Method for coding video data, computer system, and computer program

Abstract

A method, a computer program product, and a computer system for coding video data are provided. In one embodiment, video data including one or more sub-pictures is received, a Network Abstraction Layer (NAL) unit type associated with each of the one or more sub-pictures is identified based on checking flags corresponding to mixed NAL units in the one or more sub-pictures, and the video data is decoded based on the identified NAL unit type.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Provisional Patent Application No. 63 / 003137, filed March 31, 2020, and U.S. Patent Application No. 17 / 095289, filed November 11, 2020, in the United States Patent and Trademark Office, which applications are incorporated herein by reference in their entireties.

[0002] [Technical field] FIELD OF THE DISCLOSURE This disclosure relates generally to the field of data processing, and more particularly to video encoding and decoding. [Background technology]

[0003] Video coding and decoding using motion-compensated inter-picture prediction has been known for decades. Uncompressed digital video can consist of a sequence of pictures, each having spatial dimensions of, for example, 1920 x 1080 luminance samples and associated chrominance samples. The sequence of pictures can have a fixed or variable picture rate (commonly known as frame rate), for example, 60 pictures per second, or 60 Hz. Uncompressed video has significant bitrate requirements. For example, 1080p60 4:2:0 video (1920 x 1080 luminance sample resolution at a 60 Hz frame rate) at 8 bits per sample requires a bandwidth approaching 1.5 Gbit / s. One hour of such video requires over 600 GBytes of storage space.

[0004] One goal of video coding and decoding can be the reduction of redundancy in an input video signal through compression. Compression can help reduce the bandwidth or storage space requirements by more than two orders of magnitude in some cases. Both lossless and lossy compression, as well as combinations thereof, can be used. Lossless compression refers to a technique in which an exact copy of the original signal can be reconstructed from the compressed original signal. When lossy compression is used, the reconstructed signal may not be identical to the original signal, but the distortion between the original and reconstructed signal is small enough to make the reconstructed signal useful for the intended application. In the case of video, lossy compression is widely used. The amount of tolerable distortion depends on the application; for example, a user of a particular consumer streaming application may tolerate higher distortion than a user of a television distribution application. The achievable compression ratio can reflect that a higher tolerable / acceptable distortion can result in a higher compression ratio.

[0005] Video encoders and decoders may utilize techniques from several broad categories, including, for example, motion compensation, transforms, quantization, and entropy coding, some of which are introduced below.

[0006] Traditionally, video encoders and decoders have tended to operate with a given picture size that is defined and held constant for a coded video sequence (CVS), group of pictures (GOP), or similar multi-picture time frame. For example, in MPEG-2, system designs are known to vary the horizontal resolution (and thereby the picture size) depending on factors such as scene activity, but only in I-pictures, and thus typically for a GOP. Resampling of reference pictures for use of different resolutions within a CVS is known, for example, from ITU-T Rec. H.263 Annex P. However, here, the picture size remains unchanged; only the reference pictures are resampled, potentially resulting in only a portion of the picture canvas being used (in the case of downsampling) or only a portion of the scene being captured (in the case of upsampling). Furthermore, H.263 Annex Q allows for resampling of individual macroblocks by a factor of two (in each dimension), either upwards or downwards. Again, the picture size remains the same: the macroblock size is fixed in H.263 and does not need to be signaled.

[0007] Picture size changes in predicted pictures are becoming more mainstream in modern video coding. For example, VP9 allows reference picture resampling and changing the resolution of the entire picture. Similarly, some proposals made for VVC (e.g., Hendry, et. al, “On adaptive resolution change (ARC) for VVC,” Joint Video Team document JVET-M0135-v1, January 9-18, 2019, the entire text of which is incorporated herein by reference) allow resampling of the entire reference picture to a different (higher or lower) resolution. In such documents, different candidate resolutions are proposed to be coded in the sequence parameter set and referenced by per-picture syntax elements in the picture parameter set. Summary of the Invention

[0008] Embodiments relate to methods, systems, and computer-readable media for coding video data. According to one aspect, a method for coding video data is provided. The method may include receiving video data including one or more sub-pictures. A network abstraction layer (NAL) unit type associated with each of the one or more sub-pictures is identified based on checking a flag corresponding to a mixed NAL unit in the one or more sub-pictures. The video data is decoded based on the identified NAL unit type.

[0009] According to another aspect, a computer system for coding video data is provided. The computer system may include one or more processors, one or more computer-readable memories, one or more computer-readable tangible storage devices, and program instructions stored in at least one of the one or more storage devices for execution by at least one of the one or more processors via at least one of the one or more memories, thereby enabling the computer system to perform a method. The method may include receiving video data including one or more sub-pictures. A Network Abstraction Layer (NAL) unit type associated with each of the one or more sub-pictures is identified based on checking flags corresponding to mixed NAL units in the one or more sub-pictures. The video data is decoded based on the identified NAL unit type.

[0010] According to yet another aspect, a computer-readable medium for coding video data is provided. The computer-readable medium may include one or more computer-readable storage devices and program instructions stored in at least one of the one or more tangible storage devices, the program instructions being executable by a processor. The program instructions are executed by the processor to perform a method that may accordingly include receiving video data including one or more sub-pictures. A Network Abstraction Layer (NAL) unit type associated with each of the one or more sub-pictures is identified based on checking flags corresponding to mixed NAL units in the one or more sub-pictures. The video data is decoded based on the identified NAL unit type.

[0011] These and other objects, features, and advantages will become apparent from the following detailed description of the invention, which should be read in conjunction with the accompanying drawings. Various features of the drawings are not to scale, and the figures, together with the detailed description, are for the purpose of clarity in facilitating the understanding of those skilled in the art. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of a simplified block diagram of a communication system according to an embodiment. [Figure 2] 1 is a schematic diagram of a simplified block diagram of a communication system according to an embodiment. [Figure 3] FIG. 2 is a schematic block diagram of a decoder according to an embodiment. [Figure 4] FIG. 2 is a schematic block diagram of an encoder according to an embodiment. [Figure 5] 1 is a schematic diagram of options for signaling ARC parameters according to the prior art or embodiments as indicated. [Figure 6] 1 is an example of a syntax table according to an embodiment. [Figure 7] FIG. 1 is a schematic diagram of a computer system according to an embodiment. [Figure 8] 1 is an example of a prediction structure for scalability through adaptive resolution change. [Figure 9] 1 is an example of a syntax table according to an embodiment. [Figure 10] 1 is a schematic block diagram of a POC cycle per access unit and parsing and decoding of an access unit count value; [Figure 11] FIG. 1 is a schematic diagram of a video bitstream structure including multi-layer sub-pictures. [Figure 12] FIG. 10 is a schematic diagram of a display of a selected sub-picture with enhanced resolution. [Figure 13] FIG. 1 is a block diagram of a decoding and display process for a video bitstream containing multi-layer sub-pictures. [Figure 14] 1 is a schematic diagram of a 360-degree video display with a sub-picture enhancement layer. [Figure 15] 1 is an example of layout information for a sub-picture and its corresponding layer and picture prediction structure. [Figure 16]1 is an example of layout information of a sub-picture and its corresponding layer and picture prediction structure with local region spatial scalability modality. [Figure 17] 10 is an example of a syntax table for sub-picture layer information. [Figure 18] 10 is an example of a syntax table of an SEI message for sub-picture layout information. [Figure 19] 10 is an example syntax table showing output layer and profile / tier / level information for each output layer set. [Figure 20] 10 is an example of a syntax table showing output layer mode on for each output layer set. [Figure 21] 10 is an example syntax table showing the current subpicture of each layer for each output layer set. [Figure 22] 10 is an example of a syntax table showing sub-picture identifiers. [Figure 23] 10 is an example of a syntax table showing sub-picture partitioning information. [Figure 24] 1 is an example of a syntax table showing mixed NAL unit types and associated sub-picture partitioning information. DETAILED DESCRIPTION OF THE INVENTION

[0013] Although detailed embodiments of the claimed structures and methods are disclosed herein, it should be understood that the disclosed embodiments are merely exemplary of the claimed structures and methods, which may be embodied in various forms. These structures and methods may, however, be embodied in a wide variety of forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Details of well-known features and techniques may be omitted herein so as not to unnecessarily obscure the presented embodiments.

[0014] As mentioned above, video encoders and decoders have tended in most cases to operate with a given picture size that is defined and held constant for a coded video sequence (CVS). However, a picture may be partitioned into one or more sub-pictures. Each sub-picture may be further partitioned into one or more slices. Two or more independently coded sub-pictures may be merged into a coded picture, decoded by a decoder, and displayed as a single output picture. Therefore, it may be advantageous to specify some encoding or decoding constraints when two or more independently coded pictures are merged into a coded picture.

[0015] Aspects are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer-readable media according to various embodiments. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0016] 1 illustrates a simplified block diagram of a communication system (100) according to an embodiment of the present disclosure. The system (100) may include at least two terminals (110, 120) interconnected via a network (150). For one-way data transmission, a first terminal (110) may code video data at a local location for transmission to another terminal (120) via the network (150). The second terminal (120) may receive the other terminal's encoded video data from the network (150), decode the coded data, and display the recovered video data. One-way data transmission may be common in media serving applications, for example.

[0017] 1 depicts a second pair of terminals (130, 140) equipped to support bidirectional transmission of coded video, such as may occur during a video conference. For bidirectional transmission of data, each terminal (130, 140) may code video data captured at a local location for transmission to the other terminal over the network (150). Each terminal (130, 140) may also receive coded video data transmitted by the other terminal, decode the coded data, and display the recovered video data on a local display device.

[0018] In FIG. 1 , the terminals (110-140) may be represented as servers, personal computers, and smartphones, although the principles of the present disclosure need not be so limited. Embodiments of the present disclosure find application in laptop computers, tablet computers, media players, and / or dedicated videoconferencing devices. The network (150) represents any number of networks that convey coded video data between the terminals (110-140), including, for example, wireline and / or wireless communication networks. The communication network (150) may exchange data over circuit-switched and / or packet-switched channels. Exemplary networks include telecommunications networks, local area networks, wide area networks, and / or the Internet. For purposes of this discussion, the architecture and topology of the network (150) may be irrelevant to the operation of the present disclosure, unless otherwise described hereinafter.

[0019] 2 depicts the placement of a video encoder and decoder in a streaming environment as an example application of the disclosed subject matter, which may be similarly applicable to other video-enabled applications including, for example, video conferencing, digital TV, storage of compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0020] The streaming system may include a video source (201) and a capture subsystem (213) that may include, for example, a digital camera, generating uncompressed video samples. The sample stream (202), represented as a bold line to emphasize its high data volume compared to an encoded video bitstream, may be processed by an encoder (203) coupled to the camera (201). The encoder (203) may include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter, as described in further detail below. The encoded video bitstream (204), represented as a thin line to emphasize its low data volume compared to the sample stream, may be stored on a streaming server (205) for future use. One or more streaming clients (206, 208) may access the streaming server (205) to retrieve a copy of the encoded video bitstream (204). The client (206) can include a video decoder that decodes an incoming copy of the encoded video bitstream (207) and generates an outgoing video sample stream (211) that can be rendered on a display (212) or other rendering device (not shown). In some streaming systems, the video bitstreams (204, 207, 209) can be encoded according to a particular video coding / compression standard. An example of such a standard is ITU-T Recommendation H.265. A video coding standard commonly known as Versatile Video Coding, or VVC, is under development. The disclosed subject matter may be used in conjunction with VVC.

[0021] FIG. 3 may represent a functional block diagram of a video decoder (210) according to an embodiment.

[0022] The receiver (310) may receive one or more coded video sequences to be decoded by the decoder (210), one coded video sequence at a time, in the same or other embodiments. Decoding of each coded video sequence is independent of other coded video sequences. The coded video sequences may be received from a channel (312), which may be a hardware / software link to a storage device that stores the encoded video data. The receiver (310) may receive the encoded video data along with other data, such as coded audio data and / or auxiliary data streams, which may be forwarded to their respective using entities (not shown). The receiver (310) may separate the coded video sequences from other data. To combat network jitter, a buffer memory (315) may be coupled between the receiver (310) and the entropy decoder / parser (320) (hereinafter "parser"). When the receiver 310 is receiving data from a store-and-forward device with sufficient bandwidth and controllability, or from an isosynchronous network, the buffer 315 may not be needed or may be small. For use with best-effort packet networks such as the Internet, the buffer 315 may be needed and can be relatively large and adaptively sized.

