Techniques for signaling constraint flags for range extension

Abstract

Aspects of the present disclosure provide a method and apparatus for video data processing. In some examples, the apparatus for video data processing includes a processing circuit. The processing circuit determines that profile information of a bitstream indicates a profile for an operating range extension with a bit depth higher than a predetermined value. The processing circuit then checks at least syntax elements of the bitstream to determine whether the syntax elements satisfy a constraint indicating a single layer for output at a decoder for decoding the bitstream.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Patent Application No. 17 / 710,694, "TECHNIQUES FOR CONSTRAINT FLAG SIGNALING FOR RANGE EXTENSION," filed March 31, 2022, which claims the benefit of priority to U.S. Provisional Application No. 63 / 250,096, "TECHNIQUES FOR CONSTRAINT FLAG SIGNALING FOR RANGE EXTENSION," filed September 29, 2021. The disclosures of the prior applications are incorporated herein by reference in their entireties.

[0002] This disclosure generally describes embodiments related to video coding. [Background technology]

[0003] The background discussion provided herein is intended to provide a general context for the present disclosure. The inventors' work is not admitted expressly or impliedly as prior art to the present disclosure, to the extent that it is described in this background section, and aspects of the description that may not be admitted as prior art at the time of filing.

[0004] Video coding and decoding can be performed using inter-picture prediction with motion compensation. Uncompressed digital video can include a sequence of pictures, each with spatial dimensions of, for example, 1920x1080 luma samples and associated chroma samples. The sequence of pictures can have a fixed or variable (also informally known as frame rate) picture rate, for example, 60 pictures per second or 60 Hz. Uncompressed video has specific bitrate requirements. For example, 1080p60 4:2:0 video (1920x1080 luma sample resolution at a frame rate of 60 Hz) at 8 bits per sample requires a bandwidth approaching 1.5 Gbit / s. One hour of such video requires more than 600 gigabytes of storage space.

[0005] One goal of video coding and decoding may be to reduce redundancy in the input video signal through compression. Compression may help reduce the aforementioned bandwidth and / or storage space requirements, in some cases by more than one order of magnitude. Both lossless and lossy compression may be employed, as well as combinations thereof. Lossless compression refers to techniques that can restore an exact copy of the original signal from the compressed original signal. With lossy compression, the restored signal may not be identical to the original signal, but the distortion between the original and restored signals is small enough to make the restored signal useful for the intended application. For video, lossy compression is widely adopted. The amount of acceptable distortion depends on the application, e.g., users of a particular consumer streaming application may tolerate higher distortion than users of a television distribution application. The achievable compression ratio may reflect that the greater the acceptable / tolerable distortion, the higher the compression ratio may be.

[0006] Video encoders and decoders can utilize techniques from a number of broad categories, including, for example, motion compensation, transform, quantization, and entropy coding.

[0007] Video codec technology can include a technique known as intra-coding. In intra-coding, sample values ​​are represented without reference to samples or other data from previously reconstructed reference pictures. In some video codecs, a picture is spatially subdivided into blocks of samples. When all blocks of samples are coded in intra mode, the picture may be an intra picture. Intra pictures, and their derivatives, such as independent decoder refresh pictures, can be used to reset the decoder state, and therefore can be used as the first picture in a coded video bitstream and video session, or as still images. Samples of an intra block may be subjected to a transform, and the transform coefficients may be quantized before entropy coding. Intra prediction may be a technique that minimizes sample values ​​in the pre-transform domain. In some cases, the smaller the DC value after the transform and the smaller the AC coefficients, the fewer bits are required at a given quantization step size to represent the block after entropy coding.

[0008] Conventional intra-coding, such as that known from MPEG-2 generation coding techniques, does not use intra-prediction. However, some newer video compression techniques include techniques that attempt to predict from surrounding sample data and / or metadata obtained during the encoding / decoding of a block of data that is spatially adjacent and preceding in decoding order. Such techniques are hereafter referred to as "intra-prediction" techniques. It should be noted that in at least some cases, intra-prediction uses only reference data from the current picture being reconstructed, and not from a reference picture.

[0009] Intra prediction may take many different forms. When more than one of such techniques may be used in a given video coding technique, the technique in use may be coded in an intra prediction mode. In certain cases, a mode may have sub-modes and / or parameters, which may be coded separately or may be included in the mode codeword. Which codeword is used for a given mode / sub-mode / parameter combination may affect the coding efficiency gains from intra prediction, and therefore may affect the entropy coding technique used to convert the codeword into a bitstream.

[0010] Certain modes of intra prediction were introduced from H.264, improved in H.265, and further improved in newer coding techniques such as Joint Search Model (JEM), Versatile Video Coding (VVC), and Benchmark Set (BMS). A predictor block can be formed using neighboring sample values ​​belonging to already available samples. The sample values ​​of the neighboring samples are copied to the predictor block according to a direction. The reference to the direction in use may be coded in the bitstream or may itself be predicted.

[0011] Referring to FIG. 1A, depicted at the bottom right is a subset of 9 predictor directions known from the 33 possible predictor directions (corresponding to the 33 angle modes of the 35 intra modes) of H.265. The point (101) where the arrows converge represents the sample being predicted. The arrows represent the direction from which the sample is predicted. For example, arrow (102) indicates that sample (101) is predicted from one or more samples to the upper right at an angle of 45 degrees from the horizontal. Similarly, arrow (103) indicates that sample (101) is predicted from one or more samples to the lower left of sample (101) at an angle of 22.5 degrees from the horizontal.

[0012] 1A, at the top left is depicted a square block (104) of 4x4 samples (indicated by a thick dashed line). The square block (104) contains 16 samples, each labeled with "S", its position in the Y dimension (e.g., row index), and its position in the X dimension (e.g., column index). For example, sample S21 is the second sample (from the top) in the Y dimension and the first sample (from the left) in the X dimension. Similarly, sample S44 is the fourth sample in both the Y and X dimensions in the block (104). Since the block is 4x4 samples in size, S44 is at the bottom right. Also shown are reference samples that follow a similar numbering scheme. The reference samples are labeled with R, their Y position (e.g., row index), and X position (column index) relative to the block (104). In both H.264 and H.265, the predicted samples are adjacent to the block being reconstructed, so negative values ​​do not need to be used.

[0013] Intra-picture prediction can work by copying reference sample values ​​from adjacent samples as assigned by the signaled prediction direction. For example, assume that the coded video bitstream includes signaling for this block indicating a prediction direction that coincides with the arrow (102), i.e., the sample is predicted from one or more prediction samples located at an angle of 45 degrees from the horizontal and to the upper right. In that case, samples S41, S32, S23, and S14 are predicted from the same reference sample R05. Then, sample S44 is predicted from reference sample R08.

[0014] In certain cases, especially when the orientation is not evenly divisible by 45 degrees, the values ​​of multiple reference samples may be combined, for example by interpolation, to calculate the reference sample.

[0015] The number of possible directions has increased as video coding techniques have developed. In H.264 (2003), nine different directions could be represented. In H.265 (2013), this increased to 33, and at the time of this disclosure, JEM / VVC / BMS can support up to 65 directions. Experiments have been conducted to identify the most likely directions, and certain techniques of entropy coding are used to represent those likely directions with a small number of bits, accepting a certain penalty for the less likely directions. Furthermore, the direction itself can sometimes be predicted from neighboring directions used in adjacent already decoded blocks.

[0016] FIG. 1B shows a schematic diagram (180) depicting 65 intra prediction directions with JEM to illustrate the increasing number of prediction directions over time.

[0017] The mapping of intra-prediction direction bits in a coded video bitstream that represent the direction may vary from one video coding technique to another, and can range, for example, from a simple direct mapping of prediction directions to intra-prediction modes, to complex adaptation schemes involving codewords, most likely modes, and similar techniques. In all cases, however, there may be certain directions that are statistically less likely to occur in the video content than certain other directions. Because the goal of video compression is to reduce redundancy, these less likely directions are represented by more bits than more likely directions in well-performing video coding techniques.

[0018] Motion compensation may be a lossy compression technique and may refer to a technique in which blocks of sample data from a previously reconstructed picture or part thereof (reference picture) are used to predict a newly reconstructed picture or part of a picture after being spatially shifted in a direction indicated by a motion vector (hereafter MV). In some cases, the reference picture may be the same as the picture currently being reconstructed. The MV may have two dimensions X and Y, or three dimensions, the third of which is an indication of the reference picture in use (the latter may indirectly be a temporal dimension).

[0019] In some video compression techniques, the MV applicable to a particular region of sample data can be predicted from other MVs, e.g., from an MV associated with another region of sample data that is spatially adjacent to the region being restored and precedes that MV in decoding order. Doing so can significantly reduce the amount of data required to code the MV, thereby eliminating redundancy and increasing the compression ratio. For example, when coding an input video signal derived from a camera (known as natural video), MV prediction can work effectively because there exists a statistical possibility that a region larger than the region to which a single MV is applicable moves in a similar direction, and thus, in some cases, can be predicted using similar motion vectors derived from MVs of neighboring regions. As a result, the detected MV for a given region is similar or the same as the MV predicted from the surrounding MVs, and after entropy coding, can be represented with fewer bits than would be used to code the MV directly. In some cases, MV prediction can be an example of lossless compression of a signal (i.e., MV) derived from the original signal (i.e., sample stream). In other cases, the MV prediction itself can be lossy, e.g., due to rounding errors when computing a predictor from several surrounding MVs.

[0020] Various MV prediction mechanisms are described in H.265 / HEVC (ITU-T Rec. H.265, "High Efficiency Video Coding", December 2016). Among the many MV prediction mechanisms that H.265 offers, the one described herein is a technique hereafter referred to as "spatial merging".

[0021] Referring to Figure 2, a current block (201) contains samples that the encoder found during the motion search process to be predictable from a spatially shifted previous block of the same size. Instead of directly coding its MV, the MV can be derived from metadata associated with one or more reference pictures, e.g., the most recent reference picture (in decoding order), using the MV associated with any one of five surrounding samples, denoted A0, A1, and B0, B1, B2 (202-206, respectively). In H.265, MV prediction can use predictors from the same reference picture that neighboring blocks use. Summary of the Invention [Means for solving the problem]

[0022] Aspects of the present disclosure provide a method and apparatus for video data processing. In some examples, the apparatus for video data processing includes a processing circuit. The processing circuit determines that profile information of a bitstream indicates a profile for an operating range extension with a bit depth higher than a predetermined value. The processing circuit then checks at least syntax elements of the bitstream to determine whether the syntax elements of the bitstream satisfy a constraint indicating a single layer for output at a decoder for decoding the bitstream.

[0023] In some embodiments, the processing circuit checks a first syntax element indicating a maximum number of layers in a referenced video parameter set (VPS) to determine whether the value of the first syntax element satisfies a constraint. In one example, the processing circuit checks a first syntax element equal to the maximum number of layers in the VPS minus 1 to determine whether the value of the first syntax element is equal to 0.

[0024] In some embodiments, the processing circuit checks a second syntax element of the sequence parameter set (SPS) that is an identifier for a video parameter set (VPS) to which the SPS refers to determine whether the value of the second syntax element satisfies a constraint. In one example, the processing circuit checks a second syntax element of the SPS to determine whether the value of the second syntax element is equal to 0.

[0025] In some embodiments, the processing circuit checks a third syntax element indicating enabling / disabling of multi-layer extensions in the bitstream to determine whether the value of the third syntax element satisfies the constraint. In one example, the processing circuit checks the third syntax element to determine whether the value of the third syntax element indicates disabling of multi-layer extensions.

[0026] In some examples, the processing circuit checks at least one of a syntax element indicating a bit depth, a syntax element indicating an index associated with a chroma format, a syntax element indicating enabling / disabling of palette mode, a syntax element indicating use / non-use of extended dynamic range, a syntax element indicating the presence / absence of a transform skip flag in the residual coding syntax, a syntax element indicating use / non-use of Rice coding in regular residual coding, a syntax element indicating enabling / disabling of persistent Rice parameter adaptation, and a syntax element indicating a scan pattern from the last significant coefficient to determine whether a constraint associated with the profile is satisfied.

[0027] In some examples, in response to the profile being a still image profile, the processing circuit checks whether the bitstream includes only one picture.

[0028] In some examples, the processing circuitry checks a syntax element indicating a level of the bitstream to determine whether the level satisfies a constraint.

[0029] Aspects of the present disclosure also provide a non-transitory computer-readable medium storing instructions that, when executed by a computer for video decoding, cause the computer to perform a method for video decoding.

