Patent Publication Number: US-10334277-B2

Title: Signaling target display parameters of color remapping information supplemental enhancement information messages

Description:
This application claims the benefit of U.S. Provisional Application No. 62/383,356, filed Sep. 2, 2016, the entire content of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to video processing. 
     BACKGROUND 
     Digital video capabilities may be incorporated into a wide range of devices, including digital televisions, digital direct broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, digital cameras, digital recording devices, digital media players, video gaming devices, video game consoles, cellular or satellite radio telephones, so-called “smart phones,” video teleconferencing devices, video streaming devices, and the like. Digital video devices implement video coding techniques, such as those described in the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264/MPEG-4, Part 10, Advanced Video Coding (AVC), ITU-T H.265, High Efficiency Video Coding (HEVC), and extensions of such standards. The video devices may transmit, receive, encode, decode, and/or store digital video information more efficiently by implementing such video coding techniques. 
     Video coding techniques include spatial (intra-picture) prediction and/or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. For block-based video coding, a video slice (e.g., a video frame or a portion of a video frame) may be partitioned into video blocks, which may also be referred to as treeblocks, coding units (CUs) and/or coding nodes. Video blocks in an intra-coded (I) slice of a picture are encoded using spatial prediction with respect to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture may use spatial prediction with respect to reference samples in neighboring blocks in the same picture or temporal prediction with respect to reference samples in other reference pictures. Pictures may be referred to as frames, and reference pictures may be referred to as reference frames. 
     Spatial or temporal prediction results in a predictive block for a block to be coded. Residual data represents pixel differences between the original block to be coded and the predictive block. An inter-coded block is encoded according to a motion vector that points to a block of reference samples forming the predictive block, and the residual data indicating the difference between the coded block and the predictive block. An intra-coded block is encoded according to an intra-coding mode and the residual data. For further compression, the residual data may be transformed from the pixel domain to a transform domain, resulting in residual transform coefficients, which then may be quantized. The quantized transform coefficients, initially arranged in a two-dimensional array, may be scanned in order to produce a one-dimensional vector of transform coefficients, and entropy coding may be applied to achieve even more compression. 
     The total number of color values that may be captured, coded, and displayed may be defined by a color gamut. A color gamut refers to the range of colors that a device may capture (e.g., a camera) or reproduce (e.g., a display). Often, color gamuts differ from device to device. For video coding, a predefined color gamut for video data may be used such that each device in the video coding process may be configured to process pixel values in the same color gamut. Some color gamuts are defined with a larger range of colors than color gamuts that have been traditionally used for video coding. Such color gamuts with a larger range of colors may be referred to as a wide color gamut (WCG). 
     Another aspect of video data is dynamic range. Dynamic range is typically defined as the ratio between the maximum and minimum brightness (e.g., luminance) of a video signal. The dynamic range of common video data used in the past is considered to have a standard dynamic range (SDR). Other example specifications for video data define color data that has a larger ratio between the maximum and minimum brightness. Such video data may be described as having a high dynamic range (HDR). 
     SUMMARY 
     In general, this disclosure describes techniques for communicating optimal coding parameters between a source device and a sink device. The sink device may receive, in a bitstream, video data and a group of one or more supplemental enhancement information (SEI) messages, wherein each SEI message comprises indications of a set of display capabilities and a set of remapping parameters (e.g., color remapping information). The sink device may then, for each SEI message of the group of one or more SEI messages, compare the respective set of display capabilities indicated in the respective SEI message with a target set of display capabilities for the sink device. Responsive to determining that a first set of display capabilities indicated by a first SEI message is compatible with the target set of display capabilities, the sink device may adapt the video data using a respective set of remapping parameters indicated by the first SEI message. 
     In one example, the disclosure is directed to a method of processing video data by a sink device, the method including: receiving, in a bitstream, the video data; receiving, in the bitstream, a group of one or more supplemental enhancement information (SEI) messages, wherein each SEI message comprises an indication of a set of one or more display capabilities and an indication of a set of one or more remapping parameters; for each SEI message of the group of one or more SEI messages, comparing the respective set of one or more display capabilities indicated in the respective SEI message with a target set of one or more display capabilities for the sink device to determine a compatibility of the respective set of one or more display capabilities with the target set of one or more display capabilities; and responsive to determining that a first set of one or more display capabilities indicated by a first SEI message of the group of one or more SEI messages is compatible with the target set of one or more display capabilities for the sink device, adapting the video data using a respective set of one or more remapping parameters indicated by the first SEI message. 
     In another example, the disclosure is directed to a sink device for processing video data, the sink device including: a memory for storing video data; and one or more processors configured to: receive, in a bitstream, the video data; receive, in the bitstream, a group of one or more supplemental enhancement information (SEI) messages, wherein each SEI message comprises an indication of a set of one or more display capabilities and an indication of a set of one or more remapping parameters; for each SEI message of the group of one or more SEI messages, compare the respective set of one or more display capabilities indicated in the respective SEI message with a target set of one or more display capabilities for the sink device to determine a compatibility of the respective set of one or more display capabilities with the target set of one or more display capabilities; and responsive to determining that a first set of one or more display capabilities indicated by a first SEI message of the group of one or more SEI messages is compatible with the target set of one or more display capabilities for the sink device, adapt the video data using a respective set of one or more remapping parameters indicated by the first SEI message. 
     In another example, the disclosure is directed to a non-transitory computer readable storage medium storing instructions that, when executed by one or more processors of a sink device, cause the one or more processors to: receive, in a bitstream, the video data; receive, in the bitstream, a group of one or more supplemental enhancement information (SEI) messages, wherein each SEI message comprises an indication of a set of one or more display capabilities and an indication of a set of one or more remapping parameters; for each SEI message of the group of one or more SEI messages, compare the respective set of one or more display capabilities indicated in the respective SEI message with a target set of one or more display capabilities for the sink device to determine a compatibility of the respective set of one or more display capabilities with the target set of one or more display capabilities; and responsive to determining that a first set of one or more display capabilities indicated by a first SEI message of the group of one or more SEI messages is compatible with the target set of one or more display capabilities for the sink device, adapt the video data using a respective set of one or more remapping parameters indicated by the first SEI message. 
     In another example, the disclosure is directed to an apparatus including: means for receiving, in a bitstream, the video data; means for receiving, in the bitstream, a group of one or more supplemental enhancement information (SEI) messages, wherein each SEI message comprises an indication of a set of one or more display capabilities and an indication of a set of one or more remapping parameters; for each SEI message of the group of one or more SEI messages, means for comparing the respective set of one or more display capabilities indicated in the respective SEI message with a target set of one or more display capabilities for the sink device to determine a compatibility of the respective set of one or more display capabilities with the target set of one or more display capabilities; and responsive to determining that a first set of one or more display capabilities indicated by a first SEI message of the group of one or more SEI messages is compatible with the target set of one or more display capabilities for the sink device, means for adapting the video data using a respective set of one or more remapping parameters indicated by the first SEI message. 
     In another example, the disclosure is directed to a method of processing video data by a source device, the method comprising: determining, for a first set of one or more display capabilities, a first set of one or more remapping parameters for the video data; coding, in a first supplemental enhancement information (SEI) message, the first set of one or more display capabilities and the first set of one or more remapping parameters; and sending, to a sink device in a bitstream, the first SEI message and the video data. 
     In another example, the disclosure is directed to a source device for processing video data, the sink device including: a memory for storing video data; and one or more processors configured to: determine, for a first set of one or more display capabilities, a first set of one or more remapping parameters for the video data; code, in a first supplemental enhancement information (SEI) message, the first set of one or more display capabilities and the first set of one or more remapping parameters; and send, to a sink device in a bitstream, the first SEI message and the video data. 
     In another example, the disclosure is directed to a non-transitory computer readable storage medium storing instructions that, when executed by one or more processors of a source device, cause the one or more processors to: determine, for a first set of one or more display capabilities, a first set of one or more remapping parameters for the video data; code, in a first supplemental enhancement information (SEI) message, the first set of one or more display capabilities and the first set of one or more remapping parameters; and send, to a sink device in a bitstream, the first SEI message and the video data. 
     In another example, the disclosure is directed to an apparatus including: means for determining, for a first set of one or more display capabilities, a first set of one or more remapping parameters for the video data; means for coding, in a first supplemental enhancement information (SEI) message, the first set of one or more display capabilities and the first set of one or more remapping parameters; and means for sending, to a sink device in a bitstream, the first SEI message and the video data. 
     The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating an example system that includes a video compilation device, a client device, and a sink device, where the sink device configured to receive remapping parameters from the client device, in accordance with the techniques of this disclosure. 
         FIG. 2  is a conceptual diagram illustrating processing steps signaled by a color remapping information (CRI) supplemental enhancement information (SEI) message. 
         FIG. 3  is a conceptual diagram illustrating the concepts of HDR data. 
         FIG. 4  is a conceptual diagram illustrating example color gamuts. 
         FIG. 5  is a flow diagram illustrating an example of HDR/WCG representation conversion. 
         FIG. 6  is a flow diagram illustrating an example of HDR/WCG inverse conversion. 
         FIG. 7  is conceptual diagram illustrating example of Electro-optical transfer functions (EOTF) utilized for video data conversion (including SDR and HDR) from perceptually uniform code levels to linear luminance. 
         FIG. 8  is a block diagram illustrating an example of a video encoder. 
         FIG. 9  is a block diagram illustrating an example of a video decoder. 
         FIG. 10  is a block diagram illustrating an example of a sink device that may implement techniques of this disclosure. 
         FIG. 11  is a flow diagram illustrating example techniques of a sink device configured to receive CRI SEI messages from a source device, in accordance with the techniques of this disclosure. 
         FIG. 12  is a flow diagram illustrating example techniques of a source device configured to send CRI SEI messages to a sink device, in accordance with the techniques of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure is related to the processing and/or coding of video data to improve the application the color remapping information (CRI) supplemental enhancement information (SEI) messages for mapping the video data from a first color space to a second color space. More specifically, the techniques of this disclosure include means to enables the signaling of CRI SEI messages for display adaptation to target displays of different capabilities. For instance, the source device may send multiple CRI SEI messages to a sink device. Each CRI SEI message may include an indication of a set of display parameters and an indication of a corresponding set of remapping parameters. The sink device may compare the various sets of display parameters with a target set of display parameters for the sink device. The sink device may select the CRI SEI message with the display parameters that most closely match the target display parameters for the sink device and use the corresponding remapping parameters to adapt the video data for the sink device. The techniques of this disclosure are applicable for digital video interfaces such as those that support signaling of ultra high-definition (UHD), high dynamic range (HDR), and wide color gamut (WCG) video signals to end devices/displays or TVs. 
     In this way, the sink device may more efficiently process the received video data, as the color of the video data may be more closely aligned with the color gamut of the sink device. This may result in the sink device displaying a clearer image with colors more true to the original video data from the source device, as well as reduced power consumption. Further, enabling the sink device to select remapping parameters suited closest to its capabilities (i.e., more parameters associated with its capabilities) may enable the source device to process the content into a format that is supported or preferable by the sink device. This may reduce the complexity of design of sink devices for processes including display adaptation and color volume transformation, as some of these processes may be conducted at the source device. The techniques described herein may also enable the source device to perform guided mapping of the content to the HDR or WCG capabilities of the sink device to preserve artistic intent. The techniques and devices described herein may improve compression efficiency of hybrid-based video coding systems (e.g., H.265/HEVC, H.264/AVC, etc.) utilized for coding CRI SEI messages and related video data. 
     Video coding standards, including hybrid-based video coding standards include ITU-T H.261, ISO/IEC MPEG-1 Visual, ITU-T H.262 or ISO/IEC MPEG-2 Visual, ITU-T H.263, ISO/IEC MPEG-4 Visual and ITU-T H.264 (also known as ISO/IEC MPEG-4 AVC), including its Scalable Video Coding (SVC) and Multi-view Video Coding (MVC) extensions. The design of a new video coding standard, namely High Efficiency Video coding (HEVC, also called H.265), has been finalized by the Joint Collaboration Team on Video Coding (JCT-VC) of ITU-T Video Coding Experts Group (VCEG) and ISO/IEC Motion Picture Experts Group (MPEG). An HEVC draft specification referred to as HEVC Working Draft 10 (WD10), Bross et al., “High efficiency video coding (HEVC) text specification draft 10 (for FDIS &amp; Last Call),” Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11, 12th Meeting: Geneva, CH, 14-23 Jan. 2013, JCTVC-L1003v34. The finalized HEVC standard is referred to as HEVC version 1. 
     A defect report includes Wang et al., “High efficiency video coding (HEVC) Defect Report,” Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11, 14th Meeting: Vienna, AT, 25 Jul.-2 Aug. 2013, JCTVC-N1003v1. The finalized HEVC standard document is published as ITU-T H.265, Series H: Audiovisual and Multimedia Systems, Infrastructure of audiovisual services—Coding of moving video, High efficiency video coding, Telecommunication Standardization Sector of International Telecommunication Union (ITU), April 2013, and another version of the finalized HEVC standard was published in October 2014. 
     Following the decoding process, uncompressed video signal may be signaled through a high-speed digital physical interface to an end consumer device, such as a display or a TV. Protocols, requirements, and recommendations for the utilization of uncompressed digital interfaces by consumer electronics devices such as Digital Televisions (DTVs), digital cable, satellite or terrestrial set-top boxes (STBs), and related peripheral devices including, but not limited to DVD players/recorders, and other related Sources or Sinks are specified in CTA-861 specification. 
       FIG. 1  is a block diagram illustrating an example sink device configured to receive remapping parameters from a source device, in accordance with the techniques of this disclosure. As shown in  FIG. 1 , system  10  includes a video compilation device  12  that provides encoded video data to be decoded at a later time by a client device  14 , which sends the decoded video data to sink device  32  for display. In particular, video compilation device  12  provides the video data to client device  14  via a computer-readable medium  16 . Video compilation device  12 , client device  14 , and sink device  32  may comprise any of a wide range of devices, including desktop computers, notebook (i.e., laptop) computers, tablet computers, set-top boxes, telephone handsets such as so-called “smart” phones, so-called “smart” pads, televisions, cameras, display devices, digital media players, video gaming consoles, video streaming devices, or the like. In some cases, video compilation device  12  and client device  14  may be equipped for wireless communication. 
     Client device  14  may receive the encoded video data to be decoded via computer-readable medium  16 . Computer-readable medium  16  may comprise any type of medium or device capable of moving the encoded video data from video compilation device  12  to client device  14 . In one example, computer-readable medium  16  may comprise a communication medium to enable video compilation device  12  to transmit encoded video data directly to client device  14  in real-time. The encoded video data may be modulated according to a communication standard, such as a wired or wireless communication protocol, and transmitted to client device  14 . The communication medium may comprise any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form part of a packet-based network, such as a local area network, a wide-area network, or a global network such as the Internet. The communication medium may include routers, switches, base stations, or any other equipment that may be useful to facilitate communication from video compilation device  12  to client device  14 . 
     In other examples, computer-readable medium  16  may include non-transitory storage media, such as a hard disk, flash drive, compact disc, digital video disc, Blu-ray disc, or other computer-readable media. In some examples, a network server (not shown) may receive encoded video data from video compilation device  12  and provide the encoded video data to client device  14 , e.g., via network transmission. Similarly, a computing device of a medium production facility, such as a disc stamping facility, may receive encoded video data from video compilation device  12  and produce a disc containing the encoded video data. Therefore, computer-readable medium  16  may be understood to include one or more computer-readable media of various forms, in various examples. 
     In some examples, encoded data may be output from output interface  22  to a storage device. Similarly, encoded data may be accessed from the storage device by input interface. The storage device may include any of a variety of distributed or locally accessed data storage media such as a hard drive, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage media for storing encoded video data. In a further example, the storage device may correspond to a file server or another intermediate storage device that may store the encoded video generated by video compilation device  12 . Client device  14  may access stored video data from the storage device via streaming or download. The file server may be any type of server capable of storing encoded video data and transmitting encoded video data to the client device  14 . Example file servers include a web server (e.g., for a website), an FTP server, network attached storage (NAS) devices, or a local disk drive. Client device  14  may access the encoded video data through any standard data connection, including an Internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., DSL, cable modem, etc.), or a combination of both that is suitable for accessing encoded video data stored on a file server. The transmission of encoded video data from the storage device may be a streaming transmission, a download transmission, or a combination thereof. 
     The techniques of this disclosure are not necessarily limited to wireless applications or settings. The techniques may be applied to video coding in support of any of a variety of multimedia applications, such as over-the-air television broadcasts, cable television transmissions, satellite television transmissions, Internet streaming video transmissions, such as dynamic adaptive streaming over HTTP (DASH), digital video that is encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications. In some examples, system  10  may be configured to support one-way or two-way video transmission to support applications such as video streaming, video playback, video broadcasting, and/or video telephony. 
     In the example of  FIG. 1 , video compilation device  12  includes video source  18 , video preprocessor  19 , video encoder  20 , and output interface  22 . Client device  14  includes input interface  28 , video decoder  30 , and video postprocessor  31 . Sink device  32  includes processor  33 . Video postprocessor  31  of client device  14  and processor  33  of sink device  32  may be configured to implement the techniques of this disclosure, including signaling and related operations applied to video data in certain color spaces to enable more efficient compression of HDR and WCG video data. In some examples, video preprocessor  19  may be separate from video encoder  20 . In other examples, video preprocessor  19  may be part of video encoder  20 . In other examples, a source device and a destination device may include other components or arrangements. For example, video compilation device  12  may receive video data from an external video source  18 , such as an external camera. Likewise, client device  14  may include sink device  32  as an integrated sink device rather than a separate device. 
     The illustrated system  10  of  FIG. 1  is merely one example. Techniques for processing HDR and WCG video data may be performed by any digital video encoding and/or video decoding device. Moreover, the techniques of this disclosure may also be performed by a video preprocessor and/or video postprocessor. A video preprocessor may be any device configured to process video data before encoding (e.g., before HEVC encoding). A video postprocessor may be any device configured to process video data after decoding (e.g., after HEVC decoding). Video compilation device  12 , client device  14 , and sink device  32  are merely examples of such coding devices in which video compilation device  12  generates coded video data for transmission to client device  14 . In some examples, devices  12 ,  14 , and  32  may operate in a substantially symmetrical manner such that each of devices  12 ,  14 , and  32  include video encoding and decoding components, as well as a video preprocessor and a video postprocessor (e.g., video preprocessor  19  and video postprocessor  31 , respectively). Hence, system  10  may support one-way or two-way video transmission between video devices  12 ,  14 , e.g., for video streaming, video playback, video broadcasting, or video telephony. 
