Patent Publication Number: US-11653011-B2

Title: Decoded picture buffer removal

Description:
This application is a continuation of U.S. patent application Ser. No. 16/567,450, filed Sep. 11, 2019, which is a continuation of U.S. Patent Application No. continuation of U.S. patent application Ser. No. 16/112,156, filed Aug. 24, 2018, now U.S. Pat. No. 10,448,041, which is a continuation of U.S. patent application Ser. No. 14/782,910, filed on Oct. 7, 2015, now U.S. Pat. No. 10,194,160, which is a National Stage Entry of International Patent Application No. PCT/JP2014/001967, filed on Apr. 4, 2014, which is a continuation of U.S. patent application Ser. No. 13/858,076, filed on Apr. 7, 2013, now U.S. Pat. No. 9,591,321. PCT/JP2014/001967 claims priority to U.S. Provisional Application No. 61/856,575, filed on Jul. 19, 2013; to U.S. Provisional Application No. 61/845,309, filed on Jul. 11, 2013; and to U.S. Provisional Application No. 61/844,272, filed on Jul. 9, 2013. The entire contents of each of the foregoing applications are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to electronic devices. More specifically, the present disclosure relates to electronic devices for signaling sub-picture based hypothetical reference decoder parameters, and to systems and methods for hybrid operation of a decoded picture buffer (DPB). 
     BACKGROUND ART 
     Electronic devices have become smaller and more powerful in order to meet consumer needs and to improve portability and convenience. Consumers have become dependent upon electronic devices and have come to expect increased functionality. Some examples of electronic devices include desktop computers, laptop computers, cellular phones, smart phones, media players, integrated circuits, etc. 
     Some electronic devices are used for processing and displaying digital media. For example, portable electronic devices now allow for digital media to be consumed at almost any location where a consumer may be. Furthermore, some electronic devices may provide download or streaming of digital media content for the use and enjoyment of a consumer. 
     The increasing popularity of digital media has presented several problems. For example, efficiently representing high-quality digital media for storage, transmittal and rapid playback presents several challenges. As can be observed from this discussion, systems and methods that represent digital media efficiently with improved performance may be beneficial. 
     The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings. 
     SUMMARY OF INVENTION 
     Solution to Problem 
     An aspect of the invention provides a method for decoding a video bitstream comprising: (a) receiving a base bitstream representative of a coded video sequence; (b) receiving a plurality of enhancement bitstreams representative of said coded video sequence; (c) receiving a video parameter set containing syntax elements that apply to said base bitstream and said plurality of enhancement bitstreams, wherein said video parameter set contains a syntax element signaling a video parameter set extension; (d) receiving said video parameter set extension containing syntax elements related to at least one of said enhancement bitstreams; (e) receiving an output layer set change message including information indicating a change in at least one output layer set. 
     An aspect of the invention provides a method for decoding a video bitstream comprising: (a) receiving a base bitstream representative of a coded video sequence; (b) receiving a plurality of enhancement bitstreams representative of said coded video sequence; (c) receiving a video parameter set containing syntax elements that apply to said base bitstream and said plurality of enhancement bitstreams, wherein said video parameter set contains a syntax element signaling a video parameter set extension; (d) receiving said video parameter set extension containing syntax elements that includes decoded picture buffer related parameters for a decoded picture buffer for at least one of said enhancement bitstreams. 
     An aspect of the invention provides a method for video coding, comprising: beginning to parse a first slice header of a current picture; determining which steps performed by a decoded picture buffer (DPB) will be picture based and which steps will be access unit (AU) based; performing a removal from the DPB; performing a picture output from the DPB; performing a decoding and storing of a current decoded picture in the DPB; marking the current decoded picture in the DPB; and performing an additional picture output from the DPB. 
     An aspect of the invention provides an electronic device configured for video coding, comprising: a processor; memory in electronic communication with the processor, wherein instructions stored in the memory are executable to: begin to parse a first slice header of a current picture; determine which steps performed by a decoded picture buffer (DPB) will be picture based and which steps will be access unit (AU) based; perform a removal from the DPB; perform a picture output from the DPB; perform a decoding and storing of a current decoded picture in the DPB; mark the current decoded picture in the DPB; and perform an additional picture output from the DPB. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1 A  is a block diagram illustrating an example of one or more electronic devices in which systems and methods for sending a message and buffering a bitstream may be implemented. 
         FIG.  1 B  is another block diagram illustrating an example of one or more electronic devices in which systems and methods for sending a message and buffering a bitstream may be implemented. 
         FIG.  2    is a flow diagram illustrating one configuration of a method for sending a message. 
         FIG.  3    is a flow diagram illustrating one configuration of a method for determining one or more removal delays for decoding units in an access unit. 
         FIG.  4    is a flow diagram illustrating one configuration of a method for buffering a bitstream; 
         FIG.  5    is a flow diagram illustrating one configuration of a method for determining one or more removal delays for decoding units in an access unit. 
         FIG.  6 A  is a block diagram illustrating one configuration of an encoder  604  on an electronic device. 
         FIG.  6 B  is another block diagram illustrating one configuration of an encoder  604  on an electronic device. 
         FIG.  7 A  is a block diagram illustrating one configuration of a decoder on an electronic device. 
         FIG.  7 B  is another block diagram illustrating one configuration of a decoder on an electronic device. 
         FIG.  8    illustrates various components that may be utilized in a transmitting electronic device. 
         FIG.  9    is a block diagram illustrating various components that may be utilized in a receiving electronic device. 
         FIG.  10    is a block diagram illustrating one configuration of an electronic device in which systems and methods for sending a message may be implemented. 
         FIG.  11    is a block diagram illustrating one configuration of an electronic device in which systems and methods for buffering a bitstream may be implemented. 
         FIG.  12    is a block diagram illustrating one configuration of a method for operation of a decoded picture buffer. 
         FIG.  13 A  illustrates different NAL Unit header syntax. 
         FIG.  13 B  illustrates different NAL Unit header syntax. 
         FIG.  13 C  illustrates different NAL Unit header syntax. 
         FIG.  14    illustrates a general NAL Unit syntax. 
         FIG.  15    illustrates an existing video parameter set. 
         FIG.  16    illustrates existing scalability types. 
         FIG.  17    illustrates an exemplary video parameter set. 
         FIG.  18    illustrates an exemplary scalability map syntax. 
         FIG.  19    illustrates an exemplary video parameter set. 
         FIG.  20    illustrates an existing video parameter set. 
         FIG.  21    illustrates an existing dimension type, dimension id syntax. 
         FIG.  22    illustrates an exemplary video parameter set. 
         FIG.  23    illustrates an exemplary scalability map syntax. 
         FIG.  24    illustrates an exemplary video parameter set. 
         FIG.  25    illustrates an exemplary video parameter set. 
         FIG.  26    illustrates an exemplary video parameter set. 
         FIG.  27    illustrates an exemplary scalability mask syntax. 
         FIG.  28    illustrates an exemplary video parameter set extension syntax. 
         FIG.  29    illustrates an exemplary video parameter set extension syntax. 
         FIG.  30    illustrates an exemplary video parameter set extension syntax. 
         FIG.  31    illustrates an exemplary video parameter set extension syntax. 
         FIG.  32    illustrates an exemplary video parameter set extension syntax. 
         FIG.  33    illustrates an exemplary video parameter set extension syntax. 
         FIG.  34    illustrates an exemplary video parameter set syntax. 
         FIG.  35    illustrates an exemplary video parameter set extension syntax. 
         FIG.  36    illustrates an exemplary output layer sets change syntax. 
         FIG.  37    illustrates another exemplary output layer sets change syntax. 
         FIG.  38 A  illustrates an exemplary video parameter extension syntax. 
         FIG.  38 B  illustrates an exemplary video parameter extension syntax. 
         FIG.  39 A  illustrates an exemplary op_dpb_info_parameters(j) syntax. 
         FIG.  39 B  illustrates an exemplary op_dpb_info_parameters(j) syntax. 
         FIG.  40    illustrates another exemplary video parameter extension syntax. 
         FIG.  41    illustrates another exemplary oop_dpb_info_parameters(j) syntax. 
         FIG.  42    illustrates another exemplary oop_dpb_info_parameters(j) syntax. 
         FIG.  43    illustrates an exemplary num_dpb_info_parameters syntax. 
         FIG.  44    illustrates another exemplary oop_dpb_info_parameters(j) syntax. 
         FIG.  45    illustrates another exemplary num_dpb_info_parameters syntax. 
         FIG.  46    illustrates another exemplary num_dpb_info_parameters syntax. 
         FIG.  47    illustrates another exemplary video parameter extension syntax and layer_dpb_info(i). 
         FIG.  48    illustrates an exemplary oop_dpb_info_parameters and layer_dpb_info(i) syntax. 
         FIG.  49 A  illustrates another exemplary vps_extension( ). 
         FIG.  49 B  illustrates another exemplary vps_extension( ). 
         FIG.  50    illustrates an exemplary oop_dpb_maxbuffering_parameters(i). 
         FIG.  51    illustrates an exemplary layer_dpb_info_parameters(i). 
         FIG.  52    illustrates another exemplary vps_extension( ). 
         FIG.  53    illustrates another exemplary vps_extension( ). 
         FIG.  54    illustrates an exemplary oop_dpb_maxbuffering_parameters(i,k). 
         FIG.  55    illustrates an exemplary oop_dpb_maxbuffering_parameters(i,k). 
         FIG.  56    illustrates another exemplary vps_extension( ). 
         FIG.  57    illustrates an exemplary oop_dpb_maxbuffring_parameters(i,k). 
         FIG.  58    illustrates an exemplary oop_dpb_maxbuffring_parameters(i,k). 
         FIG.  59    illustrates an exemplary oop_dpb_maxbuffring_parameters(i,k). 
         FIG.  60    illustrates an exemplary oop_dpb_maxbuffring_parameters(i,k). 
         FIG.  61    illustrates an exemplary oop_dpb_maxbuffering_parameters(i,k). 
         FIG.  62    illustrates an exemplary seq_parameter_set_rbsp( ). 
         FIG.  63    is a block diagram illustrating video coding between multiple electronic devices. 
         FIG.  64    is a flow diagram of a method for hybrid decoded picture buffer (DPB) operation. 
         FIG.  65    is a flow diagram of another method for hybrid decoded picture buffer (DPB) operation. 
         FIG.  66    is a block diagram illustrating one configuration of a decoder; 
         FIG.  67 A  is a block diagram illustrating the use of both an enhancement layer and a base layer for video coding with separate decoded picture buffers (DPBs) and separate hybrid decoded picture buffer (DPB) operation modules for the base layer and the enhancement layer. 
         FIG.  67 B  is a block diagram illustrating the use of a shared decoded picture buffer (DPB) and a shared hybrid decoded picture buffer (DPB) operation module for the base layer and the enhancement layer. 
         FIG.  68    is a timing diagram illustrating hybrid decoded picture buffer (DPB) operation. 
         FIG.  69    is a block diagram illustrating structure and timing for network abstraction layer (NAL) units of layers for coded pictures and access units (AUs) when the second enhancement layer (EL 2 ) has a lower picture rate than the base layer (BL) and the first enhancement layer (EL 1 ). 
         FIG.  70    is a block diagram illustrating structure and timing for network abstraction layer (NAL) units of layers for coded pictures and access units (AUs) when the base layer (BL) has a lower picture rate than the first enhancement layer (EL 1 ) and the second enhancement layer (EL 2 ). 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Example 1 
     An electronic device for sending a message is described. The electronic device includes a processor and instructions stored in memory that is in electronic communication with the processor. The electronic device determines, when a Coded Picture Buffer (CPB) supports operation on a sub-picture level, whether to include a common decoding unit CPB removal delay parameter in a picture timing Supplemental Enhancement Information (SEI) message. The electronic device also generates, when the common decoding unit CPB removal delay parameter is to be included in the picture timing SET message (or some other SET message or some other parameter set e.g. picture parameter set or sequence parameter set or video parameter set or adaptation parameter set), the common decoding unit CPB removal delay parameter, wherein the common decoding unit CPB removal delay parameter is applicable to all decoding units in an access unit from the CPB. The electronic device also generates, when the common decoding unit CPB removal delay parameter is not to be included in the picture timing SEI message, a separate decoding unit CPB removal delay parameter for each decoding unit in the access unit. The electronic device also sends the picture timing SEI message with the common decoding unit CPB removal delay parameter or the decoding unit CPB removal delay parameters. 
     The common decoding unit CPB removal delay parameter may specify an amount of sub-picture clock ticks to wait after removal from the CPB of an immediately preceding decoding unit before removing from the CPB a current decoding unit in the access unit associated with the picture timing SEI message. 
     Furthermore, when a decoding unit is a first decoding unit in an access unit, the common decoding unit CPB removal delay parameter may specify an amount of sub-picture clock ticks to wait after removal from the CPB of a last decoding unit in an access unit associated with a most recent buffering period SEI message in a preceding access unit before removing from the CPB the first decoding unit in the access unit associated with the picture timing SEI message. 
     In contrast, when the decoding unit is a non-first decoding unit in an access unit, the common decoding unit CPB removal delay parameter may specify an amount of sub-picture clock ticks to wait after removal from the CPB of a preceding decoding unit in the access unit associated with the picture timing SEI message before removing from the CPB a current decoding unit in the access unit associated with the picture timing SEI message. 
     The decoding unit CPB removal delay parameters may specify an amount of sub-picture clock ticks to wait after removal from the CPB of the last decoding unit before removing from the CPB an i-th decoding unit in the access unit associated with the picture timing SEI message. 
     The electronic device may calculate the decoding unit CPB removal delay parameters according to a remainder of a modulo 2 (cpb_removal_delay_length_minus1+1)  counter where cpb_removal_delay_length_minus1+1 is a length of a common decoding unit CPB removal delay parameter. 
     The electronic device may also generate, when the CPB supports operation on an access unit level, a picture timing SEI message including a CPB removal delay parameter that specifies how many clock ticks to wait after removal from the CPB of an access unit associated with a most recent buffering period SEI message in a preceding access unit before removing from the CPB the access unit data associated with the picture timing SEI message. 
     The electronic device may also determine whether the CPB supports operation on a sub-picture level or an access unit level. This may include determining a picture timing flag that indicates whether a Coded Picture Buffer (CPB) provides parameters supporting operation on a sub-picture level based on a value of the picture timing flag. The picture timing flag may be included in the picture timing SEI message. 
     Determining whether to include a common decoding unit CPB removal delay parameter may include setting a common decoding unit CPB removal delay flag to 1 when the common decoding unit CPB removal delay parameter is to be included in the picture timing SEI message. It may also include setting the common decoding unit CPB removal delay flag to 0 when the common decoding unit CPB removal delay parameter is not to be included in the picture timing SEI message. The common decoding unit CPB removal delay flag may be included in the picture timing SEI message. 
     The electronic device may also generate, when the CPB supports operation on a sub-picture level, separate network abstraction layer (NAL) units related parameters that indicate an amount, offset by one, of NAL units for each decoding unit in an access unit. Alternatively, or in addition to, the electronic device may generate a common NAL parameter that indicates an amount, offset by one, of NAL units common to each decoding unit in an access unit. 
     An electronic device for buffering a bitstream is also described. The electronic device includes a processor and instructions stored in memory that is in electronic communication with the processor. The electronic device determines that a CPB signals parameters on a sub-picture level for an access unit. The electronic device also determines, when a received picture timing Supplemental Enhancement Information (SEI) message comprises the common decoding unit Coded Picture Buffer (CPB) removal delay flag, a common decoding unit CPB removal delay parameter applicable to all decoding units in the access unit. The electronic device also determines, when the picture timing SEI message does not comprise the common decoding unit CPB removal delay flag, a separate decoding unit CPB removal delay parameter for each decoding unit in the access unit. The electronic device also removes decoding units from the CPB using the common decoding unit CPB removal delay parameter or the separate decoding unit CPB removal delay parameters. The electronic device also decodes the decoding units in the access unit. 
     In one configuration, the electronic device determines that a picture timing flag is set in the picture timing SEI message. The electronic device may also set a CPB removal delay parameter, cpb_removal_delay, according to 
     
       
         
           
             
               
                 
                   
                     
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     where du_cpb_removal_delay[i] are the decoding unit CPB removal delay parameters, t c  is a clock tick, t c,sub  is a sub-picture clock tick, num_decoding_units_minus1 is an amount of decoding units in the access unit offset by one, and i is an index. 
     Alternatively, the electronic device may set a CPB removal delay parameter, cpb_removal_delay, and du_cpb_removal_delay[num_decoding_units_minus1] so as to satisfy the equation 
     
       
         
           
             
               
                 
                   
                     
                       
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     where du_cpb_removal_delay[i] are the decoding unit CPB removal delay parameters, t c  is a clock tick, t c,sub  is a sub-picture clock tick, num_decoding_units_minus1 is an amount of decoding units in the access unit offset by one, and i is an index. 
     Alternatively, the electronic device may set a CPB removal delay parameter, cpb_removal_delay, and du_cpb_removal_delay[num_decoding_units_minus1] according to cpb_removal_delay*t c =du_cpb_removal_delay[num_decoding_units_minus1]*t c_sub  where du_cpb_removal_delay[num_decoding_units_minus1] is the decoding unit CPB removal delay parameter for the num_decoding_units_minus1&#39;th decoding unit, t c  is a clock tick, t c,sub  is a sub-picture clock tick, num_decoding_units_minus1 is an amount of decoding units in the access unit offset by one. 
     In one configuration, the electronic device determines that a picture timing flag is set in the picture timing SEI message. The electronic device may also set CPB removal delay parameters, cpb_removal_delay, and du_cpb_removal_delay[num_decoding_units_minus1] so as to satisfy the equation: −1&lt;=(cpb_removal_delay*t c −du_cpb_removal_delay[num_decoding_units_minus1]*t c,sub )&lt;=1 where du_cpb_removal_delay[num_decoding_units_minus1] is the decoding unit CPB removal delay parameter for the num_decoding_units_minus1&#39;th decoding unit, t c  is a clock tick, t c,sub  is a sub-picture clock tick, num_decoding_units_minus1 is an amount of decoding units in the access unit offset by one. 
     A ClockDiff variable may be defined as ClockDiff=(num_units_in_tick−(num_units_in_sub_tick*(num_decoding_units_minus1+1))/time_scale) where num_units_in_tick is number of time units of a clock operating at the frequency time_scale Hz that corresponds to one increment of a clock tick counter, num_units_in_sub_tick is number of time units of a clock operating at the frequency time_scale Hz that corresponds to one increment of a sub-picture clock tick counter, num_decoding_units_minus1+1 is an amount of decoding units in the access unit, and time_scale is the number of time units that pass in one second. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1, the CPB is operating at sub-picture level and ClockDiff is greater than zero, the removal time for decoding unit m, t r (m) is determined according to: t r (m)=t r,n (m)+t c_sub *Ceil((t af (m)−t r,n (m))/t c_sub )+ClockDiff where t r,n (m) is the nominal removal time of the decoding unit m, t c_sub  is a sub-picture clock tick, Ceil( ) is a ceiling function and t af (m) is final arrival time of decoding unit m. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (n)&lt;t af (n), a picture timing flag is set to 1, the CPB is operating at an access unit level and ClockDiff is greater than zero, the removal time for access unit n, t r (n) is determined according to: t r (n)=t r,n (n)+t c *Ceil((t af (n)−t r,n (n))/t c )−ClockDiff where t r,n (n) is the nominal removal time of the access unit n, t c  is a clock tick, Ceil( ) is a ceiling function and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the last decoding unit m of access unit, t r (m) according to: t r (m)=t r,n (m)+max((t c_sub *Ceil((t af (m)−t r,n (m))/t c_sub )), (t c *Ceil((t af (n)−t r,n (n))/t c ))) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag is set to 1, t r,n (n)&lt;t af (n), a picture timing flag is set to 1 and the CPB is operating at access unit level, the removal time for access unit n, t r (n) according to: t r (n)=t r,n (n)+max((t c_sub *Ceil((t af (m)−t r,n (m))/t c_sub )), (t c *Ceil((t af (n)−t r,n (n))/t c ))) where t r,n (m) is the nominal removal time of the last decoding unit n, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the last decoding unit m of access unit, t r (m) according to: t r (m)=t r,n (m)+min((t c_sub *Ceil((t af (m)−t r,n (m))/t c_sub )), (t c *Ceil((t af (n)−t r,n (n))/t c ))) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag is set to 1, t r,n (n)&lt;t af (n), a picture timing flag is set to 1 and the CPB is operating at access unit level, the removal time for access unit n, t r (n) according to: t r (n)=t r,n (n)+min((t c_sub *Ceil((t af (m)−t r (m))/t c_sub )), (t c *Ceil((t af (n)−t r,n (n))/t c ))) where t r,n (m) is the nominal removal time of the last decoding unit n, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the last decoding unit m of access unit, t r (m) according to: t r (m)=t r,n (m)+(t c *Ceil((t af (n)−t r,n (n))/t c )) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag is set to 1, t r,n (n)&lt;t af (n), a picture timing flag is set to 1 and the CPB is operating at access unit level, the removal time for access unit n, t r (n) according to: t r (n)=t r,n (n)+(t c *Ceil((t af (n)−t r,n (n))/t c )) where t r,n (m) is the nominal removal time of the last decoding unit n, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for a decoding unit m which is not the last decoding unit is set as t r (m)=t af (m), where t af (m) is a final arrival time of decoding unit m. When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for a decoding unit m which is the last decoding unit m of access unit, t r (m) according to: t r (m)=(m)+(t c_sub *Ceil((t af (m)−t r,n (m))/t c_sub )) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick, t af (n) is a final arrival time of access unit n, and t af (m) is a final arrival time of last decoding unit m in the access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for a decoding unit m which is not the last decoding unit is set as t r (m)=t af (m), where t af (m) is a final arrival time of decoding unit m. When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for a decoding unit m which is the last decoding unit m of access unit, t r (m) according to: t r (m)=t r,n (m)+(t c *Ceil((t af (m)−t r,n (m))/t c )) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick, t af (n) is a final arrival time of access unit n, and t af (m) is a final arrival time of last decoding unit m in the access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for a decoding unit m is set as t r (m)=t af (m) where t r,n (m) is the nominal removal time of the decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick, t af (n) is a final arrival time of access unit n, and t af (m) is a final arrival time of decoding unit m in the access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag is set to 1, t r,n (n)&lt;t af (n), a picture timing flag is set to 1 and the CPB is operating at access unit level, the removal time for access unit n, t r (n) according to: t r (n)=t af (n) where t r,n (m) is the nominal removal time of the last decoding unit n, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     Additionally in some cases a flag may be sent in part of the bitstream to signal which of the above alternative equations are used for deciding the removal time of the decoding units and removal time of the access unit. In one case the flag may be called du_au_cpb_alignment_mode_flag. If du_au_cpb_alignment_mode_flag is 1 then the equations above which align the operation of CPB which operates in sub-picture based mode with the CPB which operates in the access unit mode are used. If du_au_cpb_alignment_mode_flag is 0 then the equations above which do not align the operation of CPB which operates in sub-picture based mode with the CPB which operates in the access unit mode are used. 
     In one case the flag du_au_cpb_alignment_mode_flag may be signaled in the video usability information (VUI). In another case the flag du_au_cpb_alignment_mode_flag may be sent in picture timing SEI message. In yet another case the flag du_au_cpb_alignment_mode_flag may be sent in some other normative part of the bitstream. One example of modified syntax and semantics in accordance with the systems and methods disclosed herein is given in Table (0) as follows. 
     
       
         
           
               
             
               
                 TABLE (0) 
               
               
                   
               
             
            
               
                 pic_timing( payloadSize ) { 
               
               
                  if( CpbDpbDelaysPresentFlag ) { 
               
               
                   cpb_removal_delay 
               
               
                   dpb_output_delay 
               
               
                   if( sub_pic_cpb_params_present_flag ) { 
               
               
                    num_decoding_units_minus1 
               
               
                    du_au_cpb_alignment_mode_flag 
               
               
                    for( i = 0; i &lt;= num_decoding_units_minus1; i++ ) { 
               
               
                     num_nalus_in_du_minus1[i] 
               
               
                     du_cpb_removal_delay[i] 
               
               
                    } 
               
               
                   } 
               
               
                  } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     It should be noted that different symbols (names) than those used above for various variables may be used. For example t r (n) of access unit n may be called CpbRemovalTime(n), t r (m) of decoding unit n may be called CpbRemovalTime(m), t c_sub  may be called ClockSubTick, t c  may be called ClockTick, t af (n) of access unit m may be called FinalArrivalTime(n) of access unit n, t af (m) of decoding unit m may be called FinalArrivalTime(m), t r,n (n) may be called NominalRemovalTime(n) of the access unit n, t r,n (m) may be called NominalRemovalTime(m) of the decoding unit m. 
     A method for sending a message by an electronic device is also described. The method includes determining, when a Coded Picture Buffer (CPB) supports operation on a sub-picture level, whether to include a common decoding unit CPB removal delay parameter in a picture timing Supplemental Enhancement Information (SEI) message. The method also includes generating, when the common decoding unit CPB removal delay parameter is to be included in the picture timing SEI message, the common decoding unit CPB removal delay parameter, wherein the common decoding unit CPB removal delay parameter is applicable to all decoding units in an access unit from the CPB. The method also includes generating, when the common decoding unit CPB removal delay parameter is not to be included in the picture timing SEI message, a separate decoding unit CPB removal delay parameter for each decoding unit in the access unit. The method also includes sending the picture timing SEI message with the common decoding unit CPB removal delay parameter or the decoding unit CPB removal delay parameters. 
     A method for buffering a bitstream by an electronic device is also described. The method includes determining that a CPB signals parameters on a sub-picture level for an access unit. The method also includes determining, when a received picture timing Supplemental Enhancement Information (SEI) message comprises the common decoding unit Coded Picture Buffer (CPB) removal delay flag, a common decoding unit CPB removal delay parameter applicable to all decoding units in the access unit. The method also includes determining, when the picture timing SEI message does not comprise the common decoding unit CPB removal delay flag, a separate decoding unit CPB removal delay parameter for each decoding unit in the access unit. The method also includes removing decoding units from the CPB using the common decoding unit CPB removal delay parameter or the separate decoding unit CPB removal delay parameters. The method also includes decoding the decoding units in the access unit. 
     The systems and methods disclosed herein describe electronic devices for sending a message and buffering a bitstream. For example, the systems and methods disclosed herein describe buffering for bitstreams starting with sub-picture parameters. In some configurations, the systems and methods disclosed herein may describe signaling sub-picture based Hypothetical Reference Decoder (HRD) parameters. For instance, the systems and methods disclosed herein describe modification to a picture timing Supplemental Enhancement Information (SEI) message. The systems and methods disclosed herein (e.g., the HRD modification) may result in more compact signaling of parameters when each sub-picture arrives and is removed from CPB at regular intervals. 
     Furthermore, when the sub-picture level CPB removal delay parameters are present, the Coded Picture Buffer (CPB) may operate at access unit level or sub-picture level. The present systems and methods may also impose a bitstream constraint so that the sub-picture level based CPB operation and the access unit level CPB operation result in the same timing of decoding unit removal. Specifically the timing of removal of last decoding unit in an access unit when operating in sub-picture mode and the timing of removal of access unit when operating in access unit mode will be the same. 
     It should be noted that although the term “hypothetical” is used in reference to an HRD, the HRD may be physically implemented. For example, “HRD” may be used to describe an implementation of an actual decoder. In some configurations, an HRD may be implemented in order to determine whether a bitstream conforms to High Efficiency Video Coding (HEVC) specifications. For instance, an HRD may be used to determine whether Type I bitstreams and Type II bitstreams conform to HEVC specifications. A Type I bitstream may contain only Video Coding Layer (VCL) Network Access Layer (NAL) units and filler data NAL units. A Type II bitstream may contain additional other NAL units and syntax elements. 
     Joint Collaborative Team on Video Coding (JCTVC) document JCTVC-I0333 includes sub-picture based HRD and supports picture timing SEI messages. This functionality has been incorporated into the High Efficiency Video Coding (HEVC) Committee Draft (JCTVC-I1003), incorporated by reference herein in its entirety. B. Bros, W-J. Han, J-R. Ohm, G. J. Sullivan, Wang, and T-. Wiegand, “High efficiency video coding (HEVC) text specification draft 10 (for DFIS &amp; Last Call)”, JCTVCJ10003_v34, Geneva, January 2013 is hereby incorporated by reference herein in its entirety. B. Bros, W-J. Han, J-R. Ohm, G. J. Sullivan, Wang, and T-. Wiegand, “High efficiency video coding (HEVC) text specification draft 10”, JCTVC-L1003, Geneva, January 2013 is hereby incorporated by reference herein in its entirety. 
     One example of modified syntax and semantics in accordance with the systems and methods disclosed herein is given in Table (1) as follows. 
     
       
         
           
               
             
               
                 TABLE (1) 
               
               
                   
               
             
            
               
                 pic_timing( payloadSize ) { 
               
               
                  if( CpbDpbDelaysPresentFlag ) { 
               
               
                   cpb_removal_delay 
               
               
                   dpb_output_delay 
               
               
                   if( sub_pic_cpb_params_present_flag ) { 
               
               
                    num_decoding_units_minus1 
               
               
                    common_du_cpb_removal_delay_flag 
               
               
                   if(common_du_cpb_removal_delay_flag) { 
               
               
                    common_du_cpb_removal_delay 
               
               
                   } 
               
               
                    for( i = 0; i &lt;= num_decoding_units_minus1; 1++ ) { 
               
               
                     num_nalus_in_du_minus1[i] 
               
               
                    if(!common_du_cpb_removal_delay_flag) 
               
               
                     du_cpb_removal_delay[i] 
               
               
                    } 
               
               
                   } 
               
               
                  } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     Examples regarding buffering period SEI message semantics in accordance with the systems and methods disclosed herein are given as follows. In particular, additional detail regarding the semantics of the modified syntax elements are given as follows. When NalHrdBpPresentFlag or VclHrdBpPresentFlag are equal to 1, a buffering period SEI message can be associated with any access unit in the bitstream, and a buffering period SEI message may be associated with each IDR access unit, with each CRA access unit, and with each access unit associated with a recovery point SEI message. For some applications, the frequent presence of a buffering period SEI message may be desirable. A buffering period is specified as the set of access units between two instances of the buffering period SEI message in decoding order. 
     ‘seq_parameter_set_id’ specifies the sequence parameter set that contains the sequence HRD attributes. The value of seq_parameter_set_id may be equal to the value of seq_parameter_set_id in the picture parameter set referenced by the primary coded picture associated with the buffering period SEI message. The value of seq_parameter_set_id may be in the range of 0 to 31, inclusive. 
     ‘initial_cpb_removal_delay’[SchedSelIdx] specifies the delay for the SchedSelIdx-th CPB between the time of arrival in the CPB of the first bit of the coded data associated with the access unit associated with the buffering period SEI message and the time of removal from the CPB of the coded data associated with the same access unit, for the first buffering period after HRD initialization. The syntax element has a length in bits given by initial_cpb_removal_delay_length_minus1+1. It is in units of a 90 kHz clock. initial_cpb_removal_delay[SchedSelIdx] may not be equal to 0 and may not exceed 90000*(CpbSize[SchedSelIdx]/BitRate[SchedSelIdx]), the time-equivalent of the CPB size in 90 kHz clock units. 
     ‘initial_cpb_removal_delay_offset’[SchedSelIdx] is used for the SchedSelIdx-th CPB in combination with the cpb_removal_delay to specify the initial delivery time of coded access units to the CPB. initial_cpb_removal_delay_offset[SchedSelIdx] is in units of a 90 kHz clock. The initial_cpb_removal_delay_offset[SchedSelIdx] syntax element is a fixed length code whose length in bits is given by initial_cpb_removal_delay_length_minus1+1. This syntax element is not used by decoders and is needed only for the delivery scheduler (HSS) (e.g., as specified in Annex C of JCTVC-I1003). 
     Over the entire coded video sequence, the sum of initial_cpb_removal_delay[SchedSelIdx] and initial_cpb_removal_delay_offset[SchedSelIdx] may be constant for each value of SchedSelIdx. 
     ‘initial_du_cpb_removal_delay’[SchedSelIdx] specifies the delay for the SchedSelIdx-th CPB between the time of arrival in the CPB of the first bit of the coded data associated with the first decoding unit in the access unit associated with the buffering period SEI message and the time of removal from the CPB of the coded data associated with the same decoding unit, for the first buffering period after HRD initialisation. The syntax element has a length in bits given by initialcpb_removal_delay_length_minus1+1. It is in units of a 90 kHz clock. initial_du_cpb_removal_delay[SchedSelIdx] may not be equal to 0 and may not exceed 90000*(CpbSize[SchedSelIdx]/BitRate[SchedSelIdx]), the time-equivalent of the CPB size in 90 kHz clock units. 
     ‘initial_du_cpb_removal_delay_offset’[SchedSelIdx] is used for the SchedSelIdx-th CPB in combination with the cpb_removal_delay to specify the initial delivery time of decoding units to the CPB. 
     initial_cpb_removal_delay_offset[SchedSelIdx] is in units of a 90 kHz clock. The initial_du_cpb_removal_delay_offset[SchedSelIdx] syntax element is a fixed length code whose length in bits is given by initial_cpb_removal_delay_length_minus1+1. This syntax element is not used by decoders and is needed only for the delivery scheduler (HSS) (e.g., as specified in Annex C of JCTVC-I1003). 
     Over the entire coded video sequence, the sum of initial_du_cpb_removal_delay[SchedSelIdx] and initial_du_cpb_removal_delay_offset[SchedSelIdx] may be constant for each value of SchedSelIdx. 
     Examples regarding picture timing SEI message semantics in accordance with the systems and methods disclosed herein are given as follows. In particular, additional detail regarding the semantics of the modified syntax elements are given as follows. 
     The syntax of the picture timing SEI message is dependent on the content of the sequence parameter set that is active for the coded picture associated with the picture timing SEI message. However, unless the picture timing SEI message of an Instantaneous Decoding Refresh (IDR) access unit is preceded by a buffering period SEI message within the same access unit, the activation of the associated sequence parameter set (and, for IDR pictures that are not the first picture in the bitstream, the determination that the coded picture is an IDR picture) does not occur until the decoding of the first coded slice Network Abstraction Layer (NAL) unit of the coded picture. Since the coded slice NAL unit of the coded picture follows the picture timing SEI message in NAL unit order, there may be cases in which it is necessary for a decoder to store the raw byte sequence payload (RBSP) containing the picture timing SEI message until determining the parameters of the sequence parameter that will be active for the coded picture, and then perform the parsing of the picture timing SEI message. 
     The presence of picture timing SEI message in the bitstream is specified as follows. If CpbDpbDelaysPresentFlag is equal to 1, one picture timing SEI message may be present in every access unit of the coded video sequence. Otherwise (CpbDpbDelaysPresentFlag is equal to 0), no picture timing SEI messages may be present in any access unit of the coded video sequence. 
     ‘cpb_removal_delay’ specifies how many clock ticks (see subclause E.2.1 of JCTVC-I1003) to wait after removal from the CPB of the access unit associated with the most recent buffering period SEI message in a preceding access unit before removing from the buffer the access unit data associated with the picture timing SEI message. This value is also used to calculate an earliest possible time of arrival of access unit data into the CPB for the HSS, as specified in Annex C of JCTVC-I1003. The syntax element is a fixed length code whose length in bits is given by cpb_removal_delay_length_minus1+1. The cpb_removal_delay is the remainder of a modulo 2 (cpb_removal_delay_length_minus1+1)  counter. 
     The value of cpb_removal_delay_length_minus1 that determines the length (in bits) of the syntax element cpb_removal_delay is the value of cpb_removal_delay_length_minus1 coded in the sequence parameter set that is active for the primary coded picture associated with the picture timing SEI message, although cpb_removal_delay specifies a number of clock ticks relative to the removal time of the preceding access unit containing a buffering period SEI message, which may be an access unit of a different coded video sequence. 
     ‘dpb_output_delay’ is used to compute the Decoded Picture Buffer (DPB) output time of the picture. It specifies how many clock ticks to wait after removal of the last decoding unit in an access unit from the CPB before the decoded picture is output from the DPB (see subclause C.2 of JCTVC-I1003). 
     With respect to the DPB, a picture is not removed from the DPB at its output time when it is still marked as “used for short-term reference” or “used for long-term reference”. Only one dpb_output_delay is specified for a decoded picture. The length of the syntax element dpb_output_delay is given in bits by dpb_output_delay_length_minus1+1. When max_dec_pic_buffering[max_temporal_layers_minus1] is equal to 0, dpb_output_delay may be equal to 0. 
     The output time derived from the dpb_output_delay of any picture that is output from an output timing conforming decoder as specified in subclause C.2 of JCTVC-I1003 may precede the output time derived from the dpb_output_delay of all pictures in any subsequent coded video sequence in decoding order. The picture output order established by the values of this syntax element may be the same order as established by the values of PicOrderCnt( ) as specified by subclause. For pictures that are not output by the “bumping” process of subclause because they precede, in decoding order, an IDR picture with no_output_of_prior_pics_flag equal to 1 or inferred to be equal to 1, the output times derived from dpb_output_delay may be increasing with increasing value of PicOrderCnt( ) relative to all pictures within the same coded video sequence. 
     ‘num_decoding_units_minus1’ plus 1 specifies the number of decoding units in the access unit the picture timing SEI message is associated with. The value of num_decoding_units_minus1 may be in the range of 0 to PicWidthInCtbs*PicHeightInCtbs−1, inclusive. 
     ‘common_du_cpb_removal_delay_flag’ equal to 1 specifies that the syntax element common_du_cpb_removal_delay is present. 
     ‘common_du_cpb_removal_delay_flag’ equal to 0 specifies that the syntax element common_du_cpb_removal_delay is not present. 
     ‘common_du_cpb_removal_delay’ specifies information as follows: If a decoding unit is the first decoding unit in the access unit associated with the picture timing SEI message then common_du_cpb_removal_delay specifies how many sub-picture clock ticks (see subclause E.2.1 of JCTVC-I1003) to wait after removal from the CPB of the last decoding unit in the access unit associated with the most recent buffering period SEI message in a preceding access unit before removing from the CPB the first decoding unit in the access unit associated with the picture timing SEI message. 
     Otherwise common_du_cpb_removal_delay specifies how many sub-picture clock ticks (see subclause E.2.1 of JCTVC-I1003) to wait after removal from the CPB of the preceding decoding unit in the access unit associated with the picture timing SEI message before removing from the CPB the current decoding unit in the access unit associated with the picture timing SEI message. This value is also used to calculate an earliest possible time of arrival of decoding unit data into the CPB for the HSS, as specified in Annex C. The syntax element is a fixed length code whose length in bits is given by cpb_removal_delay_length_minus1+1. The common_du_cpb_removal_delay is the remainder of a modulo 2 (cpb_removal_delay_length_minus1+1)  counter. 
     An alternate way of specifying ‘common_du_cpb_removal_delay’ is as follows. 
     common_du_cpb_removal_delay specifies how many sub-picture clock ticks (see subclause E.2.1 of JCTVC-I1003) to wait after removal from the CPB of the last decoding unit before removing from the CPB the current decoding unit in the access unit associated with the picture timing SEI message. This value is also used to calculate an earliest possible time of arrival of decoding unit data into the CPB for the HSS, as specified in Annex C. The syntax element is a fixed length code whose length in bits is given by cpb_removal_delay_length_minus1+1. The common_du_cpb_removal_delay is the remainder of a modulo 2 (cpb_removal_delay_length_minus1+1)  counter. 
     The value of cpb_removal_delay_length_minus1 that determines the length (in bits) of the syntax element common_du_cpb_removal_delay is the value of cpb_removal_delay_length_minus1 coded in the sequence parameter set that is active for the coded picture associated with the picture timing SEI message, although common_du_cpb_removal_delay specifies a number of sub-picture clock ticks relative to the removal time of the first decoding unit in the preceding access unit containing a buffering period SEI message, which may be an access unit of a different coded video sequence. 
     ‘num_nalus_in_du_minus1[i]’ plus 1 specifies the number of NAL units in the i-th decoding unit of the access unit the picture timing SEI message is associated with. The value of num_nalus_in_du_minus1[i] may be in the range of 0 to PicWidthInCtbs*PicHeightInCtbs−1, inclusive. 
     The first decoding unit of the access unit consists of the first num_nalus_in_du_minus1[0]+1 consecutive NAL units in decoding order in the access unit. The i-th (with i greater than 0) decoding unit of the access unit consists of the num_nalus_in_du_minus1[i]+1 consecutive NAL units immediately following the last NAL unit in the previous decoding unit of the access unit, in decoding order. There may be at least one VCL NAL unit in each decoding unit. All non-VCL NAL units associated with a VCL NAL unit may be included in the same decoding unit. 
     ‘du_cpb_removal_delay[i]’ specifies how many sub-picture clock ticks (see subclause E.2.1 of JCTVC-I1003) to wait after removal from the CPB of the first decoding unit in the access unit associated with the most recent buffering period SEI message in a preceding access unit before removing from the CPB the i-th decoding unit in the access unit associated with the picture timing SEI message. This value is also used to calculate an earliest possible time of arrival of decoding unit data into the CPB for the HSS (e.g., as specified in Annex C of JCTVC-I1003). The syntax element is a fixed length code whose length in bits is given by cpb_removal_delay_length_minus1+1. The du_cpb_removal_delay[i] is the remainder of a modulo 2 (cpb_removal_delay_length_minus1+1)  Counter. 
     The value of cpb_removal_delay_length_minus1 that determines the length (in bits) of the syntax element du_cpb_removal_delay[i] is the value of cpb_removal_delay_length_minus1 coded in the sequence parameter set that is active for the coded picture associated with the picture timing SEI message, although du_cpb_removal_delay[i] specifies a number of sub-picture clock ticks relative to the removal time of the first decoding unit in the preceding access unit containing a buffering period SEI message, which may be an access unit of a different coded video sequence. 
     In one configuration, the timing of decoding unit removal and decoding of decoding units may be implemented as follows. 
     If SubPicCpbFlag is equal to 0, the variable CpbRemovalDelay(m) is set to the value of cpb_removal_delay in the picture timing SEI message associated with the access unit that is decoding unit m, and the variable T c  is set to t c . Otherwise if SubPicCpbFlag is equal to 1 and common_du_cpb_removal_delay_flag is 0 the variable CpbRemovalDelay(m) is set to the value of du_cpb_removal_delay[i] for decoding unit m (with m ranging from 0 to num_decoding_units_minus1) in the picture timing SEI message associated with the access unit that contains decoding unit m, and the variable T c  is set to t c_sub . 
     In some cases, Otherwise if SubPicCpbFlag is equal to 1 and common_du_cpb_removal_delay_flag is 0 the variable CpbRemovalDelay(m) is set to the value of (m+1)*du_cpb_removal_delay[i] for decoding unit m (with m ranging from 0 to num_decoding_units_minus1) in the picture timing SEI message associated with the access unit that contains decoding unit m, and the variable T c  is set to t c_sub . 
     Otherwise if SubPicCpbFlag is equal to 1 and common_du_cpb_removal_delay_flag is 1 the variable CpbRemovalDelay(m) is set to the value of common_du_cpb_removal_delay for decoding unit m in the picture timing SEI message associated with the access unit that contains decoding unit m, and the variable T c  is set to t c_sub . 
     When a decoding unit m is the decoding unit with n equal to 0 (the first decoding unit of the access unit that initializes the HRD), the nominal removal time of the decoding unit from the CPB is specified by t r,n (0)=InitCpbRemovalDelay[SchedSelIdx]/90000. 
     When a decoding unit m is the first decoding unit of the first access unit of a buffering period that does not initialize the HRD, the nominal removal time of the decoding unit from the CPB is specified by t r,n (m)=t r,n (m b )+T c *CpbRemovalDelay(m), where t r,n (m b ) is the nominal removal time of the first decoding unit of the previous buffering period. 
     When a decoding unit m is the first decoding unit of a buffering period, m b  is set equal to m at the removal time t r,n (m) of the decoding unit m. The nominal removal time t r,n (m) of a decoding unit m that is not the first decoding unit of a buffering period is given by t r,n (m)=t r,n (m b )+T c *CpbRemovalDelay(m), where t r,n (m b ) is the nominal removal time of the first decoding unit of the current buffering period. 
     The removal time of decoding unit m is specified as follows. If low_delay_hrd_flag is equal to 0 or t r,n (m)&gt;=t af (m), the removal time of decoding unit m is specified by t r (m)=t r,n (m). Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)), the removal time of decoding unit m is specified by t r (m)=t r,n (m)+T c *Ceil((t af (m)−t r,n (m))/T c ). The latter case (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)) indicates that the size of decoding unit m, b(m), is so large that it prevents removal at the nominal removal time. 
     In another case the removal time of decoding unit m is specified as follows. If low_delay_hrd_flag is equal to 0 or t r,n (m)&gt;=t af (m), the removal time of decoding unit m is specified by t r (m)=t r,n (m). Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)), the removal time of decoding unit m which is not the last decoding unit in the access unit is specified by t r (m)=t af (m), and the removal time of decoding unit m which is the last decoding unit in the access unit t r (m)=t r,n (m)+T c *Ceil((t af (m)−t r,n (m))/t c ). The latter case (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)) indicates that the size of decoding unit m, b(m), is so large that it prevents removal at the nominal removal time. 
     In another case the removal time of decoding unit m is specified as follows. If low_delay_hrd_flag is equal to 0 or t r,n (m)&gt;=t af (m), the removal time of decoding unit m is specified by t r (m)=t r,n (m). Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)), the removal time of decoding unit m which is not the last decoding unit in the access unit is specified by t r (m)=t af (m), and the removal time of decoding unit m which is the last decoding unit in the access unit t r (m)=t r,n (m)+t c *Ceil((t af (m)−t r,n (m))/t c ). The latter case (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)) indicates that the size of decoding unit m, b(m), is so large that it prevents removal at the nominal removal time. 
     In another case the removal time of decoding unit m is specified as follows. If low_delay_hrd_flag is equal to 0 or t r,n (m)&gt;=t af (m), the removal time of decoding unit m is specified by t r (m)=t r,n (m). Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)), the removal time of decoding unit m is specified by t r (m)=t af (m). The latter case (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)) indicates that the size of decoding unit m, b(m), is so large that it prevents removal at the nominal removal time. 
     When SubPicCpbFlag is equal to 1, the nominal CPB removal time of access unit n t r,n (n) is set to the nominal CPB removal time of the last decoding unit in access unit n, the CPB removal time of access unit n t r (n) is set to the CPB removal time of the last decoding unit in access unit n. 
     When SubPicCpbFlag is equal to 0, each decoding unit is an access unit, hence the nominal CPB removal time and the CPB removal time of access unit n are the nominal CPB removal time and the CPB removal time of decoding unit n. 
     At CPB removal time of decoding unit m, the decoding unit is instantaneously decoded. 
     Another example of modified syntax and semantics for a picture timing SEI message in accordance with the systems and methods disclosed herein is given in Table (2) as follows. Modifications in accordance with the systems and methods disclosed herein are denoted in bold. 
     