[0030] Further features, nature and various advantages of the disclosed subject matter will become more apparent from the following detailed description and the accompanying drawings. [Brief description of the drawings]

[0031] [Figure 1A] FIG. 2 is a schematic diagram of an example subset of intra-prediction modes. [Figure 1B] FIG. 2 is a diagram of an example intra-prediction direction. [Diagram 2] FIG. 2 is a schematic diagram of a current block and its surrounding spatial merge candidates in one example. [Diagram 3] 1 is a schematic diagram of a simplified block diagram of a communication system (300), according to one embodiment. [Figure 4] FIG. 4 is a schematic diagram of a simplified block diagram of a communication system (400) according to one embodiment. [Diagram 5] FIG. 2 is a schematic diagram of a simplified block diagram of a decoder according to one embodiment. [Figure 6] FIG. 2 is a schematic diagram of a simplified block diagram of an encoder according to one embodiment. [Figure 7] FIG. 4 is a block diagram of an encoder according to another embodiment. [Figure 8]FIG. 4 is a block diagram of a decoder according to another embodiment. [Figure 9] FIG. 1 illustrates an example of signaling adaptive resolution change (ARC) parameters according to an embodiment of the present disclosure. [Figure 10] FIG. 10 shows an example of a table (1000) for mapping up- or down-sample coefficients, codewords, and Ext-Golomb codes. [Figure 11] FIG. 11 illustrates several examples of ARC parameter signaling in accordance with some embodiments of the present disclosure. [Figure 12] A diagram illustrating an example syntax structure of a set of PTL syntax elements in some examples. [Figure 13] A diagram illustrating an example syntax structure of general constraint information in some examples. [Figure 14A] A diagram showing an example of PTL information including a PTL syntax structure and a general constraint information syntax structure according to some embodiments of the present disclosure. [Figure 14B] A diagram showing an example of PTL information including a PTL syntax structure and a general constraint information syntax structure according to some embodiments of the present disclosure. [Figure 15A] FIG. 2 illustrates an example of a general constraint information syntax structure according to one embodiment of the present disclosure. [Figure 15B] FIG. 2 illustrates an example of a general constraint information syntax structure according to one embodiment of the present disclosure. [Figure 16] A diagram illustrating an example syntax structure of a sequence parameter set (SPS) range extension in accordance with some embodiments of the present disclosure. [Figure 17] FIG. 13 shows an example of a table containing allowed values ​​for some syntax elements in a profile for an extended operating range with high bit depth. [Figure 18] 1 is a flowchart outlining a process according to one embodiment of the present disclosure. [Figure 19] FIG. 1 is a schematic diagram of a computer system according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] FIG. 3 shows a simplified block diagram of a communication system (300) according to one embodiment of the present disclosure. The communication system (300) includes, for example, a plurality of terminal devices that can communicate with each other via a network (350). For example, the communication system (300) includes a first pair of terminal devices (310) and (320) interconnected via the network (350). In the example of FIG. 3, the first pair of terminal devices (310) and (320) perform unidirectional transmission of data. For example, the terminal device (310) can encode video data (e.g., a stream of video pictures captured by the terminal device (310)) for transmission to another terminal device (320) via the network (350). The encoded video data can be transmitted in the form of one or more coded video bitstreams. The terminal device (320) can receive the coded video data from the network (350), decode the coded video data to reconstruct the video pictures, and display the video pictures according to the reconstructed video data. Unidirectional data transmission may be common, such as in media serving applications.

[0033] In another example, the communication system (300) includes a second pair of terminal devices (330) and (340) performing a bidirectional transmission of coded video data, such as may occur during a video conference. In the case of a bidirectional transmission of data, in one example, each of the terminal devices (330) and (340) can code video data (e.g., a stream of video pictures captured by the terminal device) for transmission to the other of the terminal devices (330) and (340) over the network (350). Each of the terminal devices (330) and (340) can also receive coded video data transmitted by the other of the terminal devices (330) and (340), can decode the coded video data to recover the video pictures, and can display the video pictures on an accessible display device according to the recovered video data.

[0034] In the example of FIG. 3, the terminal devices (310), (320), (330), and (340) may be depicted as a server, a personal computer, and a smartphone, although the principles of the present disclosure may not be so limited. Embodiments of the present disclosure find application with laptop computers, tablet computers, media players, and / or dedicated video conferencing equipment. The network (350) represents any number of networks that convey coded video data between the terminal devices (310), (320), (330), and (340), including, for example, wired (wired) and / or wireless communication networks. The communication network (350) may exchange data over circuit-switched and / or packet-switched channels. Representative networks include telecommunications networks, local area networks, wide area networks, and / or the Internet. For purposes of this description, the architecture and topology of the network (350) may not be important to the operation of the present disclosure unless otherwise described herein below.

[0035] 4 shows an arrangement of a video encoder and a video decoder in a streaming environment as one example for 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 television, storage of compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0036] The streaming system may include a video source (401), e.g., a capture subsystem (413) that may include a digital camera, for example, that creates a stream of uncompressed video pictures (402). In one example, the stream of video pictures (402) includes samples taken by a digital camera. The stream of video pictures (402), depicted as thick lines to emphasize a larger amount of data compared to the encoded video data (404) (or coded video bitstream), may be processed by an electronic device (420) that includes a video encoder (403) coupled to the video source (401). The video encoder (403) 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 data (404) (or coded video bitstream (404)), depicted as thin lines to emphasize a smaller amount of data compared to the stream of video pictures (402), may be stored in a streaming server (405) for future use. One or more streaming client subsystems, such as the client subsystems (406) and (408) of FIG. 4, can access the streaming server (405) to retrieve copies (407) and (409) of the encoded video data (404). The client subsystem (406) can include, for example, a video decoder (410) in an electronic device (430). The video decoder (410) decodes an input copy (407) of the encoded video data and creates an output stream (411) of video pictures that can be rendered on a display (412) (e.g., a display screen) or other rendering device (not depicted). In some streaming systems, the encoded video data (404), (407), and (409) (e.g., a video bitstream) can be encoded according to a particular video coding / compression standard. Examples of such standards include ITU-T Recommendation H.265.In one example, the developing video coding standard is informally known as Versatile Video Coding (VVC), and the disclosed subject matter may be used in the context of VVC.

[0037] It should be noted that the electronic devices (420) and (430) may include other components (not shown). For example, the electronic device (420) may include a video decoder (not shown), and the electronic device (430) may also include a video encoder (not shown).

[0038] 5 shows a block diagram of a video decoder (510) according to one embodiment of the present disclosure. The video decoder (510) may be included in an electronic device (530). The electronic device (530) may include a receiver (531) (e.g., a receiving circuit). The video decoder (510) may be used in place of the video decoder (410) of the example of FIG. 4.

[0039] The receiver (531) may receive one or more coded video sequences, in the same or another embodiment, one coded video sequence at a time, to be decoded by the video decoder (510), 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 (501), which may be a hardware / software link to a storage device that stores the coded video data. The receiver (531) may receive the coded video data along with other data, e.g., coded audio data and / or auxiliary data streams, that may be forwarded to their respective using entities (not depicted). The receiver (531) may separate the coded video sequences from the other data. To combat network jitter, a buffer memory (515) may be coupled between the receiver (531) and the entropy decoder / parser (520) (hereinafter "parser (520)"). In certain applications, the buffer memory (515) is part of the video decoder (510). In other applications, it may be outside the video decoder (510) (not depicted). In still other applications, there may be a buffer memory (not depicted) outside the video decoder (510), e.g., to combat network jitter, plus another buffer memory (515) inside the video decoder (510), e.g., to handle playout timing. When the receiver (531) is receiving data from a store / forward device of sufficient bandwidth and controllability, or from an isosynchronous network, the buffer memory (515) may not be needed or may be small. For use with best-effort packet networks such as the Internet, the buffer memory (515) may be needed, may be relatively large, may be advantageously adaptively sized, and may be at least partially implemented in an operating system or similar element (not depicted) outside the video decoder (510).

[0040] The video decoder (510) may include a parser (520) to recover symbols (521) from the coded video sequence. These categories of symbols include information used to manage the operation of the video decoder (510) and potentially information for controlling a rendering device such as a rendering device (512) (e.g., a display screen) that is not an integral part of the electronic device (530) but may be coupled to the electronic device (530) as shown in FIG. 5. The control information for the rendering device may be in the form of a supplemental enhancement information (SEI message) or a video usability information (VUI) parameter set fragment (not depicted). The parser (520) may parse / entropy decode the received coded video sequence. The coding of the coded video sequence may follow a video coding technique or standard and may follow a variety of principles including variable length coding, Huffman coding, arithmetic coding, etc., with or without context sensitivity. The parser (520) can extract a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder from the coded video sequence based on at least one parameter corresponding to the group. The subgroups can include groups of pictures (GOPs), pictures, tiles, slices, macroblocks, coding units (CUs), blocks, transform units (TUs), prediction units (PUs), etc. The parser (520) can also extract information from the coded video sequence, such as transform coefficients, quantizer parameter values, motion vectors, etc.

[0041] The parser (520) can perform entropy decoding / parsing operations on the video sequence received from the buffer memory (515) to create symbols (521).

[0042] The recovery of the symbols (521) can involve several different units, depending on the type of coded video picture or part thereof (such as inter-picture and intra-picture, inter-block and intra-block, etc.), as well as other factors. Which units are involved and how can be controlled by subgroup control information parsed from the coded video sequence by the parser (520). The flow of such subgroup control information between the parser (520) and the following units is not depicted for the sake of clarity.

[0043] Beyond the functional blocks already mentioned, the video decoder (510) may be conceptually subdivided into several functional units, as described below. In an actual implementation operating under commercial constraints, many of these units may interact closely with each other and may be at least partially integrated with each other. However, for purposes of describing the disclosed subject matter, the following conceptual subdivision into functional units is appropriate.

[0044] The first unit is a scalar / inverse transform unit (551). The scalar / inverse transform unit (551) receives quantized transform coefficients as well as control information from the parser (520) including which transform to use, block size, quantization coefficients, quantization scaling matrices, etc. as symbols (521). The scalar / inverse transform unit (551) can output blocks containing sample values ​​that can be input to an aggregator (555).

[0045] In some cases, the output samples of the scalar / inverse transform (551) 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 (552). In some cases, the intra-picture prediction unit (552) generates a block of the same size and shape as the block being reconstructed using surrounding already reconstructed information fetched from a current picture buffer (558). The current picture buffer (558) buffers, for example, a partially reconstructed current picture and / or a fully reconstructed current picture. The aggregator (555) adds, possibly on a sample-by-sample basis, the prediction information generated by the intra-prediction unit (552) to the output sample information provided by the scalar / inverse transform unit (551).

[0046] In other cases, the output samples of the scalar / inverse transform unit (551) may relate to an inter-coded, potentially motion-compensated block. In such cases, the motion compensated prediction unit (553) may access the reference picture memory (557) to fetch samples used for prediction. After motion compensating the fetched samples according to the symbols (521) related to the block, these samples may be added to the output of the scalar / inverse transform unit (551) by the aggregator (555) to generate output sample information (in this case referred to as residual samples or residual signals). The addresses in the reference picture memory (557) from which the motion compensated prediction unit (553) fetches the prediction samples may be controlled by motion vectors available to the motion compensated prediction unit (553) in the form of symbols (521), which may have, for example, X, Y, and reference picture components. Motion compensation may also include interpolation of sample values ​​fetched from the reference picture memory (557) when sub-sample accurate motion vectors are used, motion vector prediction mechanisms, etc.

[0047] The output samples of the aggregator (555) may be subjected to various loop filtering techniques in a loop filter unit (556). Video compression techniques may include in-loop filter techniques that are controlled by parameters contained in the coded video sequence (also called the coded video bitstream) and made available to the loop filter unit (556) as symbols (521) from the parser (520), but may also be responsive to previously reconstructed and loop filtered sample values ​​as well as to meta-information obtained during decoding of previous portions (in decoding order) of the coded picture or coded video sequence.

[0048] The output of the loop filter unit (556) may be a sample stream that can be stored in a reference picture memory (557) for use in future inter-picture prediction as well as output to a rendering device (512).

[0049] Once a particular coded picture is fully reconstructed, it can be used as a reference picture for future prediction. For example, once a coded picture corresponding to a current picture is fully reconstructed and the coded picture is identified (e.g., by the parser (520)) as a reference picture, the current picture buffer (558) can become part of the reference picture memory (557), and any unused current picture buffer can be reallocated before beginning reconstruction of the next coded picture.

[0050] The video decoder (510) may perform decoding operations according to a given video compression technique in a standard such as ITU-T Rec. H.265. The coded video sequence may conform to the syntax specified by the video compression technique or standard being used in the sense that the coded video sequence adheres to both the syntax of the video compression technique or standard and the profile documented in the video compression technique. Specifically, the profile may select some tools from all tools available in the video compression technique or standard as the only tools available for use under that profile. Also, what is required for conformance may be that the complexity of the coded video sequence is within a range defined by the level of the video compression technique or standard. In some cases, the level limits the maximum picture size, maximum frame rate, maximum reconstructed sample rate (e.g., measured in megasamples per second), maximum reference picture size, etc. The limits set by the level may be further limited in some cases by the specification of a hypothetical reference decoder (HRD) and metadata for HRD buffer management signaled within the coded video sequence.

[0051] In one embodiment, the receiver (531) can receive additional (redundant) data along with the encoded video. The additional data may be included as part of the coded video sequence. The additional data may be used by the video decoder (510) to properly decode the data and / or to more accurately recover the original video data. The additional data may be in the form of, for example, temporal, spatial, or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0052] 6 shows a block diagram of a video encoder (603) according to one embodiment of the present disclosure. The video encoder (603) is included in an electronic device (620). The electronic device (620) includes a transmitter (640) (e.g., a transmission circuit). The video encoder (603) can be used in place of the video encoder (403) of the example of FIG. 4.

[0053] The video encoder (603) can receive video samples from a video source (601) (which is not part of the electronic device (620) in the example of FIG. 6) that can capture video images that are encoded by the video encoder (603). In another example, the video source (601) is part of the electronic device (620).

[0054] The video source (601) may provide a source video sequence that is coded by the video encoder (603) in the form of a digital video sample stream that may 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 (601) may be a storage device that stores previously prepared video. In a video conferencing system, the video source (601) 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 in sequence. 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 can easily understand the relationship between pixels and samples. The following description focuses on samples.

[0055] According to one embodiment, the video encoder (603) can code and compress pictures of a source video sequence into a coded video sequence (643) in real-time or under any other time constraint required by an application. Enforcing an appropriate coding rate is one function of the controller (650). In some embodiments, the controller (650) controls and is operatively coupled to other functional units described below. For clarity, coupling is not depicted. Parameters set by the controller (650) can 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. The controller (650) can be configured to have other appropriate functions associated with the video encoder (603) optimized for a particular system design.

