Encoding method, encoding device, decoding method, decoding device, and program

Abstract

To provide a method, a system, and a computer program for signaling output layer sets in coded video data.SOLUTION: A method, a computer program, and a computer system are provided for signaling an output layer set in an encoded video stream. Video data having multiple layers is received. One or more syntactic elements are identified. The syntactic elements specify one or more output layer sets that correspond to output layers from among multiple layers of received video data. One or more output layers corresponding to the specified output layer set are decoded and displayed.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 62 / 903660, filed September 20, 2019, and U.S. Patent Application No. 17 / 021243, filed September 15, 2020, which are incorporated herein in their entireties.

[0002] FIELD OF THE DISCLOSURE This disclosure relates generally to the field of video encoding and decoding, and more particularly to parameter set references and ranges in encoded video streams. [Background technology]

[0003] Video encoding and decoding using inter-picture prediction with motion compensation has been known for decades. Uncompressed digital video may consist of a series of pictures, each with spatial dimensions of, for example, 1920 x 1080 luma samples and associated chroma samples. The series of pictures may have a fixed or variable picture rate (also informally known as a frame rate), for example, 60 pictures per second or 60 Hz. Uncompressed video has significant bitrate requirements. For example, 1080p60 4:2:0 video (1920 x 1080 luma sample resolution at a 60 Hz frame rate) with 8 bits per sample requires a bandwidth approaching 1.5 Gbit / s. One hour of such video requires more than 600 GBytes of storage space.

[0004] One goal of video encoding and decoding can be reducing redundancy in an input video signal through compression. Compression can help reduce the aforementioned bandwidth or storage space requirements by more than two orders of magnitude, in some cases. Both lossless and lossy compression, as well as combinations thereof, can be used. Lossless compression refers to techniques that allow an exact copy of the original signal to be reconstructed from a compressed version of the original signal. When lossy compression is used, the reconstructed signal may not be identical to the original signal, but the distortion between the original and reconstructed signal is small enough to make the reconstructed signal useful for its intended use. For video, lossy compression is widely used. The amount of acceptable distortion depends on the application; for example, users of some consumer streaming applications may tolerate higher distortion than users of television broadcast applications. The achievable compression ratio may reflect that higher acceptable / tolerable distortion allows for higher compression ratios.

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

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

[0007] Changing the picture size of predicted pictures has become more mainstream in modern video coding. For example, VP9 allows for resampling of reference pictures and changing the resolution of the entire picture. Similarly, several proposals 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) allow for resampling of the entire reference picture to a different, i.e., higher or lower, resolution. In that document, different candidate resolutions are proposed to be coded in the sequence parameter set and referenced by per-picture syntax elements in the picture parameter set. Summary of the Invention [Means for solving the problem]

[0008]

[0003] Embodiments relate to a method, system, and computer-readable medium for signaling output layer sets in coded video data. According to one aspect, a method for signaling output layer sets in coded video data is provided. The method may include receiving video data having a plurality of layers. One or more syntax elements are identified. The syntax elements specify one or more output layer sets corresponding to output layers from among the plurality of layers of the received video data. The one or more output layers corresponding to the specified output layer sets are decoded and displayed.

[0009] According to another aspect, a computer system for signaling output layer sets in coded video data is provided. The computer system may include one or more processors, one or more computer-readable memories, one or more computer-readable tangible storage devices, and program instructions stored in at least one of the one or more storage devices for execution by at least one of the one or more processors via at least one of the one or more memories, thereby enabling the computer system to perform a method. The method may include receiving video data having a plurality of layers. One or more syntax elements are identified. The syntax elements specify one or more output layer sets corresponding to output layers from among the plurality of layers of the received video data. The one or more output layers corresponding to the specified output layer sets are decoded and displayed.

[0010] According to yet another aspect, a computer-readable medium for signaling output layer sets in coded video data is provided. The computer-readable medium may include one or more computer-readable storage devices and program instructions stored in at least one of the one or more tangible storage devices, the program instructions being executable by a processor. The program instructions are executable by the processor to perform a method that may include receiving video data corresponding to a plurality of layers. One or more syntax elements are identified. The syntax elements specify one or more output layer sets corresponding to output layers from among the plurality of layers of the received video data. The one or more output layers corresponding to the specified output layer sets are decoded and displayed.

[0011] The above and other objects, features and advantages will become apparent from the following detailed description of illustrative embodiments, which should be read in connection with the accompanying drawings, in which various features of the drawings are not to scale, as the illustrations are for clarity in facilitating understanding by those skilled in the art in conjunction with the detailed description. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a simplified block diagram of a communication system according to one embodiment. [Figure 2] FIG. 1 is a schematic diagram of a simplified block diagram of a communication system according to one embodiment. [Figure 3] FIG. 2 is a schematic diagram of a simplified block diagram of a decoder according to one embodiment. [Figure 4] FIG. 2 is a schematic diagram of a simplified block diagram of an encoder according to one embodiment. [Figure 5] FIG. 1 is a schematic diagram of options for signaling ARC parameters according to one embodiment. [Figure 6] FIG. 2 is a diagram of an example syntax table according to one embodiment. [Figure 7] FIG. 1 is a schematic diagram of a computer system according to one embodiment. [Figure 8] FIG. 1 is a diagram of an example of a prediction structure for scalability with adaptive resolution change. [Figure 9] FIG. 2 is a diagram of an example syntax table according to one embodiment. [Figure 10] FIG. 1 is a simplified block diagram schematic of the parsing and decoding of poc cycles per access unit and access unit count values. [Figure 11] 1 is a schematic diagram of a video bitstream structure including multi-layer sub-pictures. [Figure 12] FIG. 10 is a schematic diagram of a display of a selected subpicture with enhanced resolution. [Figure 13] FIG. 1 is a block diagram of a decoding and display process for a video bitstream that includes multi-layer subpictures. [Figure 14] FIG. 1 is a schematic diagram of a 360-degree video display with a sub-picture enhancement layer. [Figure 15] FIG. 1 is a diagram of an example of layout information for a sub-picture and its corresponding layer and picture prediction structure. [Figure 16] FIG. 10 is a diagram of an example of layout information of a sub-picture and its corresponding layer and picture prediction structure according to the local region spatial scalability modality. [Figure 17] FIG. 10 is a diagram illustrating an example of a syntax table for subpicture layout information. [Figure 18] FIG. 10 is a diagram illustrating an example of a syntax table of a subpicture layout information SEI message. [Figure 19] FIG. 10 is a diagram of an example syntax table showing output layer and profile / tier / level information for each output layer set. [Figure 20] FIG. 10 is a diagram of an example syntax table showing output layer modes for each output layer set. [Figure 21] FIG. 10 is an example of a syntax table showing the current subpicture of each layer for each output layer set. DETAILED DESCRIPTION OF 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 exemplary of the claimed structures and methods, which may be embodied in various forms. These structures and methods, however, may be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Details of well-known features and techniques may be omitted herein to avoid unnecessarily obscuring the presented embodiments.

[0014]

[0001] Embodiments relate generally to the field of data processing, and more particularly to media processing. The exemplary embodiments described below provide, among other things, systems, methods, and computer programs that enable signaling of output layer sets of coded video data. Accordingly, some embodiments have the ability to improve the computing field through improved video encoding and decoding.

[0015] As mentioned above, video encoders and decoders have mostly tended to operate with a given picture size defined for, and remaining constant for, a coded video sequence (CVS), group of pictures (GOP), or similar multi-picture time frame. For example, in MPEG-2, system designs are known to change the horizontal resolution (and thus the picture size) depending on factors such as scene activity, but only in I-pictures, and thus typically for a GOP. Resampling of reference pictures to use different resolutions within a CVS is known, for example, from ITU-T Recommendation H.263 Annex P. However, in this case, the picture size does not change; only the reference pictures are resampled, potentially using only a portion of the picture canvas (in the case of downsampling) or capturing only a portion of the scene (in the case of upsampling). Furthermore, H.263 Annex Q allows for resampling of individual macroblocks upward or downward by a factor of two (in each dimension). Again, the picture size remains the same. The size of a macroblock is fixed in H.263 and therefore does not need to be signaled.

[0016] However, in the context of, for example, 360-degree coding or some surveillance applications, multiple semantically independent source pictures (e.g., six cubic surfaces of a cube-projected 360-degree scene or individual camera inputs in the case of a multi-camera surveillance device) may require separate adaptive resolution settings to address different scene-specific activity at a given time. In other words, an encoder may choose to use different resampling factors for different semantically independent pictures that make up the entire 360-degree or surveillance scene at a given time. When combined into a single picture, this further requires resampling of the reference pictures, and adaptive resolution coding signaling to be available for each portion of the coded picture. Therefore, it may be advantageous to use available adaptive resolution coding signaling data for better signaling, encoding, decoding, and display of the video layer.

[0017] FIG. 1 illustrates a simplified block diagram of a communication system (100) according to one embodiment of the present disclosure. The system (100) may include at least two terminals (110-120) interconnected via a network (150). For unidirectional data transmission, a first terminal (110) may code video data at a local location for transmission to another terminal (120) via the network (150). The second terminal (120) may receive the coded video data of the other terminal from the network (150), decode the coded data, and display the recovered video data. Unidirectional data transmission may be common in media serving applications, for example.

[0018] 1 illustrates a second pair of terminals (130, 140) configured to support bidirectional transmission of coded video, such as may occur during a video conference. In the bidirectional transmission of data, each terminal (130, 140) may encode video data captured at a local location for transmission to the other terminal over a network (150). Each terminal (130, 140) may also receive coded video data transmitted by the other terminal, decode the encoded data, and display the decoded video data on a local display device.

[0019] In FIG. 1 , the terminals (110-140) may be illustrated as servers, personal computers, and smartphones, but the principles of the present disclosure are not so limited. Embodiments of the present disclosure apply to laptop computers, tablet computers, media players, and / or dedicated videoconferencing equipment. The network (150) represents any number of networks that convey coded video data between the terminals (110-140), including, for example, wired and / or wireless communication networks. The communication network (150) may exchange data over circuit-switched and / or packet-switched channels. Exemplary networks include telecommunications networks, local area networks, wide area networks, and / or the Internet. For purposes of this discussion, the architecture and topology of the network (150) may not be important to the operation of the present disclosure, unless otherwise described herein below.

