Source: https://patents.justia.com/patent/9788003
Timestamp: 2019-11-12 10:55:56
Document Index: 292868207

Matched Legal Cases: ['§371', 'Application No. 61', 'Application No. 61', 'Application No. 10', 'Application No. 2014', 'Application No. 2014', 'Application No. 12806944', 'Application No. 10', 'Application No. 10', 'Application No. 10', 'Application No. 101123830', 'Application No. 2014103489', 'Application No. 10', 'Application No. 104122835', 'Application No. 201280042854', 'Application No. 2', 'Application No. 105110841', 'Application No. 2016', 'Application No. 201280042854', 'application No. 2016129590', 'Application No. 106105704']

US Patent for Method and apparatus for multiplexing and demultiplexing video data to identify reproducing state of video data Patent (Patent # 9,788,003 issued October 10, 2017) - Justia Patents Search
Justia Patents Dvd With Mpeg2 Transport StreamUS Patent for Method and apparatus for multiplexing and demultiplexing video data to identify reproducing state of video data Patent (Patent # 9,788,003)
A method and apparatus for multiplexing and de-multiplexing video data. The method of multiplexing the video data involves syntax to a header of transmission unit data that is used to multiplex a clean random access (CRA) picture used in a random access, wherein the predetermined syntax indicates a reproduction status of the CRA picture, i.e., normal reproduction or reproduction according to a random access.
This application is a national stage entry under 35 U.S.C. §371(c) of International Patent Application No. PCT/KR2012/005256, filed Jul. 2, 2012, and claims priority from U.S. Provisional Patent Application No. 61/504,178, filed on Jul. 2, 2011 in the U.S. Patent and Trademark Office, and U.S. Provisional Patent Application No. 61/552,549, filed on Oct. 28, 2011 in the U.S. Patent and Trademark Office, the disclosures of which are incorporated herein in their entireties by reference.
Apparatuses and methods consistent with exemplary embodiments relate to encoding and decoding video, and more particularly, to a method and apparatus for multiplexing and de-multiplexing video data so as to identify whether a reproduction status of an intra picture that is reproduced in a decoding side is a random access reproduction status or a normal reproduction status.
A video codec including ITU-T H.261, ISO/IEC MPEG-1 Visual, ITU-T H.262(ISO/IEC MPEG-2 Visual), ITU-T H.264, ISO/IEC MPEG-4 Visual and ITU-T H.264(ISO/IEC MPEG-4 AVC) performs prediction encoding on a macroblock via inter prediction or intra prediction, generates a bitstream containing encoded image data according to a predetermined format defined by each video codec, and outputs the bitstream.
One or more exemplary embodiments defines a new type of an intra picture for random access reproduction, and provides a method and apparatus for identifying a normal reproduction status and a random access reproduction status by hardware or software related to a decoding apparatus.
According to one or more embodiments, a reproduction status of an intra picture may be identified via syntax included in predetermined transmission data.
According to one or more embodiments, a normal reproduction status and a random access reproduction status may be identified by hardware or software related to a decoding apparatus, so that it is possible to save a system resource that is used to decode pictures that are not required to be decoded.
According to one or more embodiments, there is provided a method of multiplexing video data so as to identify a reproduction status of the video data, the method including operations of encoding pictures forming the video data based on data units having a hierarchical structure; in response to a transmission request for the encoded data from a decoding apparatus, determining whether the transmission request is according to normal reproduction or is for a random access; and adding predetermined syntax to transmission unit data to multiplex an intra picture used in the random access and having leading pictures that precede the intra picture in a display order but are encoded after the intra picture in an encoding order, according to a result of the determining, wherein the predetermined syntax indicates which request from among a request via the normal reproduction and a request via the random access is related to the intra picture.
According to another embodiment, there is provided an apparatus for multiplexing video data so as to identify a reproduction status of the video data, the apparatus including a video encoder for encoding pictures forming the video data based on data units having a hierarchical structure; a reproduction status identifier for, in response to a transmission request for the encoded data from a decoding apparatus, determining whether the transmission request is according to normal reproduction or is for a random access; and a multiplexer for adding predetermined syntax to transmission unit data to multiplex an intra picture used in the random access and having leading pictures that precede the intra picture in a display order but are encoded after the intra picture in an encoding order, according to a result of the determining, wherein the predetermined syntax indicates which request from among a request via the normal reproduction and a request via the random access is related to the intra picture.
According to another embodiment, there is provided a method of de-multiplexing video data so as to identify a reproduction status of the video data, the method including operations of receiving transmission unit data used to multiplex a bitstream generated by encoding pictures forming the video data based on hierarchical-structure data units; obtaining predetermined syntax from the transmission unit data to multiplex an intra picture used in a random access and having leading pictures that precede the intra picture in a display order but are encoded after the intra picture in a decoding order, wherein the predetermined syntax indicates whether the intra picture is decoded according to a normal reproduction status or according to a random access status; and identifying whether the intra picture is reproduced according to normal reproduction or according to a random access, based on the obtained predetermined syntax.