[0056] In some embodiments, the video encoder (603) is configured to operate in a coding loop. As an oversimplified explanation, in one example, the coding loop can include a source coder (630) (e.g., responsible for creating symbols, such as a symbol stream, based on an input picture to be coded and a reference picture), as well as a (local) decoder (633) embedded in the video encoder (603). The decoder (633) reconstructs the symbols to create sample data in a manner similar to that which the (remote) decoder also does (since any compression between the symbols and the coded video bitstream is lossless in the video compression techniques considered in the disclosed subject matter). The reconstructed sample stream (sample data) is input to a reference picture memory (634). Since the decoding of the symbol stream leads to a bit-exact result regardless of the location of the decoder (local or remote), the contents in the reference picture memory (634) are also bit-exact between the local and remote encoders. In other words, the predictive part of the encoder "sees" exactly the same sample values ​​as the decoder "sees" when using prediction during decoding. This basic principle of reference picture synchrony (and the resulting drift when synchrony cannot be maintained, for example due to channel errors) is also used in several related techniques.

[0057] The operation of the "local" decoder (633) may be the same as the operation of a "remote" decoder, such as the video decoder (510), already described in detail above in conjunction with Figure 5. However, and with brief reference to Figure 5, because symbols are available and the encoding / decoding of symbols into a coded video sequence by the entropy coder (645) and parser (520) may be lossless, the entropy decoding portion of the video decoder (510), including the buffer memory (515), and the parser (520), may not be fully implemented in the local decoder (633).

[0058] An observation that can be made at this point is that any decoder technology other than parsing / entropy decoding present in a decoder must necessarily be present in a corresponding encoder in substantially identical functional form. For this reason, the disclosed subject matter focuses on the operation of the decoder. A description of the encoder technology can be omitted, since it is the inverse of the decoder technology described generically. Only in certain areas is more detailed description required and is provided below.

[0059] In operation, in some examples, the source coder (630) may perform motion-compensated predictive coding, which predictively codes an input picture with reference to one or more previously coded pictures from a video sequence designated as “reference pictures.” In this manner, the coding engine (632) codes differences between pixel blocks of the input picture and pixel blocks of reference pictures that may be selected as predictive references for the input picture.

[0060] The local video decoder (633) can decode the coded video data of the pictures that may be designated as reference pictures based on the symbols created by the source coder (630). The operation of the coding engine (632) may advantageously be a lossy process. When the coded video data may be decoded in a video decoder (not shown in FIG. 6), the reconstructed video sequence may be a replica of the source video sequence, usually with some errors. The local video decoder (633) can replicate the decoding process that may be performed by the video decoder on the reference pictures, such that the reconstructed reference pictures are stored in the reference picture memory (634). In this way, the video encoder (603) can locally store copies of reconstructed reference pictures that have common content as reconstructed reference pictures obtained by a far-end video decoder (without transmission errors).

[0061] The predictor (635) may perform a prediction search for the coding engine (632). That is, for a new picture to be coded, the predictor (635) may search the reference picture memory (634) for sample data (as candidate reference pixel blocks) or specific metadata such as reference picture motion vectors, block shapes, etc., that may serve as suitable prediction references for the new picture. The predictor (635) may operate on sample blocks on a pixel block by pixel block basis to find suitable prediction references. In some cases, as determined by the search results obtained by the predictor (635), the input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory (634).

[0062] The controller (650) can manage the coding operations of the source coder (630), including, for example, setting the parameters and subgroup parameters used to encode the video data.

[0063] The output of all the aforementioned functional units may undergo entropy coding in an entropy coder (645), which converts the symbols produced by the various functional units into a coded video sequence by losslessly compressing the symbols according to techniques such as Huffman coding, variable length coding, arithmetic coding, etc.

[0064] The transmitter (640) can buffer the coded video sequence created by the entropy coder (645) and prepare it for transmission over a communication channel (660), which may be a hardware / software link to a storage device that stores the coded video data. The transmitter (640) can merge the coded video data from the video coder (603) with other data to be transmitted, such as coded audio data and / or auxiliary data streams (sources not shown).

[0065] The controller (650) can manage the operation of the video encoder (603). During coding, the controller (650) can assign a particular coded picture type to each coded picture, which may affect the coding techniques that may be applied to the respective picture. For example, pictures may often be assigned as one of the following picture types:

[0066] An intra picture (I-picture) may be a picture that can be coded and decoded without using any other picture in a sequence as a source of prediction. Some video codecs allow various types of intra pictures, including, for example, independent decoder refresh ("IDR") pictures. Those skilled in the art are aware of these variations of I-pictures, as well as their respective uses and characteristics.

[0067] A predictive 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 sample values ​​for each block.

[0068] A bidirectionally predicted picture (B-picture) may be a picture that can be coded and decoded using intra- or inter-prediction that uses at most two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, a multi-prediction picture may use more than two reference pictures and associated metadata for the reconstruction of a single block.

[0069] A source picture may typically be spatially subdivided into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples each) and 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 respective picture of the block. For example, blocks of an I picture may be non-predictively coded or they may be predictively coded with reference to already coded blocks of the same picture (spatial or intra prediction). Pixel blocks of a P picture may be predictively coded via spatial prediction or via temporal prediction with reference to one previously coded reference picture. Blocks of a B picture may be predictively coded via spatial prediction or via temporal prediction with reference to one or two previously coded reference pictures.

[0070] The video encoder (603) may perform coding operations in accordance with a given video coding technique or standard, such as ITU-T Rec. H.265. In its operations, the video encoder (603) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancy in the input video sequence. Thus, the coded video data may conform to a syntax specified by the video coding technique or standard being used.

[0071] In one embodiment, the transmitter (640) can transmit additional data along with the coded video. The source coder (630) may include such data as part of the coded video sequence. The additional data may include temporal / spatial / SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, SEI messages, VUI parameter set fragments, etc.

[0072] Video may be captured as multiple source pictures (video pictures) in a time sequence. Intra-picture prediction (often abbreviated as intra prediction) exploits spatial correlation within a given picture, while inter-picture prediction exploits correlation (temporal or other) between pictures. In one example, a particular picture being encoded / decoded, called the current picture, is divided into blocks. When a block in the current picture is similar to a reference block in a reference picture that was previously coded and is still buffered in the video, the block in the current picture can be coded by a vector called a motion vector. The motion vector points to a reference block in the reference picture and may have a third dimension that identifies the reference picture if multiple reference pictures are used.

[0073] In some embodiments, bi-prediction techniques can be used in inter-picture prediction. According to bi-prediction techniques, two reference pictures, such as a first reference picture and a second reference picture, both of which are earlier in decoding order than the current picture in a video (but may be past and future in display order, respectively), are used. A block in the current picture can be coded by a first motion vector that points to a first reference block in the first reference picture and a second motion vector that points to a second reference block in the second reference picture. A block can be predicted by a combination of the first reference block and the second reference block.

[0074] Furthermore, merge mode techniques can be used in inter-picture prediction to improve coding efficiency.

[0075] According to some embodiments of the present disclosure, predictions such as inter-picture prediction and intra-picture prediction are performed on a block-by-block basis. For example, according to the HEVC standard, a picture in a sequence of video pictures is divided into coding tree units (CTUs) for compression, and the CTUs in a picture have the same size, such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTU includes three coding tree blocks (CTBs), one luma CTB and two chroma CTBs. Each CTU can be recursively quadtree partitioned into one or more coding units (CUs). For example, a 64×64 pixel CTU can be partitioned into one 64×64 pixel CU, or four 32×32 pixel CUs, or sixteen 16×16 pixel CUs. In one example, each CU is analyzed to determine the prediction type of the CU, such as an inter prediction type or an intra prediction type. The CU is partitioned into one or more prediction units (PUs) depending on the temporal and / or spatial predictability. Generally, each PU includes one luma prediction block (PB) and two chroma PBs. In one embodiment, prediction operations in coding (encoding / decoding) are performed in units of prediction blocks. Taking luma prediction block as an example of a prediction block, the prediction block includes a matrix of pixel values ​​(e.g., luma values) of 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, etc.

[0076] 7 shows a diagram of a video encoder (703) according to another embodiment of the present disclosure. The video encoder (703) is configured to receive a processed block of sample values ​​(e.g., a predictive block) in a current video picture in a sequence of video pictures and to encode the processed block into a coded picture that is part of a coded video sequence. In one example, the video encoder (703) is used in place of the video encoder (403) of the example of FIG. 4.

[0077] In an HEVC example, the video encoder (703) receives a matrix of sample values ​​for a processing block, such as a predictive block of 8×8 samples. The video encoder (703) determines whether the processing block is best coded using intra-mode, inter-mode, or bi-predictive mode, e.g., using rate-distortion optimization. When the processing block is coded in intra-mode, the video encoder (703) can code the processing block into a coded picture using intra-prediction techniques, and when the processing block is coded in inter-mode or bi-predictive mode, the video encoder (703) can code the processing block into a coded picture using inter-prediction or bi-prediction techniques, respectively. In certain video coding techniques, the merge mode may be an inter-picture prediction sub-mode in which motion vectors are derived from one or more motion vector predictors without the benefit of coded motion vector components outside the predictors. In certain other video coding techniques, there may be motion vector components applicable to the current block. In one example, the video encoder (703) includes other components, such as a mode decision module (not shown), to determine the mode of the processing block.

[0078] In the example of FIG. 7, the video encoder (703) includes an inter-encoder (730), an intra-encoder (722), a residual calculator (723), a switch (726), a residual encoder (724), a general controller (721), and an entropy encoder (725) coupled together as shown in FIG.

[0079] The inter-encoder (730) is configured to receive samples of a current block (e.g., a processing block), compare the block to one or more reference blocks in a reference picture (e.g., blocks in a previous picture and a subsequent picture), generate inter-prediction information (e.g., a description of redundancy information, motion vectors, merge mode information due to inter-coding techniques), and calculate an inter-prediction result (e.g., a prediction block) based on the inter-prediction information using any suitable technique. In some examples, the reference picture is a decoded reference picture that is decoded based on the coded video information.

[0080] The intra encoder (722) is configured to receive samples of a current block (e.g., a processing block), possibly compare the block with already coded blocks in the same picture, generate quantized coefficients after transformation, and possibly also generate intra prediction information (e.g., intra prediction direction information according to one or more intra encoding techniques). In one example, the intra encoder (722) also calculates intra prediction results (e.g., prediction blocks) based on the intra prediction information and reference blocks in the same picture.

[0081] The generic controller (721) is configured to determine generic control data and control other components of the video encoder (703) based on the generic control data. In one example, the generic controller (721) determines the mode of the block and provides a control signal to the switch (726) based on the mode. For example, when the mode is an intra mode, the generic controller (721) controls the switch (726) to select an intra mode result for use by the residual calculator (723) and controls the entropy encoder (725) to select intra prediction information and include the intra prediction information in the bitstream, and when the mode is an inter mode, the generic controller (721) controls the switch (726) to select an inter prediction result for use by the residual calculator (723) and controls the entropy encoder (725) to select inter prediction information and include the inter prediction information in the bitstream.

[0082] The residual calculator (723) is configured to calculate a difference (residual data) between the received block and a prediction result selected from the intra-encoder (722) or the inter-encoder (730). The residual encoder (724) is configured to operate on the residual data to encode the residual data and generate transform coefficients. In one example, the residual encoder (724) is configured to transform the residual data from the spatial domain to the frequency domain and generate transform coefficients. The transform coefficients then undergo a quantization process to obtain quantized transform coefficients. In various embodiments, the video encoder (703) also includes a residual decoder (728). The residual decoder (728) is configured to perform an inverse transform and generate decoded residual data. The decoded residual data can be used by the intra-encoder (722) and the inter-encoder (730) as appropriate. For example, the inter-encoder (730) can generate decoded blocks based on the decoded residual data and the inter-prediction information, and the intra-encoder (722) can generate decoded blocks based on the decoded residual data and the intra-prediction information. The decoded blocks are appropriately processed to generate decoded pictures, which may be buffered in a memory circuit (not shown) and used as reference pictures in some examples.

[0083] The entropy encoder (725) is configured to format the bitstream to include the encoded block. The entropy encoder (725) is configured to include various information in accordance with an appropriate standard, such as the HEVC standard. In one example, the entropy encoder (725) is configured to include in the bitstream general control data, selected prediction information (e.g., intra-prediction information or inter-prediction information), residual information, and other appropriate information. It should be noted that, in accordance with the disclosed subject matter, no residual information is present when coding a block in a merged sub-mode of either the inter-mode or the bi-prediction mode.

[0084] 8 shows a diagram of a video decoder (810) according to another embodiment of the present disclosure. The video decoder (810) is configured to receive coded pictures that are part of a coded video sequence and decode the coded pictures to generate reconstructed pictures. In one example, the video decoder (810) is used in place of the video decoder (410) of the example of FIG. 4.

[0085] In the example of FIG. 8, the video decoder (810) includes an entropy decoder (871), an inter decoder (880), a residual decoder (873), a reconstruction module (874), and an intra decoder (872) coupled together as shown in FIG.

[0086] The entropy decoder (871) may be configured to recover from the coded picture certain symbols that represent the syntax elements of which the coded picture is composed. Such symbols may include, for example, prediction information (e.g., intra prediction information or inter prediction information) that may identify the mode in which the block is coded (e.g., intra mode, inter mode, bi-predictive mode, merged sub-mode or another sub-mode, the latter two of which), certain samples or metadata used for prediction by the intra decoder (872) or the inter decoder (880), respectively, such as residual information in the form of quantized transform coefficients. In one example, when the prediction mode is an inter mode or a bi-predictive mode, the inter prediction information is provided to the inter decoder (880), and when the prediction type is an intra prediction type, the intra prediction information is provided to the intra decoder (872). The residual information may undergo inverse quantization and is provided to the residual decoder (873).