       
         
           
               
             
               
                 TABLE (2) 
               
               
                   
               
             
            
               
                 pic_timing( payloadSize ) { 
               
               
                  if( CpbDpbDelaysPresentFlag ) { 
               
               
                   cpb_removal_delay 
               
               
                   dpb_output_delay 
               
               
                   if( sub_pic_cpb_params_present_flag ) { 
               
               
                    num_decoding_units_minus1 
               
               
                    common_du_cpb_removal_delay_flag 
               
               
                    if(common_du_cpb_removal_delay_flag) { 
               
               
                    common_num_nalus_in_du_minus1 
               
               
                    common_du_cpb_removal_delay 
               
               
                    } 
               
               
                    for( i = 0; i &lt;= num_decoding_units_minus1; 1++ ) { 
               
               
                     num_nalus_in_du_minus1[i] 
               
               
                     if(!common_du_cpb_removal_delay_flag) 
               
               
                      du_cpb_removal_delay[i] 
               
               
                    } 
               
               
                   } 
               
               
                  } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     The illustrated example in Table (2) includes a syntax element common_num_nalus_in_du_minus1, which may be used to determine how much data should be removed from the CPB when removing a decoding unit. ‘common_num_nalus_in_du_minus1’ plus 1 specifies the number of NAL units in each decoding unit of the access unit the picture timing SEI message is associated with. The value of common_num_nalus_in_du_minus1 may be in the range of 0 to PicWidthInCtbs*PicHeightInCtbs−1, inclusive. 
     The first decoding unit of the access unit consists of the first common_num_nalus_in_du_minus1+1 consecutive NAL units in decoding order in the access unit. The i-th (with i greater than 0) decoding unit of the access unit consists of the common_num_nalus_in_du_minus1+1 consecutive NAL units immediately following the last NAL unit in the previous decoding unit of the access unit, in decoding order. There may be at least one VCL NAL unit in each decoding unit. All non-VCL NAL units associated with a VCL NAL unit may be included in the same decoding unit. 
     Another example of modified syntax and semantics for a picture timing SEI message in accordance with the systems and methods disclosed herein is given in Table (3) as follows. Modifications in accordance with the systems and methods disclosed herein are denoted in bold. 
     
       
         
           
               
             
               
                 TABLE (3) 
               
               
                   
               
             
            
               
                 pic_timing( payloadSize ) { 
               
               
                  if CpbDpbDelaysPresentFlag ) { 
               
               
                   cpb_removal_delay 
               
               
                   dpb_output_delay 
               
               
                   if( sub_pic_cpb_params_present_flag ) { 
               
               
                    num_decoding_units_minus1 
               
               
                    common_num_nalus_in_du_flag 
               
               
                    if(common_num_nalus_in_du_flag) { 
               
               
                     common_num_nalus_in_du_minus1 
               
               
                    } 
               
               
                     common_du_cpb_removal_delay_flag 
               
               
                    if(common_du_cpb_removal_delay_flag) { 
               
               
                     common_du_cpb_removal_delay 
               
               
                    } 
               
               
                    for( i = 0; i &lt;= num_decoding_units_minus1; i++ ) { 
               
               
                     if(!common_num_nalus_in_du flag) 
               
               
                      num_nalus_in_du_minus1[i] 
               
               
                     if(!common_du_cpb_removal_delay_flag) 
               
               
                     du_cpb_removal_delay[i] 
               
               
                    } 
               
               
                   } 
               
               
                  } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     The illustrated example in Table (3) includes a syntax element ‘common_num_nalus_in_du_flag’ that, when equal to 1, specifies that the syntax element ‘common_num_nalus_in_du_minus1’ is present. ‘common_num_nalus_in_du_flag’ equal to 0 specifies that the syntax element ‘common_num_nalus_in_du_minus1’ is not present. 
     In yet another embodiment flags common_du_cpb_removal_delay_flag common_num_nalus_in_du_minus1, may not be sent. Instead syntax elements common_num_nalus_in_du_minus1 and common_du_cpb_removal_delay could be sent every time. In this case a value of 0 (or some other) for these syntax elements could be used to indicate that these elements are not signaled. 
     In addition to modifications to the syntax elements and semantics of the picture timing SEI message, the present systems and methods may also implement a bitstream constraint so that sub-picture based CPB operation and access unit level CPB operation result in the same timing of decoding unit removal. 
     When sub_pic_cpb_params_present_flag equals to 1 that sub-picture level CPB removal delay parameters are present the CPB may operate at access unit level or sub-picture level. sub_pic_cpb_params_present_flag equal to 0 specifies that sub-picture level CPB removal delay parameters are not present and the CPB operates at access unit level. When sub_pic_cpb_params_present_flag is not present, its value is inferred to be equal to 0. 
     To support the operation at both access unit level or sub-picture level, the following bitstream constraints may be used: If sub_pic_cpb_params_present_flag is 1 then it is requirement of bitstream conformance that the following constraint is obeyed when signaling the values for cpb_removal_delay and du_cpb_removal_delay[i] for all i: 
     
       
         
           
             
               
                 
                   
                     
                       cpb 
                       ⁢ 
                       _ 
                       ⁢ 
                       removal 
                     
                     ⁢ 
                     
                       _ 
                       ⁢ 
                       delay 
                     
                   
                   = 
                   
                     
                       
                         
                           
                             
                               ( 
                               
                                 
                                   ∑ 
                                   
                                     i 
                                     = 
                                     0 
                                   
                                   
                                     num_decoding 
                                     ⁢ 
                                     _units 
                                     ⁢ 
                                     _minus 
                                     ⁢ 
                                     
                                         
                                     
                                     ⁢ 
                                     1 
                                   
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 
                                   
                                     du 
                                     ⁢ 
                                     _ 
                                     ⁢ 
                                     cpb 
                                   
                                   ⁢ 
                                   
                                     _ 
                                     ⁢ 
                                     removal 
                                   
                                   ⁢ 
                                   
                                     
                                       _ 
                                       ⁢ 
                                       delay 
                                     
                                     ⁡ 
                                     
                                       [ 
                                       i 
                                       ] 
                                     
                                   
                                 
                               
                               ) 
                             
                             * 
                           
                         
                       
                       
                         
                           
                             t 
                             
                               c 
                               , 
                               sub 
                             
                           
                         
                       
                     
                     
                       t 
                       c 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Math 
                     . 
                     
                         
                     
                     ⁢ 
                     3 
                   
                   ] 
                 
               
             
           
         
       
     
     where du_cpb_removal_delay[i] are the decoding unit CPB removal delay parameters, t c  is a clock tick, t c,sub  is sub-picture clock tick, num_decoding_units_minus1 is an amount of decoding units in the access unit offset by one, and i is an index. In some embodiments a tolerance parameter could be added to satisfy the above constraint. 
     To support the operation at both access unit level or sub-picture level, the bitstream constraints as follows may be used: Let the variable T du (k) be defined as: 
     
       
         
           
             
               
                 
                   
                     
                       T 
                       du 
                     
                     ( 
                     
                         
                     
                     ⁢ 
                     k 
                     ) 
                   
                   = 
                   
                       
                   
                   ⁢ 
                   
                     
                       
                         T 
                         du 
                       
                       ⁡ 
                       
                         ( 
                         
                           k 
                           - 
                           1 
                         
                         ) 
                       
                     
                     + 
                     
                         
                     
                     ⁢ 
                     
                       
                         t 
                         
                           c 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           _ 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           sub 
                         
                       
                       * 
                       
                           
                         
                             
                         
                         ⁢ 
                         
                             
                           
                               
                             
                                 
                               
                                 
                                   ∑ 
                                   
                                     i 
                                     = 
                                     0 
                                   
                                   
                                     num_decoding 
                                     ⁢ 
                                     _units 
                                     ⁢ 
                                     _minus 
                                     ⁢ 
                                     
                                         
                                     
                                     ⁢ 
                                     
                                       1 
                                       k 
                                     
                                   
                                 
                                 ⁢ 
                                 
                                     
                                   
                                       
                                     
                                         
                                       
                                         ( 
                                         
                                           
                                             du 
                                             ⁢ 
                                             
                                                 
                                             
                                             ⁢ 
                                             _ 
                                             ⁢ 
                                             
                                                 
                                             
                                             ⁢ 
                                             cpb 
                                             ⁢ 
                                             
                                                 
                                             
                                             ⁢ 
                                             _ 
                                             ⁢ 
                                             
                                                 
                                             
                                             ⁢ 
                                             removal 
                                             ⁢ 
                                             
                                                 
                                             
                                             ⁢ 
                                             _ 
                                             ⁢ 
                                             
                                                 
                                             
                                             ⁢ 
                                             delay 
                                             ⁢ 
                                             
                                                 
                                             
                                             ⁢ 
                                             _ 
                                             ⁢ 
                                             
                                                 
                                             
                                             ⁢ 
                                             minus 
                                             ⁢ 
                                             
                                                 
                                             
                                             ⁢ 
                                             
                                               
                                                 1 
                                                 k 
                                               
                                               ⁡ 
                                               
                                                 [ 
                                                 i 
                                                 ] 
                                               
                                             
                                           
                                           + 
                                           1 
                                         
                                         ) 
                                       
                                     
                                   
                                 
                               
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Math 
                     . 
                     
                         
                     
                     ⁢ 
                     4 
                   
                   ] 
                 
               
             
           
         
       
     
     where du_cpb_removal_delay_minus1 k [i] and num_decoding_units_minus1 k  are parameters for I&#39;th decoding unit of k&#39;th access unit (with k=0 for the access unit that initialized the HRD and T du (k)=0 for k&lt;1), and where du_cpb_removal_delay_minus1 k [i]+1=du_cpb_removal_delay_minus1 k [i] is the decoding unit CPB removal delay parameter for the I&#39;th decoding unit of the k&#39;th access unit, and num_decoding_units_minus1 k  is the number of decoding units in the k&#39;th access unit, t c  is a clock tick, t c,sub  is a sub-picture clock tick, and i and k are an indices. Then when the picture timing flag (e.g., sub_pic_cpb_params_present_flag) is set to 1, the following constraint shall be true: (au_cpb_removal_delay_minus1+1)*t c ==T du  (k), where (au_cpb_removal_delay_minus1+1)=cpb_removal_delay, the CPB removal delay. Thus in this case the CPB removal delay (au_cpb_removal_delay_minus1+1) is set such that the operation of sub-picture based CPB operation and access unit based CPB operation result in the same timing of access unit removal and last decoding unit of the access unit removal. 
     To support the operation at both access unit level or sub-picture level, the following bitstream constraints may be used: If sub_pic_cpb_params_present_flag is 1 then it is requirement of bitstream conformance that the following constraint is obeyed when signaling the values for cpb_removal_delay and du_cpb_removal_delay[i] for all i: 
     
       
         
           
             
               
                 
                   
                     
                       
                         - 
                         1 
                       
                       ≤ 
                       
                         [ 
                         
                           
                             
                               cpb 
                               ⁢ 
                               _ 
                               ⁢ 
                               removal 
                             
                             ⁢ 
                             
                               _ 
                               ⁢ 
                               delay 
                             
                             * 
                             
                               t 
                               c 
                             
                           
                           - 
                           
                             
                               ( 
                               
                                 
                                   ∑ 
                                   
                                     i 
                                     = 
                                     0 
                                   
                                   
                                     num_decoding 
                                     ⁢ 
                                     _units 
                                     ⁢ 
                                     _minus 
                                     ⁢ 
                                     
                                         
                                     
                                     ⁢ 
                                     1 
                                   
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 
                                   
                                     du 
                                     ⁢ 
                                     _ 
                                     ⁢ 
                                     cpb 
                                   
                                   ⁢ 
                                   
                                     _ 
                                     ⁢ 
                                     removal 
                                   
                                   ⁢ 
                                   
                                     
                                       _ 
                                       ⁢ 
                                       delay 
                                     
                                     ⁡ 
                                     
                                       [ 
                                       i 
                                       ] 
                                     
                                   
                                 
                               
                               ) 
                             
                             * 
                             
                               t 
                               
                                 c 
                                 , 
                                 sub 
                               
                             
                           
                         
                         ) 
                       
                     
                     ] 
                   
                   ≤ 
                   1 
                 
               
               
                 
                   [ 
                   
                     Math 
                     . 
                     
                         
                     
                     ⁢ 
                     5 
                   
                   ] 
                 
               
             
           
         
       
     
     where du_cpb_removal_delay[i] are the decoding unit CPB removal delay parameters, t c  is a clock tick, t c,sub  is sub-picture clock tick, num_decoding_units_minus1 is an amount of decoding units in the access unit offset by one, and i is an index. 
     To support the operation at both access unit level or sub-picture level, the following bitstream constraints may be used: If sub_pic_cpb_params_present_flag is 1 then it is requirement of bitstream conformance that the following constraint is obeyed when signaling the values for cpb_removal_delay and du_cpb_removal_delay[num_decoding_units_minus1]: cpb_removal_delay*t c =du_cpb_removal_delay[num_decoding_units_minus1]*t c,sub  where du_cpb_removal_delay[num_decoding_units_minus1] is the decoding unit CPB removal delay parameter for the num_decoding_units_minus1&#39;th decoding unit, t c  is a clock tick, t c,sub  is a sub-picture clock tick, num_decoding_units_minus1 is an amount of decoding units in the access unit offset by one. In some embodiments a tolerance parameter could be added to satisfy the above constraint. 
     To support the operation at both access unit level or sub-picture level, the following bitstream constraints may be used: If sub_pic_cpb_params_present_flag is 1 then it is requirement of bitstream conformance that the following constraint is obeyed when signaling the values for cpb_removal_delay and du_cpb_removal_delay[i] for all i: −1&lt;=(cpb_removal_delay*t c −du_cpb_removal_delay [num_decoding_units_minus1]*t c,sub )&lt;=1 where du_cpb_removal_delay[num_decoding_units_minus1] is the decoding unit CPB removal delay parameter for the num_decoding_units_minus1&#39;th decoding unit, t c  is a clock tick, t c,sub  is a sub-picture clock tick, num_decoding_units_minus1 is an amount of decoding units in the access unit offset by one. 
     Additionally, the present systems and methods may modify the timing of decoding unit removal. When sub-picture level CPB removal delay parameters are present, the removal time of decoding unit for “big pictures” (when low_delay_hrd_flag is 1 and t r,n  (m)&lt;t af (m)) may be changed to compensate for difference that can arise due to clock tick counter and sub-picture clock tick counter. 
     When sub_pic_cpb_params_present_flag equals to 1 then sub-picture level CPB removal delay parameters are present and the CPB may operate at access unit level or sub-picture level. sub_pic_cpb_params_present_flag equal to 0 specifies that sub-picture level CPB removal delay parameters are not present and the CPB operates at access unit level. When sub_pic_cpb_params_present_flag is not present, its value is inferred to be equal to 0. 
     Specifically, one example of timing of decoding unit removal and decoding of decoding unit implementation is as follows. The variable SubPicCpbPreferredFlag is either specified by external means, or when not specified by external means, set to 0. The variable SubPicCpbFlag is derived as follows: SubPicCpbFlag=SubPicCpbPreferredFlag &amp;&amp; sub_pic_cpb_params_present_flag. If SubPicCpbFlag is equal to 0, the CPB operates at access unit level and each decoding unit is an access unit. Otherwise the CPB operates at sub-picture level and each decoding unit is a subset of an access unit. 
     If SubPicCpbFlag is equal to 0, the variable CpbRemovalDelay(m) is set to the value of cpb_removal_delay in the picture timing SEI message associated with the access unit that is decoding unit m, and the variable T c  is set to t c . Otherwise the variable CpbRemovalDelay(m) is set to the value of du_cpb_removal_delay[i] for decoding unit m in the picture timing SEI message associated with the access unit that contains decoding unit m, and the variable T c  is set to t c_sub . 
     When a decoding unit m is the decoding unit with n equal to 0 (the first decoding unit of the access unit that initializes the HRD), the nominal removal time of the decoding unit from the CPB is specified by t r,n (0)=InitCpbRemovalDelay[SchedSelIdx]/90000. 
     When a decoding unit m is the first decoding unit of the first access unit of a buffering period that does not initialize the HRD, the nominal removal time of the decoding unit from the CPB is specified by t r,n (m)=t r,n (m b )+T c *CpbRemovalDelay(m) where t r,n (m b ) is the nominal removal time of the first decoding unit of the previous buffering period. 
     When a decoding unit m is the first decoding unit of a buffering period, m b  is set equal to m at the removal time t r,n (m) of the decoding unit m. 
     The nominal removal time t r,n (m) of a decoding unit m that is not the first decoding unit of a buffering period is given by t r,n (m)=t r,n (m b )+T c *CpbRemovalDelay(m) where t r,n (m b ) is the nominal removal time of the first decoding unit of the current buffering period. 
     The removal time of decoding unit m is specified as follows. The variable ClockDiff is defined as ClockDiff=(num_units_in_tick−(num_units_in_sub_tick*(num_decoding_units_minus1+1))/time_scale). In some case it may be requirement of a bitstream conformance that the parameters num_units_in_tick, num_units_in_sub_tick, num_decoding_units_minus1 are signaled such that following equation is satisfied. (num_units_in_tick−(num_units_in_sub_tick*(num_decoding_units_minus1+1)))&gt;=0 
     In some other case it may be requirement of a bitstream conformance that the parameters num_units_in_tick. num_units_in_sub_tick. num_decoding_units_minus1 may be signaled such that following equation is satisfied. (num_units_in_tick−(num_units_in_sub_tick*(num_decoding_units_minus1+1)))&lt;=0 If low_delay_hrd_flag is equal to 0 or t r,n (m)&gt;=t af (m), the removal time of decoding unit m is specified by t r (m)=t r,n (m). 
     Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)), and when sub_pic_cpb_params_present_flag equals to 1 and the CPB is operating at sub-picture level, and if ClockDiff is greater than zero the removal time of decoding unit m when it is the last decoding unit of the access unit n is specified by t r (m)=t r,n (m)+T c *Ceil((t af (m)−t r,n (m))/T c )+ClockDiff. 
     Otherwise (low_delay_hrd_flag is equal to 1 and tr,n(m)&lt;taf(m)), and when sub_pic_cpb_params_present_flag equals to 1 and the CPB is operating at access unit level and if ClockDiff is less than zero the removal time of access unit n is specified by t r (m)=t r,n (m)+t c *Ceil((t af (m)−t r,n (m))/t c )−ClockDiff. 
     Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)), the removal time of decoding unit m is specified by t r (m)=t r,n (m)+T c *Ceil((t af (m)−t r,n (m))/T c ). The latter case (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)) indicates that the size of decoding unit m, b(m), is so large that it prevents removal at the nominal removal time. 
     Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)) and when a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the last decoding unit m of access unit, t r (m) according to: t r (m)=t r,n (m)+min((t c_sub *Ceil((t af (m)−t r,n (m))/t c_sub )), (t c *Ceil((t af (n)−t r,n (n))/t c ))) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (n)&lt;t af (n)) and when a picture timing flag is set to 1 and the CPB is operating at access unit level, the removal time for access unit n, t r (n) according to: t r (n)=t r,n (n)+min((t c_sub *Ceil((t af (m)−t r,n (m))/t c_sub , (t c *Ceil((t af (n)−t r,n (n))/t c ))) where t r,n (m) is the nominal removal time of the last decoding unit n, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)) and a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the last decoding unit m of access unit, t r (m) according to: t r (m)=t r,n (m)+(t c *Ceil((t af (n)−t r,n (n))/t c )) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af  (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (n)&lt;t af (n)) and a picture timing flag is set to 1 and the CPB is operating at access unit level, the removal time for access unit n, t r (n) according to: t r (n)=t r,n (n)+(t c *Ceil((t af (n)−t r,n (n))/t c )) where t r,n (m) is the nominal removal time of the last decoding unit n, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)) and a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the decoding unit which is not the last decoding unit of the access unit is set as t r (m)=t af (m), where t af (m) is a final arrival time of decoding unit m. And the removal time of the last decoding unit m of access unit, t r (m) is set according to: t r (m)=t r,n (m)+(t c_sub *Ceil((t af (m)−t r,n (m))/t c_sub )) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n and t af (m) is a final arrival time of the last decoding unit m in the access unit n. 
     Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)) and a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the decoding unit which is not the last decoding unit of the access unit is set as t r (m)=t af (m), where t af (m) is a final arrival time of decoding unit m. And the removal time of the last decoding unit m of access unit, t r (m) is set according to: t r (m)=t r,n (m)+(t c *Ceil((t af (m)−t r,n (m))/t c )) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n and t af (m) is a final arrival time of the last decoding unit m in the access unit n. 
     Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (m)&lt;t af (m)) and a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the decoding unit is set as t r (m)=t af (m) where t r,n (m) is the nominal removal time of the decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n and t af (m) is a final arrival time of the decoding unit m in the access unit n. 
     Otherwise (low_delay_hrd_flag is equal to 1 and t r,n (n)&lt;t af (n)) and a picture timing flag is set to 1 and the CPB is operating at access unit level, the removal time for access unit n, t r (n) according to: t r (n)=t af (n) where t r,n (m) is the nominal removal time of the last decoding unit n, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     When SubPicCpbFlag is equal to 1, the nominal CPB removal time of access unit n t r,n (n) is set to the nominal CPB removal time of the last decoding unit in access unit n, the CPB removal time of access unit n t r (n) is set to the CPB removal time of the last decoding unit in access unit n. 
     When SubPicCpbFlag is equal to 0, each decoding unit is an access unit, hence the nominal CPB removal time and the CPB removal time of access unit n are the nominal CPB removal time and the CPB removal time of decoding unit n. At CPB removal time of decoding unit m, the decoding unit is instantaneously decoded. 
     As illustrated by the foregoing, the systems and methods disclosed herein provide syntax and semantics that modify a picture timing SEI message bitstreams carrying sub-picture based parameters. In some configurations, the systems and methods disclosed herein may be applied to HEVC specifications. 
     For convenience, several definitions are given as follows, which may be applied to the systems and methods disclosed herein. A random access point may be any point in a stream of data (e.g., bitstream) where decoding of the bitstream does not require access to any point in a bitstream preceding the random access point to decode a current picture and all pictures subsequent to said current picture in output order. 
     A buffering period may be specified as a set of access units between two instances of the buffering period SEI message in decoding order. Supplemental Enhancement Information (SEI) may contain information that is not necessary to decode the samples of coded pictures from VCL NAL units. SEI messages may assist in procedures related to decoding, display or other purposes. Conforming decoders may not be required to process this information for output order conformance to HEVC specifications (Annex C of HEVC specifications (JCTVC-I1003) includes specifications for conformance, for example). Some SEI message information may be used to check bitstream conformance and for output timing decoder conformance. 
     A buffering period SEI message may be an SEI message related to buffering period. A picture timing SEI message may be an SEI message related to CPB removal timing. These messages may define syntax and semantics which define bitstream arrival timing and coded picture removal timing. 
     A Coded Picture Buffer (CPB) may be a first-in first-out buffer containing access units in decoding order specified in a hypothetical reference decoder (HRD). An access unit may be a set of Network Access Layer (NAL) units that are consecutive in decoding order and contain exactly one coded picture. In addition to the coded slice NAL units of the coded picture, the access unit may also contain other NAL units not containing slices of the coded picture. The decoding of an access unit always results in a decoded picture. A NAL unit may be a syntax structure containing an indication of the type of data to follow and bytes containing that data in the form of a raw byte sequence payload interspersed as necessary with emulation prevention bytes. 
     As used herein, the term “common” generally refers to a syntax element or a variable that is applicable to more than one thing. For example, in the context of syntax elements in a picture timing SEI message, the term “common” may mean that the syntax element (e.g., common_du_cpb_removal_delay) is applicable to all decoding units in an access unit associated with the picture timing SEI message. Additionally, units of data are described in terms of “n” and “m” generally refer to access units and decoding units, respectively. 
     Various configurations are now described with reference to the Figures, where like reference numbers may indicate functionally similar elements. The systems and methods as generally described and illustrated in the Figures herein could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of several configurations, as represented in the Figures, is not intended to limit scope, as claimed, but is merely representative of the systems and methods. 
       FIG.  1 A  is a block diagram illustrating an example of one or more electronic devices  102  in which systems and methods for sending a message and buffering a bitstream may be implemented. In this example, electronic device A  102   a  and electronic device B  102   b  are illustrated. However, it should be noted that one or more of the features and functionality described in relation to electronic device A  102   a  and electronic device B  102   b  may be combined into a single electronic device in some configurations. 
     Electronic device A  102   a  includes an encoder  104 . The encoder  104  includes a message generation module  108 . Each of the elements included within electronic device A  102   a  (e.g., the encoder  104  and the message generation module  108 ) may be implemented in hardware, software or a combination of both. 
     Electronic device A  102   a  may obtain one or more input pictures  106 . In some configurations, the input picture(s)  106  may be captured on electronic device A  102   a  using an image sensor, may be retrieved from memory and/or may be received from another electronic device. 
     The encoder  104  may encode the input picture(s)  106  to produce encoded data. For example, the encoder  104  may encode a series of input pictures  106  (e.g., video). In one configuration, the encoder  104  may be a HEVC encoder. The encoded data may be digital data (e.g., part of a bitstream  114 ). The encoder  104  may generate overhead signaling based on the input signal. 
     The message generation module  108  may generate one or more messages. For example, the message generation module  108  may generate one or more SEI messages or other messages. For a CPB that supports operation on a sub-picture level, the electronic device  102  may send sub-picture parameters, (e.g., CPB removal delay parameter). Specifically, the electronic device  102  (e.g., the encoder  104 ) may determine whether to include a common decoding unit CPB removal delay parameter in a picture timing SEI message. For example, the electronic device may set a flag (e.g., common_du_cpb_removal_delay_flag) to one when the encoder  104  is including a common decoding unit CPB removal delay parameter (e.g., common_du_cpb_removal_delay) in the picture timing SEI message. When the common decoding unit CPB removal delay parameter is included, the electronic device may generate the common decoding unit CPB removal delay parameter that is applicable to all decoding units in an access unit. In other words, rather than including a decoding unit CPB removal delay parameter for each decoding unit in an access unit, a common parameter may apply to all decoding units in the access unit with which the picture timing SEI message is associated. 
     In contrast, when the common decoding unit CPB removal delay parameter is not to be included in the picture timing SEI message, the electronic device  102  may generate a separate decoding unit CPB removal delay for each decoding unit in the access unit with which the picture timing SEI message is associated. A message generation module  108  may perform one or more of the procedures described in connection with  FIG.  2    and  FIG.  3    below. 
     In some configurations, electronic device A  102   a  may send the message to electronic device B  102   b  as part of the bitstream  114 . In some configurations electronic device A  102   a  may send the message to electronic device B  102   b  by a separate transmission  110 . For example, the separate transmission may not be part of the bitstream  114 . For instance, a picture timing SEI message or other message may be sent using some out-of-band mechanism. It should be noted that, in some configurations, the other message may include one or more of the features of a picture timing SEI message described above. Furthermore, the other message, in one or more aspects, may be utilized similarly to the SEI message described above. 
     The encoder  104  (and message generation module  108 , for example) may produce a bitstream  114 . The bitstream  114  may include encoded picture data based on the input picture(s)  106 . In some configurations, the bitstream  114  may also include overhead data, such as a picture timing SEI message or other message, slice header(s), PPS(s), etc. As additional input pictures  106  are encoded, the bitstream  114  may include one or more encoded pictures. For instance, the bitstream  114  may include one or more encoded pictures with corresponding overhead data (e.g., a picture timing SEI message or other message). 
     The bitstream  114  may be provided to a decoder  112 . In one example, the bitstream  114  may be transmitted to electronic device B  102   b  using a wired or wireless link. In some cases, this may be done over a network, such as the Internet or a Local Area Network (LAN). As illustrated in  FIG.  1 A , the decoder  112  may be implemented on electronic device B  102   b  separately from the encoder  104  on electronic device A  102   a . However, it should be noted that the encoder  104  and decoder  112  may be implemented on the same electronic device in some configurations. In an implementation where the encoder  104  and decoder  112  are implemented on the same electronic device, for instance, the bitstream  114  may be provided over a bus to the decoder  112  or stored in memory for retrieval by the decoder  112 . 
     The decoder  112  may be implemented in hardware, software or a combination of both. In one configuration, the decoder  112  may be a HEVC decoder. The decoder  112  may receive (e.g., obtain) the bitstream  114 . The decoder  112  may generate one or more decoded pictures  118  based on the bitstream  114 . The decoded picture(s)  118  may be displayed, played back, stored in memory and/or transmitted to another device, etc. 
     The decoder  112  may include a CPB  120 . The CPB  120  may temporarily store encoded pictures. The CPB  120  may use parameters found in a picture timing SEI message to determine when to remove data. When the CPB  120  supports operation on a sub-picture level, individual decoding units may be removed rather than entire access units at one time. The decoder  112  may include a Decoded Picture Buffer (DPB)  122 . Each decoded picture is placed in the DPB  122  for being referenced by the decoding process as well as for output and cropping. A decoded picture is removed from the DPB at the later of the DPB output time or the time that it becomes no longer needed for inter-prediction reference. 
     The decoder  112  may receive a message (e.g., picture timing SEI message or other message). The decoder  112  may also determine whether the received message includes a common decoding unit CPB removal delay parameter (e.g., common_du_cpb_removal_delay). This may include identifying a flag (e.g., common_du_cpb_removal_delay_flag) that is set when the common parameter is present in the picture timing SEI message. If the common parameter is present, the decoder  112  may determine the common decoding unit CPB removal delay parameter applicable to all decoding units in the access unit. If the common parameter is not present, the decoder  112  may determine a separate decoding unit CPB removal delay parameter for each decoding unit in the access unit. The decoder  112  may also remove decoding units from the CPB  120  using either the common decoding unit CPB removal delay parameter or the separate decoding unit CPB removal delay parameters. The CPB  120  may perform one or more of the procedures described in connection with  FIG.  4    and  FIG.  5    below. 
     The HRD described above may be one example of the decoder  112  illustrated in  FIG.  1 A . Thus, an electronic device  102  may operate in accordance with the HRD and CPB  120  and DPB  122  described above, in some configurations. 
     It should be noted that one or more of the elements or parts thereof included in the electronic device(s)  102  may be implemented in hardware. For example, one or more of these elements or parts thereof may be implemented as a chip, circuitry or hardware components, etc. It should also be noted that one or more of the functions or methods described herein may be implemented in and/or performed using hardware. For example, one or more of the methods described herein may be implemented in and/or realized using a chipset, an Application-Specific Integrated Circuit (ASIC), a Large-Scale Integrated circuit (LSI) or integrated circuit, etc. 
       FIG.  1 B  is a block diagram illustrating another example of an encoder  1908  and a decoder  1972 . In this example, electronic device A  1902  and electronic device B  1970  are illustrated. However, it should be noted that the features and functionality described in relation to electronic device A  1902  and electronic device B  1970  may be combined into a single electronic device in some configurations. 
     Electronic device A  1902  includes the encoder  1908 . The encoder  1908  may include a base layer encoder  1910  and an enhancement layer encoder  1920 . The video encoder  1908  is suitable for scalable video coding and multi-view video coding, as described later. The encoder  1908  may be implemented in hardware, software or a combination of both. In one configuration, the encoder  1908  may be a high-efficiency video coding (HEVC) coder, including scalable and/or multi-view. Other coders may likewise be used. Electronic device A  1902  may obtain a source  1906 . In some configurations, the source  1906  may be captured on electronic device A  1902  using an image sensor, retrieved from memory or received from another electronic device. 
     The encoder  1908  may code the source  1906  to produce a base layer bitstream  1934  and an enhancement layer bitstream  1936 . For example, the encoder  1908  may code a series of pictures (e.g., video) in the source  1906 . In particular, for scalable video encoding for SNR scalability also known as quality scalability the same source  1906  may be provided to the base layer and the enhancement layer encoder. In particular, for scalable video encoding for spatial scalability a downsampled source may be used for the base layer encoder. In particular, for multi-view encoding a different view source may be used for the base layer encoder and the enhancement layer encoder. The encoder  1908  may be similar to the encoder  1782  described later in connection with  FIG.  6 B . 
     The bitstreams  1934 ,  1936  may include coded picture data based on the source  1906 . In some configurations, the bitstreams  1934 ,  1936  may also include overhead data, such as slice header information, PPS information, etc. As additional pictures in the source  1906  are coded, the bitstreams  1934 ,  1936  may include one or more coded pictures. 
     The bitstreams  1934 ,  1936  may be provided to the decoder  1972 . The decoder  1972  may include a base layer decoder  1980  and an enhancement layer decoder  1990 . The video decoder  1972  is suitable for scalable video decoding and multi-view video decoding. In one example, the bitstreams  1934 ,  1936  may be transmitted to electronic device B  1970  using a wired or wireless link. In some cases, this may be done over a network, such as the Internet or a Local Area Network (LAN). As illustrated in  FIG.  1 B , the decoder  1972  may be implemented on electronic device B  1970  separately from the encoder  1908  on electronic device A  1902 . However, it should be noted that the encoder  1908  and decoder  1972  may be implemented on the same electronic device in some configurations. In an implementation where the encoder  1908  and decoder  1972  are implemented on the same electronic device, for instance, the bitstreams  1934 ,  1936  may be provided over a bus to the decoder  1972  or stored in memory for retrieval by the decoder  1972 . The decoder  1972  may provide a decoded base layer  1992  and decoded enhancement layer picture(s)  1994  as output. 
     The decoder  1972  may be implemented in hardware, software or a combination of both. In one configuration, the decoder  1972  may be a high-efficiency video coding (HEVC) decoder, including scalable and/or multi-view. Other decoders may likewise be used. The decoder  1972  may be similar to the decoder  1812  described later in connection with  FIG.  7 B . Also, the base layer encoder and/or the enhancement layer encoder may each include a message generation module, such as that described in relation to  FIG.  1 A . Also, the base layer decoder and/or the enhancement layer decoder may include a coded picture buffer and/or a decoded picture buffer, such as that described in relation to  FIG.  1 A . In addition, the electronic devices of  FIG.  1 B  may operate in accordance with the functions of the electronic devices of  FIG.  1 A , as applicable. 
       FIG.  2    is a flow diagram illustrating one configuration of a method  200  for sending a message. The method  200  may be performed by an encoder  104  or one of its sub-parts (e.g., a message generation module  108 ). The encoder  104  may determine  202  a picture timing flag (e.g., sub_pic_cpb_params_present_flag) that indicates whether a CPB  120  supports operation on a sub-picture level. For example, when the picture timing flag is set to 1, the CPB  120  may operate on an access unit level or a sub-picture level. It should be noted that even when the picture timing flag is set to 1, the decision about whether to actually operate at the sub-picture level is left to the decoder  112  itself. 
     The encoder  104  may also determine  204  one or more removal delays for decoding units in an access unit. For example, the encoder  104  may determine a single common decoding unit CPB removal delay parameter (e.g., common_du_cpb_removal_delay) that is applicable to all decoding units in the access unit from the CPB  120 . Alternatively, the encoder  104  may determine a separate decoding unit CPB removal delay (e.g., du_cpb_removal_delay[i]) for each decoding unit in the access unit. 
     The encoder  104  may also determine  206  one or more NAL parameters that indicate an amount, offset by one, of NAL units in each decoding unit in the access point. For example, the encoder  104  may determine a single common NAL parameter (e.g., common_num_nalus_in_du_minus1) that is applicable to all decoding units in the access unit from the CPB  120 . Alternatively, the encoder  104  may determine a separate decoding unit CPB removal delay (e.g., num_nalus_in_du_minus1[i]) for each decoding unit in the access unit. 
     The encoder  104  may also send  208  a picture timing SEI message that includes the picture timing flag, the removal delays and the NAL parameters. The picture timing SEI message may also include other parameters (e.g., cpb_removal_delay, dpb_output_delay, etc). For example, the electronic device  102  may transmit the message via one or more of wireless transmission, wired transmission, device bus, network, etc. For instance, electronic device A  102   a  may transmit the message to electronic device B  102   b . The message may be part of the bitstream  114 , for example. In some configurations, electronic device A  102   a  may send  208  the message to electronic device B  102   b  in a separate transmission  110  (that is not part of the bitstream  114 ). 
     For instance, the message may be sent using some out-of-band mechanism. In some case the information indicated in  204 ,  206  may be sent in a SEI message different than picture timing SEI message. In yet another case the information indicated in  204 ,  206  may be sent in a parameter set e.g. video parameter set and/or sequence parameter set and/or picture parameter set and/or adaptation parameter set and/or slice header. 
       FIG.  3    is a flow diagram illustrating one configuration of a method  300  for determining one or more removal delays for decoding units in an access unit. In other words, the method  300  illustrated in  FIG.  3    may further illustrate step  204  in the method  200  illustrated in  FIG.  2   . The method  300  may be performed by an encoder  104 . The encoder  104  may determine  302  whether to include a common decoding unit CPB removal delay parameter (e.g., common_du_cpb_removal_delay). 
     This may include determining whether a common decoding unit CPB removal delay flag (e.g., common_du_cpb_removal_delay_flag) is set. An encoder  104  may send this common parameter in case the decoding units are removed from the CPB at regular interval. This may be the case, for example, when each decoding unit corresponds to certain number of rows of the picture or has some other regular structure. 
     For example, the common decoding unit CPB removal delay flag may be set to 1 when the common decoding unit CPB removal delay parameter is to be included in the picture timing SEI message and 0 when it is not to be included. If yes (e.g., flag is set to 1), the encoder  104  may determine  304  a common decoding unit CPB removal delay parameter (e.g., common_du_cpb_removal_delay) that is applicable to all decoding units in an access unit. If no (e.g., flag is set to 0), the encoder  104  may determine  306  separate decoding unit CPB removal delay parameters (e.g., du_cpb_removal_delay[i]) for each decoding unit in an access unit. 
     If a common decoding unit CPB removal delay parameter is present in a picture timing SEI message, it may specify an amount of sub-picture clock ticks to wait after removal from the CPB  120  of an immediately preceding decoding unit before removing from the CPB  120  a current decoding unit in the access unit associated with the picture timing SEI message. 
     For example, when a decoding unit is a first decoding unit in an access unit, the common decoding unit CPB  120  removal delay parameter may specify an amount of sub-picture clock ticks to wait after removal from the CPB  120  of a last decoding unit in an access unit associated with a most recent buffering period SEI message in a preceding access unit before removing from the CPB  120  the first decoding unit in the access unit associated with the picture timing SEI message. 
     When the decoding unit is a non-first decoding unit in an access unit, the common decoding unit CPB removal delay parameter may specify an amount of sub-picture clock ticks to wait after removal from the CPB  120  of a preceding decoding unit in the access unit associated with the picture timing SEI message before removing from the CPB a current decoding unit in the access unit associated with the picture timing SEI message. 
     In contrast, when a common decoding unit CPB removal delay parameter (e.g., common_du_cpb_removal_delay) is not sent in a picture timing SEI message, separate decoding unit CPB removal delay parameters (e.g., du_cpb_removal_delay[i]) may be included in the picture timing SEI message for each decoding unit in an access unit. The decoding unit CPB removal delay parameters (e.g., du_cpb_removal_delay[i]) may specify an amount of sub-picture clock ticks to wait after removal from the CPB  120  of the last decoding unit before removing from the CPB  120  an i-th decoding unit in the access unit associated with the picture timing SEI message. The decoding unit CPB removal delay parameters may be calculated according to a remainder of a modulo 2 (cpb_removal_delay_length_minus1+1)  counter where cpb_removal_delay_length_minus1+1 is a length of a common decoding unit CPB removal delay parameter. 
       FIG.  4    is a flow diagram illustrating one configuration of a method  400  for buffering a bitstream. The method  400  may be performed by a decoder  112  in an electronic device  102  (e.g., electronic device B  102   b ), which may receive  402  a message (e.g., a picture timing SEI message or other message). For example, the electronic device  102  may receive  402  the message via one or more of wireless transmission, wired transmission, device bus, network, etc. For instance, electronic device B  102   b  may receive  402  the message from electronic device A  102   a . The message may be part of the bitstream  114 , for example. In another example, electronic device B  102   b  may receive the message from electronic device A  102   a  in a separate transmission  110  (that is not part of the bitstream  114 , for example). For instance, the picture timing SEI message may be received using some out-of-band mechanism. In some configurations, the message may include one or more of a picture timing flag, one or more removal delays for decoding units in an access unit and one or more NAL parameters. Thus, receiving  402  the message may include receiving one or more of a picture timing flag, one or more removal delays for decoding units in an access unit and one or more NAL parameters. 
     The decoder  112  may determine  404  whether a CPB  120  operates on an access unit level or a sub-picture level. For example, a decoder  112  may decide to operate on sub-picture basis if it wants to achieve low latency. Alternatively, the decision may be based on whether the decoder  112  has enough resources to support sub-picture based operation. If the CPB  120  operates on a sub-picture level, the decoder may determine  406  one or more removal delays for decoding units in an access unit. For example, the decoder  112  may determine a single common decoding unit CPB removal delay parameter (e.g., common_du_cpb_removal_delay) that is applicable to all decoding units in the access unit. Alternatively, the decoder  112  may determine a separate decoding unit CPB removal delay (e.g., du_cpb_removal_delay[i]) for each decoding unit in the access unit. In other words, the picture timing SEI message may include a common parameter applicable to all decoding units in an access unit or separate parameters for every decoding unit. 
     The decoder  112  may also remove  408  decoding units based on the removal delays for the decoding units, i.e., using either a common parameter applicable to all decoding units in an access unit or separate parameters for every decoding unit. The decoder  112  may also decode  410  the decoding units. 
     The decoder  112  may use a variable ClockDiff when determining a removal time for determined from various signaled parameters. Specifically, ClockDiff may be determined according to ClockDiff=(num_units_in_tick−(num_units_in_sub_tick*(num_decoding_units_minus1+1))/time_scale) where num_units_in_tick is number of time units of a clock operating at the frequency time_scale Hz that corresponds to one increment of a clock tick counter, num_units_in_sub_tick is number of time units of a clock operating at the frequency time_scale Hz that corresponds to one increment of a sub-picture clock tick counter, num_decoding_units_minus1+1 is an amount of decoding units in the access unit, and time_scale is the number of time units that pass in one second. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1, the CPB is operating at sub-picture level and ClockDiff is greater than zero, the removal time for decoding unit m, t r (m) is determined according to: t r (m)=t r,n (m)+t c_sub *Ceil((t af  (m)−t r,n (m))/t c_sub )+ClockDiff where t r,n (m) is the nominal removal time of the decoding unit m, t c_sub  is a sub-picture clock tick, Ceil( ) is a ceiling function and t af (m) is final arrival time of decoding unit m. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (n)&lt;t af (n), a picture timing flag is set to 1, the CPB is operating at an access unit level and ClockDiff is greater than zero, the removal time for access unit n, t r (n) is determined according to: t r (n)=t r,n (n)+t c *Ceil((t af (n)−t r,n (n))/t c )−ClockDiff where t r,n (n) is the nominal removal time of the access unit n, t c  is a clock tick, Ceil( ) is a ceiling function and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the last decoding unit m of access unit, t r (m) according to: t r (m)=t r,n (m)+max((t c_sub *Ceil((t af (m)−t r,n (m))/t c_sub )), (t c *Ceil((t af (n)−t r,n (n))/t c ))) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag is set to 1, t r,n (n)&lt;t af (n), a picture timing flag is set to 1 and the CPB is operating at access unit level, the removal time for access unit n, t r (n) according to: t r (n)=t r,n (n)+max((t c_sub *Ceil((t af (m)−t r,n (m))/t c_sub )), (t c *Ceil((t af (n)−t r,n (n))/t c ))) where t r,n (m) is the nominal removal time of the last decoding unit n, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the last decoding unit m of access unit, t r (m) according to: t r (m)=t r,n (m)+min((t c_sub *Ceil((t af (m)−t r,n (m))/t c_sub ), (t c *Ceil((t af (n)−t r,n (n))/t c )) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag is set to 1, t r,n (n)&lt;t af (n), a picture timing flag is set to 1 and the CPB is operating at access unit level, the removal time for access unit n, t r (n) according to: t r (n)=t r,n (n)+min((t c_sub *Ceil((t af (m)−t r,n (m))/t c_sub )), (t c *Ceil((t af (n)−t r,n (n))/t c ))) where t r,n (m) is the nominal removal time of the last decoding unit n, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the last decoding unit m of access unit, t r (m) according to: t r (m)=t r,n (m)+(t c *Ceil((t af (n)−t r,n (n))/t c )) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag is set to 1, t r,n (n)&lt;t af (n), a picture timing flag is set to 1 and the CPB is operating at access unit level, the removal time for access unit n, t r (n) according to: t r (n)=t r,n (n)+(t c *Ceil((t af (n)−t r,n (n))/t c )) where t r,n (m) is the nominal removal time of the last decoding unit n, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the decoding unit which is not the last decoding unit of the access unit is set as t r (m)=t af (m), where t af (m) is a final arrival time of decoding unit m. And the removal time for the last decoding unit m of access unit, t r (m) according to: t r (m)=t r,n (m)+(t c_sub *Ceil((t af (m)−t r,n (m))/t c_sub )) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick, t af (n) is a final arrival time of access unit n and t af (m) is a final arrival time of the last decoding unit in the access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the decoding unit which is not the last decoding unit of the access unit is set as t r (m) t af (m), where t af (m) is a final arrival time of decoding unit m. And the removal time for the last decoding unit m of access unit, t r (m) according to: t r (m)=t r,n (m)+(t c *Ceil((t af (m)−t r,n (m))/t c )) where t r,n (m) is the nominal removal time of the last decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick, t af (n) is a final arrival time of access unit n and t af (m) is a final arrival time of the last decoding unit in the access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag (e.g., low_delay_hrd_flag) is set to 1, t r,n (m)&lt;t af (m), a picture timing flag is set to 1 and the CPB is operating at sub-picture level, the removal time for the decoding unit is set as t r (m)=t af (m) where t r,n (m) is the nominal removal time of the decoding unit m, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick, t af (n) is a final arrival time of access unit n and t af (m) is a final arrival time of the decoding unit in the access unit n. 
     When a low delay hypothetical reference decoder (HRD) flag is set to 1, t r,n (n)&lt;t af (n), a picture timing flag is set to 1 and the CPB is operating at access unit level, the removal time for access unit n, t r (n) according to: t r (n)=t af (n) where t r,n (m) is the nominal removal time of the last decoding unit n, t c_sub  is sub-picture clock tick, Ceil( ) is a ceiling function, t af (m) is a final arrival time of last decoding unit m, t r,n (n) is the nominal removal time of the access unit n, t c  is clock tick and t af (n) is a final arrival time of access unit n. 
     If the CPB operates on an access unit level, the decoder  112  may determine  412  a CPB removal delay parameter. This may be included in the received picture timing SEI message (e.g., cpb_removal_delay). The decoder  112  may also remove  414  an access unit based on the CPB removal delay parameter and decode  416  the access unit. In other words, the decoder  112  may decode whole access units at a time, rather than decoding units within the access unit. 
       FIG.  5    is a flow diagram illustrating one configuration of a method  500  for determining one or more removal delays for decoding units in an access unit. In other words, the method  500  illustrated in  FIG.  5    may further illustrate step  406  in the method  400  illustrated in  FIG.  4   . The method  500  may be performed by a decoder  112 . The decoder  112  may determine  502  whether a received picture timing SEI message includes a common decoding unit CPB removal delay parameter. This may include determining whether a common decoding unit CPB removal delay flag (e.g., common_du_cpb_removal_delay_flag) is set. If yes, the decoder  112  may determine  504  a common decoding unit CPB removal delay parameter (e.g., common_du_cpb_removal_delay) that is applicable to all decoding units in an access unit. If no, the decoder  112  may determine  506  separate decoding unit CPB removal delay parameters (e.g., du_cpb_removal_delay[i]) for each decoding unit in an access unit. 
     In addition to modifying the picture timing SEI message semantics, the present systems and methods may also impose a bitstream constraint so that the operation of sub-picture based CPB operation and access unit based CPB operation result in the same timing of decoding unit removal. Specifically, when the picture timing flag (e.g., sub_pic_cpb_params_present_flag) is set to 1, the CPB removal delay may be set according to 
     