According to another exemplary, there is provided an apparatus for de-multiplexing video data so as to identify a reproduction status of the video data, the apparatus including an inverse-multiplexer for receiving transmission unit data used to multiplex a bitstream generated by encoding pictures forming the video data based on hierarchical-structure data units, obtaining predetermined syntax from the transmission unit data to multiplex an intra picture used in a random access and having leading pictures that precede the intra picture in a display order but are encoded after the intra picture in a decoding order, wherein the predetermined syntax indicates whether the intra picture is decoded according to a normal reproduction status or according to a random access status; and a reproduction status identifier for identifying whether the intra picture is reproduced according to normal reproduction or according to a random access, based on the obtained predetermined syntax.
FIG. 1 is a block diagram of an apparatus for encoding a video, according to an exemplary embodiment.
FIG. 2 is a block diagram of an apparatus for decoding a video, according to an exemplary embodiment.
FIG. 6 is a diagram illustrating deeper coding units according to depths, and partitions according to an exemplary embodiment.
FIG. 7 is a diagram for describing a relationship between a coding unit and transformation units, according to an exemplary embodiment.
FIGS. 10 through 12 are diagrams for describing a relationship between coding units, prediction units, and transformation units, according to an exemplary embodiment.
FIG. 13 is a diagram for describing a relationship between a coding unit, a prediction unit or a partition, and a transformation unit, according to encoding mode information.
FIGS. 14A and 14B illustrate a decoding process of a clean random access (CRA) picture in normal reproduction and a random access, according to an exemplary embodiment.
FIG. 15 illustrates a structure of a video data multiplexing apparatus, according to an exemplary embodiment.
FIG. 16 illustrates a structure of a network abstraction layer (NAL) unit, according to an exemplary embodiment.
FIGS. 17A and 17B illustrate a decoding process of a CRA picture in normal reproduction and a random access, according to another exemplary embodiment.
FIG. 18 is a flowchart of a method of multiplexing video data, according to an exemplary embodiment.
FIG. 19 illustrates a structure of a video data inverse-multiplexing apparatus 1900, according to an exemplary embodiment.
FIG. 20 is a flowchart of a method of inverse-multiplexing video data, according to an exemplary embodiment.
Hereinafter, exemplary embodiments will be described in detail with reference to the attached drawings. Throughout the specification, an image may include a still image and a moving picture and may be referred to as video. Also, throughout the specification, an image frame may be referred to as a picture.
FIG. 1 is a block diagram of a video encoding apparatus 100, according to an embodiment.
The maximum coding unit splitter 110 may split a current picture based on a maximum coding unit for the current picture of an image. If the current picture is larger than the maximum coding unit, image data of the current picture may be split into the at least one maximum coding unit. The maximum coding unit according to an exemplary embodiment may be a data unit having a size of 32×32, 64×64, 128×128, 256×256, etc., wherein a shape of the data unit is a square having a width and a length that are each a multiple of 2 and greater than 8. The image data may be output to the coding unit determiner 120 according to the at least one maximum coding unit.
The maximum coding unit is hierarchically split into coding units according to depths, and, as the depth increases, number of coding units increases. Also, even if coding units correspond to same depth in one maximum coding unit, it is determined whether to split each of the coding units corresponding to the same depth to a lower depth by measuring an encoding error of the image data of the each coding unit, separately. Accordingly, even when image data is included in one maximum coding unit, the image data is split to regions according to the depths and the encoding errors may differ according to regions in the one maximum coding unit, and thus the coded depths may differ according to regions in the image data. Thus, one or more coded depths may be determined in one maximum coding unit, and the image data of the maximum coding unit may be divided according to coding units of at least one coded depth.
A maximum depth according to an embodiment is an index related to the number of splitting times from a maximum coding unit to a minimum coding unit. A first maximum depth according to an embodiment may denote the total number of splitting times from the maximum coding unit to the minimum coding unit. A second maximum depth according to an exemplary embodiment may denote the total number of depth levels from the maximum coding unit to the minimum coding unit. For example, when a depth of the maximum coding unit is 0, a depth of a coding unit, in which the maximum coding unit is split once, may be set to 1, and a depth of a coding unit, in which the maximum coding unit is split twice, may be set to 2. Here, if the minimum coding unit is a coding unit in which the maximum coding unit is split four times, 5 depth levels of depths 0, 1, 2, 3 and 4 exist, and thus the first maximum depth may be set to 4, and the second maximum depth may be set to 5.
A data unit used as a base of the transformation will now be referred to as a ‘transformation unit’. A transformation depth indicating the number of splitting times to reach the transformation unit by splitting the height and width of the coding unit may also be set in the transformation unit. For example, in a current coding unit of 2N×2N, a transformation depth may be 0 when the size of a transformation unit is also 2N×2N, may be 1 when each of the height and width of the current coding unit is split into two equal parts, totally split into 4^1 transformation units, and the size of the transformation unit is thus N×N, and may be 2 when each of the height and width of the current coding unit is split into four equal parts, totally split into 4^2 transformation units and the size of the transformation unit is thus N/2×N/2. For example, the transformation unit may be set according to a hierarchical tree structure, in which a transformation unit of an upper transformation depth is split into four transformation units of a lower transformation depth according to the hierarchical characteristics of a transformation depth.