     Video source  18  of video compilation device  12  may include a video capture device, such as a video camera, a video archive containing previously captured video, and/or a video feed interface to receive video from a video content provider. As a further alternative, video source  18  may generate computer graphics-based data as the source video, or a combination of live video, archived video, and computer-generated video. In some cases, if video source  18  is a video camera, video compilation device  12  and client device  14  may form so-called camera phones or video phones. As mentioned above, however, the techniques described in this disclosure may be applicable to video coding and video processing, in general, and may be applied to wireless and/or wired applications. In each case, the captured, pre-captured, or computer-generated video may be encoded by video encoder  20 . The encoded video information may then be output by output interface  22  onto a computer-readable medium  16 . 
     Input interface  28  of client device  14  receives information from computer-readable medium  16 . The information of computer-readable medium  16  may include syntax information defined by video encoder  20 , which is also used by video decoder  30 , that includes syntax elements that describe characteristics and/or processing of blocks and other coded units, e.g., groups of pictures (GOPs). Sink device  32  displays the decoded video data to a user, and may comprise any of a variety of display devices such as a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device. 
     Video encoder  20  and video decoder  30  each may be implemented as any of a variety of suitable encoder circuitry, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware or any combinations thereof. When the techniques are implemented partially in software, a device may store instructions for the software in a suitable, non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Each of video encoder  20  and video decoder  30  may be included in one or more encoders or decoders, either of which may be integrated as part of a combined encoder/decoder (CODEC) in a respective device. 
     Video preprocessor  19  and video postprocessor  31  each may be implemented as any of a variety of suitable encoder circuitry, such as one or more microprocessors, DSPs, ASICs, FPGAs, discrete logic, software, hardware, firmware or any combinations thereof. When the techniques are implemented partially in software, a device may store instructions for the software in a suitable, non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. 
     In some examples, video encoder  20  and video decoder  30  operate according to a video compression standard, such as ISO/IEC MPEG-4 Visual and ITU-T H.264 (also known as ISO/IEC MPEG-4 AVC), including its Scalable Video Coding (SVC) extension, Multi-view Video Coding (MVC) extension, and MVC-based three-dimensional video (3DV) extension. In some instances, any bitstream conforming to MVC-based 3DV always contains a sub-bitstream that is compliant to a MVC profile, e.g., stereo high profile. Furthermore, there is an ongoing effort to generate a 3DV coding extension to H.264/AVC, namely AVC-based 3DV. Other examples of video coding standards include ITU-T H.261, ISO/IEC MPEG-1 Visual, ITU-T H.262 or ISO/IEC MPEG-2 Visual, ITU-T H.263, ISO/IEC MPEG-4 Visual, and ITU-T H.264, ISO/IEC Visual. In other examples, video encoder  20  and video decoder  30  may be configured to operate according to the HEVC standard. 
     Video postprocessor  31  may be configured to send bitstream  34  to sink device  32  and processor  33 . Processor  33  may process data within bitstream  34  and output a graphical picture or video on a display device. Bitstream  34  may include video data, as well as CRI SEI messages  35 . CRI SEI messages  35  may be SEI messages with the specific purpose of providing remapping parameters for the video data to map the video data from one color space to another. In accordance with the techniques described herein CRI SEI messages  35  may also each contain a set of one or more display capabilities that correspond to the remapping parameters, where the remapping parameters in a particular one of CRI SEI messages  35  are compatible remapping parameters with the corresponding display capabilities. 
     As will be explained in more detail below, video postprocessor  31  and processor  33  may be configured to implement the techniques of this disclosure. In some examples, video postprocessor  31  may determine, for a first set of one or more display capabilities, a first set of one or more remapping parameters. Video postprocessor  31  may then code, in a first supplemental enhancement information (SEI) message, the first set of one or more display capabilities and the first set of one or more remapping parameters. Video postprocessor  31  may also determine, for a second set of one or more display capabilities, a second set of one or more remapping parameters for the video data, and code, in a second SEI message, the second set of one or more display capabilities and the second set of one or more remapping parameters. Video postprocessor  31  may then send, to sink device  32  in bitstream  34 , the first SEI message, the second SEI message, and the video data. 
     Processor  33  may receive, in bitstream  34  and from video postprocessor  31 , the video data and the first and second SEI messages. For each of the SEI messages, processor  33  may compare the respective set of one or more display capabilities indicated in the respective SEI message with a target set of one or more display capabilities for sink device  32  to determine a compatibility of the respective set of one or more display capabilities with the target set of one or more display capabilities. Responsive to determining that a first set of one or more display capabilities indicated by a first SEI message of the group of one or more SEI messages is compatible with the target set of one or more display capabilities for the sink device, processor  33  may adapt the video data using a respective set of one or more remapping parameters indicated by the first SEI message. 
     In examples where the group of one or more SEI messages comprise only a single SEI message, processor  33  may determine whether the set of one or more display capabilities in the single SEI message are compatible with the target set of one or more display capabilities. If the set of one or more display capabilities in the single SEI message are compatible with the target set of one or more display capabilities, processor  33  may adapt the video data using the remapping information in the single SEI message. Conversely, if the set of one or more display capabilities in the single SEI message are not compatible with the target set of one or more display capabilities, processor  33  may either refrain from adapting the video data or adjust the remapping information such that the video data may be displayed in accordance with the target display parameters. 
     In examples where the group of one or more SEI messages comprises a plurality of SEI messages, processor  33  may analyze each set of one or more display capabilities in the respective SEI messages and select an SEI message that is compatible with the target set of one or more display capabilities. Processor  33  may then adapt the video data using a respective set of one or more remapping parameters indicated by the selected SEI message. 
     Video preprocessor  19 , video postprocessor  31 , and processor  33  each may be implemented as any of a variety of suitable encoder circuitry, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware or any combinations thereof. When the techniques are implemented partially in software, a device may store instructions for the software in a suitable, non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. As discussed above video preprocessor  19  and video postprocessor  31  may be separate devices from video encoder  20  and video decoder  30 , respectively. In other examples, video preprocessor  19  may integrated with video encoder  20  in a single device and video postprocessor  31  may be integrated with video decoder  30  in a single device. 
     In HEVC and other video coding standards, a video sequence typically includes a series of pictures. Pictures may also be referred to as “frames.” A picture may include three sample arrays, denoted S L , S Cb , and S Cr . S L  is a two-dimensional array (i.e., a block) of luma samples. S Cb  is a two-dimensional array of Cb chrominance samples. S Cr  is a two-dimensional array of Cr chrominance samples. Chrominance samples may also be referred to herein as “chroma” samples. In other instances, a picture may be monochrome and may only include an array of luma samples. 
     Video encoder  20  may generate a set of coding tree units (CTUs). Each of the CTUs may comprise a coding tree block of luma samples, two corresponding coding tree blocks of chroma samples, and syntax structures used to code the samples of the coding tree blocks. In a monochrome picture or a picture that has three separate color planes, a CTU may comprise a single coding tree block and syntax structures used to code the samples of the coding tree block. A coding tree block may be an N×N block of samples. A CTU may also be referred to as a “tree block” or a “largest coding unit” (LCU). The CTUs of HEVC may be broadly analogous to the macroblocks of other video coding standards, such as H.264/AVC. However, a CTU is not necessarily limited to a particular size and may include one or more coding units (CUs). A slice may include an integer number of CTUs ordered consecutively in the raster scan. 
     This disclosure may use the term “video unit” or “video block” to refer to one or more blocks of samples and syntax structures used to code samples of the one or more blocks of samples. Example types of video units may include CTUs, CUs, PUs, transform units (TUs) in HEVC, or macroblocks, macroblock partitions, and so on in other video coding standards. 
     To generate a coded CTU, video encoder  20  may recursively perform quad-tree partitioning on the coding tree blocks of a CTU to divide the coding tree blocks into coding blocks, hence the name “coding tree units.” A coding block is an N×N block of samples. A CU may comprise a coding block of luma samples and two corresponding coding blocks of chroma samples of a picture that has a luma sample array, a Cb sample array and a Cr sample array, and syntax structures used to code the samples of the coding blocks. In a monochrome picture or a picture that has three separate color planes, a CU may comprise a single coding block and syntax structures used to code the samples of the coding block. 
     Video encoder  20  may partition a coding block of a CU into one or more prediction blocks. A prediction block may be a rectangular (i.e., square or non-square) block of samples on which the same prediction is applied. A prediction unit (PU) of a CU may comprise a prediction block of luma samples, two corresponding prediction blocks of chroma samples of a picture, and syntax structures used to predict the prediction block samples. In a monochrome picture or a picture that have three separate color planes, a PU may comprise a single prediction block and syntax structures used to predict the prediction block samples. Video encoder  20  may generate predictive luma, Cb and Cr blocks for luma, Cb and Cr prediction blocks of each PU of the CU. 
     Video encoder  20  may use intra prediction or inter prediction to generate the predictive blocks for a PU. If video encoder  20  uses intra prediction to generate the predictive blocks of a PU, video encoder  20  may generate the predictive blocks of the PU based on decoded samples of the picture associated with the PU. 
     If video encoder  20  uses inter prediction to generate the predictive blocks of a PU, video encoder  20  may generate the predictive blocks of the PU based on decoded samples of one or more pictures other than the picture associated with the PU. Inter prediction may be uni-directional inter prediction (i.e., uni-prediction) or bi-directional inter prediction (i.e., bi-prediction). To perform uni-prediction or bi-prediction, video encoder  20  may generate a first reference picture list (RefPicList0) and a second reference picture list (RefPicList1) for a current slice. 
     Each of the reference picture lists may include one or more reference pictures. When using uni-prediction, video encoder  20  may search the reference pictures in either or both RefPicList0 and RefPicList1 to determine a reference location within a reference picture. Furthermore, when using uni-prediction, video encoder  20  may generate, based at least in part on samples corresponding to the reference location, the predictive sample blocks for the PU. Moreover, when using uni-prediction, video encoder  20  may generate a single motion vector that indicates a spatial displacement between a prediction block of the PU and the reference location. To indicate the spatial displacement between a prediction block of the PU and the reference location, a motion vector may include a horizontal component specifying a horizontal displacement between the prediction block of the PU and the reference location and may include a vertical component specifying a vertical displacement between the prediction block of the PU and the reference location. 
     When using bi-prediction to encode a PU, video encoder  20  may determine a first reference location in a reference picture in RefPicList0 and a second reference location in a reference picture in RefPicList1. Video encoder  20  may then generate, based at least in part on samples corresponding to the first and second reference locations, the predictive blocks for the PU. Moreover, when using bi-prediction to encode the PU, video encoder  20  may generate a first motion indicating a spatial displacement between a sample block of the PU and the first reference location and a second motion indicating a spatial displacement between the prediction block of the PU and the second reference location. 
     After video encoder  20  generates predictive luma, Cb, and Cr blocks for one or more PUs of a CU, video encoder  20  may generate a luma residual block for the CU. Each sample in the CU&#39;s luma residual block indicates a difference between a luma sample in one of the CU&#39;s predictive luma blocks and a corresponding sample in the CU&#39;s original luma coding block. In addition, video encoder  20  may generate a Cb residual block for the CU. Each sample in the CU&#39;s Cb residual block may indicate a difference between a Cb sample in one of the CU&#39;s predictive Cb blocks and a corresponding sample in the CU&#39;s original Cb coding block. Video encoder  20  may also generate a Cr residual block for the CU. Each sample in the CU&#39;s Cr residual block may indicate a difference between a Cr sample in one of the CU&#39;s predictive Cr blocks and a corresponding sample in the CU&#39;s original Cr coding block. 
     Furthermore, video encoder  20  may use quad-tree partitioning to decompose the luma, Cb and, Cr residual blocks of a CU into one or more luma, Cb, and Cr transform blocks. A transform block may be a rectangular block of samples on which the same transform is applied. A transform unit (TU) of a CU may comprise a transform block of luma samples, two corresponding transform blocks of chroma samples, and syntax structures used to transform the transform block samples. In a monochrome picture or a picture that has three separate color planes, a TU may comprise a single transform block and syntax structures used to transform the transform block samples. Thus, each TU of a CU may be associated with a luma transform block, a Cb transform block, and a Cr transform block. The luma transform block associated with the TU may be a sub-block of the CU&#39;s luma residual block. The Cb transform block may be a sub-block of the CU&#39;s Cb residual block. The Cr transform block may be a sub-block of the CU&#39;s Cr residual block. 
     Video encoder  20  may apply one or more transforms to a luma transform block of a TU to generate a luma coefficient block for the TU. A coefficient block may be a two-dimensional array of transform coefficients. A transform coefficient may be a scalar quantity. Video encoder  20  may apply one or more transforms to a Cb transform block of a TU to generate a Cb coefficient block for the TU. Video encoder  20  may apply one or more transforms to a Cr transform block of a TU to generate a Cr coefficient block for the TU. 
     After generating a coefficient block (e.g., a luma coefficient block, a Cb coefficient block or a Cr coefficient block), video encoder  20  may quantize the coefficient block. Quantization generally refers to a process in which transform coefficients are quantized to possibly reduce the amount of data used to represent the transform coefficients, providing further compression. Furthermore, video encoder  20  may inverse quantize transform coefficients and apply an inverse transform to the transform coefficients in order to reconstruct transform blocks of TUs of CUs of a picture. Video encoder  20  may use the reconstructed transform blocks of TUs of a CU and the predictive blocks of PUs of the CU to reconstruct coding blocks of the CU. By reconstructing the coding blocks of each CU of a picture, video encoder  20  may reconstruct the picture. Video encoder  20  may store reconstructed pictures in a decoded picture buffer (DPB). Video encoder  20  may use reconstructed pictures in the DPB for inter prediction and intra prediction. 
     After video encoder  20  quantizes a coefficient block, video encoder  20  may entropy encode syntax elements that indicate the quantized transform coefficients. For example, video encoder  20  may perform Context-Adaptive Binary Arithmetic Coding (CABAC) on the syntax elements indicating the quantized transform coefficients. Video encoder  20  may output the entropy-encoded syntax elements in a bitstream. 
     Video encoder  20  may output a bitstream that includes a sequence of bits that forms a representation of coded pictures and associated data. The bitstream may comprise a sequence of network abstraction layer (NAL) units. Each of the NAL units includes a NAL unit header and encapsulates a raw byte sequence payload (RBSP). The NAL unit header may include a syntax element that indicates a NAL unit type code. The NAL unit type code specified by the NAL unit header of a NAL unit indicates the type of the NAL unit. A RBSP may be a syntax structure containing an integer number of bytes that is encapsulated within a NAL unit. In some instances, an RBSP includes zero bits. 
     Different types of NAL units may encapsulate different types of RBSPs. For example, a first type of NAL unit may encapsulate a RBSP for a picture parameter set (PPS), a second type of NAL unit may encapsulate a RBSP for a coded slice, a third type of NAL unit may encapsulate a RBSP for Supplemental Enhancement Information (SEI), and so on. A PPS is a syntax structure that may contain syntax elements that apply to zero or more entire coded pictures. NAL units that encapsulate RBSPs for video coding data (as opposed to RBSPs for parameter sets and SEI messages) may be referred to as video coding layer (VCL) NAL units. A NAL unit that encapsulates a coded slice may be referred to herein as a coded slice NAL unit. A RBSP for a coded slice may include a slice header and slice data. 
     Video decoder  30  may receive a bitstream. In addition, video decoder  30  may parse the bitstream to decode syntax elements from the bitstream. Video decoder  30  may reconstruct the pictures of the video data based at least in part on the syntax elements decoded from the bitstream. The process to reconstruct the video data may be generally reciprocal to the process performed by video encoder  20 . For instance, video decoder  30  may use motion vectors of PUs to determine predictive blocks for the PUs of a current CU. Video decoder  30  may use a motion vector or motion vectors of PUs to generate predictive blocks for the PUs. 
     In addition, video decoder  30  may inverse quantize coefficient blocks associated with TUs of the current CU. Video decoder  30  may perform inverse transforms on the coefficient blocks to reconstruct transform blocks associated with the TUs of the current CU. Video decoder  30  may reconstruct the coding blocks of the current CU by adding the samples of the predictive sample blocks for PUs of the current CU to corresponding samples of the transform blocks of the TUs of the current CU. By reconstructing the coding blocks for each CU of a picture, video decoder  30  may reconstruct the picture. Video decoder  30  may store decoded pictures in a decoded picture buffer for output and/or for use in decoding other pictures. 
     Next generation video applications may operate with video data representing captured scenery with HDR and a WCG. Parameters of the utilized dynamic range and the color gamut are two independent attributes of video content, and their specification for purposes of digital television and multimedia services are defined by several international standards. For example, ITU-R Rec. BT.709, “Parameter values for the HDTV standards for production and international programme exchange,” defines parameters for HDTV (high definition television), such as standard dynamic range (SDR) and standard color gamut, and ITU-R Rec. BT.2020, “Parameter values for ultra-high definition television systems for production and international programme exchange,” specifies ultra-high definition television (UHDTV) parameters such as HDR and WCG. There are also other standards developing organization (SDOs) documents that specify dynamic range and color gamut attributes in other systems, e.g., DCI-P3 color gamut is defined in SMPTE-231-2 (Society of Motion Picture and Television Engineers) and some parameters of HDR are defined in SMPTE-2084. A brief description of dynamic range and color gamut for video data is provided below. 
     Dynamic range is typically defined as the ratio between the minimum and maximum brightness (e.g., luminance) of the video signal. Dynamic range may also be measured in terms of “f-stop,” where one f-stop corresponds to a doubling of a signal&#39;s dynamic range. In MPEG&#39;s definition, HDR content is content that features brightness variation with more than 16 f-stops. In some terms, levels with between 10 and 16 f-stops are considered as intermediate dynamic range, but it is considered HDR in other definitions. In some examples of this disclosure, HDR video content may be any video content that has a higher dynamic range than traditionally used video content with a standard dynamic range (e.g., video content as specified by ITU-R Rec. BT.709). 
     Supplemental Enhancement information (SEI) messages may be included in video bitstreams, typically to carry information that are not essential in order to decode the bitstream by the decoder. This information is useful in improving the display or processing of the decoded output; e.g. such information may be used by decoder-side entities to improve the viewability of the content. 
     It may also be possible that certain application standards (e.g., digital video broadcasting (DVB), advanced television systems committee (ATSC)) mandate the presence of such SEI messages in the bitstream such that the improvement in quality may be brought to all devices that conform to the application standard (the carriage of the frame-packing SEI message for frame-compatible plano-stereoscopic 3DTV video format, where the SEI message is carried for every frame of the video, handling of recovery point SEI message, use of pan-scan scan rectangle SEI message in DVB). 
     The color remapping information (CRI) SEI message defined in the HEVC standard may be used to convey information for mapping pictures in one color space to another. The syntax of the CRI SEI message may include three parts: a first set of three 1-D look-up table (Pre-LUT), followed by a 3×3 matrix, followed by second set of three 1-D look-up tables (Post-LUT). For each color component, e.g. R, G, B or Y, Cb, Cr, independent LUT is defined for both, Pre-LUT and Post-LUT. 
     The CRI SEI message includes syntax element called color_remap_id, different values of which may be used to indicate different purposes of the SEI message.  FIG. 2  shows a typical structure of the color remapping information/process used by the CRI SEI message. 
     The syntax for a CRI SEI message may be similar to the following: 
     