[0020] 2 illustrates the arrangement of video encoders and decoders in a streaming environment as an example of an application of the disclosed subject matter. The disclosed subject matter may be equally applicable to other video-enabled applications, including, for example, video conferencing, digital TV, storage of compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0021] The streaming system may include a video source (201) and a capture subsystem (213), which may include, for example, a digital camera, that creates an uncompressed video sample stream (202). The sample stream (202) is shown with a bold line to emphasize its high data volume compared to an encoded video bitstream and can be processed by an encoder (203) coupled to the camera (201). The encoder (203) may include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter, as described in more detail below. The encoded video bitstream (204) is shown with a thin line to emphasize its lower data volume compared to the sample stream and can be stored on a streaming server (205) for future use. One or more streaming clients (206, 208) can access the streaming server (205) to obtain copies (207, 209) of the encoded video bitstream (204). The client (206) may include a video decoder (210) that decodes an incoming copy of the 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 a video encoding / compression standard. Examples of such standards include ITU-T Recommendation H.265. A video coding standard informally known as Versatile Video Coding, or VVC, is under development. The disclosed subject matter may be used in the context of VVC.

[0022] FIG. 3 may be a functional block diagram of a video decoder (210) according to one or more embodiments.

[0023] The receiver (310) may receive one or more codec video sequences to be decoded by the decoder (210), one coded video sequence at a time, in the same or another embodiment, with the decoding of each coded video sequence being independent of the other coded video sequences. The coded video sequences may be received from a channel (312), which may be a hardware / software link to a storage device that stores the coded video data. The receiver (310) may receive other data, such as coded audio data and / or auxiliary data streams, which may be transferred to each other using entities (not shown). The receiver (310) may separate the coded video sequences from other data. To combat network jitter, a buffer memory (315) may be coupled between the receiver (310) and the entropy decoder / parser (320) (hereinafter "parser"). When the receiver (310) is receiving data from a store-and-forward device of sufficient bandwidth and controllability or from an isochronous network, the buffer (315) may not be necessary or may be small. For use with best-effort packet networks such as the Internet, the buffer (315) may be required and may be relatively large and advantageously adaptively sized.

[0024] The video decoder (210) may include a parser (320) for reconstructing symbols (321) from the entropy-coded video sequence. These symbol categories include information used to manage the operation of the decoder (210) and, potentially, information for controlling a rendering device, such as a display (212), which is not an integral part of the decoder but can be coupled to it, as shown in FIG. 2. The control information for the rendering device(s) may be in the form of Supplementary Enhancement Information (SEI) messages or Video Usability Information (VUI) parameter set fragments (not shown). The parser (320) may parse / entropy decode the received coded video sequence. The coding of the coded video sequence may be in accordance with a video coding technique or standard and may follow principles well known to those skilled in the art, including variable-length coding, Huffman coding, arithmetic coding with or without context sensitivity, etc. The parser (320) may extract, from the coded video sequence, a set of subgroup parameters for at least one of a subgroup of pixels in the video decoder based on at least one parameter corresponding to the group. The subgroup may include a Group of Pictures (GOP), a picture, a tile, a slice, a macroblock, a coding unit (CU), a block, a transform unit (TU), a prediction unit (PU), etc. The entropy decoder / parser may also extract coded video sequence information such as transform coefficients, quantizer parameter values, motion vectors, etc.

[0025] The parser (320) may perform entropy decoding / parsing operations on the video sequence received from the buffer (315) to create symbols (321).

[0026] The reconstruction of the symbols (321) may involve several different units depending on the type of coded video picture or portion thereof (e.g., inter-picture and intra-picture, inter-block and intra-block, etc.), as well as other factors. Which units participate and how may be controlled by subgroup control information parsed from the coded video sequence by the parser (320). The flow of such subgroup control information between the parser (320) and the following units is not shown for clarity.

[0027] Beyond the functional blocks already mentioned, decoder 210 can be conceptually subdivided into several functional units as described below. In an actual implementation operating under commercial constraints, many of these units will interact closely with each other and may be, at least partially, integrated with each other. However, for purposes of describing the disclosed subject matter, the following conceptual subdivision into functional units is appropriate:

[0028] The first unit is a scalar / inverse transform unit (351), which receives quantized transform coefficients as well as control information from the parser (320) as symbol(s) (321), including which transform to use, block size, quantization coefficients, quantization scaling matrices, etc. The scalar / inverse transform unit (351) can output blocks containing sample values ​​that can be input to an aggregator (355).

[0029] 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 prediction information from a previously reconstructed picture but can use prediction information from a previously reconstructed portion of the current picture. Such prediction information may be provided by an intra-picture prediction unit (352). In some cases, the intra-picture prediction unit (352) generates blocks of the same size and shape as the block being reconstructed using surrounding already reconstructed information taken from the current (partially reconstructed) picture (356). The aggregator (355) may optionally append the prediction information generated by the intra-prediction unit (352) to the output sample information provided by the scaler / inverse transform unit (351) on a sample-by-sample basis.

[0030] In other cases, the output samples of the scalar / inverse transform unit (351) may relate to an inter-coded, potentially motion-compensated block. In such cases, the motion compensation prediction unit (353) can access a reference picture memory (357) to retrieve samples used for prediction. After motion-compensating the retrieved samples according to the symbols (321) associated with the block, these samples can be appended by the aggregator (355) to the output of the scalar / inverse transform unit (in this case, referred to as residual samples or residual signals) to generate output sample information. The address in the reference picture memory from which the motion compensation unit retrieves the prediction samples can be controlled by a motion vector, available to the motion compensation unit in the form of a symbol (321), which may have, for example, X, Y, and reference picture components. Motion compensation can also include interpolation of sample values ​​retrieved from the reference picture memory when sub-sample accurate motion vectors are used, motion vector prediction mechanisms, etc.

[0031] The output samples of the aggregator (355) can be subjected to various loop filtering techniques in the loop filter unit (356). Video compression techniques can include in-loop filtering techniques controlled by parameters contained in the coded video bitstream and provided to the loop filter unit (356) as symbols (321) from the parser (320), but can also be responsive to meta-information obtained during decoding of previous portions (in decoding order) of the coded picture or coded video sequence, or responsive to previously reconstructed, loop-filtered sample values.

[0032] The output of the loop filter unit (356) may be a sample stream that can be output to a rendering device (212) and stored in a reference picture memory (356) for use in future inter-picture prediction.

[0033] Once a coded picture is fully reconstructed, it may be used as a reference picture for future prediction. Once a coded picture is fully reconstructed and the coded picture is identified as a reference picture (e.g., by the parser (320)), the current reference picture (356) may become part of the reference picture buffer (357), and memory for the new current picture may be reallocated before beginning reconstruction of the subsequent coded picture.

[0034] Video decoder 320 may perform decoding operations according to a predetermined video compression technology, which may be documented in a standard, such as ITU-T Recommendation H.265. The coded video sequence may comply with the syntax specified in the video compression technology or standard being used, in the sense of conforming to the syntax of the video compression technology or standard as specified in the video compression technology document or standard, particularly the profile document therein. Compliance may also require that the complexity of the coded video sequence be within a range defined by the level of the video compression technology or standard. In some cases, the level limits the maximum picture size, maximum frame rate, maximum reconstruction sample rate (e.g., measured in megasamples per second), maximum reference picture size, etc. The limits set by the level may, in some cases, be further constrained by a Hypothetical Reference Decoder (HRD) specification and metadata for HRD buffer management signaled in the coded video sequence.

[0035] In one embodiment, the receiver (310) may receive additional (redundant) data with the coded video. The additional data may be included as part of one or more coded video sequences. The additional data may be used by the video decoder (320) to properly decode the data and / or to more accurately reconstruct the original video data. The additional data may be in the form of, for example, temporal, spatial, or SNR enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0036] FIG. 4 may be a functional block diagram of a video encoder (203) according to one embodiment of the present disclosure.

[0037] The encoder (203) may receive video samples from a video source (201) (not part of the encoder) that may capture the video image(s) to be encoded by the encoder (203).

[0038] The video source (201) may provide a source video sequence to be encoded by the encoder (203) in the form of a digital video sample stream that can be of any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, ...), any color space (e.g., BT.601 Y CrCB, RGB, ...), and any 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 multiple individual pictures that convey motion when viewed sequentially. The pictures themselves may be organized as a spatial array of pixels, each of which 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 discussion focuses on samples.

[0039] According to one embodiment, the encoder (203) may encode and compress pictures of a source video sequence into a coded video sequence (443) in real time or under any other time constraint required by the application. Ensuring an appropriate coding rate is one function of the controller (450). The controller controls and is operatively coupled to other functional units, as described below. Coupling is not shown for clarity. Parameters set by the controller may include rate control-related parameters (picture skip, quantizer, lambda value for rate-distortion optimization techniques, ...), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. Those skilled in the art can readily identify other functions of the controller (450) that may be relevant to an optimized video encoder (203) for a given system design.

[0040] Some video encoders operate in what those skilled in the art readily recognize as a "coding loop." As an overly simplified explanation, the coding loop may consist of a coding portion of the encoder (430) (hereinafter, the "source coder") (responsible for creating symbols based on the input picture to be coded and one or more reference pictures) and a (local) decoder (433) embedded in the encoder (203) that reconstructs the symbols to create sample data that the (remote) decoder will also create (because, in the video compression techniques considered in the disclosed subject matter, any compression between the symbols and the coded video bitstream is lossless). That reconstructed sample stream is input to a reference picture memory (434). Because decoding of the symbol stream yields bit-exact results regardless of the decoder location (local or remote), the contents of the reference picture buffer are also bit-exact between the local and remote encoders. In other words, the predictive portion of the encoder "sees" the exact same sample values ​​as the decoder will "see" when using prediction during decoding. This basic principle of reference picture synchronism (and the resulting drift if synchronism cannot be maintained, eg, due to channel errors) is well known to those skilled in the art.

[0041] The operation of the "local" decoder (433) may be the same as the operation of the "remote" decoder (210), which has already been described in detail in connection with Figure 3. However, with brief reference also to Figure 3, because symbols are available and the encoding / decoding of the symbols into a coded video sequence by the entropy coder (445) and parser (320) may be lossless, 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).

[0042] An observation that can be made at this point is that any decoder technology, with the exception of parsing / entropy decoding, that is present in the decoder must also be present in the corresponding encoder, in substantially identical functional form. For this reason, the subject matter of the disclosure focuses on decoder operation. A description of the encoder technology can be omitted, as it is the inverse of the decoder technology that has been comprehensively described. Only in certain areas is a more detailed description necessary, as presented below.

[0043] As part of its operation, the source coder (430) may perform motion-compensated predictive coding, which predictively codes an input frame with reference to one or more previously coded frames from the video sequence designated as “reference frames.” In this manner, the coding engine (432) codes differences between pixel blocks of the input frame and pixel blocks of one or more reference frames that may be selected as prediction reference(s) for the input frame.

[0044] The local video decoder (433) may decode coded video data of frames that may be designated as reference frames based on symbols created by the source coder (430). The operation of the coding engine (432) may advantageously be a lossy process. When the coded video data is decoded by a video decoder (not shown in FIG. 4), the reconstructed video sequence may typically be a copy of the source video sequence with some errors. The local video decoder (433) replicates the decoding process that may be performed by the video decoder on the reference frames, causing the reconstructed reference frames to be stored in a reference picture cache (434). In this way, the encoder (203) may locally store copies of reconstructed reference frames that have common content as reconstructed reference frames obtained by the far-end video decoder (without transmission errors).