       
         
           
             
               
                 
                   
                     
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     where du_cpb_removal_delay[i] are the decoding unit CPB removal delay parameters, t c  is a clock tick, t c,sub  is a sub-picture clock tick, num_decoding_units_minus1 is an amount of decoding units in the access unit offset by one, and i is an index. 
     Alternatively, the CPB removal delay may be set as described next: Let the variable T du (k) be defined as: 
     
       
         
           
             
               
                 
                   
                     
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     where du_cpb_removal_delay_minus1 k [i] and num_decoding_units_minus1 k  are parameters for I&#39;th decoding unit of k&#39;th access unit (with k=0 for the access unit that initialized the HRD and T du (k)=0 for k&lt;1), and where du_cpb_removal_delay_minus1 k [i]+1=du_cpb_removal_delay_minus1 k [i] is the decoding unit CPB removal delay parameter for the I&#39;th decoding unit of the k&#39;th access unit, and num_decoding_units_minus1 k  is the number of decoding units in the k&#39;th access unit, t c  is a clock tick, t c,sub  is a sub-picture clock tick, and i and k are an indices. Then when the picture timing flag (e.g., sub_pic_cpb_params_present_flag) is set to 1, the following condition shall be true: 
     (au_cpb_removal_delay_minus1+1)*t c ==T du (k), where (au_cpb_removal_delay_minus1+1)=cpb_removal_delay, the CPB removal delay. Thus in this case the CPB removal delay (au_cpb_removal_delay_minus1+1) is set such that the operation of sub-picture based CPB operation and access unit based CPB operation result in the same timing of access unit removal and last decoding unit of the access unit removal. 
     Alternatively, the CPB removal delay may be set according to 
     
       
         
           
             
               
                 
                   
                     
                       
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     where du_cpb_removal_delay[i] are the decoding unit CPB removal delay parameters, t c  is a clock tick, t c,sub  is a sub-picture clock tick, num_decoding_units_minus1 is an amount of decoding units in the access unit offset by one, and i is an index. 
     Alternatively, cpb_removal_delay and du_cpb_removal_delay[num_decoding_units_minus1] may be set according to: cpb_removal_delay*t c =du_cpb_removal_delay[num_decoding_units_minus1]*t c,sub  where du_cpb_removal_delay[num_decoding_units_minus1] is the decoding unit CPB removal delay parameter for the num_decoding_units_minus1&#39;th decoding unit, t c  is a clock tick, t c,sub  is a sub-picture clock tick, num_decoding_units_minus1 is an amount of decoding units in the access unit offset by one. 
     In addition to modifying the picture timing SEI message semantics, the present systems and methods may also impose a bitstream constraint so that the operation of sub-picture based CPB operation and access unit based CPB operation result in the same timing of decoding unit removal. Specifically, when the picture timing flag (e.g., sub_pic_cpb_params_present_flag) is set to 1, the values for cpb_removal_delay and du_cpb_removal_delay[num_decoding_units_minus1] may be set so as to satisfy: −1&lt;=(cpb_removal_delay*t c −du_cpb_removal_delay[num_decoding_units_minus1]*t c,sub )&lt;=1 where du_cpb_removal_delay[num_decoding_units_minus1] is the decoding unit CPB removal delay parameter for the num_decoding_units_minus1&#39;th decoding unit, t c  is a clock tick, t c,sub  is a sub-picture clock tick, num_decoding_units_minus1 is an amount of decoding units in the access unit offset by one. 
       FIG.  6 A  is a block diagram illustrating one configuration of an encoder  604  on an electronic device  602 . It should be noted that one or more of the elements illustrated as included within the electronic device  602  may be implemented in hardware, software or a combination of both. For example, the electronic device  602  includes an encoder  604 , which may be implemented in hardware, software or a combination of both. For instance, the encoder  604  may be implemented as a circuit, integrated circuit, application-specific integrated circuit (ASIC), processor in electronic communication with memory with executable instructions, firmware, field-programmable gate array (FPGA), etc., or a combination thereof. In some configurations, the encoder  604  may be a HEVC coder. 
     The electronic device  602  may include a source  622 . The source  622  may provide picture or image data (e.g., video) as one or more input pictures  606  to the encoder  604 . Examples of the source  622  may include image sensors, memory, communication interfaces, network interfaces, wireless receivers, ports, etc. 
     One or more input pictures  606  may be provided to an intra-frame prediction module and reconstruction buffer  624 . An input picture  606  may also be provided to a motion estimation and motion compensation module  646  and to a subtraction module  628 . 
     The intra-frame prediction module and reconstruction buffer  624  may generate intra mode information  640  and an intra-signal  626  based on one or more input pictures  606  and reconstructed data  660 . The motion estimation and motion compensation module  646  may generate inter mode information  648  and an inter signal  644  based on one or more input pictures  606  and a reference picture  678  from decoded picture buffer  676 . In some configurations, the decoded picture buffer  676  may include data from one or more reference pictures in the decoded picture buffer  676 . 
     The encoder  604  may select between the intra signal  626  and the inter signal  644  in accordance with a mode. The intra signal  626  may be used in order to exploit spatial characteristics within a picture in an intra-coding mode. The inter signal  644  may be used in order to exploit temporal characteristics between pictures in an inter coding mode. While in the intra coding mode, the intra signal  626  may be provided to the subtraction module  628  and the intra mode information  640  may be provided to an entropy coding module  642 . While in the inter coding mode, the inter signal  644  may be provided to the subtraction module  628  and the inter mode information  648  may be provided to the entropy coding module  642 . 
     Either the intra signal  626  or the inter signal  644  (depending on the mode) is subtracted from an input picture  606  at the subtraction module  628  in order to produce a prediction residual  630 . The prediction residual  630  is provided to a transformation module  632 . The transformation module  632  may compress the prediction residual  630  to produce a transformed signal  634  that is provided to a quantization module  636 . The quantization module  636  quantizes the transformed signal  634  to produce transformed and quantized coefficients (TQCs)  638 . 
     The TQCs  638  are provided to an entropy coding module  642  and an inverse quantization module  650 . The inverse quantization module  650  performs inverse quantization on the TQCs  638  to produce an inverse quantized signal  652  that is provided to an inverse transformation module  654 . The inverse transformation module  654  decompresses the inverse quantized signal  652  to produce a decompressed signal  656  that is provided to a reconstruction module  658 . 
     The reconstruction module  658  may produce reconstructed data  660  based on the decompressed signal  656 . For example, the reconstruction module  658  may reconstruct (modified) pictures. The reconstructed data  660  may be provided to a deblocking filter  662  and to the intra prediction module and reconstruction buffer  624 . The deblocking filter  662  may produce a filtered signal  664  based on the reconstructed data  660 . 
     The filtered signal  664  may be provided to a sample adaptive offset (SAO) module  666 . The SAO module  666  may produce SAO information  668  that is provided to the entropy coding module  642  and an SAO signal  670  that is provided to an adaptive loop filter (ALF)  672 . The ALF  672  produces an ALF signal  674  that is provided to the decoded picture buffer  676 . The ALF signal  674  may include data from one or more pictures that may be used as reference pictures. 
     The entropy coding module  642  may code the TQCs  638  to produce bitstream A  614   a  (e.g., encoded picture data). For example, the entropy coding module  642  may code the TQCs  638  using Context-Adaptive Variable Length Coding (CAVLC) or Context-Adaptive Binary Arithmetic Coding (CABAC). In particular, the entropy coding module  642  may code the TQCs  638  based on one or more of intra mode information  640 , inter mode information  648  and SAO information  668 . Bitstream A  614   a  (e.g., encoded picture data) may be provided to a message generation module  608 . The message generation module  608  may be configured similarly to the message generation module  108  described in connection with  FIG.  1   . Additionally or alternatively, the message generation module  608  may perform one or more of the procedures described in connection with  FIG.  2    and  FIG.  3   . 
     For example, the message generation module  608  may generate a message (e.g., picture timing SEI message or other message) including sub-picture parameters. The sub-picture parameters may include one or more removal delays for decoding units (e.g., common_du_cpb_removal_delay or du_cpb_removal_delay[i]) and one or more NAL parameters (e.g., common_num_nalus_in_du_minus1 or num_nalus_in_du_minus1[i]). In some configurations, the message may be inserted into bitstream A  614   a  to produce bitstream B  614   b . Thus, the message may be generated after the entire bitstream A  614   a  is generated (e.g., after most of bitstream B  614   b  is generated), for example. In other configurations, the message may not be inserted into bitstream A  614   a  (in which case bitstream B  614   b  may be the same as bitstream A  614   a ), but may be provided in a separate transmission  610 . 
     In some configurations, the electronic device  602  sends the bitstream  614  to another electronic device. For example, the bitstream  614  may be provided to a communication interface, network interface, wireless transmitter, port, etc. For instance, the bitstream  614  may be transmitted to another electronic device via LAN, the Internet, a cellular phone base station, etc. The bitstream  614  may additionally or alternatively be stored in memory or other component on the electronic device  602 . 
       FIG.  6 B  is a block diagram illustrating one configuration of a video encoder  1782  on an electronic device  1702 . The video encoder  1782  may include an enhancement layer encoder  1706 , a base layer encoder  1709 , a resolution upscaling block  1770  and an output interface  1780 . The video encoder of  FIG.  6 B , for example, is suitable for scalable video coding and multi-view video coding, as described herein. 
     The enhancement layer encoder  1706  may include a video input  1781  that receives an input picture  1704 . The output of the video input  1781  may be provided to an adder/subtractor  1783  that receives an output of a prediction selection  1750 . The output of the adder/subtractor  1783  may be provided to a transform and quantize block  1752 . The output of the transform and quantize block  1752  may be provided to an entropy encoding  1748  block and a scaling and inverse transform block  1772 . After entropy encoding  1748  is performed, the output of the entropy encoding block  1748  may be provided to the output interface  1780 . The output interface  1780  may output both the encoded base layer video bitstream  1707  and the encoded enhancement layer video bitstream  1710 . 
     The output of the scaling and inverse transform block  1772  may be provided to an adder  1779 . The adder  1779  may also receive the output of the prediction selection  1750 . The output of the adder  1779  may be provided to a deblocking block  1751 . The output of the deblocking block  1751  may be provided to a reference buffer  1794 . An output of the reference buffer  1794  may be provided to a motion compensation block  1754 . The output of the motion compensation block  1754  may be provided to the prediction selection  1750 . An output of the reference buffer  1794  may also be provided to an intra predictor  1756 . The output of the intra predictor  1756  may be provided to the prediction selection  1750 . The prediction selection  1750  may also receive an output of the resolution upscaling block  1770 . 
     The base layer encoder  1709  may include a video input  1762  that receives a downsampled input picture, or other image content suitable for combing with another image, or an alternative view input picture or the same input picture  1703  (i.e., the same as the input picture  1704  received by the enhancement layer encoder  1706 ). The output of the video input  1762  may be provided to an encoding prediction loop  1764 . Entropy encoding  1766  may be provided on the output of the encoding prediction loop  1764 . The output of the encoding prediction loop  1764  may also be provided to a reference buffer  1768 . The reference buffer  1768  may provide feedback to the encoding prediction loop  1764 . The output of the reference buffer  1768  may also be provided to the resolution upscaling block  1770 . Once entropy encoding  1766  has been performed, the output may be provided to the output interface  1780 . The encoded base layer video bitstream  1707  and/or the encoded enhancement layer video bitstream  1710  may be provided to one or more message generation modules, as desired. 
       FIG.  7 A  is a block diagram illustrating one configuration of a decoder  712  on an electronic device  702 . The decoder  712  may be included in an electronic device  702 . For example, the decoder  712  may be a HEVC decoder. The decoder  712  and one or more of the elements illustrated as included in the decoder  712  may be implemented in hardware, software or a combination of both. The decoder  712  may receive a bitstream  714  (e.g., one or more encoded pictures and overhead data included in the bitstream  714 ) for decoding. In some configurations, the received bitstream  714  may include received overhead data, such as a message (e.g., picture timing SEI message or other message), slice header, PPS, etc. In some configurations, the decoder  712  may additionally receive a separate transmission  710 . The separate transmission  710  may include a message (e.g., a picture timing SEI message or other message). For example, a picture timing SEI message or other message may be received in a separate transmission  710  instead of in the bitstream  714 . However, it should be noted that the separate transmission  710  may be optional and may not be utilized in some configurations. 
     The decoder  712  includes a CPB  720 . The CPB  720  may be configured similarly to the CPB  120  described in connection with  FIG.  1    above. Additionally or alternatively, the decoder  712  may perform one or more of the procedures described in connection with  FIG.  4    and  FIG.  5   . For example, the decoder  712  may receive a message (e.g., picture timing SEI message or other message) with sub-picture parameters and remove and decode decoding units in an access unit based on the sub-picture parameters. It should be noted that one or more access units may be included in the bitstream and may include one or more of encoded picture data and overhead data. 
     The Coded Picture Buffer (CPB)  720  may provide encoded picture data to an entropy decoding module  701 . The encoded picture data may be entropy decoded by an entropy decoding module  701 , thereby producing a motion information signal  703  and quantized, scaled and/or transformed coefficients  705 . 
     The motion information signal  703  may be combined with a portion of a reference frame signal  798  from a decoded picture buffer  709  at a motion compensation module  780 , which may produce an inter-frame prediction signal  782 . The quantized, descaled and/or transformed coefficients  705  may be inverse quantized, scaled and inverse transformed by an inverse module  707 , thereby producing a decoded residual signal  784 . The decoded residual signal  784  may be added to a prediction signal  792  to produce a combined signal  786 . The prediction signal  792  may be a signal selected from either the inter-frame prediction signal  782  produced by the motion compensation module  780  or an intra-frame prediction signal  790  produced by an intra-frame prediction module  788 . In some configurations, this signal selection may be based on (e.g., controlled by) the bitstream  714 . 
     The intra-frame prediction signal  790  may be predicted from previously decoded information from the combined signal  786  (in the current frame, for example). The combined signal  786  may also be filtered by a de-blocking filter  794 . The resulting filtered signal  796  may be written to decoded picture buffer  709 . The resulting filtered signal  796  may include a decoded picture. The decoded picture buffer  709  may provide a decoded picture which may be outputted  718 . In some cases  709  may be a considered as frame memory. 
       FIG.  7 B  is a block diagram illustrating one configuration of a video decoder  1812  on an electronic device  1802 . The video decoder  1812  may include an enhancement layer decoder  1815  and a base layer decoder  1813 . The video decoder  812  may also include an interface  1889  and resolution upscaling  1870 . The video decoder of  FIG.  7 B , for example, is suitable for scalable video decoding and multi-view video decoding, as described herein. 
     The interface  1889  may receive an encoded video stream  1885 . The encoded video stream  1885  may consist of base layer encoded video stream and enhancement layer encoded video stream. These two streams may be sent separately or together. The interface  1889  may provide some or all of the encoded video stream  1885  to an entropy decoding block  1886  in the base layer decoder  1813 . The output of the entropy decoding block  1886  may be provided to a decoding prediction loop  1887 . The output of the decoding prediction loop  1887  may be provided to a reference buffer  1888 . The reference buffer may provide feedback to the decoding prediction loop  1887 . The reference buffer  1888  may also output the decoded base layer video stream  1884 . 
     The interface  1889  may also provide some or all of the encoded video stream  1885  to an entropy decoding block  1890  in the enhancement layer decoder  1815 . The output of the entropy decoding block  1890  may be provided to an inverse quantization block  1891 . The output of the inverse quantization block  1891  may be provided to an adder  1892 . The adder  1892  may add the output of the inverse quantization block  1891  and the output of a prediction selection block  1895 . The output of the adder  1892  may be provided to a deblocking block  1893 . The output of the deblocking block  1893  may be provided to a reference buffer  1894 . The reference buffer  1894  may output the decoded enhancement layer video stream  1882 . The output of the reference buffer  1894  may also be provided to an intra predictor  1897 . The enhancement layer decoder  1815  may include motion compensation  1896 . The motion compensation  1896  may be performed after the resolution upscaling  1870 . The prediction selection block  1895  may receive the output of the intra predictor  1897  and the output of the motion compensation  1896 . Also, the decoder may include one or more coded picture buffers, as desired, such as together with the interface  1889 . 
       FIG.  8    illustrates various components that may be utilized in a transmitting electronic device  802 . One or more of the electronic devices  102 ,  602 ,  702  described herein may be implemented in accordance with the transmitting electronic device  802  illustrated in  FIG.  8   . 
     The transmitting electronic device  802  includes a processor  817  that controls operation of the electronic device  802 . The processor  817  may also be referred to as a CPU. Memory  811 , which may include both read-only memory (ROM), random access memory (RAM) or any type of device that may store information, provides instructions  813   a  (e.g., executable instructions) and data  815   a  to the processor  817 . A portion of the memory  811  may also include non-volatile random access memory (NVRAM). The memory  811  may be in electronic communication with the processor  817 . 
     Instructions  813   b  and data  815   b  may also reside in the processor  817 . Instructions  813   b  and/or data  815   b  loaded into the processor  817  may also include instructions  813   a  and/or data  815   a  from memory  811  that were loaded for execution or processing by the processor  817 . The instructions  813   b  may be executed by the processor  817  to implement the systems and methods disclosed herein. For example, the instructions  813   b  may be executable to perform one or more of the methods  200 ,  300 ,  400 ,  500  described above. 
     The transmitting electronic device  802  may include one or more communication interfaces  819  for communicating with other electronic devices (e.g., receiving electronic device). The communication interfaces  819  may be based on wired communication technology, wireless communication technology, or both. Examples of a communication interface  819  include a serial port, a parallel port, a Universal Serial Bus (USB), an Ethernet adapter, an IEEE 1394 bus interface, a small computer system interface (SCSI) bus interface, an infrared (IR) communication port, a Bluetooth wireless communication adapter, a wireless transceiver in accordance with 3 rd  Generation Partnership Project (3GPP) specifications and so forth. 
     The transmitting electronic device  802  may include one or more output devices  823  and one or more input devices  821 . Examples of output devices  823  include a speaker, printer, etc. One type of output device that may be included in an electronic device  802  is a display device  825 . Display devices  825  used with configurations disclosed herein may utilize any suitable image projection technology, such as a cathode ray tube (CRT), liquid crystal display (LCD), light-emitting diode (LED), gas plasma, electroluminescence or the like. A display controller  827  may be provided for converting data stored in the memory  811  into text, graphics, and/or moving images (as appropriate) shown on the display  825 . Examples of input devices  821  include a keyboard, mouse, microphone, remote control device, button, joystick, trackball, touchpad, touchscreen, lightpen, etc. 
     The various components of the transmitting electronic device  802  are coupled together by a bus system  829 , which may include a power bus, a control signal bus and a status signal bus, in addition to a data bus. However, for the sake of clarity, the various buses are illustrated in  FIG.  8    as the bus system  829 . The transmitting electronic device  802  illustrated in  FIG.  8    is a functional block diagram rather than a listing of specific components. 
       FIG.  9    is a block diagram illustrating various components that may be utilized in a receiving electronic device  902 . One or more of the electronic devices  102 ,  602 ,  702  described herein may be implemented in accordance with the receiving electronic device  902  illustrated in  FIG.  9   . 
     The receiving electronic device  902  includes a processor  917  that controls operation of the electronic device  902 . The processor  917  may also be referred to as a CPU. Memory  911 , which may include both read-only memory (ROM), random access memory (RAM) or any type of device that may store information, provides instructions  913   a  (e.g., executable instructions) and data  915   a  to the processor  917 . A portion of the memory  911  may also include non-volatile random access memory (NVRAM). The memory  911  may be in electronic communication with the processor  917 . 
     Instructions  913   b  and data  915   b  may also reside in the processor  917 . Instructions  913   b  and/or data  915   b  loaded into the processor  917  may also include instructions  913   a  and/or data  915   a  from memory  911  that were loaded for execution or processing by the processor  917 . The instructions  913   b  may be executed by the processor  917  to implement the systems and methods disclosed herein. For example, the instructions  913   b  may be executable to perform one or more of the methods  200 ,  300 ,  400 ,  500  described above. 
     The receiving electronic device  902  may include one or more communication interfaces  919  for communicating with other electronic devices (e.g., a transmitting electronic device). The communication interface  919  may be based on wired communication technology, wireless communication technology, or both. Examples of a communication interface  919  include a serial port, a parallel port, a Universal Serial Bus (USB), an Ethernet adapter, an IEEE 1394 bus interface, a small computer system interface (SCSI) bus interface, an infrared (IR) communication port, a Bluetooth wireless communication adapter, a wireless transceiver in accordance with 3 rd  Generation Partnership Project (3GPP) specifications and so forth. 
     The receiving electronic device  902  may include one or more output devices  923  and one or more input devices  921 . Examples of output devices  923  include a speaker, printer, etc. One type of output device that may be included in an electronic device  902  is a display device  925 . Display devices  925  used with configurations disclosed herein may utilize any suitable image projection technology, such as a cathode ray tube (CRT), liquid crystal display (LCD), light-emitting diode (LED), gas plasma, electroluminescence or the like. A display controller  927  may be provided for converting data stored in the memory  911  into text, graphics, and/or moving images (as appropriate) shown on the display  925 . Examples of input devices  921  include a keyboard, mouse, microphone, remote control device, button, joystick, trackball, touchpad, touchscreen, lightpen, etc. 
     The various components of the receiving electronic device  902  are coupled together by a bus system  929 , which may include a power bus, a control signal bus and a status signal bus, in addition to a data bus. However, for the sake of clarity, the various buses are illustrated in  FIG.  9    as the bus system  929 . The receiving electronic device  902  illustrated in  FIG.  9    is a functional block diagram rather than a listing of specific components. 
       FIG.  10    is a block diagram illustrating one configuration of an electronic device  1002  in which systems and methods for sending a message may be implemented. The electronic device  1002  includes encoding means  1031  and transmitting means  1033 . The encoding means  1031  and transmitting means  1033  may be configured to perform one or more of the functions described in connection with one or more of  FIG.  1   ,  FIG.  2   ,  FIG.  3   ,  FIG.  6    and  FIG.  8    above. For example, the encoding means  1031  and transmitting means  1033  may generate a bitstream  1014 .  FIG.  8    above illustrates one example of a concrete apparatus structure of  FIG.  10   . Other various structures may be implemented to realize one or more of the functions of  FIG.  1   ,  FIG.  2   ,  FIG.  3   ,  FIG.  6    and  FIG.  8   . For example, a DSP may be realized by software. 
       FIG.  11    is a block diagram illustrating one configuration of an electronic device  1102  in which systems and methods for buffering a bitstream  1114  may be implemented. The electronic device  1102  may include receiving means  1135  and decoding means  1137 . The receiving means  1135  and decoding means  1137  may be configured to perform one or more of the functions described in connection with one or more of  FIG.  1   ,  FIG.  4   ,  FIG.  5   ,  FIG.  7    and  FIG.  9    above. For example, the receiving means  1135  and decoding means  1137  may receive a bitstream  1114 .  FIG.  9    above illustrates one example of a concrete apparatus structure of  FIG.  11   . Other various structures may be implemented to realize one or more functions of  FIG.  1   ,  FIG.  4   ,  FIG.  5   ,  FIG.  7    and  FIG.  9   . For example, a DSP may be realized by software. 
       FIG.  12    is a flow diagram illustrating one configuration of a method  1200  for operation of decoded picture buffer (DPB). The method  1200  may be performed by an encoder  104  or one of its sub-parts (e.g., a decoded picture buffer module  676 ). The method  1200  may be performed by a decoder  112  in an electronic device  102  (e.g., electronic device B  102   b ). Additionally or alternatively the method  1200  may be performed by a decoder  712  or one of its sub-parts (e.g., a decoded picture buffer module  709 ). The decoder may parse first slice header of a picture  1202 . The output and removal of pictures from DPB before decoding of the current picture (but after parsing the slice header of the first slice of the current picture) happens instantaneously when first decoding unit of the access unit containing the current picture is removed from the CPB and proceeds as follows.
         The decoding process for reference picture set (RPS) is invoked. Reference picture set is a set of reference pictures associated with a picture, consisting of all reference pictures that are prior to the associated picture in decoding order, that may be used for inter prediction of the associated picture or any picture following the associated picture in decoding order.   The bitstream of the video may include a syntax structure that is placed into logical data packets generally referred to as Network Abstraction Layer (NAL) units. Each NAL unit includes a NAL unit header, such as a two-byte NAL unit header (e.g., 16 bits), to identify the purpose of the associated data payload. For example, each coded slice (and/or picture) may be coded in one or more slice (and/or picture) NAL units. Other NAL units may be included for other categories of data, such as for example, supplemental enhancement information, coded slice of temporal sub-layer access (TSA) picture, coded slice of step-wise temporal sub-layer access (STSA) picture, coded slice a non-TSA, non-STSA trailing picture, coded slice of broken link access picture, coded slice of instantaneous decoded refresh picture, coded slice of clean random access picture, coded slice of decodable leading picture, coded slice of tagged for discard picture, video parameter set, sequence parameter set, picture parameter set, access unit delimiter, end of sequence, end of bitstream, filler data, and/or sequence enhancement information message. Table (4) illustrates one example of NAL unit codes and NAL unit type classes. Other NAL unit types may be included, as desired. It should also be understood that the NAL unit type values for the NAL units shown in the Table (4) may be reshuffled and reassigned. Also additional NAL unit types may be added. Also some NAL unit types may be removed.       

     An intra random access point (IRAP) picture is a coded picture for which each video coding layer NAL unit has nal_unit_type in the range of BLA_W_LP to RSV_IRAP_VCL23, inclusive as shown in Table (4). An IRAP picture contains only Intra coded (I) slices. An instantaneous decoding refresh (IDR) picture is an IRAP picture for which each video coding layer NAL unit has nal_unit_type equal to IDR_W_RADL or IDR_N_LP as shown in Table (4). An instantaneous decoding refresh (IDR) picture contains only I slices, and may be the first picture in the bitstream in decoding order, or may appear later in the bitstream. Each IDR picture is the first picture of a coded video sequence (CVS) in decoding order. A broken link access (BLA) picture is an IRAP picture for which each video coding layer NAL unit has nal_unit_type equal to BLA_W_LP, BLA_W_RADL, or BLA_N_LP as shown in Table (4). A BLA picture contains only I slices, and may be the first picture in the bitstream in decoding order, or may appear later in the bitstream. Each BLA picture begins a new coded video sequence, and has the same effect on the decoding process as an IDR picture. However, a BLA picture contains syntax elements that specify a non-empty reference picture set. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                   
                   
                 NAL  
               
               
                 nal_ 
                   
                 Content of NAL unit and raw  
                 unit  
               
               
                 unit_  
                 Name of  
                 byte sequence payload (RBSP)  
                 type  
               
               
                 type  
                 nal_unit_type  
                 syntax structure  
                 class 
               
               
                   
               
             
            
               
                  0  
                 TRAIL_N  
                 Coded slice segment of a  
                 Video  
               
               
                  1  
                 TRAIL_R  
                 non-TSA, non-STSA trailing  
                 Coding  
               
               
                   
                   
                 picture  
                 Layer  
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                 (VCL)  
               
               
                  2  
                 TSA_N  
                 Coded slice segment of a  
                 VCL  
               
               
                  3  
                 TSA_R  
                 temporal sub-layer access (TSA)  
                   
               
               
                   
                   
                 picture  
                   
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                   
               
               
                  4  
                 STSA_N  
                 Coded slice segment of an  
                 VCL  
               
               
                  5  
                 STSA_R  
                 Step-wise Temporal sub-layer  
                   
               
               
                   
                   
                 access (STSA) picture  
                   
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                   
               
               
                  6  
                 RADL_N  
                 Coded slice segment of a random  
                 VCL  
               
               
                  7  
                 RADL_R  
                 access decodable leading  
                   
               
               
                   
                   
                 (RADL) picture  
                   
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                   
               
               
                  8  
                 RASL_N  
                 Coded slice segment of a random  
                 VCL  
               
               
                  9  
                 RASL_R  
                 access skipped leading (RASL)  
                   
               
               
                   
                   
                 picture  
                   
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                   
               
               
                 10  
                 RSV_VCL_N10  
                 Reserved non-IRAP sub-layer  
                 VCL  
               
               
                 12  
                 RSV_VCL_N12  
                 non-reference VCL NAL unit  
                   
               
               
                 14  
                 RSV_VCL_N14  
                 types  
                   
               
               
                 11  
                 RSV_VCC_R11  
                 Reserved non-IRAP sub-layer  
                 VCL  
               
               
                 13  
                 RSV_VCL_R13  
                 reference VCL NAL unit types  
                   
               
               
                 15  
                 RSV_VCL_R15  
                   
                   
               
               
                 16  
                 BLA_W_LP  
                 Coded slice segment of a broken  
                 VCL  
               
               
                 17  
                 BLA_W_RADL  
                 link access (BLA) picture  
                   
               
               
                 18  
                 BLA_N_LP  
                 slice_segment_layer_rbsp( )  
                   
               
               
                 19  
                 IDR_W_RADL  
                 Coded slice segment of an  
                 VCL  
               
               
                 20  
                 IDR_N_LP  
                 instantaneous decoding refresh  
                   
               
               
                   
                   
                 (IDR) picture  
                   
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                   
               
               
                 21  
                 CRA_NUT  
                 Coded slice segment of a clean  
                 VCL  
               
               
                   
                   
                 random access (CRA) picture  
                   
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                   
               
               
                 22  
                 RSV_IRAP_VCL22  
                 Reserved IRAP VCL NAL unit  
                 VCL  
               
               
                 23  
                 RSV_IRAP_VCL23  
                 types  
                   
               
               
                 24 . . . 31  
                 RSV_VCL24 . . .  
                 Reserved non-IRAP VCL NAL  
                 VCL  
               
               
                   
                 RSV_VCL31  
                 unit types  
                   
               
               
                 32  
                 VPS_NUT  
                 Video parameter set  
                 non-  
               
               
                   
                   
                 video_parameter_set_rbsp( )  
                 video  
               
               
                   
                   
                   
                 coding  
               
               
                   
                   
                   
                 layer  
               
               
                   
                   
                   
                 (non-  
               
               
                   
                   
                   
                 VCL)  
               
               
                 33  
                 SPS_NUT  
                 Sequence parameter set  
                 non-  
               
               
                   
                   
                 seq_parameter_set_rbsp( )  
                 VCL  
               
               
                 34  
                 PPS_NUT  
                 Picture parameter set  
                 non-  
               
               
                   
                   
                 pic_parameter_set_rbsp( )  
                 VCL  
               
               
                 35  
                 AUD_NUT  
                 Access unit delimiter  
                 non-  
               
               
                   
                   
                 access_unit_delimiter_rbsp( )  
                 VCL  
               
               
                 36  
                 EOS_NUT  
                 End of sequence  
                 non-  
               
               
                   
                   
                 end_of_seq_rbsp( )  
                 VCL  
               
               
                 37  
                 EOB_NUT  
                 End of bitstream  
                 non-  
               
               
                   
                   
                 end_of_bitstream_rbsp( )  
                 VCL  
               
               
                 38  
                 FD_NUT  
                 Filler data  
                 non-  
               
               
                   
                   
                 filler_data_rbsp( )  
                 VCL  
               
               
                 39  
                 PREFIX_SEI_NUT  
                 Supplemental enhancement  
                 non-  
               
               
                 40  
                 SUFFIX_SEI_NUT  
                 information  
                 VCL  
               
               
                   
                   
                 sei_rbsp( )  
                   
               
               
                 41 . . . 47  
                 RSV_NVCL41 . . .  
                 Reserved  
                 non-  
               
               
                   
                 RSV_NVCL47  
                   
                 VCL  
               
               
                 48 . . . 63  
                 UNSPEC48 . . .  
                 Unspecified  
                 non-  
               
               
                   
                 UNSPEC63  
                   
                 VCL 
               
               
                   
               
               
                 Table (4) 
               
            
           
         
       
     
     Referring to Table (5), the NAL unit header syntax may include two bytes of data, namely, 16 bits. The first bit is a “forbidden_zero_bit” which is always set to zero at the start of a NAL unit. The next six bits is a “nal_unit_type” which specifies the type of raw byte sequence payloads (“RBSP”) data structure contained in the NAL unit as shown in Table (4). The next 6 bits is a “nuh_layer_id” which specify the identifier of the layer. In some cases these six bits may be specified as “nuh_reserved_zero_6bits” instead. The nuh_reserved_zero_6bits may be equal to 0 in the base specification of the standard. In a scalable video coding and/or syntax extensions nuh_layer_id may specify that this particular NAL unit belongs to the layer identified by the value of these 6 bits. The next syntax element is “nuh_temporal_id_plus1”. The nuh_temporal_id_plus1 minus 1 may specify a temporal identifier for the NAL unit. The variable temporal identifier TemporalId may be specified as TemporalId=nuh_temporal_id_plus1−1. The temporal identifier TemporalId is used to identify a temporal sub-layer. The variable HighestTid identifies the highest temporal sub-layer to be decoded. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                 nal_unit_header( ) { 
                 Descriptor 
               
               
                   
                   
               
             
            
               
                   
                  forbidden_zero_bit  
                 f(1)  
               
               
                   
                  nal_unit_type  
                 u(6)  
               
               
                   
                  nuh_layer_id  
                 u(6)  
               
               
                   
                  nuh_temporal_id_plus1  
                 u(3)  
               
               
                   
                 } 
               
               
                   
                   
               
               
                   
                 Table (5) 
               
            
           
         
       
     
     Table (6) shows an exemplary sequence parameter set (SPS) syntax structure. 
     pic_width_in_luma_samples specifies the width of each decoded picture in units of luma samples. pic_width_in_luma_samples shall not be equal to 0. 
     pic_height_in_luma_samples specifies the height of each decoded picture in units of luma samples. pic_height_in_luma_samples shall not be equal to 0. 
     sps_max_sub_layers_minus1 plus 1 specifies the maximum number of temporal sub-layers that may be present in each CVS referring to the SPS. The value of sps_max_sub_layers_minus1 shall be in the range of 0 to 6, inclusive. 
     sps_sub_layer_ordering_info_present_flag flag equal to 1 specifies that sps_max_dec_pic_buffering_minus1[i], sps_max_num_reorder_pics[i], and sps_max_latency_increase_plus1[i] syntax elements are present for sps_max_sub_layers_minus1+1 sub-layers. sps_sub_layer_ordering_info_present_flag equal to 0 specifies that the values of sps_max_dec_pic_buffering_minus1[sps_max_sub_layers_minus1], sps_max_num_reorder_pics[sps_max_sub_layers_minus1], and sps_max_latency_increase_plus1[sps_max_sub_layers_minus1] apply to all sub-layers. 
     sps_max_dec_pic_buffering_minus1[i] plus 1 specifies the maximum required size of the decoded picture buffer for the CVS in units of picture storage buffers when HighestTid is equal to i. The value of sps_max_dec_pic_buffering_minus1[i] shall be in the range of 0 to MaxDpbSize−1, inclusive where MaxDpbSize specifies the maximum decoded picture buffer size in units of picture storage buffers. When i is greater than 0, sps_max_dec_pic_buffering_minus1[i] shall be greater than or equal to sps_max_dec_pic_buffering_minus1[i−1]. When sps_max_dec_pic_buffering_minus1[i] is not present for i in the range of 0 to sps_max_sub_layers_minus1−1, inclusive, due to sps_sub_layer_ordering_info_present_flag being equal to 0, it is inferred to be equal to sps_max_dec_pic_buffering_minus1[sps_max_sub_layers_minus1]. 
     sps_max_num_reorder_pics[i] indicates the maximum allowed number of pictures that can precede any picture in the CVS in decoding order and follow that picture in output order when HighestTid is equal to i. The value of sps_max_num_reorder_pics[i] shall be in the range of 0 to sps_max_dec_pic_buffering_minus1[i], inclusive. When i is greater than 0, sps_max_num_reorder_pics[i] shall be greater than or equal to sps_max_num_reorder_pics[i−1]. When sps_max_num_reorder_pics[i] is not present for i in the range of 0 to sps_max_sub_layers_minus1−1, inclusive, due to sps_sub_layer_ordering_info_present_flag being equal to 0, it is inferred to be equal to sps_max_num_reorder_pics[sps_max_sub_layers_minus1]. 
     sps_max_latency_increase_plus1[i] not equal to 0 is used to compute the value of SpsMaxLatencyPictures[i], which specifies the maximum number of pictures that can precede any picture in the CVS in output order and follow that picture in decoding order when HighestTid is equal to i. 
     When sps_max_latency_increase_plus1[i] is not equal to 0, the value of SpsMaxLatencyPictures[i] is specified as follows:
 
SpsMaxLatencyPictures[ i ]=sps_max_num_reorder_pics[ i ]+sps_max_latency_increase_plus1[ i ]−1
 
     When sps_max_latency_increase_plus1[i] is equal to 0, no corresponding limit is expressed. 
     The value of sps_max_latency_increase_plus1[i] shall be in the range of 0 to 2 32 −2, inclusive. When sps_max_latency_increase_plus1[i] is not present for i in the range of 0 to sps_max_sub_layers_minus1−1, inclusive, due to sps_sub_layer_ordering_info_present_flag being equal to 0, it is inferred to be equal to sps_max_latency_increase_plus1[sps_max_sub_layers_minus1]. 
     
       
         
           
               
             
               
                 TABLE (6) 
               
               
                   
               
             
            
               
                 seq_parameter_set_rbsp0 { 
               
               
                  ... 
               
               
                 sps_max_sub_layers_minus1 
               
               
                 ... 
               
               
                 pic_width_in_luma_samples 
               
               
                 pic_height_in_luma_samples 
               
               
                 ... 
               
               
                  for( i = ( sps_sub_layer_ordering_info_present_flag ?+0 0: 
               
               
                 sps_max_sub_layers_minusi ); 
               
               
                    i &lt;= sps_max_sub_layers_minus1; i++ ) { 
               
               
                   sps_max_dec_pic_buffering_minus1[i] 
               
               
                   sps_max_num_reorder_pics[i] 
               
               
                   sps_max latency_increase_plus1[i] 
               
               
                  } 
               
               
                 ... 
               
               
                 1 
               
               
                   
               
            
           
         
       
     
     When the current picture is an IRAP picture, the following applies:
         If the current picture is an IDR picture, a BLA picture, the first picture in the bitstream in decoding order, or the first picture that follows an end of sequence NAL unit in decoding order, a variable NoRaslOutputFlag is set equal to 1.   Otherwise, if some external means is available to set a variable HandleCraAsBlaFlag to a value for the current picture, the variable HandleCraAsBlaFlag is set equal to the value provided by that external means and the variable NoRaslOutputFlag is set equal to HandleCraAsBlaFlag.   Otherwise, the variable HandleCraAsBlaFlag is set equal to 0 and the variable NoRaslOutputFlag is set equal to 0.       

     If the current picture is an IRAP picture with NoRaslOutputFlag equal to 1 that is not picture 0, the following ordered steps are applied: 
     1. The variable NoOutputOfPriorPicsFlag is derived for the decoder under test as follows:
         If the current picture is a CRA picture, NoOutputOfPriorPicsFlag is set equal to 1 (regardless of the value of no_output_of_prior_pics_flag).   Otherwise, if the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps_max_dec_pic_buffering_minus1[HighestTid] derived from the active SPS is different from the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps_max_dec_pic_buffering_minus1[HighestTid], respectively, derived from the SPS active for the preceding picture, NoOutputOfPriorPicsFlag may (but should not) be set to 1 by the decoder under test, regardless of the value of no_output_of_prior_pics_flag.   Otherwise, NoOutputOfPriorPicsFlag is set equal to no_output_of_prior_pics_flag.       

     2. The value of NoOutputOfPriorPicsFlag derived for the decoder under test is applied for the HRD as follows:
         If NoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers in the DPB are emptied without output of the pictures they contain, and the DPB fullness is set equal to 0.   Otherwise (NoOutputOfPriorPicsFlag is equal to 0), all picture storage buffers containing a picture that is marked as “not needed for output” and “unused for reference” are emptied (without output), and all non-empty picture storage buffers in the DPB are emptied by repeatedly invoking the “bumping” process  1204 , and the DPB fullness is set equal to 0.   Otherwise (the current picture is not an IRAP picture with NoRaslOutputFlag equal to 1), all picture storage buffers containing a picture which are marked as “not needed for output” and “unused for reference” are emptied (without output). For each picture storage buffer that is emptied, the DPB fullness is decremented by one. When one or more of the following conditions are true, the “bumping” process  1204  is invoked repeatedly while further decrementing the DPB fullness by one for each additional picture storage buffer that is emptied, until none of the following conditions are true:       

     1. The number of pictures with that particular nuh_layer_id value in the DPB that are marked as “needed for output” is greater than sps_max_num_reorder_pics[HighestTid] from the active sequence parameter set (when that particular nuh_layer_id value is equal to 0) or from the active layer sequence parameter set for that particular nuh_layer_id value. 
     2. If sps_max_latency_increase_plus1[HighestTid] from the active sequence parameter set (when that particular nuh_layer_id value is equal to 0) or from the active layer sequence parameter set for that particular nuh_layer_id value is not equal to 0 and there is at least one picture with that particular nuh_layer_id value in the DPB that is marked as “needed for output” for which the associated variable PicLatencyCount is greater than or equal to SpsMaxLatencyPictures[HighestTid] for that particular nuh_layer_id value. 
     3. The number of pictures with that particular nuh_layer_id value in the DPB is greater than or equal to sps_max_dec_pic_buffering[HighestTid]+1 from the active sequence parameter set (when that particular nuh_layer_id value is equal to 0) or from the active layer sequence parameter set for that particular nuh_layer_id value. 
     Picture decoding process in the block  1206  (picture decoding and marking) happens instantaneously when the last decoding unit of access unit containing the current picture is removed from the CPB. 
     For each picture with nuh_layer_id value equal to current picture&#39;s nuh_layer_id value in the DPB that is marked as “needed for output”, the associated variable PicLatencyCount is set equal to PicLatencyCount+1. 
     The current picture is considered as decoded after the last decoding unit of the picture is decoded. The current decoded picture is stored in an empty picture storage buffer in the DPB, and the following applies:
         If the current decoded picture has PicOutputFlag equal to 1, it is marked as “needed for output” and its associated variable PicLatencyCount is set equal to 0.   Otherwise (the current decoded picture has PicOutputFlag equal to 0), it is marked as “not needed for output”.       