       
         
           
               
               
             
               
                   
               
               
                   
                 Descriptor 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 color_remapping_info( payloadSize ) { 
               
            
           
           
               
               
               
            
               
                   
                 color_remap_id 
                 ue(v) 
               
               
                   
                 color_remap_cancel_flag 
                 u(1) 
               
               
                   
                 if( !color_remap_cancel_flag ) { 
                   
               
            
           
           
               
               
               
            
               
                   
                 color_remap_persistence_flag 
                 u(1) 
               
               
                   
                 color_remap_video_signal_info_present_flag 
                 u(1) 
               
               
                   
                 if( color_remap_video_signal_info_present_flag ) { 
                   
               
            
           
           
               
               
               
            
               
                   
                 color_remap_full_range_flag 
                 u(1) 
               
               
                   
                 color_remap_primaries 
                 u(8) 
               
               
                   
                 color_remap_transfer_function 
                 u(8) 
               
               
                   
                 color_remap_matrix_coefficients 
                 u(8) 
               
            
           
           
               
               
               
            
               
                   
                 } 
                   
               
               
                   
                 color_remap_input_bit_depth 
                 u(8) 
               
               
                   
                 color_remap_bit_depth 
                 u(8) 
               
               
                   
                 for( c = 0; c &lt; 3; c++ ) { 
                   
               
            
           
           
               
               
               
            
               
                   
                 pre_lut_num_val_minus1[ c ] 
                 u(8) 
               
               
                   
                 if( pre_lut_num_val_minus1[ c ] &gt; 0 ) 
                   
               
            
           
           
               
               
            
               
                   
                 for( i = 0; i &lt;= pre_lut_num_val_minus1[ c ]; i++ ) { 
               
            
           
           
               
               
               
            
               
                   
                 pre_lut_coded_value[ c ][ i ] 
                 u(v) 
               
               
                   
                 pre_lut_target_value[ c ][ i ] 
                 u(v) 
               
            
           
           
               
               
            
               
                   
                 } 
               
            
           
           
               
               
               
            
               
                   
                 } 
                   
               
               
                   
                 color_remap_matrix_present_flag 
                 u(1) 
               
               
                   
                 if( color_remap_matrix_present_flag ) { 
                   
               
            
           
           
               
               
               
            
               
                   
                 log2_matrix_denom 
                 u(4) 
               
               
                   
                 for( c = 0; c &lt; 3; c++ ) 
                   
               
            
           
           
               
               
            
               
                   
                 for( i = 0; i &lt; 3; i++ ) 
               
            
           
           
               
               
               
            
               
                   
                 color_remap_coeffs[ c ][ i ] 
                 se(v) 
               
            
           
           
               
               
            
               
                   
                 } 
               
               
                   
                 for( c = 0; c &lt; 3; c++ ) { 
               
            
           
           
               
               
               
            
               
                   
                 post_lut_num_val_minus1[ c ] 
                 u(8) 
               
               
                   
                 if( post_lut_num_val_minus1[ c ] &gt; 0 ) 
                   
               
            
           
           
               
               
            
               
                   
                 for( i = 0; i &lt;= post_lut_num_val_minus1[ c ]; i++ ) { 
               
            
           
           
               
               
               
            
               
                   
                 post_lut_coded_value[ c ][ i ] 
                 u(v) 
               
               
                   
                 post_lut_target_value[ c ][ i ] 
                 u(v) 
               
            
           
           
               
               
            
               
                   
                 } 
               
            
           
           
               
               
            
               
                   
                 } 
               
            
           
           
               
               
            
               
                   
                 } 
               
            
           
           
               
            
               
                 } 
               
               
                   
               
            
           
         
       
     