[0023] The video decoder (210) may include a parser (320) for reconstructing symbols (321) from the entropy-coded video sequence. These symbol categories include information used to manage the operation of the decoder (210) and, potentially, information for controlling a rendering device, such as a display (212), which is not an internal part of the decoder but may be coupled to the decoder, as depicted in FIG. 3. Control information for the rendering device may take the form of a Supplementary Enhancement Information (SEI) message or a Video Usability Information (VUI) parameter set fragment (not shown). The parser (320) may parse / entropy decode the received coded video sequence. The coding of the coded video sequence may follow a video coding technique or standard and may follow principles well known to those skilled in the art, including variable length coding, Huffman coding, context-dependent or non-context-dependent arithmetic coding, etc. The parser (320) may extract from the coded video sequence a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder based on at least one parameter corresponding to the group. The subgroups may include Groups of Pictures (GOPs), pictures, tiles, slices, macroblocks, coding units (CUs), blocks, transform units (TUs), prediction units (PUs), etc. The entropy decoder / parser may also extract quantization parameter values, motion vectors, etc. from coded video sequence information such as transform coefficients.

[0024] The parser (320) may perform entropy decoding / parsing operations on the video sequence received from the buffer (315) to generate symbols (321).

[0025] The reconstruction of the symbols (321) can have a wide variety of units depending on the type of coded video picture or portion thereof (e.g., inter- and intra-picture, inter- and intra-block) and other factors. Which units are included and how they are included can be controlled by subgroup control information parsed by the parser (320) from the coded video sequence. The flow of such subgroup control information between the parser (320) and the following units is not shown for clarity.

[0026] Beyond the functional blocks already mentioned, decoder 210 may be conceptually subdivided into a number of functional units, which are described below. In an actual implementation operating under commercial constraints, many of these units may interact closely with each other and may be at least partially integrated with each other. However, for purposes of describing the disclosed subject matter, the following conceptual subdivision into functional units is appropriate.

[0027] The first unit is a scalar / inverse transform unit (351), which receives quantized transform coefficients as symbols (321) from the parser (320), along with control information including the transform to use, block size, quantization coefficients, quantization scaling matrix, etc. The scalar / inverse transform unit (351) can output blocks containing sample values ​​that can be input to an aggregator (355).

[0028] In some cases, the output samples of the scaler / inverse transform unit (351) may relate to intra-coded blocks, i.e., blocks that do not use prediction information from a previously reconstructed picture but can use prediction information from a previously reconstructed portion of the current picture. Such prediction information may be provided by an intra-picture prediction unit (352). In some cases, the intra-picture prediction unit (352) generates blocks of the same size and shape as the block being reconstructed using surrounding already reconstructed information fetched from the current (partially reconstructed) picture (358). The aggregator (355), in some cases, adds, on a sample-by-sample basis, the prediction information generated by the intra-prediction unit (352) to the output sample information provided by the scaler / inverse transform unit (351).

[0029] In other cases, the output samples of the scalar / inverse transform unit (351) may relate to an inter-coded, and potentially motion-compensated, block. In such cases, the motion-compensated prediction unit (353) may access a reference picture memory (357) to fetch samples used for prediction. After motion-compensating the fetched samples according to the block-related symbols (321), the samples may be added by an aggregator (355) to the output of the scalar / inverse transform unit (in this case, referred to as a residual sample or residual signal) to generate output sample information. The addresses in the reference picture memory from which the motion-compensated prediction unit fetches prediction samples may be controlled by a motion vector. A motion vector is available to the motion-compensated prediction unit in the form of a symbol (321), which may have, for example, X, Y, and reference picture components. Motion compensation may also include interpolation of sample values ​​fetched from the reference picture memory when sub-sample accurate motion vectors are used, motion vector prediction mechanisms, and the like.

[0030] The output samples of the aggregator (355) can be subjected to various loop filtering techniques in the loop filter unit (356). Video compression techniques can include in-loop filter techniques that are controlled by parameters contained in the coded video bitstream and made available to the loop filter unit (356) as symbols (321) from the parser (320), but can also respond to meta-information obtained during decoding of previous portions (in decoding order) of the coded picture or coded video sequence, and can even respond to previously constructed loop-filtered sample values.

[0031] The output of the loop filter unit (356) can be a sample stream that can be output to a render device (212) and further stored in a reference picture memory (357) for use in future inter-picture prediction.

[0032] Once a particular coded picture is fully reconstructed, it can be used as a reference picture for future prediction. Once a coded picture is fully reconstructed and the coded picture is identified as a reference picture (e.g., by the parser (320)), the current reference picture (358) can become part of the reference picture memory (357), and any unused current picture memory can be reallocated before beginning reconstruction of a subsequent coded picture.

[0033] The video decoder (210) may perform decoding operations according to a predetermined video compression technology, which may be documented in a standard such as ITU-T Rec. H.265. A coded video sequence may conform to the syntax prescribed by the video compression technology or standard in use, in the sense that it conforms to the syntax of the video compression technology or standard as defined in the video compression technology document or standard, specifically in a profile document therein. Compliance also requires that the complexity of the coded video sequence be within the boundaries defined by the level of the video compression technology or standard. In some cases, the level limits the maximum picture size, maximum frame rate, maximum reconstruction sample rate (e.g., measured in megasamples per second), maximum reference picture size, etc. The limits set by the level may, in some cases, be further constrained through a Hypothetical Reference Decoder (HRD) specification and metadata for HRD buffer management signaled in the coded video sequence.

[0034] In embodiments, the receiver (310) may receive additional (redundant) data along with the encoded video. The additional data may also be included as part of the coded video sequence. The additional data may be used by the video decoder (210) to properly decode the data and / or to more accurately reconstruct the original video data. The additional data may take the form of, for example, temporal, spatial, or SNR enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0035] FIG. 4 may be a functional block diagram of a video encoder (203) according to an embodiment of the present disclosure.

[0036] The encoder (203) may receive video samples from a video source (201) (not part of the encoder) that may capture video images to be coded by the encoder (203).

[0037] The video source (201) may provide a source video sequence to be coded by the encoder (203) in the form of a digital video sample stream, which can be of any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, etc.), any color space (e.g., BT.601 YCrCB, RGB, etc.), and any suitable sampling structure (e.g., YCrCb 4:2:0, YCrCb 4:4:4). In a media serving system, the video source (201) may be a storage device storing previously prepared video. In a video conferencing system, the video source (201) may be a camera capturing local image information as a video sequence. The video data may be provided as multiple individual pictures that, when viewed in sequence, impart motion. The pictures themselves may be organized as a spatial array of pixels, each of which may have one or more samples depending on the sampling structure, color space, etc., in use. Those skilled in the art will readily understand the relationship between pixels and samples. This specification will focus on samples hereafter.

[0038] According to an embodiment, the encoder (203) may code and compress pictures of a source video sequence into a coded video sequence (443) in real time or under any other time constraints required by the application. Imposing an appropriate coding rate is one function of the controller (450). The controller may also control and be operatively coupled to other functional units, as described below. Coupling is not shown for clarity. Parameters set by the controller may include parameters related to rate control (picture skip, quantizer, lambda value for rate-distortion optimization techniques, etc.), picture size, group-of-picture (GOP) layout, maximum motion vector search range, etc. Those skilled in the art will readily identify other functions of the controller (450) as they may be relevant to optimizing the video encoder (203) for a particular system design.

[0039] Some video encoders operate in what those skilled in the art readily realize as a "coding loop." As an overly simplified description, the coding loop can consist of an encoding portion of an encoder (430) (hereinafter "source coder") (responsible for generating symbols based on an input picture to be coded and reference pictures), and a (local) decoder (433) embedded in the encoder (203) that reconstructs the symbols to generate sample data that a (remote) decoder will also generate (when any compression between the symbols and the coded video bitstream is lossless with the video compression techniques contemplated in the disclosed subject matter). That reconstructed sample stream is input to a reference picture memory (434). Because decoding of the symbol stream yields bit-exact results independent of the location (local or remote) of the decoder, the contents of the reference picture memory are also bit-perfect between the local and remote encoders. That is, the prediction part of the encoder "sees" as reference picture samples exactly the same sample values ​​that the decoder will "see" when using the prediction during decoding. This basic principle of reference picture synchronicity (and the resulting drift when synchronicity cannot be maintained, e.g., due to channel errors) is well known to those skilled in the art.

[0040] The operation of the "local" decoder (433) can be the same as the "remote" decoder (210), already described in detail above in conjunction with Figure 3. Referring also briefly to Figure 3, however, because symbols are available and the decoding of the symbols into a coded video sequence by the entropy coder (445) and parser (320) can be lossless, the entropy decoding portion of the decoder (210), including the channel (312), receiver (310), buffer (315), and parser (320), need not be fully implemented in the local decoder (433).

[0041] An observation that can be made at this point is that any decoder technique, with the exception of parsing / entropy decoding, that is present in the decoder must necessarily be present in substantially the same functional form in the corresponding encoder. For this reason, the disclosed subject matter focuses on the operation of the decoder. A description of the encoder techniques can be omitted, as they are the inverse of the decoder techniques that are generically described. Only to certain extents is a more detailed description required, and is provided below.

[0042] As part of its operation, the source coder (430) may perform motion-compensated predictive coding, which predictively codes an input picture with reference to one or more previously coded frames from the video sequence designated as "reference pictures." In this manner, the coding engine (432) codes differences between pixel blocks of the input picture and pixel blocks of the reference pictures that may be selected as predictive references for the input picture.

[0043] The local video decoder (433) may decode coded video data of frames that may be designated as reference frames based on symbols generated by the source coder (430). The operation of the coding engine (432) may advantageously be a lossy process. When the coded video data is decoded by a video decoder (not shown in FIG. 4), the reconstructed video sequence may typically be a copy of the source video sequence, with some errors. The local video decoder (433) may replicate the decoding process that may be performed by the video decoder on the reference frames, causing the reconstructed reference frames to be stored in a reference picture cache (434). In this way, the encoder (203) may locally store copies of reconstructed reference frames that have content in common with reconstructed reference frames that would be obtained by a far-end video decoder (without transmission errors).

[0044] The predictor (435) may perform the prediction search of the coding engine (432). That is, for a new picture to be coded, the predictor (435) may search the reference picture memory (434) for specific metadata, such as reference picture motion vectors, block shapes, or sample data (as candidate reference pixel blocks) that can serve as suitable prediction references for the new picture. The predictor (435) may operate on a sample block-by-pixel block basis to find suitable prediction references. In some cases, as determined by the search results obtained by the predictor (435), the input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory (434).

[0045] The controller (450) may manage the coding operations of the video coder (430), including, for example, setting the parameters and subgroup parameters used to encode the video data.

[0046] The output of all of the above functional units may undergo entropy coding in an entropy coder (445), which converts the symbols produced by the various functional units into a coded video sequence by losslessly compressing the symbols according to techniques known to those skilled in the art, such as Huffman coding, variable length coding, arithmetic coding, etc.

[0047] The transmitter (440) may buffer the coded video sequence produced by the entropy coder (445) to prepare it for transmission over a communication channel (460), which may be a hardware / software link to a storage device that stores the encoded video data. The transmitter (440) may merge the coded video data from the video coder (430) with other data to be transmitted, such as coded audio data and / or auxiliary data streams (sources not shown).

[0048] A controller (450) may manage the operation of the encoder (203). During coding, the controller (450) may assign a particular coded picture type to each coded picture, which may affect the coding technique that may be applied to each picture. For example, pictures may often be assigned as one of the following frame types:

[0049] An Intra Picture (I-picture) may be a picture that can be coded and decoded without using any other picture in the sequence as a source of prediction. Some video codecs allow various types of Intra pictures, including, for example, Independent Decoder Refresh (IDR) pictures. Those skilled in the art are aware of such variations of I-pictures and their respective applications and characteristics.

[0050] A Predictive Picture (P-picture) may be a picture that can be coded and decoded by intra-prediction or inter-prediction using at most one motion vector and reference index to predict the sample values ​​of each block.

[0051] A Bi-directionally Predictive Picture (B-picture) may be a picture that can be coded and decoded by intra- or inter-prediction using at most two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multiple-predictive pictures can use more than two reference pictures and associated metadata for the reconstruction of a single block.