The minimum unit according to an exemplary embodiment may be a rectangular data unit obtained by splitting the minimum coding unit constituting the lowermost depth by 4, and may be a maximum rectangular data unit that may be included in all of the coding units, prediction units, partition units, and transformation units included in the maximum coding unit.
The maximum coding unit splitter 110 and the coding unit determiner 120 correspond to video coding layers that determine a reference frame of each of image frames forming an image sequence by performing motion estimation and motion compensation on each image frame of the image sequence according to coding units, and encode each image frame by using the determined reference frame.
Also, as will be described later, the output unit 130 maps syntax (max_dec_frame buffering) by a unit of a network abstraction layer (NAL) and thus generates a bitstream, wherein the syntax indicates a maximum size of a buffer required for a decoder to decode the image frames, syntax (num_reorder_frames) indicating the number of image frames required to be reordered, and syntax (max_latency_increase) indicating latency information of an image frame that has the greatest difference between an encoding order and a display order and that is from among the image frames forming the image sequence.
That is, data units containing the encoding information including the same split information may be gathered by observing the encoding information set assigned for the predetermined data unit from among the coding unit, the prediction unit, and the minimum unit, and the gathered data units may be considered to be one data unit to be decoded by the image data decoder 230 in the same encoding mode.
Also, the receiver 210 and the image data and encoding information extractor 220 perform an NAL decoding process in which syntax (max_dec_frame buffering) indicating a maximum size of a buffer required for a decoder to decode image frames, syntax (num_reorder_frames) indicating the number of image frames required to be reordered, and syntax (max_latency_increase) indicating latency information of an image frame that has the greatest difference between an encoding order and a display order and that is from among the image frames forming an image sequence are obtained from a bitstream and are output to the image data decoder 230.
Data output from the intra predictor 410, the motion estimator 420, and the motion compensator 425 is output as a quantized transformation coefficient through a transformer 430 and a quantizer 440. The quantized transformation coefficient is restored as data in a spatial domain through an inverse quantizer 460 and an inverse transformer 470, and the restored data in the spatial domain is output as the reference frame 495 after being post-processed through a deblocking unit 480 and a loop filtering unit 490. The quantized transformation coefficient may be output as a bitstream 455 through an entropy encoder 450. In particular, the entropy encoder 450 may map maximum decoded frame buffering syntax (max_dec_frame buffering) by a unit of a NAL and thus may generate a bitstream, wherein the maximum decoded frame buffering syntax (max_dec_frame buffering) indicates a maximum size of a buffer required for a decoder to decode image frames, number-of-reorder-frames syntax (num_reorder_frames) indicating the number of the image frames required to be reordered, maximum latency frame syntax (MaxLatencyFrame) indicating a maximum value of a difference value between an encoding order and a display order of the image frames forming an image sequence, or maximum latency increase syntax (max_latency_increase) to determine the maximum latency frame syntax(MaxLatencyFrame). In particular, the entropy encoder 450 according to the present embodiment includes the maximum decoded frame buffering syntax (max_dec_frame buffering) indicating a maximum size of a buffer required for a decoder to decode image frames, the number-of-reorder-frames syntax (num_reorder_frames) indicating the number of the image frames required to be reordered, and the maximum latency increase syntax (max_latency_increase) to determine the maximum latency frame syntax (MaxLatencyFrame), as essential elements, in a sequence parameter set (SPS) that is header information including information related to encoding of the entire image sequence.
A parser 510 parses encoded image data to be decoded and information about encoding required for decoding from a bitstream 505. In particular, the parser 510 obtains maximum decoded frame buffering syntax (max_dec_frame buffering) indicating a maximum size of a buffer required to decode image frames included as an essential element in an SPS, number-of-reorder-frames syntax (num_reorder_frames) indicating the number of the image frames required to be reordered, and maximum latency increase syntax (max_latency_increase) to determine a maximum latency frame syntax (MaxLatencyFrame) from a bitstream and outputs them to an entropy decoder 520. In FIG. 5, the parser 510 and the entropy decoder 520 are separate elements. However, the obtainment of the image data and the obtainment of each item of syntax information related to the encoded image data, which are performed by the parser 510, may be implemented to be performed by the entropy decoder 520.
The encoded image data is output as inverse quantized data through the entropy decoder 520 and an inverse quantizer 530, and the inverse quantized data is restored to image data in a spatial domain through a frequency inverse converter 540.
The image frames that are restored while passing through the intra predictor 550 and the motion compensator 560 may be post-processed through the deblocking unit 570 and may be output to a decoded picture buffer (DPB) 580. The DPB 580 stores a reference frame, changes a display order of the image frames, and stores the restored image frames so as to output the image frames. The DPB 580 stores the restored image frames, and sets a maximum size of a buffer required to normally decode the image sequence, by using the maximum decoded frame buffering syntax (max_dec_frame buffering) indicating the maximum size of the buffer required to decode the image frames, which is output from the parser 510 or the entropy decoder 520.
Also, the DPB 580 may determine whether or not to output a reference image frame that is previously decoded and stored, by using the number-of-reorder-frames syntax (num_reorder_frames) indicating the number of the image frames required to be reordered, and the maximum latency increase syntax (max_latency_increase) to determine the maximum latency frame syntax (MaxLatencyFrame). A process of outputting the reference image frame stored in the DPB 580 will be described in detail later.