[0045] The predictor (435) may perform a prediction search for the coding engine (432). That is, for a new frame to be encoded, the predictor (435) may search the reference picture memory (434) for sample data (as candidate reference pixel blocks) or certain metadata, such as reference picture motion vectors, block shapes, etc., that can serve as appropriate prediction references for the new picture. The predictor (435) may operate on a sample block-by-pixel block basis to find an appropriate prediction reference. In some cases, as determined by the search results obtained by the predictor (435), the input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory (434).

[0046] The controller (450) may manage the coding operations of the video coder (430), including, for example, setting parameters and subgroup parameters used to encode the video data.

[0047] The output of all the aforementioned functional units may undergo entropy coding in an entropy coder (445), which converts the symbols produced by the various functional units into a coded video sequence by losslessly compressing the symbols according to techniques known to those skilled in the art, such as Huffman coding, variable length coding, arithmetic coding, etc.

[0048] The transmitter (440) may buffer the coded video sequence(s) created by the entropy coder (445) for transmission over a communication channel (460), which may be a hardware / software link to a storage device that will store the coded video data. The transmitter (440) may merge the coded video data from the video coder (430) with other data to be transmitted, such as coded audio data and / or auxiliary data streams (sources not shown).

[0049] The controller (450) may manage the operation of the encoder (203). During encoding, the controller (450) may assign each coded picture a coded picture type, which may affect the encoding technique that may be applied to the respective picture. For example, pictures may often be assigned as one of the following frame types:

[0050] An intra-picture (I-picture) may be a picture that can be coded and decoded without using other frames in a sequence as a source of prediction. Some video codecs allow different types of intra-pictures, including, for example, independent decoder refresh pictures. Those skilled in the art are aware of these variations of I-pictures and their respective uses and characteristics.

[0051] A predicted picture (P picture) may be a picture that can be coded and decoded using intra- or inter-prediction, which uses at most one motion vector and reference index to predict the sample values ​​of each block.

[0052] A bidirectionally predicted picture (B picture) may be a picture that can be coded and decoded using intra- or inter-prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, a multi-predicted picture can use more than two reference pictures and associated metadata to reconstruct a single block.

[0053] A source picture is generally spatially subdivided into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples each) and may be coded block by block. Blocks may be predictively coded with reference to other (already coded) blocks, as determined by the coding assignment applied to the block's respective picture. For example, blocks of an I-picture may be nonpredictively coded or predictively coded with reference to already coded blocks of the same picture (spatial prediction or intra-prediction). Pixel blocks of a P-picture may be nonpredictively coded by spatial prediction or temporal prediction with reference to one previously coded reference picture. Blocks of a B-picture may be nonpredictively coded by spatial prediction or temporal prediction with reference to one or two previously coded reference pictures.

[0054] The video coder (203) may perform encoding operations in accordance with a predetermined video encoding technique or standard, such as ITU-T Recommendation H.265. In doing so, the video coder (203) may perform various compression operations, including predictive encoding operations that exploit temporal and spatial redundancies in the input video sequence. The coded video data may therefore conform to a syntax specified by the video encoding technique or standard being used.

[0055] In one embodiment, the transmitter (440) may transmit additional data along with the coded video. The video coder (430) may include such data as part of the coded video sequence. The additional data may include temporal / spatial / SNR enhancement layers, other forms of redundant data such as redundant pictures or slices, supplemental enhancement information (SEI) messages, visual usability information (VUI) parameter set fragments, etc.

[0056] Before describing particular aspects of the disclosed subject matter in more detail, it is necessary to explain certain terms that will be referenced in the remainder of the specification.

[0057] A subpicture, as used herein, refers to a rectangular arrangement of samples, blocks, macroblocks, coding units, or similar entities that may be semantically grouped and coded independently at varying resolutions. There may be one or more subpictures per picture. One or more coded subpictures may form a coded picture. One or more subpictures may be assembled into a picture, and one or more subpictures may be extracted from a picture. In some circumstances, one or more coded subpictures may be assembled into a picture coded in the compressed domain without transcoding to the sample level, and in the same or some other cases, one or more coded subpictures may be extracted from a picture coded in the compressed domain.

[0058] Adaptive Resolution Change (ARC) hereinafter refers to a mechanism that allows changing the resolution of pictures or sub-pictures in a coded video sequence, e.g., by resampling of reference pictures. ARC parameters hereinafter refer to the control information needed to perform the adaptive resolution change, which may include, e.g., filter parameters, scaling factors, output picture and / or reference picture resolutions, various control flags, etc.

[0059] The above description focuses on encoding and decoding of a single, semantically independent coded video picture. Before describing the implications of encoding / decoding multiple sub-pictures with independent ARC parameters and the additional complexity that they imply, options for signaling ARC parameters are discussed.

[0060] Referring to Figure 5, several novel options for signaling ARC parameters are shown. As can be seen, each option has some advantages and some 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 the prior art, for signaling ARC parameters. These options may not be mutually exclusive and may conceivably be interchanged based on application needs, the standard technology involved, or the choice of encoder.

[0061] The classes of ARC parameters may include: Separate or combined upsampling / downsampling factors in the X and Y dimensions. An upsampling / downsampling factor with an additional time dimension that indicates a constant speed zoom in / out of a given number of pictures. Either of the above two may involve encoding one or more possibly short syntax elements that may point to a table containing those coefficient(s). Resolution of the X or Y dimension of the input picture, output picture, reference picture, coded picture, in units of samples, blocks, macroblocks, CUs, or any other suitable granularity, combined or separate. If there are two or more resolutions (e.g., input picture resolution, reference picture resolution, etc.), in some cases one set of values ​​can be inferred from another set of values. This can be gated, for example, by using flags. See below for more detailed examples. "Warping" coordinates similar to those used in H.263 Annex P, also of appropriate granularity as described above. H.263 Annex P defines one efficient way of encoding such warping coordinates, but it is conceivable that other, potentially more efficient, methods may be devised. For example, the variable-length, lossless "Huffman"-style coding of Annex P's warping coordinates could be replaced by appropriate-length binary coding, where the length of the binary codewords could be derived, for example, from the maximum picture size, possibly multiplied by a factor, and offset by a value to allow "warping" outside the bounds of the maximum picture size. Upsampling or Downsampling Filter Parameters. In the simplest case, there may be only a single filter for upsampling and / or downsampling. 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 an upsampling / downsampling ratio that matches that signaled according to any of the mechanisms described above, and so on.

[0062] In the following, the description assumes the encoding of a finite set of upsampling / downsampling coefficients (the same coefficients to be used in both the X and Y dimensions) indicated via a codeword, which can advantageously be variable length coded, for example using Ext-Golomb codes common to several syntax elements in video coding specifications such as H.264 and H.265.

[0063] Many similar mappings can be devised according to the needs of the application and the capabilities of the upscaling and downscaling mechanisms available in the video compression technology or standard. The table can be extended to a larger number of values. The values ​​may also be represented by entropy coding mechanisms other than Ext-Golomb codes, for example, using binary coding. This may have some advantages if the resampling factor is an object external to the video processing engine (encoder and decoder, to begin with), for example, by MANE. Note that in the (presumably) most common case where no resolution change is required, a short Ext-Golomb code can be chosen, only one bit in the above table. This may have coding efficiency advantages over using a binary code in the most common case.

[0064] The number of entries in the table, as well as their semantics, may be fully or partially configurable. For example, a basic overview of the table may be conveyed in a "high" parameter set, such as a sequence parameter set or a decoder parameter set. Alternatively or additionally, one or more such tables may be defined in a video coding technology or standard and may be selected, for example, via a decoder parameter set or a sequence parameter set.

[0065] The following describes how the upsampling / downsampling coefficients (ARC information) coded as described above can be included in the syntax of a video coding technique or standard. Similar considerations can also apply to one or several codewords controlling an upsampling / downsampling filter. See below for considerations when a relatively large amount of data is required for a filter or other data structure.

[0066] H.263 Annex P includes ARC information 502 in the form of four warping coordinates in the picture header 501, specifically in the H.263 PLUSPTYPE (503) header extension. This can be a wise 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 in nature, scaling factors may not be relevant across picture boundaries.

[0067] The above-cited JVCET-M135-v1 includes ARC reference information (505) (index) located in a picture parameter set (504) that points to a table (506) containing target resolutions located in a sequence parameter set (507). The placement of possible resolutions in the table (506) within the sequence parameter set (507) can be justified, according to the authors' dictum, by using SPS as a negotiation point for interoperability during capability exchange. Resolution can vary within the limits set by the values ​​in the table (506) for each picture by referencing the appropriate picture parameter set (504).

[0068] Still referring to Figure 5, the following additional options may exist for conveying ARC information in a video bitstream: Each of these options has some advantages over existing techniques, as discussed above, and these options may coexist within the same video coding technology or standard.

[0069] In one embodiment, ARC information (509), such as a resampling (zoom) factor, may be present in a slice header, a GOB header, a tile header, or a tile group header (hereafter, tile group header) (508). This may be sufficient if the ARC information is small, e.g., a single variable-length ue(v) or a fixed-length codeword of a few bits, as shown above. Having the ARC information directly in the tile group header has the added advantage that the ARC information may be applicable to, for example, the sub-picture represented by that tile group, rather than to the entire picture. See also below. Additionally, even if a video compression technology or standard only assumes whole-picture adaptive resolution change (e.g., as opposed to tile group-based adaptive resolution change), placing the ARC information in the tile group header, as opposed to placing it in an H.263-style picture header, has some advantages from an error resilience perspective.

[0070] In the same or another embodiment, the ARC information (512) itself may reside in an appropriate parameter set (511), such as, for example, a picture parameter set, a header parameter set, a tile parameter set, an adaptive parameter set, etc. (an adaptive parameter set is shown). The scope of the parameter set may advantageously be below the picture, e.g., a tile group. The use of the ARC information is implicit with the activation of the associated parameter set. For example, if a video coding technology or standard only contemplates picture-based ARC, a picture parameter set or equivalent may be appropriate.

[0071] In the same or another embodiment, the ARC reference information (513) can be present in a tile group header (514) or similar data structure, and can point to a portion of the ARC information (515) available in a parameter set (516) that spans more than a single picture, such as a sequence parameter set or a decoder parameter set.