     Semantics for the variables described above for a CRI SEI message may include the following (Note that complete semantics may be available in the HEVC standard): 
     The color remapping information SEI message provides information to enable remapping of the reconstructed color samples of the output pictures. The video coding device may apply the color remapping information directly to the decoded sample values, regardless of whether they are in the luma and chroma domain or the RGB domain. The color remapping model used in the color remapping information SEI message is composed of a first piece-wise linear function applied to each color component (specified by the “pre” set of syntax elements herein), a three by-three matrix applied to the three color components, and a second piece-wise linear function applied to each color component (specified by the “post” set of syntax elements herein). Color remapping of the output pictures for the display is optional and does not affect the decoding process specified herein. 
     color_remap_id contains an identifying number that the video coding device may use to identify the purpose of the color remapping information. The value of color_remap_id may be in the range of 0 to 232−2, inclusive. 
     Values of color_remap_id from 0 to 255 and from 512 to 231−1 may be used as determined by the application. Values of color_remap_id from 256 to 511, inclusive, and from 231 to 232−2, inclusive are reserved for future use by ITU-T|ISO/IEC. Decoders may ignore all CRI SEI messages containing a value of color_remap_id in the range of 256 to 511, inclusive, or in the range of 231 to 232−2, inclusive, and bitstreams may not contain such values. 
     The video coding device may use the color_remap_id to support different color remapping processes that are suitable for different display scenarios. For example, different values of color_remap_id may correspond to different remapped color spaces supported by displays. 
     color_remap_matrix_coefficients has the same semantics as specified in clause E.3.1 of HEVC for the matrix_coeffs syntax element, except that color_remap_matrix_coefficients specifies the color space of the remapped reconstructed picture, rather than the color space used for the CLVS. When not present, the video coding device infers the value of color_remap_matrix_coefficients to be equal to the value of matrix_coeffs. 
     color_remap_input_bit_depth specifies the bit depth of the luma and chroma components or the RGB components of the associated pictures for purposes of interpretation of the color remapping information SEI message. When any color remapping information SEI messages is present with the value of color_remap_input_bit_depth not equal to the bit depth of the coded luma and chroma components or that of the coded RGB components, the SEI message refers to the hypothetical result of a transcoding operation performed to convert the coded video to a converted video with bit depth equal to color_remap_input_bit_depth. 
     The value of color_remap_input_bit_depth may be in the range of 8 to 16, inclusive. Values of color_remap_input_bit_depth from 0 to 7, inclusive, and from 17 to 255, inclusive, are reserved for future use by ITU-T|ISO/IEC. Decoders may ignore all color remapping SEI messages that contain a color_remap_input_bit_depth in the range of 0 to 7, inclusive, or in the range of 17 to 255, inclusive, and bitstreams may not contain such values. 
     color_remap_bit_depth specifies the bit depth of the output of the color remapping function described by the color remapping information SEI message. 
     The value of color_remap_bit_depth may be in the range of 8 to 16, inclusive. Values of color_remap_bit_depth from 0 to 7, inclusive, and in the range of 17 to 255, inclusive, are reserved for future use by ITU-T|ISO/IEC. Decoders may ignore all color remapping SEI messages that contain a value of color_remap_bit_depth from 0 to 7, inclusive, or in the range of 17 to 255, inclusive. 
     pre_lut_num_val_minus1[c] plus 1 specifies the number of pivot points in the piece-wise linear remapping function for the c-th component, where c equal to 0 refers to the luma or G component, c equal to 1 refers to the Cb or B component, and c equal to 2 refers to the Cr or R component. When pre_lut_num_val_minus1[c] is equal to 0, the default end points of the input values are 0 and 2color_remap_input_bit_depth−1, and the corresponding default end points of the output values are 0 and 2color_remap_bit_depth−1, for the c-th component. In bitstreams conforming to this version of this Specification, the value of pre_lut_num_val_minus1[c] may be in the range of 0 to 32, inclusive. 
     pre_lut_coded_value[c][i] specifies the value of the i-th pivot point for the c-th component. The number of bits used to represent pre_lut_coded_value[c][i] is ((color_remap_input_bit_depth+7)&gt;&gt;3)&lt;&lt;3. 
     pre_lut_target_value[c][i] specifies the value of the i-th pivot point for the c-th component. The number of bits used to represent pre_lut_target_value[c][i] is ((color_remap_bit_depth+7)&gt;&gt;3)&lt;&lt;3. 
     The semantics of post_lut_num_val_minus[ ], post_lut_coded_value[ ][ ], and post_lut_target_value[ ][ ] are similar to the semantics of pre_lut_num_val_minus[ ], pre_lut_coded_value[ ][ ], and pre_lut_target_value[ ][ ], respectively; the number of bits used to represent post_lut_coded_value[ ][ ], and post_lut_target_value[ ][ ] is equal to color_remap_bit_depth. 
     The human visual system (HVS) is capable for perceiving much larger dynamic ranges than SDR content and HDR content. However, the HVS includes an adaptation mechanism to narrow the dynamic range of the HVS to a so-called simultaneous range. The width of the simultaneous range may be dependent on current lighting conditions (e.g., current brightness). Visualization of dynamic range provided by SDR of HDTV, expected HDR of UHDTV and HVS dynamic range is shown in  FIG. 3 . 
     Some example video application and services are regulated by ITU Rec.709 and provide SDR, typically supporting a range of brightness (e.g., luminance) of around 0.1 to 100 candelas (cd) per m2 (often referred to as “nits”), leading to less than 10 f-stops. Some example next generation video services are expected to provide dynamic range of up to 16 f-stops. Although detailed specifications for such content are currently under development, some initial parameters have been specified in SMPTE-2084 and ITU-R Rec. 2020. 
     Another aspect for a more realistic video experience, besides HDR, is the color dimension. Color dimension is typically defined by the color gamut.  FIG. 4  is a conceptual diagram showing an SDR color gamut (triangle  100  based on the BT.709 color primaries), and the wider color gamut that for UHDTV (triangle  102  based on the BT.2020 color primaries).  FIG. 4  also depicts the so-called spectrum locus (delimited by the tongue-shaped area  104 ), representing the limits of the natural colors. As illustrated by  FIG. 4 , moving from BT.709 (triangle  100 ) to BT.2020 (triangle  102 ) color primaries aims to provide UHDTV services with about 70% more colors. D65 specifies an example white color for the BT.709 and/or BT.2020 specifications. 
     Examples of color gamut specifications for the DCI-P3, BT.709, and BT.202 color spaces are shown in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Color gamut parameters 
               
               
                 RGB color space parameters 
               
            
           
           
               
               
               
            
               
                 Color 
                 White point 
                 Primary colors 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 space 
                 xx W   
                 yy W   
                 xx R   
                 yy R   
                 xx G   
                 yy G   
                 xx B   
                 yy B   
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 DCI-P3 
                 0.314 
                 0.351 
                 0.680 
                 0.320 
                 0.265 
                 0.690 
                 0.150 
                 0.060 
               
               
                 ITU-R 
                 0.3127 
                 0.3290 
                 0.64 
                 0.33 
                 0.30 
                 0.60 
                 0.15 
                 0.06 
               
               
                 BT.709 
               
               
                 ITU-R 
                 0.3127 
                 0.3290 
                 0.708 
                 0.292 
                 0.170 
                 0.797 
                 0.131 
                 0.046 
               
               
                 BT.2020 
               
               
                   
               
            
           
         
       
     
     As may be seen in Table 1, a color gamut may be defined by the X and Y values of a white point, and by the X and Y values of the primary colors (e.g., red (R), green (G), and blue (B). The X and Y values represent the chromaticity (X) and the brightness (Y) of the colors, as is defined by the CIE 1931 color space. The CIE 1931 color space defines the links between pure colors (e.g., in terms of wavelengths) and how the human eye perceives such colors. 
     HDR/WCG video data is typically acquired and stored at a very high precision per component (even floating point), with the 4:4:4 chroma sub-sampling format and a very wide color space (e.g., CIE XYZ). This representation targets high precision and is almost mathematically lossless. However, such a format for storing HDR/WCG video data may include a lot of redundancies and may not be optimal for compression purposes. A lower precision format with HVS-based assumptions is typically utilized for state-of-the-art video applications. 
     One example of a video data format conversion process for purposes of compression includes three major processes, as shown in  FIG. 5 . The techniques of  FIG. 5  may be performed by source device  12 . Linear RGB data  110  may be HDR/WCG video data and may be stored in a floating-point representation. Linear RGB data  110  may be compacted using a non-linear transfer function (TF)  112  for dynamic range compacting. Transfer function  112  may compact linear RGB data  110  using any number of non-linear transfer functions, e.g., the PQ TF as defined in SMPTE-2084. In some examples, color conversion process  114  converts the compacted data into a more compact or robust color space (e.g., a YUV or YCbCr color space) that is more suitable for compression by a hybrid video encoder. This data is then quantized using a floating-to-integer representation quantization unit  116  to produce converted HDR′ data  118 . In this example HDR′ data  118  is in an integer representation. The HDR′ data is now in a format more suitable for compression by a hybrid video encoder (e.g., video encoder  20  applying HEVC techniques). The order of the processes depicted in  FIG. 5  is given as an example, and may vary in other applications. For example, color conversion may precede the TF process. In addition, additional processing, e.g. spatial subsampling, may be applied to color components. 
     The inverse conversion at the decoder side is depicted in  FIG. 5 . The techniques of  FIG. 6  may be performed by destination device  14 . Converted HDR′ data  120  may be obtained at destination device  14  through decoding video data using a hybrid video decoder (e.g., video decoder  30  applying HEVC techniques). HDR′ data  120  may then be inverse quantized by inverse quantization unit  122 . Then an inverse color conversion process  124  may be applied to the inverse quantized HDR′ data. The inverse color conversion process  124  may be the inverse of color conversion process  114 . For example, the inverse color conversion process  124  may convert the HDR′ data from a YCbCr format back to an RGB format. Next, inverse transfer function  126  may be applied to the data to add back the dynamic range that was compacted by transfer function  112  to recreate the linear RGB data  128 . 
     The techniques depicted in  FIG. 5  will now be discussed in more detail. In general, a transfer function is applied to data (e.g., HDR/WCG video data) to compact the dynamic range of the data. Such compaction allows the data to be represented with fewer bits. In one example, the transfer function may be a one-dimensional (1D) non-linear function and may reflect the inverse of an electro-optical transfer function (EOTF) of the end-user display, e.g., as specified for SDR in Rec. 709. In another example, the transfer function may approximate the HVS perception to brightness changes, e.g., the PQ transfer function specified in SMPTE-2084 for HDR. The inverse process of the OETF is the EOTF (electro-optical transfer function), which maps the code levels back to luminance.  FIG. 7  shows several examples of non-linear transfer function used to compact the dynamic range of certain color containers. The transfer functions may also be applied to each R, G and B component separately. 
     The reference EOTF specified ITU-R recommendation BT.1886 may be specified by the equation:
 
 L=a (max[( V+b ),0]) γ 
 
where:
         L: Screen luminance in cd/m2   L W : Screen luminance for white   L B : Screen luminance for black   V: Input video signal level (normalized, black at V=0, to white at V=1. For content mastered per Recommendation ITU-R BT.709, 10-bit digital code values “D” map into values of V per the following equation: V=(D−64)/876   γ: Exponent of power function, γ=2.404   a: Variable for user gain (legacy “contrast” control)       

     
       
         
           
             a 
             = 
             
               
                 ( 
                 
                   
                     L 
                     W 
                     
                       1 
                       γ 
                     
                   
                   - 
                   
                     L 
                     B 
                     
                       1 
                       γ 
                     
                   
                 
                 ) 
               
               γ 
             
           
         
       
         
         
           
             b: Variable for user black level lift (legacy “brightness” control) 
           
         
       
    
     
       
         
           
             b 
             = 
             
               
                 L 
                 B 
                 
                   1 
                   / 
                   γ 
                 
               
               
                 
                   L 
                   W 
                   
                     1 
                     / 
                     γ 
                   
                 
                 - 
                 
                   L 
                   B 
                   
                     1 
                     / 
                     γ 
                   
                 
               
             
           
         
       
     
     Above variables a and b are derived by solving following equations in order that V=1 gives 
     L=L W  and that V=0 gives L=L B :
 
 L   B   =a·b   γ 
 
 L   w   =a ·(1+ b ) γ 
 
     In order to support higher dynamic range data more efficiency, SMPTE has recently standardized a new transfer function called SMPTE ST-2084. Specification of ST2084 defined the EOTF application as following. TF is applied to a normalized linear R, G, B values which results in nonlinear representation of R′G′B′. ST2084 defines normalization by NORM=10000, which is associated with a peak brightness of 10000 nits (cd/m2). 
     
       
         
           
             
               R 
               ′ 
             
             = 
             
               PQ_TF 
               ⁢ 
               
                 ( 
                 
                   max 
                   ⁡ 
                   
                     ( 
                     
                       0 
                       , 
                       
                         min 
                         ⁡ 
                         
                           ( 
                           
                             
                               R 
                               / 
                               NORM 
                             
                             , 
                             1 
                           
                           ) 
                         
                       
                     
                     ) 
                   
                 
                 ) 
               
             
           
         
       
       
         
           
             
               G 
               ′ 
             
             = 
             
               PQ_TF 
               ⁢ 
               
                 ( 
                 
                   max 
                   ⁡ 
                   
                     ( 
                     
                       0 
                       , 
                       
                         min 
                         ⁡ 
                         
                           ( 
                           
                             
                               G 
                               / 
                               NORM 
                             
                             , 
                             1 
                           
                           ) 
                         
                       
                     
                     ) 
                   
                 
                 ) 
               
             
           
         
       
       
         
           
             
               B 
               ′ 
             
             = 
             
               PQ_TF 
               ⁢ 
               
                 ( 
                 
                   max 
                   ⁡ 
                   
                     ( 
                     
                       0 
                       , 
                       
                         min 
                         ⁡ 
                         
                           ( 
                           
                             
                               B 
                               / 
                               NORM 
                             
                             , 
                             1 
                           
                           ) 
                         
                       
                     
                     ) 
                   
                 
                 ) 
               
             
           
         
       
       
         
           
             with 
             ⁢ 
             
                 
             
           
         
       
       
         
           
             
               PQ_TF 
               ⁢ 
               
                 ( 
                 L 
                 ) 
               
             
             = 
             
               
                 ( 
                 
                   
                     
                       c 
                       1 
                     
                     + 
                     
                       
                         c 
                         2 
                       
                       ⁢ 
                       
                         L 
                         
                           m 
                           1 
                         
                       
                     
                   
                   
                     1 
                     + 
                     
                       
                         c 
                         3 
                       
                       ⁢ 
                       
                         L 
                         
                           m 
                           1 
                         
                       
                     
                   
                 
                 ) 
               
               
                 m 
                 2 
               
             
           
         
       
       
         
           
             
               m 
               1 
             
             = 
             
               
                 
                   2610 
                   4096 
                 
                 × 
                 
                   1 
                   4 
                 
               
               = 
               0.1593017578125 
             
           
         
       
       
         
           
             
               m 
               2 
             
             = 
             
               
                 
                   2523 
                   4096 
                 
                 × 
                 128 
               
               = 
               78.84375 
             
           
         
       
       
         
           
             
               c 
               1 
             
             = 
             
               
                 
                   c 
                   3 
                 
                 - 
                 
                   c 
                   2 
                 
                 + 
                 1 
               
               = 
               
                 
                   3424 
                   4096 
                 
                 = 
                 0.8359375 
               
             
           
         
       
       
         
           
             
               c 
               2 
             
             = 
             
               
                 
                   2413 
                   4096 
                 
                 × 
                 32 
               
               = 
               18.8515625 
             
           
         
       
       
         
           
             
               c 
               3 
             
             = 
             
               
                 
                   2392 
                   4096 
                 
                 × 
                 32 
               
               = 
               18.6875 
             
           
         
       
     
     Typically, EOTF is defined as a function with a floating-point accuracy, thus no error is introduced to a signal with this non-linearity if inverse TF so called OETF is applied. Inverse TF (OETF) specified in ST2084 is defined as inversePQ function: 
     
       
         
           
             R 
             = 
             
               10000 
               * 
               inversePQ_TF 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 
                   R 
                   ′ 
                 
                 ) 
               
             
           
         
       
       
         
           
             G 
             = 
             
               10000 
               * 
               inversePQ_TF 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 
                   G 
                   ′ 
                 
                 ) 
               
             
           
         
       
       
         
           
             B 
             = 
             
               10000 
               * 
               inversePQ_TF 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 
                   B 
                   ′ 
                 
                 ) 
               
             
           
         
       
       
         
           
             with 
             ⁢ 
             
                 
             
           
         
       
       
         
           
             
               inversePQ_TF 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 N 
                 ) 
               
             
             = 
             
               
                 ( 
                 
                   
                     max 
                     ⁡ 
                     
                       [ 
                       
                         
                           ( 
                           
                             
                               N 
                               
                                 1 
                                 / 
                                 
                                   m 
                                   2 
                                 
                               
                             
                             - 
                             
                               c 
                               1 
                             
                           
                           ) 
                         
                         , 
                         0 
                       
                       ] 
                     
