Methods, apparatus, and computer programs for coding video data

Abstract

To provide a method, a computer program, and a computer system for coding video data.SOLUTION: Video data is received that includes a current picture and one or more other pictures. A first flag is checked corresponding to whether the current picture is referenced by one or more other pictures in decoding order. A second flag is checked corresponding to whether a current picture is being output. The video data is decoded on the basis of values corresponding to the first flag and the second flag.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] Cross-references to related applications This application claims priority under U.S. Provisional Patent Application No. 63 / 003,112, filed on 31 March 2020, and U.S. Patent Application No. 17 / 087,865, filed on 3 November 2020, both of which are incorporated herein by reference.

[0002] This disclosure generally relates to the field of data processing, and more specifically to video encoding and decoding. [Background technology]

[0003] Video coding and decoding using interpicture prediction with motion compensation have been known for decades. Uncompressed digital video can consist of a series of pictures, each with a spatial dimension of chrominance samples associated with, for example, 1920 x 1080 luminance samples. The series of pictures can have a fixed or variable picture rate (informally also called frame rate), for example, 60 pictures per second, i.e., 60 Hz. Uncompressed video has significant bitrate requirements. For example, 1080p60 4:2:0 video with 8 bits per sample (1920 x 1080 luminance sample resolution at a frame rate of 60 Hz) requires a bandwidth of nearly 1.5 Gbit / s. Using such video for one hour would require more than 600 GB of storage space.

[0004] One purpose of video coding and decoding may be to reduce the redundancy of the input video signal through compression. Compression can help reduce the aforementioned bandwidth or storage requirements by two orders of magnitude or more, in some cases. Both lossless and lossy compression, and combinations thereof, can be used. Lossless compression refers to a technique that allows for the reconstruction of an exact copy of the original signal from the compressed original signal. With lossy compression, the reconstructed signal may not be identical to the original signal, but the distortion between the original and reconstructed signals is small enough that the reconstructed signal is still useful for its intended purpose. For video, lossy compression is widely adopted. The amount of distortion that can be tolerated varies depending on the application. For example, users of certain consumer streaming applications may tolerate higher distortion than users of television broadcast applications. The achievable compression ratio may reflect that higher tolerance / tolerance distortion results in a higher compression ratio.

[0005] Video encoders and decoders can utilize several broad categories of techniques, including motion compensation, transformation, quantization, and entropy coding, some of which are described below.

[0006] Historically, video encoders and decoders have mostly tended to operate with a given picture size defined and constant for coded video sequences (CVS), Groups of Pictures (GOP), or similar multi-picture timeframes. For example, in MPEG-2, the system design is known to change the horizontal resolution (and thus the picture size) depending on factors such as scene activity, but only in the picture, and therefore typically for GOPs. Resampling of the reference picture to use different resolutions within a CVS is known, for example, from ITU-T Rec.H.263 Annex P. However, here the picture size does not change, and only the reference picture is resampled, meaning only a portion of the picture canvas may be used (in the case of downsampling), or only a portion of the scene may be captured (in the case of upsampling). Furthermore, H.263 Annex Q allows for resampling individual macroblocks by a factor of 2 upwards or downwards (in each dimension). Here again, the picture size remains the same. Since the size of the macroblocks is fixed in H.263, there is no need for signaling.

[0007] Changing the picture size of a predictive picture has become more common in modern video coding. For example, VP9 allows for the resampling of a reference picture and the changing of the resolution of the entire picture. Similarly, a proposal made for VVC (including, for example, Hendry et al., "On adaptive resolution change (ARC) for VVC," Joint Video Team document JVET-M0135-v1, January 9-19, 2019, which is incorporated herein in its entirety) allows for the resampling of the entire reference picture to a different (higher or lower) resolution. That document proposes that the different candidate resolutions be coded within a sequence parameter set and referenced by per-picture syntax elements within a picture parameter set. [Overview of the project] [Means for solving the problem]

[0008] Embodiments relate to methods, systems, and computer-readable media for coding video data. According to one embodiment, a method for coding video data is provided. This method may include receiving video data containing a current picture and one or more other pictures. A first flag is checked, corresponding to whether the current picture is referenced in decoding order by one or more other pictures. A second flag is checked, corresponding to whether the current picture is output. The video data is decoded based on the values ​​corresponding to the first and second flags.

[0009] In another embodiment, 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 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. This method may include receiving video data containing a current picture and one or more other pictures. A first flag is checked, corresponding to whether the current picture is referenced in decoding order by one or more other pictures. A second flag is checked, corresponding to whether the current picture is output. The video data is decoded based on the values ​​corresponding to the first and second flags.

[0010] In yet another embodiment, 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 one or more tangible storage devices, the program instructions being executable by a processor. The program instructions are executable by the processor to perform a method which may include receiving video data including a current picture and one or more other pictures accordingly. A first flag corresponding to whether the current picture is referenced in decoding order by one or more other pictures is checked. A second flag corresponding to whether the current picture is output is checked. The video data is decoded based on the values ​​corresponding to the first and second flags.

[0011] These and other purposes, features, and advantages will become apparent from the following detailed description of exemplary embodiments, which should be read in conjunction with the attached drawings. Various features in the drawings are not to scale, as they are provided for clarity in conjunction with the detailed description to facilitate understanding for those skilled in the art. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram of a simplified block diagram of a communication system according to one embodiment. [Figure 2] This is a schematic diagram of a simplified block diagram of a communication system according to one embodiment. [Figure 3] This is a schematic diagram of a simplified block diagram of a decoder according to one embodiment. [Figure 4] This is a schematic diagram of a simplified block diagram of an encoder according to one embodiment. [Figure 5] This is a schematic diagram of options for signaling ARC parameters according to prior art or embodiments. [Figure 6] This is an example of a syntax table according to one embodiment. [Figure 7]Schematic diagram of a computer system according to an embodiment. [Figure 8] An example of a prediction structure for scalability with adaptive resolution change. [Figure 9] An example of a syntax table according to an embodiment. [Figure 10] Schematic diagram of a simplified block diagram of syntax analysis and decoding of poc cycles and access unit count values for each access unit. [Figure 11] Schematic diagram of a video bitstream structure including multi-layer sub-pictures. [Figure 12] Schematic diagram of the display of a selected sub-picture with enhanced resolution. [Figure 13] Block diagram of decoding and display processing of a video bitstream including multi-layer sub-pictures. [Figure 14] Schematic diagram of 360 video display with an enhancement layer of a sub-picture. [Figure 15] An example of layout information of a sub-picture, its corresponding layer, and a picture prediction structure. [Figure 16] A diagram showing an example of layout information of a sub-picture, its corresponding layer, and a picture prediction structure using a spatial scalability format of a local area. [Figure 17] An example of a syntax table of sub-picture layout information. [Figure 18] An example of a syntax table of an SEI message of sub-picture layout information. [Figure 19] An example of a syntax table showing profile / tiers / levels information of an output layer and each output layer set. [Figure 20] An example of a syntax table showing an output layer mode for each output layer set. [Figure 21] An example of a syntax table showing the current sub-picture of each layer for each output layer set. [Figure 22] This figure shows an example of a syntax table for the video parameter set RBSP. [Figure 23] This is an example of a syntax table showing the output layers configured in output layer set mode. [Figure 24] This is an example of a syntax table for a picture header, which shows the output information of a picture. [Modes for carrying out the invention]

[0013] Detailed embodiments of the claimed structures and methods are disclosed herein. However, it should be understood that the disclosed embodiments are merely illustrative of the claimed structures and methods, which may be embodied in various forms. However, these structures and methods may be embodied in many different forms and should not be construed as being limited to the exemplary embodiments described herein. Rather, these exemplary embodiments are provided so as to convey the scope of this disclosure to those skilled in the art, ensuring that it is thorough and complete. In the description, well-known features and technical details may be omitted to avoid unnecessarily obscuring the presented embodiments.

[0014] As mentioned earlier, video encoders and decoders have generally tended to operate with a given picture size, defined and kept constant for coded video sequences (CVS), Groups of Pictures (GOP), or similar multi-picture timeframes. However, a picture may or may not be referenced by subsequent pictures for motion compensation or other parameter prediction. A picture may or may not be output. Therefore, it may be advantageous to signal reference information and picture output information in one or more parameter sets.

[0015] Embodiments of methods, apparatus (systems), and computer-readable media will be described herein with reference to flowcharts and / or block diagrams of various embodiments. It will be understood that each block in a flowchart and / or block diagram, as well as combinations of blocks in a flowchart and / or block diagram, can be implemented by computer-readable program instructions.

[0016] Figure 1 shows 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). In the case of one-way data transmission, the first terminal (110) can encode video data at its local location for transmission to the other terminal (120) via the network (150). The second terminal (120) can receive the encoded video data from the other terminal via the network (150), decode the encoded data, and display the restored video data. One-way data transmission may be common in media serving applications, etc.

[0017] Figure 1 shows a second pair of terminals (130, 140) provided to support the bidirectional transmission of coded video that may occur, for example, during a video conference. In the case of bidirectional data transmission, each terminal (130, 140) can encode video data captured at its local location for transmission to another terminal over the network (150). Each terminal (130, 140) can also receive coded video data transmitted by other terminals, decode the coded data, and display the restored video data on a local display device.

[0018] In the example in Figure 1, terminal devices (110-140) may be represented as servers, personal computers, and smartphones, but the principles of this disclosure are not limited thereto. Embodiments of this disclosure find applications in laptop computers, tablet computers, media players, and / or dedicated video conferencing equipment. Network (150) represents any number of networks that transmit coded video data between terminals (110-140), including, for example, wired and / or wireless communication networks. Communication network (150) can exchange data over circuit-switched channels and / or packet-switched channels. Typical networks include communication networks, local area networks, wide area networks, and / or the Internet. For the purposes of this discussion, the architecture and topology of network (150) may not be important to the operation of this disclosure unless described herein below.

[0019] Figure 2 shows an example of the use of the disclosed subject matter, illustrating the arrangement of a video encoder and video decoder in a streaming environment. The disclosed subject matter may also be equally applicable to other video-enabled applications, such as video conferencing, digital TV, and the storage of compressed video on digital media including CDs, DVDs, and memory sticks.

[0020] The streaming system may include a capture subsystem (213) which may include a video source (201), such as a digital camera, which creates, for example, an uncompressed video sample stream (202). The sample stream (202), shown in thick lines to highlight the large amount of data 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, as will be described in more detail below. The encoded video bitstream (204), shown in thin lines to highlight the small amount of data compared to the sample stream, may be stored in a streaming server (205) for future use. One or more streaming clients (206, 208) may access the streaming server (205) to retrieve copies (207, 209) of the encoded video bitstream (204). A client (206) may include a video decoder (210) that decodes an incoming copy of an encoded video bitstream (207) and creates 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) may be encoded according to specific video coding / compression standards. Examples of these standards include ITU-T Recommendation H.265. A video coding standard informally known as Versatile Video Coding (VVC) is under development. The disclosed subject matter may be used in the context of VVC.

[0021] Figure 3 may be a functional block diagram of a video decoder (210) according to an embodiment of the present invention.

[0022] The receiver (310) can receive one or more codec video sequences to be decoded by the decoder (210), which in the same or other embodiments may be one coded video sequence at a time, and the decoding of each coded video sequence is independent of other coded video sequences. Coded video sequences may be received from a channel (312), which may be a hardware / software link to a storage device that stores encoded video data. The receiver (310) may receive encoded video data together with other data, such as coded audio data and / or auxiliary data streams, which may be transferred to their respective usage entities (not shown). The receiver (310) can isolate 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"). If the receiver (310) is receiving data from a store / forward device with sufficient bandwidth and controllability, or from an isosychronous network, the buffer (315) may not be necessary or may be small. For use in best-effort packet networks such as the Internet, the buffer (315) may be required and can be relatively large and advantageously adapted in size.