[0052] A source picture is generally spatially subdivided into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples, respectively) and may be coded block by block. Blocks may be predictively coded with reference to other (already coded) blocks as determined by the coding assignment applied to each picture of the blocks. For example, blocks of an I-picture may be coded non-predictively, or they may be predictively coded with reference to already coded blocks of the same picture (spatial prediction or intra-prediction). Pixel blocks of a P-picture may be coded non-predictively, or with spatial prediction or temporal prediction with reference to one previously coded reference picture. Blocks of a B-picture may be coded non-predictively, or with spatial prediction or temporal prediction with reference to one or two previously coded reference pictures.

[0053] The video coder (203) may perform coding operations according to a predetermined video coding technique or standard, such as ITU-T Rec. H.265. During its operation, the video coder (203) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancy in the input video sequence. Thus, the coded video data may conform to a syntax defined by the video coding technique or standard being used.

[0054] In embodiments, the transmitter (440) may transmit additional data along with the encoded video. The video coder (430) may include such data as part of the coded video sequence. The additional data may include temporal / spatial / SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, SEI messages, VUI parameter set fragments, etc.

[0055] Before describing in further detail certain aspects of the disclosed embodiments, a few items will be introduced which will be referenced in the remainder of the specification.

[0056] Hereinafter, a subpicture refers to a rectangular arrangement of samples, blocks, macroblocks, coding units, or similar entities that, in some cases, are semantically grouped and may be coded independently at a changed resolution. One or more subpictures may form a picture. One or more coded subpictures may form a coded picture. One or more subpictures may be combined into a picture, and one or more subpictures may be extracted from a picture. In certain circumstances, one or more coded subpictures may be combined into a picture coded in the compressed domain without transcoding to the same level, and in the same or other cases, one or more coded subpictures may be extracted from a subpicture coded in the compressed domain.

[0057] Hereinafter, Adaptive Resolution Change (ARC) refers to a mechanism that enables changing the resolution of pictures or sub-pictures within a coded video sequence, for example, by reference picture resampling. ARC parameters hereafter refer to the control information needed to perform adaptive resolution change and may include, for example, filter parameters, scaling factors, output and / or reference picture resolutions, various control flags, etc.

[0058] The above description has focused on the coding and decoding of a single, semantically independent coded video picture. Before describing the implications of coding / decoding multiple sub-pictures with independent ARC parameters and the additional complexity that it implies, options for signaling the ARC parameters should be explained.

[0059] Referring to Figure 5, several novel options for signaling ARC parameters are shown. As described by each of the options, they have certain advantages and disadvantages from a coding efficiency, complexity, and architecture perspective. A video coding standard or technology may select one or more of these options, or options known from the prior art, for signaling ARC parameters. The options may not be mutually exclusive and may conceivably be interchanged based on application needs, related standard technology, or encoder preference.

[0060] Categories of ARC parameters may include:

[0061] Separate or combined upsample and / or downsample factors in the X and Y dimensions

[0062] Upsampling and / or downsampling factors with an added time dimension to indicate constant speed zooming in / out for a given number of pictures

[0063] Either of the above two may involve coding one or more, possibly short, syntax elements that may point to a table containing the coefficients.

[0064] Resolution in the X or Y dimension, in combination or separately, of input picture, output picture, reference picture, coded picture sample, block, macroblock, CU, or any other suitable unit of granularity. When there is more than one resolution (e.g., one for the input picture and one for the reference picture), one set of values ​​may be inferred from the other set of values ​​in certain cases. Resolution may be gated, for example, by use of a flag. See below for more detailed examples.

[0065] "Warping" coordinates, similar to those used in H.263 Annex P, again at the appropriate granularity described above. H.263 Annex P defines one efficient way to code such warping coordinates, but other, potentially more efficient ways may conceivably be devised. For example, the variable-length reversible "Huffman"-style coding of Annex P warping coordinates may be replaced by appropriate-length binary coding, where the length of the binary codewords may be derived, for example, from the maximum picture size, possibly multiplied by a specific factor and offset by a specific value to allow "warping" outside the boundaries of the maximum picture size.

[0066] Upsample and / or downsample filter parameters. In the easiest case, there may be only a single filter for upsampling and / or downsampling. However, in certain cases, it may be advantageous to allow more flexibility in the filter design, which may require signaling of filter parameters. Such parameters may be selected by an index in a list of possible filter designs, the filter may be fully specified (e.g., through a list of filter coefficients using an appropriate entropy coding technique), or the filter may be selected implicitly by an upsample and / or downsample ratio signaled according to any of the mechanisms described above, etc.

[0067] Hereafter, the description assumes the coding of a finite set of upsample and / or downsample coefficients indicated by a codeword, where the same coefficients are used in both the X and Y dimensions. The codeword may advantageously be variable length coded, for example, by using Ext-Golomb codes common to certain syntax elements in video coding standards such as H.264 and H.265. One suitable mapping of values ​​to upsample and / or downsample coefficients may, for example, follow the table below: [Table 1]

[0068] Many similar mappings could be devised according to the needs and capabilities of the application of up- and down-scaling mechanisms available in video compression technologies or standards. The table may be extended to more values. The values ​​may also be represented by entropy coding mechanisms other than Ext-Golomb codes, for example, using binary coding. This may have particular advantages when the resampling factor is significant outside the video processing engines (primarily the encoder and decoder) themselves, for example, by MANE. It should be noted that for the (presumably) most common case where no resolution change is required, a short (e.g., only a single bit in the above table) Ext-Golomb code can be selected, which may be more coding efficient than using a binary code for the most common case.

[0069] The number of entries in the table and their semantics may be fully or partially configurable. For example, a basic outline of the table may be conveyed in a "high" parameter set, such as a sequence or decoder parameter set. Alternatively, or additionally, one or more such tables may be defined in a video coding technology or standard and may be selected, for example, by a decoder or sequence parameter set.

[0070] The following describes how the upsample and / or downsample coefficients (ARC information) coded as described above can be included in a video coding technique or standard syntax. Similar considerations apply to one or several codewords that control the upsample and / or downsample filters. See below for a discussion of when a relatively large amount of data may be required for a filter or other data structure.

[0071] H.263 Annex P includes ARC information (502) in the form of four warping coordinates within the picture header (501), specifically in the H.263 PLUSPTYPE (503) header extension. This can be a reasonable design choice when (a) there is a picture header available and (b) frequent changes in ARC information are expected. However, the overhead when using H.263-style signaling can be quite high, and scaling factors may not adhere to picture boundaries due to the potentially transient nature of picture headers.

[0072] The above JVCET-M135-v1 includes ARC reference information (505) (index) located in a picture parameter set (504) that indexes a table (506) containing target resolutions located in a sequence parameter set (507). The placement of possible resolutions in the table (506) in the sequence parameter set (507) can be justified, according to verbal statements by the authors, by using the SPS (507) as an interoperability negotiation point during capability exchange. Resolution can be varied within the limits set by the values ​​in the table (506) for each picture by referencing the appropriate picture parameter set (504).

[0073] Still referring to Figure 5, the following additional options may exist for carrying ARC information in the video bitstream: Each of these options has certain advantages over the existing techniques described above. Options may exist simultaneously within the same video coding technology or standard.

[0074] In embodiments, ARC information (509), such as a resampling (zoom) factor, may be present in a slice header, a GOB header, a tile header, or a tile group header (hereafter, tile group header) (508). This may be appropriate when the ARC information is small, such as a single variable-length ue(v) or fixed-length codeword of a few bits, as described above. Having the ARC information directly in the tile group header has the additional advantage that the ARC information may be applicable, for example, to the sub-picture represented by that tile group, rather than to the entire picture. See also below. Furthermore, even if a video compression technology or standard contemplates resolution changes that are only applicable to the entire picture (as opposed to, for example, tile-group-based adaptive resolution changes), placing the ARC information in the tile group header, as opposed to placing it in an H263-style picture header, has certain advantages from an error resilience perspective.

[0075] In the same or other embodiments, the ARC information (512) itself may reside in an appropriate parameter set (511) (depicted as an adaptive parameter set), such as, for example, a picture parameter set, a header parameter set, a tile parameter set, an adaptive parameter set, etc. The scope of that parameter set may advantageously be no larger than a picture, for example, a tile group. The use of the ARC information may be implicit through activation of an associated parameter set. For example, if a video coding technology or standard contemplates only picture-based ARC, a picture parameter set or equivalent may be appropriate.

[0076] In the same or other embodiments, the ARC reference information (513) may reside in a tile group header (514) or similar data structure, and may reference a subset of the ARC information (515) available in a parameter set (516) with a scope beyond a single picture, such as a sequence parameter set or a decoder parameter set.

[0077] The additional level of indirect implicit activation of PPS from the tile group header, PPS, and SPS used in JVET-M0135-v1 seems unnecessary, given that picture parameter sets, like sequence parameter sets, can be used for capability negotiation or announcement (as used in certain standards such as RFC3984). However, if the ARC information should be applicable to, for example, subpictures also represented by tile groups, a parameter set with activation scope limited to the tile group, such as an adaptive parameter set or a header parameter set, may be a better choice. Also, if the ARC information is larger than negligible size and contains filter control information, such as a large number of filter coefficients, parameters may be better from the perspective of coding efficiency than using the header (508) directly, since such settings can be reused by future pictures or subpictures by referencing the same parameter set.

[0078] When using sequence parameter sets or other higher parameter sets with scope spanning multiple pictures, certain considerations may apply.

[0079] 1. The parameter set holding the ARC information table (516) can in some cases be a sequence parameter set, but in other cases, advantageously, can be a decoder parameter set. The decoder parameter set can have activation ranges for multiple CVSs (i.e., coded video streams), i.e., all coded video bits from session start to session teardown. Such a range may be more appropriate because possible ARC factors may be decoder mechanisms, possibly implemented in hardware, and hardware mechanisms tend not to change with any CVS (which, at least in some entertainment systems, is a sub-second group of pictures). That said, placing the table in a sequence parameter is explicitly included in the deployment options described herein, particularly in connection with 2. below.

[0080] 2. The ARC reference information (513) may advantageously be placed directly in the picture / slice / tile / GOB / tile group header (hereafter referred to as the tile group header) (514) rather than in the picture parameter set as in JVCET-M0135-v1. The reason for this is as follows: if an encoder wants to change a single value in a picture parameter set, e.g., the ARC reference information, it should generate a new PPS and reference that new PPS. Assume that only the ARC reference information changes, and other information, e.g., the quantization matrix information in the PPS, remains the same. Such information can be quite large and needs to be retransmitted to complete the new PPS. Since the ARC reference information can be a single codeword that is the only value that changes, such as an index into a table (513), retransmitting all of the information, e.g., the quantization matrix information, would be cumbersome and wasteful. Avoiding indirect referencing through the PPS, as proposed so far in JVET-M0135-v1, may be significantly better in terms of coding efficiency. Similarly, placing the ARC reference information in the PPS has the further disadvantage that the ARC information referenced by the ARC reference information (513) must be applied unnecessarily to the entire picture and not to the sub-picture, since the activation scope of the picture parameter set is the picture.

[0081] In the same or other embodiments, the signaling of ARC parameters may follow the detailed example illustrated in Figure 6. Figure 6 depicts a syntax diagram in the representation used in video coding standards since at least 1993. The notation of such syntax diagrams roughly follows C programming. Bolded lines indicate syntax elements present in the bitstream, while non-bolded lines often indicate control flow or variable settings.

[0082] The tile group header (601), an example syntax structure for a header applicable to a (possibly rectangular) portion of a picture, can conditionally contain the variable-length Exp-Golomb coded syntax element dec_pic_size_idx (602) (shown in bold). The presence of this syntax element in the tile group header can be gated on the use of adaptive resolution (603). Here, the flag value is not shown in bold, which means that the flag is present in the bitstream at the time it occurs in the syntax diagram. Whether adaptive resolution is in use for this picture or its portion can be signaled in any higher-level syntax structure within or outside the bitstream. In the example shown, adaptive resolution is signaled in the sequence parameter set, as described below.

[0083] Still referring to Figure 6, an excerpt of a sequence parameter set (610) is also shown. The first syntax element shown is adaptive_pic_resolution_change_flag (611). If true, that flag may indicate the use of adaptive resolution, which in turn may require specific control information. In the example, such control information is conditionally present based on the value of the flag based on an if() statement in the parameter set (612) and the tile group header (600).