                   
                   
                     
                       c 
                       2 
                     
                     - 
                     
                       
                         c 
                         3 
                       
                       ⁢ 
                       
                         N 
                         
                           1 
                           / 
                           
                             m 
                             2 
                           
                         
                       
                     
                   
                 
                 ) 
               
               
                 1 
                 / 
                 
                   m 
                   1 
                 
               
             
           
         
       
       
         
           
             
               m 
               1 
             
             = 
             
               
                 
                   2610 
                   4096 
                 
                 × 
                 
                   1 
                   4 
                 
               
               = 
               
                 
                   0.1593017578125 
                   ⁢ 
                   
                     
 
                   
                   ⁢ 
                   
                     m 
                     2 
                   
                 
                 = 
                 
                   
                     
                       2523 
                       4096 
                     
                     × 
                     128 
                   
                   = 
                   
                     
                       78.84375 
                       ⁢ 
                       
                         
 
                       
                       ⁢ 
                       
                         c 
                         1 
                       
                     
                     = 
                     
                       
                         
                           c 
                           3 
                         
                         - 
                         
                           c 
                           2 
                         
                         + 
                         1 
                       
                       = 
                       
                         
                           3424 
                           4096 
                         
                         = 
                         
                           
                             0.8359375 
                             ⁢ 
                             
                               
 
                             
                             ⁢ 
                             
                               c 
                               2 
                             
                           
                           = 
                           
                             
                               
                                 2413 
                                 4096 
                               
                               × 
                               32 
                             
                             = 
                             
                               
                                 18.8515625 
                                 ⁢ 
                                 
                                   
 
                                 
                                 ⁢ 
                                 
                                   c 
                                   3 
                                 
                               
                               = 
                               
                                 
                                   
                                     2392 
                                     4096 
                                   
                                   × 
                                   32 
                                 
                                 = 
                                 18.6875 
                               
                             
                           
                         
                       
                     
                   
                 
               
             
           
         
       
     
     Note that EOTF and OETF are subjects of active research and standardization, and TFs utilized in some video coding systems may be different from ST2084. 
     In the context of this disclosure, the terms “signal value” or “color value” may be used to describe a luminance level corresponding to the value of a specific color component (such as R, G, B, or Y) for an image element. The signal value is typically representative of a linear light level (luminance value). The terms “code level” or “digital code value” may refer to a digital representation of an image signal value. Typically, such a digital representation is representative of a nonlinear signal value. An EOTF represents the relationship between the nonlinear signal values provided to a display device (e.g., sink device  32 ) and the linear color values produced by the display device. 
     RGB data is typically utilized as the input color space, since RGB is the type of data that is typically produced by image capturing sensors. However, the RGB color space has high redundancy among its components and is not optimal for compact representation. To achieve more compact and a more robust representation, RGB components are typically converted (e.g., a color transform is performed) to a more uncorrelated color space that is more suitable for compression, e.g., YCbCr. A YCbCr color space separates the brightness in the form of luminance (Y) and color information (CrCb) in different less correlated components. In this context, a robust representation may refer to a color space featuring higher levels of error resilience when compressed at a constrained bitrate. 
     Following the color transform, input data in a target color space may be still represented at high bit-depth (e.g. floating-point accuracy). The high bit-depth data may be converted to a target bit-depth, for example, using a quantization process. Certain studies show that 10-12 bits accuracy in combination with the PQ transfer is sufficient to provide HDR data of 16 f-stops with distortion below the Just-Noticeable Difference (JND). In general, a JND is the amount something (e.g., video data) must be change in order for a difference to be noticeable (e.g., by the HVS). Data represented with 10 bits accuracy can be further coded with most of the state-of-the-art video coding solutions. This quantization is an element of lossy coding and is a source of inaccuracy introduced to converted data. 
     Next generation HDR/WCG video applications may operate with video data captured at different parameters of HDR and CG. Examples of different configuration can be the capture of HDR video content with peak brightness up-to 1000 nits, or up-to 10,000 nits. Examples of different color gamut may include BT.709, BT.2020 as well SMPTE specified-P3, or others. 
     A single color space, e.g., a target color container, that incorporates all other currently used color gamut may be utilized. One example of such a target color container is BT.2020. Support of a single target color container may simplify standardization, implementation and deployment of HDR/WCG systems, since a reduced number of operational points (e.g., number of color containers, color spaces, color conversion algorithms, etc.) and/or a reduced number of required algorithms should be supported by a decoder (e.g., video decoder  30 ). 
     In one example of such a system, content captured with a native color gamut (e.g. P3 or BT.709) different from the target color container (e.g. BT.2020) may be converted to the target container prior to processing (e.g., prior to video encoding). Below are several examples of such conversion: 
     RGB conversion from BT.709 to BT.2020 color container:
 
 R   2020 =0.627404078626* R   709 +0.329282097415* G   709 +0.043313797587* B   709  
 
 G   2020 =0.069097233123* R   709 +0.919541035593* G   709 +0.011361189924* B   709  
 
 B   2020 =0.016391587664* R   709 +0.088013255546* G   709 +0.895595009604* B   709  
 
     RGB conversion from P3 to BT.2020 color container:
 
 R   2020 =0.753832826496* R   P3 +0.198597635641* G   P3 +0.047569409186* B   P3  
 
 G   2020 =0.045744636411* R   P3 +0.941777687331* G   P3 +0.012478735611* B   P3  
 
 B   2020 =−0.001210377285* R   P3 +0.017601107390* G   P3 +0.983608137835* B   P3  
 
     For modern video coding systems, typically used color space is YCbCr, as specified in ITU-R BT.709. The YCbCr color space in BT.709 standard specifies the following conversion process from R′G′B′ to Y′CbCr (non-constant luminance representation):
 
 Y′= 0.2126* R′+ 0.7152* G′+ 0.0722* B′ 
 
 Cb =( B^′−Y ^′)/1.8556
 
 Cr =( R^′−Y ^′)/1.5748
 
     The above can also be implemented using the following approximate conversion that avoids the division for the Cb and Cr components:
 
 Y′= 0.212600* R′+ 0.715200* G′+ 0.072200* B′ 
 
 Cb=− 0.114572* R′− 0.385428* G′+ 0.500000* B′ 
 
 Cr= 0.500000* R′− 0.454153* G′− 0.045847* B′ 
 
     During this conversion, the dynamic range of a signal captured in P3 or BT.709 color gamut may be reduced in a BT.2020 representation. Since the data is represented in floating point accuracy, there is no loss; however, when combined with color conversion (e.g., a conversion from RGB to YCbCr shown in equation 3 below) and quantization (example in equation 4 below), dynamic range reduction leads to increased quantization error for input data. 
     
       
         
           
             
               
                 Y 
                 ′ 
               
               = 
               
                 
                   0.2627 
                   * 
                   
                     R 
                     ′ 
                   
                 
                 + 
                 
                   0.6780 
                   * 
                   
                     G 
                     ′ 
                   
                 
                 + 
                 
                   0.0593 
                   * 
                   
                     B 
                     ′ 
                   
                 
               
             
             ; 
           
         
       
       
         
           
             
               Cb 
               = 
               
                 
                   
                     B 
                     ′ 
                   
                   - 
                   
                     Y 
                     ′ 
                   
                 
                 1.8814 
               
             
             ; 
           
         
       
       
         
           
             Cr 
             = 
             
               
                 
                   R 
                   ′ 
                 
                 - 
                 
                   Y 
                   ′ 
                 
               
               1.4746 
             
           
         
       
       
         
           
             
               D 
               
                 Y 
                 ′ 
               
             
             = 
             
               ( 
               
                 Round 
                 ⁡ 
                 
                   ( 
                   
                     
                       ( 
                       
                         
                           1 
                           - 
                         
                         ⪡ 
                         
                           ( 
                           
                             
                               BitDepth 
                               Y 
                             
                             - 
                             8 
                           
                           ) 
                         
                       
                       ) 
                     
                     * 
                     
                       ( 
                       
                         
                           219 
                           * 
                           
                             Y 
                             ′ 
                           
                         
                         + 
                         16 
                       
                       ) 
                     
                   
                   ) 
                 
               
               ) 
             
           
         
       
       
         
           
             
               D 
               Cb 
             
             = 
             
               ( 
               
                 Round 
                 ⁡ 
                 
                   ( 
                   
                     
                       ( 
                       
                         
                           1 
                           - 
                         
                         ⪡ 
                         
                           ( 
                           
                             
                               BitDepth 
                               Cr 
                             
                             - 
                             8 
                           
                           ) 
                         
                       
                       ) 
                     
                     * 
                     
                       ( 
                       
                         
                           224 
                           * 
                           Cb 
                         
                         + 
                         128 
                       
                       ) 
                     
                   
                   ) 
                 
               
               ) 
             
           
         
       
       
         
           
             
               D 
               Cr 
             
             = 
             
               ( 
               
                 Round 
                 ⁡ 
                 
                   ( 
                   
                     
                       ( 
                       
                         
                           1 
                           - 
                         
                         ⪡ 
                         
                           ( 
                           
                             
                               BitDepth 
                               Cb 
                             
                             - 
                             8 
                           
                           ) 
                         
                       
                       ) 
                     
                     * 
                     
                       ( 
                       
                         
                           224 
                           * 
                           Cr 
                         
                         + 
                         128 
                       
                       ) 
                     
                   
                   ) 
                 
               
               ) 
             
           
         
       
       
         
           with 
         
       
       
         
           
             
               Round 
               ⁡ 
               
                 ( 
                 x 
                 ) 
               
             
             = 
             
               
                 Sign 
                 ⁡ 
                 
                   ( 
                   x 
                   ) 
                 
               
               * 
               Floor 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 
                   
                     Abs 
                     ⁡ 
                     
                       ( 
                       x 
                       ) 
                     
                   
                   + 
                   0.5 
                 
                 ) 
               
             
           
         
       
       
         
           
             
               
                 
                   S 
                   ⁢ 
                   ign 
                 
                 ⁡ 
                 
                   ( 
                   x 
                   ) 
                 
               
               = 
               
                 
                   
                     - 
                     1 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   if 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   x 
                 
                 &lt; 
                 0 
               
             
             , 
             
               
                 0 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 if 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 x 
               
               = 
               0 
             
             , 
             
               
                 1 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 if 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 x 
               
               &gt; 
               0 
             
           
         
       
       
         
           
             Floor 
             ⁢ 
             
                 
             
             ⁢ 
             
               ( 
               x 
               ) 
             
             ⁢ 
             
                 
             
             ⁢ 
             the 
             ⁢ 
             
                 
             
             ⁢ 
             largest 
             ⁢ 
             
                 
             
             ⁢ 
             integer 
             ⁢ 
             
                 
             
             ⁢ 
             less 
             ⁢ 
             
                 
             
             ⁢ 
             than 
             ⁢ 
             
                 
             
             ⁢ 
             or 
             ⁢ 
             
                 
             
             ⁢ 
             equal 
             ⁢ 
             
                 
             
             ⁢ 
             to 
             ⁢ 
             
                 
             
             ⁢ 
             x 
           
         
       
       
         
           
             
               
                 Abs 
                 ⁡ 
                 
                   ( 
                   x 
                   ) 
                 
               
               = 
               
                 
                   x 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   if 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   x 
                 
                 &gt;= 
                 0 
               
             
             , 
             
               
                 
                   
                     - 
                     x 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   if 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   x 
                 
                 &lt; 
                 
                   0 
                   ⁢ 
                   
                     
 
                   
                   ⁢ 
                   Clip 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     1 
                     Y 
                   
                   ⁢ 
                   
                     ( 
                     x 
                     ) 
                   
                 
               
               = 
               
                 Clip 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 3 
                 ⁢ 
                 
                   ( 
                   
                     0 
                     , 
                     
                       
                         ( 
                         
                           1 
                           ⁢ 
                           
                             &lt;&lt; 
                             
                               BitDepth 
                               Y 
                             
                           
                         
                         ) 
                       
                       - 
                       1 
                     
                     , 
                     x 
                   
                   ) 
                 
               
             
           
         
       
       
         
           
             
               Clip 
               ⁢ 
               
                   
               
               ⁢ 
               
                 1 
                 C 
               
               ⁢ 
               
                 ( 
                 x 
                 ) 
               
             
             = 
             
               Clip 
               ⁢ 
               
                   
               
               ⁢ 
               3 
               ⁢ 
               
                 ( 
                 
                   0 
                   , 
                   
                     
                       ( 
                       
                         1 
                         ⁢ 
                         
                           &lt;&lt; 
                           
                             BitDepth 
                             C 
                           
                         
                       
                       ) 
                     
                     - 
                     1 
                   
                   , 
                   x 
                 
                 ) 
               
             
           
         
       
       
         
           
             
               
                 Clip 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 3 
                 ⁢ 
                 
                   ( 
                   
                     x 
                     , 
                     y 
                     , 
                     z 
                   
                   ) 
                 
               
               = 
               
                 
                   x 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   if 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   z 
                 
                 &lt; 
                 x 
               
             
             , 
             
               
                 y 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 if 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 z 
               
               &gt; 
               y 
             
             , 
             
               z 
               ⁢ 
               
                   
               
               ⁢ 
               otherwise 
             
           
         
       
     
     In the above equations, equation D Y′  is the quantized Y′ component, D Cb  is the quantized Cb and D Cr  is the quantized Cr component. The term &lt;&lt; represents a bit-wise right shift. BitDepth Y , BitDepth Cr , and BitDepth Cb  are the desired bit depths of the quantized components, respectively. 
     The above can also be implemented using the following approximate conversion that avoids the division for the Cb and Cr components:
 