[0023] The video decoder (210) may include a parser (320) for reconstructing symbols (321) from the entropy-encoded video sequence. As shown in Figure 2, these categories of symbols may potentially include information used to manage the operation of the decoder (210), and information for controlling rendering devices such as a display (212), which are not integral parts of the decoder but can be coupled to it. The rendering device control information may take the form of Supplementary Enhancement Information (SEI messages) or Video Usability Information (VUI) parameter set fragments (not shown). The parser (320) can parse / entropy decode the received encoded video sequence. The coding of the encoded video sequence may conform to video coding techniques or video coding standards and may follow principles well known to those skilled in the art, including variable-length coding, Huffman coding, arithmetic coding, etc., with or without context dependence. The parser (320) can extract from the coded video sequence at least one set of subgroup parameters from subgroups of pixels in the video decoder, based on at least one parameter corresponding to a group. Subgroups may include Group of Pictures (GOP), picture, tile, slice, macroblock, coding unit (CU), block, transform unit (TU), predictive unit (PU), etc. The entropy decoder / parser can also extract from coded video sequence information such as transform coefficients, quantization parameter values, and motion vectors.

[0024] The parser (320) can perform entropy decoding / parse operations on the video sequence received from the buffer (315) in order to create symbols (321).

[0025] The reconstruction of the symbol (321) may involve several different units, depending on the type of the encoded video picture or a portion thereof (such as interpictures and intrapictures, interblocks and intrablocks), and other factors. The units included and the method thereof may be controlled by subgroup control information parsed from the video sequence encoded by the parser (320). For clarity, the flow of such subgroup control information between the parser (320) and the following multiple units is not shown.

[0026] In addition to the functional blocks already described, the decoder 210 can be conceptually subdivided into several functional units, as described below. In actual implementations operating under commercial constraints, many of these units may interact closely with each other and be integrated, at least partially. However, for the purpose of illustrating the disclosed subject matter, the following conceptual subdivision into functional units is appropriate.

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

[0028] In some cases, the output samples of the scaler / inverse transform (351) may relate to intra-coded blocks, i.e., blocks that do not use predictive information from a previously reconstructed picture but can now use predictive information from a previously reconstructed portion of the picture. Such predictive information may be provided by the intra-picture predictive unit (352). In some cases, the intra-picture predictive unit (352) generates a block of the same size and shape as the block being reconstructed, using already reconstructed surrounding information fetched from the current (partially reconstructed) picture (356). The aggregator (355) may, sample by sample, add the predictive information generated by the intra-predictive unit (352) to the output sample information provided by the scaler / inverse transform unit (351).

[0029] In other cases, the output samples of the scaler / inverse unit (351) may relate to an intercoded, potentially motion-compensated block. In such cases, the motion-compensated prediction unit (353) can access the reference picture memory (357) to fetch samples to be used for prediction. After motion-compensating the fetched samples according to the symbols (321) associated with the block, these samples may be added to the output of the scaler / inverse unit by the aggregator (355) to generate output sample information (in this case, called residual samples or residual signals). The address in the reference picture memory form from which the motion-compensated unit fetches prediction samples may be controlled by motion vectors available to the motion-compensated unit in the form of symbols (321) which may have X, Y, and reference picture components, for example. Motion compensation may also include interpolation of sample values ​​fetched from the reference picture memory when the exact motion vectors of subsamples are used, motion vector prediction mechanisms, and so on.

[0030] The output samples of the aggregator (355) may be subject to various loop filtering techniques in the loop filter unit (356). The video compression technique may include in-loop filtering techniques that are controlled by parameters contained in the coded video bitstream and available in the loop filter unit (356) as symbols (321) from the parser (320), which may respond to metadata obtained during decoding of previous (in decoding order) portions of the coded picture or coded video sequence, or to previously reconstructed and loop-filtered sample values.

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

[0032] A particular coded picture, once fully reconstructed, can be used as a reference picture for future predictions. Once a coded picture is fully reconstructed and identified as a reference picture (e.g., by the parser (320)), the current reference picture (356) may become part of the reference picture buffer (357), and fresh current picture memory may be reallocated before the reconstruction of the next coded picture begins.

[0033] The video decoder 320 may perform decoding operations according to a predetermined video compression technique, which may be documented in standards such as ITU-T Rec.H.265. The encoded video sequence may conform to the syntax of the video compression technique or standard used, as specified in the video compression technique documentation or standard, and in particular to the syntax specified by the video compression technique or standard used, in the sense that it conforms to the profile documentation within it. Compliance is also required that the complexity of the encoded video sequence is within the range defined at the level of the video compression technique 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 limitations set by the level may, in some cases, be further limited by the Hypothetical Reference Decoder (HRD) specification and metadata for HRD buffer management signaled in the encoded video sequence.

[0034] In one embodiment, the receiver (310) may receive additional (redundant) data along with the encoded video. The additional data may be included as part of the encoded video sequence. The additional data may be used by the video decoder (320) to properly decode the data and / or more accurately reconstruct the original video data. The additional data may be in the form of, for example, a temporal, spatial, or SNR enhancement layer, redundant slices, redundant pictures, forward error correction codes, etc.

[0035] Figure 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 can capture video images to be encoded by the encoder (203).

[0037] The video source (201) may provide a source video sequence, encoded by the encoder (203), in the form of a digital video sample stream, which may have any suitable bit depth (e.g., 8 bits, 10 bits, 12 bits, ...), any color space (e.g., BT.601 Y CrCB, RGB, ...), and a suitable sampling structure (e.g., Y CrCb 4:2:0, Y CrCb 4:4:4). In a media serving system, the video source (201) may be a storage device that stores previously prepared video. In a video conferencing system, the video source (203) may be a camera that captures local image information as a video sequence. The video data may be provided as a series of separate pictures that, when viewed sequentially, give action. The picture itself can be organized as a spatial array of pixels, each pixel may contain 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. The following description will focus on samples.

[0038] According to one embodiment, the encoder (203) may encode pictures of a source video sequence in real time or under any other time constraints, as required by the application, and compress them into an encoded video sequence (443). Enforcing an appropriate coding speed is one function of the controller (450). The controller controls and is functionally coupled to other functional units, as described below. For simplicity, the couplings are not depicted. Parameters set by the controller may include rate control-related parameters (such as picture skipping, quantization, lambda values ​​for rate distortion optimization techniques), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. Those skilled in the art may relate to a video encoder (203) optimized for a particular system design, and other functions of the controller (450) will be readily identifiable.

[0039] Some video encoders operate in a manner readily recognizable to those skilled in the art as a “coding loop.” In an overly simplified explanation, the coding loop may consist of: an encoding portion of an encoder (430) (hereinafter, the “source coder”), responsible for creating symbols based on the input picture and reference picture to be coded; and a (local) decoder (433) embedded in the encoder (203), which creates sample data that reconstructs the symbols and also creates a (remote) decoder (since compression between the symbols and the coded video bitstream is reversible in the video compression techniques considered in the disclosed subject). The reconstructed sample stream is input to the reference picture memory (434). Because decoding the symbol stream yields bit-accurate results regardless of the decoder’s location (local or remote), the reference picture buffer content is also bit-accurate between the local and remote encoders. In other words, the predictive portion of the encoder “sees” the exact same sample values ​​as samples in the reference picture that the decoder “sees” when using predictions during decoding. This fundamental principle of reference picture synchronization (and the drift that occurs when synchronization cannot be maintained, for example, due to channel errors) is well known to those skilled in the art.

[0040] The operation of the “local” decoder (433) may be the same as that of the “remote” decoder (210), which has already been described in detail above in relation to Figure 3. However, also briefly referring to Figure 3, since symbols are available and the encoding / decoding of symbols to the encoded video sequence by the entropy coder (445) and parser (320) may be reversible, the entropy decoding portion of the decoder (210), including the channel (312), receiver (310), buffer (315), and parser (320), may not be fully implemented in the local decoder (433).

[0041] An observation that can be made at this point is that any decoder techniques present within the decoder, excluding parser / entropy decoding, must also exist in substantially the same functional form within the corresponding encoder. For this reason, the disclosed subject matter focuses on the operation of the decoder. The description of encoder techniques can be omitted as it is the inverse of the comprehensively described decoder techniques. More detailed explanations are required only in specific areas and are provided below.

[0042] As part of its operation, the source coder (430) may perform motion-compensated predictive coding, predictively coding the input frame by referencing one or more previously coded frames from a video sequence designated as “reference frames”. In this way, the coding engine (432) codes the difference between the pixel blocks of the input frame and the pixel blocks of the reference frame which may be selected as a predictive reference to the input frame.

[0043] The local video decoder (433) can decode the coded video data of a frame that may be designated as a reference frame based on symbols created by the source coder (430). It may be advantageous for the coding engine (432) to operate in a lossy manner. When coded video data can be decoded by a video decoder (not shown in Figure 4), the reconstructed video sequence may be a replica of the source video sequence, usually with some errors. The local video decoder (433) can replicate the decoding process that may be performed by the video decoder on the reference frame and store the reconstructed reference frame in the reference picture cache (434). In this way, the encoder (203) can locally store a copy of the reconstructed reference frame having common content as the reconstructed reference frame obtained by the far-end video decoder (when there are no transmission errors).

[0044] The predictor (435) may perform a predictive search of the coding engine (432). That is, for a new frame to be coded, the predictor (435) may search the reference picture memory (434) for specific metadata that can function as a suitable predictive reference for the new picture, such as motion vectors or block shapes of sample data or reference pictures (as candidate reference pixel blocks). The predictor (435) may operate sample block-pixel block by sample block to find a suitable predictive reference. In some cases, as determined by the search results obtained by the predictor (435), the input picture may have predictive 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 parameters and subgroup parameters used to encode video data.

[0046] The outputs of all the aforementioned functional units may undergo entropy coding in an entropy coder (445). The entropy coder converts the symbols generated by the various functional units into coded video sequences by lossless compression of the symbols according to techniques known to those skilled in the art, such as Huffman coding, variable-length coding, and arithmetic coding.

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

[0048] The controller (450) may manage the operation of the encoder (203). During coding, the controller (450) may assign a specific coded picture format to each coded picture, which may affect the coding technique that can be applied to each picture. For example, a picture may often be assigned as one of the following frame formats:

[0049] An intra-picture (I-picture) can be coded and decoded without using other frames in the sequence as a source for prediction. Some video codecs support various forms of intra-pictures, such as the Independent Decoder Refresh Picture. Those skilled in the art are aware of these variations of I-pictures and their respective uses and characteristics.

[0050] A predictive picture (P-picture) may be one that can be coded and decoded using intra-prediction or inter-prediction, which uses up to one motion vector and reference index to predict the sample values ​​for each block.

[0051] A bidirectional predictive picture (B-picture) may be one that can be coded and decoded using intra-prediction or inter-prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​for each block. Similarly, multiple predictive pictures may use three or more reference pictures and associated metadata for the reconstruction of a single block.

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

[0053] The video coder (203) may perform coding operations in accordance with a specified video coding technique or standard, such as ITU-T Rec.H.265. In these operations, the video coder (203) may perform various compression operations, including predictive coding operations that leverage the temporal and spatial redundancy of the input video sequence. Thus, the coded video data may conform to the syntax specified by the video coding technique or standard being used.

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

[0055] Before describing in more detail specific aspects of the disclosed subject matter, it is necessary to introduce some terms that will be referenced in the remainder of this description.

[0056] Hereinafter, a subpicture may refer to a rectangular arrangement of samples, blocks, macroblocks, coding units, or similar entities that are semantically grouped and can be coded independently at a modified resolution. A single picture may have one or more subpictures. One or more coded subpictures may form a coded picture. One or more subpictures can be assembled into a picture, and one or more subpictures can be extracted from a picture. In certain environments, one or more coded subpictures may be assembled in a compressed region without transcoding to a coded picture at the sample level. And in the same or certain other cases, one or more coded subpictures may be extracted from a coded picture in a compressed region.

[0057] Hereinafter, Adaptive Resolution Change (ARC) refers to a mechanism that allows for changes in the resolution of a picture or sub-picture within an encoded video sequence, for example, by resampling a reference picture. Hereinafter, ARC parameters refer to the control information required to perform Adaptive Resolution Change, which may include, for example, filter parameters, scaling factors, the resolution of the output picture and / or reference picture, and various control flags.