[0084] When adaptive resolution is in use, the output resolution is coded in units of samples (613), in this example. The number 613 refers to both output_pic_width_in_luma_samples and output_pic_height_in_luma_samples, which together can define the resolution of the output picture. Specific restrictions on either value may be defined elsewhere in the video coding technology or standard. For example, a level definition may limit the total number of output samples that can be the product of the values ​​of those two syntax elements. Also, a particular video coding technology or standard, or an external technology or standard such as a system standard, may limit the numbering range (e.g., one or both dimensions should be divisible by a power of 2) or the aspect ratio (e.g., width and height must have a relationship such as 4:3 or 16:9). Such restrictions may be introduced to facilitate hardware implementation or for other reasons and are well known in the art.

[0085] In certain applications, it may be wise for an encoder to instruct a decoder to use a particular picture size rather than implicitly assuming that size to be the output picture size. In this example, the syntax element reference_pic_size_present_flag (614) gates the conditional presence of the reference picture dimensions (615) (again, the numbers refer to both width and height).

[0086] Finally, a table of possible decoded picture widths and heights is shown. Such a table can be represented, for example, by a table directive (num_dec_pic_size_in_luma_samples_minus1) (616). "minus1" can refer to the interpretation of the value of that syntax element. For example, if the coded value of the syntax element is 0, there is one table entry. If the coded value is 5, there are six table entries. For each "row" of the table, the decoded picture width and height are then included in the syntax (617).

[0087] The represented table entry (617) can be indexed using the syntax element dec_pic_size_idx (602) in the tile group header, thereby allowing different decoding sizes, in effect zoom factors, per tile group.

[0088] Certain video coding techniques or standards, e.g., VP9, ​​support spatial scalability by implementing a particular form of reference picture resampling (signaled entirely separately from the disclosed subject matter) along with temporal scalability to enable spatial scalability. In particular, certain reference pictures may be upsampled to higher resolutions using ARC-style techniques to form the basis of spatial enhancement layers. These upsampled pictures may then be refined using normal prediction mechanisms at the higher resolutions to add detail.

[0089] The disclosed subject matter can be used in such environments. In certain cases, in the same or other embodiments, values ​​in NAL unit headers, e.g., in a Temporal ID field, can be used to indicate not only temporal layers but also spatial layers. Doing so has certain advantages for certain system designs. For example, existing Selected Forwarding Units (SFUs) that are generated and optimized for temporal layer selective forwarding based on the Temporal ID value in the NAL unit header can be used without modification for scalable environments. To make that possible, the mapping between coded pictures and temporal layers needs to be indicated by the Temporal ID field in the NAL unit header.

[0090] In some video coding techniques, an Access Unit (AU) can refer to a coded picture, slice, tile, NAL unit, etc. captured at a given point in time and organized into a respective picture / slice / tile / NAL unit bitstream. Such a point in time can be composition time.

[0091] In HEVC and certain other video coding technologies, a Picture Order Count (POC) value may be used to indicate a reference picture selected from multiple reference pictures stored in a Decoded Picture Buffer (DPB). When an access unit (AU) includes one or more pictures, slices, or tiles, each picture, slice, or tile belonging to the same AU may carry the same POC value, from which it can be derived that they were generated from content with the same composition time. That is, in a scenario where two pictures / slices / tiles carry the same given POC value, it can be determined that the two pictures / slices / tiles belong to the same AU and have the same composition time. In contrast, two pictures / tiles / slices with different POC values ​​may indicate that the pictures / slices / tiles belong to different AUs and have different composition times.

[0092] In embodiments of the disclosed subject matter, the above rigid relationship may be relaxed in that an access unit may contain pictures, slices, or tiles with different POC values. By allowing different POC values ​​within an AU, it becomes possible to use the POC values ​​to identify potentially independently decodable pictures / slices / tiles that have the same presentation time. This, in turn, may enable support for multiple scalable layers without changes to reference picture selection signaling (e.g., reference picture set signaling or reference picture list signaling), as described in more detail below.

[0093] However, it is still desirable to be able to identify the AU to which a picture / slice / tile belongs, relative to other pictures / slices / tiles with different POC values, from the POC value alone. This can be achieved as described below.

[0094] In the same or other embodiments, an Access Unit Count (AUC) may be signaled in a high-level syntax structure such as a NAL unit header, a slice header, a tile group header, an SEI message, a parameter set, or an AU delimiter. The value of AUC may be used to identify which NAL unit, picture, slice, or tile belongs to a given AU. The value of AUC may correspond to a distinct compositing time instance. The AUC value is equal to a multiple of the POC value. The AUC value can be calculated by dividing the POC value by an integer value. In certain cases, the division may impose a certain burden on the decoder implementation. In such cases, a small limitation in the numbering space of AUC values ​​may allow for the replacement of the division by a shift operation. For example, the AUC value is equal to the most significant bit (MSB) value of the POC value range.

[0095] In the same embodiment, the value of the POC cycle per AU (poc_cycle_au) may be signaled in a higher-level syntax structure, such as a NAL unit header, a slice header, a tile group header, an SEI message, a parameter set, or an AU delimiter. poc_cycle_au may indicate how multiple different consecutive POC values ​​can be associated with the same AU. For example, if the value of poc_cycle_au is equal to 4, pictures, slices, or tiles with POC values ​​greater than or equal to 0 and less than or equal to 3 are associated with AUs with AUC values ​​equal to 0, and pictures, slices, or tiles with POC values ​​greater than or equal to 4 and less than or equal to 7 are associated with AUs with AUC values ​​equal to 1. Thus, the value of AUC can be inferred by dividing the POC value by poc_cycle_au.

[0096] In the same or other embodiments, the value of poc_cycle_au may be derived from information located, for example, in a video parameter set (VPS) that identifies the number of spatial or SNR layers in the coded video sequence. Such possible relationships are briefly described below. While the above-described derivation may save a few bits in the VPS and thus improve coding efficiency, it may be advantageous to explicitly code poc_cycle_au in an appropriate higher-level syntax structure hierarchically below the video parameter set in order to be able to minimize poc_cycle_au for a given small portion of the bitstream, such as a picture. This optimization may save more bits than would be possible through the above derivation process, since the POC value (and / or the values ​​of syntax elements that indirectly reference POC) may be coded in a lower-level syntax structure.

[0097] The techniques for signaling adaptive resolution parameters described above can be implemented as computer software using computer-readable instructions and physically stored on one or more computer-readable media. For example, Figure 7 illustrates a computer system 700 suitable for implementing certain embodiments of the disclosed subject matter.

[0098] Computer software can be coded in any suitable machine code or computer language that can be subjected to mechanisms such as assembly, compilation, linking, etc. to produce code containing instructions that can be executed by a central processing unit (CPU), graphics processing unit (GPU), etc. directly or through interpretation, microcode execution, etc.

[0099] The instructions may be executable by various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smartphones, gaming consoles, devices for the Internet of Things, and the like.

[0100] 7 for computer system 700 are exemplary in nature and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing embodiments of the present disclosure. The arrangement of components should not be interpreted as having any dependency or requirement regarding any one or combination of components illustrated in the exemplary embodiment of computer system 700.

[0101] The computer system 700 may include certain human interface input devices. Such human interface input devices may respond to input by one or more users through, for example, tactile input (e.g., keyboard, swipe, data glove movement), audio input (e.g., voice, claps), visual input (e.g., gestures), and olfactory input (not shown). The human interface devices may also be used to capture certain media that are not necessarily directly related to conscious human input, such as audio (e.g., speech, music, ambient sounds), images (e.g., scanned images, photographic images obtained from a still camera), and video (e.g., two-dimensional video, three-dimensional video, including stereoscopic video).

[0102] The input human interface devices may include one or more of the following (only one of each is shown): a keyboard 701, a mouse 702, a trackpad 703, a touchscreen 710, a data glove 704, a joystick 705, a microphone 706, a scanner 707, and a camera 708.

[0103] The computer system 700 may also include certain human interface output devices. Such human interface output devices may stimulate one or more of the user's senses through, for example, tactile output, sound, light, and smell / taste. Such human interface output devices may include haptic output devices (e.g., haptic feedback via a touchscreen 710, data gloves 704, or joystick 705; however, haptic feedback devices that do not function as input devices may also be present), audio output devices (e.g., speakers 709, headphones (not shown)), visual output devices (e.g., screen 710, including CRT screens, LCD screens, plasma screens, and OLED screens, each with or without touchscreen input capability, each with or without haptic feedback capability, some of which may provide two-dimensional visual output or output in more than three dimensions, such as by means of stereoscopic output, virtual reality glasses (not shown), holographic displays, and smoke tanks (not shown)), and printers (not shown).

[0104] The computer system 700 may also include human-accessible storage devices and their associated media, such as CD / DVD ROM / RW 720 along with CD / DVD or similar media 721, thumb drives 722, removable hard disk or solid state drives 723, legacy magnetic media such as tape and floppy disks (not shown), dedicated ROM / ASIC / PLD-based devices such as security dongles (not shown), and the like.

[0105] Those skilled in the art will also understand that the term "computer-readable medium" as used in connection with the presently disclosed subject matter does not include transmission media, carrier waves, or other transitory signals.

[0106] The computer system 700 may also include interfaces to one or more communications networks. Networks may be, for example, wireless, wireline, or optical. Networks may further be local, wide-area, metropolitan, vehicular, and industrial, real-time, delay-tolerant, and the like. Examples of networks include local area networks such as Ethernet; wireless LANs; cellular networks including GSM, 3G, 4G, 5G, LTE, and the like; TV wireline or wireless wide-area digital networks including cable TV, satellite TV, and terrestrial broadcast TV; and vehicle and factory networks including CAN bus. Certain networks generally require an external network interface adapter attached to a particular general-purpose data port or peripheral bus (749) (e.g., a USB port on the computer system 700). Others are generally built into the core of the computer system 700 by attachment to a system bus as described below (e.g., an Ethernet network interface to a PC computer system or a cellular network interface to a smartphone computer system). Using any of these networks, the computer system 700 can communicate with other entities. Such communication may be one-way receive-only (e.g., broadcast TV) or one-way transmit-only (e.g., a CAN bus to a particular CAN bus device), or may be two-way to other computer systems, for example, using local or wide area digital networks. Specific protocols or protocol stacks may be used with each of the networks and network interfaces described above.

[0107] The above-mentioned human interface devices, human-accessible storage devices, and network interfaces may be attached to the core 740 of the computer system 700 .

[0108] The core 740 may include one or more central processing units (CPUs) 741, graphics processing units (GPUs) 742, dedicated programmable processing units in the form of field programmable gate arrays (FPGAs) 743, hardware accelerators 744 for specific tasks, etc. These devices may be connected through a system bus 748, along with read-only memory (ROM) 745, random access memory (RAM) 746, internal mass storage such as an internal non-user-accessible hard drive, SSD, etc. 747. In some computer systems, the system bus 748 may be accessible in the form of one or more physical plugs to allow expansion with additional CPUs, GPUs, etc. Peripheral devices may be attached directly to the core's system bus 748 or through a peripheral bus 749. Architectures for peripheral buses include PCI, USB, etc.

[0109] The CPU 741, GPU 742, FPGA 743, and accelerator 744 can execute specific instructions that, in combination, can constitute the above-mentioned computer code. The computer code can be stored in ROM 745 or RAM 746. Temporary data can also be stored in RAM 746, while persistent data can be stored, for example, in an internal mass storage device 747. Fast storage and retrieval from any of the memory devices can be enabled through the use of cache memory. The cache memory can be closely associated with one or more of the CPU 741, GPU 742, mass storage device 747, ROM 745, RAM 746, etc.

[0110] The computer-readable medium can carry computer code for performing various computer-implemented operations. The medium and computer code can be those specially designed and constructed for the purposes of the present disclosure, or they can be of the kind well known and available to those of ordinary skill in the computer software arts.