 Y′= 0.262700* R′+ 0.678000* G′+ 0.059300* B′ 
 
 Cb=− 0.139630* R′− 0.360370* G′+ 0.500000* B′ 
 
 Cr= 0.500000* R′− 0.459786* G′− 0.040214* B′ 
 
     In addition, in a real-world coding system, coding a signal with reduced dynamic range may lead to significant loss of accuracy for coded chroma components and would be observed by a viewer as coding artifacts, e.g., color mismatch and/or color bleeding. 
     An uncompressed video signal is signaled through a high-speed digital physical interface from a decoder (e.g., a source device, such as client device  14 ) to an end consumer device (e.g., sink device  32 ), such as a display or TV. Protocols, requirements, and recommendations for the utilization of uncompressed digital interfaces by consumer electronics devices such as Digital Televisions (DTVs), digital cable, satellite or terrestrial set-top boxes (STBs), and related peripheral devices including, but not limited to DVD players/recorders, and other related Sources or Sinks are defined in specification produced by Consumer Electronics Association (CTA) R4.8 DTV Interface Subcommittee, CTA-861. Protocols, requirements, and recommendations that are defined include Video Formats and waveforms; colorimetry and quantization; transport of compressed and uncompressed, as well as Linear Pulse Code Modulation (L-PCM), audio; carriage of auxiliary data; and implementations of the Video Electronics Standards Association (VESA) Enhanced Extended Display Identification Data Standard (E-EDID), which is used by Sinks to declare display capabilities and characteristics. 
     The CTA 861-G specification may include the Extended InfoFrame data structure for the purpose of carrying larger amounts of dynamic (temporally varying) metadata, which can be used for smart processing, guided mapping, display adaptation and color volume transformation applicable at the end device, such as display or TV with information provided from the video signal source, such as decoder or receiver. Type of the Extended InfoFrame application is identified with 2-byte number. When the Extended InfoFrame Type Code is set to 0x0001, 0x0002, 0x0003, or 0x0004, the Extended InfoFrame would carry HDR Dynamic Metadata. The HDR Dynamic Metadata Extended InfoFrame contains the HDR Dynamic Metadata that may be carried in Supplementary Enhancement Information (SEI) messages of the compressed video bitstream, such as HEVC, AVC or VP8/VP9/VP10 bitstreams, or others. 
     If the source device (e.g., client device  14 ) supports transmission of a type of HDR Dynamic Metadata Extended InfoFrame (as indicated by the relevant Extended InfoFrame Type) and if the source device determines that the sink device (e.g., sink device  32 ) is capable of receiving that information, the source device may send the HDR Dynamic Metadata Extended InfoFrame in conjunction with the video encoded according to the rules of the HDR metadata type. A source device shall not send an HDR Dynamic Metadata Extended InfoFrame containing an Extended InfoFrame Type 0x0001, 0x0002, 0x0003, or 0x004 to a sink device that does not indicate support for that Extended InfoFrame Type in the sink device&#39;s HDR Dynamic Metadata Data Block. 
     The communication between the sink device and the source device is conducted via Extended Display Identification Data (EDID). This data, which is stored in the sink device, describes Video Formats that the DTV (display) is capable of receiving and rendering. The information is supplied to the source device, over the interface, upon the request of the source device. The source device then chooses its output format, taking into account the format of the original video stream and the formats supported by the sink device. 
     Parameters of display capabilities are communicated between Sink and Source in several specified data blocks, e.g. Colorimetry Data Block, HDR Static Metadata Block, HDR Dynamic Metadata Data Block and others. 
     The Colorimetry Data Block indicates support of specific extended colorimetry standards and gamut-related as yet, such as BT.2020 or DCI-P3. The HDR Data Block indicates the HDR capabilities of the Sink through such parameters as characteristics of display&#39;s EOTF (BT.1886, ST 2084 or others), desired parameters of dynamical range of the content, e.g. desired content Min/Max Luminance or desired content max frame-average luminance for optimal rendering of content on the display. The HDR Dynamic Metadata Data Block indicates a type and version of the supported HDR Dynamic Metadata Type. 
     Display capabilities described in Colorimetry Data Block (CDB) and HDR Static Metadata Data Block indicate certain parameters of HDR/WCG capabilities of the sink device. Accepted colorimetry, a.k.a. representation format or color container, e.g. BT.2020 or DCI-P3 are specified in the CDB. Whereas display HDR capabilities in a form of desired Min/Max content luminance are defined in HDR Static Metadata Data Block. 
     The information that is relayed through the above blocks allow the source device to convert the decoded uncompressed signal into a format that is understandable by the sink device. The conversion process may include either HDR tone mapping (to meet desired max luminance level) and/or color container conversion (to meet supported colorimetry format) of the content, or selection of HDR Dynamic Metadata Type and parameters entity, which would allow the sink device to conduct signal adaptation to meet its capabilities. 
     Problems may exist with CRI SEI messages. The processes of analyzing the CRI SEI message, such as utilizing the look-up table, may be applied after dequantization, filtering and upsampling the decoded samples, or performing color space conversion of the decoded samples. As defined in HEVC, video decoder  30  may not be aware at what point of the processing chain the CRI SEI is to be applied. 
     The specification of the CRI SEI message includes the syntax element color_remap_id to indicate the purpose of the SEI message. However, the semantics do not specify the processing of concurrent or sequential CRI SEI messages with different IDs, and whether such concurrency or sequence CRI SEI messages may be carried and/or applied. 
     Processor  33  may apply CRI SEI messages  35  to adapt the output of the decoder to a specific display. That is, CRI SEI may be used for display adaptation to a target display. A display may be defined by its peak brightness and color gamut, among other characteristics. However, the CRI SEI does not indicate some of these characteristics of the target display, notably, the peak brightness. The CRI SEI indicates the container of the output (i.e., the meaning of the pixel values), but not the intended use of that output, and specifically, for what kind of display is the output. 
     The CRI SEI message may also be used to specify color volume transformations such that the video after application of the CRI SEI message is suitable for display in a device that has particular characteristics, e.g. a certain color gamut, peak brightness or color volume. Current signaling inside the CRI SEI message may only contain syntax elements that indicates the color primaries of the video after application of the processing specified in CRI SEI. The color primaries only describe how the video data content is to be interpreted, and does not describe the characteristics of the content or how suitable the content is to be represented in a display of certain characteristic. The invention decouples the signaling of the color primaries of the container from the primaries of the content or display. Additionally, the invention allows to describe the target display characteristics (such as target display characteristics, peak luminance etc.) for which the current CRI SEI message is intended, so that a specific display may choose the CRI SEI message that is closest to its own characteristics when there are more than one CRI SEI messages are present. 
     The techniques of this disclosure describe methods for video postprocessor  31  and/or processor  33  to generate and use the CRI SEI message signaling for display adaptation. Application standards like DVB and ATSC may modify or further specify aspects of the SEI in order to make these SEI more useful for their use case. This invention looks at methods to use the CRI SEI message signaling from the point of view of these application standards. 
     Video postprocessor  31  and/or processor  33  may use one or more bits of color_remap_id (codewords in the color_remap_id space) to indicate the color primaries or the color gamut of target displays with which the CRI SEI message is to be associated. Video postprocessor  31  and/or processor  33  may also use such bits to indicate target displays for which usage of the CRI SEI message is suitable for processing the content. 
     In some embodiments, video postprocessor  31  and/or processor  33  may use one or more bits of the color_remap_id to indicate the color primaries or the color gamut of target displays with which the CRI SEI message is associated, or target displays for which usage of the CRI SEI message is suitable for processing the content. Video postprocessor  31  and/or processor  33  may also determine a subset of SEI messages (e.g. subset of a set of signaled CRI SEI messages) based on the bits of color_remap_id, or a representation derived from color_remap_id, such that the values of color_remap_id (or its representation), or the bits thereof, indicate that the processing specified in the CRI messages in the subset are suitable for a particular target display. 
     Suitability of a CRI SEI message to a target display may be defined as the similarity (or matching) of one or more characteristics of the display of sink device  32  with the characteristics described by the syntax elements of the CRI SEI message, including the color_remap_id. For instance, a display color gamut/volume of the display may be close to the color gamut indicated by the color_remap_id, and the transfer function of the display may be the same as the transfer function indicated by color_remap_transfer_function. This may indicate that the CRI message is compatible with the target display. 
     Video postprocessor  31  and/or processor  33  may generate the color_remap_id syntax element for decoder-side interpretation such that one or more bits of color_remap_id indicate the color primaries or the color gamut of the target display and some of other bits of color_remap_id are utilized to identify the difference in other parameters of the CRI message, e.g. transfer characteristics or parameters of color transform. Video postprocessor  31  and/or processor  33  may also generate the color_remap_id syntax element such that one or more bits of color_remap_id indicate the color primaries or the color gamut of the target display and some of other bits of color_remap_id are utilized to identify the sequence of applications of different CRI messages, e.g. an SEI message with a lower value of the color_remap_id may be applied to the decoded samples prior to the CRI message with a higher value of the color_remap_id. 
     Video postprocessor  31  and/or processor  33  may tabulate parameters of the target display color gamut and associate one or more bits of color_remap_id and the parameters of the target color gamut. Parameters of the target color gamut may be expressed, for example, in the form of primaries in x, y, z color space. 
     The semantics of color_remap_id may be changed so that this syntax element also conveys the information that the message is applied either directly to the decoded samples or to samples after some processing. 
     In an example of such a technique, when the color_remap_id is equal to 0, video postprocessor  31  and/or processor  33  may apply the decoder samples in the YCbCr domain. When the color_remap_id is equal to 1, video postprocessor  31  and/or processor  33  may apply the decoded samples after the color transform from YCbCr to RGB. 
     In another example, video postprocessor  31  and/or processor  33  may derive an input to the CRI SEI message from the color_remap_id value. For example, video postprocessor  31  may determine input color coefficients from the color_remap_id syntax element value. For instance, when color_remap_id is even, the input is in YCbCr, and when color_remap_id is odd, the input is in GBR. Note that, in this embodiment, the bit  0  (least significant bit) of color_remap_id may be used to indicate the input domain of the CRI. 
     In one example, color_remap_id value is the value in nits (cd/m2) of the peak luminance of the target display. Valid values of color_remap_id may be constrained to be between 50 and 10000. In another example, the color_remap_id value indicates the peak luminance in steps of 100 nits and be constrained between 1 and 100. 
     In another example, video postprocessor  31  may determine the target maximum luminance (Tml) after remapping (in cd/m2) using the color_remap_id syntax element as follows:
 
 Tml= 100*ceil((color_remap_ id+ 1)/2)
 
A maximum value of Tml may be defined, so not to allow for target maximum luminance above what is reasonable in a display or what is the transfer function able to indicate.
 
     The signaling of the CRI SEI message may mandate the persistence of the CRI SEI for a target display, so that the receiver (e.g., sink device  32  and processor  33 ) may rely on the metadata for display adaptation for the bitstream. 
     In an example, the specification may state that if a CRI SEI message with a specific target display is present at a random access point (RAP), then the specific target display may also be present in the following RAPs. A “target display” may be determined by the value of the syntax elements color_remap_id, color_remap_primaries, and color_remap_transfer_function. In another embodiment, the target display may be determined by the value of other syntax elements. 
     The examples described above may be combined in several ways. For example, in the following text intended for DVB (TS 101 154), HEVC HDR UHDTV Bitstreams using PQ10 contain color remapping information SEI messages may be specified in Recommendation ITU-T H.265/ISO/IEC 23008-2 clause D.3.32. If a CRI SEI message is present in the bitstream, the video postprocessor  31  may transmit the bitstream at each HEVC DVB_RAP. Further, video postprocessor  31  may set the syntax element color_remap_video_signal_info_present_flag to “1”, so that color_remap_full_range_flag, color_remap_primaries, color_remap_transfer_function, color_remap_matrix_coefficients are present. Video postprocessor  31  may set color_remap_primaries to “1” or “9”. Video postprocessor  31  may set color_remap_matrix_coefficients to “0”, “1” or “9”. Video postprocessor  31  may set color_remap_transfer_function to “1”, “14” or “16”. Video postprocessor  31  may set color_remap_input_bit_depth and color_remap_bit_depth to “8”, “10” or “12”. Video postprocessor  21  may only make changes to any of the syntax elements color_remap_full_range_flag, color_remap_primaries, color_remap_transfer_function, color_remap_matrix_coefficients, color_remap_input_bit_depth and color_remap_output_bit_depth at a HEVC DVB_RAP. Video postprocessor  31  may set color_remap_id to less than “256”. Video postprocessor  31  may determine input color coefficients by the color_remap_id syntax element value such that when color_remap_id is even, the input is in YCbCr, and when color_remap_id is odd, the input is in GBR. 
     When a color remapping information SEI message is present for a particular target display in an HEVC DVB_RAP picture, video postprocessor  31  may include a CRI SEI message for the same target display at least for each subsequent HEVC DVB_RAP. A “target display” is determined by the value of the syntax elements color_remap_id, color_remap_primaries, and color_remap_transfer_function. 
     In some examples, video postprocessor  31  may mask a few bits of a fixed representation of the syntax element for an assignment of the codewords of the syntax element color_remap_id. The table for ue(v) codeword interpretation is given below. When the bit string is “read” as an integer, then subtracting the integer by one gives the value of codeNum. 
     
       
         
           
               
               
             
               
                   
               
               
                 Bit string 
                 codeNum 
               
               
                   
               
             
            
               
                      1 
                 0 
               
               
                    0 1 0 
                 1 
               
               
                    0 1 1 
                 2 
               
               
                   0 0 1 0 0 
                 3 
               
               
                   0 0 1 0 1 
                 4 
               
               
                   0 0 1 1 0 
                 5 
               
               
                   0 0 1 1 1 
                 6 
               
               
                 0 0 0 1 0 0 0 
                 7 
               
               
                 0 0 0 1 0 0 1 
                 8 
               
               
                 0 0 0 1 0 1 0 
                 9 
               
               
                 . . . 
                 . . . 
               
               
                   
               
            
           
         
       
     
     Let ColorRemapId be the code number associated with the signalled color_remap_id, and is represented as a 32-bit integer. The bitmap representation is given below: 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
                   
               
             
            
               
                 31 
                 30 
                 29 
                 28 
                 27 
                 26 
                 25 
                 24 
                 23 
                 22 
                 21 
                 20 
                 19 
                 18 
                 17 
                 16 
               
               
                 15 
                 14 
                 13 
                 12 
                 11 
                 10 
                 9 
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                 0 
               
               
                   
               
            
           
         
       
     
     Since the values 256 to 511, inclusive, and from 2 31  to 2 32 −2, inclusive, are reserved by ITU-T|ISO/IEC, this reserves bits  8  and  31  to be fixed to 0. The remaining bits are available to indicate the purpose of the SEI message. The following table provides the interpretation of the bits. 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 b0 
                 Domain of processing 
                 0 - YCbCr, 
               
               
                   
                   
                 1 - RGB 
               
               
                 b7:b1 
                 Target peak luminance 
                 x = b7:b1 
               
               
                   
                 (TPL) 
                 T ml  = 100* (x + 1) 
               
               
                   
                   
                 where, 
               
               
                   
                   
                 T ml  = peak luminance of the 
               
               
                   
                   
                 display for which the contents of 
               
               
                   
                   
                 the CRI SEI message are provided 
               
               
                   
                   
                 for display adaptation 
               
               
                 b10:b9 
                 Target display color 
                 y = b10:b9 
               
               
                   
                 gamut (TDCG) 
                 y = 0, TDCG are defined as in 
               
               
                   
                   
                 BT.2020 (refer to value of 9 for 
               
               
                   
                   
                 color_primaries in HEVC Spec.) 
               
               
                   
                   
                 y = 1, TDCG are defined as in 
               
               
                   
                   
                 BT.709 (refer to value of 1 for 
               
               
                   
                   
                 color_primaries in HEVC Spec.) 
               