In order for the image decoder 500 to be applied in the video decoding apparatus 200, all elements of the image decoder 500, i.e., the parser 510, the entropy decoder 520, the inverse quantizer 530, the frequency inverse converter 540, the intra predictor 550, the motion compensator 560, the deblocking unit 570, and the loop filtering unit 580 may perform decoding operations based on coding units having a tree structure for each maximum coding unit. Specifically, the intra prediction 550 and the motion compensator 560 may determine partitions and a prediction mode for each of the coding units having a tree structure, and the frequency inverse converter 540 may determine a size of a transformation unit for each coding unit.
The prediction unit and the partitions of a coding unit are arranged along the horizontal axis according to each depth. In other words, if the coding unit 610 having the size of 64×64 and the depth of 0 is a prediction unit, the prediction unit may be split into partitions included in the coding unit 610, i.e. a partition having a size of 64×64 included in the coding unit 610, partitions 612 having the size of 64×32, partitions 614 having the size of 32×64, or partitions 616 having the size of 32×32.
Similarly, a prediction unit of the coding unit 620 having the size of 32×32 and the depth of 1 may be split into partitions included in the coding unit 620, i.e. a partition having a size of 32×32 included in the coding unit 620, partitions 622 having a size of 32×16, partitions 624 having a size of 16×32, and partitions 626 having a size of 16×16.
The coding unit 650 having the size of 4×4 and the depth of 4 is the minimum coding unit and a coding unit of the lowermost depth may be split into partitions included in the coding unit 650, i.e. a partition having a size of 4×4 included in the coding unit 650, partitions 652 having a size of 4×2, partitions 654 having a size of 2×4, and partitions 656 having a size of 2×2.
TABLE 1 Split Information 0 Split (Encoding on Coding Unit having Size of 2N × 2N and Current Depth of d) Information 1
Intra Symmetrical Asymmetrical Split Split Coding Units Inter Partition Partition Information 0 of Information 1 of having Skip Type Type Transformation Transformation Lower Depth (Only Unit Unit of d + 1 2N × 2N) 2N × 2N 2N × nU 2N × 2N N × N 2N × N 2N × nD (Symmetrical N × 2N nL × 2N Type) N × N nR × 2N N/2 × N/2 (Asymmetrical Type)
As described above, the video encoding apparatus 100 and the video decoding apparatus 200 according to one or more exemplary embodiments perform encoding and decoding by splitting a maximum coding unit by using a coding unit equal to or less than the maximum coding unit. The data encoded in the video encoding apparatus 100 is multiplexed by using a transmission data unit appropriate for a protocol or a format of a communication channel, a storage media, a video editing system, a media framework, or the like, and the transmission data unit is transmitted to the video decoding apparatus 200.
In a case of reproduction of video data, the video decoding apparatus 200 restores the video data according to one of a trick play manner and a normal play manner and reproduces the video data. The trick play manner includes a normal play manner, a fast-forward manner or a fast-backward manner, and a random access manner. According to the normal play manner, all pictures included in the video data are sequentially processed and reproduced. According to the fast-forward manner or the fast-backward manner, a reference picture, i.e., an I picture in every predetermined period is selected and reproduced in a forward or backward manner according to a reproduction speed. According to the random access manner, reproduction is performed with a skip to a key picture, i.e., an I picture at a predetermined position. According to the H.264 standard, an instantaneous decoder refresh (IDR) picture is used as the key picture for the random access manner. The IDR picture is an intra picture to refresh a decoding apparatus when a corresponding picture is decoded. In more detail, when the IDR picture is decoded, a DPB marks a picture other than the IDR picture, which is previously decoded, as a non-reference picture, and a picture order count (POC) is also initialized. Also, a picture that is decoded after the IDR picture may always be behind the IDR picture in a display order, and may be decoded while not referring to a picture before the IDR picture.
According to the present embodiment, in addition to the IDR picture, a clean random access (CRA) picture is used as the key picture for the random access manner. The CRA picture may be referred to as a clean decoding refresh (CDR) picture or a deferred decoding refresh (DDR) picture. The CRA picture is an intra picture having pictures that precede in the display order but are encoded (or decoded) after the CRA picture in an encoding (or decoding) order. Hereinafter, a picture that is in the same group of pictures (GOP) as the CRA picture and that precedes the CRA picture in the display order but is encoded (or decoded) after the CRA picture in the encoding (or decoding) order is defined as a leading picture.
The IDR picture and the CRA picture are common in that they are key pictures for the random access manner and are intra pictures to be encoded (or decoded) without referring to another picture. With respect to the IDR picture, a picture that follows the IDR picture in the encoding (or decoding) order does not precede the IDR picture in the display order. However, as described above, with respect to the CRA picture, the leading picture follows the CRA picture in the encoding (or decoding) order but precedes the CRA picture in the display order. The decoding order and the encoding order indicate orders in a decoder and an encoder by which pictures are processed, and an encoding order of pictures is equal to a decoding order of the pictures. Accordingly, throughout the specification, the encoding order may mean the decoding order, or the decoding order may mean the encoding order.
FIGS. 14A and 14B illustrate a decoding process of a CRA picture in normal reproduction and a random access, according to an exemplary embodiment.