     The current decoded picture is marked as “used for short-term reference”. 
     When one or more of the following conditions are true, the additional “bumping” process  1208  is invoked repeatedly until none of the following conditions are true:
         The number of pictures with nuh_layer_id value equal to current picture&#39;s nuh_layer_id value in the DPB that are marked as “needed for output” is greater than sps_max_num_reorder_pics[HighestTid] from the active sequence parameter set (when the current picture&#39;s nuh_layer_id value is equal to 0) or from the active layer sequence parameter set for the current picture&#39;s nuh_layer_id value.   sps_max_latency_increase_plus1[HighestTid] from the active sequence parameter set (when the current picture&#39;s nuh_layer_id value is equal to 0) or from the active layer sequence parameter set for the current picture&#39;s nuh_layer_id value is not equal to 0 and there is at least one picture with that particular nuh_layer_id value in the DPB that is marked as “needed for output” for which the associated variable PicLatencyCount is greater than or equal to SpsMaxLatencyPictures[HighestTid] for that particular nuh_layer_id value.       

     The “bumping” process  1204  and additional bumping process  1208  are identical in terms of the steps and consists of the following ordered steps: The pictures that are first for output is selected as the ones having the smallest value of picture order count (PicOrderCntVal) of all pictures in the DPB marked as “needed for output”. A picture order count is a variable that is associated with each picture, uniquely identifies the associated picture among all pictures in the CVS, and, when the associated picture is to be output from the decoded picture buffer, indicates the position of the associated picture in output order relative to the output order positions of the other pictures in the same CVS that are to be output from the decoded picture buffer.
         These pictures are cropped, using the conformance cropping window specified in the active sequence parameter set for the picture with nuh_layer_id equal to 0 or in the active layer sequence parameter set for a nuh_layer_id value equal to that of the picture, the cropped pictures are output in ascending order of nuh_layer_id, and the pictures are marked as “not needed for output”.   Each picture storage buffer that contains a picture marked as “unused for reference” and that included one of the pictures that was cropped and output is emptied.       

     Referring to  FIG.  13 A , as previously described the NAL unit header syntax may include two bytes of data, namely, 16 bits. The first bit is a “forbidden_zero_bit” which is always set to zero at the start of a NAL unit. The next six bits is a “nal_unit_type” which specifies the type of raw byte sequence payloads (“RBSP”) data structure contained in the NAL unit. The next 6 bits is a “nuh_reserved_zero_6bits”. The nuh_reserved_zero_6bits may be equal to 0 in the base specification of the standard. Other values of nuh_reserved_zero_6bits may be specified as desired. Decoders may ignore (i.e., remove from the bitstream and discard) all NAL units with values of nuh_reserved_zero_6bits not equal to 0 when handling a stream based on the base specification of the standard. In a scalable or other extension nuh_reserved_zero_6bits may specify other values, to signal scalable video coding and/or syntax extensions. In some cases syntax element nuh_reserved_zero_6bits may be called reserved_zero_6bits. In some cases the syntax element nuh_reserved_zero_6bits may be called as layer_id_plus1 or layer_id, as illustrated in  FIG.  13 B  and  FIG.  13 C . In this case the element layer_id will be layer_id_plus1 minus 1. In this case it may be used to signal information related to layer of scalable coded video. The next syntax element is “nuh_temporal_id_plus1”. nuh_temporal_id_plus1 minus 1 may specify a temporal identifier for the NAL unit. The variable temporal identifier TemporalId may be specified as TemporalId=nuh_temporal_id_plus1−1. 
     Referring to  FIG.  14   , a general NAL unit syntax structure is illustrated. The NAL unit header two byte syntax of  FIG.  13    is included in the reference to nal_unit_header( ) of  FIG.  14   . The remainder of the NAL unit syntax primarily relates to the RBSP. 
     One existing technique for using the “nuh_reserved_zero_6bits” is to signal scalable video coding information by partitioning the 6 bits of the nuh_reserved_zero_6bits into distinct bit fields, namely, one or more of a dependency ID, a quality ID, a view ID, and a depth flag, each of which refers to the identification of a different layer of the scalable coded video. Accordingly, the 6 bits indicate what layer of the scalable encoding technique this particular NAL unit belongs to. Then in a data payload, such as a video parameter set (“VPS”) extension syntax (“scalability_type”) as illustrated in  FIG.  15   , the information about the layer is defined. The VPS extension syntax of  FIG.  15    includes 4 bits for scalability type (syntax element scalability_type) which specifies the scalability types in use in the coded video sequence and the dimensions signaled through layer_id_plus1 (or layer_id) in the NAL unit header. When the scalability type is equal to 0, the coded video sequence conforms to the base specification, thus layer_id_plus1 of all NAL units is equal to 0 and there are no NAL units belonging to an enhancement layer or view. Higher values of the scalability type are interpreted as illustrated in  FIG.  16   . 
     The layer_id_dim_len[i] specifies the length, in bits, of the i-th scalability dimension ID. The sum of the values layer_id_dim_len[i] for all i values in the range of 0 to 7 is less than or equal to 6. The vps_extension_byte_alignment_reserved_zero_bit is zero. The vps_layer_id[i] specifies the value of layer_id of the i-th layer to which the following layer dependency information applies. The num_direct_ref_layers[i] specifies the number of layers the i-th layer directly depends on. The ref_layer_id[i][j] identifies the j-th layer the i-th layer directly depends on. 
     In this manner, the existing technique signals the scalability identifiers in the NAL unit and in the video parameter set to allocate the bits among the scalability types listed in  FIG.  16   . Then for each scalability type,  FIG.  16    defines how many dimensions are supported. For example, scalability type 1 has 2 dimensions (i.e., spatial and quality). For each of the dimensions, the layer_id_dim_len[i] defines the number of bits allocated to each of these two dimensions, where the total sum of all the values of layer_id_dim_len[i] is less than or equal to 6, which is the number of bits in the nuh_reserved_zero_6bits of the NAL unit header. Thus, in combination the technique identifies which types of scalability is in use and how the 6 bits of the NAL unit header are allocated among the scalability. 
     While such a fixed combination of different scalability dimensions, as illustrated in  FIG.  16   , is suitable for many applications there are desirable combinations which are not included. Referring to  FIG.  17   , a modified video parameter set extension syntax specifies a scalability type for each bit in the nuh_reserved_zero_6bits syntax element. The vps_extension_byte_alignment_reserved_zero_bit is set to 0. The max_num_layers_minus1_bits indicates the total number of bits used for the syntax element in the first two bytes of the NAL unit header in  FIG.  13    referred to as layer_id_plus1 or nuh_reserved_zero_6bits. The scalability_map[i] specifies the scalability type for each bit in the layer_id_plus1 syntax element. In some case the layer_id_plus1 syntax element may be instead called nuh_reserved_zero_6bits or rserved_zero_6bits syntax element. The scalability map for all the bits of the syntax element layer_id_plus1 together specifies the scalability in use in the coded video sequence. The actual value of the identifier for each of the scalability types is signaled through those corresponding bits in the layer_id_plus1 (nuh_reserved_zero_6bits) field in the NAL unit header. When scalability_map[i] is equal to 0 for all values of i, the coded video sequence conforms to the base specification, thus layer_id_plus1 value of NAL units is equal to 0 and there are no NAL units belonging to an enhancement layer or view. The vps_layer_id[i] specifies the value of layer_id of the i-th layer to which the following layer dependency information applies. The num_direct_ref_layers[i] specifies the number of layers the i-th layer directly depends on. The ref_layer_id[i][j ] identifies the j-th layer the i-th layer directly depends on. 
     Higher values of scalability_map[i] are interpreted as shown in  FIG.  18   . The scalability map [i] includes the scalability dimensions of (0) none; (1) spatial; (2) quality; (3) depth; (4) multiview; (5) unspecified; (6) reserved; and (7) reserved. 
     Therefore each bit in the NAL unit header is interpreted based on the 3 bits in the video parameter set of what is the scalability dimension (e.g., none, spatial, quality, depth, multiview, unspecified, reserved). For example, to signal that all the bits in layer_id_plus1 correspond to spatial scalability, the scalability_map values in the VPS may be coded as 001 001 001 001 001 001 for the 6 bits of the NAL unit header. Also for example, to signal that 3 bits in layer_id_plus1 correspond to spatial scalability and 3 bits correspond to quality scalability, the scalability_map values in the VPS may be coded as 001 001 001 010 010 010 for the 6 bits of the NAL Unit header. 
     Referring to  FIG.  19   , another embodiment includes the video parameter set signaling the number of scalability dimensions in the 6 bits of the NAL unit header using the num_scalability_dimensions_minus1. The num_scalability_dimensions_minus1 plus 1 indicates the number of scalability dimensions signaled through the layer_id_plus1; nuh_reserved_zero_6bits; and/or reserved_zero_6bits syntax elements. The scalability_map[i] has the same semantics as described above in relation to  FIG.  17   . The num_bits_for_scalability_map[i] specifies the length in bits for the I&#39;th scalability dimension. The sum of all of the num_bits_for_scalability_map[i] for i=0, . . . num_scalability_dimensions_minus1 is equal to six (or otherwise equal to the number of bits used for layer_id_plus1; vps_reserved_zero_6bits; max_num_layers_minus1; reserved_zero_6bits; nuh_reserved_zero_6bits syntax elements). 
     With respect to  FIG.  17    and  FIG.  19    other variations may be used, if desired. In one embodiment for example, the scalability_map[i] may be signaled with u(4) (or u(n) with n&gt;3 or n&lt;3). In this case the higher values of scalability_map[i] may be specified as reserved for bitstreams conforming to a particular profile of the video technique. For example, scalability map values 6 . . . 15 may be specified as ‘reserved’ when signaling scalability_map[i] with u(4). In another embodiment for example, scalability_map[i] maybe signaled with ue(v) or some other coding scheme. In another embodiment for example, a restriction may be specified such that the scalability_map[i] values are arranged in monotonic non decreasing (or non-increasing) order. This results in various scalability dimension fields in the layer_id_plus1 field in NAL unit header being contiguous. 
     Another existing technique for signaling the scalable video coding using the “layer_id_plus1” or “nuh_reserved_zero_6bits” syntax element is to map the layer_id_plus1 in the NAL unit header to a layer identification by signaling a general lookup table in the video parameter set. Referring to  FIG.  20   , the existing technique includes a video parameter set that specifies the number of dimension types and dimension identifications for the i-th layer of the lookup table. In particular, the vps_extension_byte_alignment_reserved_zero_bit is zero. The num_dimensions_minus1 [i] plus 1 specifies the number of dimension types (dimension_type[i][j]) and dimension identifiers (dimension_id[i][j]) for the i-th layer. The dimension_type[i][j] specifies the j-th scalability dimension type of the i-th layer, which has layer_id or layer_id_plus1 equal to i, as specified in  FIG.  31   . As illustrated in  FIG.  21   , the dimensions that are identified include of (0) view order idx; (1) depth flag; (2) dependency ID; (3) quality ID; (4)-(15) reserved. The dimension_id[i][j] specifies the identifier of the j-th scalability dimension type of the i-th layer, which when not present is inferred to be 0. The num_direct_ref_layers[i] specifies the number of layers the i-th layer directly depends on. The ref_layer_id[i][j] identifies the j-th layer the i-th layer directly depends on. Unfortunately, the proposed embodiment illustrated in  FIG.  20    results in an unwieldy large lookup table. 
     Referring to  FIG.  22   , a modified video parameter set extension includes a scalability mask that is used in combination with a scalability dimension. The scalability_mask signals a pattern of 0 and 1 bits with each bit corresponding to one scalability dimension as indicated by the scalability map syntax of  FIG.  23   . A value of 1 for a particular scalability dimension indicates that this scalability dimension is present in this layer (I&#39;th layer). A value of 0 for a particular scalability dimension indicates that this scalability dimension is not present in this layer (I&#39;th layer). For example, a set of bits of 00100000 refers to quality scalability. The actual identifier value of the particular scalability dimension that is present is indicated by the scalability_id[j] value signaled. The values of num_scalability_types[i] is equal to the sum of number of bits in the scalability_mask having value of 1. Thus 
     
       
         
           
             
               
                 
                   
                     num 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     _ 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     scalability 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     _ 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       types 
                       ⁢ 
                       
                           
                       
                       [ 
                       i 
                       ] 
                     
                   
                   = 
                   
                     
                       ∑ 
                       
                         k 
                         = 
                         0 
                       
                       7 
                     
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       scalability 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       _ 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                         mask 
                         ⁢ 
                         
                             
                         
                         [ 
                         i 
                         ] 
                       
                       ⁢ 
                       
                         ( 
                         k 
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Math 
                     . 
                     
                         
                     
                     ⁢ 
                     9 
                   
                   ] 
                 
               
             
           
         
       
     
     The scalability_id[j] indicates the j-th scalability dimension&#39;s identifier value for the type of scalability values that are signaled by the scalability_mask value. 
     Referring to  FIG.  24   , a modification of  FIG.  22   , includes the scalability mask being signaled outside the loop. This results in one common mask for each layer identification. Referring to  FIG.  25   , in this modification a corresponding exemplary video parameter set may include the scalable identification with the scalability mask not being included. In this case the syntax element scalable_id[j] has same interpretation as the syntax element scalability_id[j] in  FIG.  22   . 
     Referring to  FIG.  26    a modification of  FIG.  22    includes the scalability mask (scalability_mask) being signaled outside the loop. This results in one common mask for each layer identification. The scalability_mask signals a pattern of 0 and 1 bits with each bit corresponding to one scalability dimension as indicated by the scalability map syntax of  FIG.  27   . A value of 1 for a particular scalability dimension indicates that this scalability dimension is present in this layer (i&#39;th layer). A value of 0 for a particular scalability dimension indicates that this scalability dimension is not present in this layer (i&#39;th layer). For example, a set of bits of 00100000 refers to quality scalability. The actual identifier value of the particular scalability dimension that is present is indicated by the scalability_id[j] value signaled. The values of num_scalability_types[i] is equal to the sum of number of bits in the scalability_mask having value of 1. Thus 
     
       
         
           
             
               
                 
                   
                     NumScalabilityTypes 
                     ⁡ 
                     
                       [ 
                       i 
                       ] 
                     
                   
                   = 
                   
                     
                       ∑ 
                       
                         k 
                         = 
                         0 
                       
                       
                         1 
                         ⁢ 
                         5 
                       
                     
                     ⁢ 
                     
                       scalability 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       _ 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       mask 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                         ( 
                         k 
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Math 
                     . 
                     
                         
                     
                     ⁢ 
                     10 
                   
                   ] 
                 
               
             
           
         
       
     
     In this case the scalability_id[j] variable may instead be called dimension_id[i][j] variable. dimension_id[i][j] specifies the scalability identifier of the j-th scalability dimension of the i-th layer. Then a variable ScalabilityId[i][j] is derived as follows. 
     
       
         
           
               
             
               
                 TABLE 7 
               
               
                   
               
             
            
               
                 for( i = 1; i &lt;= vps_max_layers_minus1; i++ ) { 
               
               
                  for(k=0, j=0; k&lt;=15; k++) { 
               
               
                   if(scalability_mask(k)==1) 
               
               
                    ScalabilityId [i][k]=dimension_id[i][j++] 
               
               
                   else 
               
               
                   ScalabilityId [i][k]=0; 
               
               
                  } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     Where the ScalabilityId [i][k] signals dimension ID for the corresponding scalability type as follows. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 8 
               
               
                   
                   
               
             
            
               
                   
                 k  
                 ScalabilityId [i][k] 
               
               
                   
                 0  
                 DependencyId[i][k] 
               
               
                   
                 1  
                 QualityId[il[k] 
               
               
                   
                 2  
                 depthFlag[i][k] 
               
               
                   
                 3  
                 ViewId[i][k] 
               
               
                   
                 4-15  
                 Reserved 
               
               
                   
                   
               
            
           
         
       
     
     Where DependencyId[i][1] is the dependency ID for the spatial scalability dimension for the i-th layer, QualityId[i][2] is the quality ID for the quality scalability dimension for the i-th layer, depthFlag[i][3] is the depth flag/depth ID for the depth scalability dimension for the i-th layer, and ViewId[i][4] is the view ID for the multiview scalability dimension for the i-th layer. 
     Also in  FIG.  26    avc_base_codec_flag equal to 1 specifies that the base layer conforms to Rec. ITU-T H.264 I ISO/IEC 14496-10, and avc_base_codec_flag equal to 1 specifies to HEVC. vps_nuh_layer_id_presnet_flag indicates if layer_id_in_nuh[i] variable which signals the value of layer_id in NAL unit header is signaled. 
     In another embodiment one or more of the syntax elements scalability_mask[i], scalability_mask, scalability_id[j] may be signaled using different number of bits than u(8). For example they could be signaled with u(16) (or u(n) with n&gt;8 or n&lt;8). In another embodiment one or more of these syntax element could be signaled with ue(v). In another embodiment the scalability_mask may be signaled in the NAL unit header in layer_id_plus1; vps_reserved_zero_6bits; max_num_layers_minus1; reserved_zero_6bits; and/or nuh_reserved_zero_6bits syntax elements. In some embodiments the system may do this only for VPS NAL units, or only for non-VPS NAL units, or for all NAL units. In yet another embodiment scalability_mask may be signaled per picture anywhere in the bitstream. For example it may be signaled in slice header, picture parameter set, video parameter set, or any other parameter set or any other normative part of the bitstream. 
     It should be noted that  FIGS.  13 ,  15 ,  18 ,  20 ,  21 ,  22 ,  23    and corresponding description refer to 6 bits since the syntax element nuh_reserved_zero_6bits or layer_id_plus1 in NAL unit header of  FIG.  13    has 6 bits. However all the above description can be suitably modified if that syntax element used a different number of bits than 6 bits. For example if that syntax element (nuh_reserved_zero_6bits or layer_id_plus1) instead used 9 bits then in  FIG.  17    the value of max_num_layer_minus1 bits will be 9 and the scalability_map[i] will be signaled for each of the 9 bits instead of 6 bits. 
     Referring to  FIG.  24    a modification of  FIG.  22    provides syntax for signaling layer dependency information. New syntax element layer_dependency_information_pattern is defined. 
     layer_dependency_information_pattern signals a pattern of 0 and 1 bits with the length equal to vps_max_layers_minus1. A value of 0 for i&#39;th bit indicates that the layer with layer_id (i+1) is an independent layer. A value of 1 for i&#39;th bit indicates that the layer with layer_id (i+1) is a dependent layer which depends on one or more of other layers. 
     The values of NumDepLayers is equal to the sum of number of bits in the layer_dependency_information_pattern having value of 1. Thus 
     
       
         
           
             
               
                 
                   NumDepLayers 
                   = 
                   
                       
                     
                       
                         ∑ 
                         
                           k 
                           = 
                           0 
                         
                         
                           
                             vps 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             max 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             layer 
                             ⁢ 
                             
                                 
                             
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                             _ 
                             ⁢ 
                             
                                 
                             
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                             ⁢ 
                             
                                 
                             
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                             1 
                           
                           - 
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                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                           
                         
                             
                           
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                             ⁢ 
                             
                                 
                             
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                             ⁢ 
                             
                                 
                             
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                             _ 
                             ⁢ 
                             
                                 
                             
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                             ⁢ 
                             
                                 
                             
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                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             pattern 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               ( 
                               k 
                               ) 
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Math 
                     . 
                     
                         
                     
                     ⁢ 
                     11 
                   
                   ] 
                 
               
             
           
         
       
     
     Referring to  FIG.  29    a modification of  FIG.  26    provides syntax for signaling layer dependency information. New syntax element layer_dependency_flag[i] is defined. layer_dependency_flag[i] signals if a layer depends on other layers. A value of 0 for the flag indicates that the layer with layer_id i is an independent layer. A value of 1 for i&#39;th bit indicates that the layer with layer_id i is a dependent layer. 
     Referring to  FIG.  30    a modification of  FIG.  26    provides syntax for signaling layer dependency information. New syntax element layer_dependency_map[i] is defined. layer_dependency_map[i] signals a pattern of 0 and 1 bits with the length equal to vps_max_layers_minus1. A value of 0 for k&#39;th bit of layer_dependency_map[i] indicates that the layer i does not depend on layer with layer_id (k+1). A value of 1 for k&#39;th bit of layer_dependency_map[i] indicates that the layer i depends on layer with layer_id (k+1). 
     Referring to  FIG.  31    a modification of  FIG.  26    provides syntax for signaling layer dependency information. New syntax element layer_dependency_information_pattern is defined. 
     layer_dependency_information_pattern signals a pattern of 0 and 1 bits with the length equal to vps_max_layers_minus1. A value of 0 for i&#39;th bit indicates that the layer with layer_id (i+1) is an independent layer. A value of 1 for i&#39;th bit indicates that the layer with layer_id (i+1) is a dependent layer which depends on one or more of other layers. The values of NumDepLayers is equal to the sum of number of bits in the layer_dependency_information_pattern having value of 1. Thus 
     
       
         
           
             
               
                 
                   NumDepLayers 
                   = 
                   
                       
                     
                       
                         ∑ 
                         
                           k 
                           = 
                           0 
                         
                         
                           
                             vps 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             max 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             layer 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             minus 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                           
                           - 
                           1 
                         
                       
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                           
                         
                             
                           
                             layer 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             dependency 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             information 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
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                             ⁢ 
                             
                                 
                             
                             ⁢ 
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                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               ( 
                               k 
                               ) 
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Math 
                     . 
                     
                         
                     
                     ⁢ 
                     12 
                   
                   ] 
                 
               
             
           
         
       
     
     layer_dependency_map[i] signals a pattern of 0 and 1 bits with the length equal to vps_max_layers_minus1. A value of 0 for k&#39;th bit of layer_dependency_map[i] indicates that the layer i does not depend on layer with layer_id (k+1). A value of 1 for k&#39;th bit of layer_dependency_map[i] indicates that the layer i depends on layer with layer_id (k+1). 
     Referring to  FIG.  32    a modification of  FIG.  26    provides syntax for signaling layer dependency information.  FIG.  28    is a variant syntax based on syntax in  FIG.  27   . New syntax element layer_dependency_information_pattern is defined. 
     layer_dependency_information_pattern signals a pattern of 0 and 1 bits with the length equal to vps_max_layers_minus1. A value of 0 for i&#39;th bit indicates that the layer with layer_id (i+1) is an independent layer. A value of 1 for i&#39;th bit indicates that the layer with layer_id (i+1) is a dependent layer which depends on one or more of other layers. 
     The values of NumDepLayers is equal to the sum of number of bits in the layer_dependency_information_pattern having value of 1. Thus 
     
       
         
           
             
               
                 
                   NumDepLayers 
                   = 
                   
                       
                     
                       
                         ∑ 
                         
                           k 
                           = 
                           0 
                         
                         
                           
                             vps 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
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                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
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                             ⁢ 
                             
                                 
                             
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                             ⁢ 
                             
                                 
                             
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                           - 
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                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                           
                         
                             
                           
                             layer 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
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                             ⁢ 
                             
                                 
                             
                             ⁢ 
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                             ⁢ 
                             
                                 
                             
                             ⁢ 
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                             ⁢ 
                             
                                 
                             
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                             ⁢ 
                             
                               ( 
                               k 
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                   [ 
                   
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                     . 
                     
                         
                     
                     ⁢ 
                     13 
                   
                   ] 
                 
               
             
           
         
       
     
     Syntax elements num_direct_ref_layers[i] and ref_layer_id[i][j] are signaled only when layer_dependency_information_pattern(i) has a value of 1. Where layer_dependency_information_pattern(i) is the i&#39;th bit of the syntax element layer_dependency_pattern. 
     Referring to  FIG.  33    a modification of  FIG.  26    provides syntax for signaling layer dependency information.  FIG.  29    is a variant syntax based on syntax in  FIG.  31   . New syntax element layer_dependency_information_pattern is defined. 
     layer_dependency_information_pattern signals a pattern of 0 and 1 bits with the length equal to vps_max_layers_minus1. A value of 0 for i&#39;th bit indicates that the layer with layer_id (i+1) is an independent layer. A value of 1 for i&#39;th bit indicates that the layer with layer_id (i+1) is a dependent layer which depends on one or more of other layers. 
     The values of NumDepLayers is equal to the sum of number of bits in the layer_dependency_information_pattern having value of 1. Thus 
     
       
         
           
             
               
                 
                   NumDepLayers 
                   = 
                   
                       
                     
                       
                         ∑ 
                         
                           k 
                           = 
                           0 
                         
                         
                           
                             vps 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             max 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             layer 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             minus 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                           
                           - 
                           1 
                         
                       
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                           
                         
                             
                           
                             layer 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             dependency 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             information 
                             ⁢ 
                             
                                 
                             
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                             _ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             pattern 
                             ⁢ 
                             
                                 
                             
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                               ( 
                               k 
                               ) 
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Math 
                     . 
                     
                         
                     
                     ⁢ 
                     14 
                   
                   ] 
                 
               
             
           
         
       
     
     layer_dependency_map[i] signals a pattern of 0 and 1 bits with the length equal to vps_max_layers_minus1. A value of 0 for k&#39;th bit of layer_dependency_map[i] indicates that the layer i does not depend on layer with layer_id (k+1). A value of 1 for k&#39;th bit of layer_dependency_map[i] indicates that the layer i depends on layer with layer_id (k+1). Syntax elements layer_dependency_map[i] is signaled only when layer_dependency_information_pattern(i) has a value of 1. Where layer_dependency_information_pattern(i) is the i&#39;th bit of the syntax element layer_dependency_pattern. 
     In another embodiment layer_dependency_information_pattern syntax element may be signaled as a set of 1 bit flag values. In this case a total of vps_max_layers_minus1 1 bit values will be signaled as: 
     
       
         
           
               
             
               
                 TABLE 9 
               
               
                   
               
             
            
               
                 for( i = 1; i &lt;= vps_max_layers_minus1 ; i++ ) 
               
               
                 { 
               
               
                  layer_dependency_information_pattern_flags[i]; 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     In another embodiment layer_dependency_map[i] syntax element may be signaled as a set of 1 bit flag values. In this case a total of vps_max_layers_minus1 1 bit values will be signaled as: 
     
       
         
           
               
             
               
                 TABLE 10 
               
               
                   
               
             
            
               
                 for( j = 1; j&lt;= vps_max_layers_minus1 ; j++ ) 
               
               
                 { 
               
               
                  layer_dependency_map_values[i][j]; 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     In another embodiment one or more of the syntax elements layer_dependency_information_pattern, layer_dependency_map may be signaled using a known fixed number of bits instead of u(v). For example they could be signaled using u(64). 
     In another embodiment one or more of or more of the syntax elements layer_dependency_information_pattern, layer_dependency_map may be signaled with ue(v) or some other coding scheme. 
     In another embodiment the names of various syntax elements and their semantics may be altered by adding a plus1 or plus2 or by subtracting a minus1 or a minus2 compared to the described syntax and semantics. 
     In yet another embodiment various syntax elements such as layer_dependency_information_pattern, layer_dependency_map, layer_dependency_flag[i] etc. may be signaled per picture anywhere in the bitstream. For example it may be signaled in slice header, pps/sps/vps/aps or any other parameter set or other normative part of the bitstream. 
     As previously described, scalable video coding is a technique of encoding a video bitstream that also contains one or more subset bitstreams. A subset video bitstream may be derived by dropping packets from the larger video to reduce the bandwidth required for the subset bitstream. The subset bitstream may represent a lower spatial resolution (smaller screen), lower temporal resolution (lower frame rate), or lower quality video signal. For example, a video bitstream may include 5 subset bitstreams, where each of the subset bitstreams adds additional content to a base bitstream. Hannuksela, et al., “Test Model for Scalable Extensions of High Efficiency Video Coding (HEVC)” JCTVC-L0453, Shanghai, October 2012, is hereby incorporated by reference herein in its entirety. Chen, et al., “SHVC Draft Text 1,” JCTVC-L1008, Geneva, March, 2013, is hereby incorporated by reference herein in its entirety. Wang, et al., “AHG9: On VPS and SPS in HEVC 3DV and scalable extensions,” JCTVC-M0268, Incheon, April 2013 is herby incorporated by reference herein in its entirety. 
     As previously described, multi-view video coding is a technique of encoding a video bitstream that also contains one or more other bitstreams representative of alternative views. For example, the multiple views may be a pair of views for stereoscopic video. For example, the multiple views may represent multiple views of the same scene from different viewpoints. The multiple views generally contain a large amount of inter-view statistical dependencies, since the images are of the same scene from different viewpoints. Therefore, combined temporal and inter-view prediction may achieve efficient multi-view encoding. For example, a frame may be efficiently predicted not only from temporally related frames, but also from the frames of neighboring viewpoints. Hannuksela, et al., “Common specification text for scalable and multiview extensions,” JCTVC-L0452, Geneva, January 2013, is hereby incorporated by reference herein in its entirety. Tech, et. al. “MV-HEVC Draft Text 3 (ISO/IEC 23008-2:201x/PDAM2),” JCT3V-C1004_d3, Geneva, January 2013, is hereby incorporated by reference herein in its entirety. 
     Chen, et al., “SHVC Draft Text 1,” JCTVC-L1008, Geneva, January 2013; Hannuksela, et al. “Test Model for Scalable Extensions of High Efficiency Video Coding (HEVC),” JCTVC-L0453-spec-text, Shanghai, October 2012; and Hannuksela, “Draft Text for Multiview Extension of High Efficiency Video Coding (HEVC),” JCTVC-L0452-spec-text-r1, Shanghai, October 2012; each of which is incorporated by reference herein in its entirety.JCTVC-L0452 and JCTVC-L0453 each have the concept of output operation points. This was later changed to the concept of output layer sets in JCTVC-L1008. For the syntax elements num_output_operation_points, output_op_point_index[ ], and output_layer_flag[ ][ ] are defined for the output operation points for JCTVC-L0453 and LCTVC-L0452, and modified to num_output_layer_sets, output_layer_set_idx[ ], and output_layer_flag[ ][ ] in JCTVC-L1008. In each of such documents, a layer dependency change SEI message is defined. The SEI message allows signaling layer dependency information changes starting with the current access unit containing the SEI message. 
     Chen, et al., “SHVC Draft Text 1,” JCTVC-L1008, Geneva, January 2013; Hannuksela, et al. “Test Model for Scalable Extensions of High Efficiency Video Coding (HEVC),” JCTVC-L0453-spec-text, Shanghai, October 2012; and Hannuksela, “Draft Text for Multiview Extension of High Efficiency Video Coding (HEVC),” JCTVC-L0452-spec-text-r1, Shanghai, October 2012; each of which is incorporated by reference herein in its entirety, each have an output order decoded picture buffer (DPB) which operates based on using sps_max_num_reorder_pics[HighestTid], sps_max_latency_increase_plus1[HighestTid] and sps_max_dec_pic_buffering[HighestTid] syntax elements for the output and removal of pictures 0 from the DPB. This information is signaled in the video parameter set for the base layer, which provides buffering information for the video content including the enhancement layers, if any. 
     Referring to  FIG.  34   , another example of a video parameter set is illustrated. In particular, the video parameter set of  FIG.  34    includes reference to an associated video parameter set extension (vps_extension). The vps_extension may be signaled with the vps_extension_flag, the vps_extension2_flag, and/or the vps_extension_data_flag. 
     Referring to  FIG.  35   , another example of a video parameter set extension is illustrated. In particular, the video parameter set extension of  FIG.  35    includes reference to num_output_layer_sets, which defines those layers of a set of layers of a bitstream that may be output to the viewer by the decoder. num_output_layer_sets specifies the number of layer sets for which output layers are specified with output_layer_set_index[i] and output_layer_flag[lsIdx][j]. When not present, the value of num_output_layer_sets is inferred to be equal to 0. A layer set describing output layers is an output layer set. 
     The output_layer_set_idx[i] specifies the index lsIdx of the layer set for which output_layer_flag[lsIdx][j] is present. 
     The output_layer_flag[lsIdx][j] equal to 1 specifies that the layer with nuh_layer_id equal to j is a target output layer of the lsIdx-th layer set. A value of output_layer_flag[lsIdx][j] equal to 0 specifies that the layer with nuh_layer_id equal to j is not a target output layer of the lsIdx-th layer set. 
     With the num_output_layer_sets being defined in the vps_extension in the manner described, the num_output_layer_sets may be updated by sending a new video parameter set together with a corresponding video parameter set extension. Unfortunately, sending the new video parameter set together with the corresponding video parameter set extension results in a significant reduction in the available bandwidth. Additionally a new video parameter set could only be activated at certain picture types, for example at Intra random access point picture types. 
     As an example, a bitstream may include a base layer 0 and four enhancement layers, namely enhancement layer 1, enhancement layer 2, enhancement layer 3, and enhancement layer 4. A first layer set may be base layer 0 and enhancement layer 1. A second layer set may be base layer 0, enhancement layer 1, and enhancement layer 2. A third layer set may be base layer 0, enhancement layer 1, and enhancement layer 3. A fourth layer set may be base layer 0 and enhancement layer 4. The output layer sets define the particular layers of a layer set that may be provided as an output. For example, output layer set 1 may be layer 0 is an output and layer 1 is not an output. For example, output layer set 2 may be layer 0 is an output, layer 1 is an output, and layer 2 is not output. For example, output layer set 3 may be layer 0 is not output, layer 1 is not output, and layer 3 is output. For example, output layer set 4 may be layer 0 is output and layer 4 is not output. A limited number of output layers is useful to accommodate limited decoding capabilities. In some cases, it is desirable to disable some dependencies between different layers to accommodate decoding other layers and/or decoder capabilities. When some layer dependencies change it may likewise be desirable to enable, disable, and/or add other layers as output layers. As an example layer dependency change could require fewer layers to be decoded to decode a particular target layer (e.g. a view in MV-HEVC). Thus a decoder could decode and output a layer (e.g. and additional view) after a layer dependency change that it previously could not due to its hardware limitation. Currently no mechanism exists to allow signaling a change in the output layer sets without sending a new video parameter set. 
     Referring to  FIG.  36   , a SEI message syntax may be used to facilitate changes of the output layer sets, namely, output_layer_sets_change(payloadSize). This SEI message indicates that the output layer sets information changes starting with the current access unit containing the SEI message and is interpreted with respect to the active video parameter set. More than one video parameter set may be included with the bitstream, and the active video parameter set is changed, as desired. When present, the output layer sets change SEI message applies to the target access unit set that consists of the current access unit and all the subsequent access units, in decoding order, until the next output layer sets change SEI message or the end of the coded video sequence, whichever is earlier in decoding order. Output layer sets change SEI messages preferably do not have a cumulative effect. 
     The ‘active_vps_id’ identifies an active video parameter set that contains the output layer sets information to which the change or addition applied. The value of active_vps_id is equal to the value of video_parameter_set_id of the active video parameter set for the VCL NAL units of the access unit containing the SEI message. 
     The ‘num_changed_output_layer_sets’ specifies the number of changed output layer sets for which output layers are specified in vps extension section of the active video parameter set identified by active_vps_id. The value of num_changed_output_layer_sets should be in the range of 0 to num_output_layer_sets, inclusive. When not present, the value of num_changed_output_layer_sets is inferred to be equal to 0. 
     The ‘changed_output_layer_sets_idx_entry’[i] identifies the index entry in the list of output layer set entries in the vps extension identified by active_vps_id for which output_layer_flag[clsIdx][j] change applies to. The value of changed_output_layer_set_idx_entry[i] should be in the range of 0 to num_output_layer_sets, inclusive. The changed_output_layer_sets_idx_entry[i] is not equal to changed_output_layer_sets_idx_entry[j] for any j not equal to i. 
     The ‘output_layer_flag’[clsIdx][j] equal to 1 specifies that the layer with nuh_layer_id equal to j is a target output layer of the clsIdx-th layer set. A value of output_layer_flag[clsIdx][j] equal to 0 specifies that the layer with nuh_layer_id equal to j is not a target output layer of the clsIdx-th layer set. 
     When output_layer_flag[clsIdx][j] is not present for clsIdx in the range of 0 to vps_num_layer_sets_minus1, inclusive and for j in the range of 0 to 63, inclusive, output_layer_flag[clsIdx][j] is inferred to be equal to (j==LayerSetLayerIdList[clsIdx][NumLayersInIdList[clsIdx]−1]). 
     The ‘num_addl_output_layer_sets’ specifies the number of additional layer sets for which output layers are specified with addl_output_layer_set_idx[i] and output_layer_flag[addllsIdx][j]. When not present, the value of num_addl_output_layer_sets is inferred to be equal to 0. The ‘addl_output_layer_sets_idx’[i] identifies the index addllsIdx of the layer set for which output_layer_flag[addllsIdx][j] is present. 
     The ‘output_layer_flag’[addllsIdx][j] equal to 1 specifies that the layer with nuh_layer_id equal to j is a target output layer of the addllsIdx-th layer set. A value of output_layer_flag[addllsIdx][j] equal to 0 specifies that the layer with nuh_layer_id equal to j is not a target output layer of the addllsIdx-th layer set. 
     When output_layer_flag[addllsIdx][j] is not present for addllsIdx in the range of 0 to vps_num_layer_sets_minus1, inclusive and for j in the range of 0 to 63, inclusive, output_layer_flag[addllsIdx][j] is inferred to be equal to (j==LayerSetLayerIdList[addllsIdx][NumLayersInIdList[addllsIdx]−1]). 
     When output_layer_flag[addllsIdx][j] is not present for addllsIdx in the range of 0 to vps_num_layer_sets_minus1, inclusive and for j in the range of 0 to 63, inclusive, and when output_layer_flag[clsIdx][j] is not present for clsIdx in the range of 0 to vps_num_layer_sets_minus1, inclusive and for j in the range of 0 to 63, inclusive, output_layer_flag[addllsIdx][j] is inferred to be equal to (j==LayerSetLayerIdList[addllsIdx][NumLayersInIdList[addllsIdx]−1]). 
     When output_layer_flag[addllsIdx][j] is not present for addllsIdx in the range of 0 to vps_num_layer_sets_minus1, inclusive and for j in the range of 0 to 63, inclusive, and when output_layer_flag[clsIdx][i] is not present for clsIdx in the range of 0 to vps_num_layer_sets_minus1, inclusive and for j in the range of 0 to 63, inclusive, output_layer_flag[clsIdx][j] is inferred to be equal to (j==LayerSetLayerIdList[clsIdx][NumLayersInIdList[clsIdx]−1]). 
     A target list of output layers may be derived, if desired. The target output layer identifier list, targetOpLayerIdList, specifies the list of nuh_layer_id values, in increasing order of nuh_layer_id values which are output layers for the selected output layer set may be derived as follows: 
     For a selected output layer set oLsIdx, a target output layer identifier list targetOpLayerIdList is derived as: 
     
       
         
           
               
             
               
                 TABLE 11 
               
               
                   
               
             
            
               
                 for(k=0, numOutputLayers=0;k&lt;=vps_max_layer_id;k++) 
               
               
                 if(output_layer_flag[oLsIdx][k]) 
               
               
                  targetOpLayerIdList[numOutputLayers++]=layer_id_in_nuh[k] 
               
               
                   
               
            
           
         
       
     
     A target output layer set may be identified by the associated target output layer identifier list targetOpLayerIdList. 
     The selected output layer set oLsIdx is between 0 and num_output_layer_sets if there are no output layer sets change SEI messages. 
     The selected output layer set oLsIdx is between 0 and num_output_layer_sets+num_addl_output_layer_sets if there are output layer sets change SEI messages present. 
     A target list of decoded layers may be derived, if desired. The target decoded layer identifier list, targetDLayerIdList, specifies the list of nuh_layer_id values, which need to be decoded for the selected output layer set may be derived as follows: 
     For a selected output layer set oLsIdx, a target output layer identifier list targetOpLayerIdList is derived as: 
     
       
         
           
               
             
               
                 TABLE 12 
               
               
                   
               
             
            
               
                 for(k=0, numOutputLayers=0;k&lt;=vps_max_layer_id;k++) 
               
               
                 if(output_layer_flag[oLsIdx][k]) 
               
               
                  targetOpLayerIdList [numOutputLayers++]=layer_id_in_nuh[k] 
               
               
                   
               
            
           
         
       
     
     A target decoded layer identifier list targetDLayerIdList may be derived as: 
     
       
         
           
               
             
               
                 TABLE 13 
               
               
                   
               
             
            
               
                 for(m=0, numDecodedLayers=0;m&lt; numOutputLayers;m++) { 
               
               
                  for(n=0;n&lt;NumDirectRefLayers+LayerIdInVps+targetOpLayerIdList[m 
               
               
                 ]]];n++) { 
               
               
                     rLid=RefLayerId[LayerIdInVps[targetOpLayerIdList[m]]][n] 
               
               
                    if(rLid not included in targetDLayerIdList[0,..., 
               
               
                 numDecodedLayers]) 
               
               
                      targetDLayerIdList[numDecodedLayers++]=rLId; 
               
               
                   } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     In some case the final targetDLayerIdList may be obtained by sorting the above targetDLayerIdList in increasing order of nuh_layer_id values. 
     A target decoded layer set is identified by the associated target decoded layer identifier list targetDLayerIdList. In some case the targetDLayerIdList may be same as the layer identifier list TargetDecLayerIdList from JCTVC-L1008, which specifies the list of nuh_layer_id values, in increasing order of nuh_layer_id values, of the NAL units to be decoded: 
     The selected output layer set oLsIdx is between 0 and num_output_layer_sets if there are no output layer sets change SEI messages. 
     The selected output layer set oLsIdx is between 0 and num_output_layer_sets+num_addl_output_layer_sets if there are output layer sets change SEI messages present. 
     Referring to  FIG.  37   , another SEI message syntax may be used to facilitate the change of the output layer sets, namely, output_layer_sets_change(payloadSize). 
     The ‘num_deleted_output_layer_sets’ specifies the number of output layer sets which are deleted and so are no longer present. The value of num_deleted_output_layer_sets is in the range of 0 to num_output_layer_sets, inclusive. When not present, the value of num_deleted_output_layer_sets is inferred to be equal to 0. 
     The ‘deleted_output_layer_sets_idx_entry’[i] identifies the index entry in the list of output layer set entries which is indicated to be deleted and so no longer present. The value of deleted_output_layer_set_idx_entry[i] should be in the range of 0 to num_output_layer_sets, inclusive. The deleted_output_layer_sets_idx_entry[i] is not equal to deleted_output_layer_sets_idx_entry[j] for any j not equal to i. 
     The ‘num_changed_output_layer_sets’ specifies the number of changed output layer sets for which output layers are specified in vps extension section of the active video parameter set identified by active_vps_id. The value of num_changed_output_layer_sets should be in the range of 0 to num_output_layer_sets−num_deleted_output_layer_sets, inclusive. When not present, the value of num_changed_output_layer_sets is inferred to be equal to 0. 
     A target list of output layers may be derived, if desired. The target output layer identifier list, targetOpLayerIdList, specifies the list of nuh_layer_id values, in increasing order of nuh_layer_id values which are output layers for the selected output layer set may be derived as follows: 
     For a selected output layer set oLsIdx, a target output layer identifier list targetOpLayerIdList is derived as: 
     
       
         
           
               
             
               
                 TABLE 14 
               
               
                   
               
             
            
               
                 for(k=0, numOutputLayers=0;k&lt;=vps_max_layer_id;k++) 
               
               
                 if(output_layer_flag[oLsIdx][k]) 
               
               
                  targetOpLayerIdList [numOutputLayers++]=layer_id_in_nuh[k] 
               
               
                   
               
            
           
         
       
     
     A target output layer set is identified by the associated target output layer identifier list targetOpLayerIdList. 
     The selected output layer set oLsIdx is between 0 and num_output_layer_sets if there are no output layer sets change SEI messages. 
     The selected output layer set oLsIdx is between 0 and num_output_layer_sets−num_deleted_output_layer_sets+num_addl_output_layer_sets if there are output layer sets change SEI messages present. 
     A target list of decoded layers may be derived, if desired. 
     A target decoded layer identifier list, TargetDLayerIdList, specifies the list of nuh_layer_id values, which need to be decoded for the selected output layer set may be derived as follows: 
     For a selected output layer set oLsIdx, a target output layer identifier list targetOpLayerIdList may be derived as: 
     
       
         
           
               
             
               
                 TABLE 15 
               
               
                   
               
             
            
               
                 for(k=0, numOutputLayers=0;k&lt;=vps_max_layer_id;k++) 
               
               
                 if(output_layer_flag[oLsIdx][k]) 
               
               
                  targetOpLayerId List [numOutputLayers++]=layer_id_in_nuh[k] 
               
               
                   
               
            
           
         
       
     
     Then a target decoded layer identifier list targetDLayerIdList may be derived as: 
     
       
         
           
               
             
               
                 TABLE 16 
               
               
                   
               
             
            
               
                 for(m=0, numDecodedLayers=0;m&lt; numOutputLayers;m++) { 
               
               
                  for(n=0;n&lt;NumDirectRefLayers[LayerIdInVps[targetOpLayerIdList[m 
               
               
                 ]]];n++) { 
               
               
                     rLid=RefLayerId[LayerIdInVps[targetOpLayerIdList[m]]][n] 
               