               
                   
                   
                 y = 2, TDCG are defined as in SMPTE 
               
               
                   
                   
                 EG 432-1 (2010) (refer to value of 3 
               
               
                   
                   
                 for color_primaries in HEVC Spec.) 
               
               
                   
                   
                 y = 3, Reserved for future use 
               
               
                   
                   
                 by ATSC 
               
               
                 b12:b11 
                 Target transfer 
                 z = b12:b11 
               
               
                   
                 function (TTF) 
                 z = 0, value of crtf is 16 
               
               
                   
                   
                 z = 1, value of crtf is one 
               
               
                   
                   
                 of 1, 6, 14, and 15 
               
               
                   
                   
                 z = 2 and 3 Reserved for 
               
               
                   
                   
                 future use by ATSC where, crtf 
               
               
                   
                   
                 is color_remap_transfer_function 
               
               
                 b14:b13 
                 Target color primaries 
                 w = b14:b13 
               
               
                   
                 (TCP) 
                 w = 0, TCP are defined as in 
               
               
                   
                   
                 BT.2020 (refer to value of 9 for 
               
               
                   
                   
                 color_primaries in HEVC Spec.) 
               
               
                   
                   
                 w = 1, TCP are defined as in 
               
               
                   
                   
                 BT.709 (refer to value of 1 for 
               
               
                   
                   
                 color_primaries in HEVC Spec.) 
               
               
                   
                   
                 w = 2, TCP are defined as in 
               
               
                   
                   
                 SMPTE EG 432-1 (2010) (refer to 
               
               
                   
                   
                 value of 3 for color_primaries in 
               
               
                   
                   
                 HEVC Spec.) 
               
               
                   
                   
                 w = 3, Reserved for future use 
               
               
                   
                   
                 by ATSC 
               
               
                   
               
            
           
         
       
     