[0058] The above explanation focuses on coding and decoding a single, semantically independent coded video picture. Before discussing the implications of coding / decoding multiple subpictures with independent ARC parameters and the additional complexities that this implies, we can discuss the options for signaling ARC parameters.

[0059] Referring to Figure 5, several novel options for signaling ARC parameters are shown. As described for each option, they have specific advantages and disadvantages in terms of coding efficiency, complexity, and architecture. A video coding standard or technology may select one or more of these options, or options known from prior art, to signal ARC parameters. The options do not necessarily have to be mutually exclusive and may be interchangeable based on application needs, relevant standards, or encoder selection.

[0060] The classes of ARC parameters may include the following:

[0061] - Up / down sampling coefficients that separate or combine in the X and Y dimensions.

[0062] - An up / down sampling coefficient with an added time dimension, representing a constant zoom-in / out rate for a given number of pictures.

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

[0064] - The X-dimensional or Y-dimensional resolution of the input picture, output picture, reference picture, coded picture, combined picture, or separate, sample, block, macroblock, CU, or any other appropriate unit of granularity. If there are two or more resolutions (e.g., one for the input picture, one for the reference picture, etc.), in certain cases one set of values ​​may be inferred from another set of values. This can be gated, for example, by using flags. See below for more detailed examples.

[0065] - The "warping" coordinates are of appropriate granularity, as described above, similar to those used in H.263 Annex P. While H.263 Annex P defines one efficient method for coding such warping coordinates, other potentially more efficient methods are conceivable. For example, the variable-length reversible "Huffman" style coding of warping coordinates in Annex P can be replaced with a binary coding of appropriate length, the length of which can be derived, for example, from the maximum picture size, and possibly multiplied by a specific coefficient to shift by a certain value, thereby enabling "warping" beyond the boundaries of the maximum picture size.

[0066] - Upsampling filter parameters or downsampling filter parameters. In the simplest case, only a single filter for upsampling and / or downsampling may exist. However, in some cases, it may be advantageous to allow more flexibility in filter design, which may require signaling of filter parameters. Such parameters may be selected via an index in a list of possible filter designs, the filter may be fully specified (e.g., via a list of filter coefficients using appropriate entropy coding techniques), the filter may be implicitly selected via the up / downsampling ratio, the up / downsampling ratio being signaled according to one of the mechanisms described above, and so on.

[0067] In the following explanation, we assume the coding of up / downsampling coefficients (the same coefficients used in both the X and Y dimensions) for a finite set, indicated by a codeword. This codeword can, advantageously, be coded in variable length using Ext-Golomb coding, which is common to certain syntactic elements in video coding specifications such as H.264 and H.265. A suitable mapping of values ​​to up / downsampling coefficients can follow, for example, the table below.

[0068] [Table 1]

[0069] Many similar mappings can be devised depending on the application needs and the capabilities of the upscaling and downscaling mechanisms available in the video compression technology or standard. The table can be extended to more values. The values ​​may also be represented by an entropy coding mechanism other than the Ext-Golomb code, for example, using binary coding. This may have certain advantages when the resampling factor is of interest outside the video processing engine itself (the encoder and decoder are the foremost), as in MANE, for example. Note that in the (perhaps) most common case where resolution change is not required, a short Ext-Golomb code may be chosen. In the table above, this is only 1 bit. This may have an advantage in coding efficiency over using binary code in the most common case.

[0070] The number of entries in a table, as well as their semantics, can be fully or partially configurable. For example, the basic outline of a table may be communicated by a “high” parameter set, such as a sequence or decoder parameter set. Alternatively, or in addition, one or more such tables may be defined by a video coding technique or standard, and may be selected, for example, via a decoder or sequence parameter set.

[0071] The following explains how the upsampling / downsampling coefficients (ARC information), coded as described above, may be incorporated into video coding techniques or standard syntax. Similar considerations may apply to one or more codewords that control upsampling filters. For explanations regarding cases where filters or other data structures require relatively large amounts of data, see below.

[0072] H.263 Annex P includes ARC information 502 in the form of four warping coordinates within the picture header 501, specifically within the H.263 PLUSPTYPE(503) header extension. This can be a sensible design choice when a) there is a picture header available and b) frequent changes to the ARC information are expected. However, the overhead when using H.263-style signaling can be very high, and because picture headers can be transient, scaling factors may not be relevant between picture boundaries.

[0073] The JVCET-M 135-v1 cited above includes ARC reference information (505) (index) located within the picture parameter set (504) and indexes a table (506) containing target resolutions located within the sequence parameter set (507). The arrangement of possible resolutions in table (506) within the sequence parameter set (507) may be justified by using SPS as a point of negotiation for interoperability during capability exchange, in accordance with oral statements made by the authors. Resolutions may vary per picture within the limits set by the values ​​in table (506) by referencing the appropriate picture parameter set (504).

[0074] Referring further to Figure 5, the following additional options may exist for transmitting ARC information in the video bitstream. Each of these options has specific advantages over existing technologies, as described above. The options may coexist simultaneously in the same video coding technology or standard.

[0075] In one embodiment, ARC information (509), such as the resampling (zoom) coefficient, may reside in a slice header, GOB header, tile header, or tile group header (hereinafter, tile group header) (508). This may be appropriate when the ARC information is small, such as a single variable-length ue(v) or a fixed-length codeword of a few bits, as shown above. Having the ARC information directly within the tile group header has further advantages and may be applicable to subpictures represented by the tile group, rather than the entire picture. See also below. In addition, even if the video compression technology or standard assumes only whole-picture adaptive resolution changes (as opposed to tile group-based adaptive resolution changes, for example), placing the ARC information in the tile group header has certain advantages in terms of fault tolerance compared to placing it in an H.263-style picture header.

[0076] In the same or other embodiments, the ARC information (512) itself may reside in a suitable parameter set (511), such as a picture parameter set, a header parameter set, a tile parameter set, an adaptive parameter set, etc. (the adaptive parameter set shown in the figure). The scope of the parameter set may, advantageously, be limited to pictures, for example, tile groups. The use of the ARC information is implicitly performed by invoking the relevant parameter set. For example, if the video coding technique or standard intends only picture-based ARC, a picture parameter set or equivalent may be appropriate.

[0077] In the same or other embodiments, the ARC reference information (513) may reside in a tile group header (514) or a similar data structure. The reference information (513) may refer to a subset of the ARC information (515) available in a parameter set (516) that has a range beyond a single picture, for example, a sequence parameter set or a decoder parameter set.

[0078] The implicit activation of the indirect additional level of PPS from the tile group header, PPS, and SPS used in JVET-M 0135-v1 appears unnecessary, as picture parameter sets, like sequence parameter sets, can be used for capability negotiation or announcement (and have in certain standards such as RFC 3984). However, if the ARC information should be applicable to subpictures that are also represented by tile groups, for example, then a parameter set with an activation scope limited to tile groups, such as an adaptation parameter set or header parameter set, might be a better choice. Also, if the ARC information is of a significant size, for example, if it contains filter control information such as a large number of filter coefficients, then parameters might be a better choice from a coding efficiency standpoint than using the header (508) directly, because these settings can be reused by future pictures or subpictures by referencing the same parameter set.

[0079] Certain considerations may apply when using a sequence parameter set or another higher parameter set with a scope spanning multiple pictures.

[0080] 1. The parameter set for storing the ARC information table (516) may in some cases be a sequence parameter set, but in other cases a decoder parameter set is preferable. A decoder parameter set can have multiple CVSs, i.e., coded video streams, i.e., activation ranges of all coded video bits from the start to the end of the session. Such a range may be more appropriate because the possible ARC factors may be decoder functions implemented in hardware, and hardware functions tend not to change with CVSs (at least in some entertainment systems, they are Groups of Pictures of less than half their length). Nevertheless, placing the table in a sequence parameter set is clearly included in the arrangement options described herein, particularly in relation to point 2 below.

[0081] 2. ARC reference information (513) may, advantageously, be placed directly within the picture / slice tile / GOB / tile group header (hereinafter, tile group header) (514) rather than within the picture parameter set, as in JVCET-M 0135-v1. The reason is that if the encoder wants to change a single value in the picture parameter set, such as ARC reference information, it would need to create a new PPS and reference that new PPS. Suppose only the ARC reference information changes, while other information, such as quantization matrix information in the PPS, remains. Such information can be quite large and would need to be retransmitted to complete the new PPS. ARC reference information may be a single codeword, such as an index to the table (513), and since it is the only value that changes, retransmitting all of the quantization matrix information, for example, would be cumbersome and wasteful. To that extent, avoiding the indirectness through the PPS, as proposed in JVET-M 0135-v1, can be quite good from the standpoint of coding efficiency. Similarly, including ARC reference information in the PPS has a further drawback: since the scope of Picture Parameter Set Activation is the picture, the ARC information referenced by ARC reference information (513) must necessarily apply to the entire picture, not just the subpictures.

[0082] In the same or other embodiments, the signaling of ARC parameters may follow a detailed example outlined in Figure 6. Figure 6 shows a syntax diagram of the representation used in video coding standards since at least 1993. The notation of such a syntax diagram broadly follows C-style programming. Bold lines indicate syntax elements present in the bitstream, while non-bold lines often indicate control flow or variable settings.

[0083] A tile group header (601), as an exemplary syntax structure for a header applicable to a portion of a picture (possibly a rectangular portion), can conditionally contain a variable-length Exp-Golomb coded syntax element dec_pic_size_idx (602) (shown in bold). The presence of this syntax element within the tile group header can be gated using an adaptive resolution (603), a flag value not shown in bold here, which means the flag is present in the bitstream at the point where it occurs in the syntax diagram. Whether or not an adaptive resolution is used for this picture or a portion of it can be signaled by any high-level syntax structure inside or outside the bitstream. In the example shown, it is signaled by a set of sequence parameters as outlined below.

[0084] Continuing to refer to Figure 6, an excerpt of the sequence parameter set (610) is also shown. The first syntax element shown is adaptive_pic_resolution_change_flag (611). If true, the flag can indicate the use of adaptive resolution, which may require certain control information. In this example, such control information exists conditionally, based on the value of the flag based on the if() statement in the parameter set (612) and the tile group header (601).

[0085] When adaptive resolution is used, in this example, what is coded is the output resolution in samples (613). Reference numeral 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. Elsewhere in the video coding technique or standard, specific limitations may be defined on either value. For example, a level definition may limit the total number of output samples, which can be the product of the values ​​of those two syntax elements. Also, a particular video coding technique or standard, or an external technique or standard such as a system standard, may limit the range of numbering (e.g., one or both dimensions must be divisible by a power of 2) or the aspect ratio (e.g., width and height must be in a relationship such as 4:3 or 16:9). Such limitations may be introduced to facilitate hardware implementation or for other reasons and are well known in the art.

[0086] For certain applications, it may be desirable for the encoder to instruct the decoder to use a specific reference picture size rather than implicitly assuming that the size is the output picture size. In this example, the syntax element reference_pic_size_present_flag(614) gates the conditional existence of reference picture dimensions(615) (again, the numbers refer to both width and height).

[0087] Finally, a table of possible decoded picture widths and heights is shown. Such a table can be represented, for example, by the table directive (num_dec_pic_size_in_luma_samples_minus1)(616), where "minus1" can refer to the interpretation of the value of its syntax element. For example, if the coded value is 0, there is one table entry. If the value is 5, there are six table entries. For each "line" in the table, the decoded picture width and height are contained in syntax(617).

[0088] The presented table entries (617) can be indexed using the syntax element dec_pic_size_idx (602) within the tile group header, thereby allowing for different decode sizes, or in other words, zoom levels, for each tile group.

[0089] For example, certain video coding techniques or standards, such as VP9, ​​support spatial extensibility by performing a form of reference picture resampling (signaled entirely differently from the disclosed subject) in conjunction with temporal extensibility to enable spatial extensibility. In particular, specific reference pictures can be upsampled to a higher resolution using ARC-style techniques to form the base of a spatial enhancement layer. These upsampled pictures can then be refined at high resolution using conventional predictive mechanisms to add detail.