In FIGS. 14A and 14B, Bi and bi are Bi-predictive pictures that are predicted by using L0 prediction and L1 prediction, in which i indicates a display order, i.e., a POC. Also, Bi having a capital letter ‘B’ indicates a picture that is used as a reference picture of another picture, and bi having a lowercase letter ‘b’ indicates a picture that is not used as a reference picture of another picture.
Referring to FIG. 14A, in the normal reproduction, i.e., when all pictures are decoded and reproduced, leading pictures 1420 that are decoded after a CRA24 picture 1410 may be normally decoded by referring to a reference picture that is previously decoded. For example, when a B22 picture 1421 is bi-directionally predicted by using the L0 prediction that refers to a B18 picture 1401 and the L1 prediction that refers to the CRA24 picture 1410, in the normal reproduction, the B22 picture 1421 may be normally decoded by referring to the CRA24 picture 1410 and the B18 picture 1401 which are previously decoded and stored in a DPB 1430.
Referring to FIG. 14B, in a case where the CRA24 picture 1410 is decoded via the random access after a B6 picture 1402 is decoded, the L0 prediction for prediction of the B22 picture 1421 determines a reference picture according to a reference picture index in a direction of the L0 prediction. In this case, the B6 picture 1402 that is previously decoded and stored in a DPB 1440 may be determined as the reference picture for the L0 prediction of the B22 picture 1421. In this case, the reference picture for the L0 prediction of the B22 picture 1421 has to be the B18 picture 1401, but, due to the random access, a picture that refers to reference pictures between the B6 picture 1402 and the CRA24 picture 1410 cannot be normally decoded.
Also, referring back to FIG. 14A, because the leading pictures 1420 precede the CRA24 picture 1410 in a display order, after the CRA24 picture 1410 is decoded and displayed via the random access, the leading pictures 1420 are not displayed and thus are not required to be decoded.
However, the video decoding apparatus 200 simply and sequentially decode and output a plurality of pieces of input video data, and thus cannot recognize whether the leading pictures 1420 are pictures that are decoded after the CRA24 picture 1410 in the normal reproduction or via the random access. In other words, the video decoding apparatus 200 cannot recognize whether the CRA24 picture 1410 is a picture that is decoded via the random access or is decoded in the normal reproduction.
Thus, one or more exemplary embodiments may provide multiplexing and de-multiplexing methods by which syntax for identification of a reproduction status of a CRA picture is added to data in a predetermined transmission unit, wherein the data is obtained by multiplexing the CRA picture that is encoded to be identified whether the CRA picture is encoded according to a random access or is encoded according to normal reproduction.
First, a video data multiplexing apparatus and method thereof will be described.
FIG. 15 illustrates a structure of a video data multiplexing apparatus 1500, according to an exemplary embodiment.
Referring to FIG. 15, the video data multiplexing apparatus 1500 includes a video encoder 1510, a multiplexer 1520, and a reproduction status identifier 1530.
The video encoder 1510 corresponds to the video encoding apparatus 100 of FIG. 1, and encodes video data based on the hierarchical coding unit in a video coding layer in which the encoding of the video data is processed. The multiplexer 1520 multiplexes the video data by using a transmission data unit appropriate for a protocol or a format of a communication channel, a storage media, a video editing system, a media framework, or the like. As will be described later, the multiplexer 1520 may multiplex the video data by using a NAL unit that is a transmission unit in an NAL.
When there is a transmission request for the encoded video data from a client connected via the communication channel, an apparatus managing the storage media, the video editing system, and the media framework (hereinafter, collectively referred to as a “decoding apparatus”), the reproduction status identifier 1530 identifies whether the transmission request is for sequential reproduction of the video data according to normal reproduction or is for transmission of the video data according to a random access. The reproduction status identifier 1530 may compare a display time of a picture requested by the decoding apparatus with a display time of a picture currently displayed by a current decoding apparatus, and then may identify that the transmission request of the video data occurs according to the random access.
The multiplexer 1520 adds predetermined syntax to the NAL unit including information about a CRA picture that is a key picture for the random access, based on the identification result by the reproduction status identifier 1530, wherein the predetermined syntax indicates which request from among a request via the normal reproduction and a request via the random access is related to the CRA picture.
FIG. 16 illustrates a structure of an NAL unit 1600, according to an exemplary embodiment.
Referring to FIG. 16, the NAL unit 1600 is formed of an NAL header 1610 and a raw byte sequence payload (RBSP) 1620. A RBSP filling bit 1630 is a length adjustment bit attached to an end of the RBSP 1620 so as to express a length of the RBSP 1620 as an 8-bit multiple. The RBSP filling bit 1630 has a pattern such as ‘100 . . . ’ that starts with ‘1’ and continues with sequential ‘0’ determined according to the length of the RBSP 1620. In this regard, by searching for ‘1’ that is an initial bit value, a position of a last bit of the RBSP 1620 which is right before the initial bit value may be determined.
The NAL header 1610 includes a forbidden_zero_bit 1611 having a value of 0, a flag nal_ref_idc indicating whether the NAL unit 1600 includes a slice to be a reference picture, and the like. In particular, the NAL header 1610 according to the present embodiment includes status identification syntax 1612 indicating which request from among a request via normal reproduction and a request via a random access is related to a CRA picture that is added to the NAL unit 1600 including information about the CRA picture.