[0087] The inter decoder (880) is configured to receive the inter prediction information and to generate inter prediction results based on the inter prediction information.

[0088] The intra decoder (872) is configured to receive the intra prediction information and to generate a prediction result based on the intra prediction information.

[0089] The residual decoder (873) is configured to perform inverse quantization to extract inverse quantized transform coefficients, and process the inverse quantized transform coefficients to transform the residual from the frequency domain to the spatial domain. The residual decoder (873) may also require certain control information (to include quantizer parameters (QP)), which may be provided by the entropy decoder (871) (this may be only a small amount of control information, so the data path is not depicted).

[0090] The reconstruction module (874) is configured to combine, in the spatial domain, the residual output by the residual decoder (873) with a prediction result (possibly output by an inter-prediction module or an intra-prediction module) to form a reconstructed block that may be part of a reconstructed picture, which may be part of the reconstructed video. It should be noted that other suitable operations, such as a deblocking operation, may be performed to improve appearance.

[0091] It should be noted that the video encoders (403), (603), and (703) and the video decoders (410), (510), and (810) may be implemented using any suitable technique. In one embodiment, the video encoders (403), (603), and (703) and the video decoders (410), (510), and (810) may be implemented using one or more integrated circuits. In another embodiment, the video encoders (403), (603), and (603) and the video decoders (410), (510), and (810) may be implemented using one or more processors executing software instructions.

[0092] Aspects of this disclosure provide techniques for controlling coding tools and features through constraint flags in a coded video stream.

[0093] According to one aspect of the present disclosure, the picture size in the bitstream may remain the same or may change. In some related examples, video encoders and decoders may operate on a given picture size that is defined and remains constant for a coded video sequence (CVS), group of pictures (GOP), or similar multi-picture time frame. In one example, such as MPEG-2, system designs are known to change the horizontal resolution (and therefore the picture size) depending on factors such as scene activity, but only in I-pictures, and thus the picture size is typically defined and remains constant for a GOP. Resampling of reference pictures to use different resolutions in a CVS is known, for example, from ITU-T Rec. H.263 Annex P. However, the picture size in a CVS does not change, and only the reference pictures are resampled, potentially resulting in only a portion of the picture canvas being used (e.g., in the case of downsampling) or only a portion of the scene being captured (e.g., in the case of upsampling). In some instances, such as H.263 Annex Q, resampling of individual macroblocks by a factor of 2 in each dimension (e.g., above or below) is permitted. However, the picture size remains the same. As the size of the macroblocks may be fixed, for example, in H.263, the size of the macroblocks does not need to be signaled.

[0094] In some relevant examples, the picture size of the predicted picture may be changed. Examples such as VP9 allow resampling of reference pictures and changing the resolution of the entire picture. In some examples (e.g., Hendry et al., "On adaptive resolution change (ARC) for VVC," Joint Video Team document JVET-M0135-v1, January 9-19, 2019, which are incorporated herein in their entirety) allow resampling of the entire reference picture to a different resolution (e.g., higher or lower resolution). The different candidate resolutions may be coded within the sequence parameter set (SPS) and referenced by per-picture syntax elements within the picture parameter set (PPS).

[0095] According to one aspect of the present disclosure, a source video can be compressed by layered coding, which can encode a picture into a bitstream that includes one or more layers with different qualities, such as different resolutions. The bitstream can have syntax elements that specify which layer (or set of layers) can be output at the decoder side. The set of layers that are output can be defined as an output layer set. For example, in a video codec that supports multiple layers and scalability, one or more output layer sets can be signaled in a video parameter set (VPS). Syntax elements that specify a profile hierarchy level (PTL) for the entire bitstream or one or more output layer sets can be signaled in a VPS, a decoder parameter set (DPS), which may be referred to as decoder capability information (DCI) in some examples, an SPS, a PPS, an SEI message, etc. In the PTL information, there can be general constraint information that can specify constraints on a coding tool or function. It is desirable to efficiently represent and signal constraint information for various coding tools and functions.

[0096] In some examples, the term "subpicture" may be used to refer to a rectangular arrangement of samples, blocks, macroblocks, coding units, or similar entities that may be semantically grouped and coded separately at a modified resolution, for example. One or more subpictures may form a 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 examples, one or more coded subpictures may be assembled in the compressed domain without transcoding down to the sample level into a coded picture. In some examples, one or more coded subpictures may be extracted from a coded picture in the compressed domain.

[0097] In some examples, a mechanism that allows for changing the resolution of a picture or subpicture in a CVS, for example by reference picture resampling, may be referred to as adaptive resolution change (ARC). The control information used to perform adaptive resolution change may be referred to as ARC parameters. ARC parameters may include filter parameters, scaling factors, output and / or reference picture resolutions, various control flags, etc.

[0098] In some examples, ARC encoding / decoding is picture-based, so a set of control information (ARC parameters) is used to encode / decode a single semantically independent coded video picture. In some examples, ARC encoding / decoding is sub-picture-based, so multiple sub-pictures within a picture can be encoded / decoded with independent ARC parameters. Note that ARC parameters can be signaled using a variety of techniques.

[0099] FIG. 9 illustrates examples (e.g., options) of techniques for signaling ARC parameters according to some embodiments of the present disclosure. Coding efficiency, complexity, and architecture may vary from example to example. A video coding standard or technology may select one or more of the examples or other variations for signaling ARC parameters. The examples may not be mutually exclusive and may be interchanged based on application needs, standard technology, encoder choice, etc.

[0100] According to one aspect of the disclosure, the ARC parameters may be provided as classes of ARC parameters in various manners. In some examples, the classes of ARC parameters include upsampled and / or downsampled coefficients separated or combined in the X and Y dimensions. In one example, one or more short syntax elements may be coded that may point to tables that include the upsampled and / or downsampled coefficients.

[0101] In some examples, upsample and / or downsample coefficients are included that add a time dimension to indicate a constant rate of zooming in and / or zooming out for a given number of pictures. In one example, one or more short syntax elements may be coded that can point to a table that includes the upsample and / or downsample coefficients.

[0102] In some examples, the class of ARC parameters includes the resolution of the X or Y dimension in units of samples, blocks, macroblocks, CUs, or any other suitable granularity of input pictures, output pictures, reference pictures, coded pictures, combined or separate. In some examples, there are two or more resolutions used in video coding (e.g., one resolution for input pictures, another resolution for reference pictures), and a set of values ​​(corresponding to one of the resolutions) can be inferred from another set of values ​​(corresponding to another of the resolutions). The determination of the values ​​can be gated, for example, based on the use of a flag. The use of flags for gating is described in detail in further description.

[0103] In some examples, the class of ARC parameters includes warping coordinates similar to those used in H.263 Annex P with the appropriate granularity described above. H.263 Annex P defines an efficient way of coding the warping coordinates. Other efficient ways can be devised. For example, the variable length reversible Huffman style coding of the warping coordinates of Annex P can be replaced by an appropriate length binary coding, where the length of the binary codeword can be derived from the maximum picture size multiplied by a coefficient and offset by a value that allows warping outside the boundaries of the maximum picture size.

[0104] In some examples, the class of ARC parameters includes filter parameters for upsampling and / or downsampling. In one example, there is only a single filter for upsampling and / or downsampling. In another example, multiple filters can be used. In some examples, the filter parameters may be signaled to allow for further flexibility in filter design. The filter parameters may be selected using an index in a list of possible filter designs. The filters may be fully specified (e.g., by specifying a list of filter coefficients using a suitable entropy coding technique), the filters may be implicitly selected by an upsample ratio or downsample ratio signaled according to any of the mechanisms described above, etc.

[0105] In the following description, a finite set of upsample or downsample coefficients (the same coefficients used in both the X and Y dimensions) is used to indicate signaling ARC parameters via codewords. In some examples, the codewords can be variable length coded, for example, using Ext-Golomb codes for certain syntax elements in video coding specifications (e.g., H.264 and H.265).

[0106] FIG. 10 shows an example of a table (1000) for mapping up- or down-sample coefficients, codewords, and Ext-Golomb codes.

[0107] It should be noted that other similar mappings can be devised according to the use and function of the upscaling and downscaling mechanisms available in the video compression technology or standard. In some examples, Table 1 can be appropriately extended for additional values. The values ​​may be represented by entropy coding mechanisms other than Ext-Golomb codes, for example, using binary coding. In one example, entropy coding mechanisms other than Ext-Golomb codes may have certain advantages when the resampling factor is of interest external to the video processing engine (e.g., encoder and decoder), for example, by a media aware network element (MANE). When no change in resolution is required (e.g., the original / target resolution is 1 in Table 1), a short Ext-Golomb code (e.g., only a single bit shown in Table 1) can be selected, which may have coding efficiency advantages over, for example, using binary codes in the most general case.

[0108] According to one aspect of the present disclosure, a mapping table such as Table 1 may be configurable. For example, some items in Table 1 and corresponding semantics may be fully or partially configurable. For example, a basic outline of the mapping table is conveyed within a high-level parameter set such as an SPS or DPS. Alternatively or additionally, in some examples, one or more tables similar to Table 1 may be defined in a video coding technology or standard, and one of the tables may be selected, for example, via an SPS or DPS.

[0109] ARC information, such as upsample or downsample coefficients coded as described above, may be included in the syntax of a video coding technique or standard. Note that one or more codewords may be used to control other classes of ARC information, such as upsample or downsample filters. In some instances, a relatively large amount of data is required for the filters or other data structures.

[0110] 9, in an example (910) such as H.263 Annex P, the ARC information (912) may be in the form of four warping coordinates and is included in a picture header (911) such as an H.263 PLUSPTYPE (913) header extension. The example (910) may be applied when i) a picture header is available and ii) frequent changes of the ARC information are expected. However, the overhead when using H.263-style signaling such as that illustrated in the example (910) may be high, and since the picture header may be of a transitional nature, the scaling factor may not be applicable between picture boundaries.

[0111] Referring to FIG. 9, in an example (920) such as JVCET-M135-v1, ARC reference information (925) (e.g., index) can be placed in a PPS (924) and can point to a table (i.e., target resolution table) (926) that contains the target resolutions (e.g., resolutions 1-3). In one example, the table (926) is located inside an SPS (927). Placing the target resolutions in the table (926) in the SPS (927) can be justified by using the SPS as an interoperability negotiation point during capability exchange. The resolution can vary from one picture to another within a restricted set of values ​​(e.g., resolutions 1-3) in the table (926) by referencing (e.g., ARC reference information (925)) in the appropriate PPS (924).

[0112] 9 also illustrates additional techniques, such as examples (930), (940), and (950), that may be used to convey ARC information within a video bitstream. The techniques may be used individually or in appropriate combination within the same video coding technique or standard.

[0113] Referring to Figure 9, in an example (930), ARC information (939), such as a resampling factor (or zoom factor), may be present in a header, such as a slice header, a GOB header, a tile header, a tile group header, etc. For example, a tile group header (938) is shown in Figure 9. The technique illustrated by the example (930) can be used when the ARC information (939) can be coded with a small number of bits, such as a single variable-length ue(v) or a fixed-length codeword of a few bits.

[0114] In accordance with one aspect of the disclosure, having the ARC information (939) directly in a header (e.g., the tile group header (938) of FIG. 9, a slice header, or a tile header) can have an additional advantage in that the ARC information (939) can be applicable to, for example, a sub-picture represented by a corresponding tile group (or slice, tile) rather than to the entire picture. Additionally, in an example, even if a video compression technology or standard only envisions full-picture adaptive resolution change (as opposed to, for example, a tile group-based adaptive resolution change), example (930) can have certain advantages compared to example (910) in terms of error resiliency.

[0115] Referring to FIG. 9, in an example (940), the ARC information (942) may be present within a parameter set (941), such as a PPS, a header parameter set, a tile parameter set, an adaptation parameter set (APS), etc. For example, an APS (941) is shown in FIG. 9. In some examples, the scope of the parameter set (941) may not be greater than a picture, and may be, for example, a picture, a tile group, etc. The use of the ARC information (e.g., ARC information (942)) may be implicit via activation of an associated parameter set (e.g., APS (941)). For example, when a video coding technology or standard contemplates only picture-based ARC, a PPS or equivalent may be appropriate.

[0116] Referring to FIG. 9, in an example (950), the ARC reference information (953) may be present in a tile group header (954) or a similar data structure (e.g., a picture header, a slice header, a tile header, or a GOP header), as described above. For example, a tile group header (954) is shown in FIG. 9. The ARC reference information (953) can reference a subset of the ARC information (955) available in a parameter set (956) that has a scope beyond a single picture, such as, for example, an SPS, a DPS, etc. For example, an SPS (956) is shown in FIG. 9.

[0117] 11 illustrates some examples of ARC parameter signaling according to some embodiments of the present disclosure. FIG. 11 illustrates examples of syntax diagrams used in video coding standards. In one example, the notation of the syntax diagrams roughly follows C-style programming. Bold lines may indicate syntax elements present in the bitstream, and non-bold lines may indicate control flow or variable settings.

[0118] Referring to FIG. 11, the tile group header (1101) includes a syntax structure for a header applicable to a portion (e.g., a rectangular portion) of a picture. In one example, the tile group header (1101) can conditionally include a variable-length Exp-Golomb coding syntax element dec_pic_size_idx (1102) (depicted in bold). The presence of a syntax element (e.g., dec_pic_size_idx (1102)) in the tile group header (1101) can be gated based on, for example, an adaptive resolution represented by a flag (e.g., adaptive_pic_resolution_change_flag) (1103). The value of the flag (e.g., adaptive_pic_resolution_change_flag) (1103) is not depicted in bold, and thus the flag is present in the bitstream at the point where the flag in the syntax diagram appears. Whether adaptive resolution is used for a picture or part of a picture can be signaled within a high level syntax structure (eg, SPS (1110) in FIG. 11) inside or outside the bitstream.