[0090] The disclosed subject matter can be used in such environments. In some cases, and in the same or other embodiments, spatial layers as well as temporal layers can be indicated using values ​​in the NAL unit header, such as the time ID field. Doing so has certain advantages in certain system designs. For example, an existing selective transfer unit (SFU) created and optimized for temporal layer selective transfer based on the NAL unit header time ID value can be used without modification for scalable environments. To enable this, there may be requirements for mapping between coded picture sizes and temporal layers, which are indicated by the time ID field in the NAL unit header.

[0091] In some video coding techniques, an Access Unit (AU) can refer to coded pictures, slices, tiles, NAL units, etc., that are captured and configured within the respective picture / slice / tile / NAL unit bitstream in a given instance at time. That instance at time may be composite time.

[0092] In HEVC and certain other video coding techniques, a Picture Order Count (POC) value can be used to indicate a selected reference picture from among multiple reference pictures stored in a Decode Picture Buffer (DPB). If an Access Unit (AU) contains one or more pictures, slices, or tiles, each picture, slice, or tile belonging to the same AU can have the same POC value, from which it can be deduced that they were created from content of the same composition time. In other words, in a scenario where two pictures / slices / tiles carry the same given POC value, it can indicate two pictures / slices / tiles belonging to the same AU and having the same composition time. Conversely, two pictures / tiles / slices with different POC values ​​can indicate those pictures / slices / tiles belonging to different AUs and having different composition times.

[0093] In one embodiment of the disclosed subject matter, the aforementioned strict relationship can be relaxed in that an access unit may include pictures, slices, or tiles having different POC values. By allowing different POC values ​​within an AU, it becomes possible to use the POC values ​​to identify potentially independently decodeable pictures / slices / tiles having the same presentation time. This makes it possible to support multiple scalable layers without changing the reference picture selection signaling (e.g., reference picture set signaling or reference picture list signaling), as will be described in more detail below.

[0094] 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, based solely on the POC value. This can be achieved as described below.

[0095] In the same or other embodiments, the access unit count (AUC) may be signaled in high-level syntactic structures such as NAL unit headers, slice headers, tile group headers, SEI messages, parameter sets, or AU delimiters. The AUC value may be used to identify which NAL unit, picture, slice, or tile belongs to a given AU. The AUC value may correspond to a separate synthesis time instance. The AUC value may be equal to a multiple of the POC value. The AUC value can be calculated by dividing the POC value by an integer value. In some cases, the division operation may impose a certain burden on the decoder implementation. In such cases, the division operation can be replaced with a shift operation because the constraints on the numbering space of the AUC value are small. For example, the AUC value may be equal to the most significant bit (MSB) value of the POC value range.

[0096] In the same embodiment, the POC cycle value for each AU (poc_cycle_au) may be signaled in a high-level syntactic structure such as a NAL unit header, slice header, tile group header, SEI message, parameter set, or AU delimiter. poc_cycle_au can indicate how many different consecutive POC values ​​can be associated with the same AU. For example, if the value of poc_cycle_au is equal to 4, then pictures, slices, or tiles with POC values ​​between 0 and -3 are associated with AUs with AUC values ​​equal to 0, and pictures, slices, or tiles with POC values ​​between 4 and -7 are associated with AUs with AUC values ​​equal to 1. Thus, the AUC value can be estimated by dividing the POC value by the value of poc_cycle_au.

[0097] In the same or other embodiments, the value of poc_cycle_au may be derived from information identifying the number of spatial or SNR layers in the coded video sequence, for example, located in the video parameter set (VPS). A brief description of such a relationship follows. While the derivation described above can save a few bits in the VPS and thus improve coding efficiency, it may be advantageous to explicitly encode poc_cycle_au in a hierarchically appropriate high-level syntax structure below the video parameter set to minimize poc_cycle_au for a given small portion of a bitstream, such as a picture. This optimization can save more bits than can be saved through the above derivation process, because the POC value (and / or the value of a syntax element that indirectly references the POC) can be encoded in a low-level syntax structure.

[0098] The above-described techniques for signaling adaptive resolution parameters can be implemented as computer software using computer-readable instructions and can be physically stored on one or more computer-readable media. For example, Figure 7 shows a computer system 700 suitable for implementing a particular embodiment of the disclosed subject.

[0099] Computer software can be coded using any suitable machine code or computer language, and is subject to assembly, compilation, linking, or similar mechanisms, creating code that contains instructions that can be executed directly by a computer's central processing unit (CPU), graphics processing unit (GPU), etc., or through interpretation, microcode execution, etc.

[0100] The instructions can be executed on various types of computers or their components, including, for example, personal computers, tablet computers, servers, smartphones, game consoles, and Internet of Things devices.

[0101] The components of the computer system 700 shown in Figure 7 are illustrative in nature and are not intended to imply any limitation on the scope of use or functionality of computer software implementing embodiments of the present disclosure. Furthermore, the configuration of the components should not be construed as having any dependence or requirement on any one or combination of components shown in the exemplary embodiments of the computer system 700.

[0102] The computer system 700 may include certain human interface input devices. Such human interface input devices may respond to input from one or more users, such as tactile input (keystrokes, swipes, data glove movements, etc.), voice input (voice, applause, etc.), visual input (gestures, etc.), and olfactory input (not shown). The human interface device may also be used to capture certain media that are not necessarily directly related to conscious human input, such as voice (speech, music, ambient sounds, etc.), images (scanned images, photographic images obtained from still image cameras, etc.), and video (2D video, 3D video including stereoscopic video, etc.).

[0103] The input human interface device may include one or more of the following (only one of each as shown): keyboard 701, mouse 702, trackpad 703, touchscreen 710, data glove 704, joystick 705, microphone 706, scanner 707, and camera 708.

[0104] The computer system 700 may also include certain human interface output devices. Such human interface output devices can stimulate the senses of one or more human users, for example, by tactile output, sound, light, and smell / taste. Such human interface output devices may include tactile output devices (e.g., tactile feedback by touchscreen 710, data glove 704, or joystick 705, but there may also be tactile feedback devices that do not function as input devices), audio output devices (e.g., speaker 709, headphones (not shown)), visual output devices (screens 710 including CRT screens, LCD screens, plasma screens, OLED screens, etc., each with or without touchscreen input functionality, each with or without tactile feedback functionality, some of which can output two-dimensional visual output or three-dimensional or more output by means such as stereographic output, virtual reality glasses (not shown), holographic displays, and smoke tanks (not shown)), and printers (not shown).

[0105] The computer system 700 may also include human-accessible storage devices and related media such as optical media 721 including CD / DVD ROM / RW 720, thumb drives 722, removable hard drives or solid-state drives 723, legacy magnetic media such as tapes and floppy disks (not shown), and dedicated ROM / ASIC / PLD-based devices such as security dongles (not shown).

[0106] Those skilled in the art should also understand that the term “computer-readable medium” as used in connection with the subject matter disclosed herein does not include a transmission medium, carrier wave, or other transient signal.

[0107] The computer system 700 may also include interfaces to one or more communication networks. These networks may be, for example, wireless, wired, or optical. Networks may further be local, wide-area, metropolitan, automotive, and industrial, real-time, or latency-tolerant. Examples of networks include local area networks such as cellular networks including Ethernet, Wi-Fi, GSM, 3G, 4G, 5G, and LTE; wired or wireless wide-area digital networks including cable television, satellite television, and terrestrial television; and automotive and industrial networks including CANBus. Certain networks generally require an external network interface adapter connected to a specific general-purpose data port or peripheral bus (749) (e.g., a USB port on the computer system 700), while others are generally integrated into the core of the computer system 700 by connecting to a system bus, as described below (e.g., an Ethernet 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 communications can be one-way, receive only (e.g., broadcast television), one-way transmit only (e.g., from a CANbus to a specific CANbus device), or two-way, for example, to another computer system using a local area digital network or a wide area digital network. Specific protocols and protocol stacks can be used on each of those networks and network interfaces, as described above.

[0108] The aforementioned human interface device, human-accessible storage device, and network interface can be connected to the core 740 of the computer system 700.

[0109] The core 740 may include one or more central processing units (CPUs) 741, graphics processing units (GPUs) 742, field-programmable gate areas (FPGAs) 743, and specialized programmable processing units such as hardware accelerators 744 for specific tasks. These units may be connected via a system bus 748, along with read-only memory (ROM) 745, random access memory 746, and internal mass storage devices 747 such as internal hard drives and SSDs that are not accessible to the user. In some computer systems, the system bus 748 can be accessed in the form of one or more physical plugs to enable expansion with additional CPUs, GPUs, etc. Peripheral devices can be connected directly to the core's system bus 748 or via a peripheral bus 749. Peripheral bus architectures include PCI, USB, etc.

[0110] The CPU 741, GPU 742, FPGA 743, and accelerator 744 can execute specific instructions that, when combined, constitute the aforementioned computer code. This computer code can be stored in ROM 745 or RAM 746. Transitional data can also be stored in RAM 746, while persistent data can be stored, for example, in internal mass storage device 747. By using cache memory that can be closely associated with one or more CPUs 741, GPUs 742, mass storage devices 747, ROM 745, RAM 746, etc., high-speed storage and retrieval to any memory device becomes possible.

[0111] A computer-readable medium may contain computer code for performing various computer implementation operations. The medium and computer code may be specifically designed and constructed for the purposes of this disclosure, or they may be in a format well known and available to those skilled in the computer software technology.

[0112] As an example, and not an limitation, a computer system having architecture 700, in particular core 740, can provide functionality as a result of a processor (including CPUs, GPUs, FPGAs, accelerators, etc.) that runs software embedded in one or more tangible computer-readable media. Such computer-readable media may be user-accessible mass storage devices as described above, and media associated with specific storage devices of core 740 that have a non-transient nature, such as the core internal mass storage device 747 or ROM 745. Software implementing various embodiments of this disclosure may be stored in such devices and executed by core 740. The computer-readable media may include one or more memory devices or chips according to specific needs. The software may cause core 740, in particular the processor within it (including CPUs, GPUs, FPGAs, etc.), to perform specific operations or specific parts of specific operations described herein, including defining data structures stored in RAM 746 and modifying such data structures according to software-defined operations. In addition, or alternatively, a computer system may provide functionality as a result of logic embodied in a circuit (e.g., accelerator 744) in a logic hardwired or otherwise manner, and may perform specific processes or specific parts of specific processes described herein, instead of or in conjunction with software. References to software may include logic, and vice versa, as appropriate. References to computer-readable media may, as necessary, include circuits that store software for execution (such as integrated circuits (ICs)), circuits that embody logic for execution, or both. This disclosure encompasses any suitable combination of hardware and software.

[0113] Figure 8 shows an example of a video sequence structure with a combination of temporal_id, layer_id, POC, and AUC values, accompanied by adaptive resolution changes. In this example, a picture, slice, or tile in a first AU with AUC=0 can have temporal_id=0 and layer_id=0 or 1, while a picture, slice, or tile in a second AU with AUC=1 can have temporal_id=1 and layer_id=0 or 1, respectively. Regardless of the values ​​of temporal_id and layer_id, the POC value increases by 1 for each picture. In this example, the value of poc_cycle_au can be equal to 2. Preferably, the value of poc_cycle_au may be set to be equal to the number of (spatially expandable) layers. Thus, in this example, the POC value increases by 2 and the AUC value increases by 1.

[0114] In the embodiments described above, all or a subset of the picture- or layer-based prediction structures and reference picture indications may be supported by using existing reference picture set (RPS) signaling or reference picture list (RPL) signaling in HEVC. In RPS or RPL, a selected reference picture is indicated by signaling the POC value or the delta value of the POC between the current picture and the selected reference picture. For the disclosed subject matter, RPS and RPL may be used to indicate picture- or layer-based prediction structures without modifying the signaling, but subject to the following limitations: If the value of the reference picture's temporal_id is greater than the value of the current picture's temporal_id, the current picture may not use the reference picture for motion compensation or other predictions. If the value of the reference picture's layer_id is greater than the value of the current picture's layer_id, the current picture may not use the reference picture for motion compensation or other predictions.