[0072] Indirectly implied activation of an additional level of PPS from the tile group header, PPS, and SPS, as used in JVET-M0135-v1, seems unnecessary because picture parameter sets, like sequence parameter sets, can be used (and some standards, such as RFC3984, have) for capability negotiation or announcement. However, if the ARC information should be applicable to, for example, subpictures also represented by tile groups, a parameter set with activation scope limited to the tile group, such as an adaptive parameter set or a header parameter set, may be a better choice. Also, if the ARC information is of non-negligible size, for example, if it contains filter control information such as a large number of filter coefficients, these settings may be reusable by future pictures or subpictures by referencing the same parameter set, so the parameters may be a better choice than directly using the header (508) from the perspective of coding efficiency.

[0073] When using a sequence parameter set or another higher level parameter set with a range spanning multiple pictures, several considerations may apply.

[0074] The parameter set for storing the ARC information table (516) can be a sequence parameter set in some cases, but advantageously a decoder parameter set in other cases. A decoder parameter set can have multiple CVSs, i.e., activation ranges for all coded video bits in the coded video stream, i.e., from the start of the session to the end of the session. Such ranges may be more appropriate because possible ARC factors may be decoder capabilities, possibly implemented in hardware, and hardware capabilities tend not to change for any CVS (at least in some entertainment systems, a Group of Pictures, which is one second or less in length). However, placing the table in a sequence parameter set is explicitly included in the placement options described herein.

[0075] The ARC reference information (513) can advantageously be placed directly in the picture / slice / tile / GOB / tile group header (hereafter referred to as the tile group header) (514) rather than in the picture parameter set as in JVCET-M0135-v1. The reason is as follows: If an encoder wants to change a single value in a picture parameter set, such as the ARC reference information, it needs to create a new PPS and reference the new PPS. Assume that only the ARC reference information changes, while other information in the PPS, such as quantization matrix information, remains the same. Such information may be of considerable size and needs to be retransmitted to complete the new PPS. Since the ARC reference information can be a single codeword, such as an index into the table (513), and 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 detour through the PPS, as proposed in JVET-M0135-v1, can be significantly better from the perspective of coding efficiency. Similarly, putting the ARC reference information in the PPS has the further disadvantage that, since the scope of picture parameter set activation is the picture, the ARC information referenced by the ARC reference information (513) must necessarily apply to the entire picture, not to a sub-picture.

[0076] In the same or another embodiment, signaling of ARC parameters may follow the 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 in such syntax diagrams loosely follows C-style programming. Bolded lines indicate syntax elements present in the bitstream, while non-bolded lines often indicate control flow or variable setting.

[0077] The tile group header (601), an exemplary syntax structure for a header applicable to a (possibly rectangular) portion of a picture, can conditionally contain the variable-length Exp-Golomb coding syntax element dec_pic_size_idx (602) (shown in bold). The presence of this syntax element in the tile group header can be gated with respect to the use of adaptive resolution (603), a flag value not shown here in bold, meaning that the flag is present in the bitstream at the point where it occurs in the syntax diagram. Whether adaptive resolution is used for this picture or portion of a picture can be signaled in any high-level syntax structure, inside or outside the bitstream. In the illustrated example, it is signaled in the sequence parameter set, as outlined below.

[0078] 6, an excerpt of a sequence parameter set (610) is also shown. The first syntax element shown is adaptive_pic_resolution_change_flag (611). If true, that flag can indicate the use of adaptive resolution, which may require some control information. In this example, such control information is conditionally present based on the value of the flag based on an if() statement in the parameter set (612) and the tile group header (601).

[0079] When adaptive resolution is used, in this example, it is the output resolution in samples (613) that is coded. Number 613 refers to both output_pic_width_in_luma_samples and output_pic_height_in_luma_samples, which together can define the resolution of the output picture. Elsewhere in a video coding technology or standard, some restrictions on either value can be defined. For example, a level definition may limit the number of total output samples that can be the product of the values ​​of those two syntax elements. Some video coding technologies or standards, or external technologies or standards such as system standards, may also limit number ranges (e.g., one or both dimensions must be divisible by a power of 2) or aspect ratios (e.g., width and height must have a relationship such as 4:3 or 16:9). Such restrictions may be introduced to facilitate hardware implementation or for other reasons and are well known in the art.

[0080] In certain applications, it may be desirable for the encoder to instruct the decoder to use a particular reference picture size rather than implicitly assuming that size is the output picture size. In this example, the syntax element reference_pic_size_present_flag (614) gates the conditional presence of the reference picture dimensions (615) (again, the numbers refer to both width and height).

[0081] Finally, a table of possible decoded picture widths and heights is shown. Such a table can be represented, for example, by the table designation (num_dec_pic_size_in_luma_samples_minus1) (616). "minus1" can refer to the interpretation of the value of that syntax element. For example, if the coded value is 0, there is one table entry. If the value is 5, there are six table entries. For each "row" in the table, the syntax (617) contains the width and height of the decoded picture.

[0082] The presentation table entries (617) can be indexed using the syntax element dec_pic_size_idx (602) in the tile group header, allowing for different decoded sizes, and in fact zoom ratios, per tile group.

[0083] The techniques for signaling adaptive resolution parameters described above can be implemented as computer software using computer-readable instructions and physically stored on one or more computer-readable media. For example, Figure 7 illustrates a computer system 700 suitable for implementing certain embodiments of the disclosed subject matter.

[0084] Computer software may be coded using any suitable machine or computer language that can be assembled, compiled, linked, or similar mechanisms to create code containing instructions that can be executed by a computer's central processing unit (CPU), graphics processing unit (GPU), etc., directly, or by interpretation, microcode execution, etc.

[0085] The instructions may be executed on various types of computers or computer components including, for example, personal computers, tablet computers, servers, smartphones, gaming consoles, Internet of Things devices, and the like.

[0086] 7 for computer system 700 are exemplary in nature and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing embodiments of the present disclosure. The arrangement of components should not be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary embodiment of computer system 700.

[0087] The computer system 700 may include certain human interface input devices. Such human interface input devices may respond to input by one or more human users via, for example, tactile input (e.g., keystrokes, swipes, data glove movements), audio input (e.g., voice, clapping), visual input (e.g., gestures), or olfactory input (not shown). The human interface devices may be used to capture certain media not necessarily directly associated with conscious human input, such as audio (e.g., voice, music, ambient sounds), images (e.g., scanned images, photographic images obtained from a still image camera), and video (e.g., two-dimensional video, three-dimensional video, including stereoscopic video).

[0088] The input human interface devices may include one or more of a keyboard 701, a mouse 702, a trackpad 703, a touchscreen 710, a data glove 704, a joystick 705, a microphone 706, a scanner 707, and a camera 708 (only one of each is shown).

[0089] The computer system 700 may also include certain human interface output devices. Such human interface output devices may stimulate one or more of the human user's senses, for example, through tactile output, sound, light, and smell / taste. Such human interface output devices may include tactile output devices (e.g., tactile feedback via a touchscreen 710, data gloves 704, or joystick 705, although some tactile feedback devices may not function as input devices), audio output devices (such as speakers 709, headphones (not shown)), visual output devices (such as screens 710, including CRT screens, LCD screens, plasma screens, and OLED screens, each with or without touchscreen input capabilities, each with or without tactile feedback capabilities, some of which may be capable of outputting output in more than three dimensions through means such as two-dimensional visual output or stereoscopic output, such as virtual reality glasses (not shown), holographic displays, and smoke tanks (not shown)), and printers (not shown).

[0090] The computer system 700 may also include human-accessible storage devices and media associated with the storage devices, such as optical media including CD / DVD ROM / RW 720 with media 721 such as CD / DVD, thumb drive 722, removable hard drive or solid state drive 723, legacy magnetic media such as tape or floppy disk (not shown), dedicated ROM / ASIC / PLD based devices such as security dongles (not shown), etc.

[0091] Those skilled in the art will also understand that the term "computer-readable medium" as used in connection with the subject matter of this disclosure does not encompass transmission media, carrier waves, or other transitory signals.

[0092] The computer system 700 may also include interfaces to one or more communication networks. The networks may be, for example, wireless, wired, or optical. The networks may further be local, wide area, metropolitan, vehicular and industrial, real-time, delay-tolerant, etc. Examples of networks include local area networks such as Ethernet, WLAN, etc.; cellular networks including GSM, 3G, 4G, 5G, LTE, etc.; television wired or wireless wide area digital networks including cable television, satellite television, and terrestrial broadcast television; vehicular and industrial networks including CANBus, etc. Some networks typically require an external network interface adapter connected to some general-purpose data port or peripheral bus (749) (e.g., a USB port on computer system 700), while other networks are typically integrated into the core of computer system 700 by connection to a system bus (e.g., an Ethernet interface to a PC computer system or a cellular network interface to a smartphone computer system) as described below. Using any of these networks, computer system 700 can communicate with other entities. Such communications can be unidirectional, receive-only (e.g., television broadcasts), unidirectional transmit-only (e.g., from a CANbus to some CANbus devices), or bidirectional, for example, to other computer systems using local or wide-area digital networks. Several protocols and protocol stacks may be used with each of these networks and network interfaces, as described above.

[0093] The aforementioned human interface devices, human-accessible storage devices, and network interfaces may be attached to core 740 of computer system 700 .

[0094] The core 740 may include one or more central processing units (CPUs) 741, graphics processing units (GPUs) 742, specialized programmable processing units in the form of field programmable gate arrays (FPGAs) 743, hardware accelerators for certain tasks 744, etc. These devices may be connected via a system bus 748, along with read-only memory (ROM) 745, random access memory 746, and internal mass storage such as an internal non-user-accessible hard drive, SSD, etc. 747. In some computer systems, the system bus 748 may be accessible in the form of one or more physical plugs to allow expansion with additional CPUs, GPUs, etc. Peripheral devices may be attached directly to the core's system bus 748 or via a peripheral bus 749. Peripheral bus architectures include PCI, USB, etc.

[0095] The CPU 741, GPU 742, FPGA 743, and accelerator 744 may execute a number of instructions that, in combination, may constitute the aforementioned computer code. The computer code may be stored in ROM 745 or RAM 746. Transient data may also be stored in RAM 746, while persistent data may be stored, for example, in internal mass storage 747. Rapid storage and retrieval from any of the memory devices may be enabled through the use of cache memory, which may be closely associated with one or more of the CPU 741, GPU 742, mass storage 747, ROM 745, RAM 746, etc.

[0096] The computer-readable medium may bear computer code for performing various computer-implemented operations. The medium and computer code may be those specially designed and constructed for the purposes of the present disclosure, or they may be of the kind well known and available to those skilled in the computer software arts.