[0111] By way of example, and not limitation, a computer system having architecture 700, and specifically core 740, can provide functionality as a result of a processor (including a CPU, GPU, FPGA, accelerator, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media can be media associated with the user-accessible mass storage devices introduced above, in addition to specific storage of core 740 that is non-transitory in nature, such as core internal mass storage 747 or ROM 745. Software implementing various embodiments of the present disclosure can be stored on such devices and executable by core 740. Computer-readable media can include one or more memory devices or chips, depending on particular needs. The software can cause core 740, and specifically the processor therein (including a CPU, GPU, FPGA, etc.), to perform particular processes or particular portions of particular processes described herein, including defining data structures stored in RAM 746 and modifying such data structures according to software-defined processes. Additionally, or alternatively, a computer system may provide functionality as a result of logic (e.g., accelerator 744) implemented by hardware or otherwise embodied in circuitry that can operate in place of or in conjunction with software to perform particular processes or portions of particular processes described herein. References to software can encompass logic, where appropriate, and vice versa. References to computer-readable media can encompass circuitry (e.g., integrated circuits (ICs)) storing software for execution, circuitry embodying logic for execution, or both, where appropriate. The present disclosure encompasses any suitable combination of hardware and software.

[0112] 8 shows an example of a video sequence structure with a combination of temporal_id, layer_id, and POC and AUC values ​​with adaptive resolution change. In this example, a picture, slice, or tile in the first AU with AUC=0 may have temporal_id=0 and layer_id=0 or 1, while a picture, slice, or tile in the second AU with AUC=1 may have temporal_id=1 and layer_id=0 or 1, respectively. The value of POC increases by 1 for each picture regardless of the values ​​of temporal_id and layer_id. In this example, the value of poc_cycle_au is equal to 2. Preferably, the value of poc_cycle_au may be set equal to the number of (spatial scalability) layers. Therefore, in this example, the value of POC increases by 2, while the value of AUC increases by 1.

[0113] In the above embodiments, all or a subset of the inter-picture or inter-layer prediction structure and reference picture indication may be supported by using the existing reference picture set (RPS) signaling or reference picture list (RPL) signaling in HEVC. In the RPS or RPL, the selected reference picture may be indicated by signaling the value of POC or the difference value of POC between the current picture and the selected reference picture. For the disclosed subject matter, the RPS or RPL may be used to indicate the inter-picture or inter-layer prediction structure without any signaling changes, but with the following restrictions: If the value of the temporal_id of a reference picture is greater than the value of the temporal_id of the current picture, the current picture may not use the reference picture for motion compensation or other prediction. If the value of the layer_id of a reference picture is greater than the value of the layer_id of the current picture, the current picture may not use the reference picture for motion compensation or other prediction.

[0114] In the same or other embodiments, motion vector scaling based on POC difference for temporal motion vector prediction may be disabled across multiple pictures within an access unit. Thus, even though each picture may have a different POC value within the access unit, motion vectors are not scaled and used for temporal motion vector prediction within the access unit. This is because reference pictures with different POCs in the same AU are considered to be reference pictures with the same time instance. Thus, in an embodiment, the motion vector scaling function may return 1 if the reference picture belongs to the AU associated with the current picture.

[0115] In the same or other embodiments, motion vector scaling based on POC difference for temporal motion vector prediction may be optionally disabled across multiple pictures if the spatial resolution of the reference picture differs from the spatial resolution of the current picture. When motion vector scaling is allowed, the motion vector is scaled based on both the POC difference and the spatial resolution ratio between the current picture and the reference picture.

[0116] In the same or other embodiments, motion vectors may be scaled based on AUC differential instead of POC differential for temporal motion vector prediction, especially when poc_cycle_au has a non-uniform value (when vps_contant_poc_cycle_per_au==0), otherwise (when vps_contant_poc_cycle_per_au==1), motion vector scaling based on AUC differential may be the same as motion vector scaling based on POC differential.

[0117] In the same or other embodiments, when a motion vector is scaled based on an AUC difference, a reference motion vector (having the same AUC value) within the same AU containing the current picture is not scaled based on the AUC difference and is used for motion vector prediction with or without scaling based on the spatial resolution ratio between the current picture and the reference picture.

[0118] In the same or other embodiments, the AUC value is used to identify AU boundaries and for hypothetical reference decoder (HRD) operations that require input and output timing at AU granularity. In most cases, the decoded picture with the top layer of the AU may be output for display. The AUC value and layer_id value may be used to identify the output picture.

[0119] In embodiments, a picture may consist of one or more sub-pictures. Each sub-picture may cover a local area or the entire area of ​​the picture. The area supported by a sub-picture may or may not overlap with the area supported by other sub-pictures. The area comprised by one or more sub-pictures may or may not cover the entire area of ​​the picture. When a picture consists of sub-pictures, the area supported by the sub-pictures is the same as the area supported by the picture.

[0120] In the same embodiment, sub-pictures may be coded by a coding method similar to that used for the coded picture. Sub-pictures may be coded independently or may be coded dependent on other sub-pictures or coded pictures. Sub-pictures may or may not have any parsing dependency from other sub-pictures or coded pictures.

[0121] In the same embodiment, a coded sub-picture may be included in one or more layers. The coded sub-pictures within a layer may have different spatial resolutions. The original sub-picture may be spatially resampled (upsampled or downsampled), coded with different spatial resolution parameters, and included in the bitstream corresponding to the layer.

[0122] In the same or other embodiments, a subpicture having (W, H), where W denotes the width of the subpicture and H denotes the height of the subpicture, may be coded and included in the coded bitstream corresponding to layer 0, while a subpicture having (W×S), which is upsampled (or downsampled) from a subpicture having the original spatial resolution, may be coded and included in the coded bitstream corresponding to layer 1. w,k ,H×S h,k ) may be coded and included in the coded bitstream corresponding to layer k, where S w,k , S h,k are the resampling ratios in the horizontal and vertical directions, respectively. w,k , S h,k When the value of is greater than 1, resampling is equivalent to upsampling. On the other hand, S w,k , S h,k If the value of is less than 1, resampling is equivalent to downsampling.

[0123] In the same or other embodiments, a coded subpicture within a layer may have a different visual quality than that of a coded subpicture within another layer, either in the same subpicture or in a different subpicture. For example, subpicture i within layer n may have a different visual quality than that of a coded subpicture within another layer, either in the same subpicture or in a different subpicture. i,n while subpicture j in layer m is coded with quantization parameter Q j,m It is coded as:

[0124] In the same or other embodiments, coded sub-pictures within a layer may be independently decodable without any parsing or decoding dependency from coded sub-pictures in other layers of the same local region. A sub-picture layer that can be independently decodable without reference to other sub-picture layers of the same local region is an independent sub-picture layer. Coded sub-pictures within an independent sub-picture layer may or may not have decoding or parsing dependencies from previously coded sub-pictures in the same sub-picture layer, but the coded sub-pictures may not have any dependencies from coded sub-pictures in other sub-picture layers.

[0125] In the same or other embodiments, coded sub-pictures within a layer may be dependently decodable, having some parsing or decoding dependency from coded sub-pictures in other layers of the same local region. A sub-picture layer that can be dependently decodable by reference to other sub-picture layers of the same local region is a dependent sub-picture layer. A coded sub-picture in a dependent sub-picture layer may reference coded sub-pictures belonging to the same sub-picture, previously coded sub-pictures in the same sub-picture layer, or both.

[0126] In the same or other embodiments, a coded subpicture consists of one or more independent subpicture layers and one or more dependent subpicture layers. However, at least one independent subpicture layer may exist for a coded subpicture. The value of the layer identifier (layer_id), which may be present in the NAL unit header or other high-level syntax structure, of an independent subpicture layer will be equal to 0. A subpicture layer with layer_id equal to 0 may be a base subpicture layer.

[0127] In the same or other embodiments, a picture may consist of one or more foreground subpictures and one background subpicture. The area supported by a background subpicture may be equal to the area of ​​the picture. The area supported by a foreground subpicture may overlap the area supported by a background subpicture. A background subpicture may be a base subpicture layer, while a foreground subpicture may be a non-base (enhancement) subpicture layer. One or more non-base subpicture layers may reference the same base layer for decoding. Each non-base subpicture layer with layer_id equal to a may reference a non-base subpicture layer with layer_id equal to b, where a is greater than b.

[0128] In the same or other embodiments, a picture may consist of one or more foreground subpictures, with or without background subpictures. Each subpicture may have its own base subpicture layer and one or more non-base (enhancement) layers. Each base subpicture layer may be referenced by one or more non-base subpicture layers. Each non-base subpicture layer with layer_id equal to a may reference a non-base subpicture layer with layer_id equal to b, where a is greater than b.

[0129] In the same or other embodiments, a picture may consist of one or more foreground subpictures, with or without background subpictures. Each coded subpicture in a subpicture layer (base or non-base) may be referenced by one or more non-base layer subpictures that belong to the same subpicture, and by one or more non-base layer subpictures that do not belong to the same subpicture.

[0130] In the same or other embodiments, a picture may consist of one or more foreground subpictures with or without background subpictures. A subpicture in layer a may be further partitioned into multiple subpictures within the same layer. One or more coded subpictures in layer b may reference a partitioned subpicture in layer a.

[0131] In the same or other embodiments, a coded video sequence (CVS) may be a group of coded pictures. A CVS may consist of one or more coded sub-picture sequences (CSPS), which may be groups of coded sub-pictures covering the same local region of a picture. A CSPS may have the same or a different temporal resolution than that of the coded video sequence.

[0132] In the same or other embodiments, a CSPS may be coded and included in one or more layers. A CSPS may consist of one or more CSPS layers. Decoding one or more CSPS layers corresponding to a CSPS may reconstruct a sequence of sub-pictures corresponding to the same local region.

[0133] In the same or other embodiments, the number of CSPS layers corresponding to a CSPS may be the same as or different from the number of CSPS layers corresponding to other CSPSs.

[0134] In the same or other embodiments, a CSPS layer may have a different temporal resolution (e.g., frame rate) than other CSPS layers, and the original (uncompressed) sub-picture sequence may be temporally resampled (e.g., upsampled or downsampled), coded with different temporal resolution parameters, and included in the bitstream corresponding to the layer.

[0135] In the same or other embodiments, a sub-picture sequence with a frame rate F may be coded and included in the coded bitstream corresponding to layer 0, while a sub-picture sequence with a frame rate F×S may be temporally upsampled (or downsampled) from the original sub-picture sequence. t,k may be coded and included in the coded bitstream corresponding to layer k, where S t,k denotes the temporal sampling ratio for layer k. t,k If the value of is greater than 1, the temporal resampling process is equivalent to frame rate up-conversion. t,k If ∑ is less than 1, the temporal resampling process is equivalent to frame rate down-conversion.

[0136] In the same or other embodiments, when a subpicture with CSPS layer a is referenced by a subpicture with CSPS layer b for motion compensation or some inter-layer prediction, if the spatial resolution of CSPS layer a is different from the spatial resolution of CSPS layer b, the decoded pixels in CSPS layer a are resampled and used for reference. The resampling process may require upsampling filtering or downsampling filtering.

[0137] In the same or another embodiment, Figure 9 shows an example of a syntax table for signaling the vps_poc_cycle_au syntax element in the VPS (or SPS), which indicates the poc_cycle_au used for all pictures / slices in the coded video sequence, and the slice_poc_cycle_au syntax element, which indicates the poc_cycle_au of the current slice in the slice header. When the POC value increases uniformly per AU, vps_contant_poc_cycle_per_au in the VPS is set equal to 1, and vps_poc_cycle_au is signaled in the VPS. In this case, slice_poc_cycle_au is not explicitly signaled, and the AUC value for each AU is calculated by dividing the POC value by vps_poc_cycle_au. When the POC value does not increase uniformly per AU, vps_contant_poc_cycle_per_au in the VPS is set equal to 0. In this case, vps_access_unit_cnt is not signaled, while slice_access_unit_cnt is signaled in the slice header for each slice or picture. Each slice or picture may have a different value of slice_access_unit_cnt. The AUC value for each AU is calculated by dividing the POC value by slice_poc_cycle_au. Figure 10 shows a block diagram representing the related workflow.

[0138] In the same or other embodiments, pictures, slices, or tiles corresponding to AUs having the same AUC value may be associated with the same decoding or output time instance, even though the POC values ​​of the pictures, slices, or tiles may differ. Thus, all or a subset of pictures, slices, or tiles associated with the same AU may be decoded in parallel and output at the same time instance, without any mutual parsing / decoding dependencies between pictures, slices, or tiles within the same AU.