[0115] In this embodiment and other embodiments, scaling of motion vectors based on POC differences for temporal motion vector prediction can be disabled across multiple pictures within an access unit. Thus, each picture may have a different POC value within the access unit, but the motion vector is not scaled and is not used for temporal motion vector prediction within the access unit. This is because reference pictures with different POCs within the same AU are considered to be reference pictures having the same time instance. Therefore, in this embodiment, the motion vector scaling function can return 1 if the reference picture belongs to the AU currently associated with the picture.

[0116] In the same and other embodiments, if the spatial resolution of the reference picture differs from that of the current picture, the scaling of motion vectors based on the POC difference for time motion vector prediction can be optionally disabled across multiple pictures. When motion vector scaling is permitted, the motion vectors are scaled based on both the POC difference and the spatial resolution ratio between the current picture and the reference picture.

[0117] In the same or other embodiments, the motion vector may be scaled based on the AUC difference rather than the POC difference for temporal motion vector prediction, particularly when poc_cycle_au has non-uniform values ​​(when vps_contant_poc_cycle_per_au == 0). Otherwise (when vps_contant_poc_cycle_per_au == 1), scaling the motion vector based on the AUC difference may be identical to scaling the motion vector based on the POC difference.

[0118] In the same or other embodiments, when motion vectors are scaled based on the AUC difference, a reference motion vector within the same AU (having the same AUC value) as 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.

[0119] In the same and other embodiments, the AUC value is used to identify the boundaries of the AU and for virtual reference decoder (HRD) operation that requires input and output timings with AU granularity. In most cases, the decoded picture with the top layer in the AU may be output for display. The AUC value and layer_id value can be used to identify the output picture.

[0120] In one embodiment, a picture may consist of one or more subpictures. Each subpicture may cover the local area or the entire area of ​​the picture. The area supported by a subpicture may or may not overlap with the area supported by another subpicture. The area composed of one or more subpictures may or may not cover the entire area of ​​the picture. If the picture consists of subpictures, the area supported by a subpicture is the same as the area supported by the picture.

[0121] In the same embodiment, a subpicture may be coded by a coding method similar to the coding method used for the coded picture. A subpicture may be coded independently or may be coded in dependence of another subpicture or coded picture. A subpicture may or may not have syntax analysis dependencies from another subpicture or coded picture.

[0122] In the same embodiment, coded subpictures may be contained in one or more layers. Coded subpictures within a layer may have different spatial resolutions. The original subpicture may be spatially resampled (upsampled or downsampled), coded with different spatial resolution parameters, and contained in the bitstream corresponding to the layer.

[0123] In the same embodiment or other embodiments, a subpicture having (W, H), where W represents the width of the subpicture and H represents the height of the subpicture, can be included in the encoded bitstream corresponding to layer 0, while a subpicture upsampled (or downsampled) from a subpicture having the original spatial resolution of (W*S w、k , H*S h、k ) can be included in the encoded bitstream corresponding to layer k, and S w、k , S h、k represent the resampling ratios in the horizontal and vertical directions. S w、k , S h、k being greater than 1 means the resampling is equal to upsampling. On the other hand, when the value of S w、k , S h、k is less than 1, the resampling is equal to downsampling.

[0124] In the same or other embodiments, the encoded subpictures within a layer can have a different visual quality from the encoded subpictures within another layer in the same or different subpictures. For example, subpicture i within layer n is encoded with quantization parameter Q i、n , and subpicture j within layer m is encoded with quantization parameter Q j、m .

[0125] In the same or other embodiments, coded subpictures within a layer may be decodeable independently without any syntax analysis or decoding dependencies from coded subpictures in other layers within the same local region. A subpicture layer that can be decoded independently without referring to another subpicture layer within the same local region is an independent subpicture layer. Coded subpictures within an independent subpicture layer may or may not have decoding or syntax analysis dependencies from previously coded subpictures within the same subpicture layer, but coded subpictures may not have any dependencies from coded pictures in other subpicture layers.

[0126] In the same or other embodiments, coded subpictures within a layer may be dependently decodeable with any syntax analysis or decoding dependency from coded subpictures in other layers in the same local region. A subpicture layer that may be dependently decodeable by referencing another subpicture layer in the same local region is a dependent subpicture layer. Coded subpictures within a dependent subpicture may reference coded subpictures belonging to the same subpicture, previously coded subpictures within the same subpicture layer, or both reference subpictures.

[0127] In the same or other embodiments, the coded subpicture consists of one or more independent subpicture layers and one or more dependent subpicture layers. However, there may be at least one independent subpicture layer for the coded subpicture. An independent subpicture layer may have a layer identifier (layer_id) value equal to 0, which may be present in the NAL unit header or another higher-level syntax structure. The subpicture layer with layer_id equal to 0 is the base subpicture layer.

[0128] In the same or other embodiments, a picture may consist of one or more foreground subpictures and one background subpicture. The area supported by the background subpicture may be equal to the area of ​​the picture. The area supported by the foreground subpicture may overlap with the area supported by the background subpicture. The background subpicture may be a base subpicture layer, and the foreground subpicture may be a non-base (enhancement) subpicture layer. One or more non-base subpicture layers may refer to the same base layer for decoding. Each non-base subpicture layer with layer_id equal to a may refer to 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 a background subpicture. 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.

[0130] In the same or other embodiments, a picture may consist of one or more foreground subpictures, with or without background subpictures. Each coded subpicture within a (base or non-base) subpicture layer may be referenced by one or more non-base layer subpictures belonging to the same subpicture and one or more non-base layer subpictures not belonging to the same subpicture.

[0131] 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 divided into multiple subpictures within the same layer. One or more coded subpictures in layer b may refer to divided subpictures in layer a.

[0132] In the same or other embodiments, the coded video sequence (CVS) may be a group of coded pictures. The CVS may consist of one or more coded subpicture sequences (CSPS), which may be a group of coded subpictures covering the same local area of ​​a picture. The CSPS may have the same or different temporal resolution as the coded video sequence.

[0133] In the same or other embodiments, the CSPS may be coded and contained in one or more layers. The CSPS may consist of one or more CSP layers. Decoding one or more CSP layers corresponding to the CSPS allows for the reconstruction of a sequence of subpictures corresponding to the same local region.

[0134] In the same or other embodiments, the number of CSP layers corresponding to a CSPS may be the same as or different from the number of CSP layers corresponding to another CSPS.

[0135] In the same or other embodiments, a CSP layer may have a different temporal resolution (e.g., frame rate) than another CSP layer. The original (uncompressed) subpicture sequence may be resampled in time (upsampled or downsampled), coded with different temporal resolution parameters, and included in the bitstream corresponding to the layer.

[0136] In the same or other embodiments, a subpicture sequence having a frame rate F may be encoded and included in the encoded bitstream corresponding to layer 0, F*S t、k A temporally upsampled (or downsampled) subpicture sequence from the original subpicture sequence having S may be encoded and included in the encoded bitstream corresponding to layer k, t、k This indicates the time sampling ratio of layer k. t、k If the value of is greater than 1, the temporal resampling process is equivalent to a frame rate up conversion. On the other hand, S t、k If the value is less than 1, the temporal resampling process is equivalent to a frame rate downconversion.

[0137] In the same or other embodiments, when a subpicture having CSP layer a is referenced by a subpicture having CSP layer b for motion compensation or arbitrary inter-layer prediction, if the spatial resolution of CSP layer a differs from that of CSP layer b, the decoded pixels in CSP layer a are resampled and used for reference. The resampling process may require upsampling filtering or downsampling filtering.

[0138] In the same or other embodiments, Figure 9 shows an example syntax table for signaling the syntax element of vps_poc_cycle_au in the VPS (or SPS), which indicates the poc_cycle_au used for all pictures / slices in the coded video sequence, and the syntax element of slice_poc_cycle_au, which indicates the poc_cycle_au of the current slice in the slice header. If the POC value increases uniformly per AU, vps_contant_poc_cycle_per_au in the VPS is set 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 per AU is calculated by dividing the POC value by vps_poc_cycle_au. If the POC value does not increase uniformly per AU, vps_contant_poc_cycle_per_au in the VPS is set to 0. In this case, vps_access_unit_cnt is not signaled, and slice_access_unit_cnt is signaled in the slice header for each slice or picture. Each slice or picture may have a different slice_access_unit_cnt value. The AUC value per AU is calculated by dividing the POC value by slice_poc_cycle_au. Figure 10 shows a block diagram illustrating the relevant workflow.

[0139] In the same or other embodiments, even if the POC values ​​of the pictures, slices, or tiles are different, pictures, slices, or tiles corresponding to an AU with the same AUC value can be associated with the same decoding or output time instance. Therefore, all or a subset of pictures, slices, or tiles associated with the same AU can be decoded in parallel and output simultaneously without dependencies between syntax analysis / decoding across pictures, slices, or tiles within the same AU.

[0140] In the same or other embodiments, even if the POC values ​​of the pictures, slices, or tiles are different, pictures, slices, or tiles corresponding to AUs with the same AUC value may be associated with the same composite / display time instance. If the composite time is included in the container format, even if the pictures correspond to different AUs, if the pictures have the same composite time, those pictures may be displayed in the same time instance.

[0141] In the same or other embodiments, each picture, slice, or tile may have the same temporal identifier (temporal_id) within the same AU. All or a subset of pictures, slices, or tiles corresponding to a time instance may be associated with the same time sublayer. In the same or other embodiments, each picture, slice, or tile may have the same or different spatial layer ID (layer_id) within 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 layer.

[0142] Figure 11 shows an exemplary video stream containing a background video CSPS with layer_id equal to 0 and multiple foreground CSP layers. Encoded subpictures may consist of one or more CSP layers, while background areas not belonging to any foreground CSP layer may consist of a base layer. The base layer may contain both background and foreground areas, while the enhancement CSP layer contains only the foreground area. The enhancement CSP layer may have better visual quality than the base layer in the same area. The enhancement CSP layer may reference reconstructed pixels and motion vectors from the base layer corresponding to the same area.

[0143] In the same or other embodiments, the video bitstream corresponding to the base layer is contained in a track, and the CSP layers corresponding to each subpicture are contained in separate tracks within the video file.

[0144] In the same or other embodiments, the video bitstream corresponding to the base layer is included in a track, and the CSP layers having the same layer_id are included in separate tracks. In this example, the track corresponding to layer k includes only the CSP layer corresponding to layer k.

[0145] In the same or other embodiments, each CSP layer of each subpicture is stored in a separate track. Each track may or may not have any syntax analysis or decoding dependencies from one or more other tracks.

[0146] In the same or other embodiments, each track can include a bitstream corresponding to layer i to layer j of all or a subset of the CSP layers of the subpicture, where 0 < i <= j <= k and k is the top layer of the CSPSs.

[0147] 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 time-limited media data can be divided into one or more data substreams each corresponding to one subpicture.

[0148] In the same or other embodiments, Figure 12 shows an example of video conferencing based on a multi-layer subpicture method. The video stream includes one base layer video bitstream corresponding to the background picture and one or more enhancement layer video bitstreams corresponding to the foreground subpictures. Each enhancement layer bitstream corresponds to a CSP layer. On the display, the picture corresponding to the base layer is displayed by default. This includes picture-in-picture (PIP) for one or more users. When a specific user is selected by client control, the enhancement CSP layer corresponding to the selected user is decoded and displayed at enhanced quality or spatial resolution. Figure 13 shows a diagram for operation.

[0149] In the same or other embodiments, a network intermediate box (such as a router) may select a subset of layers to send to a user depending on its bandwidth. Picture / subpicture organization may be used for bandwidth adaptation. For example, if a user has limited bandwidth, the router may remove layers or select some subpictures based on their importance or the configuration used, and this can be done dynamically to accommodate the bandwidth.

[0150] Figure 14 illustrates a use case for 360 video. When a spherical 360 picture is projected onto a planar picture, the projected 360 picture may be divided into multiple subpictures as a base layer. Enhancement layers for specific subpictures may be coded and sent to the client. The decoder can decode both the base layer containing all subpictures and the enhancement layers of selected subpictures. If the current viewport is identical to the selected subpicture, the displayed picture may have higher quality with the decoded subpictures that have the enhancement layers. Otherwise, the decoded picture with the base layer may be displayed at lower quality.