               
                    if(rLid not included in targetDLayerIdList[0,..., 
               
               
                 numDecodedLayers]) 
               
               
                      targetDLayerIdList[numDecodedLayers++]=rLId; 
               
               
                   } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     In some case the final targetDLayerIdList may be obtained by sorting the above targetDLayerIdList in increasing order of nuh_layer_id values. 
     A target decoded layer set is identified by the associated target decoded layer identifier list targetDLayerIdList. In some case the targetDLayerIdList may be same as the layer identifier list TargetDecLayerIdList from JCTVC-L1008, which specifies the list of nuh_layer_id values, in increasing order of nuh_layer_id values, of the NAL units to be decoded: 
     The selected output layer set oLsIdx is between 0 and num_output_layer_sets if there are no output layer sets change SEI messages. 
     The selected output layer set oLsIdx is between 0 and num_output_layer_sets−num_deleted_output_layer_sets+num_addl_output_layer_sets if there are output layer sets change SEI messages present. 
     The output layer sets change SEI message is defined such that its effect is not cumulative. In another embodiment this message syntax and/or semantics can be defined such that they are cumulative. In this case the decoder (and encoder) can keep track of the all the previous values of num_output_layer_sets (from vps extension) and/or num_deleted_output_layer_sets and/or num_changed_output_layer_sets and/or num_addl_output_layer_sets and can accumulate these changes every time a new SEI message is signaled. 
     In another embodiment one or more of the syntax elements may be signaled using a known fixed number of bits instead of u(v) instead of ue(v). For example they could be signaled using u(8) or u(16) or u(32) or u(64), etc. 
     In another embodiment one or more of these syntax element could be signaled with ue(v) or some other coding scheme instead of fixed number of bits such as u(v) coding. 
     In another embodiment the names of various syntax elements and their semantics may be altered by adding a plus1 or plus2 or by subtracting a minus1 or a minus2 compared to the described syntax and semantics. 
     In yet another embodiment various syntax elements included in the output layer sets SEI message may be signaled per picture or at other frequency anywhere in the bitstream. For example they may be signaled in slice segment header, pps/sps/vps/adaptation parameter set or any other parameter set or other normative part of the bitstream. 
     In yet another embodiment various syntax elements may be signaled per picture or at other frequency anywhere in the bitstream. For example they may be signaled in slice segment header, pps/sps/vps/adaptation parameter set or any other parameter set or other normative part of the bitstream. 
     In yet another embodiments all the concepts defined in this invention related to output layer sets could be applied to output operation points as defined in JCTVC-L0452 and JCTVC-L0453 and/or to operation points as defined in JCTVC-L1003. 
     Example 2 
     Another example of the present invention is described below. Note that, for convenience, members having functions identical to those of the respective members illustrated in the First Example are given respective identical reference numerals, and a description of those members is omitted here. 
     It was determined that signaling the output order decoded picture buffer (DPB) based on using sps_max_num_reorder_pics[HighestTid], sps_max_latency_increase_plus1[HighestTid] and sps_max_dec_pic_buffering[HighestTid] syntax elements for the output and removal of pictures from the DPB does not account for the buffer characteristics that may result from scalable video coding, such as when different numbers of enhancement layers are used which tends to vary after the content has been encoded based upon the user&#39;s viewing preferences, and the multi-view enhancement layers which tends to vary after the content has been encoded based upon the user&#39;s viewing preferences. Also it was determined that signaling the output order decoded picture buffer (DPB) based on using sps_max_num_reorder_pics[HighestTid], sps_max_latency_increase_plus1[HighestTid] and sps_max_dec_pic_buffering[HighestTid] syntax elements for the output and removal of pictures from the DPB may not be optimal in terms of the memory usage of the DPB when decoder operates at a certain operation point and/or is outputting selected output layer set. To accommodate such differences in the viewing preferences, the output order decoded picture buffer (DPB) may further and/or alternatively be based upon such syntax elements being included together with the video parameter set extension (VPS extension) to provide syntax elements for one or more of the enhancement layers. In this manner the syntax elements may be selected to be especially suitable for the particular operation point or output layer set, which tends to correspond to the user&#39;s viewing preferences. 
     The DPB buffering related parameters, vps_max_dec_pic_buffering_minus1, vps_max_num_reorder_pics, vps_max_latency_increase_plus1 may be signaled for sub-layers for the CVS for one or more operation points and/or for output layer sets in VPS extension. Similarly, the system may define the operation and bumping process for the output order DPB to use the above signalled DPB buffering parameters from the VPS extension if they are signalled for the operation point under test or for the selected output layer set. Otherwise the corresponding SPS level parameters from the active SPS (when currLayerId which corresponds to nuh_layer_id of the current picture is equal to 0) or from the active layer SPS depending upon the layer_id of the current layer are used. In some cases the parameters vps_max_dec_pic_buffering_minus1, vps_max_num_reorder_pics, vps_max_latency_increase_plus1 may be termed as max_vps_dec_pic_buffering_minus1, max_vps_num_reorder_pics, max_vps_latency_increase_plus1. 
     In another case the DPB buffering related parameter max_vps_dec_pic_buffering_minus1 is signaled for sub-layers for the CVS for one or more output layer sets in VPS extension. The output layer sets may correspond to operating points. The DPB buffering related parameters max_vps_num_reorder_pics, max_vps_latency_increase_plus1 may be signaled for sub-layers for the CVS for each layer in VPS extension. Similarly, the system may define the operation and bumping process for the output order DPB to use the above signalled DPB buffering parameters from the VPS extension if they are signalled for the operation point under test or for the selected output layer set. Otherwise the corresponding SPS level parameters from the active SPS (when currLayerId which corresponds to nuh_layer_id of the current picture is equal to 0) or from the active layer SPS depending upon the layer_id of the current layer are used. 
     Referring to  FIG.  38 A , an exemplary modified vps_extension is illustrated. The modified vps extension includes new syntax, namely, num_op_dpb_info_parameters and operation_point_layer_set_idx[i]. This modified vps extension may be defined in terms of the operation point which is a bitstream created from another bitstream by operation of a sub-bitstream extraction process with the another bitstream, a target highest TemporalId, and a target layer identifier list as inputs. 
     num_output_layer_sets specifies the number of layer sets for which output layers are specified with output_layer_set_index[i] and output_layer_flag[lsIdx][j]. When not present, the value of num_output_layer_sets is inferred to be equal to 0. A layer set describing output layers is an output layer set. 
     output_layer_set_idx[i] specifies the index lsIdx of the layer set for which output_layer_flag[lsIdx][j] is present. 
     output_layer_flag[lsIdx][j] equal to 1 specifies that the layer with nuh_layer_id equal to j is a target output layer of the lsIdx-th layer set. A value of output_layer_flag[lsIdx][j] equal to 0 specifies that the layer with nuh_layer_id equal to j is not a target output layer of the lsIdx-th layer set. 
     The num_op_dpb_info_parameters specifies the number of op_dpb_parameters(j) syntax structures present in the VPS extension RBSP, defined in terms of the operation point. The num_op_dpb_info_parameters decoders is in the range of 0 to vps_num_layer_sets_minus1, inclusive. 
     The operation_point_layer_set_idx[i] specifies the index, into the list of layer sets defined by operation points to which the i th op_dpb_info_parameters(j) syntax structure in the VPS extension applies. The value of operation_point_layer_set_idx[i] may be in the range of 0 to vps_num_layer_sets_minus1, inclusive. For bitstream conformance the operation_point_layer_set_idx[i] is not equal to operation_point_layer_set_idx[j] for any j not equal to i. 
     Referring to  FIG.  39 A , the op_dpb_info_parameters specifies vps_max_sub_layers_minus1[j], vps_sub_layer_ordering_info_present_flag[j], vps_max_dec_pic_buffering_minus1[j][k], vps_max_num_reorder_pics[j][k], and vps_max_latency_increase_plus1[j][k]. 
     The vps_max_sub_layers_minus1[j] plus 1 indicates how many sub layers are included. The vps_max_sub_layers_minus1[j] plus 1 specifies the maximum number of temporal sub-layers that may be present in the CVS for layer with nuh_layer_id equal to j. The value of vps_max_sub_layers_minus1[j] is in the range of 0 to 6, inclusive. 
     The vps_sub_layer_ordering_info_present_flag[j] indicates whether the syntax is for one set including all layers or for each individual layer. The vps_sub_layer_ordering_info_present_flag[j] equal to 1 specifies that vps_max_dec_pic_buffering_minus1[j][k], vps_max_num_reorder_pics[j][k], and vps_max_latency_increase_plus1[j][k] are present for layer with nuh_layer_id equal to j for vps_max_sub_layers_minus1[j]+1 sub-layers. The vps_sub_layer_ordering_info_present_flag[j] equal to 0 specifies that the values of vps_max_dec_pic_buffering_minus1[j][vps_max_sub_layers_minus1[j]], vps_max_num_reorder_pics[j][vps_max_sub_layers_minus1[j]], and vps_max_latency_increase_plus1[j][vps_max_sub_layers_minus1[j]] apply to all sub-layers for layer with nuh_layer_id equal to j. 
     The vps_max_dec_pic_buffering_minus1[j][k] plus 1 specifies the maximum required size of the decoded picture buffer for the CVS for layer with nuh_layer_id equal to j in units of picture storage buffers when HighestTid is equal to k. The value of vps_max_dec_pic_buffering_minus1[j][k] shall be in the range of 0 to MaxDpbSize−1 (as specified in subclause A.4), inclusive. When k is greater than 0, vps_max_dec_pic_buffering_minus1[j][k] shall be greater than or equal to vps_max_dec_pic_buffering_minus1[j][k−1]. When vps_max_dec_pic_buffering_minus1[j][k] is not present for k in the range of 0 to vps_max_sub_layers_minus1[j]−1, inclusive, due to vps_sub_layer_ordering_info_present_flag[j] being equal to 0, it is inferred to be equal to vps_max_dec_pic_buffering_minus1[j][vps_max_sub_layers_minus1[j]]. 
     The vps_max_num_reorder_pics[j][k] indicates the maximum allowed number of pictures that can precede any picture in the CVS for layer with nuh_layer_id equal to j in decoding order and follow that picture in output order when HighestTid is equal to k. The value of vps_max_num_reorder_pics[j][k] shall be in the range of 0 to vps_max_dec_pic_buffering_minus1[j][k], inclusive. When k is greater than 0, vps_max_num_reorder_pics[j][k] is greater than or equal to vps_max_num_reorder_pics[j][k−1]. When vps_max_num_reorder_pics[j][k] is not present for k in the range of 0 to vps_max_sub_layers_minus1[j]−1, inclusive, due to vps_sub_layer_ordering_info_present_flag[j] being equal to 0, it is inferred to be equal to vps_max_num_reorder_pics[j][vps_max_sub_layers_minus1[j]]. 
     The vps_max_latency_increase_plus1[j][k] not equal to 0 is used to compute the value of VpsMaxLatencyPictures[j][k], which specifies the maximum number of pictures that can precede any picture in the CVS for layer with nuh_layer_id equal to j in output order and follow that picture in decoding order when HighestTid is equal to k. 
     When vps_max_latency_increase_plus1[j][k] is not equal to 0, the value of VpsMaxLatencyPictures[j][k] may be specified as follows:
 
VpsMaxLatencyPictures[ j ][ k ]=vps_max_num_reorder_pics[ j ][ k ]+vps_max_latency_increase_plus1[ j ][ k ]−1
 
     When vps_max_latency_increase_plus1[j][k] is equal to 0, no corresponding limit is expressed. 
     The value of vps_max_latency_increase_plus1[j][k] is in the range of 0 to 2 32 −2, inclusive. When vps_max_latency_increase_plus1[j][k] is not present for k in the range of 0 to vps_max_sub_layers_minus1[j]−1, inclusive, due to vps_sub_layer_ordering_info_present_flag[j] being equal to 0, it is inferred to be equal to vps_max_latency_increase_plus1[j][vps_max_sub_layers_minus1[j]]. 
     The ‘vps_max_sub_layers_minus1’ [id][j] plus 1 specifies the maximum number of temporal sub-layers that may be present in the CVS for layer with nuh_layer_id equal to j for the operation point associated with index id. The value of vps_max_sub_layers_minus1[id][j] shall be in the range of 0 to 6, inclusive. 
     The ‘vps_sub_layer_ordering_info_present_flag’[id][j] equal to 1 specifies that vps_max_dec_pic_buffering_minus1[id][j][k], vps_max_num_reorder_pics[id][j][k], and vps_max_latency_increase_plus1[id][j][k] are present for layer with nuh_layer_id equal to j for the operation point associated with index id for vps_max_sub_layers_minus1[id][j]+1 sub-layers. 
     vps_sub_layer_ordering_info_present_flag[id][j] equal to 0 specifies that the values of vps_max_dec_pic_buffering_minus1 [id][j][vps_max_sub_layers_minus1[id][j]], vps_max_num_reorder_pics[id][j][vps_max_sub_layers_minus1[id][j]], and vps_max_latency_increase_plus1 [id][j][vps_max_sub_layers_minus1 [id][j] ] apply to all sub-layers for layer with nuh_layer_id equal to j for the operation point associated with index id. 
     The ‘vps_max_dec_pic_buffering_minus1’ [id][j][k] plus 1 specifies the maximum required size of the decoded picture buffer for the CVS for layer with nuh_layer_id equal to j for the operation point associated with index id in units of picture storage buffers when HighestTid is equal to k. The value of vps_max_dec_pic_buffering_minus1[id][j][k] shall be in the range of 0 to MaxDpbSize−1 (as specified in subclause A.4), inclusive. When k is greater than 0, vps_max_dec_pic_buffering_minus1[id][j][k] shall be greater than or equal to vps_max_dec_pic_buffering_minus1[id][j][k−1]. When vps_max_dec_pic_buffering_minus1[id][j][k] is not present for k in the range of 0 to vps_max_sub_layers_minus1[id][j]−1, inclusive, due to vps_sub_layer_ordering_info_present_flag[id][j] being equal to 0, it is inferred to be equal to vps_max_dec_pic_buffering_minus1[id][j][vps_max_sub_layers_minus1[id][j]]. 
     The ‘vps_max_num_reorder_pics’[id][j][k] indicates the maximum allowed number of pictures that can precede any picture in the CVS for layer with nuh_layer_id equal to j for the operation point associated with index id in decoding order and follow that picture in output order when HighestTid is equal to k. The value of vps_max_num_reorder_pics[id][j][k] shall be in the range of 0 to vps_max_dec_pic_buffering_minus1[id][j][k], inclusive. When k is greater than 0, vps_max_num_reorder_pics[id][j][k] shall be greater than or equal to vps_max_num_reorder_pics[id][j][k−1]. When vps_max_num_reorder_pics[id][j][k] is not present for k in the range of 0 to vps_max_sub_layers_minus1[id][j]−1, inclusive, due to vps_sub_layer_ordering_info_present_flag[id][j] being equal to 0, it is inferred to be equal to vps_max_num_reorder_pics[id][j][vps_max_sub_layers_minus1[id][j]]. 
     The ‘vps_max_latency_increase_plus1’ [id][j][k] not equal to 0 is used to compute the value of VpsMaxLatencyPictures[id][j][k], which specifies the maximum number of pictures that can precede any picture in the CVS for layer with nuh_layer_id equal to j for the operation point associated with index id in output order and follow that picture in decoding order when HighestTid is equal to k. 
     When vps_max_latency_increase_plus1[id][j][k] is not equal to 0, the value of VpsMaxLatencyPictures[id][j][k] is specified as follows:
 
VpsMaxLatencyPictures[ id ][ j ][ k ]=vps_max_num_reorder_pics[ id ][ j ][ k ]+vps_max_latency_increase_plus1[ id ][ j ][ k ]−1
 
     When vps_max_latency_increase_plus1[id][j][k] is equal to 0, no corresponding limit is expressed. 
     The value of vps_max_latency_increase_plus1[id][j][k] shall be in the range of 0 to 2 32 −2, inclusive. When vps_max_latency_increase_plus1[id][j][k] is not present for k in the range of 0 to vps_max_sub_layers_minus1[id][j]−1, inclusive, due to vps_sub_layer_ordering_info_present_flag[id][j] being equal to 0, it is inferred to be equal to vps_max_latency_increase_plus1[id][j][vps_max_sub_layers_minus1[id][j]]. 
     Referring to  FIG.  39    B, the op_dpb_info_parameters may be further modified as shown to op_dpb_info_parameters(id,j). In this case the syntax of VPS extension may be as illustrated in  FIG.  38 B . The hypothetical reference decoder (HRD) is used to check bitstream and decoder conformance. Two types of bitstreams or bitstream subsets are subject to HRD conformance checking for the Joint Collaborative Team on Video Coding (JCT-VC). The first type, called a Type I bitstream, is a NAL unit stream containing only the VCL NAL units and NAL units with nal_unit_type equal to FD_NUT (filler data NAL units) for all access units in the bitstream. The second type, called a Type II bitstream, contains, in addition to the VCL NAL units and filler data NAL units for all access units in the bitstream, at least one of (a) additional non-VCL NAL units other than filler data NAL units, and (b) all leading_zero_8bits, zero_byte, start_code_prefix_one_3 bytes, and trailing_zero_8bits syntax elements that form a byte stream from the NAL unit stream. 
     The syntax elements of non-VCL NAL units (or their default values for some of the syntax elements), required for the HRD, are specified in the semantic subclauses of clause 7, Annexes D and E. 
     Two types of HRD parameter sets (NAL HRD parameters and VCL HRD parameters) are used. The HRD parameter sets are signalled through the hrd_parameters( ) syntax structure, which may be part of the SPS syntax structure or the VPS syntax structure. 
     Multiple tests may be needed for checking the conformance of a bitstream, which is referred to as the bitstream under test. For each test, the following steps apply in the order listed: 
     (1) An operation point under test, denoted as TargetOp, is selected. The layer identifier list OpLayerIdList of TargetOp consists of the list of nuh_layer_id values, in increasing order of nuh_layer_id values, present in the bitstream subset associated with TargetOp, which is a subset of the nuh_layer_id values present in the bitstream under test. The OpTid of TargetOp is equal to the highest TemporalId present in the bitstream subset associated with TargetOp. 
     (2) TargetDecLayerIdList is set equal to OpLayerIdList of TargetOp, HighestTid is set equal to OpTid of TargetOp, and the sub-bitstream extraction process as specified in clause 10 is invoked with the bitstream under test, HighestTid, and TargetDecLayerIdList as inputs, and the output is assigned to BitstreamToDecode. 
     (3) The hrd_parameters(j) syntax structure and the sub_layer_hrd_parameters( ) syntax structure applicable to TargetOp are selected. If TargetDecLayerIdList contains all nuh_layer_id values present in the bitstream under test, the hrd_parameters( ) syntax structure in the active SPS (or provided through an external means not specified in this Specification) is selected. Otherwise, the hrd_parameters( ) syntax structure in the active VPS (or provided through some external means not specified in this Specification) that applies to TargetOp is selected. Within the selected hrd_parameters( ) syntax structure, if BitstreamToDecode is a Type I bitstream, the sub_layer_hrd_parameters(HighestTid) syntax structure that immediately follows the condition “if(vcl_hrd_parameters_present_flag)” is selected and the variable NalHrdModeFlag is set equal to 0; otherwise (BitstreamToDecode is a Type II bitstream), the sub_layer_hrd_parameters(HighestTid) syntax structure that immediately follows either the condition “if(vcl_hrd_parameters_present_flag)” (in this case the variable NalHrdModeFlag is set equal to 0) or the condition “if(nal_hrd_parameters_present_flag)” (in this case the variable NalHrdModeFlag is set equal to 1) is selected. When BitstreamToDecode is a Type II bitstream and NalHrdModeFlag is equal to 0, all non-VCL NAL units except filler data NAL units, and all leading_zero_8bits, zero_byte, start_code_prefix_one_3 bytes, and trailing_zero_8bits syntax elements that form a byte stream from the NAL unit stream (as specified in Annex B), when present, are discarded from BitstreamToDecode, and the remaining bitstream is assigned to BitstreamToDecode. 
     In another case Multiple tests may be needed for checking the conformance of a bitstream, which is referred to as the bitstream under test. For each test, the following steps apply in the order listed: 
     (1) An output layer set under test, denoted as TargetOpLs is selected. The operation point referred in TargetOpLs by output_layer_set_idx[ ] identifies the operation point under test. The output layer identifier list OpLayerIdList of TargetOpLs consists of the list of nuh_layer_id values, in increasing order of nuh_layer_id values, present in the bitstream subset associated with TargetOp and TargetOpLs, which is a subset of the nuh_layer_id values present in the bitstream under test. The OpTid of TargetOp is equal to the highest TemporalId present in the bitstream subset associated with TargetOp. 
     (2) TargetDecLayerIdList is set equal to target decoded layer identifier list targetDLayerIdList for the selected output layer set TargetOpLs, HighestTid is set equal to OpTid of TargetOp, and the sub-bitstream extraction process as specified in clause 10 is invoked with the bitstream under test, HighestTid, and TargetDecLayerIdList as inputs, and the output is assigned to BitstreamToDecode. 
     (3) The hrd_parameters(j) syntax structure and the sub_layer_hrd_parameters( ) syntax structure applicable to TargetOp are selected. If TargetDecLayerIdList contains all nuh_layer_id values present in the bitstream under test, the hrd_parameters( ) syntax structure in the active SPS (or provided through an external means not specified in this Specification) is selected. Otherwise, the hrd_parameters( ) syntax structure in the active VPS (or provided through some external means not specified in this Specification) that applies to TargetOp is selected. Within the selected hrd_parameters( ) syntax structure, if BitstreamToDecode is a Type I bitstream, the sub_layer_hrd_parameters(HighestTid) syntax structure that immediately follows the condition “if(vcl_hrd_parameters_present_flag)” is selected and the variable NalHrdModeFlag is set equal to 0; otherwise (BitstreamToDecode is a Type II bitstream), the sub_layer_hrd_parameters(HighestTid) syntax structure that immediately follows either the condition “if(vcl_hrd_parameters_present_flag)” (in this case the variable NalHrdModeFlag is set equal to 0) or the condition “if(nal_hrd_parameters_present_flag)” (in this case the variable NalHrdModeFlag is set equal to 1) is selected. When BitstreamToDecode is a Type II bitstream and NalHrdModeFlag is equal to 0, all non-VCL NAL units except filler data NAL units, and all leading_zero_8bits, zero_byte, start_code_prefix_one_3 bytes, and trailing_zero_8bits syntax elements that form a byte stream from the NAL unit stream (as specified in Annex B), when present, are discarded from BitstreamToDecode, and the remaining bitstream is assigned to BitstreamToDecode. 
     A conforming decoder may fulfil all requirements specified in this subclause. 
     (1) A decoder claiming conformance to a specific profile, tier and level shall be able to successfully decode all bitstreams that conform to the bitstream conformance requirements specified in subclause C.4, in the manner specified in Annex A, provided that all VPSs, SPSs and PPSs referred to in the VCL NAL units, and appropriate buffering period and picture timing SEI messages are conveyed to the decoder, in a timely manner, either in the bitstream (by non-VCL NAL units), or by external means not specified in this Specification. 
     (2) When a bitstream contains syntax elements that have values that are specified as reserved and it is specified that decoders shall ignore values of the syntax elements or NAL units containing the syntax elements having the reserved values, and the bitstream is otherwise conforming to this Specification, a conforming decoder shall decode the bitstream in the same manner as it would decode a conforming bitstream and shall ignore the syntax elements or the NAL units containing the syntax elements having the reserved values as specified. 
     There are two types of conformance of a decoder: output timing conformance and output order conformance. 
     To check conformance of a decoder, test bitstreams conforming to the claimed profile, tier and level, as specified in subclause C.4 are delivered by a hypothetical stream scheduler (HSS) both to the HRD and to the decoder under test (DUT). All cropped decoded pictures output by the HRD shall also be output by the DUT, each cropped decoded picture output by the DUT shall be a picture with PicOutputFlag equal to 1, and, for each such cropped decoded picture output by the DUT, the values of all samples that are output shall be equal to the values of the samples produced by the specified decoding process. 
     For output timing decoder conformance, the HSS operates as described above, with delivery schedules selected only from the subset of values of SchedSelIdx for which the bit rate and CPB size are restricted as specified in Annex A for the specified profile, tier and level, or with “interpolated” delivery schedules as specified below for which the bit rate and CPB size are restricted as specified in Annex A. The same delivery schedule is used for both the HRD and the DUT. 
     When the HRD parameters and the buffering period SEI messages are present with cpb_cnt_minus1[HighestTid] greater than 0, the decoder shall be capable of decoding the bitstream as delivered from the HSS operating using an “interpolated” delivery schedule specified as having peak bit rate r, CPB size c(r), and initial CPB removal delay
 
( f ( r )÷ r )  [Math. 15]
 
     as follows: 
     
       
         
           
               
               
             
               
                 TABLE 17 
               
               
                   
               
             
            
               
                 α=(r − BitRate[ SchedSelIdx − 1 ] ) ÷ (BitRate[ SchedSelIdx ] − BitRate[ SchedSelIdx − 1 ] ),  
                 (C-22) 
               
               
                 c( r ) = α* CpbSize[ SchedSelIdx ] + (1 − α) * CpbSize[ SchedSelIdx − 1 ], 
                 (C-23) 
               
               
                 f( r ) = α* InitCpbRemovalDelay[ SchedSelIdx ] * BitRate[ SchedSelIdx ] + 
                 (C-24) 
               
               
                  (1 − α) * InitCpbRernovalDelay[ SchedSelIdx − 1 ] * BitRate[ SchedSelIdx − 1 ] 
               
               
                   
               
            
           
         
       
     
     for any SchedSelIdx&gt;0 and r such that BitRate[SchedSelIdx−1]&lt;=r&lt;=BitRate[SchedSelIdx] such that r and c(r) are within the limits as specified in Annex A for the maximum bit rate and buffer size for the specified profile, tier and level. The InitCpbRemovalDelay[SchedSelIdx] can be different from one buffering period to another and have to be re-calculated. 
     For output timing decoder conformance, an HRD as described above is used and the timing (relative to the delivery time of the first bit) of picture output is the same for both the HRD and the DUT up to a fixed delay. 
     For output order decoder conformance, the following applies: 
     (1) The HSS delivers the bitstream BitstreamToDecode to the DUT “by demand” from the DUT, meaning that the HSS delivers bits (in decoding order) only when the DUT requires more bits to proceed with its processing. This means that for this test, the coded picture buffer of the DUT could be as small as the size of the largest decoding unit. 
     (2) A modified HRD as described below is used, and the HSS delivers the bitstream to the HRD by one of the schedules specified in the bitstream BitstreamToDecode such that the bit rate and CPB size are restricted as specified in Annex A. The order of pictures output shall be the same for both the HRD and the DUT. 
     (3) The HRD CPB size is given by CpbSize[SchedSelIdx] as specified in subclause E.2.3, where SchedSelIdx and the HRD parameters are selected as specified in subclause C.1. The DPB size is given by sps_max_dec_pic_buffering_minus1[HighestTid]+1 from the active SPS (when nuh_layer_id for the current decoded picture is equal to 0) or from the active layer SPS for the value of nuh_layer_id of the current decoded picture. In some cases, if operation point DPB information parameters op_dpb_info_parameters( ) are present for the selected output layer set, The DPB size is given by vps_max_dec_pic_buffering_minus1[HighestTid] when currLayerId is equal to 0 or is set to vps_max_dec_pic_buffering_minus1[CurrLayerId][HighestTid] for the currLayerId for the operation point under test when currLayerId is greater than 0, where currLayerId is the nuh_layer_id of the current decoded picture. Otherwise if operation point DPB information parameters op_dpb_info_parameters( ) are not present for the operation point under test, the DPB Size is given by sps_max_dec_pic_buffering_minus1[HighestTid]+1 from the active SPS (when nuh_layer_id for the current decoded picture is equal to 0) or from the active layer SPS for the value of nuh_layer_id of the current decoded picture. 
     In some cases, if output layer sets DPB information parameters oop_dpb_info_parameters( ) are present for the selected output layer set, The DPB size is given by vps_max_dec_pic_buffering_minus1[HighestTid] when currLayerId is equal to 0 or is set to vps_max_dec_pic_buffering_minus1[CurrLayerId][HighestTid] for the currLayerId for the selected output layer set, where currLayerId is the nuh_layer_id of the current decoded picture. Otherwise if output layer sets DPB information parameters oop_dpb_info_parameters( ) are not present for the selected output layer set, the DPB Size is given by sps_max_dec_pic_buffering_minus1[HighestTid]+1 from the active SPS (when nuh_layer_id for the current decoded picture is equal to 0) or from the active layer SPS for the value of nuh_layer_id of the current decoded picture. 
     The removal time from the CPB for the HRD is the final bit arrival time and decoding is immediate. The operation of the DPB of this HRD is as described in subclauses C.5.2 through C.5.2.3. 
     The decoded picture buffer contains picture storage buffers. The number of picture storage buffers for nuh_layer_id equal to 0 is derived from the active SPS. The number of picture storage buffers for each non-zero nuh_layer_id value is derived from the active layer SPS for that non-zero nuh_layer_id value. Each of the picture storage buffers contains a decoded picture that is marked as “used for reference” or is held for future output. The process for output and removal of pictures from the DPB as specified in subclause F.13.5.2.2 is invoked, followed by the invocation of the process for picture decoding, marking, additional bumping, and storage as specified in subclause F.13.5.2.3. The “bumping” process is specified in subclause F.13.5.2.4 and is invoked as specified in subclauses F.13.5.2.2 and F.13.5.2.3. 
     The output and removal of pictures from the DPB before the decoding of the current picture (but after parsing the slice header of the first slice of the current picture) happens instantaneously when the first decoding unit of the access unit containing the current picture is removed from the CPB and proceeds as follows. 
     The decoding process for RPS as specified in subclause 8.3.2 is invoked. 
     (1) If the current picture is an IRAP picture with NoRaslOutputFlag equal to 1 and with nuh_layer_id equal to 0 that is not picture 0, the following ordered steps are applied: 
     (A) The variable NoOutputOfPriorPicsFlag is derived for the decoder under test as follows: 
     (i) If the current picture is a CRA picture, NoOutputOfPriorPicsFlag is set equal to 1 (regardless of the value of no_output_of_prior_pics_flag). 
     (ii) Otherwise, if the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps_max_dec_pic_buffering_minus1[HighestTid] derived from the active SPS is different from the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps_max_dec_pic_buffering_minus1[HighestTid], respectively, derived from the SPS active for the preceding picture, NoOutputOfPriorPicsFlag may (but should not) be set to 1 by the decoder under test, regardless of the value of no_output_of_prior_pics_flag. Although setting NoOutputOfPriorPicsFlag equal to no_output_of_prior_pics_flag is preferred under these conditions, the decoder under test is allowed to set NoOutputOfPriorPicsFlag to 1 in this case. 
     (iii) Otherwise, NoOutputOfPriorPicsFlag is set equal to no_output_of_prior_pics_flag. 
     (B) The value of NoOutputOfPriorPicsFlag derived for the decoder under test is applied for the HRD as follows: 
     (i) If NoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers in the DPB are emptied without output of the pictures they contain, and the DPB fullness is set equal to 0. 
     (ii) Otherwise (NoOutputOfPriorPicsFlag is equal to 0), all picture storage buffers containing a picture that is marked as “not needed for output” and “unused for reference” are emptied (without output), and all non-empty picture storage buffers in the DPB are emptied by repeatedly invoking the “bumping” process specified in subclause F.13.5.2.4, and the DPB fullness is set equal to 0. 
     (iii) Otherwise (the current picture is not an IRAP picture with NoRaslOutputFlag equal to 1 and with nuh_layer_id equal to 0), all picture storage buffers containing a picture which are marked as “not needed for output” and “unused for reference” are emptied (without output). For each picture storage buffer that is emptied, the DPB fullness is decremented by one. The variable currLayerId is set equal to nuh_layer_id of the current decoded picture. 
     The variables MaxNumReorderPics[TargetOp][currLayerId][HighestTid], MaxLatencyIncreasePlus1[TargetOp][currLayerId][HighestTid], MaxLatencyPictures[TargetOp][currLayerId][HighestTid], MaxDecPicBufferingMinus1[TargetOp][currLayerId][HighestTid] are derived as follows based on the current operation point under test: 
     (1) If operation point DPB information parameters op_dpb_info_parameters( ) are present for the operation point under test TargetOp, MaxNumReorderPics[TargetOp][currLayerId][HighestTid] is set to vps_max_num_reorder_pics[HighestTid] when currLayerId is equal to 0 or is set to vps_max_num_reorder_pics[TargetOp][CurrLayerId][HighestTid] for the currLayerId for the operation point under test when currLayerId is greater than 0. Otherwise if operation point DPB information parameters op_dpb_info_parameters( ) are not present for the operation point under test MaxNumReorderPics[TargetOp][currLayerId][HighestTid] is set to sps_max_num_reorder_pics[HighestTid] from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId. 
     (2) If operation point DPB information parameters op_dpb_info_parameters( ) are present for the operation point under test TargetOp, MaxLatencyIncreasePlus1[TargetOp][currLayerId][HighestTid] is set to vps_max_latency_increase_plus1[HighestTid] when currLayerId is equal to 0 or is set to vps_max_latency_increase_plus1[TargetOp][CurrLayerId][HighestTid] for the currLayerId for the operation point under test when currLayerId is greater than 0. If operation point DPB information parameters op_dpb_info_parameters( ) are present for the operation point under test, MaxLatencyPictures[TargetOp][currLayerId][HighestTid] is set to VpsMaxLatencyPictures[HighestTid] when currLayerId is equal to 0 or is set to VpsMaxLatencyPictures[TargetOp][CurrLayerId][HighestTid] for the currLayerId for the operation point under test when currLayerId is greater than 0. Otherwise if operation point DPB information parameters op_dpb_info_parameters( ) are not present for the operation point under test, MaxLatencyIncreasePlus1[TargetOp][currLayerId][HighestTid] is set to sps_max_latency_increase_plus1 [HighestTid] of the active SPS (when currLayerId is equal to 0) or the active layer SPS for the value of currLayerId and MaxLatencyPictures[TargetOp][currLayerId][HighestTid] is set to SpsMaxLatencyPictures[HighestTid] derived from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId. 
     (3) If operation point DPB information parameters op_dpb_info_parameters( ) are present for the selected operation point under test TargetOp, MaxDecPicBufferingMinus1[TargetOp][currLayerId][HighestTid] is set to vps_max_dec_pic_buffering_minus1[HighestTid] when currLayerId is equal to 0 or is set to vps_max_dec_pic_buffering_minus1[TargetOp][CurrLayerId][HighestTid] for the currLayerId for the operation point under test when currLayerId is greater than 0. Otherwise if operation point DPB information parameters op_dpb_info_parameters( ) are not present for the operation point under test, MaxDecPicBufferingMinus1[TargetOp][currLayerId][HighestTid] is set to sps_max_dec_pic_buffering_minus1[HighestTid] from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId. 
     When one or more of the following conditions are true, the “bumping” process specified in subclause F.13.5.2.4 is invoked repeatedly while further decrementing the DPB fullness by one for each additional picture storage buffer that is emptied, until none of the following conditions are true: 
     (1) The number of pictures with nuh_layer_id equal to currLayerId in the DPB that are marked as “needed for output” is greater than MaxNumReorderPics[TargetOp][CurrLayerId][HighestTid]. 
     (2) If MaxLatencyIncreasePlus1[TargetOp][CurrLayerId][HighestTid] is not equal to 0 and there is at least one picture with nuh_layer_id equal to currLayerId in the DPB that is marked as “needed for output” for which the associated variable PicLatencyCount[currLayerId] is greater than or equal to MaxLatencyPictures[TargetOp][CurrLayerId][HighestTid]. 
     (3) The number of pictures with nuh_layer_id equal to currLayerId in the DPB is greater than or equal to MaxDecPicBuffering[TargetOp][CurrLayerId][HighestTid]. 
     The processes specified in this subclause happen instantaneously when the last decoding unit of access unit n containing the current picture is removed from the CPB. 
     The variable currLayerId is set equal to nuh_layer_id of the current decoded picture. 
     For each picture in the DPB that is marked as “needed for output” and that has a nuh_layer_id value equal to currLayerId, the associated variable PicLatencyCount[currLayerId] is set equal to PicLatencyCount[currLayerId]+1. 
     The current picture is considered as decoded after the last decoding unit of the picture is decoded. The current decoded picture is stored in an empty picture storage buffer in the DPB, and the following applies: 
     (A) If the current decoded picture has PicOutputFlag equal to 1, it is marked as “needed for output” and its associated variable PicLatencyCount[currLayerId] is set equal to 0. 
     (B) Otherwise (the current decoded picture has PicOutputFlag equal to 0), it is marked as “not needed for output”. 
     The current decoded picture is marked as “used for short-term reference”. 
     When one or more of the following conditions are true, the “bumping” process specified in subclause F.13.5.2.4 is invoked repeatedly until none of the following conditions are true. 
     (A) The number of pictures with nuh_layer_id equal to currLayerId in the DPB that are marked as “needed for output” is greater than MaxNumReorderPics[TargetOp][CurrLayerId][HighestTid]. 
     (B) MaxLatencyIncreasePlus1[TargetOp][CurrLayerId][HighestTid] is not equal to 0 and there is at least one picture with nuh_layer_id equal to currLayerId in the DPB that is marked as “needed for output” for which the associated variable PicLatencyCount[currLayerId] is greater than or equal to MaxLatencyPictures[TargetOp][CurrLayerId][HighestTid]. 
     In other case the variables MaxNumReorderPics[currLayerId][HighestTid], MaxLatencyIncreasePlus1[currLayerId][HighestTid], MaxLatencyPictures[currLayerId][HighestTid], MaxDecPicBufferingMinus1[currLayerId][HighestTid]may be derived as follows: 
     (1) If operation point DPB information parameters op_dpb_info_parameters( ) are present for the operation point under test, MaxNumReorderPics[currLayerId][HighestTid] is set to vps_max_num_reorder_pics[HighestTid] when currLayerId is equal to 0 or is set to vps_max_num_reorder_pics[CurrLayerId][HighestTid] for the currLayerId for the operation point under test when currLayerId is greater than 0. Otherwise if operation point DPB information parameters op_dpb_info_parameters( ) are not present for the operation point under test MaxNumReorderPics[currLayerId][HighestTid] is set to sps_max_num_reorder_pics[HighestTid] from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId. 
     (2) If operation point DPB information parameters op_dpb_info_parameters( ) are present for the operation point under test, MaxLatencyIncreasePlus1[currLayerId][HighestTid] is set to vps_max_latency_increase_plus1[HighestTid] when currLayerId is equal to 0 or is set to vps_max_latency_increase_plus1[CurrLayerId][HighestTid] for the currLayerId for the operation point under test when currLayerId is greater than 0. If operation point DPB information parameters op_dpb_info_parameters( ) are present for the operation point under test, MaxLatencyPictures[currLayerId][HighestTid] is set to VpsMaxLatencyPictures [HighestTid] when currLayerId is equal to 0 or is set to VpsMaxLatencyPictures [CurrLayerId][HighestTid] for the currLayerId for the operation point under test when currLayerId is greater than 0. Otherwise if operation point DPB information parameters op_dpb_info_parameters( ) are not present for the operation point under test, MaxLatencyIncreasePlus1[currLayerId][HighestTid] is set to sps_max_latency_increase_plus1[HighestTid] of the active SPS (when currLayerId is equal to 0) or the active layer SPS for the value of currLayerId and MaxLatencyPictures[currLayerId][HighestTid] is set to SpsMaxLatencyPictures [HighestTid] derived from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId. 
     (3) If operation point DPB information parameters op_dpb_info_parameters( ) are present for the selected operation point under test, MaxDecPicBufferingMinus1[currLayerId][HighestTid] is set to vps_max_dec_pic_buffering_minus1[HighestTid] when currLayerId is equal to 0 or is set to vps_max_dec_pic_buffering_minus1[CurrLayerId][HighestTid] for the currLayerId for the operation point under test when currLayerId is greater than 0. Otherwise if operation point DPB information parameters op_dpb_info_parameters( ) are not present for the operation point under test, MaxDecPicBufferingMinus1[currLayerId][HighestTid] is set to sps_max_dec_pic_buffering_minus1[HighestTid] from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId. 
     When one or more of the following conditions are true, the “bumping” process specified in subclause F.13.5.2.4 is invoked repeatedly while further decrementing the DPB fullness by one for each additional picture storage buffer that is emptied, until none of the following conditions are true: 
     (1) The number of pictures with nuh_layer_id equal to currLayerId in the DPB that are marked as “needed for output” is greater than MaxNumReorderPics[CurrLayerId][HighestTid]. 
     (2) If MaxLatencyIncreasePlus1[CurrLayerId][HighestTid] is not equal to 0 and there is at least one picture with nuh_layer_id equal to currLayerId in the DPB that is marked as “needed for output” for which the associated variable PicLatencyCount[currLayerId] is greater than or equal to MaxLatencyPictures[CurrLayerId][HighestTid]. 
     (3) The number of pictures with nuh_layer_id equal to currLayerId in the DPB is greater than or equal to MaxDecPicBuffering[CurrLayerId][HighestTid]. 
     The processes specified in this subclause happen instantaneously when the last decoding unit of access unit n containing the current picture is removed from the CPB. 
     The variable currLayerId is set equal to nuh_layer_id of the current decoded picture. 
     For each picture in the DPB that is marked as “needed for output” and that has a nuh_layer_id value equal to currLayerId, the associated variable PicLatencyCount[currLayerId] is set equal to PicLatencyCount[currLayerId]+1. 
     The current picture is considered as decoded after the last decoding unit of the picture is decoded. The current decoded picture is stored in an empty picture storage buffer in the DPB, and the following applies: 
     (A) If the current decoded picture has PicOutputFlag equal to 1, it is marked as “needed for output” and its associated variable PicLatencyCount[currLayerId] is set equal to 0. 
     (B) Otherwise (the current decoded picture has PicOutputFlag equal to 0), it is marked as “not needed for output”. 
     The current decoded picture is marked as “used for short-term reference”. 
     When one or more of the following conditions are true, the “bumping” process specified in subclause F.13.5.2.4 is invoked repeatedly until none of the following conditions are true. 
     (A) The number of pictures with nuh_layer_id equal to currLayerId in the DPB that are marked as “needed for output” is greater than MaxNumReorderPics[CurrLayerId][HighestTid]. 
     (B) MaxLatencyIncreasePlus1[CurrLayerId][HighestTid] is not equal to 0 and there is at least one picture with nuh_layer_id equal to currLayerId in the DPB that is marked as “needed for output” for which the associated variable PicLatencyCount[currLayerId ] is greater than or equal to MaxLatencyPictures [CurrLayerId][HighestTid]. 
     The “bumping” process consists of the following ordered steps: 
     (A) The pictures that are first for output are selected as the ones having the smallest value of PicOrderCntVal of all pictures in the DPB marked as “needed for output”. 
     (B) These pictures are cropped, using the conformance cropping window specified in the active SPS for the picture with nuh_layer_id equal to 0 or in the active layer SPS for a nuh_layer_id value equal to that of the picture, the cropped pictures are output in ascending order of nuh_layer_id, and the pictures are marked as “not needed for output”. 
     (C) Each picture storage buffer that contains a picture marked as “unused for reference” and that included one of the pictures that was cropped and output is emptied. 
     The VPS Extension may have additional modifications, if desired. 
     Referring to  FIG.  40   , an additional modification may include the DPB parameters being sent in the VPS extension for output layer sets instead of for operation points, where the oops_dpb_info_parameters(j) are illustrated in  FIG.  41   . 
     The num_dpb_info_parameters specifies the number of oop_dpb_parameters( ) syntax structures present in the VPS extension RBSP. num_dpb_info_parameters decoders shall be in the range of 0 to num_output_layer_sets, inclusive. 
     The output_point_layer_set_idx[i] specifies the index, into the list of target output layer sets to which the i th oop_dpb_info_parameters( ) syntax structure in the VPS extension applies. 
     The value of output_point_layer_set_idx[i] should be in the range of 0 to num_output_layer_sets, inclusive. It is requirement of bitstream conformance that output_point_layer_set_idx [i] shall not be equal to output_point_layer_set_idx [j] for any j not equal to i. 
     Referring to  FIG.  42   , the oop_dpb_info_paremters(c) may be further modified, where the syntax in the VPS extension may be as illustrated in  FIG.  43   . 
     Referring to  FIG.  44   , the oop_dpb_info_paremters(c) may be further modified, where the syntax in the VPS extension may be as illustrated in  FIG.  45    or  FIG.  46   . 
     An exemplary alternative for the syntax in VPS extension is that 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 18 
               
               
                   
                   
               
             
            
               
                   
                   
                 for( j = 0; j &lt;= vps_max_layer_id; j++ ) 
               
               
                   
                   
                  oop_dpb_info_parameters(j) 
               
               
                   
                   
               
            
           
         
       
     
     may be changed to 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 19 
               
               
                   
                   
               
             
            
               
                   
                   
                 for( j = 0; j &lt;= vps_max_layers_minus1; j++ ) 
               
               
                   
                   
                  oop_dpb_info_parameters(j) 
               
               
                   
                   
               
            
           
         
       
     
     The vps_max_layer_id specifies the maximum allowed value of nuh_layer_id of all NAL units in the CVS. The vps_max_layers_minus1, specifies the maximum number of layers that may be present in the CVS, wherein a layer may e.g. be a spatial scalable layer, a quality scalable layer, a texture view or a depth view. 
     Another exemplary alternative for the syntax in VPS extension is that 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 20 
               
               
                   
                   
               
             
            
               
                   
                   
                 for( j = 0; j &lt;= vps_max_layer_id; j++ ) 
               