[0119] Referring to FIG. 11, an excerpt of an SPS (1110) is shown. The SPS (1110) includes a first syntax element (1111) that is a flag (1111) (e.g., adaptive_pic_resolution_change_flag). When the flag (1111) is true, the flag (1111) can indicate the use of adaptive resolution, which may require specific control information. In one example, the specific control information is present conditionally based on the value of the flag (1111), as indicated by the if() statements (1112) in the SPS (1110) and the tile group header (1101).

[0120] When adaptive resolution is used, such as that shown in the example of FIG. 11, an output resolution (or output picture resolution) (1113) in samples can be coded. In one example, the output resolution (1113) is coded based on a width resolution (e.g., output_pic_width_in_luma_samples) and a height resolution (e.g., output_pic_height_in_luma_samples). A video coding technique or standard may define specific limitations on the value of the output resolution (1113). For example, a level definition may limit the total number of output samples (e.g., the product of output_pic_width_in_luma_samples and output_pic_height_in_luma_samples). In some examples, a video coding technology or standard, or an external technology or standard (e.g., a system standard), may restrict the numbering range for the width and / or height resolution (e.g., the width and / or height resolution is divisible by a power of 2), the aspect ratio of the width resolution to the height resolution (e.g., the ratio of the width resolution to the height resolution is 4:3 or 16:9), etc. In one example, the above restrictions may be introduced to facilitate hardware implementation.

[0121] In certain applications, an encoder can instruct a decoder to use a particular reference picture size rather than implicitly assuming that size is the output picture size. For example, a syntax element (e.g., reference_pic_size_present_flag) (1114) gates the conditional presence of a reference picture dimension (1115). The reference picture dimension (1115), in one example, can include both a width (e.g., reference_pic_width_in_luma_samples) and a height (e.g., reference_pic_height_in_luma_samples).

[0122] Also shown in Figure 11 are applicable decoded picture width and height tables. In one example, the number of entries in the table can be represented by a table indication (e.g., syntax element num_dec_pic_size_in_luma_samples_minus1) (1116). "minus1" can refer to the interpretation of the value of the syntax element (1116). For example, if the coded value is 0, there is one table entry. If the coded value is 5, there are six table entries. For each entry in the table, the decoded picture width and height are included as syntax elements (1117).

[0123] The table items represented by the syntax element (1117) can be indexed using the syntax element dec_pic_size_idx (1102) in the tile group header (1101), thus allowing different decoding sizes and zoom factors for each tile group.

[0124] According to one aspect of the present disclosure, certain video coding techniques or standards (e.g., VP9) may enable spatial scalability by implementing a certain form of reference picture resampling along with temporal scalability. In one embodiment, reference pictures are upsampled to a higher resolution using ARC-style techniques to form the base of a spatial enhancement layer. The upsampled pictures can be refined using normal prediction mechanisms (e.g., motion compensated prediction for inter prediction from the reference picture) at the higher resolution, e.g., to add detail.

[0125] In some examples, values ​​in a network abstraction layer (NAL) unit header, e.g., a temporal ID field, are used to indicate temporal layer information and spatial layer information. Using values ​​in a NAL unit header to indicate both temporal layer information and spatial layer information can enable the use of existing selected transport units (SFUs) for scalable environments without modification. For example, existing SFUs can be created and optimized for transport selected in temporal layers based on the temporal ID value in the NAL unit header. Then, in some examples, existing SFUs can be used for spatial scalability (e.g., spatial layer selection) without modification. In some examples, a mapping can be realized between the coded picture size and the temporal layers indicated by the temporal ID field in the NAL unit header.

[0126] According to one aspect of the present disclosure, some characteristics of the coded bitstream can be specified using profile, tier, and level (PTL) information, which includes profile, tier, level, and general constraint information. In some examples, a profile defines a subset of the bitstream's characteristics, such as color reproduction, resolution, additional video compression, etc. A video codec can define various profiles, such as a baseline profile (e.g., a simple profile with a low compression ratio), a high profile (a complex profile with a high compression ratio), a main profile (e.g., a profile with a medium compression ratio between the baseline profile and the high profile may be the default profile setting).

[0127] Additionally, tiers and levels can be used to specify certain constraints that define the bitstream in terms of maximum bitrate, maximum luma sample rate, maximum luma picture size, minimum compression ratio, maximum number of slices allowed, maximum number of tiles allowed, etc. Lower tiers are more constrained than higher tiers, and lower levels are more constrained than higher levels. In one example, a standard may define two tiers, Main and High. The Main tier is a tier lower than the High tier. The tiers are created to address different applications in terms of maximum bitrate. In one example, the Main tier is designed for most applications, and the High tier is designed for very demanding applications. A standard may define multiple levels. A level is a set of constraints for a bitstream. In one example, for levels below level 4, only the Main tier is allowed. In some examples, a decoder that complies with a given tier / level is required to be able to decode all bitstreams encoded for that tier / level and all lower tiers / levels.

[0128] The general constraint information may include constraint information regarding video source type, coding tool, and function. For example, the constraint flag may indicate whether inter-coding tool, intra-coding tool, DBF, entropy coding, transform, partition (e.g., tile, slice), buffer management, random access (e.g., IDR), parameter set (e.g., SPS, PPS), etc. are present or used in the coded video bitstream. The constraint information may be signaled within a parameter set (e.g., SPS, VPS, or DCI). The constraint flag may be signaled within a high-level syntax structure (e.g., SPS, VPS, DCI).

[0129] According to some aspects of the disclosure, PTL information can be associated with a scope (e.g., a portion of the coded video data within a bitstream). In some examples, PTL information can be specified, for example, for the entire bitstream, the CVS of the bitstream, each output layer set of the bitstream, etc., and can be signaled within a high-level syntax (HLS) structure, such as a VPS, DPS, DCI, SPS, PPS, APS, GOP, sequence, header, SEI message, etc.

[0130] In some examples, the high level syntax (HLS) is defined with respect to the block level. Block level coding tools can be used to decode pixels or samples in a picture to reconstruct the picture. Block level coding tools can include any suitable coding tools used to reconstruct coding blocks, such as coding tools for inter prediction (i.e., inter coding tools), coding tools for intra prediction (i.e., intra coding tools), adaptive loop filters (ALFs), deblocking filters (DBFs), entropy coding, transforms, etc.

[0131] High level syntax (HLS) can specify information about capabilities, system interfaces, picture level control of tools, buffer control, etc. For example, HLS can specify partitions (e.g., tiles, slices, subpictures), buffer management, random access (e.g., IDR, clean random access (CRA)), parameter sets (e.g., VPS, SPS, PPS, APS), reference picture resampling (RPR), scalability, etc. High level syntax can be above the block level.

[0132] The control information may have an appropriate level, such as SPS level tool control information, PPS level tool control information, sequence level control information, bitstream level control information, etc. In some examples, the PTL information is part of the control information and may be signaled as a constraint flag in the HLS structure to indicate control or constraint of the tool within the range corresponding to the HLS structure. For example, the constraint flag may be provided in one of the sequence level control information and the bitstream level control information. In one example, if a particular tool is disabled by a constraint flag in the HLS structure, the tool is not used to code blocks within the range corresponding to the HLS, for example.

[0133] 12 and 13 show an example of PTL information according to some embodiments of the present disclosure. Fig. 12 shows an example syntax structure of a set of PTL syntax elements (1200), and Fig. 13 shows an example syntax structure of general constraint information (1300).

[0134] In FIG. 12, the set of PTL syntax elements may include general_profile_idc, general_tier_flag, general_level_idc, num_sub_profiles, general_sub_profile_idc, sublayer_level_present_flag, ptl_alignment_0_bit, and sublayer_level_idc.

[0135] In Figure 13, the general constraint information may include multiple constraint flags. In one example, a constraint flag (e.g., intra_only_constraint_flag) (1305) equal to 1 indicates that the parameter sh_slice_type should be I (i.e., the slice is an intra slice). The parameter sh_slice_type is a parameter in the slice header that specifies the coding type of the slice between types I, P, and B. A constraint flag (e.g., intra_only_constraint_flag) (1305) equal to 0 imposes no constraint (e.g., sh_slice_type should be I) on all coded pictures within the PTL information where other information (e.g., profile_idc) may allow non-intra slices. In another example, a constraint flag (e.g., no_alf_constraint_flag) (1306) equal to 1 can indicate that sps_alf_enabled_flag is equal to 0 for all CVSs within the scope of the PTL information, and thus adaptive loop filtering is not used even if adaptive loop filtering is allowed based on, for example, the profile_idc. A constraint flag (e.g., no_alf_constraint_flag) (1306) equal to 0 does not impose the above constraint.

[0136] In another example, as shown in Fig. 13, a constraint flag (e.g., no_lossless_coding_tool_constraint_flag) (1301) may be signaled within the general constraint information. A constraint flag (e.g., no_lossless_coding_tool_constraint_flag) (1301) equal to 1 may indicate that coding tools related to lossless coding cannot be used within the scope of the PTL information containing that constraint flag (1301). A constraint flag (e.g., no_lossless_coding_tool_constraint_flag) (1301) equal to 0 does not impose the above constraint.

[0137] In another example, as shown in Fig. 13, a constraint flag (e.g., no_lossy_coding_tool_constraint_flag) (1302) may be signaled within the general constraint information. A constraint flag (e.g., no_lossy_coding_tool_constraint_flag) (1302) equal to 1 may indicate that coding tools related to lossy coding cannot be used within the scope of the PTL information containing that constraint flag (1302). A constraint flag (e.g., no_lossy_coding_tool_constraint_flag) (1302) equal to 0 does not impose the above constraint.

[0138] In one embodiment, when a constraint flag (e.g., no_lossy_coding_tool_constraint_flag) (1302) is equal to 1, the constraint flag (e.g., no_lossless_coding_tool_constraint_flag) (1301) may not be equal to 1. Alternatively, when a constraint flag (e.g., no_lossy_coding_tool_constraint_flag) (1301) is equal to 1, the constraint flag (e.g., no_lossy_coding_tool_constraint_flag) (1302) may not be equal to 1.

[0139] The multiple constraint flags in the general constraint information may be sorted in a particular order. The order may be set, for example, based on the likelihood of each mechanism and / or tool not being used within the PTL. The order may be referred to as a priority. The order may be presented in the general constraint information syntax structure from high priority to low priority, with a high priority indicating a high likelihood of non-use of the tool (or mechanism) and a low priority indicating a low likelihood of non-use of the tool (or mechanism). Additional factors influencing the order may include tools that are likely to be used only for a particular use case (e.g., tools for sub-picture, scalability, and / or interlace support), the impact of the tool on the encoder / decoder / implementation complexity, etc.

[0140] 14A-14B show examples of PTL information including an example syntax structure (1410) of a PTL syntax structure (also referred to as a PTL bracket) and an example syntax for a generic constraint information syntax structure (also referred to as a generic constraint information bracket) (1420) according to some embodiments of the present disclosure. In some examples, a syntax element (e.g., num_available_constraint_flags) indicating the number of constraint flags can be signaled. In one example, the syntax element indicating the number of constraint flags can be signaled within a PTL syntax structure, such as that shown by (1401) in the example syntax (1410) shown in FIG. 14A, which may be outside of the example syntax for the generic constraint information bracket (1420). Alternatively, the syntax element indicating the number of constraint flags can be signaled at the beginning of the generic constraint information bracket, such as at the beginning of the example syntax (1420). When a syntax element (e.g., num_available_constraint_flags) is present and the value of the syntax element (e.g., num_available_constraint_flags) is equal to N, the first N constraint flags may be present in the general constraint information syntax structure. Additionally, other constraint flags may not be present and may be inferred to be equal to specific values. N may be a non-negative integer.

[0141] In one embodiment, the value N (e.g., num_available_constraint_flags) ranges from 0 to the maximum number of constraint flags (e.g., the value of the parameter MaxNumConstraintFlags). The maximum number of constraint flags may be any positive integer. The value of the maximum number of constraint flags (e.g., MaxNumConstraintFlags) may be predefined to be 16, 32, 64, 128, etc. When the value N (e.g., num_available_constraint_flags) is equal to 0, no constraint flags are present in the general constraint information syntax structure. The coding of the value N (e.g., num_available_constraint_flags) may be selected such that the value N and the corresponding entropy coded representation for the constraint flags sum to a number that is divisible by 8 to ensure byte alignment.

[0142] In some examples, the constraint flags can be classified into one or more constraint information groups. Each constraint information group can include one or more constraint flags and can have a corresponding gating flag. The gating flag of the corresponding constraint information group can indicate whether the constraint flag in the corresponding constraint information group may be present. In one example, the gating flag can be referred to as a constraint group presence flag. Generally, the gating flag is associated with the corresponding constraint information group and associated with the constraint flag in the corresponding constraint information group. In one embodiment, the gating flag gates whether the constraint flag in the corresponding constraint information group is present (or signaled) in the constraint information. For example, if the gating flag of the corresponding constraint information group is equal to 1, the constraint flag corresponding to the constraint information group can be present, for example, in the general constraint information. If the gating flag of the corresponding constraint information group is equal to 0, the constraint flag corresponding to the constraint information group may not be present, for example, in the general constraint information. In one example, if all gating flags are equal to 0, no constraint flag is present.

[0143] Constraint flags can have different scopes. For example, the scope of a constraint flag in a DCI may be a coded video bitstream. The scope of a constraint flag in a VPS may be a CLVS with multiple layers. The scope of a constraint flag in an SPS may be a single CLVS.