[0151] In the same or other embodiments, any layout information for display may be present in the file as auxiliary information (such as SEI messages or metadata). One or more decoded subpictures may be rearranged and displayed according to the signaled layout information. The layout information may be signaled by a streaming server or broadcaster, regenerated by a network entity or cloud server, or determined by user-customized settings.

[0152] In one embodiment, if 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, picture size (width, height) and upper-left corner offset information (x_offset, y_offset). Figure 15 shows an example of the layout of divided sub-pictures, their sub-picture size and position information, and their corresponding picture prediction structure. Layout information, including sub-picture size(s) and sub-picture position(s), may be signaled by parameter sets(s), slice or tile group headers, or high-level syntactic structures such as SEI messages.

[0153] In the same embodiment, each subpicture corresponding to an independent layer may have its own unique POC value within the AU. When a reference picture among the pictures stored in the DPB is indicated using a syntax element of the RPS or RPL structure, the POC value of each subpicture corresponding to the layer may be used.

[0154] In the same or other embodiments, the layer_id may not be used to indicate the (inter-layer) prediction structure, and a POC (delta) value may be used instead.

[0155] In the same embodiment, a subpicture 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 a subpicture having a POC value equal to N+K corresponding to the same layer (or the same local region) for motion compensation prediction. In most cases, the value of K may be equal to the maximum number of (independent) layers, which may be the same as the number of subregions.

[0156] In the same or other embodiments, Figure 16 shows an extended case of Figure 15. When the input picture is divided into multiple (e.g., four) subregions, 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 subregions, and one or more layers may correspond to subregions. Thus, each subregion may be coded with one or more independent layers and zero or more independent layers.

[0157] In the same embodiment, in Figure 16, the input picture may be divided into four sub-regions. The upper right sub-region may be coded as two layers, Layer 1 and Layer 4, and the lower right sub-region may be coded as two layers, Layer 3 and Layer 5. In this case, Layer 4 can refer to Layer 1 for motion compensation prediction, and Layer 5 can refer to Layer 3 for motion compensation.

[0158] In the same or other embodiments, in-loop filtering across layer boundaries (such as deblocking filters, adaptive in-loop filters, reshapers, bilateral filters, or any deep learning-based filtering) can be (optionally) disabled.

[0159] In the same or other embodiments, motion compensation prediction or intrablock copying across layer boundaries can be (optionally) disabled.

[0160] In the same or other embodiments, boundary padding for motion compensation prediction or in-loop filtering at the boundaries of subpictures may be processed optionally. A flag indicating whether boundary padding is processed can be signaled in a parameter set (VPS, SPS, PPS, or APS), a slice or tile group header, or a high-level syntactic structure such as an SEI message.

[0161] 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 the syntax elements for the VPS and SPS. In this example, the VPS signals the vps_sub_picture_dividing_flag. The flag can indicate whether or not an input picture is divided into multiple sub-regions. When 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 does not need to be divided into multiple sub-regions. In this case, the input picture size may be equal to the coded picture size (pic_width_in_luma_samples, pic_height_in_luma_samples) signaled in the SPS. When 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_samples are signaled in the VPS. The values ​​of vps_full_pic_width_in_luma_samples and vps_full_pic_height_in_luma_samples may be equal to the width and height of the input picture, respectively.

[0162] 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 composition and display.

[0163] In the same embodiment, when the value of vps_sub_picture_dividing_flag is equal to 1, the syntax elements pic_offset_x and pic_offset_y may (a) be signaled in the SPS corresponding to a particular layer(s). In this case, the coded picture size (pic_width_in_luma_samples, pic_height_in_luma_samples) signaled in the SPS may be equal to the width and height of the sub-region corresponding to the particular layer. The position of the upper-left corner of the sub-region (pic_offset_x, pic_offset_y) may also be signaled in the SPS.

[0164] In the same embodiment, the position information of the upper left corner of the subregion (pic_offset_x, pic_offset_y) may not be used for decoding, but may be used for composition and display.

[0165] In the same or other embodiments, layout information (size and position) of all or a subset of sub-regions of an input picture, and dependency information between layers, may be signaled in a parameter set or SEI message. Figure 18 shows an example of syntax elements that indicate information about the layout of sub-regions, dependencies between layers, and relationships between sub-regions and one or more layers. In this example, the syntax element num_sub_region indicates the number of (rectangular) sub-regions 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 sub-region is coded as a single layer, the value of num_layers may be equal to the value of num_sub_region. When one or more sub-regions are coded as multiple layers, the value of num_layers may be greater than the value of num_sub_region. The syntax element direct_dependency_flag[i][j] indicates the dependency from the j-th layer to the i-th 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.

[0166] In one embodiment, one or more syntax elements that specify an output layer, configured to indicate one of a plurality of layers to be output with or without profile tier layer level information, may be signaled in a high-level syntax structure, such as a VPS, DPS, SPS, PPS, APS, or SEI message. Referring to Figure 19, the syntax element num_output_layer_sets, which indicates the number of output layer sets (OLS) in an encoded video sequence referencing a VPS, may be signaled in the VPS. For each output layer set, the same number of output_layer_flags as the number of output layers may be signaled.

[0167] In the same embodiment, output_layer_flag[i] equal to 1 specifies that the i-th layer is output. vps_output_layer_flag[i] equal to 0 specifies that the i-th layer is not output.

[0168] In the same or other embodiments, one or more syntax elements specifying profile tier level information for each output layer set may be signaled in a high-level syntax structure, such as VPS, DPS, SPS, PPS, APS, or SEI messages. Furthermore, referring to Figure 19, a syntax element num_profile_tile_level indicating the number of profile tier level pieces per OLS in a coded video sequence referencing a VPS may be signaled within the VPS. For each output layer set, a set of syntax elements for profile tier level information, or an index indicating a specific profile tier level piece among the entries within the profile tier level information, may be signaled as many times as there are output layers.

[0169] In the same embodiment, profile_tier_level_idx[i][j] specifies the index of the profile_tier_level() syntax structure that applies to the j-th layer of the i-th OLS within the list of profile_tier_level() syntax structures in the VPS.

[0170] In the same or other embodiments, referring to Figure 20, if the maximum number of layers is greater than 1 (vps_max_layers_minus1>0), the syntax elements num_profile_tile_level and / or num_output_layer_sets may be signaled.

[0171] In the same or other embodiments, referring to Figure 20, a syntax element vps_output_layers_mode[i] indicating the mode of output layer signaling for the i-th set of output layers may exist within the VPS.

[0172] In the same embodiment, a vps_output_layers_mode[i] equal to 0 specifies that only the top layer in the i-th output layer set is output. A vps_output_layer_mode[i] equal to 1 specifies that all layers are output in the i-th output layer set. A vps_output_layer_mode[i] equal to 2 specifies that the layers to be output are those with a vps_output_layer_flag[i][j] equal to 1, where the i-th output layer is set. More values ​​may be reserved.

[0173] In the same embodiment, output_layer_flag[i][j] may or may not be signaled according to the value of vps_output_layers_mode[i] for the i-th output layer set.

[0174] In the same or other embodiments, referring to Figure 20, a flag vps_ptl_signal_flag[i] may exist for the i-th output layer set. Depending on the value of vps_ptl_signal_flag[i], the profile tier level information for the i-th output layer set may or may not be signaled.

[0175] In the same or other embodiments, referring to Figure 21, the number of subpictures in the current CVS, max_subpics_minus1, can be signaled in a high-level syntactic structure, such as a VPS, DPS, SPS, PPS, APS, or SEI message.

[0176] In the same embodiment, referring to Figure 21, if the number of subpictures is greater than 1 (max_subpics_minus1>0), the subpicture identifier sub_pic_id[i] of the i-th subpicture may be signaled.

[0177] In the same or other embodiments, one or more syntax elements indicating subpicture identifiers belonging to each layer of each output layer set may be signaled in the VPS. Referring to Figures 22 and 23, sub_pic_id_layer[i][j][k] indicates the k-th subpicture located in the j-th layer of the i-th output layer set. Using this information, the decoder can determine which subpictures for each layer of a particular output layer set can be decoded and output.

[0178] In one embodiment, a picture header (PH) is a syntax structure containing syntax elements that apply to all slices of the coded picture. A picture unit (PU) is a set of NAL units that are related to each other according to a specified classification rule, are consecutive in decoding order, and each contains exactly one coded picture. A PU may include a picture header (PH) and one or more VCL NAL units that constitute the coded picture.

[0179] In one embodiment, the SPS(RBSP) is available for decoding before being referenced and may be contained in at least one AU having a TemporalId equal to 0, or provided via external means.

[0180] In one embodiment, the SPS(RBSP) may be available for decoding before being referenced, and may be contained in at least one AU having a TemporalId equal to 0, which includes one or more PPS that reference the SPS, or may be provided via external means.

[0181] In one embodiment, the SPS(RBSP) may be available for decoding before being referenced by one or more PPS, which include one or more PPS that reference the SPS, or which are provided via external means and are contained in at least one PU having a nuh_layer_id equal to the lowest nuh_layer_id value of the PPS NAL units that reference the SPS NAL units in the CVS.

[0182] In one embodiment, the SPS(RBSP) may be available for decoding before being referenced by one or more PPS, which are contained in at least one PU having a TemporalId equal to 0 and a nuh_layer_id equal to the lowest nuh_layer_id value of the PPS NAL units provided via external means or referencing an SPS NAL unit.

[0183] In one embodiment, the SPS(RBSP) may be available for decoding before being referenced by one or more PPS, or may be provided via external means, or may be provided via external means, and is contained in at least one PU where the TemporalId of a PPS NAL unit in the CVS that references an SPS NAL unit is equal to 0 and the nuh_layer_id is equal to the lowest nuh_layer_id value, and includes one or more PPS that reference the SPS.

[0184] 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 PPS referenced by the coded picture in the CLVS.

[0185] In the same or other embodiments, all SPS NAL units having a specific value for sps_seq_parameter_set_id in CVS may have the same content.

[0186] In the same or other embodiments, SPS NAL units can share the same value space for sps_seq_parameter_set_id, regardless of the nuh_layer_id value.

[0187] In the same or other embodiments, the nuh_layer_id value of an SPS NAL unit may be equal to the lowest nuh_layer_id value of a PPS NAL unit referencing the SPS NAL unit.

[0188] In one embodiment, an SPS having a nuh_layer_id equal to m is referenced by one or more PPS having a nuh_layer_id equal to n. The layer whose nuh_layer_id is equal to m may be the same as the (direct or indirect) reference layer of the layer whose nuh_layer_id is equal to n or the layer whose nuh_layer_id is equal to m.

[0189] In one embodiment, the PPS(RBSP) may be available for pre-reference decoding processing, either contained in at least one AU having a TemporalId equal to the TemporalId of the PPS NAL unit, or provided via external means.

[0190] In one embodiment, the PPS(RBSP) may be available for pre-reference decoding processing, provided via external means or contained in at least one AU having a TemporalId equal to the TemporalId of the PPS NAL unit in the CVS, which includes one or more PHs (or coded slice NAL units) that reference the PPS.

[0191] In one embodiment, the PPS(RBSP) may be available for decoding before being referenced by one or more PHs (or coded slice NAL units) which include one or more PHs (or coded slice NAL units) that reference the PPS, or which are provided via external means and are contained in at least one PU having a nuh_layer_id equal to the lowest nuh_layer_id value of coded slice NAL units that reference the PPS NAL units in the CVS.

[0192] In one embodiment, PPS(RBSP) may be available for decoding before being referenced by one or more PHs (or coded slice NAL units) which include one or more PHs (or coded slice NAL units) that reference the PPS NAL unit, or which are provided via external means, and which include one or more PHs (or coded slice NAL units) that reference the PPS NAL unit, and which have a TemporalId equal to the TemporalId of the PPS NAL unit and a nuh_layer_id equal to the lowest nuh_layer_id value of the coded slice NAL unit.

[0193] In the same or other embodiments, the ph_pic_parameter_set_id of the PH specifies the value of the pps_pic_parameter_set_id of the reference PPS in use. The value of pps_seq_parameter_set_id may be the same for all PPS referenced by the coded picture in the CLVS.