[0097] By way of example and not limitation, computer system 700 having the architecture, and specifically core 740, may provide functionality as a result of processor(s) (including CPU, GPU, FPGA, accelerator, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media may be user-accessible mass storage, as described above, as well as media associated with some storage of core 740 that is non-transitory in nature, such as core internal mass storage 747 or ROM 745. Software implementing various embodiments of the present disclosure may be stored in such devices and executed by core 740. Computer-readable media may include one or more memory devices or chips, depending on particular needs. Software may cause core 740, and specifically the processors therein (including CPU, GPU, FPGA, etc.), to perform particular processes or particular portions of particular processes described herein, including defining data structures stored in RAM 746 and modifying such data structures according to software-defined processes. Additionally, or alternatively, a computer system may provide functionality as a result of hardwired or otherwise embodied logic in circuitry (e.g., accelerator 744) that can operate in place of or together with software to perform particular processes or portions of particular processes described herein. When referring to software, it can encompass logic, and vice versa, where appropriate. When referring to a computer-readable medium, it can encompass, where appropriate, circuitry (such as an integrated circuit (IC)) that stores software for execution, circuitry that embodies logic for execution, or both. The present disclosure encompasses any appropriate combination of hardware and software.

[0098] Some video coding technologies or standards, e.g., VP9, ​​support spatial scalability by implementing a form of reference picture resampling (signaled quite differently than the disclosed subject matter) in conjunction with temporal scalability to enable spatial scalability. In particular, certain reference pictures may 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 using regular prediction mechanisms at higher resolutions to add detail.

[0099] The disclosed subject matter can be used in such environments. In some cases, in the same or another embodiment, values ​​in NAL unit headers, e.g., the Temporal ID field, can be used to indicate spatial layers as well as temporal layers. Doing so has several advantages in certain system designs. For example, existing selected transport units (SFUs) created and optimized for selected transport of temporal layers based on the Temporal ID value in the NAL unit header can be used in scalable environments without modification. To enable this, there may be requirements for a mapping between coded picture sizes and temporal layers, indicated by the Temporal ID field in the NAL unit header.

[0100] In some video coding techniques, an access unit (AU) can refer to a coded picture(s), slice(s), tile(s), NAL unit(s), etc. that are captured and composed into a respective picture / slice / tile / NAL unit bitstream at a given temporal instance, which may be composition time.

[0101] In HEVC and some other video coding technologies, a picture order count (POC) value may be used to indicate a reference picture selected from multiple reference pictures stored in a decoded picture buffer (DPB). When an access unit (AU) includes one or more pictures, slices, or tiles, each picture, slice, or tile belonging to the same AU may have the same POC value, from which it may be derived that they were created from content with the same composition time. In other words, in a scenario where two pictures / slices / tiles have the same given POC value, it may indicate two pictures / slices / tiles that belong to the same AU and have the same composition time. Conversely, two pictures / tiles / slices with different POC values ​​may indicate those pictures / slices / tiles that belong to different AUs and have different composition times.

[0102] In one embodiment of the disclosed subject matter, the aforementioned strict relationship may be relaxed in that an access unit may contain pictures, slices, or tiles with different POC values. By allowing different POC values ​​within an AU, it becomes possible to use the POC values ​​to identify potentially independently decodable pictures / slices / tiles that have the same presentation time. This may enable support for multiple scalable layers without modifying reference picture selection signaling (e.g., reference picture set signaling or reference picture list signaling), as described in more detail below.

[0103] However, it is still desirable to be able to identify, from the POC value alone, the AU to which a picture / slice / tile belongs, relative to other pictures / slices / tiles with different POC values. This can be achieved as described below.

[0104] In the same or other embodiments, the access unit count (AUC) may be signaled in a high-level syntax structure such as a NAL unit header, a slice header, a tile group header, an SEI message, a parameter set, or an AU delimiter. The value of the AUC may be used to identify which NAL unit, picture, slice, or tile belongs to a given AU. The value of the AUC may correspond to a distinct compositing time instance. The AUC value may be equal to a multiple of the POC value. The AUC value may 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, due to the small limitation of the number space of the AUC value, the division operation may be replaced with a shift operation. For example, the AUC value may be equal to the most significant bit (MSB) value of the POC value range.

[0105] In the same embodiment, the value of the POC cycle per AU (poc_cycle_au) may be signaled in a high-level syntax structure such as a NAL unit header, a slice header, a tile group header, an SEI message, a parameter set, or an AU delimiter. poc_cycle_au may 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, pictures, slices, or tiles having POC values ​​equal to 0 through 3, inclusive, are associated with an AU having an AUC value equal to 0, and pictures, slices, or tiles having POC values ​​equal to 4 through 7, inclusive, are associated with an AU having an AUC value equal to 1. Thus, the value of AUC may be inferred by dividing the POC value by the value of poc_cycle_au.

[0106] In the same or another embodiment, the value of poc_cycle_au may be derived from information, e.g., located in a video parameter set (VPS), that identifies the number of spatial or SNR layers in the coded video sequence. Such possible relationships are briefly described below. While the derivation as described above may save a few bits in the VPS and thus improve coding efficiency, it may be advantageous to explicitly code poc_cycle_au in an appropriate high-level syntax structure hierarchically lower in the video parameter set, allowing poc_cycle_au to be minimized for a given small portion of the bitstream, such as a picture. This optimization may save more bits than can be saved by the derivation process described above, because the POC value (and / or the values ​​of syntax elements that indirectly reference the POC) may be coded in a lower-level syntax structure.

[0107] 8 shows an example of a video sequence structure with a combination of temporal_id, layer_id, POC, and AUC values ​​with adaptive resolution change. In this example, a picture, slice, or tile in the first AU with AUC=0 may have temporal_id=0 and layer_id=0 or 1, and a picture, slice, or tile in the second AU with AUC=1 may have temporal_id=1 and layer_id=0 or 1, respectively. Regardless of the values ​​of temporal_id and layer_id, the value of POC increases by 1 for each picture. In this example, the value of poc_cycle_au may be equal to 2. Preferably, the value of poc_cycle_au may be set equal to the number of (spatial scalability) layers. Thus, in this example, the value of POC increases by 2 and the value of AUC increases by 1.

[0108] In the above embodiments, all or part of the inter-picture or inter-layer prediction structure and reference picture indication 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 a value of POC or a delta value of POC between the current picture and the selected reference picture. In the disclosed subject matter, RPS and RPL can be used to indicate inter-picture or inter-layer prediction structure without changing the signaling, but with the following restrictions: If the value of the temporal_id of a reference picture is greater than the value of the temporal_id of the current picture, the current picture may not use that reference picture for motion compensation or other prediction. If the value of the layer_id of a reference picture is greater than the value of the layer_id of the current picture, the current picture may not use that reference picture for motion compensation or other prediction.

[0109] In the same embodiment and other embodiments, motion vector scaling based on POC difference for temporal motion vector prediction may be disabled across multiple pictures within an access unit. Thus, although each picture may have a different POC value within an access unit, the motion vectors are not scaled and are 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 with the same time instance. Therefore, in this embodiment, if the reference picture belongs to the AU associated with the current picture, the motion vector scaling function may return 1.

[0110] In the same and other embodiments, if the spatial resolution of the reference picture is different from the spatial resolution of the current picture, motion vector scaling based on the POC difference for temporal motion vector prediction may be optionally disabled across multiple pictures. If motion vector scaling is allowed, the motion vector is scaled based on both the POC difference and the spatial resolution ratio between the current picture and the reference picture.

[0111] In the same or another embodiment, motion vectors may be scaled based on the AUC differential instead of the POC differential for temporal motion vector prediction, especially 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), the motion vector scaling based on the AUC differential may be identical to the motion vector scaling based on the POC differential.

[0112] In the same or another embodiment, when a motion vector is scaled based on an AUC difference, reference motion vectors within the same AU with the current picture (having the same AUC value) are not scaled based on the AUC difference and are used for motion vector prediction without scaling or with scaling based on the spatial resolution ratio between the current picture and the reference picture.

[0113] In the same and other embodiments, the AUC value is used to identify AU boundaries and is used for hypothetical reference decoder (HRD) operations that require input and output timing with AU granularity. In most cases, the decoded picture of the highest layer within an AU can be output for display. The AUC value and layer_id value can be used to identify the output picture.

[0114] In one embodiment, a picture may consist of one or more sub-pictures. Each sub-picture may cover a local area or the entire area of ​​the picture. The area supported by a sub-picture may or may not overlap with the area supported by another sub-picture. The area comprised by one or more sub-pictures may or may not cover the entire area of ​​the picture. When a picture consists of sub-pictures, the area supported by the sub-picture is the same as the area supported by the picture.

[0115] In the same embodiment, a sub-picture may be coded by a coding method similar to that used for the coded picture. A sub-picture may be coded independently or may be coded depending on another sub-picture or coded picture. A sub-picture may or may not have perspective dependency from another sub-picture or coded picture.

[0116] In the same embodiment, coded sub-pictures may be included in one or more layers. The coded sub-pictures within a layer may have different spatial resolutions. The original sub-pictures may be spatially resampled (upsampled or downsampled), coded with different spatial resolution parameters, and included in the bitstream corresponding to the layer.

[0117] In the same or another embodiment, a (W,H) sub-picture may be encoded and included in the coded bitstream corresponding to layer 0, where W denotes the width of the sub-picture and H denotes the height of the sub-picture, respectively, and (W*S w,k ,H*S h,k ), a sub-picture upsampled (or downsampled) from a sub-picture with the original spatial resolution may be encoded and included in the coded bitstream corresponding to layer k, and S w,k , S h,kindicates the resampling ratio in the horizontal and vertical directions. S w,k , S h,k If the value of is greater than 1, resampling is equivalent to upsampling. On the other hand, if S w,k , S h,k If the value of is less than 1, resampling is equivalent to downsampling.

[0118] In the same or another embodiment, a coded subpicture within a layer may have a different visual quality than a coded subpicture within another layer, either within the same subpicture or a different subpicture. For example, subpicture i within layer n may have a quantization parameter Q i,n and subpicture j in layer m is coded with quantization parameter Q j,m is encoded as

[0119] In the same or another embodiment, coded sub-pictures within a layer may be independently decodable without perspective or decoding dependency from coded sub-pictures in another layer of the same local region. A sub-picture layer that may be independently decodable without reference to another sub-picture layer of the same local region is an independent sub-picture layer. A coded sub-picture within an independent sub-picture layer may or may not have decoding or perspective dependency from previously coded sub-pictures in the same sub-picture layer, but the coded sub-picture may not have any dependency from coded pictures in another sub-picture layer.

[0120] In the same or another embodiment, coded subpictures within a layer may be dependently decodable with perspective dependency or decoding dependency from coded subpictures in another layer of the same local region. A subpicture layer that may be dependently decodable with reference to another subpicture layer of the same local region is a dependent subpicture layer. A coded subpicture within a dependent subpicture may reference coded subpictures belonging to the same subpicture, previously coded subpictures in the same subpicture layer, or both reference subpictures.

[0121] In the same or another embodiment, a 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 a coded subpicture. An independent subpicture layer may have a value of a layer identifier (layer_id), which may be present in the NAL unit header or another high-level syntax structure, equal to 0. A subpicture layer with layer_id equal to 0 is a base subpicture layer.