[0144] 15A-15B show an example of a general constraint information syntax structure 1500 according to an embodiment of the present disclosure. The general constraint information syntax structure 1500 includes a flag that indicates general constraint information. Specifically, the general constraint information syntax structure (1500) includes one or more gate flags, such as a gate flag (e.g., general_frame_structure_constraint_group_flag) (1501), a gate flag (e.g., high_level_functionality_constraint_group_flag) (1502), a gate flag (e.g., scalability_constraint_group_flag) (1503), a gate flag (e.g., partitioning_constraint_group_flag) (1504), a gate flag (e.g., intra_coding_tool_constraint_group_flag) (1505), a gate flag (e.g., inter_coding_tool_constraint_group_flag) (1506), a gate flag (e.g., transform_contraint_group_flag) (1507), and a gate flag (e.g., inloop_filtering_constraint_group_flag) (1508) of FIG. 15A. As shown in FIG. 15A, one or more gate flags (eg, gate flags (1501)-(1508)) may be present at the beginning of the general constraint information syntax structure (1500).

[0145] A gate flag (e.g., general_frame_structure_constraint_group_flag) (1501) is associated with a constraint information group (1510) and is associated with constraint flags (1511)-(1514) within the constraint information group (1510). A gate flag (e.g., general_frame_structure_constraint_group_flag) (1501) equal to 1 may specify that constraint flags (1511)-(1514) within the constraint information group (1510) may be present.

[0146] The constraint information group (1510) (or constraint flags (1511)-(1514)) may be associated with an input source and a frame packing (e.g., filled frame or projected frame). With reference to FIG. 15A , the constraint flags (1511)-(1514) correspond to the general_non_packed_constraint_flag (1511), the general_frame_only_constraint_flag (1512), the general_non_projected_constraint_flag (1513), and the general_one_picture_only_constraint_flag (1514). Otherwise, a gate flag (e.g., the general_frame_structure_constraint_group_flag) (1501) equal to 0 may specify that the constraint flags (1511)-(1514) that are in the constraint information group (1510) may not be present in the general constraint information syntax structure (1500).

[0147] Additionally, in some examples, a gating flag (e.g., high_level_functionality_constraint_group_flag) (1502) equal to 1 may specify that a constraint flag related to a high-level functionality (e.g., reference picture resampling) within the constraint information group (1520) may be present as shown by FIG. 15B. Otherwise, a gating flag (e.g., high_level_functionality_constraint_group_flag) (1502) equal to 0 may specify that a constraint flag within the constraint information group (1520) may not be present within the general constraint information syntax structure (1500).

[0148] 15A, a gating flag (e.g., scalability_constraint_group_flag) (1503) equal to 1 may specify that constraint flags related to scalability (e.g., inter-layer prediction) may be present. Otherwise, constraint flags related to scalability may not be present in the general constraint information syntax structure (1500).

[0149] A gate flag (e.g., partitioning_constraint_group_flag) (1504) equal to 1 may specify that constraint flags related to higher-level partitions (e.g., subpictures or tiles) may be present. Otherwise, constraint flags related to higher-level partitions may not be present in the general constraint information syntax structure (1500).

[0150] A gate flag (e.g., intra_coding_tool_constraint_group_flag) (1505) equal to 1 may specify that constraint flags related to intra-coding (e.g., intra-prediction) may be present. Otherwise, constraint flags related to intra-coding may not be present in the general constraint information syntax structure (1500).

[0151] A gate flag (e.g., inter_coding_tool_constraint_group_flag) (1506) equal to 1 may specify that constraint flags related to inter-coding (e.g., motion compensation for inter-picture prediction) may be present. Otherwise, constraint flags related to inter-coding may not be present in the general constraint information syntax structure (1500).

[0152] A gate flag (e.g., transform_contraint_group_flag) (1507) equal to 1 may specify that constraint flags related to transform coding (e.g., multiple transform matrices) may be present. Otherwise, constraint flags related to transform coding may not be present in the general constraint information syntax structure (1500).

[0153] In one embodiment, when all gate flags (e.g., gate flags (1501)-(1508) in FIG. 15A) are equal to 0, no constraint flags are present in the general constraint information syntax structure (e.g., general constraint information syntax structure (1500)).

[0154] According to an aspect of the present disclosure, the syntax can be designed such that the control information, including gate flags (e.g., gate flags (1501)-(1508)), associated constraint flags (e.g., constraint flags (1511)-(1512) and constraint flags in the constraint information group (1520)), additional control information, etc., can be byte aligned, for example, the number of flags is divisible by 8 to maintain byte alignment. In one example, the number of gate flags and constraint flags in the constraint information (e.g., general constraint information syntax structure (1500)) is divisible by 8. A byte alignment mechanism can be used to achieve byte alignment of the control information. Referring to FIG. 15B, a syntax (e.g., a while loop) (1530) can be used for byte alignment.

[0155] In some embodiments, offset information, such as an offset (e.g., using the syntax element constraint_info_offset[]) and length information, such as a length (e.g., using the syntax element constraint_info_length[]), are present in the constraint information (e.g., at the beginning of the general constraint information syntax structure) to assist in presenting the constraint flags in the respective constraint information groups associated with the gating flags in the constraint information. In one embodiment, one or more of the at least one constraint information group are present in the coded video bitstream. In the case of a constraint information group, an offset and a length may be present in the constraint information for the constraint information group. The offset may indicate an offset relative to the first constraint flag in the constraint information group, and the length may indicate the number of constraint flags in the constraint information group. In some examples, the number of constraint information groups may be explicitly indicated, for example, by the syntax element num_constraint_info_set. The value of num_constaint_info_set may be an integer equal to or greater than 0. When the value of num_constaint_info_set is 0, constraint_info_offset[], constraint_info_length[], and constraint flags are not present in the general constraint information syntax structure.

[0156] In one embodiment, the constraint information offset (e.g., syntax element constraint_info_offset[i]) and the constraint information length (e.g., syntax element constraint_info_length[i]) can help to present the constraint flags for the constraint information group i (i is a positive integer) in the constraint information (e.g., general constraint information syntax structure). In one example, when the value of the constraint information offset (e.g., syntax element constraint_info_offset[i]) is equal to 5 and the value of the constraint information length (e.g., syntax element constraint_info_length[i]) is equal to 3, the fifth, sixth, and seventh constraint flags are associated with the constraint information group i and are present in the constraint information (e.g., general constraint information syntax structure).

[0157] In one example, run-length coding may be used to code the constraint flags specified in a predefined order (or a given sequence).

[0158] In one embodiment, run-length coding can be used when the constraint flags are specified in a predefined order (or a given sequence). Instead of directly coding the constraint flags, a suitably coded list of "skip" values ​​can indicate a constraint flag equal to 0, with subsequent constraint flags being implied to be equal to 1. The above-described run-coding can be particularly efficient when (i) the number of constraint flags is large and (ii) a small fraction of the constraint flags are equal to 1.

[0159] In one embodiment, one or more of the at least one constraint information group are present in the coded video bitstream. The constraint flags in the one or more of the at least one constraint information group are signaled according to a predetermined order. In response, the constraint flags can be run coded (e.g., run encoded or run decoded). Furthermore, prediction information for a subset of the coding blocks can be determined based on the constraint flags.

[0160] In one embodiment, at least one constraint flag in the constraint information group of the gate flag includes a plurality of constraint flags that are signaled according to a predetermined order. Accordingly, the plurality of constraint flags can be run-coded (e.g., run-encoded or run-decoded).

[0161] In one embodiment, the complete list of constraint flags may be specified in a video coding standard (e.g., the VVC specification), an external table, etc. In one example, only the available constraint flags of the constraint flags are indicated, for example, by one or more of the following: available constraint flags present in the coded video stream (e.g., num_available_constraint_flags), the number of gate flags (or constraint group present flags), constraint information offset information, and constraint information length information, etc.

[0162] In one example, a complete list of constraint flags is specified and available to the encoder and the decoder. The complete list of constraint flags can be stored in the decoder. The complete list of constraint flags can include 100 constraint flags. Ten of the 100 constraint flags are present in the constraint information for the CLVS and are therefore available to a subset of coding blocks in the CLVS. The ten of the 100 constraint flags are referred to as ten available constraint flags. In one example, the number of available constraint flags (e.g., ten) is signaled. In one example, the ten available constraint flags are in two constraint information groups and are gated by a first gate flag and a second gate flag. Thus, the first gate flag and the second gate flag can be signaled to indicate the ten available constraint flags.

[0163] In one example, a first constraint information offset (e.g., syntax element constraint_info_offset[0]) and a first constraint information length (e.g., syntax element constraint_info_length[0]) are signaled. A second constraint information offset (e.g., syntax element constraint_info_offset[1]) and a second constraint information length (e.g., syntax element constraint_info_length[1]) are signaled. For example, the syntax element constraint_info_offset[0] is 15, the syntax element constraint_info_length[0] is 3, the syntax element constraint_info_offset[1] is 82, and the syntax element constraint_info_length[1] is 7, thus indicating that the 15th to 17th constraint flags and the 82nd to 88th constraint flags in the complete list (e.g., 100 constraint flags) are available or present in the constraint information.

[0164] In one embodiment, any of the various techniques (or methods, embodiments, examples) for efficiently coding the constraint flags can be combined using appropriate control information. The combination can be any suitable combination of two or more of such techniques. Alternatively, one of the various techniques (or methods, embodiments, examples) can be used alone. The constraint flags can be grouped. Certain groups can use run coding, while other groups can use simple binary coding.

[0165] The value of the maximum number of constraint flags (eg, MaxNumConstraintFlags) can be predefined to be 16, 32, 64, 128, and so on.

[0166] Since the value of the maximum number of constraint flags (e.g., MaxNumConstraintFlags) can be determined by profile information such as general_profile_idc or general_sub_profile_idc, or codec version information, the range of the number of constraint flags (e.g., num_available_constraint_flags (1401)) can be limited by the profile information or version information. For example, the value of the number of constraint flags (e.g., num_available_constraint_flags (1401)) in the main profile (e.g., when MaxNumConstraintFlags=64) can be in the range of 0 to 64, while the value of the number of constraint flags (e.g., num_available_constraint_flags (1401)) in the advanced profile (e.g., when MaxNumConstraintFlags=128) can be in the range of 0 to 128.

[0167] In one embodiment, the value of the number of constraint flags (e.g., num_available_constraint_flags) can be inferred to be equal to a value predefined by profile information such as general_profile_idc or general_sub_profile_idc, or codec version information, so that the value of num_available_constraint_flags can be determined without explicit signaling.

[0168] In some embodiments, the reserved byte information may be present in a general constraint information syntax structure. For example, as shown in FIG. 13, the flags gci_num_reserved_bytes (1303) and gci_reserved_bytes[] (1304) may be present in a general constraint information syntax structure for an extension of the general constraint information syntax structure. The flag gci_num_reserved_bytes may specify the number of reserved constraint bytes. In one example, the reserved constraint bytes are for signaling additional flags (e.g., additional constraint flags). The flag gci_reserved_byte[] may have any suitable value.

[0169] In one embodiment, the value of gci_num_reserved_bytes may be limited or determined by profile information such as general_profile_idc or general_sub_profile_idc, or codec version information. In the Basic Profile (or Main Profile), the value of the flag gci_num_reserved_bytes may be 0. In the Extended Profile (or Advanced Profile), the value of gci_num_reserved_bytes may be greater than 0.

[0170] In some embodiments, a field sequence flag may be signaled in a coded video bitstream. The field sequence flag may indicate whether a picture in an output layer is coded with field coding. In some examples, the field sequence flag may be signaled in an SPS using the syntax element sps_field_seq_flag. In one embodiment, the flag sps_field_seq_flag may be present in an SPS. The flag sps_field_seq_flag equal to 1 may indicate that the CLVS conveys a picture representing a field. The flag sps_field_seq_flag equal to 0 may indicate that the CLVS conveys a picture representing a frame.

[0171] In the general constraint information syntax structure of FIG. 13, a flag general_frame_only_constraint_flag may be present. The flag general_frame_only_constraint_flag equal to 1 may specify that the scope for the output layer set (e.g., OlsInScope) conveys pictures that represent frames. The flag general_frame_only_constraint_flag equal to 0 specifies that the scope for the output layer set (e.g., OlsInScope) conveys pictures that may or may not represent frames. In one embodiment, the flag general_frame_only_constraint_flag indicates whether the pictures in the output layer set are coded with field coding. The output layer set may include a subset of coding blocks. The flag sps_field_seq_flag may be false based on the flag general_frame_only_constraint_flag indicating (e.g., is 1) that the subset of pictures is not coded with field coding. The subset of pictures may be in one layer of the output layer set.

[0172] When the flag general_frame_only_constraint_flag is equal to 1, the value of the flag sps_field_seq_flag may be equal to 0.

[0173] In one embodiment, the flag pps_mixed_nalu_types_in_pic_flag may be present in the PPS. The flag pps_mixed_nalu_types_in_pic_flag equal to 1 may specify that each picture that references the PPS has two or more VCL NAL units, and that the VCL NAL units do not have the same value of nal_unit_type. The flag pps_mixed_nalu_types_in_pic_flag equal to 0 may specify that each picture that references the PPS has one or more VCL NAL units, and that the VCL NAL units of each picture that references the PPS have the same value of nal_unit_type. The flag no_mixed_nalu_types_in_pic_constraint_flag may be present in the general constraint information syntax structure of FIG. 13. The flag no_mixed_nalu_types_in_pic_constraint_flag equal to 1 may specify that the value of pps_mixed_nalu_types_in_pic_flag must be equal to 0. The flag no_mixed_nalu_types_in_pic_constraint_flag equal to 0 does not impose such a constraint.