[0194] In the same or other embodiments, all PPS NAL units having a specific value for pps_pic_parameter_set_id within the PU may have the same content.

[0195] In the same or other embodiments, regardless of the nuh_layer_id value, PPS NAL units can share the same value space for pps_pic_parameter_set_id.

[0196] In the same or other embodiments, the nuh_layer_id value of a PPS NAL unit may be equal to the lowest nuh_layer_id value of the coded slice NAL units that reference the NAL units that reference the PPS NAL unit.

[0197] In one embodiment, a PPS having a nuh_layer_id equal to m is referenced by one or more coded slice NAL units having a nuh_layer_id equal to n. The layer whose nuh_layer_id is equal to m may be the same as the (direct or indirect) reference layer of the layer whose nuh_layer_id is equal to n or the layer whose nuh_layer_id is equal to m.

[0198] In one embodiment, the PPS(RBSP) may be available for pre-reference decoding processing, either contained in at least one AU having a TemporalId equal to the TemporalId of the PPS NAL unit, or provided via external means.

[0199] In one embodiment, the PPS(RBSP) may be available for pre-reference decoding processing, provided via external means or contained in at least one AU having a TemporalId equal to the TemporalId of the PPS NAL unit in the CVS, which includes one or more PHs (or coded slice NAL units) that reference the PPS.

[0200] In one embodiment, the PPS(RBSP) may be available for decoding before being referenced by one or more PHs (or coded slice NAL units) which include one or more PHs (or coded slice NAL units) that reference the PPS, or which are provided via external means and are contained in at least one PU having a nuh_layer_id equal to the lowest nuh_layer_id value of coded slice NAL units that reference the PPS NAL units in the CVS.

[0201] In one embodiment, PPS(RBSP) may be available for decoding before being referenced by one or more PHs (or coded slice NAL units) which include one or more PHs (or coded slice NAL units) that reference the PPS NAL unit, or which are provided via external means, and which include one or more PHs (or coded slice NAL units) that reference the PPS NAL unit, and which have a TemporalId equal to the TemporalId of the PPS NAL unit and a nuh_layer_id equal to the lowest nuh_layer_id value of the coded slice NAL unit.

[0202] In the same or other embodiments, the ph_pic_parameter_set_id of the PH specifies the value of the pps_pic_parameter_set_id of the reference PPS in use. The value of pps_seq_parameter_set_id may be the same for all PPS referenced by the coded picture in the CLVS.

[0203] In the same or other embodiments, all PPS NAL units having a specific value for pps_pic_parameter_set_id within the PU may have the same content.

[0204] In the same or other embodiments, regardless of the nuh_layer_id value, PPS NAL units can share the same value space for pps_pic_parameter_set_id.

[0205] In the same or other embodiments, the nuh_layer_id value of a PPS NAL unit may be equal to the lowest nuh_layer_id value of the coded slice NAL units that reference the NAL units that reference the PPS NAL unit.

[0206] In one embodiment, a PPS having a nuh_layer_id equal to m is referenced by one or more coded slice NAL units having a nuh_layer_id equal to n. The layer whose nuh_layer_id is equal to m may be the same as the (direct or indirect) reference layer of the layer whose nuh_layer_id is equal to n or the layer whose nuh_layer_id is equal to m.

[0207] The output layer indicates the layers in the output layer set that will be output. An output layer set (OLS) is a set of layers consisting of a specified set of layers, where one or more layers in the set of layers are designated as output layers. The output layer set (OLS) layer index is the index of a layer in the OLS relative to the list of layers in the OLS.

[0208] A sublayer represents a time-scalable layer of a time-scalable bitstream, consisting of VCL NAL units and associated non-VCL NAL units with a specific value of the TemporalId variable. A sublayer representation represents a subset of the bitstream consisting of a particular sublayer and its sub-sublayer NAL units.

[0209] The VPS RBSP is available for decoding before being referenced and may be contained in at least one AU with a TemporalId of 0, or provided via external means. All VPS NAL units with a specific value for vps_video_parameter_set_id in the CVS may have the same content.

[0210] `vps_video_parameter_set_id` provides an identifier for the VPS for reference by other syntax elements. The value of `vps_video_parameter_set_id` can be greater than 0.

[0211] vps_max_layers_minus1+1 specifies the maximum number of layers allowed within each CVS that references the VPS.

[0212] `vps_max_sublayers_minus1+1` specifies the maximum number of temporal sublayers that may exist in each layer within CVS referencing the VPS. The value of `vps_max_sublayers_minus1` can be in the range of 0 to 6.

[0213] A value of 1 for vps_all_layers_same_num_sublayers_flag specifies that the number of temporal sublayers is the same for all layers in each CVS referencing the VPS. A value of 0 for vps_all_layers_same_num_sublayers_flag specifies that each layer in each CVS referencing the VPS may or may not have the same number of temporal sublayers. If it is not present, the value of vps_all_layers_same_num_sublayers_flag is inferred to be equal to 1.

[0214] A vps_all_independent_layers_flag equal to 1 specifies that all layers in CVS are coded independently without using inter-layer prediction. A vps_all_independent_layers_flag equal to 0 specifies that one or more layers in CVS can use inter-layer prediction. If it is not present, the value of vps_all_independent_layers_flag is assumed to be equal to 1.

[0215] vps_layer_id[i] specifies the value of nuh_layer_id for the i-th layer. For any two non-negative integer values ​​of m and n, the value of vps_layer_id[m] can be less than vps_layer_id[n] when m is less than n.

[0216] A vps_independent_layer_flag[i] equal to 1 indicates that the layer with index i does not use inter-layer prediction. A vps_independent_layer_flag[i] equal to 0 indicates that the layer with index i can use inter-layer prediction, and that a syntax element vps_direct_ref_layer_flag[i][j] with j between 0 and i-1 exists in the VPS. If it does not exist, the value of vps_independent_layer_flag[i] is assumed to be equal to 1.

[0217] A vps_direct_ref_layer_flag[i][j] equal to 0 indicates that the layer with index j is not a direct reference layer for the layer with index i. A vps_direct_ref_layer_flag[i][j] equal to 1 indicates that the layer with index j is a direct reference layer for the layer with index i. For i and j in the range of 0 or greater and less than or equal to vps_max_layers_minus1, if vps_direct_ref_layer_flag[i][j] does not exist, it is presumed to be equal to 0. When vps_independent_layer_flag[i] is equal to 0, there may be at least one value of j in the range of 0 or greater and less than or equal to i-1 such that the value of vps_direct_ref_layer_flag[i][j] is equal to 1.

[0218] The variables NumDirectRefLayers[i], DirectRefLayerIdx[i][d], NumRefLayers[i], RefLayerIdx[i][r], and LayerUsedAsRefLayerFlag[j] are derived as follows: for(i=0;i <=vps_max_layers_minus1;i++){ for(j=0;j <=vps_max_layers_minus1;j++){ dependencyFlag[ i ][ j ]=vps_direct_ref_layer_flag[ i ][ j ] for(k=0;k <i;k++) if(vps_direct_ref_layer_flag[ i ][ k ]&&dependencyFlag[ k ][ j ]) dependencyFlag[ i ][ j ] = 1 } LayerUsedAsRefLayerFlag[ i ]=0 } for(i=0;i <=vps_max_layers_minus1;i++){ for(j=0, d=0, r=0;j <=vps_max_layers_minus1;j++){ if(vps_direct_ref_layer_flag[ i ][ j ]){ DirectRefLayerIdx[ i ][ d++]=j LayerUsedAsRefLayerFlag[ j ]=1 } if(dependencyFlag[ i ][ j ]) RefLayerIdx[ i ][ r++]=j } NumDirectRefLayers[i]=d NumRefLayers[ i ] = r }

[0219] The variable GeneralLayerIdx[i], which specifies the layer index of the layer whose nuh_layer_id is equal to vps_layer_id[i], is derived as follows: for(i=0;i <=vps_max_layers_minus1;i++) GeneralLayerIdx[ vps_layer_id[ i ] ]=i

[0220] A bitstream compatibility requirement is that, for any two different values ​​of both i and j within the range of 0 or greater and less than or equal to vps_max_layers_minus1, when dependencyFlag[i][j] is equal to 1, the values ​​of chroma_format_idc and bit_depth_minus8 applied to the i-th layer can be equal to the values ​​of chroma_format_idc and bit_depth_minus8 applied to the j-th layer, respectively.

[0221] A value of 1 for max_tid_ref_present_flag[i] indicates that the syntax element max_tid_il_ref_pics_plus1[i] exists. A value of 0 for max_tid_ref_present_flag[i] indicates that the syntax element max_tid_il_ref_pics_plus1[i] does not exist.

[0222] A max_tid_il_ref_pics_plus1[i] equal to 0 specifies that inter-layer prediction should not be used for non-IRAP pictures in the i-th layer. A max_tid_il_ref_pics_plus1[i] greater than 0 specifies that pictures with a TemporalId greater than max_tid_il_ref_pics_plus1[i]-1 should not be used as ILRP for decoding pictures in the i-th layer. If none exists, the value of max_tid_il_ref_pics_plus1[i] is assumed to be equal to 7.

[0223] A value of 1 for each_layer_is_an_ols_flag indicates that each OLS contains only one layer, and each layer in CVS referencing the VPS is itself an OLS, with the single layer it contains being the only output layer. A value of 0 for each_layer_is_an_ols_flag means that an OLS can contain two or more layers. If vps_max_layers_minus1 is equal to 0, the value of each_layer_is_an_ols_flag is inferred to be equal to 1. Otherwise, if vps_all_independent_layers_flag is equal to 0, the value of each_layer_is_an_ols_flag is inferred to be equal to 0.

[0224] A value of ols_mode_idc equal to 0 indicates that the total number of OLS specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer indices between 0 and i (inclusive), and for each OLS, only the top layer of the OLS is output.

[0225] A value of ols_mode_idc equal to 1 indicates that the total number of OLS specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer indices between 0 and i (inclusive), and for each OLS, all layers within the OLS are output.

[0226] A value of ols_mode_idc equal to 2 specifies that the total number of OLS specified by the VPS is explicitly signaled, the output layer for each OLS is explicitly signaled, and the other layers are direct or indirect reference layers of the OLS's output layer.

[0227] The value of ols_mode_idc may be in the range of 0 to 2. The value of ols_mode_idc 3 is reserved for future use by ITU-T|ISO / IEC.

[0228] If vps_all_independent_layers_flag is equal to 1 and each_layer_is_an_ols_flag is equal to 0, then the value of ols_mode_idc is presumed to be equal to 2.

[0229] num_output_layer_sets_minus1 plus1 specifies the total number of OLS specified by the VPS when ols_mode_idc is equal to 2.

[0230] The variable TotalNumOlss, which specifies the total number of OLS designated by the VPS, is derived as follows: if(vps_max_layers_minus1==0) TotalNumOlss=1 else if(each_layer_is_an_ols_flag | | ols_mode_idc==0 | | ols_mode_idc==1) TotalNumOlss=vps_max_layers_minus1+1 else if(ols_mode_idc==2) TotalNumOlss=num_output_layer_sets_minus1+1

[0231] ols_output_layer_flag[i][j] being 1 indicates that a layer whose nuh_layer_id is equal to vps_layer_id[j] is the output layer of the i-th OLS when ols_mode_idc is equal to 2, and ols_output_layer_flag[i][j] being 0 indicates that a layer whose nuh_layer_id is equal to vps_layer_id[j] is not the output layer of the i-th OLS when ols_mode_idc is equal to 2.