[0139] In the same or other embodiments, pictures, slices, or tiles corresponding to AUs with the same AUC value may be associated with the same compositing / display time instance, even though the POC values ​​of the pictures, slices, or tiles may differ. If compositing time is included in the container format, pictures may be displayed at the same time instance if they have the same compositing time, even if they correspond to different AUs.

[0140] In the same or other embodiments, each picture, slice, or tile may have the same temporal identifier (temporal_id) in the same AU. All or a subset of pictures, slices, or tiles corresponding to a time instance may be associated with the same temporal sublayer. In the same or other embodiments, each picture, slice, or tile may have the same or different spatial layer id (layer_id) in the same AU. All or a subset of pictures, slices, or tiles corresponding to a time instance may be associated with the same or different spatial layers.

[0141] Figure 11 shows an example of a video stream including a background video CSPS with layer_id equal to 0 and multiple foreground CSPS layers. A coded subpicture may consist of one or more CSPS layers, while background regions that do not belong to any foreground CSPS layer may consist of the base layer. The base layer may include background and foreground regions, while the enhanced CSPS layer may include foreground regions. The enhanced CSPS layer may have better visual quality than the base layer for the same region. The enhanced CSPS layer may reference the motion vectors and reconstructed pixels of the base layer corresponding to the same region.

[0142] In the same or another embodiment, in a video file, the video bitstream corresponding to the base layer is included in a track, while the CSPS layers corresponding to each sub-picture are included in separate tracks.

[0143] In the same or other embodiments, the video bitstream corresponding to the base layer is included in a track, while the CSPS layers having the same layer_id are included in separate tracks. In this example, the track corresponding to layer k includes only the CSPS layers corresponding to layer k.

[0144] In the same or other embodiments, each CSPS layer of each subpicture is stored in a separate track. Each track may or may not have any parsing or decoding dependencies from one or more other tracks.

[0145] In the same or other embodiments, each track may include a bitstream corresponding to layer i to layer j of the CSPS layers of all or a subset of the subpictures. Here, 0 < i <= j <= k, where k is the highest layer of CSPS.

[0146] In the same or other embodiments, a picture consists of one or more associated media data including a depth map, an alpha map, 3D geometry data, an occupancy map, etc. Such associated timed media data can be divided into one or more data substreams each corresponding to one subpicture.

[0147] In the same or other embodiments, FIG. 12 shows an example of a video conference based on a multi-layer subpicture method. The video stream includes one base layer video bitstream corresponding to a background picture and one or more enhancement layer video bitstreams corresponding to foreground subpictures. Each enhancement layer video bitstream corresponds to a CSPS layer. On the display, the picture corresponding to the base layer is displayed by default. The base layer includes Picture In Picture (PIP) of one or more users. When a particular user is selected by the control of the client, the enhanced CSPS layer corresponding to the selected user is decoded and displayed with improved quality or spatial resolution. FIG. 13 shows a diagram of the operation.

[0148] In the same or other embodiments, a network middlebox (e.g., a router) may select a subset of layers to send to a user depending on its bandwidth. The picture / subpicture organization may be used for bandwidth adaptation. For example, if a user does not have the bandwidth, the router may remove layers or select some subpictures based on their importance or the settings being used. This may be done dynamically to adapt to the bandwidth.

[0149] Figure 14 shows a use case for 360-degree video. When a spherical 360-degree picture is projected onto a planar picture, the projected 360-degree picture may be partitioned into multiple sub-pictures as a base layer. The enhancement layer of a specific sub-picture may be coded and transmitted to the client. The decoder may be able to decode both the base layer containing all sub-pictures and the enhancement layer of a selected sub-picture. If the current viewport is the same as the selected sub-picture, the displayed picture may have higher quality in the decoded sub-picture with the enhancement layer. Otherwise, the decoded picture including the base layer may be displayed with lower quality.

[0150] In the same or other embodiments, any layout information for display may be present in the file as supplemental information (e.g., SEI messages or metadata). One or more decoded subpictures may be rearranged or displayed according to the signaled layout information. The layout information may be signaled by a streaming server or broadcaster, or may be played by a network entity or cloud server, or may be determined by a user's customized settings.

[0151] In an embodiment, when an input picture is divided into one or more (rectangular) sub-regions, each sub-region may be coded as an independent layer. Each independent layer corresponding to a local region may have a unique layer_id value. For each independent layer, sub-picture size and position information may be signaled. For example, the picture size (width, height) and the offset information of the top-left corner (x_offset, y_offset) may be signaled. Figure 15 shows an example of a layout of divided sub-pictures, their sub-picture size and position information, and their corresponding picture prediction structure. Layout information including sub-picture size and sub-picture position may be signaled in a higher-level syntax structure such as a parameter set, a slice or tile group header, or an SEI message.

[0152] In the same embodiment, each sub-picture corresponding to an independent layer may have its unique POC value within the AU, and the POC value of each sub-picture corresponding to a layer may be used when a reference picture in a picture stored in the DPB is indicated by using a syntax element in the RPS or RPL structure.

[0153] In the same or other embodiments, the layer_id may not be used and the POC (difference) value may be used to indicate the (inter-layer) prediction structure.

[0154] In the same embodiment, a sub-picture having a POC value equal to N corresponding to a layer (or local region) may or may not be used as a reference picture for motion compensated prediction of a sub-picture having a POC value equal to K+N corresponding to the same layer (or the same local region). In most cases, the value of the number K will be equal to the maximum number of (independent) layers, which may be the same as the number of sub-regions.

[0155] In the same or another embodiment, Figure 16 shows an extended case of Figure 15. When an input picture is divided into multiple (e.g., four) sub-regions, each local region may be coded with one or more layers. In this case, the number of independent layers may be equal to the number of sub-regions, and one or more layers may correspond to one sub-region. Thus, each sub-region may be coded with one or more independent layers and zero or more dependent layers.

[0156] In the same embodiment, in Figure 16, the input picture may be divided into four sub-regions. The top-right sub-region may be coded as two layers, Layer 1 and Layer 4, while the bottom-right sub-region may be coded as two layers, Layer 3 and Layer 5. In this case, Layer 4 may refer to Layer 1 for motion-compensated prediction, while Layer 5 may refer to Layer 3 for motion compensation.

[0157] In the same or other embodiments, in-loop filtering across layer boundaries (e.g., deblocking filtering, adaptive in-loop filtering, reshapers, bilateral filtering, or any deep learning based filtering) may be (optionally) disabled.

[0158] In the same or other embodiments, motion compensated prediction or intra block copying across layer boundaries may (optionally) be disabled.

[0159] In the same or other embodiments, boundary padding for motion compensated prediction or in-loop filtering at sub-picture boundaries may be optionally processed. A flag indicating whether boundary padding is processed may be signaled in a higher level syntax structure, such as a parameter set (VPS, SPS, PPS, or APS), a slice or tile group header, or an SEI message.

[0160] In the same or other embodiments, layout information for sub-regions (or sub-pictures) may be signaled in the VPS or SPS. Figure 17 shows an example of syntax elements in the VPS and SPS. In this example, vps_sub_picture_dividing_flag is signaled in the VPS. The flag may indicate whether the input picture is divided into multiple sub-regions. If the value of vps_sub_picture_dividing_flag is equal to 0, the input picture in the coded video sequence corresponding to the current VPS may not be divided into multiple sub-regions. In this case, the size of the input picture is equal to the coded picture size (pic_width_in_luma_samples, pic_height_in_luma_samples) signaled in the SPS. If the value of vps_sub_picture_dividing_flag is equal to 1, the input picture may be divided into multiple sub-regions. In this case, the syntax elements vps_full_pic_width_in_luma_samples and vps_full_pic_height_in_luma_samaples are signaled in the VPS. The values ​​of vps_full_pic_width_in_luma_samples and vps_full_pic_height_in_luma_samaples are equal to the width and height of the input picture, respectively.

[0161] In the same embodiment, the values ​​of vps_full_pic_width_in_luma_samples and vps_full_pic_height_in_luma_samples may not be used for decoding, but may be used for synthesis and display.

[0162] In the same embodiment, the syntax elements pic_offset_x and pic_offset_y may be signaled in the SPS corresponding to a specific layer when the value of vps_sub_picture_dividing_flag is equal to 1. In this case, the size of the coded picture signaled in the SPS (pic_width_in_luma_samples, pic_height_in_luma_samples) is equal to the width and height of the sub-region corresponding to a specific layer. Also, the position of the upper left corner of the sub-region (pic_offset_x, pic_offset_y) may be signaled in the SPS.

[0163] In the same embodiment, the position information (pic_offset_x, pic_offset_y) of the top left corner of the sub-region may not be used for decoding, but may be used for synthesis and display.

[0164] In the same or other embodiments, layout information (size and position) of all or a subset of the subregions of the input picture, as well as inter-layer dependency information, may be signaled in a parameter set or SEI message. Figure 18 shows an example of syntax elements indicating information about the layout of subregions, inter-layer dependencies, and the relationship between subregions and one or more layers. In this example, the syntax element num_sub_region indicates the number of (rectangular) subregions in the current coded video sequence. The syntax element num_layers indicates the number of layers in the current coded video sequence. The value of num_layers may be greater than or equal to the value of num_sub_region. If any subregion is coded as a single layer, the value of num_layers is equal to the value of num_sub_region. If one or more subregions are coded as multiple layers, the value of num_layers is greater than the value of num_sub_region. The syntax element direct_dependency_flag[i][j] indicates the dependency of the jth layer to the ith layer. num_layers_for_region[i] indicates the number of layers associated with the i-th subregion. sub_region_layer_id[i][j] indicates the layer_id of the j-th layer associated with the i-th subregion. sub_region_offset_x[i] and sub_region_offset_y[i] indicate the horizontal and vertical positions of the top left corner of the i-th subregion, respectively. sub_region_width[i] and sub_region_height[i] indicate the width and height of the i-th subregion, respectively.

[0165] In one embodiment, one or more syntax elements defining output layer sets to indicate one or more layers to be output with or without profile tier-level information may be signaled in a high-level syntax structure, such as a VPS, DPS, SPS, PPS, APS, or SEI message. With reference to Figure 19, a syntax element num_output_layer_sets indicating the number of output layer sets (OLS) in a coded video sequence that references a VPS may be signaled in the VPS. For each output layer set, output_layer_flag may be signaled as many times as the number of output layers.

[0166] In the same embodiment, output_layer_flag equal to 1 specifies that the i-th layer is output. Output_layer_flag equal to 0 specifies that the i-th layer is not output.

[0167] In the same or other embodiments, one or more syntax elements defining the profile tier level information for each output layer set may be signaled in a higher-level syntax structure, such as a VPS, DPS, SPS, PPS, APS, or SEI message. Still referring to Figure 19, a syntax element num_profile_tier_level indicating the number of profile tier level information per OLS in a coded video sequence that references a VPS may be signaled in the VPS. For each output layer set, an index indicating a particular profile tier level information among the set of syntax elements for profile tier level information or an entry in the profile tier level information may be signaled as many times as the number of output layers.

[0168] In the same embodiment, profile_tier_level_idx[i][j] specifies the index into the list of profile_tier_level() syntax structures in the VPS of the profile_tier_level() syntax structure that applies to the jth layer of the ith OLS.

[0169] In the same or other embodiments, referring to FIG. 20, the syntax elements num_profile_tile_level and / or num_output_layer_sets may be signaled if the number of maximum layers is greater than 1 (vps_max_layers_minus1>0).

[0170] In the same or other embodiments, referring to FIG. 20, a syntax element vps_output_layers_mode[i] may be present in the VPS, indicating the mode of output layer signaling for the i-th output layer set.

[0171] In the same embodiment, vps_output_layers_mode[i] equal to 0 specifies that only the highest layer is output by the i-th output layer set. vps_output_layers_mode[i] equal to 1 specifies that all layers are output by the i-th output layer set. vps_output_layers_mode[i] equal to 2 specifies that the layer output by the i-th output layer set is the layer with vps_output_layer_flag[i][j] equal to 1. More values ​​may be reserved.

[0172] In the same embodiment, output_layer_flag[i][j] may or may not be signaled depending on the value of vps_output_layers_mode[i] for the i-th output layer set.

[0173] In the same or other embodiments, referring to Figure 20, a flag vps_ptl_flag[i] may be present for the i-th output layer set. Depending on the value of vps_ptl_flag[i], the profile tier level information for the i-th output layer set may or may not be signaled.