     The above table is only one example of mapping described for the ColorRemapId and various characteristics of the content and display. It is to be understood that other configurations of the table (including other characteristics of the content or display, more bits for one or more characteristics, different mapping for certain bits and their interpretation, etc.) also fall within this disclosure. 
     In one example, only a subset of the set of parameters including target peak luminance, three-dimensional computer graphics (TDCG), and transmission control protocol (TCP) are signaled, and no explicit constraints are put on the rest of the bits. When a receiver (e.g. ATSC receiver, DVB receiver, sink device  32  or processor  33 ) receives a bitstream with one or SEI messages, the receiver parses the color_remap_id and based on the capabilities of the display/sink, chooses a subset of the one or more SEI messages and forwards the subset of SEI message to the display/sink, wherein, capabilities of the display may be advertised by the display using feedback messages, is predetermined, or conveyed to the receiver by other means, choosing a subset of the one or more SEI messages is performed by parsing the syntax element color_remap_id or the variable ColorRemapId, and based on the bits of ColorRemapId and the associated characteristics, determine the subset of SEI messages to be suitable to the display/sink. 
     In one example, a receiver (e.g., sink device  32  or processor  33 ) has to parse only a subset of the bits of the ColorRemapId to determine the characteristics associated with the CRI SEI message. The value of the other bits is unrelated to the target display characteristics. In another example, the receiver performs the association of bits of ColorRemapId only for characteristics that are not included in the CRI SEI message (e.g. TDCG, TPL). 
     In another example, the determination of subset of SEI messages to be suitable for a display is made by parsing the bits of the ColorRemapId as well as one or more syntax elements that are signaled in the CRI SEI message. For example, only domain of processing, TDCG and TPL are associated with bits in ColorRemapId and the suitability is determined by parsing ColorRemapId as well as one or more of the syntax elements in the CRI, e.g., color_remap_full_range_flag, color_remap_primaries, color_remap_transfer_function and color_remap_matrix_coefficients. 
     In some examples, other parameters in the CRI SEI message may also be assigned bits in the colour_remap_id; e.g. colour_remap_full_range_flag, colour_remap_primaries, colour_remap_transfer_function and colour_remap_matrix_coefficients, colour_remap_input_bit_depth and colour_remap_output_bit_depth. 
       FIG. 8  is a block diagram illustrating an example of video encoder  20 . Video encoder  20  may perform intra- and inter-coding of video blocks within video slices in a target color container that have been processed by video preprocessor  19 . Intra-coding relies on spatial prediction to reduce or remove spatial redundancy in video within a given video frame or picture. Inter-coding relies on temporal prediction to reduce or remove temporal redundancy in video within adjacent frames or pictures of a video sequence. Intra-mode (I mode) may refer to any of several spatial based coding modes. Inter-modes, such as uni-directional prediction (P mode) or bi-prediction (B mode), may refer to any of several temporal-based coding modes. 
     In the example of  FIG. 8 , video preprocessor  19  may be integrated with video encoder  20  in a single device. Video preprocessor  19  may be implemented as any of a variety of suitable encoder circuitry, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware or any combinations thereof. When the techniques are implemented partially in software, a device may store instructions for the software in a suitable, non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. As discussed above, in other examples, video preprocessor  19  may be separate devices from video encoder  20 , respectively. 
     As shown in  FIG. 8 , video encoder  20  receives a current video block within a video frame to be encoded. In the example of  FIG. 7 , video encoder  20  includes mode select unit  40 , a video data memory  41 , decoded picture buffer  64 , summer  50 , transform processing unit  52 , quantization unit  54 , and entropy encoding unit  56 . Mode select unit  40 , in turn, includes motion compensation unit  44 , motion estimation unit  42 , intra prediction processing unit  46 , and partition unit  48 . For video block reconstruction, video encoder  20  also includes inverse quantization unit  58 , inverse transform processing unit  60 , and summer  62 . A deblocking filter (not shown in  FIG. 7 ) may also be included to filter block boundaries to remove blockiness artifacts from reconstructed video. If desired, the deblocking filter would typically filter the output of summer  62 . Additional filters (in loop or post loop) may also be used in addition to the deblocking filter. Such filters are not shown for brevity, but if desired, may filter the output of summer  50  (as an in-loop filter). 
     Video data memory  41  may store video data to be encoded by the components of video encoder  20 . The video data stored in video data memory  41  may be obtained, for example, from video source  18 . Decoded picture buffer  64  may be a reference picture memory that stores reference video data for use in encoding video data by video encoder  20 , e.g., in intra- or inter-coding modes. Video data memory  41  and decoded picture buffer  64  may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Video data memory  41  and decoded picture buffer  64  may be provided by the same memory device or separate memory devices. In various examples, video data memory  41  may be on-chip with other components of video encoder  20 , or off-chip relative to those components. 
     During the encoding process, video encoder  20  receives a video frame or slice to be coded. The frame or slice may be divided into multiple video blocks. Motion estimation unit  42  and motion compensation unit  44  perform inter-predictive coding of the received video block relative to one or more blocks in one or more reference frames to provide temporal prediction. Intra prediction processing unit  46  may alternatively perform intra-predictive coding of the received video block relative to one or more neighboring blocks in the same frame or slice as the block to be coded to provide spatial prediction. Video encoder  20  may perform multiple coding passes, e.g., to select an appropriate coding mode for each block of video data. 
     Moreover, partition unit  48  may partition blocks of video data into sub-blocks, based on evaluation of previous partitioning schemes in previous coding passes. For example, partition unit  48  may initially partition a frame or slice into LCUs, and partition each of the LCUs into sub-CUs based on rate-distortion analysis (e.g., rate-distortion optimization). Mode select unit  40  may further produce a quadtree data structure indicative of partitioning of an LCU into sub-CUs. Leaf-node CUs of the quadtree may include one or more PUs and one or more TUs. 
     Mode select unit  40  may select one of the coding modes, intra or inter, e.g., based on error results, and provides the resulting intra- or inter-coded block to summer  50  to generate residual block data and to summer  62  to reconstruct the encoded block for use as a reference frame. Mode select unit  40  also provides syntax elements, such as motion vectors, intra-mode indicators, partition information, and other such syntax information, to entropy encoding unit  56 . 
     Motion estimation unit  42  and motion compensation unit  44  may be highly integrated, but are illustrated separately for conceptual purposes. Motion estimation, performed by motion estimation unit  42 , is the process of generating motion vectors, which estimate motion for video blocks. A motion vector, for example, may indicate the displacement of a PU of a video block within a current video frame or picture relative to a predictive block within a reference picture (or other coded unit) relative to the current block being coded within the current picture (or other coded unit). A predictive block is a block that is found to closely match the block to be coded, in terms of pixel difference, which may be determined by sum of absolute difference (SAD), sum of square difference (SSD), or other difference metrics. In some examples, video encoder  20  may calculate values for sub-integer pixel positions of reference pictures stored in decoded picture buffer  64 . For example, video encoder  20  may interpolate values of one-quarter pixel positions, one-eighth pixel positions, or other fractional pixel positions of the reference picture. Therefore, motion estimation unit  42  may perform a motion search relative to the full pixel positions and fractional pixel positions and output a motion vector with fractional pixel precision. 
     Motion estimation unit  42  calculates a motion vector for a PU of a video block in an inter-coded slice by comparing the position of the PU to the position of a predictive block of a reference picture. The reference picture may be selected from a first reference picture list (List 0) or a second reference picture list (List 1), each of which identify one or more reference pictures stored in decoded picture buffer  64 . Motion estimation unit  42  sends the calculated motion vector to entropy encoding unit  56  and motion compensation unit  44 . 
     Motion compensation, performed by motion compensation unit  44 , may involve fetching or generating the predictive block based on the motion vector determined by motion estimation unit  42 . Again, motion estimation unit  42  and motion compensation unit  44  may be functionally integrated, in some examples. Upon receiving the motion vector for the PU of the current video block, motion compensation unit  44  may locate the predictive block to which the motion vector points in one of the reference picture lists. Summer  50  forms a residual video block by subtracting pixel values of the predictive block from the pixel values of the current video block being coded, forming pixel difference values, as discussed below. In general, motion estimation unit  42  performs motion estimation relative to luma components, and motion compensation unit  44  uses motion vectors calculated based on the luma components for both chroma components and luma components. Mode select unit  40  may also generate syntax elements associated with the video blocks and the video slice for use by video decoder  30  in decoding the video blocks of the video slice. 
     Intra prediction processing unit  46  may intra-predict a current block, as an alternative to the inter-prediction performed by motion estimation unit  42  and motion compensation unit  44 , as described above. In particular, intra prediction processing unit  46  may determine an intra-prediction mode to use to encode a current block. In some examples, intra prediction processing unit  46  may encode a current block using various intra-prediction modes, e.g., during separate encoding passes, and intra prediction processing unit  46  (or mode select unit  40 , in some examples) may select an appropriate intra-prediction mode to use from the tested modes. 
     For example, intra prediction processing unit  46  may calculate rate-distortion values using a rate-distortion analysis for the various tested intra-prediction modes, and select the intra-prediction mode having the best rate-distortion characteristics among the tested modes. Rate-distortion analysis generally determines an amount of distortion (or error) between an encoded block and an original, unencoded block that was encoded to produce the encoded block, as well as a bit rate (that is, a number of bits) used to produce the encoded block. Intra prediction processing unit  46  may calculate ratios from the distortions and rates for the various encoded blocks to determine which intra-prediction mode exhibits the best rate-distortion value for the block. 
     After selecting an intra-prediction mode for a block, intra prediction processing unit  46  may provide information indicative of the selected intra-prediction mode for the block to entropy encoding unit  56 . Entropy encoding unit  56  may encode the information indicating the selected intra-prediction mode. Video encoder  20  may include in the transmitted bitstream configuration data, which may include a plurality of intra-prediction mode index tables and a plurality of modified intra-prediction mode index tables (also referred to as codeword mapping tables), definitions of encoding contexts for various blocks, and indications of a most probable intra-prediction mode, an intra-prediction mode index table, and a modified intra-prediction mode index table to use for each of the contexts. 
     Video encoder  20  forms a residual video block by subtracting the prediction data from mode select unit  40  from the original video block being coded. Summer  50  represents the component or components that perform this subtraction operation. Transform processing unit  52  applies a transform, such as a discrete cosine transform (DCT) or a conceptually similar transform, to the residual block, producing a video block comprising residual transform coefficient values. Transform processing unit  52  may perform other transforms which are conceptually similar to DCT. Wavelet transforms, integer transforms, sub-band transforms or other types of transforms could also be used. In any case, transform processing unit  52  applies the transform to the residual block, producing a block of residual transform coefficients. The transform may convert the residual information from a pixel value domain to a transform domain, such as a frequency domain. Transform processing unit  52  may send the resulting transform coefficients to quantization unit  54 . 
     Quantization unit  54  quantizes the transform coefficients to further reduce bit rate. The quantization process may reduce the bit depth associated with some or all of the coefficients. The degree of quantization may be modified by adjusting a quantization parameter. In some examples, quantization unit  54  may then perform a scan of the matrix including the quantized transform coefficients. Alternatively, entropy encoding unit  56  may perform the scan. 
     Following quantization, entropy encoding unit  56  entropy codes the quantized transform coefficients. For example, entropy encoding unit  56  may perform context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding or another entropy coding technique. In the case of context-based entropy coding, context may be based on neighboring blocks. Following the entropy coding by entropy encoding unit  56 , the encoded bitstream may be transmitted to another device (e.g., video decoder  30 ) or archived for later transmission or retrieval. 
     Inverse quantization unit  58  and inverse transform processing unit  60  apply inverse quantization and inverse transformation, respectively, to reconstruct the residual block in the pixel domain, e.g., for later use as a reference block. Motion compensation unit  44  may calculate a reference block by adding the residual block to a predictive block of one of the frames of decoded picture buffer  64 . Motion compensation unit  44  may also apply one or more interpolation filters to the reconstructed residual block to calculate sub-integer pixel values for use in motion estimation. Summer  62  adds the reconstructed residual block to the motion compensated prediction block produced by motion compensation unit  44  to produce a reconstructed video block for storage in decoded picture buffer  64 . The reconstructed video block may be used by motion estimation unit  42  and motion compensation unit  44  as a reference block to inter-code a block in a subsequent video frame. 
       FIG. 9  is a block diagram illustrating an example of  30  video decoder, in accordance with the techniques of this disclosure. In particular, video decoder  30  may decode video data into a target color container that may then be processed by video postprocessor  31 , as described above. In the example of  FIG. 8 , video decoder  30  includes an entropy decoding unit  70 , a video data memory  71 , motion compensation unit  72 , intra prediction processing unit  74 , inverse quantization unit  76 , inverse transform processing unit  78 , decoded picture buffer  82  and summer  80 . Video decoder  30  may, in some examples, perform a decoding pass generally reciprocal to the encoding pass described with respect to video encoder  20  ( FIG. 8 ). Motion compensation unit  72  may generate prediction data based on motion vectors received from entropy decoding unit  70 , while intra prediction processing unit  74  may generate prediction data based on intra-prediction mode indicators received from entropy decoding unit  70 . 
     In the example of  FIG. 8 , video postprocessor  31  may be integrated with video decoder  30  in a single device. Video postprocessor  31  may be implemented as any of a variety of suitable encoder circuitry, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware or any combinations thereof. When the techniques are implemented partially in software, a device may store instructions for the software in a suitable, non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. As discussed above, in other examples, video postprocessor  31  may be separate devices from video decoder  30 , respectively. 
     Video data memory  71  may store video data, such as an encoded video bitstream, to be decoded by the components of video decoder  30 . The video data stored in video data memory  71  may be obtained, for example, from computer-readable medium  16 , e.g., from a local video source, such as a camera, via wired or wireless network communication of video data, or by accessing physical data storage media. Video data memory  71  may form a coded picture buffer (CPB) that stores encoded video data from an encoded video bitstream. Decoded picture buffer  82  may be a reference picture memory that stores reference video data for use in decoding video data by video decoder  30 , e.g., in intra- or inter-coding modes. Video data memory  71  and decoded picture buffer  82  may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Video data memory  71  and decoded picture buffer  82  may be provided by the same memory device or separate memory devices. In various examples, video data memory  71  may be on-chip with other components of video decoder  30 , or off-chip relative to those components. 
     During the decoding process, video decoder  30  receives an encoded video bitstream that represents video blocks of an encoded video slice and associated syntax elements from video encoder  20 . Entropy decoding unit  70  of video decoder  30  entropy decodes the bitstream to generate quantized coefficients, motion vectors or intra-prediction mode indicators, and other syntax elements. Entropy decoding unit  70  forwards the motion vectors to and other syntax elements to motion compensation unit  72 . Video decoder  30  may receive the syntax elements at the video slice level and/or the video block level. 
     When the video slice is coded as an intra-coded (I) slice, intra prediction processing unit  74  may generate prediction data for a video block of the current video slice based on a signaled intra prediction mode and data from previously decoded blocks of the current frame or picture. When the video frame is coded as an inter-coded (i.e., B or P) slice, motion compensation unit  72  produces predictive blocks for a video block of the current video slice based on the motion vectors and other syntax elements received from entropy decoding unit  70 . The predictive blocks may be produced from one of the reference pictures within one of the reference picture lists. Video decoder  30  may construct the reference picture lists, List 0 and List 1, using default construction techniques based on reference pictures stored in decoded picture buffer  82 . Motion compensation unit  72  determines prediction information for a video block of the current video slice by parsing the motion vectors and other syntax elements, and uses the prediction information to produce the predictive blocks for the current video block being decoded. For example, motion compensation unit  72  uses some of the received syntax elements to determine a prediction mode (e.g., intra- or inter-prediction) used to code the video blocks of the video slice, an inter-prediction slice type (e.g., B slice or P slice), construction information for one or more of the reference picture lists for the slice, motion vectors for each inter-encoded video block of the slice, inter-prediction status for each inter-coded video block of the slice, and other information to decode the video blocks in the current video slice. 
     Motion compensation unit  72  may also perform interpolation based on interpolation filters. Motion compensation unit  72  may use interpolation filters as used by video encoder  20  during encoding of the video blocks to calculate interpolated values for sub-integer pixels of reference blocks. In this case, motion compensation unit  72  may determine the interpolation filters used by video encoder  20  from the received syntax elements and use the interpolation filters to produce predictive blocks. 
     Inverse quantization unit  76  inverse quantizes, i.e., de-quantizes, the quantized transform coefficients provided in the bitstream and decoded by entropy decoding unit  70 . The inverse quantization process may include use of a quantization parameter QP Y  calculated by video decoder  30  for each video block in the video slice to determine a degree of quantization and, likewise, a degree of inverse quantization that should be applied. Inverse transform processing unit  78  applies an inverse transform, e.g., an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process, to the transform coefficients in order to produce residual blocks in the pixel domain. 
     After motion compensation unit  72  generates the predictive block for the current video block based on the motion vectors and other syntax elements, video decoder  30  forms a decoded video block by summing the residual blocks from inverse transform processing unit  78  with the corresponding predictive blocks generated by motion compensation unit  72 . Summer  80  represents the component or components that perform this summation operation. If desired, a deblocking filter may also be applied to filter the decoded blocks in order to remove blockiness artifacts. Other loop filters (either in the coding loop or after the coding loop) may also be used to smooth pixel transitions, or otherwise improve the video quality. The decoded video blocks in a given frame or picture are then stored in decoded picture buffer  82 , which stores reference pictures used for subsequent motion compensation. Decoded picture buffer  82  also stores decoded video for later presentation on a display device, such as sink device  32  of  FIG. 1 . 
     In accordance with one or more techniques of this disclosure, components of video decoder  30 , including video postprocessor  31 , may be configured to perform any of the techniques described herein. For instance, video postprocessor  31  may determine, for a first set of one or more display capabilities, a first set of one or more remapping parameters. Video postprocessor  31  may then code, in a first supplemental enhancement information (SEI) message, the first set of one or more display capabilities and the first set of one or more remapping parameters. Video postprocessor  31  may also determine, for a second set of one or more display capabilities, a second set of one or more remapping parameters for the video data, and code, in a second SEI message, the second set of one or more display capabilities and the second set of one or more remapping parameters. Video postprocessor  31  may then send, to sink device  32  in bitstream  34 , the first SEI message, the second SEI message, and the video data. 
     In some examples, the first SEI message and the second SEI message may each be a CRI SEI message. Further, the one or more display capabilities indicated in the first and second SEI messages may include one or more color primaries, one or more color gamuts, a domain of processing, a peak luminance, or a transfer function. 
       FIG. 10  is a block diagram illustrating an example of sink device  32  that may implement techniques of this disclosure. In the example of  FIG. 10 , sink device  32  may include processor  33 , display device  36 , and video interface  38 . In other examples, sink device  32  may include more components, such as a power source or a video memory, or fewer components. 
     Processor  33  may be implemented as any of a variety of suitable encoder circuitry, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware or any combinations thereof. When the techniques are implemented partially in software, a device may store instructions for the software in a suitable, non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. As discussed above, in other examples, processor  33  may be separate devices from sink device  32 . 
     Display device  36  may include any structure capable of displaying video data to a user. Examples of display device  36  include liquid crystal displays (LCD), dot matrix displays, light emitting diode (LED) displays, organic light-emitting diode (OLED) displays, e-ink, or similar monochrome or color displays capable of outputting visible information to a user of sink device  32 . 
     Video interface  38  of sink device  32  may communicate with external devices (e.g., client device  14 ) via one or more wired and/or wireless networks by transmitting and/or receiving network signals on one or more networks. Examples of video interface  38  include a network interface card (e.g. such as an Ethernet card), an optical transceiver, a radio frequency transceiver, a GPS receiver, or any other type of device that can send and/or receive information. Other examples of video interface  38  may include short wave radios, cellular data radios, wireless network radios, as well as universal serial bus (USB) controllers. 
     In accordance with one or more techniques of this disclosure, components of sink device  32 , including processor  33 , may be configured to perform any of the techniques described herein. For instance, processor  33  may receive, in a bitstream, video data and a group of one or more supplemental enhancement information (SEI) messages. Each SEI message may include an indication of a set of one or more display capabilities and an indication of a set of one or more remapping parameters. For each SEI message of the group of one or more SEI messages, processor  33  may compare the respective set of one or more display capabilities indicated in the respective SEI message with a target set of one or more display capabilities for sink device  32  to determine a compatibility of the respective set of one or more display capabilities with the target set of one or more display capabilities. Responsive to determining that a first set of one or more display capabilities indicated by a first SEI message of the group of one or more SEI messages is compatible with the target set of one or more display capabilities for the sink device, processor  33  may adapt the video data using a respective set of one or more remapping parameters indicated by the first SEI message. 
     In examples where the group of one or more SEI messages comprise only a single SEI message, processor  33  may determine whether the set of one or more display capabilities in the single SEI message are compatible with the target set of one or more display capabilities. If the set of one or more display capabilities in the single SEI message are compatible with the target set of one or more display capabilities, processor  33  may adapt the video data using the remapping information in the single SEI message. Conversely, if the set of one or more display capabilities in the single SEI message are not compatible with the target set of one or more display capabilities, processor  33  may either refrain from adapting the video data or adjust the remapping information such that the video data may be displayed in accordance with the target display parameters. 
     In examples where the group of one or more SEI messages comprises a plurality of SEI messages, processor  33  may analyze each set of one or more display capabilities in the respective SEI messages and select an SEI message that is compatible with the target set of one or more display capabilities. Processor  33  may then adapt the video data using a respective set of one or more remapping parameters indicated by the selected SEI message. 
     In some examples, each SEI message in the group of one or more SEI messages comprises a color remapping information (CRI) SEI message for mapping the video data from a first color space to a second color space. Further, the one or more display capabilities indicated in each SEI message may include one or more color primaries, one or more color gamuts, a domain of processing, a peak luminance, or a transfer function. 
     In some examples, in adapting the video data, processor  33  may perform display adaptation based on the respective set of one or more remapping parameters indicated by the first SEI message. 
     In some instances, in determining that the first set of one or more display capabilities indicated by the first SEI message is compatible with the target set of one or more display capabilities for sink device  32 , processor  33  may determine the compatibility for the first set of one or more display capabilities to the target set of one or more display capabilities based on a similarity of the first set of one or more display capabilities with the target set of one or more display capabilities. In other instances, processor  33  may determine the compatibility for the first set of one or more display capabilities to the target set of one or more display capabilities based on a matching of the first set of one or more display capabilities with the target set of one or more display capabilities. 
       FIG. 11  is a flow diagram illustrating example techniques of a sink device configured to receive CRI SEI messages from a source device, in accordance with the techniques of this disclosure. The method of  FIG. 11  may be performed by sink device  32  and, specifically, processor  33  of sink device  32 . 
     For instance, processor  33  may receive, in a bitstream, video data ( 102 ) and a group of one or more supplemental enhancement information (SEI) messages ( 104 ). Each SEI message may include an indication of a set of one or more display capabilities and an indication of a set of one or more remapping parameters. For each SEI message of the group of one or more SEI messages, processor  33  may compare the respective set of one or more display capabilities indicated in the respective SEI message with a target set of one or more display capabilities for the sink device to determine a compatibility of the respective set of one or more display capabilities with the target set of one or more display capabilities ( 106 ). Responsive to determining that a first set of one or more display capabilities indicated by a first SEI message of the group of one or more SEI messages is compatible with the target set of one or more display capabilities for the sink device, processor  33  may adapt the video data using a respective set of one or more remapping parameters indicated by the first SEI message ( 108 ). 
     In examples where the group of one or more SEI messages comprise only a single SEI message, processor  33  may determine whether the set of one or more display capabilities in the single SEI message are compatible with the target set of one or more display capabilities. If the set of one or more display capabilities in the single SEI message are compatible with the target set of one or more display capabilities, processor  33  may adapt the video data using the remapping information in the single SEI message. Conversely, if the set of one or more display capabilities in the single SEI message are not compatible with the target set of one or more display capabilities, processor  33  may either refrain from adapting the video data or adjust the remapping information such that the video data may be displayed in accordance with the target display parameters. 
     In examples where the group of one or more SEI messages comprises a plurality of SEI messages, processor  33  may analyze each set of one or more display capabilities in the respective SEI messages and select an SEI message that is compatible with the target set of one or more display capabilities. Processor  33  may then adapt the video data using a respective set of one or more remapping parameters indicated by the selected SEI message. 
     In some examples, each SEI message in the group of one or more SEI messages comprises a color remapping information (CRI) SEI message for mapping the video data from a first color space to a second color space. Further, the one or more display capabilities indicated in each SEI message may include one or more color primaries, one or more color gamuts, a domain of processing, a peak luminance, or a transfer function. 
     In some examples, in adapting the video data, processor  33  may perform display adaptation based on the respective set of one or more remapping parameters indicated by the first SEI message. 
     In some instances, in determining that the first set of one or more display capabilities indicated by the first SEI message is compatible with the target set of one or more display capabilities for sink device  32 , processor  33  may determine the compatibility for the first set of one or more display capabilities to the target set of one or more display capabilities based on a similarity of the first set of one or more display capabilities with the target set of one or more display capabilities. In other instances, processor  33  may determine the compatibility for the first set of one or more display capabilities to the target set of one or more display capabilities based on a matching of the first set of one or more display capabilities with the target set of one or more display capabilities. 
       FIG. 12  is a flow diagram illustrating example techniques of a source device configured to send CRI SEI messages to a sink device, in accordance with the techniques of this disclosure. The method of  FIG. 12  may be performed by client device  14  and, specifically, video postprocessor  31  of client device  14 . 
     In accordance with one or more techniques of this disclosure, components of video decoder  30 , including video postprocessor  31 , may be configured to perform any of the techniques described herein. For instance, video postprocessor  31  may determine, for a first set of one or more display capabilities, a first set of one or more remapping parameters ( 112 ). Video postprocessor  31  may then code, in a first supplemental enhancement information (SEI) message, the first set of one or more display capabilities and the first set of one or more remapping parameters ( 114 ). Video postprocessor  31  may also determine, for a second set of one or more display capabilities, a second set of one or more remapping parameters for the video data ( 116 ), and code, in a second SEI message, the second set of one or more display capabilities and the second set of one or more remapping parameters ( 118 ). Video postprocessor  31  may then send, to sink device  32  in bitstream  34 , the first SEI message, the second SEI message, and the video data ( 120 ). 
     In some examples, the first SEI message and the second SEI message may each be a CRI SEI message for mapping the video data from a first color space to a second color space. Further, the one or more display capabilities indicated in the first and second SEI messages may include one or more color primaries, one or more color gamuts, a domain of processing, a peak luminance, or a transfer function. 
     It is to be recognized that depending on the example, certain acts or events of any of the techniques described herein can be performed in a different sequence, may be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the techniques). Moreover, in certain examples, acts or events may be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors, rather than sequentially. 
     In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer-readable media generally may correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium. 
     By way of example, and not limitation, such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but are instead directed to non-transitory, tangible storage media. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. 
     Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor,” as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and/or software modules configured for encoding and decoding, or incorporated in a combined codec. Also, the techniques could be fully implemented in one or more circuits or logic elements. 
     The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC) or a set of ICs (e.g., a chip set). Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, various units may be combined in a codec hardware unit or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and/or firmware. 
     Various examples of the disclosure have been described. Any combination of the described systems, operations, or functions is contemplated. These and other examples are within the scope of the following claims.