               
                   
                   
                  oop_dpb_info_parameters(j) 
               
               
                   
                   
               
            
           
         
       
     
     may be changed to 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 21 
               
               
                   
                   
               
             
            
               
                   
                   
                 for( j = 0; j &lt; numOutputLayers; j++ ) 
               
               
                   
                   
                  oop_dpb_info_parameters(j) 
               
               
                   
                   
               
            
           
         
       
     
     where numOutputLayers for the selected output layer set index oplsIdx is derived as: 
     
       
         
           
               
             
               
                 TABLE 22 
               
               
                   
               
             
            
               
                 for(k=0, numOutputLayers=0;k&lt;=vps_max_layer_id;k++) 
               
               
                 if(output_layer_flag[opLsIdx][k]) 
               
               
                  targetOpLayerIdList [numOutputLayers++]=layer_id_in_nuh[k] 
               
               
                   
               
            
           
         
       
     
     Another exemplary alternative for the syntax in VPS extension is that 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 23 
               
               
                   
                   
               
             
            
               
                   
                   
                 for( j = 0; j &lt;= vps_max_layer_id; j++ ) 
               
               
                   
                   
                  oop_dpb_info_parameters(j) 
               
               
                   
                   
               
            
           
         
       
     
     may be changed to 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 24 
               
               
                   
                   
               
             
            
               
                   
                   
                 for( j = 0; j &lt; numDecodedLayers; j++ ) 
               
               
                   
                   
                  oop_dpb_info_parameters(j) 
               
               
                   
                   
               
            
           
         
       
     
     where numOutputLayers for the selected oplsIdx is derived as: 
     
       
         
           
               
             
               
                 TABLE 25 
               
               
                   
               
             
            
               
                 for(k=0, numOutputLayers=0;k&lt;=vps_max_layer_id;k++) 
               
               
                 if(output_layer_flag[opLsIdx][k]) 
               
               
                  targetOpLayerIdList [numOutputLayers++]=layer_id_in_nuh[k] 
               
               
                   
               
            
           
         
       
     
     Then a target decoded layer identifier list targetDLayerIdList and numDecodedLayers for the selected oplsIdx is derived as: 
     
       
         
           
               
             
               
                 TABLE 26 
               
               
                   
               
             
            
               
                 for(m=0, numDecodedLayers=0;m&lt; numOutputLayers;m++) { 
               
               
                  for(n=0;n&lt;NumDirectRefLayers[LayerIdInVps[targetOpLayerIdList[ 
               
               
                 m]]];n++) { 
               
               
                   rLid=RefLayerId[LayerIdInVps[targetOpLayerIdList[m]]][n] 
               
               
                   if(rLid not included in targetDLayerIdList[0,..., 
               
               
                 numDecodedLayers]) 
               
               
                    targetDLayerIdList[numDecodedLayers++]=rLId; 
               
               
                   } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     In one embodiment an additional flag maybe signalled to indicate if oop_dpb_information_parameters are signalled for the particular layer as follows: 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 27 
               
               
                   
                   
               
             
            
               
                   
                 for( j = 0; j &lt;= vps_max_layer_id; j++ ) { 
                   
               
               
                   
                  vps_layer_info_present_flag[j] 
                 u(1)  
               
               
                   
                  if(vps_layer info_present_flag)  
                   
               
               
                   
                   oop_dpb_info_parameters(j)  
                   
               
               
                   
                 } 
               
               
                   
                   
               
            
           
         
       
     
     The vps_layer_info_present_flag[j] equal to 1 specifies that oop_dpb_info_parameters are present for the j&#39;th layer for the particular output layer set. vps_layer_info_present_flag[j] equal to 0 specifies that oop_dpb_info_parameters are not present for the j&#39;th layer for the particular output layer set. 
     In another embodiment num_dpb_info_parameters decoders shall be in the range of 0 to 1024, inclusive. In yet another embodiment a different fixed number could be used in place of 1024. 
     In an alternative embodiment output_point_layer_set_idx[i] is in the range of 0 to 1023, inclusive. 
     Referring to  FIG.  47   , another modified VPS extension and layer_dpb_info(i) may be used if the DPB parameters are sent in the VPS extension for each layer independently of output layer sets and operation points. 
     Referring to  FIG.  48   , a modified layer_dpb_info(i) may be used where the syntax element vps_max_sub_layer_minus1 signaled from VPS is used for all the layers and is not separately signalled in oop_dpb_info_parameters(id)/op_dpb_info_parameters(id). 
     Referring to  FIGS.  49 A and  49 B , an exemplary modified vps_extension is illustrated. The modified vps extension includes new syntax, namely, max_sub_layers_vps_predict_flag[i], max_sub_layers_vps_minus1[i] num_dpb_info_parameters, output_point_layer_set_idx[i], oop_dpb_maxbuffering_parameters(i), and layer_dpb_info_parameters(i). num_output_layer_sets specifies the number of layer sets for which output layers are specified with output_layer_set_index[i] and output_layer_flag[lsIdx][j]. When not present, the value of num_output_layer_sets is inferred to be equal to 0. A layer set describing output layers is an output layer set. 
     ‘max_sub_layers_vps_predict_flag’[i] equal to 1 specifies that max_sub_layers_vps_minus1[i] is inferred to be equal to max_sub_layers_vps_minus1[i−1]. 
     max_sub_layers_vps_predict_flag[i] equal to 0 specifies that max_sub_layers_vps_minus1[i] is explicitly signalled. The value of max_sub_layers_vps_predict_flag[0] is inferred to be equal to 0. 
     ‘max_sub_layers_vps_minus1’ [i] plus 1 specifies the maximum number of temporal sub-layers that may be present in the CVS for layer with nuh_layer_id equal to i. The value of max_vps_sub_layers_vps_minus1[i] shall be in the range of 0 to 6, inclusive. In some cases max_sub_layers_vps_minus1[i] is used for the inference of the SPS syntax element sps_max_sub_layers_minus1. When max_sub_layers_vps_predict_flag[i] is equal to 1, max_sub_layers_vps_minus1[i] is inferred to be equal to max_sub_layers_vps_minus1[i−1]. The value of max_sub_layers_vps_minus1[0] is inferred to be equal to vps_max_sub_layers_minus1. 
     The variable MaxSubLayers[setId] for setId in the range of 0 to num_dpb_info_parameters−1, inclusive, is derived as follows: 
     
       
         
           
               
             
               
                 TABLE 28 
               
               
                   
               
             
            
               
                 for( setId = 0; setId &lt; num_dpb_info_parameters; setId++ ) { 
               
               
                  lsIdx = 
               
               
                 output_layer_set_idx_minus1[ output_point_layer_set_idx[ setId] ] + 1 
               
               
                   highestLayerId = 
               
               
                 layerSetLayerIdList[lsIdx][numLayersInIdList[lsIdx]−1] 
               
               
                   MaxSubLayers[setId] = 
               
               
                 ( max_sub_layers_vps_minus1[highestLayerId]+1 ) ) 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     ‘num_dpb_info_parameters’ specifies the number of oop_dpb_maxbuffering_parameters(i) syntax structures present in the VPS extension RBSP. num_dpb_info_parameters decoders shall be in the range of 0 to numOutputLayerSets, inclusive. 
     ‘output_point_layer_set_idx’[i] specifies the index, into the list of output layer sets to which the i th oop_dpb_maxbuffering_parameters(i) syntax structure in the VPS extension applies. 
     The value of output_point_layer_set_idx[i] should be in the range of 0 to numOutputLayerSets, inclusive. It is requirement of bitstream conformance that 
     output_point_layer_set_idx [i] shall not be equal to output_point_layer_set_idx [j] for any j not equal to i. 
     Referring to  FIG.  50   , the oop_dpb_maxbuffering_parameters specifies ‘sub_layer_vps_buf_info_present_flag’[i], ‘max_vps_dec_pic_buffering_minus1’ [i][j]. 
     ‘sub_layer_vps_buf_info_present_flag’[i] equal to 1 specifies that max_vps_dec_pic_buffering_minus1[i][j] are present for MaxSubLayers[i] sub-layers. sub_layer_vps_buf_info_present_flag[i] equal to 0 specifies that the values of max_vps_dec_pic_buffering_minus1[i][MaxSubLayers[i]−1] apply to all sub-layers. 
     ‘max_vps_dec_pic_buffering_minus1’[i][j] plus 1 specifies the maximum required size of the decoded picture buffer for the CVS for layer with nuh_layer_id equal to highestLayerId in the output layer set associated with index i in units of picture storage buffers when HighestTid is equal to j. The value of max_vps_dec_pic_buffering_minus1[i][j] shall be in the range of 0 to MaxDpbSize−1 (as specified in subclause A.4), inclusive. When j is greater than 0, max_vps_dec_pic_buffering_minus1[i][j] shall be greater than or equal to max_vps_dec_pic_buffering_minus1[i][j−1] In some cases max_vps_dec_pic_buffering_minus1[i][j] is used for inference of the values of the SPS syntax elements sps_max_dec_pic_buffering_minus1[j]. When max_vps_dec_pic_buffering_minus1[i][j] is not present for i in the range of 0 to MaxSubLayers[i]−2, inclusive, due to sub_layer_vps_buf_info_present_flag[i] being equal to 0, it is inferred to be equal to max_vps_dec_pic_buffering_minus1[i][MaxSubLayers[i]−1]. 
     The value of max_vps_dec_pic_buffering_minus1[0][j] for each value of j is inferred to be equal to vps_max_dec_pic_buffering_minus1[j]. 
     Referring to  FIG.  51   , the layer_dpb_info_parameters specifies ‘sub_layer_vps_ordering_info_present_flag’[i], max_vps_num_reorder_pics[i][j], ‘max_vps_latency_increase_plus1’[i][j]. 
     ‘sub_layer_vps_ordering_info_present_flag’[i] equal to 1 specifies that max_vps_num_reorder_pics[i][j] and max_vps_latency_increase_plus1[i][j] are present for max_sub_layers_vps_minus1+1 sub-layers. 
     sub_layer_vps_ordering_info_present_flag[i] equal to 0 specifies that the values of max_vps_num_reorder_pics[i][vps_max_sub_layers_minus1] and max_vps_latency_increase_plus1[i][max_sub_layers_vps_minus1] apply to all sub-layers. 
     ‘max_vps_num_reorder_pics’[i][j] indicates the maximum allowed number of pictures that can precede any picture in the CVS for layer with nuh_layer_id equal to i in decoding order and follow that picture in output order when HighestTid is equal to j. The value of max_vps_num_reorder_pics[i][j] shall be in the range of 0 to max_vps_dec_pic_buffering_minus1[i][j], inclusive. When j is greater than 0, max_vps_num_reorder_pics[i][j] shall be greater than or equal to max_vps_num_reorder_pics[i][j−1] In some cases max_vps_num_reorder_pics[i][j] is used for inference of the values of the SPS syntax element sps_max_num_reorder_pics[j]. When max_vps_num_reorder_pics[i][j] is not present for i in the range of 0 to max_sub_layers_vps_minus1[i]−1, inclusive, due to sub_layer_vps_ordering_info_present_flag[i] being equal to 0, it is inferred to be equal to max_vps_num_reorder_pics[i][max_sub_layers_vps_minus1[i]]. 
     max_vps_latency_increase_plus1[i][j] not equal to 0 is used to compute the value of VpsMaxLatencyPictures[i][j], which specifies the maximum number of pictures that can precede any picture in the CVS for layer with nuh_layer_id equal to i in output order and follow that picture in decoding order when HighestTid is equal to j. 
     When max_vps_latency_increase_plus1[i][j] is not equal to 0, the value of VpsMaxLatencyPictures[i][j] is specified as follows:
 
VpsMaxLatencyPictures[ i ][ j ]=max_vps_num_reorder_pics[ i ][ j ]+max_vps_latency_increase_plus1[ i ][ j ]−1
 
     When max_vps_latency_increase_plus1[i][j] is equal to 0, no corresponding limit is expressed. 
     The value of max_vps_latency_increase_plus1[j][k] shall be in the range of 0 to 2 32 −2, inclusive. In some cases max_vps_latency_increase_plus1[i][j] is used for inference of the values of the SPS syntax elements sps_max_latency_increase_plus1[j]. When max_vps_latency_increase_plus1[i][j] is not present for i in the range of 0 to max_sub_layers_vps_minus1[i]−1, inclusive, due to sub_layer_vps_ordering_info_present_flag[i] being equal to 0, it is inferred to be equal to max_vps_latency_increase_plus1[i][max_sub_layers_vps_minus1[i]]. 
     Referring to  FIG.  52   , an exemplary modified vps_extension is illustrated. The modified vps extension includes further modification of the syntax in  FIG.  49    with new syntax, namely, sub_layer_vps_buf_info_predict_flag[i], sub_layer_vps_ordering_info_predict_flag[i] which are conditionally signalled. sub_layer_vps_buf_info_predict_flag[i] equal to 1 specifies that max_vps_dec_pic_buffering_minus1[i][j] is inferred to be equal to max_vps_dec_pic_buffering_minus1[i−1][j] for each value of j. 
     sub_layer_vps_buf_info_predict_flag[i] equal to 0 specifies that max_vps_dec_pic_buffering_minus1[i][j] for at least one value of j is explicitly signalled. sub_layer_vps_buf_info_predict_flag[0] is inferred to be equal to 0. When not present, sub_layer_vps_buf_info_predict_flag[i] is inferred to be equal to 0. 
     sub_layer_vps_ordering_info_predict_flag[i] equal to 1 specifies that the syntax elements sub_layer_vps_ordering_info_present_flag[i], max_vps_num_reorder_pics[i][j], and max_vps_latency_increase_plus1[i][j] are inferred to be equal to sub_layer_vps_ordering_info_present_flag[i−1], max_vps_num_reorder_pics[i−1][j], and max_vps_latency_increase_plus1[i 1][j], respectively. sub_layer_vps_ordering_info_predict_flag[i] equal to 0 indicates that the syntax elements sub_layer_vps_ordering_info_present_flag[i], max_vps_num_reorder_pics[i][j], and max_vps_latency_increase_plus1[i][j] are explicitly signalled. When not present, the value of sub_layer_vps_ordering_info_predict_flag[i] is set equal to 0. 
     Other syntax elements and their semantic meanings for  FIG.  52    are same as those for  FIG.  49   . 
     Referring to  FIG.  53   , an exemplary modified vps_extension is illustrated. The modified vps extension includes further modification of the syntax in  FIG.  49   . In  FIG.  53    oop_dpb_maxbuffering_parameters(i,j) are signalled for each layer j for the particular output layer set i compared to  FIG.  49    which signals a single set of oop_dpb_maxbuffering_parameters(i) parameters for the highest layer id in the output layer set i. 
     Referring to  FIG.  54   , the oop_dpb_maxbuffering_parameters specifies sub_layer_vps_buf_info_present_flag[i][k], max_vps_dec_pic_buffering_minus1[i][k][j]. 
     sub_layer_vps_buf_info_present_flag[i][k] equal to 1 specifies that max_vps_dec_pic_buffering_minus1[i][k][j] are present for max_sub_layers_vps_minus1[k] sub-layers. sub_layer_vps_buf_info_present_flag[i] equal to 0 specifies that the values of max_vps_dec_pic_buffering_minus1[i][k][max_sub_layers_vps_minus1[k]] apply to all sub-layers. 
     max_vps_dec_pic_buffering_minus1[i][k][j] plus 1 specifies the maximum required size of the decoded picture buffer for the CVS for layer with nuh_layer_id equal to k for the output layer set associated with index i in units of picture storage buffers when HighestTid is equal to j. The value of max_vps_dec_pic_buffering_minus1 [i][k][j] shall be in the range of 0 to MaxDpbSize−1 (as specified in subclause A.4), inclusive. 
     When j is greater than 0, max_vps_dec_pic_buffering_minus1[i][k][j] shall be greater than or equal to max_vps_dec_pic_buffering_minus1[i][k][j−1] are used for inference of the values of the SPS syntax elements sps_max_dec_pic_buffering_minus1[j]. 
     When max_vps_dec_pic_buffering_minus1[i][j] is not present for i in the range of 0 to max_sub_layers_vps_minus1[k]−1, inclusive, due to sub_layer_vps_buf_info_present_flag[i][k] being equal to 0, it is inferred to be equal to max_vps_dec_pic_buffering_minus1[i][k][max_sub_layers_vps_minus1[k]]. 
     The value of max_vps_dec_pic_buffering_minus1[i][0][j] for each value of i and j is inferred to be equal to vps_max_dec_pic_buffering_minus1[j]. 
     Referring to  FIG.  55    the oop_dpb_maxbuffering_parameters specifies sub_layer_vps_buf_info_present_flag[i][k], max_vps_dec_pic_buffering_minus1[i][k][j].  FIG.  55    is a variant syntax for oop_dpb_maxbuffering_parameters compared to the syntax in  FIG.  54    for oop_dpb_maxbuffering_parameters. 
     The variable MaxSubLayers[setId][k] for setId in the range of 0 to num_dpb_info_parameters−1, inclusive, is derived as follows: 
     
       
         
           
               
             
               
                 TABLE 29 
               
               
                   
               
             
            
               
                 for( setId = 0; setId &lt; num_dpb_info_parameters; setId++ ) { 
               
               
                    for( k = 1; k &lt;= vps_max_layers_minus1; i++ ) { 
               
               
                    MaxSubLayers[setId][k] =( max_sub_layers_vps_minus1[k]+1 ) 
               
               
                    } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     In this case the oop_dpb_maxbuffering_parameters parameters (i, k) will be defined as in the  FIG.  55   . 
     Referring to  FIG.  56   , an exemplary modified vps_extension is illustrated. The modified vps extension includes further modification of the syntax in  FIG.  52    with new syntax., In  FIG.  53    in this variant oop_dpb_maxbuffering_parameters(i,j) are signalled for each layer j for the particular output layer set i compared to  FIG.  52    which signals a single set of oop_dpb_maxbuffering_parameters(i) parameters for the highest layer id in the output layer set i. 
     The oop_dpb_maxbuffring_parameters(I,k) are as shown in  FIG.  57   . 
     Referring to  FIG.  58    the oop_dpb_maxbuffering_parameters specifies sub_layer_vps_buf_info_present_flag[i][k], max_vps_dec_pic_buffering_minus1[i][k][j].  FIG.  58    is a variant syntax for oop_dpb_maxbuffering_parameters compared to the syntax in  FIG.  57    for oop_dpb_maxbuffering_parameters. 
     The variable MaxSubLayers[setId][k] for setId in the range of 0 to num_dpb_info_parameters−1, inclusive, is derived as follows: 
     
       
         
           
               
             
               
                 TABLE 30 
               
               
                   
               
             
            
               
                 for( setId = 0; setId &lt; num_dpb_info_parameters; setId++ ) { 
               
               
                    for( k = 1; k &lt;= vps_max_layers_minus1; i++ ) { 
               
               
                    MaxSubLayers[setId][k] = ( max_sub_layers_vps_minus1[k]+1 ) 
               
               
                    } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     In this case the oop_dpb_maxbuffering_parameters parameters (i, k) will be defined as in the  FIG.  58   . 
     Referring to  FIG.  59   , an exemplary modified vps_extension is illustrated. The modified vps extension includes further modification of the syntax in  FIG.  56    with new syntax, namely, an additional flag layer_dpb_info_parameters_presence_flag which are conditionally signalled. layer_dpb_info_parameters_presence_flag makes signalling of layer_dpb_info_parameters(i) in VPS extension optional. 
     layer_dpb_info_parameters_presence_flag[i] equal to 1 specifies that the syntax elements sub_layer_vps_ordering_info_predict_flag[i] and layer_dpb_info_parameters(i) are present for vps_max_num_layers_minus1 layers. layer_dpb_info_parameters_presence_flag[i] equal to 0 specifies that the syntax elements sub_layer_vps_ordering_info_predict_flag[i] and layer_dpb_info_parameters(i) are not present for vps_max_num_layers_minus1 layers. 
     The oop_dpb_maxbuffring_parameters(i,k) are as shown in  FIG.  60   . 
     Referring to  FIG.  61    the oop_dpb_maxbuffering_parameters specifies sub_layer_vps_buf_info_present_flag[i][k], max_vps_dec_pic_buffering_minus1[i][k][j].  FIG.  61    is a variant syntax for oop_dpb_maxbuffering_parameters compared to the syntax in  FIG.  60    for oop_dpb_maxbuffering_parameters. 
     The variable MaxSubLayers[setId][k] for setId in the range of 0 to num_dpb_info_parameters−1, inclusive, is derived as follows: 
     
       
         
           
               
             
               
                 TABLE 31 
               
               
                   
               
             
            
               
                 for( setId = 0; setId &lt; num_dpb_info_parameters; setId++ ) { 
               
               
                    for( k = 1; k &lt;= vps_max_layers_minus1; i++ ) { 
               
               
                    MaxSubLayers[setId][k] =( max_sub_layers_vps_minus1[k]+1 ) 
               
               
                    } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     In this case the oop_dpb_maxbuffering_parameters parameters (i, k) will be defined as in the  FIG.  61   . 
     An exemplary alternative for the syntax in VPS extension is that 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 32 
               
               
                   
                   
               
             
            
               
                   
                   
                 for( k = 1; j &lt;= vps_max_layers_minus1; k++ ) 
               
               
                   
                   
                  oop_dpb_maxbuffering_parameters(k) 
               
               
                   
                   
               
            
           
         
       
     
     may be changed to 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 33 
               
               
                   
                   
               
             
            
               
                   
                   
                 for( k = 0; k &lt;= vps_max_layers_minus1; k++ ) 
               
               
                   
                   
                  oop_dpb_maxbuffering_parameters(k) 
               
               
                   
                   
               
            
           
         
       
     
     Thus index k could start at 0 instead of at 1. 
     An exemplary alternative for the syntax in VPS extension is that 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 34 
               
               
                   
                   
               
             
            
               
                   
                   
                 for( k = 0; k &lt;= vps_max_layers_minus1; k++ ) 
               
               
                   
                   
                  oop_dpb_maxbuffering_parameters(k) 
               
               
                   
                   
               
            
           
         
       
     
     may be changed to 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 35 
               
               
                   
                   
               
             
            
               
                   
                   
                 for( k = 0; k &lt;= vps_max_layers_minus1; k++ ) 
               
               
                   
                   
                  oop_dpb_maxbuffering_parameters(k) 
               
               
                   
                   
               
            
           
         
       
     
     The vps_max_layer_id specifies the maximum allowed value of nuh_layer_id of all NAL units in the CVS. The vps_max_layers_minus1, specifies the maximum number of layers that may be present in the CVS, wherein a layer may e.g. be a spatial scalable layer, a quality scalable layer, a texture view or a depth view. 
     Another exemplary alternative for the syntax in VPS extension is that 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 36 
               
               
                   
                   
               
             
            
               
                   
                   
                 for( k = 1; k &lt;= vps_max_layers_minus1; k++ ) 
               
               
                   
                   
                  oop_dpb_maxbuffering_parameters(I,k) 
               
               
                   
                   
               
            
           
         
       
     
     may be changed to 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 37 
               
               
                   
                   
               
             
            
               
                   
                   
                 for( k = 1; k &lt; numOutputLayers; k++ ) 
               
               
                   
                   
                  oop_dpb_maxbuffering_parameters(I,k) 
               
               
                   
                   
               
            
           
         
       
     
     where numOutputLayers is derived as 
     
       
         
           
               
             
               
                 TABLE 38 
               
               
                   
               
             
            
               
                 for( setId = 0; setId &lt; num_dpb_info_parameters; setId++ ) { 
               
               
                    lsIdx = 
               
               
                 output_layer_set_idx_minus1[ output_point_layer_set_idx[ setId ] ] + 1 
               
               
                    numOutputLayers = [ numLayersInIdList[ lsIdx ] − 1 ] 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     or it could be changed to 
     
       
         
           
               
               
             
               
                 TABLE 39 
               
               
                   
               
             
            
               
                   
                 for( k = 1; k &lt;= 
               
               
                   
                 numLayersInIdList[output_layer_set_idx_minus1[output_ 
               
               
                   
                 point_layer_set_idx[ i ] ]]-1; i++ ) { 
               
               
                   
                  oop_dpb_maxbuffering_parameters( i, k ) 
               
               
                   
               
            
           
         
       
     
     In one embodiment an additional flag maybe signalled to indicate if oop_dpb_information_parameters are signalled for the particular layer as follows: 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 40 
               
               
                   
                   
               
             
            
               
                   
                 for( k = 1; k &lt;= vps_max_layers_minus1; i++ ) { 
                   
               
               
                   
                  vps_layer_info_present_flag[ k ] 
                 u(1)  
               
               
                   
                  oop_dpb_maxbuffering_parameters( i, k )  
                   
               
               
                   
                 } 
               
               
                   
                   
               
            
           
         
       
     
     vps_layer_info_present_flag[k] equal to 1 specifies that oop_dpb_maxbuffering_parameters are present for the k&#39;th layer for the particular output layer set. vps_layer_info_present_flag[k] equal to 0 specifies that oop_dpb_maxbuffering_parameters are not present for the k&#39;th layer for the particular output layer set. 
     The syntax elements of non-VCL NAL units (or their default values for some of the syntax elements), required for the HRD, are specified in the semantic subclauses of clause 7, Annexes D and E. 
     Two types of HRD parameter sets (NAL HRD parameters and VCL HRD parameters) are used. The HRD parameter sets are signalled through the hrd_parameters( ) syntax structure, which may be part of the SPS syntax structure or the VPS syntax structure. 
     Multiple tests may be needed for checking the conformance of a bitstream, which is referred to as the bitstream under test. For each test, the following steps apply in the order listed: 
     (1) An output layer set under test, denoted as TargetOpLs is selected. The operation point referred in TargetOpLs by output_layer_set_idx[ ] identifies the operation point under test. The output layer identifier list OpLayerIdList of TargetOpLs consists of the list of nuh_layer_id values, in increasing order of nuh_layer_id values, present in the bitstream subset associated with TargetOp and TargetOpLs, which is a subset of the nuh_layer_id values present in the bitstream under test. The OpTid of TargetOp is equal to the highest TemporalId present in the bitstream subset associated with TargetOp. 
     (2) TargetDecLayerIdList is set equal to target decoded layer identifier list targetDLayerIdList for the selected output layer set TargetOpLs, HighestTid is set equal to OpTid of TargetOp, and the sub-bitstream extraction process as specified in clause 10 is invoked with the bitstream under test, HighestTid, and TargetDecLayerIdList as inputs, and the output is assigned to BitstreamToDecode. 
     (3) The hrd_parameters(j) syntax structure and the sub_layer_hrd_parameters( ) syntax structure applicable to TargetOp are selected. If TargetDecLayerIdList contains all nuh_layer_id values present in the bitstream under test, the hrd_parameters( ) syntax structure in the active SPS (or provided through an external means not specified in this Specification) is selected. Otherwise, the hrd_parameters( ) syntax structure in the active VPS (or provided through some external means not specified in this Specification) that applies to TargetOp is selected. Within the selected hrd_parameters( ) syntax structure, if BitstreamToDecode is a Type I bitstream, the sub_layer_hrd_parameters(HighestTid) syntax structure that immediately follows the condition “if(vcl_hrd_parameters_present_flag)” is selected and the variable NalHrdModeFlag is set equal to 0; otherwise (BitstreamToDecode is a Type II bitstream), the sub_layer_hrd_parameters(HighestTid) syntax structure that immediately follows either the condition “if(vcl_hrd_parameters_present_flag)” (in this case the variable NalHrdModeFlag is set equal to 0) or the condition “if(nal_hrd_parameters_present_flag)” (in this case the variable NalHrdModeFlag is set equal to 1) is selected. When BitstreamToDecode is a Type II bitstream and NalHrdModeFlag is equal to 0, all non-VCL NAL units except filler data NAL units, and all leading_zero_8bits, zero_byte, start_code_prefix_one_3 bytes, and trailing_zero_8bits syntax elements that form a byte stream from the NAL unit stream (as specified in Annex B), when present, are discarded from BitstreamToDecode, and the remaining bitstream is assigned to BitstreamToDecode. 
     A conforming decoder may fulfil all requirements specified in this subclause. 
     (1) A decoder claiming conformance to a specific profile, tier and level shall be able to successfully decode all bitstreams that conform to the bitstream conformance requirements specified in subclause C.4, in the manner specified in Annex A, provided that all VPSs, SPSs and PPSs referred to in the VCL NAL units, and appropriate buffering period and picture timing SEI messages are conveyed to the decoder, in a timely manner, either in the bitstream (by non-VCL NAL units), or by external means not specified in this Specification. 
     (2) When a bitstream contains syntax elements that have values that are specified as reserved and it is specified that decoders shall ignore values of the syntax elements or NAL units containing the syntax elements having the reserved values, and the bitstream is otherwise conforming to this Specification, a conforming decoder shall decode the bitstream in the same manner as it would decode a conforming bitstream and shall ignore the syntax elements or the NAL units containing the syntax elements having the reserved values as specified. 
     There are two types of conformance of a decoder: output timing conformance and output order conformance. 
     To check conformance of a decoder, test bitstreams conforming to the claimed profile, tier and level, as specified in subclause C.4 are delivered by a hypothetical stream scheduler (HSS) both to the HRD and to the decoder under test (DUT). All cropped decoded pictures output by the HRD shall also be output by the DUT, each cropped decoded picture output by the DUT shall be a picture with PicOutputFlag equal to 1, and, for each such cropped decoded picture output by the DUT, the values of all samples that are output shall be equal to the values of the samples produced by the specified decoding process. 
     For output timing decoder conformance, the HSS operates as described above, with delivery schedules selected only from the subset of values of SchedSelIdx for which the bit rate and CPB size are restricted as specified in Annex A for the specified profile, tier and level, or with “interpolated” delivery schedules as specified below for which the bit rate and CPB size are restricted as specified in Annex A. The same delivery schedule is used for both the HRD and the DUT. 
     When the HRD parameters and the buffering period SEI messages are present with cpb_cnt_minus1[HighestTid] greater than 0, the decoder shall be capable of decoding the bitstream as delivered from the HSS operating using an “interpolated” delivery schedule specified as having peak bit rate r, CPB size c(r), and initial CPB removal delay
 
( f ( r )÷ r )  [Math. 16]
 
     as follows: 
     
       
         
           
               
               
             
               
                 TABLE 41 
               
               
                   
               
             
            
               
                 α = ( r − BitRate[ SchedSelIdx − 1 ] ) + ( BitRate[ SchedSelIdx ] − BitRate[ SchedSelIdx − 1 ] ),  
                 (C-22) 
               
               
                 c( r ) = α * CpbSize[ SchedSelIdx ] + (1 − α) * CpbSize[ SchedSelIdx − 1 ],  
                 (C-23) 
               
               
                 f( r ) = α * InitCpbRemovalDelay[ SchedSelIdx ] * BitRate[ SchedSelIdx ] + 
                   
               
               
                     ( 1 − α )* InitCpbRemovalDelay[ SchedSelIdx − 1 ] * BitRate[ SchedSelIdx − 1 ] 
                 (C-24) 
               
               
                   
               
            
           
         
       
     