[0174] In the same or other embodiments, referring to FIG. 21, the number of sub-pictures in the current CVS, max_subpics_minus1, may be signaled in a higher level syntax structure, such as a VPS, DPS, SPS, PPS, APS, or SEI message.

[0175] In the same embodiment, referring to FIG. 21, the sub-picture identifier sub_pic_id[i] of the ith sub-picture may be signaled if the number of sub-pictures is greater than 1 (max_subpics_minus1>0).

[0176] In the same or other embodiments, one or more syntax elements indicating sub-picture identifiers belonging to each layer of each output layer set may be signaled in the VPS. With reference to Figure 22, sub_pic_id_layer[i][j][k] indicates the kth sub-picture present in the jth layer of the ith output layer set. With this information, a decoder may know which sub-pictures can be decoded and output for each layer of a particular output layer set.

[0177] In an embodiment, a picture header (PH) is a syntax structure that contains syntax elements that apply to all slices of a coded picture. A picture unit (PU) is a set of NAL units that are related to each other according to specific classification rules, are consecutive in decoding order, and contain exactly one coded picture. A PU may contain a picture header (PH) and one or more video coding layer (VCL) NAL units that make up a coded picture.

[0178] In an embodiment, the SPS (RBSP) may be available to the decoding process before it is referenced, may be contained in at least one AU with TemporalID equal to 0, or may be supplied through external means.

[0179] In an embodiment, the SPS (RBSP) may be available to the decoding process before it is referenced, may be included in at least one AU with TemporalID equal to 0 in a CVS that contains one or more PPSs that reference the SPS, or may be supplied through external means.

[0180] In an embodiment, the SPS (RBSP) may be available to the decoding process before it is referenced by one or more PPSs, may be included in at least one PU with nuh_layer_id equal to the smallest nuh_layer_id value of the PPS NAL unit that references the SPS in a CVS that contains one or more PPSs that reference the SPS, or may be supplied through external means.

[0181] In an embodiment, the SPS (RBSP) may be available to the decoding process before it is referenced by one or more PPSs, or may be included in at least one PU with TemporalID equal to 0 and nuh_layer_id equal to the minimum nuh_layer_id value of the PPS NAL units that reference the SPS NAL unit, or may be supplied through external means.

[0182] In an embodiment, the SPS (RBSP) may be available to the decoding process before it is referenced by one or more PPSs, or may be included in at least one PU with TemporalID equal to 0 and nuh_layer_id equal to the minimum nuh_layer_id value of the PPS NAL unit that references the SPS NAL unit in its CVS, or may be supplied through external means.

[0183] In the same or other embodiments, pps_seq_parameter_set_id specifies the value of sps_seq_parameter_set_id for the referenced SPS. The value of pps_seq_parameter_set_id may be the same for all PPSs referenced by coded pictures in CLVS.

[0184] In the same or other embodiments, all SPS NAL units with a particular value of sps_seq_parameter_set_id in the CVS may have the same content.

[0185] In the same or other embodiments, regardless of the nuh_layer_id value, SPS NAL units may share the same value space for sps_seq_parameter_set_id.

[0186] In the same or other embodiments, the nuh_layer_id value of an SPS NAL unit may be equal to the smallest nuh_layer_id value of the PPS NAL units that reference that SPS NAL unit.

[0187] In an embodiment, when an SPS with nuh_layer_id equal to m is referenced by one or more PPSs with nuh_layer_id equal to n, the layer with nuh_layer_id equal to m may be the same as the (direct or indirect) reference layer of the layer with nuh_layer_id equal to n or the layer with nuh_layer_id equal to m.

[0188] In an embodiment, the PPS (RBSP) should be available to the decoding process before it is referenced, or be contained in at least one AU with a TemporalID equal to the TemporalID of the PPS NAL unit, or be supplied through external means.

[0189] In an embodiment, the PPS (RBSP) may be available to the decoding process before it is referenced, may be included in at least one AU with a TemporalID equal to the TemporalID of the PPS NAL unit in a CVS containing one or more PHs (or coded slice NAL units) that reference the PPS, or may be supplied through external means.

[0190] In an embodiment, the PPS (RBSP) may be available to the decoding process before it is referenced by one or more PHs (or coded slice NAL units), may be included in at least one PU with nuh_layer_id equal to the smallest nuh_layer_id value of the coded slice NAL units that reference the PPS NAL unit in the CVS containing one or more PHs (or coded slice NAL units) that reference the PPS, or may be supplied through external means.

[0191] In an embodiment, the PPS (RBSP) may be available to the decoding process before it is referenced by one or more PHs (or coded slice NAL units), or may be included in at least one PU with nuh_layer_id equal to the smallest nuh_layer_id value of the coded slice NAL units that reference the PPS NAL unit in the CVS containing one or more PHs (or coded slice NAL units) that reference the PPS, and with a TemporalID equal to the TemporalID of the PPS NAL unit, or may be supplied through external means.

[0192] In the same or other embodiments, ph_pic_parameter_set_id in PH specifies the value of pps_pic_parameter_set_id for the referenced PPS in use. The value of pps_seq_parameter_set_id may be the same for all PPSs referenced by coded pictures in CLVS.

[0193] In the same or other embodiments, all PPS NAL units with a particular value of pps_pic_parameter_set_id within a PU should have the same content.

[0194] In the same or other embodiments, PPS NAL units may share the same value space for pps_pic_parameter_set_id regardless of the nuh_layer_id value.

[0195] In the same or other embodiments, the nuh_layer_id of a PPS NAL unit may be equal to the smallest nuh_layer_id value of the coded slice NAL units that reference the NAL units that reference that PPS NAL unit.

[0196] In an embodiment, when a PPS with nuh_layer_id equal to m is referenced by one or more coded slice NAL units with nuh_layer_id equal to n, the layer with nuh_layer_id equal to m may be the same as the (direct or indirect) reference layer of the layer with nuh_layer_id equal to n or the layer with nuh_layer_id equal to m.

[0197] In an embodiment, the PPS (RBSP) should be available to the decoding process before it is referenced, or be contained in at least one AU with a TemporalID equal to the TemporalID of the PPS NAL unit, or be provided through external means.

[0198] In an embodiment, the PPS (RBSP) may be available to the decoding process before it is referenced, may be included in at least one AU with a TemporalID equal to the TemporalID of the PPS NAL unit in a CVS containing one or more PHs (or coded slice NAL units) that reference the PPS, or may be supplied through external means.

[0199] In an embodiment, the PPS (RBSP) may be available to the decoding process before it is referenced by one or more PHs (or coded slice NAL units), may be included in at least one PU with nuh_layer_id equal to the smallest nuh_layer_id value of the coded slice NAL units that reference the PPS NAL unit in the CVS containing one or more PHs (or coded slice NAL units) that reference the PPS, or may be supplied through external means.

[0200] In an embodiment, the PPS (RBSP) may be available to the decoding process before it is referenced by one or more PHs (or coded slice NAL units), or may be included in at least one PU with nuh_layer_id equal to the smallest nuh_layer_id value of the coded slice NAL units that reference the PPS NAL unit in the CVS containing one or more PHs (or coded slice NAL units) that reference the PPS, and with a TemporalID equal to the TemporalID of the PPS NAL unit, or may be supplied through external means.

[0201] In the same or other embodiments, ph_pic_parameter_set_id in PH specifies the value of pps_pic_parameter_set_id for the referenced PPS in use. The value of pps_seq_parameter_set_id may be the same for all PPSs referenced by coded pictures in CLVS.

[0202] In the same or other embodiments, all PPS NAL units with a particular value of pps_pic_parameter_set_id within a PU should have the same content.

[0203] In the same or other embodiments, PPS NAL units may share the same value space for pps_pic_parameter_set_id regardless of the nuh_layer_id value.

[0204] In the same or other embodiments, the nuh_layer_id of a PPS NAL unit may be equal to the smallest nuh_layer_id value of the coded slice NAL units that reference the NAL units that reference that PPS NAL unit.

[0205] In an embodiment, when a PPS with nuh_layer_id equal to m is referenced by one or more coded slice NAL units with nuh_layer_id equal to n, the layer with nuh_layer_id equal to m may be the same as the (direct or indirect) reference layer of the layer with nuh_layer_id equal to n or the layer with nuh_layer_id equal to m.

[0206] In an embodiment, pps_subpic_id[i] in a picture parameter set specifies the subpicture ID of the ith subpicture, as shown in Figure 22. The length of the pps_subpic_id[i] syntax element is pps_subpic_id_len_minus1+1 bits.

[0207] The variable SubpicIdVal[i] is derived as follows for each value of i in the range 0 to sps_num_subpics_minus1, inclusive:

number

[0208] In the same or other embodiments, for any two different values ​​of i and j in the range from 0 to sps_num_subpics_minus1, inclusive, SubpicIdVal[i] may not be equal to SubpicIdVal[j].

[0209] In the same or other embodiments, if the current picture is not the first picture in the CLVS, then for each value of i in the range from 0 to sps_num_subpics_minus1, inclusive, if the value of SubpicIdVal[i] is not equal to the value of SubpicIdVal[i] of the previous picture in decoding order within the same layer, then the nal_unit_type for all coded slice NAL units of subpictures in the current picture with subpicture index i is equal to a specific value in the range from IDR_W_RADL to CRA_NUT, inclusive.

[0210] In the same or other embodiments, if the current picture is not the first picture in the CLVS, then for each value of i in the range 0 to sps_num_subpics_minus1, inclusive, if the value of SubpicIdVal[i] is not equal to the value of SubpicIdVal[i] of the previous picture in decoding order within the same layer, then sps_independent_subpics_flag is equal to 1.

[0211] In the same or other embodiments, if the current picture is not the first picture in the CLVS, then for each value of i in the range 0 to sps_num_subpics_minus1, inclusive, if the value of SubpicIdVal[i] is not equal to the value of SubpicIdVal[i] of the previous picture in decoding order within the same layer, then subpic_treated_as_pic_flag[i] and loop_flter_across_subpic_enabled_flag[i] are equal to 1.

[0212] In the same or other embodiments, if the current picture is not the first picture in the CLVS, then for each value of i in the range 0 to sps_num_subpics_minus1, inclusive, if the value of SubpicIdVal[i] is not equal to the value of SubpicIdVal[i] of the previous picture in decoding order within the same layer, then sps_independent_subpics_flag shall be equal to 1, or alternatively subpic_treated_as_pic_flag[i] and loop_flter_across_subpic_enabled_flag[i] shall be equal to 1.

[0213] In the same or other embodiments, the value of a sub-picture identifier for a region may be changed within a coded video sequence when the sub-picture is encoded independently without any reference to other sub-pictures.

[0214] Samples are processed in units of CTBs. The array size per luma CTB, in both width and height, is CtbSizeY in units of samples. The array width and height per chroma CTB are CtbWidthC and CtbHeightC, respectively, in units of samples. Each CTB is assigned partition signaling to identify block sizes for intra or inter prediction and for transform coding. The partitioning is recursive quadtree partitioning. The root of the quadtree is assigned a CTB. The quadtree is split to reach leaves, called quadtree leaves. A CTB at the right component boundary is incomplete if the component width is not an integer multiple of the CTB size. A CTB at the ↓ component boundary is incomplete if the component height is not an integer multiple of the CTB size.

[0215] The width and height of each subpicture may be signaled in the SPS in units of CtbSizeY. In Figure 23, for example, subpic_width_minus1[i]+1 specifies the width of the i-th subpicture in units of CtbSizeY. The length of the syntax element is Ceil(Log2((pic_width_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)) bits. If not present, the value of subpic_width_minus1[i] is inferred to be equal to ((pic_width_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)-subpic_ctu_top_left_x[i]-1. subpic_height_minus1[i]+1 specifies the height of the i-th subpicture in units of CtbSizeY. The length of the syntax element is Ceil(Log2((pic_hight_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)) bits. If not present, the value of subpic_height_minus1[i] is inferred to be equal to ((pic_height_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)-subpic_ctu_top_left_y[i]-1.

[0216] The width of each subpicture may be greater than or equal to CtbSizeY if the picture width is greater than or equal to CtbSizeY. The height of each subpicture may be greater than or equal to CtbSizeY if the picture height is greater than or equal to CtbSizeY.