[0122] In the same or another embodiment, a picture may consist of one or more foreground subpictures and one background subpicture. The area supported by a background subpicture may be equal to the area of ​​the picture. The area supported by a foreground subpicture may overlap the area supported by a background subpicture. 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 reference the same base layer for decoding. Each non-base subpicture layer with layer_id equal to a may reference a non-base subpicture layer with layer_id equal to b, where a is greater than b.

[0123] In the same or another embodiment, a picture may consist of one or more foreground subpictures with or without background subpictures. Each subpicture may have its own base subpicture layer and one or more non-base (enhancement) layers. Each base subpicture layer may be referenced by one or more non-base subpicture layers. Each non-base subpicture layer with layer_id equal to a may reference a non-base subpicture layer with layer_id equal to b, where a is greater than b.

[0124] In the same or another embodiment, a picture may consist of one or more foreground subpictures with or without background subpictures. Each coded subpicture in a (base or non-base) subpicture layer may be referenced by one or more non-base layer subpictures that belong to the same subpicture and one or more non-base layer subpictures that do not belong to the same subpicture.

[0125] In the same or another embodiment, 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 reference divided subpictures in layer a.

[0126] In the same or another embodiment, a coded video sequence (CVS) may be a group of coded pictures. A CVS may consist of one or more coded sub-picture sequences (CSPS), which may be a group of coded sub-pictures covering the same local region of a picture. A CSPS may have the same or a different temporal resolution as the coded video sequence.

[0127] In the same or another embodiment, a CSPS may be coded and included in one or more layers. A CSPS may consist of one or more CSPS layers. By decoding one or more CSPS layers corresponding to a CSPS, a sequence of sub-pictures corresponding to the same local region may be reconstructed.

[0128] In the same or different embodiments, the number of CSPS layers corresponding to a CSPS may be the same as or different from the number of CSPS layers corresponding to another CSPS.

[0129] In the same or another embodiment, a CSPS layer may have a different temporal resolution (e.g., frame rate) than another CSPS layer, and the original (uncompressed) sub-picture sequence may be temporally resampled (upsampled or downsampled), coded with different temporal resolution parameters, and included in the bitstream corresponding to the layer.

[0130] In the same or another embodiment, a sub-picture sequence having a frame rate F may be encoded and included in the coded bitstream corresponding to layer 0, where F*S t,k where S is a temporally upsampled (or downsampled) sub-picture sequence from the original sub-picture sequence, and S is a coded bitstream corresponding to layer k. t,k denotes the temporal sampling ratio of layer k. t,k If the value of is greater than 1, the temporal resampling process is equivalent to frame rate up-conversion. t,k If the value of is less than 1, the temporal resampling process is equivalent to a frame rate down-conversion.

[0131] In the same or another embodiment, when a subpicture with CSPS layer a is referenced by a subpicture with CSPS layer b for motion compensation or any inter-layer prediction, if the spatial resolution of CSPS layer a is different from the spatial resolution of CSPS layer b, the decoded pixels in CSPS layer a are resampled and used for reference. The resampling process may require upsampling filtering or downsampling filtering.

[0132] 9 shows an example of a syntax table for signaling the vps_poc_cycle_au syntax element in the VPS (or SPS), which indicates the poc_cycle_au used for all pictures / slices in a coded video sequence, and the slice_poc_cycle_au syntax element, which indicates the poc_cycle_au of the current slice in the slice header. If the POC value increases uniformly per AU, vps_contant_poc_cycle_per_au in the VPS is set equal to 1, and vps_poc_cycle_au is signaled in the VPS. In this case, slice_poc_cycle_au is not explicitly signaled, and the AUC value 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 equal to 0. In this case, vps_access_unit_cnt is not signaled, but slice_access_unit_cnt is signaled in the slice header for each slice or picture. Each slice or picture may have a different value of slice_access_unit_cnt. The AUC value per AU is calculated by dividing the POC value by slice_poc_cycle_au. Figure 10 shows a block diagram illustrating the related work flow.

[0133] In the same or other embodiments, pictures, slices, or tiles corresponding to AUs having the same AUC value may be associated with the same decoding or output time instance, even though the POC values ​​of the pictures, slices, or tiles may differ. Thus, all or some of the pictures, slices, or tiles associated with the same AU may be decoded in parallel and output at the same time instance, without inter-parse / inter-decoding dependencies across pictures, slices, or tiles within the same AU.

[0134] In the same or other embodiments, pictures, slices, or tiles corresponding to AUs with the same AUC value may be associated with the same composition / display time instance, even though the POC values ​​of the pictures, slices, or tiles may be different. If the composition time is included in the container format, pictures can be displayed at the same time instance if they have the same composition time, even if they correspond to different AUs.

[0135] 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 some of the pictures, slices, or tiles corresponding to a time instance may be associated with the same temporal sublayer. In the same or other embodiments, each picture, slice, or tile may have the same or different spatial layer ID (layer_id) within the same AU. All or some of the pictures, slices, or tiles corresponding to a time instance may be associated with the same or different spatial layers.

[0136] Figure 11 shows an exemplary video stream including a background video CSPS having a layer_id equal to 0 and a plurality of foreground CSPS layers. The coded subpicture may consist of one or more CSPS layers, but the background area that does not belong to any foreground CSPS layer may consist of the base layer. The base layer may include a background area and a foreground area, while the enhancement CSPS layer includes a foreground area. The enhancement CSPS layer may have better visual quality than the base layer in the same area. The enhancement CSPS layer may refer to the reconstructed pixels and the motion vectors of the base layer corresponding to the same area.

[0137] In the same or another embodiment, the video bitstream corresponding to the base layer is included in a track, and the CSPS layer corresponding to each subpicture is included in a separate track within the video file.

[0138] In the same or another embodiment, the video bitstream corresponding to the base layer is included in a track, and the CSPS layers having the same layer_id are included in separate tracks. In this example, the track corresponding to layer k includes only the CSPS layer corresponding to layer k.

[0139] In the same or another embodiment, each CSPS layer of each subpicture is stored in a separate track. Each track (trach) may or may not have a parse dependency or a decoding dependency from one or more other tracks.

[0140] [[ID=十六]]In the same or another embodiment, each track may include a bitstream corresponding to the CSPS layers from layer i to layer j of all or part of the subpicture, where 0 < i ≤ j ≤ k, and k is the top layer of the CSPS.

[0141] In the same or another embodiment, a picture consists of one or more associated media data including a depth map, an alpha map, 3D shape data, an occupancy map, etc. Such associated timed media data may be divided into one or more data sub-streams, each corresponding to one sub-picture.

[0142] In the same or another embodiment, Figure 12 illustrates an example of a video conference based on a multi-layer sub-picture method. The video stream includes one base layer video bitstream corresponding to a background picture and one or more enhancement layer video bitstreams corresponding to foreground sub-pictures. Each enhancement layer video bitstream corresponds to a CSPS layer. On the display, the picture corresponding to the base layer is displayed by default, including picture-in-picture (PIP) views of one or more users. When a user is selected under client control, the enhancement CSPS layer corresponding to the selected user is decoded and displayed with enhanced quality or spatial resolution. Figure 13 illustrates an operational diagram.

[0143] In the same or another embodiment, a middlebox (such as a router) in the network may select some of the layers to send to a user depending on its bandwidth. The picture / subpicture organization may be used for bandwidth adaptation. For example, if a user does not have the bandwidth, the router may strip out layers or select some subpictures according to their importance or based on the setup used, and do this dynamically to accommodate the bandwidth.

[0144] Figure 14 shows a use case for 360-degree video. When a spherical 360-degree picture is projected onto a planar picture, the projected 360-degree picture may be divided into multiple sub-pictures as a base layer. Enhancement layers for specific sub-pictures may be encoded and sent to the client. A decoder can decode both the base layer containing all sub-pictures and the enhancement layer for a selected sub-picture. If the current viewport is the same as the selected sub-picture, the displayed picture may have higher quality with the decoded sub-picture with the enhancement layer. Otherwise, the decoded picture with the base layer may be displayed with lower quality.

[0145] In the same or another embodiment, any layout information for display may be present in the file as supplemental information (such as an SEI message 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, or may be regenerated by a network entity or cloud server, or may be determined by a user's customized settings.

[0146] In one embodiment, when an input picture is divided into one or more (rectangular) sub-regions, each sub-region may be coded as an independent layer. Each independent layer corresponding to a local region may have a unique layer_id value. For each independent layer, sub-picture size and position information may be signaled, such as picture size (width, height) and offset information of the top-left corner (x_offset, y_offset). Figure 15 shows an example of a layout of divided sub-pictures, their sub-picture size and position information, and their corresponding picture prediction structure. Layout information, including sub-picture size(s) and sub-picture position(s), may be signaled in a high-level syntax structure, such as parameter set(s), slice or tile group header, or SEI message.

[0147] In the same embodiment, each sub-picture corresponding to an independent layer may have its own POC value within the AU. When a reference picture among the pictures stored in the DPB is indicated using one or more syntax elements in the RPS or RPL structure, the POC value(s) of each sub-picture corresponding to the layer may be used.

[0148] In the same or another embodiment, the layer_id may not be used to indicate the (inter-layer) prediction structure, and the POC (delta) value may be used.

[0149] In the same embodiment, a sub-picture with 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 sub-picture with 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 the number K may be equal to the maximum number of (independent) layers, which may be the same as the number of sub-regions.

[0150] In the same or another embodiment, Figure 16 shows an extended case of Figure 15. When an input picture is divided into multiple (e.g., four) sub-regions, each local region may be coded with one or more layers. In this case, the number of independent layers may be equal to the number of sub-regions, and one or more layers may correspond to a sub-region. Thus, each sub-region may be coded using one or more independent layers and zero or more dependent layers.

[0151] In the same embodiment, in Figure 16, the input picture may be divided into four sub-regions. The top-right sub-region may be coded as two layers, Layer 1 and Layer 4, and the bottom-right sub-region may be coded as two layers, Layer 3 and Layer 5. In this case, Layer 4 may refer to Layer 1 for motion compensation prediction, and Layer 5 may refer to Layer 3 for motion compensation.

[0152] In the same or another embodiment, in-loop filtering (such as deblocking filtering, adaptive in-loop filtering, reshaper, bilateral filter, or any deep learning based filtering) across layer boundaries may (optionally) be disabled.

[0153] In the same or another embodiment, motion compensated prediction or intrablock copying across layer boundaries may (optionally) be disabled.

[0154] In the same or another embodiment, boundary padding for motion-compensated prediction or in-loop filtering at sub-picture boundaries may be optionally processed. A flag indicating whether boundary padding is processed may be signaled in a high-level syntax structure, such as parameter set(s) (VPS, SPS, PPS, or APS), slice or tile group header, or SEI message.