The status identification syntax 1612 to identify a reproduction status of the CRA picture may be included in an identifier (nal unit type) indicating a type of the NAL unit 1600. That is, an NAL unit that is used to decode a CRA picture provided according to a request via normal reproduction may have an identifier (nal unit type) that is a different type from an identifier (nal unit type) of an NAL unit that is used to decode a CRA picture provided according to a request via a random access.
Table 2 shows types of the NAL unit 1600 according to values of an identifier (nal unit type).
TABLE 2 nal_unit_type Types of NAL unit
0 Unspecified 1 Picture slice other than RAP, TFD, TLA pictures 2 TFD picture slice 3 TLA picture slice other than TFD 4, 5 Slice of CRA picture 6, 7 Slice of BLA picture 8 Slice of IDR picture 9-24 Reserved for future extension 25 VPS 26 SPS 27 PPS 28 APS 29 Access Unit (AU) delimiter 30 Filler data 31 Supplemental Enhancement Information (SEI) 32-47 Reserved for future extension 48-63 Unspecified
The multiplexer 1520 allocates different values of 4 and 5 in Table 2 above, as an identifier (nal unit type), to the NAL unit that is used to decode the CRA picture provided according to the request via the normal reproduction, and to the NAL unit that is used to decode the CRA picture provided according to the request via the random access. By doing so, the multiplexer 1520 may signal that an NAL unit including information about a CRA picture is which one from among a CRA picture provided according to normal reproduction and a CRA picture provided according to a random access.
Also, the multiplexer 1520 may use a flag as syntax added to a header of the NAL unit, wherein the flag is set to have one of different values of 0 and 1 with respect to the NAL unit used to decode the CRA picture provided according to the request via the normal reproduction, and the NAL unit used to decode the CRA picture provided according to the request via the random access.
According to the current embodiment, the multiplexer 1520 adds type information, which directly indicates the reproduction status of the CRA picture, to the NAL unit. In another embodiment, the multiplexer 1520 may not directly signal a type of the reproduction status of the CRA picture but may identify whether the CRA picture is reproduced according to the normal reproduction or is reproduced according to the random access, by using a counter of key pictures that are decoded before the CRA picture, and by using information about a POC of a picture that is used as a reference picture of leading pictures.
Referring to FIGS. 17A and 17B, a B38 picture 1710 and a B40 picture 1720 are pictures that are decoded before a CRA44 picture and that are referred to by b41, B42, and b43 pictures that are leading pictures. The B38 picture 1710 is referred to by the B42 picture that is the leading picture, and the B40 picture 1720 is referred to by the B41 picture that is the leading picture. The B38 picture 1710 and the B40 picture 1720 which precede a CRA picture in a decoding order and are used as reference pictures of the leading pictures are defined as a brother picture. The reason why the brother picture is defined is that it is possible to identify whether the CRA picture is reproduced according to normal reproduction or is reproduced according to a random access, by using a POC of the brother picture.
For example, referring to FIG. 17A, while pictures are sequentially decoded in a normal reproduction status, when the CRA44 picture is decoded, the B38 picture 1710 and the B40 picture 1720 that are previously decoded are stored in a DPB 1740. If a POC value of 38 of the B38 picture 1710, and a POC value of 40 of the B40 picture 1720, which are brother pictures, are added to a slice header of the CRA44 picture, a decoder may compare a POC of pictures that are previously decoded and stored in the DPB 1740 at a time of decoding the CRA44 picture with the POC of the brother pictures included in the slice header of the CRA44 picture and thus may identify whether the CRA44 picture is reproduced according to the random access or is reproduced according to the normal reproduction. Since a reproduction order, i.e., a decoding order, jumps to the CRA44 picture in the reproduction according to the random access, if the POC of the pictures that are previously decoded and stored in the DPB 1740 at a time of decoding the CRA44 picture does not match with the POC of the brother pictures, there is a high possibility that the CRA44 picture is reproduced according to the random access.
However, there is also a possibility that the CRA44 picture may be misidentified as to whether the CRA44 picture is reproduced according to the random access or is reproduced according to the normal reproduction, by using only information about the POC of the brother pictures.
For example, referring to FIG. 17B, in a case where the CRA44 picture is decoded according to the random access after a B40 picture 1745 is decoded, when the CRA44 picture is decoded, a POC value of 40 of the B40 picture 1745 is stored in a DPB 1780, and a POC value of 40 of a brother picture stored in the slice header of the CRA44 picture is equal to the POC value of a previous picture stored in the DPB 1780, so that a decoder may misidentify that the CRA44 picture is reproduced according to the normal reproduction. As described above, a reproduction status of a CRA picture may not be correctly identified by using only information about a POC of a brother picture. This is because every time an IDR picture is decoded, a POC is reset, so that a reference picture that is different from an actual reference picture to be referred to by brother pictures in a random access may have the same POC as a POC of the brother pictures.