     for any SchedSelIdx&gt;0 and r such that BitRate[SchedSelIdx−1]&lt;=r&lt;=BitRate[SchedSelIdx] such that r and c(r) are within the limits as specified in Annex A for the maximum bit rate and buffer size for the specified profile, tier and level. The InitCpbRemovalDelay[SchedSelIdx] can be different from one buffering period to another and have to be re-calculated. 
     For output timing decoder conformance, an HRD as described above is used and the timing (relative to the delivery time of the first bit) of picture output is the same for both the HRD and the DUT up to a fixed delay. 
     For output order decoder conformance, the following applies: 
     (1) The HSS delivers the bitstream BitstreamToDecode to the DUT “by demand” from the DUT, meaning that the HSS delivers bits (in decoding order) only when the DUT requires more bits to proceed with its processing. This means that for this test, the coded picture buffer of the DUT could be as small as the size of the largest decoding unit. 
     (2) A modified HRD as described below is used, and the HSS delivers the bitstream to the HRD by one of the schedules specified in the bitstream BitstreamToDecode such that the bit rate and CPB size are restricted as specified in Annex A. The order of pictures output shall be the same for both the HRD and the DUT. 
     (3) The HRD CPB size is given by CpbSize[SchedSelIdx] as specified in subclause E.2.3, where SchedSelIdx and the HRD parameters are selected as specified in subclause C.1. The DPB size is given by sps_max_dec_pic_buffering_minus1[HighestTid]+1 from the active SPS (when nuh_layer_id for the current decoded picture is equal to 0) or from the active layer SPS for the value of nuh_layer_id of the current decoded picture. 
     In some cases if output layer sets DPB information parameters oop_dpb_maxbuffering_parameters(j) are present for the selected output layer set, The DPB size is given by max_vps_dec_pic_buffering_minus1[CurrLayerId][HighestTid] where currLayerId is the nuh_layer_id of the current decoded picture. Otherwise if output layer sets DPB information parameters oop_dpb_maxbuffering_parameters ( ) are not present for the selected output layer set, the DPB Size is given by sps_max_dec_pic_buffering_minus1[HighestTid]+1 from the active SPS (when nuh_layer_id for the current decoded picture is equal to 0) or from the active layer SPS for the value of nuh_layer_id of the current decoded picture.) 
     The removal time from the CPB for the HRD is the final bit arrival time and decoding is immediate. The operation of the DPB of this HRD is as described in subclauses C.5.2 through C.5.2.3. 
     The decoded picture buffer contains picture storage buffers. The number of picture storage buffers for nuh_layer_id equal to 0 is derived from the active SPS. The number of picture storage buffers for each non-zero nuh_layer_id value is derived from the active layer SPS for that non-zero nuh_layer_id value. Each of the picture storage buffers contains a decoded picture that is marked as “used for reference” or is held for future output. The process for output and removal of pictures from the DPB as specified in subclause F.13.5.2.2 is invoked, followed by the invocation of the process for picture decoding, marking, additional bumping, and storage as specified in subclause F.13.5.2.3. The “bumping” process is specified in subclause F.13.5.2.4 and is invoked as specified in subclauses F.13.5.2.2 and F.13.5.2.3. 
     The output and removal of pictures from the DPB before the decoding of the current picture (but after parsing the slice header of the first slice of the current picture) happens instantaneously when the first decoding unit of the access unit containing the current picture is removed from the CPB and proceeds as follows. 
     The decoding process for RPS as specified in subclause 8.3.2 is invoked. 
     (1) If the current picture is an IRAP picture with NoRaslOutputFlag equal to 1 and with nuh_layer_id equal to 0 that is not picture 0, the following ordered steps are applied: 
     (A) The variable NoOutputOfPriorPicsFlag is derived for the decoder under test as follows: 
     (i) If the current picture is a CRA picture, NoOutputOfPriorPicsFlag is set equal to 1 (regardless of the value of no_output_of_prior_pics_flag). 
     (ii) Otherwise, if the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps_max_dec_pic_buffering_minus1[HighestTid] derived from the active SPS is different from the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps_max_dec_pic_buffering_minus1[HighestTid], respectively, derived from the SPS active for the preceding picture, NoOutputOfPriorPicsFlag may (but should not) be set to 1 by the decoder under test, regardless of the value of no_output_of_prior_pics_flag. Although setting NoOutputOfPriorPicsFlag equal to no_output_of_prior_pics_flag is preferred under these conditions, the decoder under test is allowed to set NoOutputOfPriorPicsFlag to 1 in this case. 
     (iii) Otherwise, NoOutputOfPriorPicsFlag is set equal to no_output_of_prior_pics_flag. 
     (B) The value of NoOutputOfPriorPicsFlag derived for the decoder under test is applied for the HRD as follows: 
     (i) If NoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers in the DPB are emptied without output of the pictures they contain, and the DPB fullness is set equal to 0. 
     (ii) Otherwise (NoOutputOfPriorPicsFlag is equal to 0), all picture storage buffers containing a picture that is marked as “not needed for output” and “unused for reference” are emptied (without output), and all non-empty picture storage buffers in the DPB are emptied by repeatedly invoking the “bumping” process specified in subclause F.13.5.2.4, and the DPB fullness is set equal to 0. 
     (iii) Otherwise (the current picture is not an IRAP picture with NoRaslOutputFlag equal to 1 and with nuh_layer_id equal to 0), all picture storage buffers containing a picture which are marked as “not needed for output” and “unused for reference” are emptied (without output). For each picture storage buffer that is emptied, the DPB fullness is decremented by one. The variable currLayerId is set equal to nuh_layer_id of the current decoded picture. 
     The variables MaxNumReorderPics[currLayerId][HighestTid], MaxLatencyIncreasePlus1[currLayerId][HighestTid], MaxLatencyPictures[currLayerId][HighestTid], MaxDecPicBufferingMinus1[currLayerId][HighestTid] are derived as follows: 
     If layer DPB information parameters layer_dpb_info_parameters(j) are present in VPS, MaxNumReorderPics[currLayerId][HighestTid] is set to vps_max_num_reorder_pics[HighestTid] when currLayerId is equal to 0 or is set to max_vps_num_reorder_pics[CurrLayerId][HighestTid] for the currLayerId when currLayerId is greater than 0. Otherwise if layer DPB information parameters layer_dpb_info_parameters(j) are not present MaxNumReorderPics[currLayerId][HighestTid] is set to sps_max_num_reorder_pics[HighestTid] from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId. 
     If layer DPB information parameters layer_dpb_info_parameters(j) are present in VPS, MaxLatencyIncreasePlus1[currLayerId][HighestTid] is set to vps_max_latency_increase_plus1[HighestTid] when currLayerId is equal to 0 or is set to max_vps_latency_increase_plus1[CurrLayerId][HighestTid] for the currLayerId when currLayerId is greater than 0. If layer DPB information parameters layer_dpb_info_parameters(j) are present in VPS, MaxLatencyPictures[currLayerId][HighestTid] is set to SpsMaxLatencyPictures [HighestTid] when currLayerId is equal to 0 or is set to VpsMaxLatencyPictures [CurrLayerId][HighestTid] for the currLayerId when currLayerId is greater than 0. Otherwise if layer DPB information parameters layer_dpb_info_parameters(o are not present for the for the operation point under test, MaxLatencyIncreasePlus1[currLayerId][HighestTid] is set to sps_max_latency_increase_plus1[HighestTid] of the active SPS (when currLayerId is equal to 0) or the active layer SPS for the value of currLayerId and MaxLatencyPictures[currLayerId][HighestTid] is set to SpsMaxLatencyPictures[currLayerId][HighestTid] derived from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId. 
     If operation point DPB information parameters oop_dpb_maxbuffering_parameters( ) are present for the selected output layer set, MaxDecPicBufferingMinus1[currLayerId][HighestTid] is set to vps_max_dec_pic_buffering_minus1[HighestTid] when currLayerId is equal to 0 or is set to max_vps_dec_pic_buffering_minus1[CurrLayerId][HighestTid] for the currLayerId for the operation point under test when currLayerId is greater than 0. Otherwise if operation point DPB information parameters oop_dpb_maxbuffering_parameters (are not present for the operation point under test, MaxDecPicBufferingMinus1[currLayerId][HighestTid] is set to sps_max_dec_pic_buffering_minus1[HighestTid] from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId. 
     When one or more of the following conditions are true, the “bumping” process specified in subclause F.13.5.2.4 is invoked repeatedly while further decrementing the DPB fullness by one for each additional picture storage buffer that is emptied, until none of the following conditions are true: 
     (1) The number of pictures with nuh_layer_id equal to currLayerId in the DPB that are marked as “needed for output” is greater than MaxNumReorderPics[CurrLayerId][HighestTid]. 
     (2) If MaxLatencyIncreasePlus1[CurrLayerId][HighestTid] is not equal to 0 and there is at least one picture with nuh_layer_id equal to currLayerId in the DPB that is marked as “needed for output” for which the associated variable PicLatencyCount[currLayerId] is greater than or equal to MaxLatencyPictures[CurrLayerId][HighestTid]. 
     (3) The number of pictures with nuh_layer_id equal to currLayerId in the DPB is greater than or equal to MaxDecPicBuffering[CurrLayerId][HighestTid]. 
     The processes specified in this subclause happen instantaneously when the last decoding unit of access unit n containing the current picture is removed from the CPB. 
     The variable currLayerId is set equal to nuh_layer_id of the current decoded picture. 
     For each picture in the DPB that is marked as “needed for output” and that has a nuh_layer_id value equal to currLayerId, the associated variable PicLatencyCount[currLayerId] is set equal to PicLatencyCount[currLayerId]+1. 
     The current picture is considered as decoded after the last decoding unit of the picture is decoded. The current decoded picture is stored in an empty picture storage buffer in the DPB, and the following applies: 
     (A) If the current decoded picture has PicOutputFlag equal to 1, it is marked as “needed for output” and its associated variable PicLatencyCount[currLayerId] is set equal to 0. 
     (B) Otherwise (the current decoded picture has PicOutputFlag equal to 0), it is marked as “not needed for output”. 
     The current decoded picture is marked as “used for short-term reference”. 
     When one or more of the following conditions are true, the “bumping” process specified in subclause F.13.5.2.4 is invoked repeatedly until none of the following conditions are true. 
     (A) The number of pictures with nuh_layer_id equal to currLayerId in the DPB that are marked as “needed for output” is greater than MaxNumReorderPics[CurrLayerId][HighestTid]. 
     (B) MaxLatencyIncreasePlus1[CurrLayerId][HighestTid] is not equal to 0 and there is at least one picture with nuh_layer_id equal to currLayerId in the DPB that is marked as “needed for output” for which the associated variable PicLatencyCount[currLayerId] is greater than or equal to MaxLatencyPictures[CurrLayerId][HighestTid]. 
     The “bumping” process consists of the following ordered steps: 
     (A) The pictures that are first for output are selected as the ones having the smallest value of PicOrderCntVal of all pictures in the DPB marked as “needed for output”. 
     (B) These pictures are cropped, using the conformance cropping window specified in the active SPS for the picture with nuh_layer_id equal to 0 or in the active layer SPS for a nuh_layer_id value equal to that of the picture, the cropped pictures are output in ascending order of nuh_layer_id, and the pictures are marked as “not needed for output”. 
     (C) Each picture storage buffer that contains a picture marked as “unused for reference” and that included one of the pictures that was cropped and output is emptied. 
     Referring to  FIG.  62   , an exemplary modified sequence parameter set (sps) syntax seq_parameter_set_rbsp is illustrated. The modified sps includes a sps_dpb_params_present_flag. In one embodiment based on the value of this flag and based on the value of nuh_layer_id some of the syntax elements (e.g. sps_sub_layer_ordering_info_present_flag, sps_max_dec_pic_buffering_minus1[i], sps_max_num_reorder_pics[i], sps_max_latency_incease_plus1[i] may not be signaled. 
     sps_dpb_params_present_flag equal to 0 specifies that, for SPS with nuh_layer_id&gt;0 the syntax elements sps_sub_layer_ordering_info_present_flag, sps_max_dec_pic_buffering_minus1[i], sps_max_num_reorder_pics[i], sps_max_latency_increase_plus1[i] are not present in this SPS. The value of these parameters is set equal to the value of sub_layer_vps_buf_info_present_flag[i], max_vps_num_reorder_pics[i][j] and max_vps_latency_increase_plus1[i][j] parameters signaled in active VPS extension. sps_dpb_params_present_flag equal to 1 specifies that, for SPS with nuh_layer_id&gt;0 the syntax elements sps_sub_layer_ordering_info_present_flag, sps_max_dec_pic_buffering_minus1[i], sps_max_num_reorder_pics[i], sps_max_latency_increase_plus1[i] are present in this SPS. 
     In another embodiment one or more of the syntax elements may be signaled using a known fixed number of bits instead of u(v) instead of ue(v). For example they could be signaled using u(8) or u(16) or u(32) or u(64), etc. 
     In another embodiment one or more of these syntax element could be signaled with ue(v) or some other coding scheme instead of fixed number of bits such as u(v) coding. 
     In another embodiment the names of various syntax elements and their semantics may be altered by adding a plus1 or plus2 or by subtracting a minus1 or a minus2 compared to the described syntax and semantics. 
     In yet another embodiment various syntax elements may be signaled per picture anywhere in the bitstream. For example they may be signaled in slice segment header, pps/sps/vps/or any other parameter set or other normative part of the bitstream. 
     In yet another embodiments all the concepts defined in this invention related to output layer sets could be applied to output operation points [2,3] and/or to operation points [1]. 
     Example 3 
     A method for video coding is disclosed. The method includes beginning to parse a first slice header of a current picture. It is determined which steps performed by a decoded picture buffer (DPB) will be picture based and which steps will be access unit (AU) based. A removal from the DPB is performed. A picture output from the DPB is performed. A decoding and storing of a current decoded picture in the DPB are performed. The current decoded picture in the DPB is marked. An additional picture output from the DPB is also performed. 
     In some configurations, the removal and the output from the DPB may be based on at least one AU output flag, such as an AU output flag, an AU no rasl output flag and/or an AU no output of prior pictures flag. The AU output flag may be derived based on syntax elements signaled in the bitstream and other conditions. The AU flags represent flags derived and applied at access unit (AU) level. In some cases, these will be flags different than similar flags which are signaled or derived at picture level, such as a picture output flag (e.g., pic_output_flag), a picture no rasl output flag (e.g., NoRaslOutputFlag) and/or a picture no output of prior pictures flag (e.g., no_output_of_prior_pics flag). 
     In one configuration, a first AU output flag may be derived and used by the DPB and a second AU output flag is derived and used by the DPB. In another configuration, all picture output flag syntax element values may be constrained to the same value for all coded pictures in an AU when a picture output flag is present in the first slice header. In some configurations, all picture output flag syntax element values may be constrained to the same value for all coded pictures in an AU when a no picture output flag is present in the first slice header. 
     In one configuration, the removal may be picture based, the picture output may be AU (access unit) based, the storing and decoding may be picture based, the marking may be picture based, and the additional picture output may be AU based. The removal from the DPB may remove one or more pictures from the DPB before decoding of the current picture. 
     In another configuration, the removal may be picture based, and the picture output, the decoding and storing, the marking and the additional picture output may be AU based. In yet another configuration, the removal, the picture output, the decoding and storing, the marking and the additional picture output may be AU based. In another configuration, the removal, the decoding and storing and the marking may be picture based, and the picture output and the additional picture output may be AU based. In yet another configuration, the removal, the picture output, the decoding and storing, the marking and the additional picture output may be picture based. 
     Marking the current decoded picture in the DPB may include a reference marking step and an output marking step. The reference marking step may be picture based and the output marking step may be AU based. A DPB fullness may be incremented by one when a decoded picture is stored in the DPB in an empty storage buffer. The DPB fullness may be decremented by one when a picture is output from the DPB. The DPB fullness may be tracked per layer. The DPB fullness may also be tracked for an output layer set. 
     The DPB may include separately identified and managed picture buffers for decoded pictures having one or more of different resolutions, different bit-depths and different color chromaticity. The DPB may include a common pool of picture storage buffers. A decoded picture may be stored in the picture storage buffers based on at least one of size, resolution and bit-depth. In one configuration, a decoded picture may be stored in one picture buffer slot of the picture storage buffers. 
     The method may be performed by a decoder within an electronic device that conforms to a scalable high efficiency video coding (SHVC) standard. The method may also be performed by a decoder within an electronic device that conforms to a multi-view high efficiency video coding (MV-HEVC) standard. 
     An electronic device configured for video coding is also disclosed. The electronic device includes a processor and memory in electronic communication with the processor. Instructions in the memory are executable to begin to parse a first slice header of a current picture. Instructions in the memory are also executable to determine which steps performed by a decoded picture buffer (DPB) will be picture based and which steps will be access unit (AU) based. Instructions in the memory are further executable to perform a removal from the DPB. Instructions in the memory are also executable to perform a picture output from the DPB. Instructions in the memory are further executable to perform a decoding and storing of a current decoded picture in the DPB. Instructions in the memory are also executable to mark the current decoded picture in the DPB. Instructions in the memory are further executable to perform an additional picture output from the DPB. 
     Various configurations are now described with reference to the Figures, where like reference numbers may indicate functionally similar elements. The systems and methods as generally described and illustrated in the Figures herein could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of several configurations, as represented in the Figures, is not intended to limit scope, as claimed, but is merely representative of the systems and methods. 
       FIG.  63    is a block diagram illustrating video coding between multiple electronic devices  2102   a - b . A first electronic device  2102   a  and a second electronic device  2102   b  are illustrated. However, it should be noted that one or more of the features and functionality described in relation to the first electronic device  2102   a  and the second electronic device  2102   b  may be combined into a single electronic device  102  in some configurations. Each electronic device  102  may be configured to encode video and/or decode video. The electronic devices  102  may be configured to use hybrid decoded picture buffer (DPB) operation. Hybrid decoded picture buffer (DPB) operation refers to scenarios where the various steps of removal, output (bumping), storage, marking and additional output (bumping) performed on a decoded picture buffer (DPB)  116  happen on either a picture basis or an access unit (AU) basis. Although specific combinations of these steps are referred to as being performed on a picture basis or an access unit (AU) basis, all possible combinations of doing each of these steps individually on either a picture basis or an access unit (AU) basis are supported. 
     As used herein, access unit (AU) refers to a set of network abstraction layer (NAL) units that are associated with each other according to a specified classification rule, that are consecutive in decoding order, and that include the video coding layer (VCL) NAL units of all coded pictures associated with the same output time and their associated non-VCL NAL units. The base layer is a layer in which all VCL NAL units have a nuh_layer_id equal to 0. A coded picture is a coded representation of a picture that includes VCL NAL units with a particular value of nuh_layer_id and that includes all the coding tree units of the picture. In some cases, a coded picture may be called a layer component. Addition details about steps being picture based or access unit (AU) based are given in relation to  FIGS.  69  and  70    below. 
     In one configuration, each of the electronic devices  102  may conform to the High Efficiency Video Coding (HEVC) standard, the Scalable High Efficiency Video Coding (SHVC) standard or the Multi-view High Efficiency Video Coding (MV-HEVC) standard. The HEVC standard is a video compression standard that acts as a successor to H.264/MPEG-4 AVC (Advanced Video Coding) and that provides improved video quality and increased data compression ratios. As used herein, a picture is an array of luma samples in monochrome format or an array of luma samples and two corresponding arrays of chroma samples in 4:2:0, 4:2:2 and 4:4:4 colour format or some other colour format. The operation of a hypothetical reference decoder (HRD) and the operation of the output order decoded picture buffer (DPB)  116  are described for SHVC and MV-HEVC in JCTVC-M1008, JCTVC-L1008, JCTVC-D1004, JCT3V-C1004, JCTVC-L0453 and JCTVC-L0452. 
     The first electronic device  2102   a  may include an encoder  2108  and an overhead signaling module  2112 . The first electronic device  2102   a  may obtain an input picture  2106 . In some configurations, the input picture  2106  may be captured on the first electronic device  2102   a  using an image sensor, retrieved from memory and/or received from another electronic device  102 . The encoder  2108  may encode the input picture  2106  to produce encoded data  2110 . For example, the encoder  2108  may encode a series of input pictures  2106  (e.g., video). The encoded data  2110  may be digital data (e.g., a bitstream). 
     The overhead signaling module  2112  may generate overhead signaling based on the encoded data  2110 . For example, the overhead signaling module  2112  may add overhead data to the encoded data  2110  such as slice header information, video parameter set (VPS) information, sequence parameter set (SPS) information, picture parameter set (PPS) information, picture order count (POC), reference picture designation, etc. In some configurations, the overhead signaling module  2112  may produce a wrap indicator that indicates a transition between two sets of pictures. 
     The encoder  2108  (and overhead signaling module  2112 , for example) may produce a bitstream  2114 . The bitstream  2114  may include encoded picture data based on the input picture  2106 . In some configurations, the bitstream  2114  may also include overhead data, such as slice header information, VPS information, SPS information, PPS information, etc. As additional input pictures  2106  are encoded, the bitstream  2114  may include one or more encoded pictures. For instance, the bitstream  2114  may include one or more encoded reference pictures and/or other pictures. 
     The bitstream  2114  may be provided to a decoder  2104 . In one example, the bitstream  2114  may be transmitted to the second electronic device  2102   b  using a wired or wireless link. In some cases, this may be done over a network, such as the Internet or a Local Area Network (LAN). As illustrated in  FIG.  63   , the decoder  2104  may be implemented on the second electronic device  2102   b  separately from the encoder  2108  on the first electronic device  2102   a . However, it should be noted that the encoder  2108  and decoder  2104  may be implemented on the same electronic device  102  in some configurations. When the encoder  2108  and decoder  2104  are implemented on the same electronic device, for instance, the bitstream  2114  may be provided over a bus to the decoder  2104  or stored in memory for retrieval by the decoder  2104 . 
     The decoder  2104  may receive (e.g., obtain) the bitstream  2114 . The decoder  2104  may generate a decoded picture  2118  (e.g., one or more decoded pictures  2118 ) based on the bitstream  2114 . The decoded picture  2118  may be displayed, played back, stored in memory and/or transmitted to another device, etc. 
     The decoder  2104  may include a decoded picture buffer (DPB)  116 . The decoded picture buffer (DPB)  116  may be a buffer holding decoded pictures for reference, output reordering or output delay specified for a hypothetical reference decoder (HRD). On an electronic device  102 , a decoded picture buffer (DPB)  116  may be used to store reconstructed (e.g., decoded) pictures at a decoder  2104 . These stored pictures may then be used, for example, in an inter-prediction mechanism. When pictures are decoded out of order, the pictures may be stored in the decoded picture buffer (DPB)  116  so they can be displayed later in order. 
     In the H.264 or advance video coding (AVC) standard, decoded picture buffer (DPB)  116  management (e.g., deletion, addition of pictures, reordering of pictures, etc.) is carried out using memory management control operations (MMCO). Many different decoded picture buffer (DPB)  116  management approaches are under consideration. 
     The decoder  2104  may include a hybrid decoded picture buffer (DPB) operation module  2120 . The hybrid decoded picture buffer (DPB) operation module  2120  may allow for decoded picture buffer (DPB)  116  management approaches with picture basis steps  2122  and/or decoded picture buffer (DPB)  116  management approaches with access unit (AU) based steps  2124 . For example, one advantage of the use of picture based steps  2124  for removal, storage and reference marking is that optimal decoded picture buffer (DPB)  116  memory will be used by various layers. Thus, the overall required memory when using picture based steps may be lower. One advantage of the use of access unit (AU) based steps  2124  for output (including output, output marking and additional output) is that the output process may be simplified. 
       FIG.  64    is a flow diagram of a method  2200  for hybrid decoded picture buffer (DPB)  116  operation. The method  2200  may be performed by a decoded picture buffer (DPB)  116  as part of a decoder  2104  on an electronic device  102 . In one configuration, the method  2200  may be performed by a hybrid decoded picture buffer (DPB) operation module  2120 . The decoded picture buffer (DPB)  116  may begin parsing  2202  a first slice header of a current picture. The decoded picture buffer (DPB)  116  may determine  2204  which steps of the hybrid decoded picture buffer (DPB) operation will be picture based and which steps will be access unit (AU) based. 
     The decoded picture buffer (DPB)  116  may perform  2206  a removal (without output) from the decoded picture buffer (DPB)  116 . The removal may remove pictures from the decoded picture buffer (DPB)  116  before the decoding of the current picture. The decoded picture buffer (DPB)  116  may perform  2208  a picture output (bumping) from the decoded picture buffer (DPB)  116 . A picture output (bumping) may refer to the output of pictures from the decoded picture buffer (DPB)  116  at the coded picture buffer (CPB) removal time. In some configurations, the term bumping may be used to indicate the output of one or more pictures from the decoded picture buffer (DPB)  116 . Thus, the terms bumping and output may be used interchangeably. 
     The decoded picture buffer (DPB)  116  may decode  2210  and store the current picture in the decoded picture buffer (DPB)  116 . The decoded picture buffer (DPB)  116  may mark  2212  the current decoded picture stored in the decoded picture buffer (DPB)  116 . For example, the decoded picture buffer (DPB)  116  may mark  2212  the current decoded picture as “unused for reference,” “used for reference,” “needed for output” or “not needed for output.” The decoded picture buffer (DPB)  116  may also perform  2214  another picture output (additional bumping) from the decoded picture buffer (DPB)  116 . In some configurations, a repeated removal/bumping of pictures from the decoded picture buffer (DPB)  116  may occur until certain conditions are satisfied. 
       FIG.  65    is a flow diagram of another method  2300  for hybrid decoded picture buffer (DPB)  116  operation. For example, the method  2300  of  FIG.  65    may be a preferred method for hybrid decoded picture buffer (DPB)  116  operation. The method  2300  may be performed by a decoded picture buffer (DPB)  116  as part of a decoder  2104  on an electronic device  102 . In one configuration, the method  2300  may be performed by a hybrid decoded picture buffer (DPB) operation module  2120 . The decoded picture buffer (DPB)  116  may begin parsing  2302  a first slice header of a current picture. The term hybrid refers to the fact that some of the decoded picture buffer (DPB)  116  operation steps are performed on a picture basis and some of the decoded picture buffer (DPB)  116  operation steps are performed on an access unit (AU) basis. The decoded picture buffer (DPB)  116  may perform  2304  a picture based removal (without output) from the decoded picture buffer (DPB)  116 . The decoded picture buffer (DPB)  116  may perform  2306  an access unit (AU) based picture output (bumping) from the decoded picture buffer (DPB)  116 . The decoded picture buffer (DPB)  116  may perform  2308  picture based decoding and storage of the current picture in the decoded picture buffer (DPB). 
     The decoded picture buffer (DPB)  116  may perform  310  picture based marking of the current decoded picture in the decoded picture buffer (DPB). The marking step performed by the decoded picture buffer (DPB)  116  may be further sub-divided to include both a reference marking step and an output marking step. As used herein, marking pictures as “unused for reference” or “used for reference” is referred to as the reference marking step. A decoded picture in the decoded picture buffer (DPB)  116  can be marked as only one of “unused for reference,” “used for short-term reference,” or “used for long-term reference” at any given moment during the decoding process operation. Assigning one of these markings to a picture implicitly removes another of the markings that is assigned to the picture. When a picture is referred to as being marked as “used for reference,” this collectively refers to the picture being marked as either “used for short-term reference” or “used for long-term reference,” but never both. As used herein, marking pictures as “needed for output” or “not needed for output” is referred to as the output marking step. 
     The decoded picture buffer (DPB)  116  may operate in such a manner that the reference marking step and the output marking step could happen on either a picture basis or on an access unit (AU) basis. In general, all possible combinations (typically four combinations) of doing these two marking steps individually on a picture basis or on an access unit (AU) basis are supported. However, it may be preferable that the reference marking step is picture based and the output marking step is access unit (AU) based. 
     The decoded picture buffer (DPB)  116  may also perform  2312  an access unit (AU) based output marking of the current decoded picture. The decoded picture buffer (DPB)  116  may perform  2314  another access unit (AU) based picture output (additional bumping) from the decoded picture buffer (DPB)  116 . In some configurations, a repeated removal/bumping of pictures from the decoded picture buffer (DPB)  116  may occur until certain conditions are satisfied. 
     In some approaches, bitstream conformance constraints may be required for flags in the slice segment header. In some cases, the constraints may be applied for flags across pictures belonging to the same access unit (AU). For example, the flags pic_output_flag and/or no_output_of_prior_pics_flag may be required to follow bitstream conformance constraints. For instance, JCTVC-L1003, JCTVC-M1008 and JCT3V-D1004 each describe signaling in the slice segment header using pic_output_flag and no_output_of_prior_pics_flag. Further, flags such as PicOutputFlag, NoRaslOutputFlag and NoOutputOfPriorPicsFlag are derivable based on the syntax elements and NAL unit types. 
     JCTVC-L1003, JCTVC-M1008, and JCT3V-D1004, also include descriptions of DPB for HEVC, SHVC and MV-HEVC. JCTVC-M1008 SHVC Draft Text 1 provides text draft for a scalable extension of HEVC. JCT3V-D1004 MV-HEVC Draft Text 4 describes text draft for multi-view extension of HEVC. 
     The video coded bitstream, according to JCTVC-L1003, JCTVC-M1008 and/or JCT3V-D1004, may include a syntax structure that is placed into logical data packets generally referred to as Network Abstraction Layer (NAL) units. Each NAL unit includes a NAL unit header, such as a two-byte NAL unit header (e.g., 16 bits), to identify the purpose of the associated data payload. For example, each coded slice (and/or picture) may be coded in one or more slice (and/or picture) NAL units. Other NAL units may be included for other categories of data, such as for example, supplemental enhancement information, a coded slice of temporal sub-layer access (TSA) picture, a coded slice of step-wise temporal sub-layer access (STSA) picture, a coded slice a non-TSA, non-STSA trailing picture, a coded slice of broken link access picture, a coded slice of instantaneous decoded refresh picture, a coded slice of clean random access picture, a coded slice of decodable leading picture, a coded slice of tagged for discard picture, a video parameter set, sequence parameter set, a picture parameter set, access unit delimiter, an end of sequence, an end of bitstream, filler data and/or a sequence enhancement information message. Table (7) below illustrates one example of NAL unit codes and NAL unit type classes. Other NAL unit types may also be included, as desired. 
     It should also be understood that the NAL unit type values for the NAL units shown in the Table (7) may be rearranged and reassigned. Also, additional NAL unit types may be added or removed. 
     An intra random access point (IRAP) picture is a coded picture for which each video coding layer NAL unit has nal_unit_type in the range of BLA_W_LP to RSV_IRAP_VCL23, inclusive, as shown in Table (7) below. An IRAP picture includes only Intra coded (I) slices. 
     An instantaneous decoding refresh (IDR) picture is an IRAP picture for which each video coding layer NAL unit has nal_unit_type equal to IDR_W_RADL or IDR_N_LP, as shown in Table (7). An instantaneous decoding refresh (IDR) picture includes only I slices and may be the first picture in the bitstream in decoding order, or may appear later in the bitstream. 
     Each IDR picture is the first picture of a coded video sequence (CVS) in decoding order. A broken link access (BLA) picture is an IRAP picture for which each video coding layer NAL unit has nal_unit_type equal to BLA_W_LP, BLA_W_RADL, or BLA_N_LP, as shown in Table (7). 
     A BLA picture includes only I slices, and may be the first picture in the bitstream in decoding order, or may appear later in the bitstream. Each BLA picture begins a new coded video sequence, and has the same effect on the decoding process as an IDR picture. However, a BLA picture includes syntax elements that specify a non-empty reference picture set. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 42 
               
               
                   
               
               
                   
                   
                   
                 NAL  
               
               
                 nal_ 
                   
                 Content of NAL unit and raw  
                 unit  
               
               
                 unit_ 
                 Name of  
                 byte sequence payload (RBSP)  
                 type  
               
               
                 type  
                 nal_unit_type  
                 syntax structure  
                 class 
               
               
                   
               
             
            
               
                  0  
                 TRAIL_N  
                 Coded slice segment of a  
                 Video  
               
               
                  1  
                 TRAIL_R  
                 non-TSA, non-STSA trailing  
                 Coding  
               
               
                   
                   
                 picture  
                 Layer  
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                 (VCL)  
               
               
                  2  
                 TSA_N  
                 Coded slice segment of a  
                 VCL  
               
               
                  3  
                 TSA_R  
                 temporal sub-layer access (TSA)  
                   
               
               
                   
                   
                 picture  
                   
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                   
               
               
                  4  
                 STSA_N  
                 Coded slice segment of an  
                 VCL  
               
               
                  5  
                 STSA_R  
                 Step-wise Temporal sub-layer  
                   
               
               
                   
                   
                 access (STSA) picture  
                   
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                   
               
               
                  6  
                 RADL_N  
                 Coded slice segment of a random  
                 VCL  
               
               
                  7  
                 RADL_R  
                 access decodable leading  
                   
               
               
                   
                   
                 (RADL) picture  
                   
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                   
               
               
                  8  
                 RASL_N  
                 Coded slice segment of a random  
                 VCL  
               
               
                  9  
                 RASL_R  
                 access skipped leading (RASL)  
                   
               
               
                   
                   
                 picture  
                   
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                   
               
               
                 10  
                 RSV_VCL_N10  
                 Reserved non-IRAP sub-layer  
                 VCL  
               
               
                 12  
                 RSV_VCL_N12  
                 non-reference VCL NAL unit  
                   
               
               
                 14  
                 RSV_VCL_N14  
                 types  
                   
               
               
                 11  
                 RSV_VCL_R11  
                 Reserved non-IRAP sub-layer  
                 VCL  
               
               
                 13  
                 RSV_VCL_R13  
                 reference VCL NAL unit types  
                   
               
               
                 15  
                 RSV_VCL_R15  
                   
                   
               
               
                 16  
                 BLA_W_LP  
                 Coded slice segment of a broken  
                 VCL  
               
               
                 17  
                 BLA_W_RADL  
                 link access (BLA) picture  
                   
               
               
                 18  
                 BLA_N_LP  
                 slice_segment_layer_rbsp( )  
                   
               
               
                 19  
                 IDR_W_RADL  
                 Coded slice segment of an  
                 VCL  
               
               
                 20  
                 IDR_N_LP  
                 instantaneous decoding refresh  
                   
               
               
                   
                   
                 (IDR) picture  
                   
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                   
               
               
                 21  
                 CRA_NUT  
                 Coded slice segment of a clean  
                 VCL  
               
               
                   
                   
                 random access (CRA) picture  
                   
               
               
                   
                   
                 slice_segment_layer_rbsp( )  
                   
               
               
                 22  
                 RSV_IRAP_VCL22  
                 Reserved IRAP VCL NAL unit  
                 VCL  
               
               
                 23  
                 RSV_IRAP_VCL23  
                 types  
                   
               
               
                 24 . . . 31  
                 RSV_VCL24 . . .  
                 Reserved non-IRAP VCL NAL  
                 VCL  
               
               
                   
                 RSV_VCL31  
                 unit types  
                   
               
               
                 32  
                 VPS_NUT  
                 Video parameter set  
                 non-  
               
               
                   
                   
                 video_parameter_set_rbsp( )  
                 video  
               
               
                   
                   
                   
                 coding  
               
               
                   
                   
                   
                 layer  
               
               
                   
                   
                   
                 (non-  
               
               
                   
                   
                   
                 VCL)  
               
               
                 33  
                 SPS_NUT  
                 Sequence parameter set  
                 non-  
               
               
                   
                   
                 seq_parameter_set_rbsp( )  
                 VCL  
               
               
                 34  
                 PPS_NUT  
                 Picture parameter set  
                 non-  
               
               
                   
                   
                 pic_parameter_set_rbsp( )  
                 VCL  
               
               
                 35  
                 AUD_NUT  
                 Access unit delimiter  
                 non-  
               
               
                   
                   
                 access_unit_delimiter_rbsp( )  
                 VCL  
               
               
                 36  
                 EOS_NUT  
                 End of sequence  
                 non-  
               
               
                   
                   
                 end_of_seq_rbsp( )  
                 VCL  
               
               
                 37  
                 EOB_NUT  
                 End of bitstrearn  
                 non-  
               
               
                   
                   
                 end_of_bitstream_rbsp( )  
                 VCL  
               
               
                 38  
                 FD_NUT  
                 Filler data  
                 non-  
               
               
                   
                   
                 filler_data_rbsp( )  
                 VCL  
               
               
                 39  
                 PREFIX_SEI_NUT  
                 Supplemental enhancement  
                 non-  
               
               
                 40  
                 SUFFIX_SEI_NUT  
                 information  
                 VCL  
               
               
                   
                   
                 sei_rbsp( )  
                   
               
               
                 41 . . . 47  
                 RSV_NVCL41 . . .  
                 Reserved  
                 non-  
               
               
                   
                 RSV_NVCL47  
                   
                 VCL  
               
               
                 48 . . . 63  
                 UNSPEC48 . . .  
                 Unspecified  
                 non-  
               
               
                   
                 UNSPEC63  
                   
                 VCL 
               
               
                   
               
               
                 Table (7) 
               
            
           
         
       
     
     Referring to Table (8) below, the NAL unit header syntax may include two bytes of data, namely, 16 bits. The first bit may be a “forbidden_zero_bit” that is always set to zero at the start of a NAL unit. The next six bits may be a “nal_unit_type” which specifies the type of raw byte sequence payloads (“RBSP”) data structure included in the NAL unit as shown in Table (7) above. The next 6 bits may be a “nuh_layer_id” which specify the identifier of the layer. In some cases, these six bits may be specified as “nuh_reserved_zero_6bits” instead. The nuh_reserved_zero_6bits may be equal to 0 in the base specification of the standard. In a scalable video coding and/or syntax extensions, nuh_layer_id may specify that this particular NAL unit belongs to the layer identified by the value of these 6 bits. 
     The next syntax element may be “nuh_temporal_id_plus1”. The nuh_temporal_id_plus1 minus 1 may specify a temporal identifier for the NAL unit. The variable temporal identifier TemporalId may be specified as TemporalId=nuh_temporal_id_plus1−1. The temporal identifier TemporalId is used to identify a temporal sub-layer. The variable HighestTid identifies the highest temporal sub-layer to be decoded. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 43 
               
               
                   
                   
               
               
                   
                 nal_unit_header( ) { 
                 Descriptor 
               
               
                   
                   
               
             
            
               
                   
                  forbidden_zero_bit  
                 f(1)  
               
               
                   
                  nal_unit_type  
                 u(6)  
               
               
                   
                  nuh_layer_id  
                 u(6)  
               
               
                   
                  nuh_temporal_id_plus1  
                 u(3)  
               
               
                   
                 } 
               
               
                   
                   
               
               
                   
                 Table (8) 
               
            
           
         
       
     
     Table (9) below shows an exemplary sequence parameter set (SPS) syntax structure. pic_width_in_luma_samples specifies the width of each decoded picture in units of luma samples. pic_width_in_luma_samples shall not be equal to 0. pic_height_in_luma_samples specifies the height of each decoded picture in units of luma samples. pic_height_in_luma_samples shall not be equal to 0. 
     sps_max_sub_layers_minus1 plus 1 specifies the maximum number of temporal sub-layers that may be present in each CVS referring to the SPS. The value of sps_max_sub_layers_minus1 ranges from 0 to 6, inclusive. 
     sps_sub_layer_ordering_info_present_flag flag equal to 1 specifies that sps_max_dec_pic_buffering_minus1[i], sps_max_num_reorder_pics[i], and sps_max_latency_increase_plus1[i] syntax elements are present for sps_max_sub_layers_minus1+1 sub-layers. sps_sub_layer_ordering_info_present_flag equal to 0 specifies that the values of sps_max_dec_pic_buffering_minus1[sps_max_sub_layers_minus1], sps_max_num_reorder_pics[sps_max_sub_layers_minus1], and sps_max_latency_increase_plus1[sps_max_sub_layers_minus1] apply to all sub-layers. 
     sps_max_dec_pic_buffering_minus1[i] plus 1 specifies the maximum required size of the decoded picture buffer for the CVS in units of picture storage buffers when HighestTid is equal to i. The value of sps_max_dec_pic_buffering_minus1[i] ranges from 0 to MaxDpbSize−1, inclusive where MaxDpbSize specifies the maximum decoded picture buffer size in units of picture storage buffers. When i is greater than 0, sps_max_dec_pic_buffering_minus1[i] shall be greater than or equal to sps_max_dec_pic_buffering_minus1[i−1]. When sps_max_dec_pic_buffering_minus1[i] is not present for i in the range of 0 to sps_max_sub_layers_minus1−1, inclusive, due to sps_sub_layer_ordering_info_present_flag being equal to 0, it is inferred to be equal to sps_max_dec_pic_buffering_minus1[sps_max_sub_layers_minus1]. 
     sps_max_num_reorder_pics[i] indicates the maximum allowed number of pictures that can precede any picture in the CVS in decoding order and follow that picture in output order when HighestTid is equal to i. The value of sps_max_num_reorder_pics[i] ranges from 0 to sps_max_dec_pic_buffering_minus1[i], inclusive. When i is greater than 0, sps_max_num_reorder_pics[i] may be greater than or equal to sps_max_num_reorder_pics[i−1]. When sps_max_num_reorder_pics[i] is not present for i in the range of 0 to sps_max_sub_layers_minus1−1, inclusive, due to sps_sub_layer_ordering_info_present_flag being equal to 0, it is inferred to be equal to sps_max_num_reorder_pics[sps_max_sub_layers_minus1]. 
     sps_max_latency_increase_plus1[i] not equal to 0 may be used to compute the value of SpsMaxLatencyPictures[i], which specifies the maximum number of pictures that can precede any picture in the CVS in output order and follow that picture in decoding order when HighestTid is equal to i. When sps_max_latency_increase_plus1[i] is not equal to 0, the value of SpsMaxLatencyPictures[i] is specified as SpsMaxLatencyPictures[i]=sps_max_num_reorder_pics[i]+sps_max_latency_increase_plus1[i]−1. When sps_max_latency_increase_plus1[i] is equal to 0, no corresponding limit is expressed. 
     The value of sps_max_latency_increase_plus1[i] ranges from 0 to 2 32 −2, inclusive. When sps_max_latency_increase_plus1[i] is not present for i in the range of 0 to sps_max_sub_layers_minus1−1, inclusive, due to sps_sub_layer_ordering_info_present_flag being equal to 0, it is inferred to be equal to sps_max_latency_increase_plus1[sps_max_sub_layers_minus1]. 
     
       
         
           
               
             
               
                 TABLE 44 
               
               
                   
               
               
                 Table (9) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   
                 seq_parameter_set_rbsp( ) { 
               
               
                   
                  ... 
               
               
                   
                 sps_max_sub_layers_minus1 
               
               
                   
                 ... 
               
               
                   
                 pic_width_in_luma_samples 
               
               
                   
                 pic_height_in_luma_samples 
               
               
                   
                 ... 
               
               
                   
                  for( i = ( sps_sub_layer_ordering_info_present_flag ? 0 : 
               
               
                   
                 sps_max_sub_layers_minus1 ); 
               
               
                   
                      I&lt;=sps_max_sub_layers_minus1; i++) { 
               
               
                   
                    sps_max_dec_pic_buffering_minus1[i] 
               
               
                   
                    sps_max_num_reorder_pics[i] 
               
               
                   
                    sps_max_latency_increase_plus1[i] 
               
               
                   
                  } 
               
               
                   
                 ... 
               
               
                   
                 } 
               
               
                   
               
            
           
         
       
     
     Further, JCTVC-L1003 describes the HEVC standard. For example, detail regarding pic_out_flag and no_output_of_prior_pics_flag is provided in Table (10) below: 
     
       
         
           
               
             
               
                 TABLE 45 
               
               
                   
               
               
                 Table (10) 
               
               
                 GENERAL SLICE SEGMENT HEADER SYNTAX 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 slice_segment_header( ) { 
               
               
                  first_slice_segment_in_pic_flag 
               
               
                  if( nal_unit_type&gt;=BLA_W_LP&amp;&amp;nal_unit_type&lt;= 
               
               
                  RSV_IRAP_VCL23 ) 
               
               
                    no_output_of_prior_pics_flag 
               
               
                  slice_pic_parameter_set_id 
               
               
                  if( !first_slice_segment_in_pic_flag ) { 
               
               
                    if( dependent_slice_segments_enabled flag ) 
               
               
                       dependent_slice_segment_flag 
               
               
                    slice_segment_address 
               
               
                  } 
               
               
                  if( !dependent_slice_segment_flag ) { 
               
               
                    for( i = 0; i &lt; num_extra_slice_header bits; i++ ) 
               
               
                       slice_reserved_flag[i] 
               
               
                    slice_type 
               
               
                    if( output_flag_present_flag ) 
               
               
                       pic_output_flag 
               
               
                  ... 
               
               
                  ... 
               
               
                  } 
               
               
                   
               
            
           
         
       
     
     In Table (10), no_output_of_prior_pics_flag affects the output of previously-decoded pictures in the decoded picture buffer (DPB) after the decoding of an IDR or a BLA picture that is not the first picture in the bitstream as specified in Annex C of JCTVC-L1003. 
     output_flag_present_flag equal to 1 indicates that the pic_output_flag syntax element is present in the associated slice headers. output_flag_present_flag equal to 0 indicates that the pic_output_flag syntax element is not present in the associated slice headers. pic_output_flag affects the decoded picture output and removal processes as specified in Annex C of JCTVC-L1003. When pic_output_flag is not present, it is inferred to be equal to 1. 
     For the general decoding process (as found in 8.1 of JCTVC-L1003), PicOutputFlag is set as follows:
         If the current picture is a RASL picture and NoRaslOutputFlag of the associated IRAP picture is equal to 1, PicOutputFlag may be set equal to 0.   Otherwise, PicOutputFlag may be set equal to pic_output_flag.       

     Additionally, during the general decoding process for generating unavailable reference pictures (as found in section 8.3.3.1 of JCTVC-L1003), the value of PicOutputFlag for the generated picture may be set equal to 0 under certain conditions. 
     When the current picture is an IRAP picture, the following applies:
         If the current picture is an IDR picture, a BLA picture, the first picture in the bitstream in decoding order or the first picture that follows an end of sequence NAL unit in decoding order, the variable NoRaslOutputFlag may be set equal to 1.   Otherwise, if some external means not specified in JCTVC-L1003 is available to set the variable HandleCraAsBlaFlag to a value for the current picture, the variable HandleCraAsBlaFlag may be set equal to the value provided by the external means and the variable NoRaslOutputFlag may be set equal to HandleCraAsBlaFlag.   Otherwise, the variable HandleCraAsBlaFlag may be set equal to 0 and the variable NoRaslOutputFlag may be set equal to 0.       

     As describe above, access unit (AU) refers to a set of network abstraction layer (NAL) units that are associated with each other according to a specified classification rule, that are consecutive in decoding order, and that include the video coding layer (VCL) NAL units of all coded pictures associated with the same output time and their associated non-VCL NAL units. The base layer is a layer in which all VCL NAL units have a nuh_layer_id equal to 0. A coded picture is a coded representation of a picture that includes VCL NAL units with a particular value of nuh_layer_id and that includes all the coding tree units of the picture. In some cases, a coded picture may be called a layer component. Addition details about steps being picture based or access unit (AU) based are given in relation to  FIGS.  69  and  70    below. 
     In some configurations, bitstream conformance constraints for pic_output_flag and/or no_output_of_prior_pics_flag may be used for coded pictures in an access unit (AU). In addition, three new access unit output flags, AU output flag (e.g., AuOutputFlag), AU no RASL output flag (e.g., AuNoRaslOutputFlag) and AU no output of prior pictures flag (e.g., AuNoOutputOfPriorPicsFlag), may be derived for an AU based on the value of various syntax elements and NAL unit types for the coded pictures in the AU. In some configurations, output and removal of pictures may be based on these three flags (e.g., AuOutputFlag, AuNoRaslOutputFlag and AuNoOutputOfPriorPicsFlag) for SHVC and multi-view HEVC. 
     For example, bitstream conformance constraints for HEVC-extensions may be followed as described in the systems and methods herein. In particular, bitstream conformance constraints may be applied to the SHVC bitstream. In addition, bitstream conformance constraints may be applied for the MV-HEVC bitstream. 
     In one configuration, when present, the value of the slice segment header syntax elements pic_output_flag may be required to be the same in all slice segment headers of coded pictures in an access unit (AU). In another configuration, the value of the slice segment header syntax elements pic_output_flag, when present, may be the same in all slice segment headers of coded pictures in an access unit (AU) when the coded pictures have the same NAL unit type. 
     In one configuration, when present, the value of the slice segment header syntax elements pic_output_flag for the slice segments with nuh_layer_id equal to the nuh_layer_id value of a target layer may be the same in all slice segment headers of such coded pictures in an access unit (AU). In another configuration, when present, the value of the slice segment header syntax elements pic_output_flag for the slice segments with nuh_layer_id not equal to the nuh_layer_id value of a target layer may be 0 in all slice segment headers of such coded pictures in an access unit (AU). 
     In one configuration, a target layer may be a layer which belongs to a layer set or a target layer set or an output layer set as defined in JCTVC-L1003, JCTVC-M1008, or JCT3V-D1004. In another configuration, a target layer may be a layer which is intended to be decoded. In yet another configuration, a target layer may be a layer which is intended to be decoded and outputted (displayed or otherwise sent for output). 
     In some configurations, when present, the value of the slice segment header syntax elements no_output_of_prior_pics_flag may be the same in all slice segment headers of coded pictures in an access unit (AU). In other configurations, when present, the value of the slice segment header syntax elements no_output_of_prior_pics_flag may be the same in all slice segment headers of coded pictures in an access unit (AU) when the coded pictures have the same NAL unit type. In one configuration, when present, the value of the slice segment header syntax elements no_output_of_prior_pics_flag for the slice segments with nuh_layer_id equal to the nuh_layer_id value of a target layer may be the same in all slice segment headers of such coded pictures in an access unit (AU). 
     In some configuration, the syntax elements pic_output_flag and/or no_output_of_prior_pics_flag may not be signaled when nuh_layer_id&gt;0. In this case, the values for layers with nuh_layer_id&gt;0 may be inferred to be equal to their signaled values for nuh_layer_id equal to 0. 
     In some configurations, additional flags, such as AuOutputFlag and AuNoRaslOutputFlag may be employed. The flags AuOutputFlag and AuNoRaslOutputFlag may be derived according to a number of approaches. In one approach or configuration, the two flags, AuOutputFlag and AuNoRaslOutputFlag may be derived and used for DPB operation. AuOutputFlag may be set equal to 1 if PicOutputFlag is equal to 1 for all the pictures in the AU. Otherwise AuOutputFlag may be set equal to 0. 
     In another approach, AuOutputFlag may be set equal to 1 if PicOutputFlag is equal to 1 for at least one picture in the AU. Otherwise AuOutputFlag may be set equal to 0. Thus, in this case, the AuOutputFlag may be set equal to 0 if PicOutputFlag is equal to 0 for all the pictures in an AU. 
     In yet another approach, AuOutputFlag may be set equal to 1 if PicOutputFlag is equal to 1 for pictures belonging to all target output layers in the AU. Otherwise AuOutputFlag may be set equal to 0. 
     In still yet another approach, AuOutputFlag may be set equal to 1 if PicOutputFlag is equal to 1 for picture belonging to at least one target output layers in the AU. Otherwise AuOutputFlag may be set equal to 0. 
     In one approach, AuNoRaslOutputFlag may be set equal to 1 if NoRaslOutputFlag is equal to 1 for all the pictures in the AU. Otherwise AuNoRaslOutputFlag may be set equal to 0. 
     In another approach, AuNoRaslOutputFlag may be set equal to 1 if NoRaslOutputFlag is equal to 1 for at least one picture in the AU. Otherwise AuNoRaslOutputFlag may be set equal to 0. Thus, in this case, the AuNoRaslOutputFlag may be set equal to 0 if NoRaslOutputFlag is equal to 0 for all the pictures in an AU. 
     In yet another approach, AuNoRaslOutputFlag may be set equal to 1 if NoRaslOutputFlag is equal to 1 for pictures belonging to all target output layers in the AU. Otherwise AuNoRaslOutputFlag may be set equal to 0. 
     In still yet another approach, AuNoRaslOutputFlag may be set equal to 1 if NoRaslOutputFlag is equal to 1 for picture belonging to at least one target output layers in the AU. Otherwise AuNoRaslOutputFlag may be set equal to 0. 
     In some of the above approaches and configurations, the DPB operation may use the AuOutputFlag in place of the PicOutputFlag. Additionally, the DPB operation may use AuNoRaslOutputFlag in place of the NoRaslOutputFlag. 
     Examples showing the use of AU output flags, such as AuOutputFlag and AuNoRaslOutputFlag, according to the present systems and methods, are provided below in Listing (1A) and Listing (2A) below. Also, as described below in Listing (1), Listing (1A), Listing (2) and Listing (2A), the AU output flag AuNoOutputOfPriorPicsFlag may be derived and used for DPB operation. 
     The present systems and methods may be implemented by changes to standards documents. Listing (1) below provides the sections of JCTVC-L1003 that would be changed to accommodate the present systems and methods. 
     Listing 1 
     C.3 Operation of the Decoded Picture Buffer (DPB) 
     C.3.1 General 
     The specifications in this subclause apply independently to each set of DPB parameters selected as specified in subclause C.1. The DPB operates separately or independently for each layer. Thus the following steps take place separately for each decoded picture with a particular value of nuh_layer_id.
 
The decoded picture buffer contains picture storage buffers. Each layer consists of its own set of picture storage buffers. Thus picture storage buffers of each layer are associated with the nuh_layer_id value of the layer. Each of the picture storage buffers may contain a decoded picture that is marked as “used for reference” or is held for future output. The processes specified in subclauses C.3.2, C.3.3 and C.3.4 are sequentially applied as specified below.
 
C.3.2 Removal of Pictures from the DPB
 
The removal of pictures from the DPB before decoding of the current picture (but after parsing the slice header of the first slice of the current picture) happens instantaneously at the CPB removal time of the first decoding unit of the current picture belonging to access unit n (containing the current picture) and proceeds as follows:
         The decoding process for RPS as specified in subclause 8.3.2 is invoked.   When the current picture is an IRAP picture with NoRaslOutputFlag equal to 1 that is not picture 0, the following ordered steps are applied:
           1. The variable NoOutputOfPriorPicsFlag is derived for the decoder under test as follows:
               If the current picture is a CRA picture, NoOutputOfPriorPicsFlag is set equal to 1 (regardless of the value of no_output_of_prior_pics_flag).   Otherwise, if the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps_max_dec_pic_buffering_minus1[HighestTid] derived from the active SPS corresponding to the nuh_layer_id value of the current picture is different from the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps_max_dec_pic_buffering_minus1[HighestTid], respectively, derived from the SPS active for the preceding picture with the nuh_layer_id value equal to the nuh_layer_id value of the current picture, NoOutputOfPriorPicsFlag may (but should not) be set to 1 by the decoder under test, regardless of the value of no_output_of_prior_pics_flag.
                   NOTE—Although setting NoOutputOfPriorPicsFlag equal to no_output_of_prior_pics_flag is preferred under these conditions, the decoder under test is allowed to set NoOutputOfPriorPicsFlag to 1 in this case.   
                   Otherwise, NoOutputOfPriorPicsFlag is set equal to no_output_of_prior_pics_flag.   
               2. The value of NoOutputOfPriorPicsFlag derived for the decoder under test is applied for the HRD, such that when the value of NoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers corresponding to the nuh_layer_id value of the current picture in the DPB are emptied without output of the pictures they contain, and the DPB fullness for the nuh_layer_id value of the current picture is set equal to 0.
               In one embodiment the value of NoOutputOfPriorPicsFlag derived for the decoder under test is applied for the HRD, such that when the value of NoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers corresponding to all the nuh_layer_id values in the DPB are emptied without output of the pictures they contain, and the DPB fullness for all nuh_layer_id values is set equal to 0.   In one embodiment the value of NoOutputOfPriorPicsFlag derived for the decoder under test is applied for the HRD, such that when the value of NoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers PSB[currLayerId] with currLayerId equal to nuh_layer_id value of the current picture in the DPB are emptied without output of the pictures they contain, and the DPB fullness DPBFullness[currLayerId] for the nuh_layer_id value currLayerId of the current picture is set equal to 0.   In one embodiment the value of NoOutputOfPriorPicsFlag derived for the decoder under test is applied for the HRD, such that when the value of NoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers PSB[nuh_layer_id] for all the nuh_layer_id values in the DPB are emptied without output of the pictures they contain, and the DPB fullness DPBFullness[nuh_layer_id] for all nuh_layer_id values is set equal to 0.   
               
           When both of the following conditions are true for any pictures k in the picture storage buffer corresponding to the nuh_layer_id value of the current picture in the DPB, all such pictures k in the DPB are removed from the DPB:
           picture k is marked as “unused for reference”   picture k has PicOutputFlag equal to 0 or its DPB output time is less than or equal to the CPB removal time of the first decoding unit (denoted as decoding unit m) of the current picture n; i.e. DpbOutputTime[k] is less than or equal to CpbRemovalTime(m)   For each picture that is removed from the DPB, the DPB fullness is decremented by one.   In one embodiment for each picture k having nuh_layer_id value nuhLayerIdk that is removed from the DPB, the DPB fullness DPBfullness[nuhLayerIdk] is decremented by one.
 
C.3.3 Picture Output
 
The processes specified in this subclause happen instantaneously at the CPB removal time of access unit n, AuCpbRemovalTime[n].
 
When picture n has PicOutputFlag equal to 1, its DPB output time DpbOutputTime[n] is derived as follows, where the variable firstPicInBufferingPeriodFlag is equal to 1 if access unit n is the first access unit of a buffering period and 0 otherwise:
   
               

                                if( !SubPicHrdFlag ) {        DpbOutputTime[ n ] = AuCpbRemovalTime[ n ] + ClockTick * picDpbOutputDelay (C-16)        if( firstPicInBufferingPeriodFlag )         DpbOutputTime[ n ] −= ClockTick * DpbDelayOffset       } else        DpbOutputTime[ n ] = AuCpbRemovalTime[ n ] + ClockSubTick *       picSptDpbOutputDuDelay                    
where picDpbOutputDelay is the value of pic dpb_output_delay in the picture timing SEI message associated with access unit n, and picSptDpbOutputDuDelay is the value of pic_spt_dpb_output_du_delay, when present, in the decoding unit information SEI messages associated with access unit n, or the value of pic_dpb_output_du_delay in the picture timing SEI message associated with access unit n when there is no decoding unit information SEI message associated with access unit n or no decoding unit information SEI message associated with access unit n has pic_spt_dpb_output_du_delay present.
         NOTE—When the syntax element pic_spt_dpb_output_du_delay is not present in any decoding unit information SEI message associated with access unit n, the value is inferred to be equal to pic_dpb_output_du_delay in the picture timing SEI message associated with access unit n.
 
The output of the current picture if its nuh_layer_id belongs to the layer in the TargetDecLayerIdList is specified as follows:
   If PicOutputFlag is equal to 1 and DpbOutputTime[n] is equal to AuCpbRemovalTime[n], the current picture is output.   Otherwise, if PicOutputFlag is equal to 0, the current picture is not output, but will be stored in the picture storage buffer corresponding to the nuh_layer_id value of the current picture in the DPB as specified in subclause C.3.4.   In one embodiment: Otherwise, if PicOutputFlag is equal to 0, the current picture is not output, but will be stored in the picture storage buffer PSB[currLayerId] corresponding to the nuh_layer_id value currLayerId of the current picture in the DPB as specified in subclause C.3.4.   Otherwise (PicOutputFlag is equal to 1 and DpbOutputTime[n] is greater than AuCpbRemovalTime[n]), the current picture is output later and will be stored in the picture storage buffer corresponding to the nuh_layer_id value of the current picture in the DPB (as specified in subclause C.3.4) and is output at time DpbOutputTime[n] unless indicated not to be output by the decoding or inference of no_output_of_prior_pics_flag equal to 1 at a time that precedes DpbOutputTime[n].
 
In another embodiment the above steps are specified for:
 
The output of the current picture if its nuh_layer_id belongs to a layer which belongs to the output layer set corresponding to the (current) operation point.
 