[0155] In the same or another embodiment, layout information for sub-region(s) (or sub-picture(s)) may be signaled in the VPS or SPS. Figure 17 shows an example of syntax elements for the VPS and SPS. In this example, vps_sub_picture_dividing_flag is signaled in the VPS. This flag may indicate whether the input picture(s) are divided into multiple sub-regions. When the value of vps_sub_picture_dividing_flag is equal to 0, the input picture(s) in the coded video sequence(s) corresponding to the current VPS may not 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(s) 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(s), respectively.

[0156] In some embodiments, 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 compositing and display.

[0157] 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 be signaled in the SPS corresponding to (a) a specific 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 specific layer. Also, the location of the upper-left corner of the sub-region (pic_offset_x, pic_offset_y) may be signaled in the SPS.

[0158] In the same embodiment, the position information (pic_offset_x, pic_offset_y) of the upper left corner of the sub-region may not be used for decoding, but may be used for compositing and display.

[0159] In the same or another embodiment, layout information (size and position) of all or part of a subregion(s) of an input picture(s), and dependency information between a layer(s) may be signaled in a parameter set or an SEI message. Figure 18 shows an example of syntax elements indicating information about the layout of a subregion, the dependency between layers, and the relationship between a subregion and one or more layers. In this example, the syntax element num_sub_region indicates the number of (rectangular) subregions in the current coded video sequence. The syntax element num_layers indicates the number of layers in the current coded video sequence. The value of num_layers may be equal to or greater than the value of num_sub_region. If any subregion is coded as a single layer, the value of num_layers may be equal to the value of num_sub_region. If one or more subregions 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 jth layer to the ith layer. num_layers_for_region[i] indicates the number of layers associated with the i-th subregion. sub_region_layer_id[i][j] indicates the layer_id of the j-th layer associated with the i-th subregion. The 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.

[0160] In one embodiment, one or more syntax elements specifying an output layer set to indicate one of multiple layers to be output with or without profile tier-level information may be signaled in a high-level syntax structure, such as a VPS, DPS, SPS, PPS, APS, or SEI message. Referring to Figure 19, a syntax element num_output_layer_sets indicating the number of output layer sets (OLSs) in a coded video sequence that references a VPS may be signaled in the VPS. For each output layer set, an output_layer_flag may be signaled as many times as the number of output layers.

[0161] 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.

[0162] In the same or another embodiment, 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 a VPS, DPS, SPS, PPS, APS, or SEI message. Further referring to Figure 19, a syntax element num_profile_tile_level indicating the number of profile tier level information for each OLS in a coded video sequence that references the VPS may be signaled in 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 information among the entries in the profile tier level information, may be signaled in the same number as the number of output layers.

[0163] In the same embodiment, profile_tier_level_idx[i][j] specifies an index into the list of profile_tier_level() syntax structures in the VPS for the profile_tier_level() syntax structure that applies to the jth layer of the ith OLS.

[0164] In the same or another embodiment, referring to FIG. 20, the syntax elements num_profile_tile_level and / or num_output_layer_sets may be signaled if the maximum number of layers is greater than 1 (vps_max_layers_minus1>0).

[0165] In the same or another embodiment, referring to FIG. 20, there may be a syntax element vps_output_layers_mode[i] in the VPS that indicates the mode of output layer signaling for the i-th output layer set.

[0166] In the same embodiment, vps_output_layers_mode[i] equal to 0 specifies that only the top layer is output in the i output layer set. vps_output_layer_mode[i] equal to 1 specifies that all layers are output in the i output layer set. vps_output_layer_mode[i] equal to 2 specifies that the layers output are those in the i output layer set with vps_output_layer_flag[i][j] equal to 1. More values ​​may be reserved.

[0167] In the same embodiment, output_layer_flag[i][j] may or may not be signaled depending on the value of vps_output_layers_mode[i] for the i-th output layer set.

[0168] In the same or another embodiment, referring to Figure 20, a flag vps_ptl_signal_flag[i] may be present for the i-th output layer set. Depending on the value of vps_ptl_signal_flag[i], profile tier level information for the i-th output layer set may or may not be signaled.

[0169] In the same or another embodiment, referring to FIG. 21, the number of sub-pictures in the current CVS, max_subpics_minus1, may be signaled in a high-level syntax structure, such as a VPS, DPS, SPS, PPS, APS, or SEI message.

[0170] In the same embodiment, referring to FIG. 21, if the number of sub-pictures is greater than 1 (max_subpics_minus1>0), the sub-picture identifier sub_pic_id[i] of the i-th sub-picture may be signaled.

[0171] In the same or another embodiment, one or more syntax elements indicating sub-picture identifiers belonging to each layer of each output layer set may be signaled in the VPS. Referring to Figure 22, sub_pic_id_layer[i][j][k] indicates the kth sub-picture present in the jth layer of the ith output layer set. With this information, the decoder may know which sub-pictures can be decoded and output for each layer of a particular output layer set.

[0172] In one embodiment, a picture header (PH) is a syntax structure that contains syntax elements that apply to all slices of a coded picture. A picture unit (PU) is a set of NAL units that are associated with each other according to specified classification rules, are consecutive in decoding order, and contain exactly one coded picture. A PU may contain a picture header (PH) and one or more VCL NAL units that make up a coded picture.

[0173] In one embodiment, the SPS (RBSP) may be available to the decoding process before being referenced, may be included in at least one AU with TemporalId equal to 0, or may be provided via external means.

[0174] In one embodiment, the SPS (RBSP) may be available to the decoding process before being referenced, may be included in at least one AU with TemporalId equal to 0 in the CVS that contains one or more PPSs that reference the SPS, or may be provided via external means.

[0175] In one embodiment, the SPS (RBSP) may be available to the decoding process before being referenced by one or more PPSs, and may be included in at least one PU with a nuh_layer_id equal to the lowest nuh_layer_id value of a PPS NAL unit that references an SPS NAL unit in a CVS, including one or more PPSs that reference the SPS, or may be provided via external means.

[0176] In one embodiment, the SPS (RBSP) may be available to the decoding process before being referenced by one or more PPSs, and may be included in at least one PU with TemporalId equal to 0 and nuh_layer_id equal to the lowest nuh_layer_id value of the PPS NAL units that reference the SPS NAL unit, or may be provided via external means.

[0177] In one embodiment, the SPS (RBSP) may be available to the decoding process before being referenced by one or more PPSs, and may be included 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 a PPS NAL unit that references an SPS NAL unit in a CVS, including one or more PPSs that reference the SPS, or may be provided via external means.

[0178] In the same or another embodiment, pps_seq_parameter_set_id specifies the value of sps_seq_parameter_set_id of the referenced SPS. The value of pps_seq_parameter_set_id may be the same in all PPSs referenced by coded pictures within a CLVS.

[0179] In the same or another embodiment, all SPS NAL units with a particular value of sps_seq_parameter_set_id in a CVS may have the same content.

[0180] In the same or another embodiment, regardless of the nuh_layer_id value, SPS NAL units may share the same value space for sps_seq_parameter_set_id.

[0181] In the same or another embodiment, the nuh_layer_id value of an SPS NAL unit may be equal to the lowest nuh_layer_id value of the PPS NAL units that reference the SPS NAL unit.

[0182] In one embodiment, if an SPS with nuh_layer_id equal to m is referenced by one or more PPSs with nuh_layer_id equal to n, the layer with nuh_layer_id equal to m may be the same as the (direct or indirect) reference layer of the layer with nuh_layer_id equal to n or the layer with nuh_layer_id equal to m.

[0183] In one embodiment, the PPS (RBSP) shall be available to the decoding process before being referenced and shall be contained in at least one AU with TemporalId equal to the TemporalId of the PPS NAL unit or provided via external means.

[0184] In one embodiment, the PPS (RBSP) may be available to the decoding process before being referenced, may be included in at least one AU with a TemporalId equal to the TemporalId of the PPS NAL unit in the CVS that contains one or more PHs (or coded slice NAL units) that reference the PPS, or may be provided via external means.

[0185] In one embodiment, the PPS (RBSP) may be available to the decoding process before being referenced by one or more PHs (or coded slice NAL units), and may be included in at least one PU with a nuh_layer_id equal to the lowest nuh_layer_id value of the coded slice NAL units that reference the PPS NAL units in the CVS, including one or more PHs (or coded slice NAL units) that reference the PPS, or may be provided via external means.

[0186] In one embodiment, the PPS (RBSP) may be available to the decoding process before being referenced by one or more PHs (or coded slice NAL units) and may be included in at least one PU having 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 units that reference the PPS NAL unit in the CVS, including one or more PHs (or coded slice NAL units) that reference the PPS, or may be provided via external means.

[0187] In the same or another embodiment, ph_pic_parameter_set_id in PH specifies the value of pps_pic_parameter_set_id of the referenced PPS in use. The value of pps_seq_parameter_set_id may be the same in all PPSs referenced by coded pictures in CLVS.

[0188] In the same or another embodiment, all PPS NAL units with a particular value of pps_pic_parameter_set_id within a PU shall have the same content.

[0189] In the same or another embodiment, PPS NAL units may share the same value space for pps_pic_parameter_set_id regardless of the nuh_layer_id value.

[0190] In the same or another embodiment, 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 NAL units that reference the PPS NAL unit.

[0191] In one embodiment, when a PPS with nuh_layer_id equal to m is referenced by one or more coded slice NAL units with nuh_layer_id equal to n, the layer with nuh_layer_id equal to m may be the same as the (direct or indirect) reference layer of the layer with nuh_layer_id equal to n or the layer with nuh_layer_id equal to m.

[0192] In one embodiment, the PPS (RBSP) shall be available to the decoding process before being referenced and shall be contained in at least one AU with TemporalId equal to the TemporalId of the PPS NAL unit or provided via external means.

[0193] In one embodiment, the PPS (RBSP) may be available to the decoding process before being referenced, may be included in at least one AU with a TemporalId equal to the TemporalId of the PPS NAL unit in the CVS that contains one or more PHs (or coded slice NAL units) that reference the PPS, or may be provided via external means.

[0194] In one embodiment, the PPS (RBSP) may be available to the decoding process before being referenced by one or more PHs (or coded slice NAL units), and may be included in at least one PU with a nuh_layer_id equal to the lowest nuh_layer_id value of the coded slice NAL units that reference the PPS NAL units in the CVS, including one or more PHs (or coded slice NAL units) that reference the PPS, or may be provided via external means.

[0195] In one embodiment, the PPS (RBSP) may be available to the decoding process before being referenced by one or more PHs (or coded slice NAL units) and may be included in at least one PU having 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 units that reference the PPS NAL unit in the CVS, including one or more PHs (or coded slice NAL units) that reference the PPS, or may be provided via external means.