Thus, the multiplexer 1520 adds POC information of a brother picture to syntax of transmission unit data of a CRA picture, obtains a count from a POC discontinuity counter (PDC) that is a counter having a value increasing by 1 whenever a POC is reset or the CRA picture is encoded while pictures before the CRA picture are encoded, and adds the count from the PDC to the syntax.
Referring back to FIG. 17A, as described above, the multiplexer 1520 increases the count from the PDC by 1 whenever the POC is reset or the CRA picture is encoded while the pictures are encoded. Since the POC is reset whenever the IDR picture is encoded, a value of the PDC increases by 1 whenever the IDR picture is encoded, and the value of the count from the PDC increases by 1 when a previous CRA picture except for the CRA44 picture is encoded. The multiplexer 1520 adds the value of the PDC with the POC of the brother pictures to a header 1730 of the transmission unit data of the CRA picture. The decoder in the same manner as an encoder increases the count from the PDC by 1 whenever the POC is reset while the input transmission unit data is decoded, i.e., whenever the IDR picture is decoded or the CRA picture is decoded. As illustrated in FIG. 17A, in a case of normal reproduction, when the CRA44 picture is decoded, a PDC value included in the header 1730 of the transmission unit data used to multiplex the CRA44 picture, and a PDC value 1745 counted while pictures are decoded by the decoder are all 3.
Referring back to FIG. 17B, in a case of a random access, one IDR picture and one CRA picture which are decoded before the CRA44 picture exist, so that, when the CRA44 picture is decoded according to the random access, a PDC value 1785 is 2, which is different from a PDC value having 3 and included in a header 1770 of transmission unit data that is used to multiplex the CRA44 picture. Thus, based on the mismatch between the PDC values, the decoder may determine that a current CRA picture is reproduced according to the random access.
Referring to FIG. 18, in operation 1810, the video encoder 1510 encodes pictures forming video data based on data units having a hierarchical structure. As described above, the video encoder 1510 determines tree-structure encoding units including encoding units with encoding depths from among deeper encoding units according to depths which are hierarchically formed according to depths indicating a spatial split count of at least one maximum encoding unit obtained by splitting a picture forming video by using a maximum size encoding unit, determines a partition for prediction encoding for each of the encoding units with encoding depths, performs transformation based on hierarchical-structure transformation units, and then determines tree-structure transformation units. In the determination of a hierarchical data unit, a structure of an optimal hierarchical data unit may be determined based on a rate distortion (RD) cost.
In operation 1820, in response to a transmission request for encoded data from a decoding apparatus, the reproduction status identifier 1530 determines whether the transmission request is according to normal reproduction or is for a random access. As described above, the decoding apparatus may collectively indicate apparatuses for storing, reproducing, and editing encoded video data, and may include a client connected via a communication channel, an apparatus managing a storage media, a video edition system, a media framework, and the like.
In operation 1830, the multiplexer 1520 adds predetermined syntax to transmission unit data used to multiplex a CRA picture that is an intra picture having leading pictures, according to a result of the determination in operation 1820, wherein the predetermined syntax indicates which request from among a request via the normal reproduction and a request via the random access is related to the CRA picture. As described above, the leading picture means a picture that precedes the CRA picture in a display order but is encoded after the CRA picture in an encoding order. Also, the transmission unit data may be NAL data. Also, the multiplexer 1520 may add an identifier (nal unit type) indicating a type of an NAL unit to a header of the NAL unit so that an NAL unit that is used to multiplex a CRA picture provided according to the request via the normal reproduction may have an identifier (nal unit type) that is different from an identifier (nal unit type) of an NAL unit that is used to multiplex a CRA picture provided according to a request via the random access. Also, the multiplexer 1520 may add a flag to the header of the NAL unit, wherein the flag has a value of 0 or 1 according to the NAL unit used to multiplex the CRA picture provided according to the request via the normal reproduction, and the NAL unit used to multiplex the CRA picture provided according to the request via the random access. Also, the multiplexer 1520 may obtain a count from a PDC that increases by 1 whenever a POC is reset or the CRA picture is encoded while pictures are multiplexed, and may add POC information of a brother picture of the CRA picture, and the count from the PDC to the header of the NAL unit.
Referring to FIG. 19, the video data inverse-multiplexing apparatus 1900 includes a video decoder 1910, an inverse-multiplexer 1920, and a reproduction status identifier 1930.
The inverse-multiplexer 1920 receives transmission unit data, i.e., NAL unit data transmitted from the video data multiplexing apparatus 1500 of FIG. 15, and obtains syntax indicating whether a CRA picture is decoded according to a normal reproduction status or according to a random access status, from the NAL unit data that is used to multiplex the CRA picture.
The reproduction status identifier 1930 determines whether the CRA picture is reproduced according to normal reproduction or according to a random access, by using the obtained syntax.
As described above, when an NAL unit that is used to multiplex a CRA picture provided according to the request via the normal reproduction is set to have an identifier (nal unit type) different from an identifier (nal unit type) of an NAL unit that is used to multiplex a CRA picture provided according to a request via the random access, the reproduction status identifier 1930 may recognize a decoding status of a current CRA picture by referring to values of the identifiers (nal unit type). If a header of the NAL unit has added thereto a flag that has a value of 0 or 1 according to the NAL unit used to multiplex the CRA picture provided according to the request via the normal reproduction, and the NAL unit used to multiplex the CRA picture provided according to the request via the random access, the reproduction status identifier 1930 may recognize the decoding status of the current CRA picture by referring to information about the flag.