[0174] In one embodiment, a flag general_one_picture_only_constraint_flag may be present in a general constraint information syntax structure such as that shown in Figure 13. general_one_picture_only_constraint_flag equal to 1 may specify that there is only one picture coded in the bitstream. Flag general_one_picture_only_constraint_flag equal to 0 does not impose such a constraint.

[0175] In one embodiment, the flag single_layer_constraint_flag may be present in a general constraint information syntax structure such as that shown in Figure 13. The flag single_layer_constraint_flag equal to 1 may specify that sps_video_parameter_set_id must be equal to 0. The flag single_layer_constraint_flag equal to 0 does not impose such a constraint. When the flag general_one_picture_only_constraint_flag is equal to 1, the value of the flag single_layer_constraint_flag may be equal to 1.

[0176] In one embodiment, the flag all_layers_independent_constraint_flag may be present in a general constraint information syntax structure such as that shown in Figure 13. The flag all_layers_independent_constraint_flag equal to 1 may specify that the flag vps_all_independent_layers_flag may be equal to 1. The flag all_layers_independent_constraint_flag equal to 0 does not impose such a constraint. When the flag single_layer_constraint_flag is equal to 1, the value of the flag all_layers_independent_constraint_flag may be equal to 1.

[0177] In one embodiment, the flag no_res_change_in_clvs_constraint_flag may be present in a general constraint information syntax structure such as that shown in Figure 13. The flag no_res_change_in_clvs_constraint_flag equal to 1 may specify that the flag sps_res_change_in_clvs_allowed_flag may be equal to 0. The flag no_res_change_in_clvs_constraint_flag equal to 0 does not impose such a constraint. When the flag no_ref_pic_resampling_constraint_flag is equal to 1, the value of the flag no_res_change_in_clvs_constraint_flag may be equal to 1.

[0178] In one embodiment, the flag no_mixed_nalu_types_in_pic_constraint_flag may be present in the general constraint information syntax structure of Figure 13. The flag no_mixed_nalu_types_in_pic_constraint_flag equal to 1 specifies that the value of the flag pps_mixed_nalu_types_in_pic_flag may be equal to 0. The flag no_mixed_nalu_types_in_pic_constraint_flag equal to 0 does not impose such a constraint. When the flag one_subpic_per_pic_constraint_flag is equal to 1, the value of the flag no_mixed_nalu_types_in_pic_constraint_flag may be equal to 1.

[0179] In one embodiment, the flag no_trail_constraint_flag may be present in the general constraint information syntax structure of Figure 13. The flag no_trail_constraint_flag equal to 1 may specify that there may be no NAL units in OlsInScope with nuh_unit_type equal to TRAIL_NUT. The flag no_trail_constraint_flag equal to 0 does not impose such constraint. The flag no_trail_constraint_flag may be equal to 1 when the flag general_one_picture_only_constraint_flag is equal to 1.

[0180] In one embodiment, the flag no_stsa_constraint_flag may be present in the general constraint information syntax structure of Figure 13. The flag no_stsa_constraint_flag equal to 1 may specify that NAL units with nuh_unit_type equal to STSA_NUT may not be present in OlsInScope. The flag no_stsa_constraint_flag equal to 0 does not impose such constraint. The flag no_stsa_constraint_flag may be equal to 1 when the flag general_one_picture_only_constraint_flag is equal to 1.

[0181] In one embodiment, the flag no_trail_constraint_flag may be present in the general constraint information syntax structure of Figure 13. The flag no_trail_constraint_flag equal to 1 may specify that there may be no NAL units in OlsInScope with nuh_unit_type equal to TRAIL_NUT. The flag no_trail_constraint_flag equal to 0 does not impose such constraint. The flag no_trail_constraint_flag may be equal to 1 when the flag general_one_picture_only_constraint_flag is equal to 1.

[0182] In one embodiment, the flag no_stsa_constraint_flag may be present in the general constraint information syntax structure of Figure 13. The flag no_stsa_constraint_flag equal to 1 may specify that NAL units with nuh_unit_type equal to STSA_NUT may not be present in OlsInScope. The flag no_stsa_constraint_flag equal to 0 does not impose such constraint. The flag no_stsa_constraint_flag may be equal to 1 when the flag general_one_picture_only_constraint_flag is equal to 1.

[0183] In one embodiment, the flag no_idr_constraint_flag may be present in a general constraint information syntax structure such as that shown in Figure 13. no_idr_constraint_flag equal to 1 may specify that NAL units with nuh_unit_type equal to IDR_W_RADL or IDR_N_LP may not be present in OlsInScope. The flag no_idr_constraint_flag equal to 0 does not impose such constraint.

[0184] In one embodiment, a flag no_cra_constraint_flag may be present in a general constraint information syntax structure such as that shown in Figure 13. The flag no_cra_constraint_flag equal to 1 may specify that NAL units with nuh_unit_type equal to CRA_NUT may not be present in OlsInScope. The flag no_cra_constraint_flag equal to 0 does not impose such a constraint.

[0185] In one embodiment, the flag no_rasl_constraint_flag may be present in the general constraint information syntax structure of FIG. 13 (the flag no_rasl_constraint_flag is not shown). The flag no_rasl_constraint_flag equal to 1 may specify that no NAL units with nuh_unit_type equal to RASL_NUT are present in OlsInScope. The flag no_rasl_constraint_flag equal to 0 does not impose such constraint. When the flag no_cra_constraint_flag is equal to 1, the value of the flag no_rasl_constraint_flag may be equal to 1.

[0186] In one embodiment, the flag no_radl_constraint_flag may be present in a general constraint information syntax structure such as that shown in Figure 13. The flag no_radl_constraint_flag equal to 1 may specify that NAL units with nuh_unit_type equal to RADL_NUT may not be present in OlsInScope. The flag no_radl_constraint_flag equal to 0 does not impose such constraint. When the flag no_idr_constraint_flag is equal to 1 and the flag no_cra_constraint_flag is equal to 1, the value of the flag no_rasl_constraint_flag may be equal to 1.

[0187] Certain aspects of this disclosure provide techniques for constraining flag signaling for range extension with high bit depth.

[0188] According to one aspect of the present disclosure, some standards may be developed initially for specific applications with a specific chroma format and a specific bit depth (bits per sample). For example, HEVC is originally targeted at applications with a chroma format of 4:2:0 with 8-10 bits per sample. To create a standard that is applicable to other formats and bit depths other than the specific chroma format and the specific bit depth, range extensions are developed to support applications using other chroma formats and / or higher bit depths.

[0189] To restrict the feature set to those required for a particular group of applications, video coding standards define profiles, which may include a defined set of decoder features that should be supported for interoperability with encoders that use these features. For example, a profile may define a set of coding tools or algorithms that may be used in generating a compliant bitstream. In addition to profiles, some standards (e.g., VVC, HEVC, etc.) also define levels and tiers. Levels impose restrictions on the bitstream in terms of spatial resolution, pixel rate, bitrate values ​​and variances that may correspond to the decoder's processing load and memory capabilities. Level restrictions may be expressed in terms of maximum sample rate, maximum picture size, maximum bitrate, minimum compression ratio, coded picture buffer capabilities, etc. Higher level values ​​may correspond to higher complexity restrictions. Tiers modify bitrate values ​​and variance restrictions per level. For example, the Main tier targets most applications, while the High tier is designed to address more demanding video posting applications, such as having much higher bitrate values ​​than video distribution applications. Each of the profiles, tiers, and levels impacts implementation and decoding complexity, and the combination of the three specifies interoperability points for bitstreams and decoders.

[0190] In some examples, a decoder that conforms to a particular hierarchy and level must be able to decode all bitstreams that conform to the same hierarchy or sub-hierarchies at that level or any level below, and a decoder that conforms to a particular profile may support all features in that profile. In some examples, an encoder need not take advantage of any particular set of features supported in a profile, but must generate compliant bitstreams, i.e., bitstreams that obey specified constraints that allow them to be decoded by compliant decoders.

[0191] In addition to the PTL information, the PTL syntax structure may also contain a general constraint information (GCI) syntax structure, which contains a list of constraint flags and non-flag syntax elements that indicate specific constraint characteristics of the bitstream.

[0192] In one example, HEVC originally includes three profiles called the Main profile, the Main 10 profile, and the Main Still Picture profile. The three profiles have some limitations, such as only supporting 4:2:0 chroma sampling. The Main profile and the Main Still Picture profile only support 8 bits of video precision per sample, while the Main 10 profile supports up to 10 bits per sample. In the Main Still Picture profile, the entire bitstream contains only one coded picture.

[0193] In some examples, HEVC with range extension can support additional profiles. Some of the additional profiles can support higher bit depths and can be referred to as profiles for extended operating range with high bit depth. In some examples, the profiles for extended operating range with high bit depth include profiles that support more than 10 bits per sample, such as the Main 12 profile, the Main 12 4:4:4 profile, the Main 16 4:4:4 profile, the Main 12 Intra profile, the Main 12 4:4:4 Intra profile, the Main 16 4:4:4 Intra profile, the Main 12 Still Picture profile, the Main 12 4:4:4 Still Picture profile, and the Main 16 4:4:4 Still Picture profile.

[0194] Specifically, the Main 12 profile supports 4:0:0 and 4:2:0 chroma sampling, both intra and inter prediction modes, and allows for bit depths from 8 to 12 bits per sample. In some examples, a decoder conforming to the Main 12 profile is capable of decoding bitstreams produced with the following profiles: Monochrome, Monochrome 12, Main, Main 10, and Main 12.

[0195] The Main 12 4:4:4 profile supports chroma sampling of 4:0:0, 4:2:0, 4:2:2, and 4:4:4, as well as both intra and inter prediction modes, allowing for bit depths from 8 to 12 bits per sample. In some examples, a decoder conforming to the Main 12 4:4:4 profile is capable of decoding bitstreams produced with the following profiles: Monochrome, Main, Main 10, Main 12, Main 10 4:2:2, Main 12 4:2:2, Main 4:4:4, Main 10 4:4:4, Main 12 4:4:4, and Monochrome 12.

[0196] The Main 16 4:4:4 profile supports 4:0:0, 4:2:0, 4:2:2, and 4:4:4 chroma sampling, as well as both intra and inter prediction modes, allowing for bit depths from 8 to 16 bits per sample.

[0197] The Main 12 Intra profile supports 4:0:0 and 4:2:0 chroma sampling, as well as intra prediction modes, allowing bit depths from 8 to 12 bits per sample.

[0198] The Main 12 4:4:4 Intra profile supports 4:0:0, 4:2:0, 4:2:2, and 4:4:4 chroma sampling, as well as intra prediction modes, allowing bit depths from 8 to 12 bits per sample.

[0199] The Main 16 4:4:4 Intra profile supports 4:0:0, 4:2:0, 4:2:2, and 4:4:4 chroma sampling, as well as intra prediction modes, allowing bit depths from 8 to 16 bits per sample.

[0200] The Main 12 Still Picture profile supports 4:0:0 and 4:2:0 chroma sampling, allowing bit depths from 8 to 12 bits per sample. In the Main 12 Still Picture profile, the entire bitstream contains only one coded picture.

[0201] The Main 12 4:4:4 Still Picture profile supports chroma sampling of 4:0:0, 4:2:0, 4:2:2, and 4:4:4, allowing bit depths from 8 to 12 bits per sample. In the Main 12 4:4:4 Still Picture profile, the entire bitstream contains only one coded picture.

[0202] The Main 16 4:4:4 Still Picture profile supports chroma sampling of 4:0:0, 4:2:0, 4:2:2, and 4:4:4, allowing bit depths from 8 to 16 bits per sample. In the Main 16 4:4:4 Still Picture profile, the entire bitstream contains only one coded picture.

[0203] According to some aspects of the present disclosure, for a profile for extended operating range with high bit depth, some signaling (e.g., flags) in the bitstream may need to comply with certain high bit depth related constraints. When the signaling in the bitstream does not comply with the high bit depth related constraints, in one example, the video decoder may erroneously determine that the video decoder cannot decode the bitstream based on the signaling flags, which may limit the functionality of the video decoder.

[0204] In some embodiments, a bitstream conforming to the format of a profile for extended operating range with high bit depth may follow the constraint that a referenced VPS should have a syntax element denoted by vps_max_layers_minus1 equal to 0. In one example, the syntax element vps_max_layers_minus1 in a VPS may be used to signal the maximum number of layers allowed in each CVS that references the VPS. For example, the value of vps_max_layers_minus1 plus 1 is the maximum number of layers allowed in each CVS that references the VPS.

[0205] According to one aspect of the present disclosure, some profiles for extended operating range with high bit depth may not be scalable. In one example, when a bitstream conforms to the format of a profile for extended operating range with high bit depth, each CVS has only one layer. However, if the value of vps_max_layers_minus1 in the VPS that the CVS references is not equal to 0, the signaling of vps_max_layers_minusl may limit the ability of a video decoder to decode the bitstream. Therefore, in some examples, a bitstream adaptation process may be used to check whether the syntax vps_max_layers_minus1 is equal to 0 for a bitstream that conforms to the format of a profile for extended operating range with high bit depth.

[0206] In some embodiments, a bitstream conforming to the format of a profile for extended operating range with high bit depth may follow the constraint that a referenced SPS should have a syntax element denoted by sps_video_parameter_set_id equal to 0. In one example, the syntax element sps_video_parameter_set_id of an SPS is used to signal an identifier (ID) of a VPS to which the SPS refers. A VPS may contain layer relationships of multiple layers for a video sequence.

[0207] In one example, when a bitstream conforms to the format of the profile for extended operating range with high bit depth, each CVS has only one layer. In some examples, the VPS may be removed or may not be present. However, if the value of sps_video_parameter_set_id is not equal to 0, the signaling of sps_video_parameter_set_id may limit the ability of a video decoder to decode the bitstream. Thus, in some examples, a bitstream conformance process may be used to check whether the syntax element sps_video_parameter_set_id is equal to 0 for a bitstream conforming to the format of the profile for extended operating range with high bit depth.