[0232] The variables NumOutputLayersInOls[i], which specify the number of output layers in the i-th OLS, NumSubLayersInLayerInOLS[i][j], which specify the number of sublayers in the j-th layer of the i-th OLS, OutputLayerIdInOls[i][j], which specify the nuh_layer_id value of the j-th output layer in the i-th OLS, and LayerUsedAsOutputLayerFlag[k], which specify whether the k-th layer is used as an output layer in at least one OLS, are derived as follows: NumOutputLayersInOls

[0000] =1 OutputLayerIdInOls

[0000]

[0000] =vps_layer_id

[0000] NumSubLayersInLayerInOLS

[0000]

[0000] =vps_max_sub_layers_minus1+1 LayerUsedAsOutputLayerFlag

[0000] =1 for(i=1, i <=vps_max_layers_minus1;i++){ if(each_layer_is_an_ols_flag | | ols_mode_idc<2) LayerUsedAsOutputLayerFlag[ i ]=1 else / *(!each_layer_is_an_ols_flag&&ols_mode_idc==2)* / LayerUsedAsOutputLayerFlag[ i ]=0 } for(i=1;i <TotalNumOlss;i++) if(each_layer_is_an_ols_flag | | ols_mode_idc==0){ NumOutputLayersInOls[i]=1 OutputLayerIdInOls[ i ]

[0000] =vps_layer_id[ i ] for(j=0;j<i&&(ols_mode_idc==0);j++) NumSubLayersInLayerInOLS[ i ][ j ]=max_tid_il_ref_pics_plus1[ i ] NumSubLayersInLayerInOLS[ i ][ i ]=vps_max_sub_layers_minus1+1 } else if(ols_mode_idc==1){ NumOutputLayersInOls[ i ]=i+1 for(j=0;j<NumOutputLayersInOls[ i ];j++){ OutputLayerIdInOls[ i ][ j ]=vps_layer_id[ j ] NumSubLayersInLayerInOLS[ i ][ j ]=vps_max_sub_layers_minus1+1 } } else if(ols_mode_idc==2){ for(j=0;j <=vps_max_layers_minus1;j++){ layerIncludedInOlsFlag[ i ][ j ]=0 NumSubLayersInLayerInOLS[ i ][ j ]=0 } for(k=0,j=0;k <=vps_max_layers_minus1;k++)(40) if(ols_output_layer_flag[ i ][ k ]){ layerIncludedInOlsFlag[ i ][ k ]=1 LayerUsedAsOutputLayerFlag[ k ]=1 OutputLayerIdx[ i ][ j ]=k OutputLayerIdInOls[ i ][ j++]=vps_layer_id[ k ] NumSubLayersInLayerInOLS[ i ][ j ]=vps_max_sub_layers_minus1+1 } NumOutputLayersInOls[ i ]=j for(j=0;j <NumOutputLayersInOls[ i ];j++){ idx=OutputLayerIdx[ i ][ j ] for(k=0;k <NumRefLayers[ idx ];k++){ layerIncludedInOlsFlag[ i ][ RefLayerIdx[ idx ][ k ] ]=1 if(NumSubLayersInLayerInOLS[ i ][ RefLayerIdx[ idx ][ k ] ] < max_tid_il_ref_pics_plus1[ OutputLayerIdInOls[ i ][ j ] ]) NumSubLayersInLayerInOLS[ i ][ RefLayerIdx[ idx ][ k ] ]= max_tid_il_ref_pics_plus1[ OutputLayerIdInOls[ i ][ j ] ] } } }

[0233] For each value of i in the range of 0 or greater and less than or equal to vps_max_layers_minus1, the values ​​of LayerUsedAsRefLayerFlag[i] and LayerUsedAsOutputLayerFlag[i] do not have to be equal to 0. In other words, there do not have to be any layers that are neither an output layer of at least one OLS nor a direct reference layer of any other layer.

[0234] For each OLS, there may be at least one output layer. That is, for any value of i in the range of 0 to TotalNumOlss-1, the value of NumOutputLayersInOls[i] may be 1 or greater.

[0235] The variable NumLayersInOls[i], which specifies the number of layers in the i-th OLS, and the variable LayerIdInOls[i][j], which specifies the nuh_layer_id value of the j-th layer of the i-th OLS, are derived as follows: NumLayersInOls

[0000] =1 LayerIdInOls

[0000]

[0000] =vps_layer_id

[0000] for(i=1;i <TotalNumOlss;i++){ if(each_layer_is_an_ols_flag){ NumLayersInOls[ i ]=1 LayerIdInOls[ i ]

[0000] =vps_layer_id[ i ] } else if(ols_mode_idc==0 | | ols_mode_idc==1){ NumLayersInOls[i]=i+1 for(j=0;j <NumLayersInOls[ i ];j++) LayerIdInOls[ i ][ j ]=vps_layer_id[ j ] } else if(ols_mode_idc==2){ for(k=0,j=0;k <=vps_max_layers_minus1;k++) if(layerIncludedInOlsFlag[ i ][ k ]) LayerIdInOls[ i ][ j++]=vps_layer_id[ k ] NumLayersInOls[ i ]=j } }

[0236] The variable OlsLayerIdx[i][j], which specifies the OLS layer index of the layer whose nuh_layer_id is equal to LayerIdInOls[i][j], is derived as follows: for(i=0;i <TotalNumOlss;i++) for j=0;j <NumLayersInOls[ i ];j++) OlsLayerIdx[ i ][ LayerIdInOls[ i ][ j ] ]=j

[0237] The lowest layer in each OLS may be an independent layer. That is, for every i in the range of 0 to TotalNumOlss-1, the value of vps_independent_layer_flag[ GeneralLayerIdx[ LayerIdInOls[ i ]

[0000] ] ] may be set to 1.

[0238] Each layer may be included in at least one OLS specified by the VPS. In other words, for k between 0 and vps_max_layers_minus1, for each layer where a particular value of nuh_layer_id nuhLayerId is equal to one of vps_layer_id[k], there may be at least one pair of i and j such that the value of LayerIdInOls[i][j] is equal to nuhLayerId, where i is between 0 and TotalNumOlss-1 and j is between NumLayersInOls[i]-1.

[0239] In one embodiment, the decoding process currently operates for the picture CurrPic as follows: -PictureOutputFlag is set as follows: -If any of the following conditions are true, PictureOutputFlag will be set to equal to 0. - The current picture is a RASL picture, and the NoOutputBeforeRecoveryFlag of the associated IRAP picture is equal to 1. - The gdr_enabled_flag is equal to 1, and the current picture is a GDR picture with a NoOutputBeforeRecoveryFlag equal to 1. - The gdr_enabled_flag is equal to 1, the current picture is associated with a GDR picture whose NoOutputBeforeRecoveryFlag is equal to 1, and the PicOrderCntVal of the current picture is smaller than the RpPicOrderCntVal of the associated GDR picture. - The sps_video_parameter_set_id is greater than 0, the ols_mode_idc is equal to 0, and the current AU contains a picture picA that satisfies all of the following conditions. - The PictureOutputFlag of PicA is 1. - PicA has a larger nuh_layer_id nuhLid than the current picture. - PicA belongs to the output layer of OLS (i.e., OutputLayerIdInOls [TargetOlsIdx]

[0000] is equal to nuhLid). - The sps_video_parameter_set_id is greater than 0, the ols_mode_idc is equal to 2, and the ols_output_layer_flag [TargetOlsIdx][GeneralLayerIdx [nuh_layer_id]] is equal to 0. - Otherwise, the PictureOutputFlag is set equal to pic_output_flag.

[0240] After all slices of the current picture have been decoded, the current decoded picture is marked as "used for short-term reference", and each ILRP entry within RefPicList

[0000] or RefPicList

[0001] is marked as "used for short-term reference".

[0241] In the same or other embodiments, if each layer is an output layer set, PictureOutputFlag is set to be equal to pic_output_flag, regardless of the value of ols_mode_idc.

[0242] In the same or other embodiments, PictureOutputFlag is set to equal to 0 if sps_video_parameter_set_id is greater than 0, each_layer_is_an_ols_flag is equal to 0, ols_mode_idc is equal to 0, and the current AU includes picture picA that satisfies all of the following conditions: PicA has a PictureOutputFlag equal to 1, PicA has a nuh_layer_id nuhLid that is greater than that of the current picture, and PicA belongs to the output layer of OLS (i.e., OutputLayerIdInOls[TargetOlsIdx]

[0000] is equal to nuhLid).

[0243] In the same or other embodiments, PictureOutputFlag is set to equal to 0 if sps_video_parameter_set_id is greater than 0, each_layer_is_an_ols_flag is equal to 0, ols_mode_idc is equal to 2, and ols_output_layer_flag [ TargetOlsIdx ][ GeneralLayerIdx [ nuh_layer_id ] ] is equal to 0.

[0244] A picture may or may not be referenced in decoding order by one or more subsequent pictures for motion compensation or parameter prediction. A flag indicating whether the current picture is referenced by the following pictures may be explicitly signaled in the picture header or slice header.

[0245] For example, in Figure 24, the non_reference_picture_flag is signaled in the picture header. A non_reference_picture_flag equal to 1 specifies that the picture associated with the PH will never be used as a reference picture. A non_reference_picture_flag equal to 0 specifies that the picture associated with the PH may or may not be used as a reference picture.

[0246] The picture may or may not be cropped and output for display or other purposes. A flag indicating whether or not the picture is currently cropped and output can be explicitly signaled in the picture header or slice header.

[0247] For example, in Figure 24, pic_output_flag is signaled within the picture header. A pic_output_flag equal to 1 indicates that the picture may be cropped and output. A pic_output_flag equal to 0 indicates that the picture may not be cropped and output.

[0248] Currently, if a picture is a non-referenced picture that may not be referenced by subsequent pictures in the decoding order, and the value of non_reference_picture_flag is equal to 1, then the value of pic_output_flag may also be equal to 1. This is because any picture that is not referenced by subsequent pictures and is not output may not be included in the video bitstream by the decoder.

[0249] In the same or other embodiments, when the current picture is a non-referenced picture (i.e., non_reference_picture_flag is equal to 1), pic_output_flag is not explicitly signaled and is inferred to be equal to 1.

[0250] On the encoder side, non-reference pictures that are not output may not be encoded in the encoded bitstream.

[0251] In an intermediate system element, a coded picture with non_reference_picture_flag equal to 1 and pic_output_flag equal to 0 may be discarded from the encoded bitstream.

[0252] Although the present disclosure has described several exemplary embodiments, there are changes, substitutions, and various alternative equivalents within the scope of the present disclosure. Therefore, it will be understood that those skilled in the art can devise numerous systems and methods that embody the principles of the present disclosure and thus fall within its spirit and scope, even though not explicitly shown or described herein.

Description of Reference Numerals

[0253] [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​745 ROM 746 RAM 747 Mass Storage Device 748 System Bus 749 Local Buses

Claims

1. A method for generating an encoded bitstream having a data structure that can be executed by a processor, A step of generating a non_ref_pic_flag and setting the value of the generated non_ref_pic_flag, wherein the value is set to 1 if the picture is never used as a reference picture, and to 0 if it may or may not be used. The steps include signaling the generated non_ref_pic_flag and the set value in a high-level syntax structure, If the value of the generated non_ref_pic_flag is set to 0, the steps are to generate a pic_output_flag and signal it in the high-level syntax structure, or A method comprising the step of not signaling pic_output_flag in the high-level syntax structure if the value of the generated non_ref_pic_flag is set to 1.

2. A method for encoding video data, which can be executed by a processor, A step of generating a non_ref_pic_flag and setting the value of the generated non_ref_pic_flag, wherein the current picture is never used as a reference picture, and the value is set to 1, and the current picture may or may not be used as a reference picture, and the step of setting it to 0. The steps include signaling the generated non_ref_pic_flag and its generated value in a high-level syntax structure, If the value of the generated non_ref_pic_flag is set to 0, the steps are to generate a pic_output_flag and signal it in the high-level syntax structure, or If the value of the generated non_ref_pic_flag is set to 1, the step of not signaling pic_output_flag in the high-level syntax structure is: Methods that include...

3. A method for decoding video data, which can be executed by a processor, A step of receiving a signaled non_ref_pic_flag and its value in a high-level syntax structure, wherein if non_ref_pic_flag is 1, it indicates that the current picture will never be used as a reference picture, and if non_ref_pic_flag is 0, it indicates that the current picture may or may not be used as a reference picture. If the value of non_ref_pic_flag is 0, further in the high-level syntax structure, the step of receiving pic_output_flag, or A method comprising the step of not receiving and estimating pic_output_flag to 1 in the high-level syntax structure if the value of non_ref_pic_flag is 1.

Images