Also, when the header of the NAL unit includes a count from a PDC and POC information of a brother picture, the reproduction status identifier 1930 increases the count from the PDC whenever an IDR picture or a CRA picture is decoded while previous pictures are decoded, and determines a match between the count from the PDC that is obtained from the header of the NAL unit at a time of decoding the current CRA picture, and a PDC that counts in a decoding process. Also, the reproduction status identifier 1930 determines a match between a POC value of the brother picture of the CRA picture which is included in the header of the NAL unit, and a POC value of previous pictures stored in a DPB at a time of decoding the current CRA picture. If any one of the count from the PDC or the POC value does not match, the reproduction status identifier 1930 determines that the current CRA picture is reproduced according to the random access, and if both the count from the PDC and the POC value match, the reproduction status identifier 1930 determines that the current CRA picture is reproduced according to the normal reproduction. If the current CRA picture is reproduced according to the random access, it is not necessary to decode leading pictures of the current CRA, so that the reproduction status identifier 1930 notifies the video decoder 1910 that the leading pictures of the current CRA are not required to be decoded.
The video decoder 1910 corresponds to the video decoding apparatus 200 of FIG. 2 or the image decoder 500 of FIG. 5. The video decoder 1910 obtains encoded image data, and split information, partition type information, prediction mode information, transformation unit size information, and parameter set information related to an encoding process, which are about encoding units used to generate the encoded image data, from an NAL unit, and performs decoding.
Referring to FIG. 20, in operation 2010, the inverse-multiplexer 1920 receives transmission unit data used to multiplex a bitstream generated by encoding pictures forming the video data based on hierarchical-structure data units. As described above, the transmission unit data may be NAL unit data.
In operation 2020, the inverse-multiplexer 1920 obtains syntax indicating whether a CRA picture is decoded according to a normal reproduction status or according to a random access status, from NAL unit data that is used to multiplex the CRA picture.
In operation 2030, the reproduction status identifier 1930 identifies whether the CRA picture is reproduced according to normal reproduction or according to a random access, based on the obtained syntax. As described above, when a header of an NAL unit signals a decoding status of the CRA picture by using an identifier (nal unit type), the reproduction status identifier 1930 may recognize a decoding status of a current CRA picture by referring to a value of the identifier (nal unit type). If a flag having a value of 0 or 1 is added to the header of the NAL unit, the reproduction status identifier 1930 may recognize the decoding status of the current CRA picture by referring to information of the flag. Also, when a PDC and POC information of a brother picture are included in the header of the NAL unit, the reproduction status identifier 1930 may recognize the decoding status of the current CRA picture by determining a match between a PDC obtained in a decoding process, and the PDC included in the header of the NAL unit, and a match between a POC value of previous pictures stored in a DPB, and a POC value of the brother picture.
When it is determined that the CRA picture is reproduced according to the random access, leading pictures of the CRA picture are not displayed and thus are not required to be decoded. According to one or more exemplary embodiments, the CRA picture that is reproduced according to the random access may be identified, so that the leading pictures of the CRA picture may not be decoded and thus a system resource of the decoding apparatus may be saved.
One or more exemplary embodiments may also be computer readable codes on a computer readable recording medium. The computer readable recording medium is any data storage device that may store data which may be thereafter read by a computer system. Examples of the computer readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, etc. The computer readable recording medium may also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.
While exemplary embodiments have been described, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the scope of the invention is defined not by the detailed description but by the appended claims, and all differences within the scope will be construed as being included in the present invention.
receiving transmission unit data containing a header;
obtaining, from the header, type information that indicates a type of a current picture contained in the transmission unit data;
identifying whether the current picture is a CRA (Clean Random Access) picture for a random access based on the type information;
determining whether the identified CRA picture is decoded according to normal reproduction or according to a random access, based on a flag of the identified CRA picture; and
decoding the video including the identified CRA picture,
wherein the video includes a leading picture of the current picture that follows the current picture in a decoding order and precedes the current picture in a display order.
wherein the identified CRA picture is split into a plurality of maximum coding units,
wherein one of the plurality of maximum coding units is split into a plurality of coding units by using split information parsed from a bitstream, and
wherein the identified CRA picture is decoded based on the plurality of coding units.
wherein the transmission unit data is NAL (Network Abstraction Layer) unit data that is transmission unit data in a Network Abstraction Layer, and
wherein the type information is NAL unit type information that indicates the type of the current picture contained in the transmission unit data.
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Patent Publication Number: 20140146885
Inventors: Young-o Park (Seoul), Kwang-pyo Choi (Anyang-si), Chan-yul Kim (Seongnam-si), Hee-chul Yang (Suwon-si)
Application Number: 14/130,600
International Classification: H04N 19/70 (20140101); H04N 19/46 (20140101); H04N 19/119 (20140101); H04N 21/426 (20110101); H04N 21/845 (20110101); H04N 21/2387 (20110101); H04N 21/6587 (20110101); H04N 19/107 (20140101); H04N 19/503 (20140101); H04N 19/169 (20140101); H04N 19/426 (20140101);