[0196] In the same or another embodiment, ph_pic_parameter_set_id in PH specifies the value of pps_pic_parameter_set_id of the referenced PPS in use. The value of pps_seq_parameter_set_id may be the same in all PPSs referenced by coded pictures in CLVS.

[0197] In the same or another embodiment, all PPS NAL units with a particular value of pps_pic_parameter_set_id within a PU shall have the same content.

[0198] In the same or another embodiment, PPS NAL units may share the same value space for pps_pic_parameter_set_id regardless of the nuh_layer_id value.

[0199] In the same or another embodiment, 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 NAL units that reference the PPS NAL unit.

[0200] In one embodiment, when a PPS with nuh_layer_id equal to m is referenced by one or more coded slice NAL units with nuh_layer_id equal to n, the layer with nuh_layer_id equal to m may be the same as the (direct or indirect) reference layer of the layer with nuh_layer_id equal to n or the layer with nuh_layer_id equal to m.

[0201] In one embodiment, if the flag no_temporal_sublayer_switching_flag is signaled in a DPS, VPS, or SPS, the TemporalId value of a PPS referencing a parameter set containing the flag equal to 1 may be equal to 0, while the TemporalId value of a PPS referencing a parameter set containing the flag equal to 1 may be greater than or equal to the TemporalId value of the parameter set.

[0202] In one embodiment, each PPS (RBSP) may be available to the decoding process before being referenced and may be included in at least one AU with a TemporalId that is less than or equal to the TemporalId of the coded slice NAL unit (or PH NAL unit) that references it, or may be provided via external means. If a PPS NAL unit is included in an AU that precedes an AU that contains a coded slice NAL unit that references the PPS, there may not be a VCL NAL unit that enables temporal upper layer switching or a VCL NAL unit with nal_unit_type equal to STSA_NUT after the PPS NAL unit and before a coded slice NAL unit that references an APS, indicating that the picture in the VCL NAL unit may be a gradual temporal sub-layer access (STSA) picture.

[0203] In the same or another embodiment, the PPS NAL unit and the coded slice NAL unit (and its PH NAL unit) that references the PPS may be included in the same AU.

[0204] In the same or another embodiment, the PPS NAL unit and the STSA NAL unit may be included in the same AU that precedes the coded slice NAL unit (and its PH NAL unit) that references the PPS.

[0205] In the same or another embodiment, the STSA NAL unit, the PPS NAL unit, and the coded slice NAL unit that references the PPS (and its PH NAL unit) may reside in the same AU.

[0206] In the same embodiment, the TemporalId value of a VCL NAL unit containing a PPS may be equal to the TemporalId value of the preceding STSA NAL unit.

[0207] In the same embodiment, the picture order count (POC) value of the PPS NAL unit may be greater than or equal to the POC value of the STSA NAL unit.

[0208] In the same embodiment, the picture order count (POC) value of a coded slice or PH NAL unit that references a PPS NAL unit may be greater than or equal to the POC value of the referenced PPS NAL unit.

[0209] In one embodiment, since all VCL NAL units in an AU have the same TemporalId value, the value of sps_max_sublayers_minus1 shall be the same across all layers in a coded video sequence. The value of sps_max_sublayers_minus1 shall be the same in all SPSs referenced by coded pictures in a CVS.

[0210] In one embodiment, the chroma_format_idc value of an SPS referenced by one or more coded pictures in layer A shall be equal to the chroma_format_idc value in the SPS referenced by one or more coded pictures in layer B if layer A is a direct reference layer for layer B. This is because any coded picture has the same chroma_format_idc value as its reference picture. The chroma_format_idc value of an SPS referenced by one or more coded pictures in layer A shall be equal to the chroma_format_idc value in the SPS referenced by one or more coded pictures in layer A's direct reference layers in the CVS.

[0211] In one embodiment, the subpics_present_flag and sps_subpic_id_present_flag values ​​of an SPS referenced by one or more coded pictures in layer A shall be equal to the subpics_present_flag and sps_subpic_id_present_flag values ​​in an SPS referenced by one or more coded pictures in layer B if layer A is a direct reference layer of layer B. This is because the layout of subpictures needs to be aligned or related across layers. Otherwise, subpictures with multiple layers may not be extracted correctly. The subpics_present_flag and sps_subpic_id_present_flag values ​​of an SPS referenced by one or more coded pictures in layer A shall be equal to the subpics_present_flag and sps_subpic_id_present_flag values ​​in the SPS referenced by one or more coded pictures in the direct reference layer of layer A in the CVS.

[0212] In one embodiment, if an STSA picture in layer A is referenced by a picture in a direct reference layer of layer A in the same AU, the picture referencing the STSA shall be the STSA picture. Otherwise, upward switching of temporal sublayers cannot be synchronized between layers. If an STSA NAL unit in layer A is referenced by a VCL NAL unit in a direct reference layer of layer A in the same AU, the nal_unit_type value of the VCL NAL unit referencing the STSA NAL unit shall be equal to STSA_NUT.

[0213] In one embodiment, if an RASL picture in layer A is referenced by a picture in a direct reference layer of layer A in the same AU, the picture referencing the RASL shall be an RASL picture. Otherwise, the picture cannot be correctly decoded. If an RASL NAL unit in layer A is referenced by a VCL NAL unit of a direct reference layer of layer A in the same AU, the nal_unit_type value of the VCL NAL unit referencing the RASL NAL unit shall be equal to RASL_NUT.

[0214] While this disclosure describes several exemplary embodiments, there are alterations, substitutions, and various substitute equivalents that fall within the scope of this disclosure. Thus, it will be appreciated that those skilled in the art can devise numerous systems and methods that, although not explicitly shown or described herein, embody the principles of the present disclosure and are therefore within its spirit and scope. [Explanation of symbols]

[0215] 100 Communication Systems 110 First Terminal 120 Second Terminal 130 terminals 140 terminals 150 Network 201 Video Sources 202 Sample Stream 203 Encoder 204 Video Bitstream 205 Streaming Server 206 Streaming Client 207 Video Bitstream 208 Streaming Client 209 Video Bitstream 210 Video Decoder 211 video sample streams 212 Display, Rendering Devices 213 Capture Subsystem 310 Receiver 312 channels 315 Buffer Memory 320 Entropy Decoder / Parser 321 Symbol 351 Scaler / Descaler Unit 352 Intra-picture prediction unit 353 Motion Compensation Prediction Unit 355 Aggregator 356 Loop filter unit, current reference picture 357 Reference Picture Memory (Buffer) 430 Source Coder 432 Coding Engine 433 Local Decoder 434 Reference Picture Memory 435 Predictor 440 Transmitter 443 coded video sequence 445 Entropy Coder 450 Controller 460 Communication Channels 501 Picture Header 502 ARC information 503 H.263 PLUSPTYPE header extension 504 Picture Parameter Set 505 ARC Reference Information 506 Table 507 Sequence Parameter Set 508 Tile Group Header 509 ARC information 511 parameter sets 512 ARC information 513 ARC Reference Information 514 Tile Group Header 515 ARC information 516 Parameter Set, ARC Information Table 601 Tile Group Header 602 Syntax element dec_pic_size_idx 603 Adaptive Resolution 610 Sequence Parameter Set 611 adaptive_pic_resolution_change_flag 612 parameter sets Output resolution in 613 samples 614 Syntax element reference_pic_size_present_flag 615 Reference Picture Dimensions 616 table_direction(num_dec_pic_size_in_luma_samples_minus1) 617 Syntax, Table Entry 700 Computer Systems 701 Keyboard 702 Mouse 703 Trackpad 704 Data Gloves 705 Joystick 706 Microphone 707 Scanner 708 Camera 709 Speaker 710 Touchscreen, Screen 720 CD / DVD ROM / RW 721 Medium 722 thumb drive 723 Removable Hard Drive or Solid State Drive 740 cores 741 Central Processing Unit (CPU) 742 Graphics Processing Unit (GPU) 743 Field Programmable Gate Area (FPGA) 744 Hardware Accelerator 745 Read-Only Memory (ROM) 746 Random Access Memory 747 Core internal mass storage unit 748 System Bus 749 Peripheral Bus

Claims

1. An encoding method for encoding video data having one or more layers using a processor, A step of encoding a first syntactic element that defines multiple modes specifying one or more output layers from among one or more layers associated with each of one or more sets of output layers, Includes, The first syntactic element is, A first mode in which only the topmost layer among the one or more layers associated with the specified output layer set is designated as the output layer. A second mode in which all of the one or more layers associated with the specified output layer set are designated as output layers, and A third mode in which a second syntactic element is signaled, associated with each of the one or more layers associated with the specified output layer set. It stipulates, The second syntactic element, when 1, designates the associated layer as the output layer, and when 0, does not designate the associated layer as the output layer. Encoding method.

2. The step of encoding the second syntactic element for each of the one or more output layer sets and for each of the one or more associated layers, when the first syntactic element is in the third mode. The encoding method according to claim 1, further comprising:

3. A step of encoding a third syntactic element that defines a subpicture identifier corresponding to each layer associated with each of the one or more output layer sets. The encoding method according to claim 1, further comprising:

4. An encoding method for encoding video data having one or more layers using a processor, The step of generating and transmitting a bitstream encoded from the aforementioned video data, The step of generating and transmitting the bitstream is: A step of encoding a first syntactic element that defines multiple modes specifying one or more output layers from among one or more layers associated with each of one or more sets of output layers, Includes, The first syntactic element is, A first mode in which only the topmost layer among the one or more layers associated with the specified output layer set is designated as the output layer. A second mode in which all of the one or more layers associated with the specified output layer set are designated as output layers, and A third mode in which a second syntactic element is signaled, associated with each of the one or more layers associated with the specified output layer set. It stipulates, The second syntactic element, when 1, designates the associated layer as the output layer, and when 0, does not designate the associated layer as the output layer. Encoding method.

5. An encoding device configured to perform the encoding method described in any one of Claims 1 to 4.

6. A program for causing a computer to perform the encoding method described in any one of claims 1 to 4.

7. A method for decoding video data having one or more layers by a processor, Receive or retrieve a first syntax element that defines multiple modes specifying one or more output layers from among the one or more layers associated with each of one or more sets of output layers, If the first syntactic element is in the first mode, then only the topmost layer among the one or more layers associated with the specified output layer set is decoded as an output layer. If the first syntactic element is in the second mode, all of the one or more layers associated with the specified output layer set are decoded as output layers. If the first syntactic element is in third mode, the second syntactic element associated with each of the one or more layers associated with the specified output layer set is further received or obtained; if the second syntactic element is 1, the associated layer is decoded as the output layer; if the second syntactic element is 0, the associated layer is not decoded as the output layer. Decryption method.

8. A decoding device configured to perform the decoding method described in Claim 7.

9. A program for causing a computer to execute the decryption method described in Claim 7.

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