[0217] If the picture width is less than or equal to CtbSizeY and the picture height is less than or equal to CtbSizeY, the picture may not be partitioned into more than one sub-picture, in which case the number of sub-pictures may be equal to 1.

[0218] If pic_width_max_in_luma_samples is less than or equal to CtbSizeY and pic_height_max_in_luma_samples is less than or equal to CtbSizeY, the value of subpic_info_present_flag shall be equal to 0. When subpic_info_present_flag is equal to 0, no explicit signaling exists for subpicture partitioning information and the number of subpictures in the picture is equal to 1.

[0219] In the same or other embodiments, sps_subpic_id_len_minus1+1 specifies the number of bits used to represent the syntax element sps_subpic_id[i], the syntax element pps_subpic_id[i], if present, and the syntax element slice_subpic_id, if present. The value of sps_subpic_id_len_minus1 may range from 0 to 15, inclusive. The value of 1<<(sps_subpic_id_len_minus1) may be greater than or equal to sps_num_subpics_minus1+1.

[0220] In the same or other embodiments, if the number of sub-pictures is equal to 1, subpic_info_present_flag is equal to 1 and sub-picture partitioning information may not be explicitly signaled, because in that case the sub-picture width and height information is equal to the picture width and height information, and the top-left position of the sub-picture is equal to the top-left position of the picture.

[0221] For example, subpic_ctu_top_left_x[i] specifies the horizontal position of the top-left CTU of the ith subpicture in units of CtbSizeY. The length of the syntax element is Ceil(Log2((pic_width_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)) bits. If not present, the value of subpic_ctu_top_left_x[i] is inferred to be equal to 0. subpic_ctu_top_left_y[i] specifies the vertical position of the top-left CTU of the ith subpicture height in units of CtbSizeY. The length of the syntax element is Ceil(Log2((pic_height_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)) bits. If not present, the value of subpic_ctu_top_left_y[i] is inferred to be equal to 0. subpic_width_minus1[i]+1 specifies the width of the ith subpicture in units of CtbSizeY. The length of this syntax element is Ceil(Log2((pic_width_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)) bits. If not present, the value of subpic_width_minus1[i] is inferred to be equal to ((pic_width_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)-subpic_ctu_top_left_x[i]-1. subpic_height_minus1[i]+1 specifies the height of the ith subpicture in units of CtbSizeY. The length of this syntax element is Ceil(Log2((pic_height_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)) bits. If not present, the value of subpic_height_minus1[i] is inferred to be equal to ((pic_height_max_in_luma_samples+CtbSizeY-1)>>CtbLog2SizeY)-subpic_ctu_top_left_y[i]-1.

[0222] In the same or other embodiments, if the number of sub-pictures is greater than 1, subpic_info_present_flag is equal to 1 and the sub-picture partitioning information may be explicitly signaled in the parameter set, as shown in FIG.

[0223] For example, in Figure 23, sps_num_subpics_minus2+2 specifies the number of subpictures in each picture in CLVS. The value of sps_num_subpics_minus2 can range from 0 to Ceil(pic_width_max_in_luma_samples÷CtbSizeY) * Ceil(pic_height_max_in_luma_samples÷CtbSizeY)-1, inclusive. If not present, the value of sps_num_subpics_minus2 is inferred to be equal to 0.

[0224] In the same embodiment, the lists SubpicWidthInTiles[i] and SubpicHeightInTiles[i], for i in the range 0 to sps_num_subpics_minus1, inclusive, specifying the width and height of the ith subpicture in the tile column and row, respectively, and the list subpicHeightLessThanOneTileFlag[i], for i in the range 0 to sps_num_subpics_minus1, inclusive, specifying whether the height of the ith subpicture is less than one tile row, are derived as follows:

number

[0225] When rect_slice_flag is equal to 1, the list NumCtusInSlice[i] for i in the range 0 to num_slices_in_pic_minus1, inclusive, that specifies the number of CTUs in the i-th slice, the list SliceTopLeftTileIdx[i] for i in the range 0 to num_slices_in_pic_minus1, inclusive, that specifies the tile index of the tile containing the first CTU in the slice, and the matrix CtbAddrInSlice[i][j] for i in the range 0 to num_slices_in_pic_minus1, inclusive, and j in the range 0 to NumCtusInSlice[i]-1, inclusive, that specifies the picture raster scan address of the j-th CTB in the i-th slice, and the variable NumSlicesInTile[i] that specifies the number of slices in the tile containing the i-th slice are derived as follows:

number

[0226] Two or more independently coded sub-pictures may be merged into a coded picture so that the coded picture can be decoded and output as a single picture.

[0227] A coded picture may consist of VCL NAL units with two or more different NAL unit types when two or more independently coded subpictures are merged into the coded picture.

[0228] In Figure 23, the flag mixed_nalu_types_in_pic_flag may be signaled in a parameter set (e.g., PPS, SPS). mixed_nalu_types_in_pic_flag equal to 1 specifies that each picture that references a PPS has more than one VCL NAL unit and that no VCL NAL units have the same value of nal_unit_type. mixed_nalu_types_in_pic_flag equal to 0 specifies that each picture that references a PPS has one or more VCL NAL units and that the VCL NAL units of each picture that references a PPS have the same value of nal_unit_type.

[0229] If mixed_nalu_types_in_pic_flag in the PPS is equal to 1, each picture with mixed_nalu_types_in_pic_flag is treated as a trailing picture. Thus, a coded picture with two or more different NAL unit types can be decoded as a trailing picture. A picture may be treated as a trailing picture if it is referenced by a subsequent picture in decoding order.

[0230] In Figure 23, sps_independent_subpics_flag equal to 1 specifies that all subpicture boundaries in CLVS are treated as picture boundaries and there is no loop filtering between subpicture boundaries. sps_independent_subpics_flag equal to 0 imposes no such constraint. When not present, the value of sps_independent_subpics_flag is inferred to be equal to 0.

[0231] In Figure 23, subpic_treated_as_pic_flag[i] equal to 1 specifies that the i-th subpicture of each coded picture in CLVS is treated as a picture in the decoding process excluding in-loop filtering operations. subpic_treated_as_pic_flag[i] equal to 0 specifies that the i-th subpicture of each coded picture in CLVS is not treated as a picture in the decoding process excluding in-loop filtering operations. If not present, the value of subpic_treated_as_pic_flag[i] is inferred to be equal to sps_independent_subpics_flag. When subpic_treated_as_pic_flag[i] equals 1, it is a requirement of bitstream conformance that all of the following conditions are true for each output layer and its reference layers in the OLS, including the layer that contains the i-th subpicture as an output layer:

[0232] All pictures in the output layer and its reference layers should have the same value of pic_width_max_in_luma_samples and the same value of pic_height_max_in_luma_samples.

[0233] All SPSs referenced by the output layer and its reference layers should have the same value of sps_num_subpics_minus1, and for each value of j in the range 0 to sps_num_subpics_minus1, should have the same values ​​of subpic_ctu_top_left_x[i], subpic_ctu_top_left_y[i], subpic_width_minus1[j], subpic_height_minus1[j], and loop_flter_across_subpic_enabled_flag[j], respectively.

[0234] All pictures in each access unit in the output layer and its reference layers should have the same value of SubpicIdVal[j] for each value of j in the range 0 to sps_num_subpics_minus1, inclusive.

[0235] In Figure 23, loop_flter_across_subpic_enabled_flag[i] equal to 1 specifies that in-loop filtering operations may be performed across the i-th subpicture boundary within each coded picture in CLVS. Loop_flter_across_subpic_enabled_flag[i] equal to 0 specifies that in-loop filtering operations are not performed across the i-th subpicture boundary within each coded picture in CLVS. If not present, the value of loop_flter_across_subpic_enabled_flag[i] is inferred to be equal to 1-sps_independent_subpics_flag.

[0236] When two or more coded sub-pictures are merged into a coded picture, these coded sub-pictures may not have any parsing or decoding dependency from each other.

[0237] In an embodiment, if mixed_nalu_types_in_pic_flag in a PPS is equal to 1, the value of subpic_treated_as_pic_flag[i] of the subpicture that references the PPS may be equal to 1.

[0238] In an embodiment, mixed_nalu_types_in_pic_flag may be equal to 0 if sps_independent_subpics_flag is equal to 0 and one or more subpic_treated_as_pic_flag[i] values ​​are not equal to 1.

[0239] In an embodiment, if mixed_nalu_types_in_pic_flag is equal to 1, the value of sps_independent_subpics_flag may be equal to 1.

[0240] In an embodiment, if mixed_nalu_types_in_pic_flag in a PPS is equal to 1, the value of subpic_treated_as_pic_flag[i] of the subpicture that references the PPS is inferred to be equal to 1.

[0241] In an embodiment, two or more adjacent subpictures in a picture that have different NAL unit types should have the value of subpic_treated_as_pic_flag[i] equal to 1.

[0242] In an embodiment, in Figure 24, sub-picture partitioning information may be signaled in the PPS. For example, pps_independent_subpics_flag equal to 1 specifies that all boundary sub-pictures referencing the PPS are treated as picture boundaries and that there is no loop filtering between sub-picture boundaries. pps_independent_subpics_flag equal to 0 imposes no such constraint. When not present, the value of pps_independent_subpics_flag is inferred to be equal to 0. pps_subpic_treated_as_pic_flag[i] equal to 1 specifies that the i-th sub-picture of each coded picture referencing the PPS is treated as a picture in the decoding process except for in-loop filtering operations. pps_subpic_treated_as_pic_flag[i] equal to 0 specifies that the i-th sub-picture of each coded picture referencing the PPS is not treated as a picture in the decoding process except for in-loop filtering operations. If not present, the value of pps_subpic_treated_as_pic_flag[i] is inferred to be equal to pps_independent_subpics_flag. pps_loop_filter_across_subpic_enabled_flag[i] equal to 1 specifies that in-loop filtering operations may be performed across the i-th subpicture boundary of each coded picture that references the PPS. pps_loop_filter_across_subpic_enabled_flag[i] equal to 0 specifies that in-loop filtering operations are not performed across the i-th subpicture boundary of each coded picture that references the PPS. If not present, the value of pps_loop_filter_across_subpic_enabled_flag[i] is inferred to be equal to 1-pps_independent_subpics_flag.

[0243] In the same embodiment, if mixed_nalu_types_in_pic_flag in the PPS is equal to 1, the value of pps_subpic_treated_as_pic_flag[i] should be equal to 1.

[0244] In the same or other embodiments, if mixed_nalu_types_in_pic_flag is equal to 1, then pps_independent_subpics_flag shall be equal to 1.

[0245] In the same or other embodiments, if mixed_nalu_types_in_pic_flag is equal to 1, then pps_subpic_treated_as_pic_flag[i] shall be equal to 1.

[0246] In an embodiment, if mixed_nalu_types_in_pic_flag is equal to 1 and at least one VCL NAL unit of the picture has nal_unit_type equal to CRA_NUT, the CRA sub-picture or picture may not be treated as a CVS start picture.

[0247] In an embodiment, if mixed_nalu_types_in_pic_flag is equal to 1 and at least one VCL NAL unit of the picture has a nal_unit_type equal to CRA_NUT, a CRA sub-picture or the first picture associated with the picture may be output.

[0248] In the same embodiment, if mixed_nalu_types_in_pic_flag is equal to 1 and at least one VCL NAL unit of a picture has a nal_unit_type equal to CRA_NUT, then both HandleCraAsCvsStartFlag and NoOutputBeforeRecoveryFlag of that picture are set equal to 0.

[0249] While this disclosure has described several example embodiments, there are alterations, permutations, and various substitute equivalents that fall within the scope of this disclosure. It will thus be apparent to those skilled in the art that numerous systems and methods will be possible which embody the principles of the present disclosure and are therefore within its spirit and scope, even if not explicitly shown or described herein.

Claims

[Claim 1] 1. A processor-executable method for decoding video data, comprising: receiving video data including one or more sub-pictures; identifying a Network Abstraction Layer (NAL) unit type associated with each of the one or more sub-pictures based on checking a flag corresponding to a mixed NAL unit in the one or more sub-pictures; decoding the video data based on the identified NAL unit type; and If the flag indicates the presence of a plurality of different NAL unit types and a video coding layer NAL unit having a clean random access type is present, a first picture associated with the video data is output. method.

Images