In yet another embodiment the above steps are specified for:
 
The output of current picture (without checking if it belongs to the TargetDecLayerIdList or the output layer set for the current operation point).
 
When output, the picture is cropped, using the conformance cropping window specified in the active SPS for the picture.
 
When picture n is a picture that is output and is not the last picture of the bitstream that is output, the value of the variable DpbOutputlnterval[n] is derived as follows:
 
DpbOutputlnterval[ n ]=DpbOutputTime[nextPicInOutputOrder]−DpbOutputTime[ n ]  (C-17)
 
where nextPicInOutputOrder is the picture that follows picture n in output order and has PicOutputFlag equal to 1.
 
C.3.4 Current Decoded Picture Marking and Storage
 
The process specified in this subclause happens instantaneously at the CPB removal time of access unit n, CpbRemovalTime[n].
 
The current decoded picture is stored in the DPB in an empty picture storage buffer corresponding to the nuh_layer_id value of the current picture, the DPB fullness for the nuh_layer_id value of the current picture is incremented by one, and the current picture is marked as “used for short-term reference.”
 
In one embodiment:
 
The current decoded picture with nuh_layer_id equal to currLayerId is stored in the DPB in an empty picture storage buffer PSB[currLayerId] with currLayerId equal to nuh_layer_id value of the current picture in the DPB, the DPB fullness for the nuh_layer_id value of the current picture DPBFullness[currLayerId] is incremented by one, and the current picture is marked as “used for short-term reference.”
 
C.4 Bitstream Conformance
 
The specifications in subclause C.4 apply.
 
C.5 Decoder Conformance
 
F.8.1.1 C.5.1 General
 
The specifications in subclause C.5.1 apply.
       

     Listing (1) 
     As used in Listing (1) above, PSB refers to a picture storage buffer. DPBFullness refers to a variable used to describe the fullness of decoded picture buffer (DPB)  116 . 
     Listing (1A) below provides an alternative approach to section C.3.2 of Listing (1) according to accommodate the present systems and methods. In some configurations, Listing (1A) may only represent changes to section C.3.2 in JCTVC-L1003. Listing (1A) may use the flags AuNoOutputOfPriorPicsFlag and AuNoRaslOutputFlag defined above. 
     Listing 1A 
     C.3.2 Removal of Pictures from DPB 
     The removal of pictures from the DPB before decoding of the current picture (but after parsing the slice header of the first slice of the current picture) happens instantaneously at the CPB removal time of the first decoding unit of the current picture belonging to access unit n (containing the current picture) and proceeds as follows:
         The decoding process for RPS as specified in subclause 8.3.2 is invoked.   When the current picture is an IRAP picture with AuNoRaslOutputFlag equal to 1 that is not picture 0, the following ordered steps are applied:   In another configuration, when the current picture is an IRAP picture with NoRaslOutputFlag equal to 1 that is not picture 0, the following ordered steps are applied:
           1. The variable AuNoOutputOfPriorPicsFlag is derived for the decoder under test as follows:
               If the current picture is a CRA picture, AuNoOutputOfPriorPicsFlag is set equal to 1 (regardless of the value of no_output_of_prior_pics_flag for the current picture or other pictures in the AU).   Otherwise, if the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps_max_dec_pic_buffering_minus1[HighestTid] derived from the active SPS is different from the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps_max_dec_pic_buffering_minus1[HighestTid], respectively, derived from the SPS active for the preceding picture, AuNoOutputOfPriorPicsFlag may (but should not) be set to 1 by the decoder under test, regardless of the value of no_output_of_prior_pics_flag.
                   NOTE—Although setting AuNoOutputOfPriorPicsFlag equal to no_output_of_prior_pics_flag is preferred under these conditions, the decoder under test is allowed to set AuNoOutputOfPriorPicsFlag to 1 in this case.   
                   Otherwise, AuNoOutputOfPriorPicsFlag is set based on the value of no_output_of_prior_pics_flag for the current picture and other pictures in the AU as follows:
                   AuNoOutputOfPriorPicsFlag is set equal to 1 if no_output_of_prior_pics_flag is equal to 1 for at least one picture in the AU. Otherwise AuNoOutputOfPriorPicsFlag is set equal to 0. Thus in this case the AuNoOutputOfPriorPicsFlag is set equal to 0 if no_output_of_prior_pics_flag is equal to 0 for all the pictures in an AU.   In another embodiment AuNoOutputOfPriorPicsFlag is set equal to 1 if no_output_of_prior_pics_flag is equal to 1 for the current picture. Otherwise AuNoOutputOfPriorPicsFlag is left unchanged.   In another embodiment AuNoOutputOfPriorPicsFlag is set equal to 1 if no_output_of_prior_pics_flag is equal to 1 for all the pictures in the AU. Otherwise AuNoOutputOfPriorPicsFlag is set equal to 0.   In another embodiment AuNoOutputOfPriorPicsFlag is set equal to 1 if no_output_of_prior_pics_flag is equal to 1 for all the pictures belonging to the target output layers in the AU. Otherwise AuNoOutputOfPriorPicsFlag is set equal to 0.   In another embodiment AuNoOutputOfPriorPicsFlag is set equal to 1 if no_output_of_prior_pics flag is equal to 1 for at least one picture belonging to the target output layers in the AU. Otherwise AuNoOutputOfPriorPicsFlag is set equal to 0.   
                   
               2. The value of AuNoOutputOfPriorPicsFlag derived for the decoder under test is applied for the HRD, such that when the value of AuNoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers corresponding to all the nuh_layer_id values in the DPB are emptied without output of the pictures they contain, and the DPB fullness for all the nuh_layer_id values is set equal to 0.
               In another embodiment, the value of AuNoOutputOfPriorPicsFlag derived for the decoder under test is applied for the HRD, such that when the value of AuNoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers corresponding to the nuh_layer_id value of the current picture in the DPB are emptied without output of the pictures they contain, and the DPB fullness for the nuh_layer_id value of the current picture is set equal to 0.   
               
               

     Listing (1A) 
     Listing (2) below provides the sections of JCTVC-L1008 that would be changed to accommodate the present systems and methods. 
     Listing 2 
     F.13 Hypothetical Reference Decoder 
     F.13.1 General 
     The specifications in subclause C.1 apply. 
     F.13.2 Operation of Coded Picture Buffer (CPB) 
     The specifications in subclause C.2 apply. 
     F.13.3 Operation of the Decoded Picture Buffer (DPB) 
     The specifications in subclause C.3 apply separately for each set of decoded pictures with a particular value of nuh_layer_id. 
     PicOutputFlag for pictures that are not included in a target output layer is set equal to 0. 
     Decoded pictures with the same DPB output time and with PicOutputFlag equal to 1 are output in ascending order of nuh_layer_id values of these decoded pictures. 
     F.13.5 Decoder Conformance 
     F.13.5.1 General 
     The specifications in subclause C.5.1 apply. 
     F.13.5.2 Operation of the Output Order DPB 
     F.13.5.2.1 General 
     The decoded picture buffer contains picture storage buffers. Each layer consists of its own set of picture storage buffers. Thus picture storage buffers of each layer are associated with the nuh_layer_id value of the layer. The number of picture storage buffers for nuh_layer_id equal to 0 is derived from the active SPS of the layer with nuh_layer_id equal to 0. The number of picture storage buffers for each non-zero nuh_layer_id value is derived from the active layer SPS for that non-zero nuh_layer_id value. Each of the picture storage buffers contains a decoded picture that is marked as “used for reference” or is held for future output. The process for output and removal of pictures from the DPB as specified in subclause F.13.5.2.2 is invoked, followed by the invocation of the process for picture decoding, marking, additional bumping, and storage as specified in subclause F.13.5.2.3. The “bumping” process is specified in subclause F.13.5.2.4 and is invoked as specified in subclauses F.13.5.2.2 and F.13.5.2.3.
 
F.13.5.2.2 Output and Removal of Pictures from the DPB
 
The output and removal of pictures from the DPB before the decoding of the current picture (but after parsing the slice header of the first slice of the current picture) happens instantaneously when the first decoding unit of the current picture belonging to the access unit containing the current picture is removed from the CPB and proceeds as follows.
 
The decoding process for RPS as specified in subclause 8.3.2 is invoked.
         If the current picture is an IRAP picture with NoRaslOutputFlag equal to 1 and with nuh_layer_id equal to 0 that is not picture 0, the following ordered steps are applied:
           1. The variable NoOutputOfPriorPicsFlag is derived for the decoder under test as follows:
               If the current picture is a CRA picture, NoOutputOfPriorPicsFlag is set equal to 1 (regardless of the value of no_output_of_prior_pics_flag).   Otherwise, if the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps_max_dec_pic_buffering_minus1[HighestTid] derived from the active SPS corresponding to the nuh_layer_id value of the current picture is different from the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps max_dec_pic_buffering minus1[HighestTid], respectively, derived from the SPS active for the preceding picture with the nuh_layer_id value equal to the nuh_layer_id value of the current picture, NoOutputOfPriorPicsFlag may (but should not) be set to 1 by the decoder under test, regardless of the value of no_output_of_prior_pics_flag.
                   NOTE—Although setting NoOutputOfPriorPicsFlag equal to no_output_of_prior_pics_flag is preferred under these conditions, the decoder under test is allowed to set NoOutputOfPriorPicsFlag to 1 in this case.   
                   Otherwise, NoOutputOfPriorPicsFlag is set equal to no_output_of_prior_pics_flag.   
               2. The value of NoOutputOfPriorPicsFlag derived for the decoder under test is applied for the HRD as follows:
               If NoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers corresponding to the nuh_layer_id value of the current picture in the DPB are emptied without output of the pictures they contain, and the DPB fullness for the nuh_layer_id value of the current picture is set equal to 0.   In one embodiment if NoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers corresponding to all the nuh_layer_id values in the DPB are emptied without output of the pictures they contain, and the DPB fullness for all nuh_layer_id values is set equal to 0.   In one embodiment if NoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers PSB[currLayerId] corresponding to the nuh_layer_id value currLayerId of the current picture in the DPB are emptied without output of the pictures they contain, and the DPB fullness DPBFullness[currLayerId] is set equal to 0.   In one embodiment if NoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers PSB[nuh_layer_id] for all the nuh_layer_id values in the DPB are emptied without output of the pictures they contain, and the DPB fullness DPBFullness[nuh_layer_id] for all nuh_layer_id values is set equal to 0.   Otherwise (NoOutputOfPriorPicsFlag is equal to 0), all picture storage buffers containing a picture that is marked as “not needed for output” and “unused for reference” are emptied (without output), and all non-empty picture storage buffers in the DPB corresponding to the nuh_layer_id value of the current picture are emptied by repeatedly invoking the “bumping” process specified in subclause F.13.5.2.4, and the DPB fullness for the nuh_layer_id value of the current picture is set equal to 0.   In another embodiment when NoOutputOfPriorPicsFlag is equal to 0, all picture storage buffers corresponding to all the nuh_layer_id values containing a picture that is marked as “not needed for output” and “unused for reference” are emptied (without output), and all non-empty picture storage buffers corresponding to all the nuh_layer_id values in the DPB are emptied by repeatedly invoking the “bumping” process specified in subclause F.13.5.2.4, and the DPB fullness for all nuh_layer_id values is set equal to 0.   In another embodiment Otherwise (NoOutputOfPriorPicsFlag is equal to 0), all picture storage buffers containing a picture that is marked as “not needed for output” and “unused for reference” are emptied (without output), and all non-empty picture storage buffers PSB[currLayerId] in the DPB corresponding to the nuh_layer_id value currLayerId of the current picture are emptied by repeatedly invoking the “bumping” process specified in subclause F.13.5.2.4, and the DPB fullness DPBFullness[currLayerId] for the nuh_layer_id value of the current picture is set equal to 0.   In another embodiment when NoOutputOfPriorPicsFlag is equal to 0, all picture storage buffers PSB[nuh_layer_id] for all the nuh_layer_id values in the DPB containing a picture that is marked as “not needed for output” and “unused for reference” are emptied (without output), and all non-empty picture storage buffers PSB[nuh_layer_id] corresponding to all the nuh_layer_id values in the DPB are emptied by repeatedly invoking the “bumping” process specified in subclause F.13.5.2.4, and the DPB fullness DPBFullness[nuh_layer_id] for all nuh_layer_id values is set equal to 0.   
               
           Otherwise (the current picture is not an IRAP picture with NoRaslOutputFlag equal to 1 and with nuh_layer_id equal to 0), all picture storage buffers corresponding to the nuh_layer_id value of the current picture containing a picture which are marked as “not needed for output” and “unused for reference” are emptied (without output). For each picture storage buffer that is emptied, the DPB fullness corresponding to the nuh_layer_id value of the current decoded picture is decremented by one. The variable currLayerId is set equal to nuh_layer_id of the current decoded picture and when one or more of the following conditions are true, the “bumping” process specified in subclause F.13.5.2.4 is invoked repeatedly while further decrementing the DPB fullness by one for each additional picture storage buffer corresponding to the nuh_layer_id value of the current decoded picture that is emptied, until none of the following conditions are true:
           The number of pictures with nuh_layer_id equal to currLayerId in the DPB that are marked as “needed for output” is greater than sps_max_num_reorder_pics[HighestTid] from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId.   sps_max_latency_increase_plus1[HighestTid] of the active SPS (when currLayerId is equal to 0) or the active layer SPS for the value of currLayerId is not equal to 0 and there is at least one picture with nuh_layer_id equal to currLayerId in the DPB that is marked as “needed for output” for which the associated variable PicLatencyCount[currLayerId] is greater than or equal to SpsMaxLatencyPictures[HighestTid] derived from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId.   The number of pictures with nuh_layer_id equal to currLayerId in the DPB is greater than or equal to sps_max_dec_pic_buffering_minus1[HighestTid]+1 from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId.
 
In another embodiment: Otherwise (the current picture is not an IRAP picture with NoRaslOutputFlag equal to 1 and with nuh_layer_id equal to 0), all picture storage buffers corresponding to all the nuh_layer_id values containing a picture which are marked as “not needed for output” and “unused for reference” are emptied (without output). For each picture storage buffer that is emptied, the DPB fullness corresponding to the nuh_layer_id value of the picture is decremented by one.
 
In another embodiment: Otherwise (the current picture is not an IRAP picture with NoRaslOutputFlag equal to 1 and with nuh_layer_id equal to 0), all picture storage buffers PSB[currLayerId] in the DPB corresponding to the nuh_layer_id value currLayerId of the current picture containing a picture which are marked as “not needed for output” and “unused for reference” are emptied (without output). For each picture storage buffer that is emptied, the DPB fullness DPBfullness[currLayerId] corresponding to the nuh_layer_id value of the current decoded picture is decremented by one.
 
In another embodiment: Otherwise (the current picture is not an IRAP picture with NoRaslOutputFlag equal to 1 and with nuh_layer_id equal to 0), all picture storage buffers PSB[nuh_layer_id] for all the nuh_layer_id values in the DPB containing a picture which are marked as “not needed for output” and “unused for reference” are emptied (without output). For each picture storage buffer that is emptied, the DPB fullness DPBFullness[nuh_layer_id] corresponding to the nuh_layer_id value of the picture emptied is decremented by one.
 
F.13.5.2.3 Picture Decoding, Marking, Additional Bumping, and Storage
 
The processes specified in this subclause happen instantaneously when the last decoding unit of access unit n containing the current picture is removed from the CPB.
 
The variable currLayerId is set equal to nuh_layer_id of the current decoded picture. For each picture in the DPB that is marked as “needed for output” and that has a nuh_layer_id value equal to currLayerId, the associated variable PicLatencyCount[currLayerId] is set equal to PicLatencyCount[currLayerId]+1.
 
The current picture is considered as decoded after the last decoding unit of the picture is decoded. The current decoded picture is stored in an empty picture storage buffer corresponding to currLayerId (the nuh_layer_id value of the current picture) in the DPB, and the following applies:
   
           If the current decoded picture has PicOutputFlag equal to 1, it is marked as “needed for output” and its associated variable PicLatencyCount[currLayerId] is set equal to 0.   Otherwise (the current decoded picture has PicOutputFlag equal to 0), it is marked as “not needed for output.”
 
In one embodiment, the current decoded picture is stored in an empty picture storage buffer corresponding to currLayerId (the nuh_layer_id value of the current picture) in the DPB, and the following applies:
   If the current decoded picture has PicOutputFlag equal to 1, it is marked as “needed for output” and its associated variable PicLatencyCount[currLayerId] is set equal to 0. All picture storage buffers containing a picture that has the same picture order count value (PicOrderCntVal) as the current decoded picture are marked as “needed for output.”   Otherwise (the current decoded picture has PicOutputFlag equal to 0), it is marked as “not needed for output.”
 
In one embodiment, the current decoded picture is stored in an empty picture storage buffer PSB[curreLayerId] corresponding to currLayerId (the nuh_layer_id value of the current picture) in the DPB, and the DPB fullness for the nuh_layer_id value of the current picture DPBFullness[currLayerId] is incremented by one, and the following applies
 
The current decoded picture is marked as “used for short-term reference.”
 
When one or more of the following conditions are true, the “bumping” process specified in subclause F.13.5.2.4 is invoked repeatedly until none of the following conditions are true.
   The number of pictures with nuh_layer_id equal to currLayerId in the DPB that are marked as “needed for output” is greater than sps_max_num_reorder_Pics[HighestTid] from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId.   sps_max_latency_increase_plus1[HighestTid] is not equal to 0 and there is at least one picture with nuh_layer_id equal to currLayerId in the DPB that is marked as “needed for output” for which the associated variable PicLatencyCount[currLayerId] that is greater than or equal to SpsMaxLatencyPictures[HighestTid] derived from the active SPS (when currLayerId is equal to 0) or from the active layer SPS for the value of currLayerId.
 
F.13.5.2.4 “Bumping” Process
 
The “bumping” process consists of the following ordered steps:
   1. The pictures that are first for output are selected as the ones having the smallest value of PicOrderCntVal of all pictures in the DPB marked as “needed for output.”   2. These pictures are cropped, using the conformance cropping window specified in the active SPS for the picture with nuh_layer_id equal to 0 or in the active layer SPS for a nuh_layer_id value equal to that of the picture, the cropped pictures are output in ascending order of nuh_layer_id, and the pictures are marked as “not needed for output.”   3. Each picture storage buffer that contains a picture marked as “unused for reference” and that included one of the pictures that was cropped and output is emptied.       

     Listing (2) 
     Listing (2A) below provides an alternative approach to section F.13.5.2.2 of Listing (2) according to accommodate the present systems and methods. In some configurations, Listing (2A) may only represent changes to section F.13.5.2.2 in JCTVC-L1008. Listing (2A) may use the flags AuNoOutputOfPriorPicsFlag and AuNoRaslOutputFlag defined above. 
     Listing 2A 
     F.13.5.2.2 Output and Removal of Pictures from the DPB 
     The output and removal of pictures from the DPB before the decoding of the current picture (but after parsing the slice header of the first slice of the current picture) happens instantaneously when the first decoding unit of the access unit containing the current picture is removed from the CPB and proceeds as follows:
 
The decoding process for RPS as specified in subclause 8.3.2 is invoked.
         If the current picture is an IRAP picture with AuNoRaslOutputFlag equal to 1 and with nuh_layer_id equal to 0 that is not picture 0, the following ordered steps are applied:   In another configuration, if the current picture is an IRAP picture with NoRaslOutputFlag equal to 1 and with nuh_layer_id equal to 0 that is not picture 0, the following ordered steps are applied:
           1. The variable AuNoOutputOfPriorPicsFlag is derived for the decoder under test as follows.
               If current picture has nuh_layer_id equal to 0 AuNoOutputOfPriorPicsFlag is initialized to 0. Then:
                   If the current picture is a CRA picture, AuNoOutputOfPriorPicsFlag is set equal to 1 (regardless of the value of no_output_of_prior_pics_flag for the current picture or other pictures in the AU).   Otherwise, if the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps_max_dec_pic_buffering_minus1[HighestTid] derived from the active SPS is different from the value of pic_width_in_luma_samples, pic_height_in_luma_samples, or sps_max_dec_pic_buffering_minus1[HighestTid], respectively, derived from the SPS active for the preceding picture, AuNoOutputOfPriorPicsFlag may (but should not) be set to 1 by the decoder under test, regardless of the value of no_output_of_prior_pics_flag.    NOTE—Although setting AuNoOutputOfPriorPicsFlag equal to no_output_of_prior_pics_flag is preferred under these conditions, the decoder under test is allowed to set AuNoOutputOfPriorPicsFlag to 1 in this case.   Otherwise, AuNoOutputOfPriorPicsFlag is set based on the value of no_output_of_prior_pics_flag for the current picture and other pictures in the AU as follows:    AuNoOutputOfPriorPicsFlag is set equal to 1 if no_output_of_prior_pics_flag is equal to 1 for at least one picture in the AU. Otherwise AuNoOutputOfPriorPicsFlag is set equal to 0. Thus in this case the AuNoOutputOfPriorPicsFlag is set equal to 0 if no_output_of_prior_pics_flag is equal to 0 for all the pictures in an AU.    In another embodiment AuNoOutputOfPriorPicsFlag is set equal to 1 if no_output_of_prior_pics_flag is equal to 1 for current picture. Otherwise AuNoOutputOfPriorPicsFlag is left unchanged.    In another embodiment AuNoOutputOfPriorPicsFlag is set equal to 1 if no_output_of_prior_pics_flag is equal to 1 for all the pictures in the AU. Otherwise AuNoOutputOfPriorPicsFlag is set equal to 0.    In another embodiment AuNoOutputOfPriorPicsFlag is set equal to 1 if no_output_of_prior_pics_flag is equal to 1 for all the pictures belonging to the target output layers in the AU. Otherwise AuNoOutputOfPriorPicsFlag is set equal to 0.    In another embodiment AuNoOutputOfPriorPicsFlag is set equal to 1 if no_output_of_prior_pics_flag is equal to 1 for at least one picture belonging to the target output layer in the AU. Otherwise AuNoOutputOfPriorPicsFlag is set equal to 0.   
                   
               2. The value of AuNoOutputOfPriorPicsFlag derived for the decoder under test is applied for the HRD as follows:
               If AuNoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers in the DPB corresponding to all the nuh_layer_id values are emptied without output of the pictures they include, and the DPB fullness is set equal to 0 for all the nuh_layer_id values.   In another embodiment, if AuNoOutputOfPriorPicsFlag is equal to 1, all picture storage buffers in the DPB corresponding to all the nuh_layer_id value of the current picture are emptied without output of the pictures they include, and the DPB fullness is set equal to 0 for the nuh_layer_id value of the current picture.   Otherwise (AuNoOutputOfPriorPicsFlag is equal to 0), all picture storage buffers corresponding to all the nuh_layer_id values including a picture that is marked as “not needed for output” and “unused for reference” are emptied (without output), and all non-empty picture storage buffers in the DPB are emptied by repeatedly invoking the “bumping” process specified in subclause F.13.5.2.4, and the DPB fullness for all the nuh_layer_id values is set equal to 0.   In another embodiment:   Otherwise (AuNoOutputOfPriorPicsFlag is equal to 0), all picture storage buffers corresponding to the nuh_layer_id value of the current picture including a picture that is marked as “not needed for output” and “unused for reference” are emptied (without output), and all non-empty picture storage buffers in the DPB are emptied by repeatedly invoking the “bumping” process specified in subclause F.13.5.2.4, and the DPB fullness for the nuh_layer_id value of the current picture is set equal to 0.   
               
               

     Listing (2A) 
     In one configuration, for the proposed text in Listing (1), Listing (1A), Listing (2) and Listing (2A) above, all occurrences of “current picture” may be replaced by “current decoded picture”. 
     Listing (3) below provides an additional section for decoding to accommodate the present systems and methods. Listing (3) provides the sections of JCTVC-L1003 (i.e., the HEVC specification version 34) that would be changed to accommodate the present systems and methods. 
     Listing 3 
     8.3.2. Decoding Process for Reference Picture Set 
     When the current picture is an IRAP picture with NoRaslOutputFlag equal to 1, all reference pictures currently in the DPB corresponding to the nuh_layer_id value of the current picture (if any) are marked as “unused for reference.” 
     In another embodiment: When the current picture is an IRAP picture with NoRaslOutputFlag equal to 1, all reference pictures currently in the DPB corresponding to all the nuh_layer_id values (if any) are marked as “unused for reference.” 
     Listing (3) 
     Many different variants may be used for defining hybrid decoded picture buffer (DPB)  116  operations with various steps being picture based or access unit based. Tables (11)-(15) below list multiple variants of the steps and corresponding picture based/access unit (AU) based settings. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 46 
               
               
                   
                   
               
               
                   
                 Step  
                 Picture Based/AU Based 
               
               
                   
                   
               
             
            
               
                   
                 Removal  
                 Picture based  
               
               
                   
                 Output  
                 AU Based  
               
               
                   
                 Storage  
                 Picture Based  
               
               
                   
                 Marking  
                 AU Based for output marking,  
               
               
                   
                   
                 Picture based for reference marking  
               
               
                   
                 Additional Output  
                 AU Based 
               
               
                   
                   
               
               
                   
                 Table (11) 
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 47 
               
               
                   
                   
               
               
                   
                 Step  
                 Picture Based/AU Based 
               
               
                   
                   
               
             
            
               
                   
                 Removal  
                 Picture based  
               
               
                   
                 Output  
                 AU based  
               
               
                   
                 Storage  
                 AU based  
               
               
                   
                 Marking  
                 AU based for output marking,  
               
               
                   
                   
                 AU based for reference marking  
               
               
                   
                 Additional Output  
                 AU based 
               
               
                   
                   
               
               
                   
                 Table (12) 
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 48 
               
               
                   
                   
               
               
                   
                 Step  
                 Picture Based/AU Based 
               
               
                   
                   
               
             
            
               
                   
                 Removal  
                 AU based  
               
               
                   
                 Output  
                 AU based  
               
               
                   
                 Storage  
                 AU based  
               
               
                   
                 Marking  
                 AU based for output marking,  
               
               
                   
                   
                 AU based for reference marking  
               
               
                   
                 Additional Output  
                 AU based 
               
               
                   
                   
               
               
                   
                 Table (13) 
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 49 
               
               
                   
                   
               
               
                   
                 Step  
                 Picture Based/AU Based 
               
               
                   
                   
               
             
            
               
                   
                 Removal  
                 Picture based  
               
               
                   
                 Output  
                 AU based  
               
               
                   
                 Storage  
                 Picture based  
               
               
                   
                 Marking  
                 Picture based for output marking,  
               
               
                   
                   
                 Picture based for reference marking  
               
               
                   
                 Additional Output  
                 AU based 
               
               
                   
                   
               
               
                   
                 Table (14) 
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 50 
               
               
                   
                   
               
               
                   
                 Step  
                 Picture Based/AU Based 
               
               
                   
                   
               
             
            
               
                   
                 Removal  
                 Picture based  
               
               
                   
                 Output  
                 Picture based  
               
               
                   
                 Storage  
                 Picture based  
               
               
                   
                 Marking  
                 Picture based for output marking,  
               
               
                   
                   
                 Picture based for reference marking  
               
               
                   
                 Additional Output  
                 Picture based 
               
               
                   
                   
               
               
                   
                 Table (15) 
               
            
           
         
       
     
       FIG.  66    is a block diagram illustrating one configuration of a decoder  2404 . The decoder  2404  may be included in an electronic device  2402 . For example, the decoder  2404  may be a high-efficiency video coding (HEVC) decoder. The decoder  2404  and/or one or more of the elements illustrated as included in the decoder  2404  may be implemented in hardware, software or a combination of both. The decoder  2404  may receive a bitstream  2414  (e.g., one or more encoded pictures included in the bitstream  2414 ) for decoding. In some configurations, the received bitstream  2414  may include received overhead information, such as a received slice header, received PPS, received buffer description information, etc. The encoded pictures included in the bitstream  2414  may include one or more encoded reference pictures and/or one or more other encoded pictures. 
     Received symbols (in the one or more encoded pictures included in the bitstream  2414 ) may be entropy decoded by an entropy decoding module  454 , thereby producing a motion information signal  456  and quantized, scaled and/or transformed coefficients  458 . 
     The motion information signal  456  may be combined with a portion of a reference frame signal  484  from a frame memory  464  at a motion compensation module  460 , which may produce an inter-frame prediction signal  468 . The quantized, descaled and/or transformed coefficients  458  may be inverse quantized, scaled and inverse transformed by an inverse module  462 , thereby producing a decoded residual signal  470 . The decoded residual signal  470  may be added to a prediction signal  478  to produce a combined signal  472 . The prediction signal  478  may be a signal selected from either the inter-frame prediction signal  468  or an intra-frame prediction signal  476  produced by an intra-frame prediction module  474 . In some configurations, this signal selection may be based on (e.g., controlled by) the bitstream  2414 . 
     The intra-frame prediction signal  476  may be predicted from previously decoded information from the combined signal  472  (in the current frame, for example). The combined signal  472  may also be filtered by a de-blocking filter  480 . The resulting filtered signal  482  may be written to frame memory  464 . The resulting filtered signal  482  may include a decoded picture. 
     The frame memory  464  may include a decoded picture buffer (DPB)  2416  as described herein. The decoded picture buffer (DPB)  2416  may be capable of hybrid decoded picture buffer (DPB)  116  operations. The decoded picture buffer (DPB)  2416  may include one or more decoded pictures that may be maintained as short or long term reference frames. The frame memory  464  may also include overhead information corresponding to the decoded pictures. For example, the frame memory  464  may include slice headers, video parameter set (VPS) information, sequence parameter set (SPS) information, picture parameter set (PPS) information, cycle parameters, buffer description information, etc. One or more of these pieces of information may be signaled from an encoder (e.g., encoder  2108 , overhead signaling module  2112 ). 
       FIG.  67 A  is a block diagram illustrating the use of both an enhancement layer and a base layer for video coding with separate decoded picture buffers (DPBs)  516   a - b  and separate hybrid decoded picture buffer (DPB) operation modules  520   a - b  for the base layer and the enhancement layer. A first electronic device  502   a  and a second electronic device  502   b  are illustrated. The first electronic device  502   a  may include a video encoder  508  that includes an enhancement layer encoder  526  and a base layer encoder  528 . Each of the elements included within the first electronic device  502   a  (i.e., the enhancement layer encoder  526  and the base layer encoder  528 ) may be implemented in hardware, software or a combination of both. The first electronic device  502   a  may obtain an input picture  2506 . In some configurations, the input picture  2506  may be captured on the first electronic device  502   a  using an image sensor, retrieved from memory or received from another electronic device  502 . 
     The enhancement layer encoder  526  may encode the input picture  2506  to produce encoded data. For example, the enhancement layer encoder  526  may encode a series of input pictures  2506  (e.g., video). The encoded data may be included in an encoded enhancement layer video bitstream  530 . The enhancement layer encoder  526  may generate overhead signaling based on the input picture  2506 . 
     The enhancement layer video decoder  534  may include a decoded picture buffer (DPB)  516   a  and a hybrid decoded picture buffer (DPB) operation module  520   a . Likewise, the base layer decoder  536  may include a decoded picture buffer (DPB)  516   b  and a hybrid decoded picture buffer (DPB) operation module  520   b.    
     The base layer encoder  528  may also encode the input picture  2506 . In one configuration, the same input picture  2506  used by the enhancement layer encoder  526  may also be used by the base layer encoder  528 . In another configuration, a different (but similar) input picture than the input picture  2506  used by the enhancement layer encoder  526  may be used by the base layer encoder  528 . For example, for signal-to-noise ratio (SNR) scalability (also referred to as quality scalability), the same input picture  2506  may be used by both the enhancement layer encoder  526  and the base layer encoder  528 . As another example, for spatial scalability, a downsampled picture may be used by the base layer encoder  528 . In yet another example, for multi-view scalability, a different view picture may be used by the base layer encoder  528 . The base layer encoder  528  may produce encoded data included in an encoded base layer video bitstream  532 . 
     The encoded enhancement layer video bitstream  530  and the encoded base layer video bitstream  532  may each include encoded data based on the input picture  2506 . In one example, the encoded enhancement layer video bitstream  530  and the encoded base layer video bitstream  532  may include encoded picture data. In some configurations, the encoded enhancement layer video bitstream  530  and/or the encoded base layer video bitstream  532  may also include overhead data, such as sequence parameter set (SPS) information, picture parameter set (PPS) information, video parameter set (VPS) information, slice header information, etc. 
     The encoded enhancement layer video bitstream  530  may be provided to the second electronic device  502   b . Likewise, the encoded base layer video bitstream  532  may be provided to the second electronic device  502   b . The second electronic device  502   b  may include a video decoder  2504 . The video decoder  2504  may include an enhancement layer decoder  534  and a base layer decoder  536 . In one configuration, the encoded base layer video bitstream  530  is decoded by the base layer decoder  536  while the encoded enhancement layer video bitstream  530  is decoded by the enhancement layer decoder  534 . 
     In one example, the encoded enhancement layer video bitstream  530  and the encoded base layer video bitstream  532  may be transmitted to the second electronic device  502   b  using a wired or wireless link. In some cases, this may be done over a network, such as the Internet, a Local Area Network (LAN) or other type of network for communicating between devices. It should be noted that in some configurations, the encoders (i.e., the enhancement layer encoder  526  and the base layer encoder  528 ) and the decoder  2504  (e.g., the base layer decoder  536  and the enhancement layer decoder  534 ) may be implemented on the same electronic device  502  (i.e., the first electronic device  502   a  and the second electronic device  502   b  may be part of a single electronic device  502 ). In an implementation where the encoders and decoders are implemented on the same electronic device  502 , for instance, the encoded enhancement layer video bitstream  530  and the encoded base layer video bitstream  532  may be made available to the video decoder  2504  in a variety of ways. For example, the encoded enhancement layer video bitstream  530  and the encoded base layer video bitstream  532  may be provided over a bus to the video decoder  2504  or stored in memory for retrieval by the video decoder  2504 . 
     The video decoder  2504  may generate one or more decoded pictures based on the encoded enhancement layer video bitstream  530  and the encoded base layer video bitstream  532 . A decoded picture  2118  (which may include an enhancement layer decoded picture  538  and a base layer decoded picture  540 ) may be displayed, played back, stored in memory and/or transmitted to another device, etc. 
     In one example, the decoded picture  2118  may be transmitted to another device or back to the first electronic device  502   a . The decoded picture  2118  may also be stored or otherwise maintained on the second electronic device  502   b . In another example, the second electronic device  502   b  may display the decoded picture  2118 . In other configurations, the decoded picture  2118  includes elements of the input picture  2506  with different properties based on the encoding and other operations performed on the bitstream  2114 . In some configurations, the decoded picture  2118  may be included in a picture stream with a different resolution, format, specifications or other attribute from the input picture  2506 . 
       FIG.  67 B  is a block diagram illustrating the use of a shared decoded picture buffer (DPB)  516   c  and a shared hybrid decoded picture buffer (DPB) operation module  520   c  for the base layer and the enhancement layer.  FIG.  67 B  includes the same components as that of  FIG.  67 A  except that the enhancement layer video decoder  534  and the base layer decoder  536  share both a decoded picture buffer (DPB)  516   c  and a hybrid decoded picture buffer (DPB) operation module  520   c.    
       FIG.  68    is a timing diagram illustrating hybrid decoded picture buffer (DPB)  116  operation. The hybrid decoded picture buffer (DPB)  116  operations of  FIG.  68    show the steps of a preferred variant where removal, storage and reference marking are picture based and output, output marking and additional output are access unit (AU) based. An ideal decoded picture buffer (DPB)  116  and hypothetical reference decoder (HRD) may operate in such a manner that the various individual steps shown (e.g., removal  621   a - b , output  623 , storage  625   a - c , marking  627   a - c ,  629  and additional output  631 ) are all performed instantaneously. The sequence of these steps and the timing offsets are illustrated between individual steps for illustration purposes. For output timing decoder conformance, the timing (relative to the delivery time of the first bit) of a picture output is the same for both the hypothetical reference decoder (HRD) and the decoder under test (DUT) up to a fixed delay. As such, the timing offset illustrated could happen for a DUT which introduces a fixed delay compared to an HRD. 
     The steps for a decoded picture buffer (DPB)  116  of the first enhancement layer (EL 1 )  2642   a , a decoded picture buffer (DPB)  116  of the second enhancement layer (EL 2 )  2642   b  and a decoded picture buffer (DPB)  116  of the base layer (BL)  2644  are illustrated. A coded picture buffer (CPB) removal time  2646  is illustrated. After the coded picture buffer (CPB) removal time  2646 , a picture based removal (without output)  621   a  may be performed by the decoded picture buffer (DPB)  116  of the second enhancement layer (EL 2 )  2642   b  and a picture based removal (without output)  621   b  may be performed by the decoded picture buffer (DPB)  116  of the base layer (BL)  2644 . After a timing offset, an access unit (AU) based picture output (bumping)  623  may be performed by the decoded picture buffer (DPB)  116  of the base layer (BL)  2644 , the decoded picture buffer (DPB)  116  of the first enhancement layer (EL 1 )  2642   a  and the decoded picture buffer (DPB)  116  of the second enhancement layer (EL 2 )  2642   b.    
     After another timing offset, the current decoded picture related process  613  is illustrated. A picture based storage step  625   a - c  may be performed by the decoded picture buffer (DPB)  116  of the base layer (BL)  2644 , the decoded picture buffer (DPB)  116  of the first enhancement layer (EL 1 )  2642   a  and the decoded picture buffer (DPB)  116  of the second enhancement layer (EL 2 )  2642   b . The storage step may be performed after each of the base layer (BL)  2644 , the first enhancement layer (EL 1 )  2642   a  and the second enhancement layer (EL 2 )  2642   b  pictures are decoded. The storage step  625  may be further subdivided. In the storage steps  625 , a decoded picture is stored in the decoded picture buffer (DPB)  116  in an empty storage buffer and the decoded picture buffer (DPB) fullness is incremented by one. Also, when a picture is removed (without output) from the decoded picture buffer (DPB)  116 , the decoded picture buffer (DPB) fullness is decremented by one. Similarly, when a picture is bumped from the decoded picture buffer (DPB)  116  (during either bumping or additional bumping), the decoded picture buffer (DPB) fullness is decremented by one. 
     The decoded picture buffer (DPB)  116  may include separately identified and managed picture buffers for decoded pictures having different characteristics. For example, the decoded picture buffer (DPB)  116  may include separately identified and managed picture buffers for decoded pictures with different resolutions, different bit-depths and/or different color chromaticity. 
     A decoded picture may instead be stored in a common pool of picture storage buffers in the decoded picture buffer (DPB)  116 . For example, two additional sub-cases may be used to determine the decoded picture buffer (DPB)  116  size constraints that affect the bumping/removal process and level definitions. In a byte based decoded picture buffer (DPB)  116  constraint, a decoded picture may be stored with consideration for the size based on resolution and/or bit-depth. The decoded picture buffer (DPB)  116  size constraints may be defined as a byte limit that considers resolution and bit-depth of each decoded picture. In a picture unit based decoded picture buffer (DPB)  116  constraint, a decoded picture may be stored (and is considered to take one picture buffer slot). The decoded picture buffer (DPB)  116  size constraints may then be defined as a number of picture slots limit without considering resolution and bit-depth of each decoded picture. 
     In one configuration, the decoded picture buffer (DPB) fullness may be tracked per layer. For example, the decoded picture buffer (DPB)  116  size constraints may be signaled, and bumping may be applied, per layer. Where each layer includes its own picture storage buffers a variable DPBFullness[nuh_layer_id] could be used to track to the decoded picture buffer (DPB) fullness of each layer. When a picture is removed from a layer with a layer ID value equal to nuh_layer_id, the variable DPBFullness[nuh_layer_id] may be set equal to DPBFullness[nuh_layer_id]- 1  (i.e., DPBFullness[nuh_layer_id] may be decremented by one). In this case, the picture was removed from a picture storage buffer PSB[nuh_layer_id]. 
     Similarly, when a currently decoded picture with a layer ID value equal to nuh_layer_id is stored in the decoded picture buffer (DPB)  116 , the variable DPBFullness[nuh_layer_id] is set equal to DPBFullness[nuh_layer_id]+1 (i.e., DPBFullness[nuh_layer_id] is incremented by one). In this case, the picture was stored into a picture storage buffer PSB[nuh_layer_id]. 
     The decoded picture buffer (DPB) fullness could also be tracked for an output layer set. The decoded picture buffer (DPB)  116  size constraints may then be signaled, and bumping may be applied, based on the constraints specified for an output layer set. A DPBFullness value could be tracked for the output layer set which is associated with the operation point under test. Thus, when a picture is removed from a layer belonging to the output layer set, the value of the decoded picture buffer (DPB) fullness may be decremented by one as DPBFullness=DPBFullness−1. Likewise, when a currently decoded picture is stored in the decoded picture buffer (DPB)  116 , the decoded picture buffer (DPB) fullness may be decremented by one as DPBFullness=DPBFullness+1. 
     Within the current decoded picture related process  613 , the marking process  611  is illustrated. The marking process  611  may include reference marking  627   a - c  and output marking  629 . After a timing offset from the storage steps  625   a - c , a picture based reference marking step  627   a - c  may be performed by the decoded picture buffer (DPB)  116  of the base layer (BL)  2644 , the decoded picture buffer (DPB)  116  of the first enhancement layer (EL 1 )  2642   a  and the decoded picture buffer (DPB)  116  of the second enhancement layer (EL 2 )  2642   b . After another timing offset, an access unit (AU) based output marking step  629  may be performed by the decoded picture buffer (DPB)  116  of the base layer (BL)  2644 , the decoded picture buffer (DPB)  116  of the first enhancement layer (EL 1 )  2642   a  and the decoded picture buffer (DPB)  116  of the second enhancement layer (EL 2 )  2642   b . Once the current decoded picture related process  613  is completed, an access unit (AU) based picture output (additional bumping) step  631  may be performed by the decoded picture buffer (DPB)  116  of the base layer (BL)  2644 , the decoded picture buffer (DPB)  116  of the first enhancement layer (EL 1 )  2642   a  and the decoded picture buffer (DPB)  116  of the second enhancement layer (EL 2 )  2642   b.    
       FIG.  69    is a block diagram illustrating structure and timing for network abstraction layer (NAL) units of layers for coded pictures and access units (AUs) when the second enhancement layer (EL 2 )  942   b  has a lower picture rate than the base layer (BL)  944  and the first enhancement layer (EL 1 )  942   a . The NAL units of an EL 1  coded picture  953   a  are illustrated along the first enhancement layer (EL 1 )  942   a . The NAL units of an EL 2  coded picture  953   b  are illustrated along the second enhancement layer (EL 2 )  942   b . The NAL units of a base layer coded picture  953   c  are illustrated along the base layer (BL)  944 . 
     At time t 1 , the NAL units of an EL 1  coded picture  953   a , the NAL units of an EL 2  coded picture  953   b  and the NAL units of a base layer coded picture  953   c  are part of the access unit (AU)  955   a . At time t 2 , the NAL units of an EL 1  coded picture  953   a  and the NAL units of a base layer coded picture  953   c  are part of the access unit (AU)  955   b . At time t 3 , the NAL units of an EL 1  coded picture  953   a , the NAL units of an EL 2  coded picture  953   b  and the NAL units of a base layer coded picture  953   c  are part of the access unit (AU)  955   c . At time t 4 , the NAL units of an EL 1  coded picture  953   a  and the NAL units of a base layer coded picture  953   c  are part of the access unit (AU)  955   d.    
       FIG.  70    is a block diagram illustrating structure and timing for network abstraction layer (NAL) units of layers for coded pictures and access units (AUs) when the base layer (BL)  1044  has a lower picture rate than the first enhancement layer (EL 1 )  1042   a  and the second enhancement layer (EL 2 )  1042   b . The NAL units of an EL 1  coded picture  1053   a  are illustrated along the first enhancement layer (EL 1 )  1042   a . The NAL units of an EL 2  coded picture  1053   b  are illustrated along the second enhancement layer (EL 2 )  1042   b . The NAL units of a base layer coded picture  1053   c  are illustrated along the base layer (BL)  1044 . 
     At time t 1 , the NAL units of an EL 1  coded picture  1053   a , the NAL units of an EL 2  coded picture  1053   b  and the NAL units of a base layer coded picture  1053   c  are part of the access unit (AU)  1055   a . At time t 2 , the NAL units of an EL 1  coded picture  1053   a  and the NAL units of a EL 2  coded picture  1053   b  are part of the access unit (AU)  1055   b . At time t 3 , the NAL units of an EL 1  coded picture  1053   a , the NAL units of an EL 2  coded picture  1053   b  and the NAL units of a base layer coded picture  1053   c  are part of the access unit (AU)  1055   c . At time t 4 , the NAL units of an EL 1  coded picture  1053   a  and the NAL units of an EL 1  coded picture  1053   b  are part of the access unit (AU)  1055   d.    
     The term “computer-readable medium” refers to any available medium that can be accessed by a computer or a processor. The term “computer-readable medium,” as used herein, may denote a computer- and/or processor-readable medium that is nontransitory and tangible. By way of example, and not limitation, a computer-readable or processor-readable medium may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer or processor. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray (registered trademark) disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. 
     It should be noted that one or more of the methods described herein may be implemented in and/or performed using hardware. For example, one or more of the methods or approaches described herein may be implemented in and/or realized using a chipset, an ASIC, a LSI or integrated circuit, etc. 
     Each of the methods disclosed herein comprises one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another and/or combined into a single step without departing from the scope of the claims. In other words, unless a specific order of steps or actions is required for proper operation of the method that is being described, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims. 
     It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the systems, methods, and apparatus described herein without departing from the scope of the claims.