[0208] In some embodiments, a bitstream conforming to the Format Range Extension Profile may follow the constraint that the referenced SPS should have ptl_multilayer_enabled_flag equal to 0. In one example, the syntax element ptl_multilayer_enabled_flag is in a syntax structure for profile, tier, and level information (e.g., syntax structure (1200), syntax structure (1410)) and is used to signal whether multi-layer extensions are enabled. For example, a syntax element ptl_multilayer_enabled_flag equal to 1 specifies that multi-layer extensions are enabled in the bitstream, and a syntax element ptl_multilayer_enabled_flag equal to 0 specifies that multi-layer extensions are not used in the bitstream.

[0209] In one example, when a bitstream conforms to the format of the profile for extended operating range with high bit depth, each CVS has only one layer. However, if the value of ptl_multilayer_enabled_flag is not equal to 0, the signaling of ptl_multilayer_enabled_flag may limit the ability of a video decoder to decode the bitstream. Thus, in some examples, a bitstream conformance process may be used to check whether the syntax element ptl_multilayer_enabled_flag is equal to 0 for a bitstream that conforms to the format of the profile for extended operating range with high bit depth.

[0210] According to some aspects of the present disclosure, constraints may be applied to other suitable syntax within a bitstream that conforms to the format of a profile for extended operating range with high bit depth.

[0211] According to one aspect of the present disclosure, a syntax element (e.g., denoted by sps_bitdepth_minus8) can be used to signal the bit depth (e.g., denoted by BitDepth) of the luma and chroma array samples, and the values ​​of the luma and chroma quantization parameter range offsets (e.g., denoted by QpBdOffset). In one example, the bit depth BitDepth can be calculated according to Equation (1), and the QP range offset QpBdOffset can be calculated according to Equation (2). BitDepth=8+sps_bitdepth_minus8 Formula (1) QpBdOffset=6×sps_bitdepth_minus8 Formula (2)

[0212] The syntax element sps_bitdepth_minus8 is signaled in the bitstream, and the value of sps_bitdepth_minus8 may need to comply with the constraints on the profile for the operating range extension with high bit depth. For example, the value of sps_bitdepth_minus8 may need to be in the range from 0 to 4, including for the Main 12 profile, the Main 12 4:4:4 profile, the Main 12 Intra profile, the Main 12 4:4:4 Intra profile, the Main 12 Still Picture profile, and the Main 12 4:4:4 Still Picture profile.

[0213] Note that in some examples, some other syntax elements may need to conform to the constraints on the profile for extended operating range with high bit depth. For example, the syntax elements called sps_chroma_format_idc and sps_palette_enabled_flag may need to conform to the constraints on the profile for extended operating range with high bit depth.

[0214] The syntax element sps_chroma_format_idc is used to indicate an index associated with a chroma format. For example, the syntax element sps_chroma_format_idc equal to 0 can indicate monochrome, the syntax element sps_chroma_format_idc equal to 1 can indicate chroma format 4:2:0, the syntax element sps_chroma_format_idc equal to 2 can indicate 4:2:2, and the syntax element sps_chroma_format_idc equal to 3 can indicate 4:4:4.

[0215] The syntax element sps_palette_enabled_flag equal to 1 specifies that the decoding process for palette mode may be used for intra blocks. The syntax element sps_palette_enabled_flag equal to 0 specifies that the decoding process for palette mode does not apply.

[0216] According to one aspect of the present disclosure, the bitstream may include additional flags when the bitstream conforms to a profile for extended operating range. The additional flags may comply with constraints on the profile for extended operating range with high bit depth.

[0217] 16 illustrates an example of a syntax structure (1600) for sequence parameter set (SPS) range extensions according to some embodiments of the present disclosure. The syntax structure (1600) includes syntax elements referenced by sps_extended_precision_flag (1601), sps_ts_residual_coding_rice_present_in_sh_flag (1603), sps_rrc_rice_extension_flag (1605), sps_persistent_rice_adaptation_enabled_flag (1607), and sps_reverse_last_sig_coeff_enabled_flag (1609).

[0218] The syntax element sps_extended_precision_flag (1601) equal to 1 specifies that an extended dynamic range is used for the binarization of transform coefficients in the scaling and transformation process, as well as some syntax elements such as abs_remainder[] and dec_abs_level[]. The syntax element abs_remainder[scan position n] is the absolute value of the remainder of the transform coefficient level coded with a Golomb-Rice code at scan position n. When abs_remainder[] is not present, it is inferred to be equal to 0. The syntax element dec_abs_level[scan position n] can correspond to an intermediate value coded with a Golomb-Rice code at scan position n and used to determine the level of the transform coefficient at scan position n. The syntax element sps_extended_precision_flag (1601) equal to 0 specifies that the extended dynamic range is not used in the scaling and transformation process, e.g., not used for binarization, such as the syntax elements abs_remainder[] and dec_abs_level[]. When not present, the syntax element sps_extended_precision_flag (1601) is inferred to be equal to 0.

[0219] In one example, the variable denoted by Log2TransformRange is used to determine the dynamic range for the binarization of a particular syntax element as well as the transform coefficients in the scaling and transform process. For example, the variable Log2TransformRange may be the number of bits to represent the transform coefficients in the scaling and transform process as well as the binarization of a particular syntax element. The dynamic range may be the difference between the maximum number and the minimum number represented using the number of bits. In one example, the variable Log2TransformRange is derived according to sps_extended_precision_flag, such as using Equation (3). Log2TransformRange=sps_extended_precision_flag?Max(15,Min(20,BitDepth+6)):15 Formula (3)

[0220] The dynamic range for the binarization of the transform coefficients and the specific syntax elements in the scaling and transform process can be determined based on the variable Log2TransformRange. In some examples, when the flag sps_extended_precision_flag has a value of 0, the extended dynamic range function (e.g., the coding tool of the extended dynamic range) is not used, and the dynamic range of the transform coefficients is based on a fixed number of bits, such as 15 bits. When the flag sps_extended_precision_flag has a value of 1, the extended dynamic range function is enabled, and the number of bits for representing the transform coefficients in the scaling and transform process can be one of 15 bits, 16 bits, 17 bits, 18 bits, 19 bits, and 20 bits based on the bit depth BitDepth in the example of Equation (1). The dynamic range of the transform coefficients can be determined based on the number of bits.

[0221] According to one aspect of the present disclosure, slice-based Rice parameter selection for transform skip residual coding may be included in the scope extension of the video standard. In some examples, as shown in Figure 16, when transform skip mode is enabled (e.g., syntax element sps_tranform_skip_enabled_flag is true), one control flag (e.g., represented by sps_ts_residual_coding_rice_present_in_sh_flag (1603)) is signaled in the sequence parameter set (SPS) to indicate whether signaling of Rice parameters for transform skip slices is enabled or disabled.

[0222] When the control flag (1603) is signaled as enabled (e.g., equal to "1"), one syntax element (e.g., denoted by sh_ts_residual_coding_rice_idx_minus1) is further signaled, for example, for each transform skip slice in the slice header, to indicate the Rice parameter selection for that transform skip slice. When the control flag is signaled as disabled (e.g., equal to "0"), no further syntax element is signaled at the slice level (e.g., slice header) to indicate the Rice parameter selection for the transform skip slice, and a default Rice parameter may be used for all transform skip slices in the coded video data that references the SPS, in one example.

[0223] For example, the syntax element sps_ts_residual_coding_rice_present_in_sh_flag (1603) equal to 1 specifies that the slice header flag (slice range) represented by sh_ts_residual_coding_rice_idx_minus1 may be present in the slice header (e.g., slice_header()) syntax structure that references the SPS. The syntax element sps_ts_residual_coding_rice_present_in_sh_flag (1603) equal to 0 specifies that the slice header flag sh_ts_residual_coding_rice_idx_minus1 is not present in the slice_header() syntax structure that references the SPS. When not present, in some examples, the value of sps_ts_residual_coding_rice_present_in_sh_flag is inferred to be equal to 0.

[0224] In some examples, the syntax element sps_rrc_rice_extension_flag (1605) is used to realize the control of one or more coding tools for Rice parameter derivation for binarization of some syntax elements such as abs_remainder[ ] and dec_abs_level[ ] in regular residual coding (RRC). In some examples, regular residual coding (RRC) refers to some techniques for coding blocks obtained by transform and quantization. In some examples, RRC can be modified for blocks obtained by quantization only. In some examples, transform skip residual coding (TSRC) refers to some techniques dedicated to coding blocks obtained by bypassing transform (also called transform skip).

[0225] In some examples, a video coding standard may include one or more coding tools for Rice parameter derivation for binarization of some syntax elements, such as abs_remainder[ ] and dec_abs_level[ ], and a scope extension of the video coding standard may include one or more alternative coding tools for Rice parameter derivation for binarization of some syntax elements, such as abs_remainder[ ] and dec_abs_level[ ].

[0226] In some examples, video standards use local template-based techniques for Rice parameter derivation. For example, a template including one or more (e.g., five in one example) adjacent coefficient levels is used for Rice parameter derivation. For example, the sum of absolute coefficient values ​​within the template can be calculated, and then the Rice parameter is determined based on the sum. In one example, a lookup table can be used to determine the Rice parameter based on the sum.

[0227] It should be noted that the Rice parameter may be determined by other suitable coding tools. In one example, a formula may be used to determine the Rice parameter based on a sum. In another example, context modeling may be used to determine the Rice parameter based on statistical data of adjacent coefficient levels. In some examples, a range extension of a video standard may specify one or more alternative coding tools for Rice parameter derivation.

[0228] In some examples, range extensions of the video standard may include modifications to the RRC for use in other scenarios. In one example, the range extensions may include different context modeling and residual signal rotation tools for residual coding in transform skip mode.

[0229] In some examples, the syntax element sps_rrc_rice_extension_flag (1605) equal to 1 specifies that an alternative Rice parameter derivation for binarization of abs_remaining[] and dec_abs_level[] is used (e.g., an alternative coding tool for Rice parameter derivation in range extension). The syntax element sps_rrc_rice_extension_flag (1605) equal to 0 specifies that an alternative Rice parameter derivation for binarization of abs_remaining[] and dec_abs_level[] is not used. When not present, the value of sps_rrc_rice_extension_flag (1605) is inferred to be equal to 0.

[0230] The syntax element sps_persistent_rice_adaptation_enabled_flag (1607) is used to realize the control of the statistical-based Rice parameter derivation for the binarization of abs_remainder[] and dec_abs_level[]. According to one aspect of the present disclosure, the Rice parameter derivation for the binarization of abs_remainder[] and dec_abs_level[] can be initialized at the beginning of each transform unit (TU) using the statistical data accumulated from the previous TU. In some examples, the statistical-based Rice parameter derivation can be included in the scope extension of the video standard.

[0231] The syntax element sps_persistent_rice_adaptation_enabled_flag (1607) equal to 1 in the SPS specifies that the Rice parameter derivation for binarization of abs_remaining[] and dec_abs_level[] is initialized at the beginning of each TU using accumulated statistical data from the previous TU. The syntax element sps_persistent_rice_adaptation_enabled_flag (1607) equal to 0 specifies that the previous TU state is not used in the Rice parameter derivation of the current TU. When not present, the value of sps_persistent_rice_adaptation_enabled_flag is inferred to be equal to 0.

[0232] In some embodiments, the syntax element sps_reverse_last_sig_coeff_enabled_flag (1609) is used to realize control of the coding tool used to code the location of the last significant coefficient during entropy coding of the transform coefficients (e.g., using a reverse diagonal scan pattern from the last significant coefficient). In one example, the location of the last significant coefficient can be coded by different coding tools. For example, a video standard can specify a first coding tool that can determine the location of the last significant coefficient by coding two coordinates of the location represented by the LastSignificantCoeffX and LastSignificantCoeffY variables, and a range extension of the video standard can specify an alternative coding tool, such as a second coding tool that can determine the location of the last significant coefficient by coding the relative coordinate of the last significant coefficient with reference to the bottom right corner of the zeroed-out transform block in one example.

[0233] In some examples, a syntax element sps_reverse_last_sig_coeff_enabled_flag (1609) equal to 1 in an SPS specifies that the slice header flag (slice range) represented by sh_reverse_last_sig_coeff_flag is present in the slice header syntax structure (e.g., slice_header() in some examples) that references the SPS. A syntax element sps_reverse_last_sig_coeff_enabled_flag (1609) equal to 0 specifies that the slice header flag sh_reverse_last_sig_coeff_flag is not present in the slice header syntax structure that references the SPS. If not present, the value of sps_reverse_last_sig_coeff_enabled_flag (1609) is inferred to be equal to 0.

[0234] In some examples, the value of the slice header flag sh_reverse_last_sig_coeff_flag of the slice is used to determine the position derivation of the last significant coefficient among the transform coefficients in the scaling and transform process in the coding of the slice. In one example, when sh_reverse_last_sig_coeff_flag is equal to 1, the last significant coefficient position is coded by an alternative coding tool in the range extension of the video standard, such as a second coding tool, otherwise the current coordinate of the last significant coefficient position is coded by the first coding tool.

[0235] 17 shows an example of a table (1700) that contains allowable values ​​for some syntax elements in a profile for an extended operating range with high bit depth. The table (1700) can be used as constraints on the syntax elements in the table (1700).

[0236] Note that constraints specified in table (1700) may apply, where an item marked with "-" indicates that the table item does not impose any profile-specific constraints on the corresponding syntax element. For some syntax elements that have a table item marked with "-", the constraints may be indirectly imposed by semantic constraints imposed elsewhere, e.g., in an appropriate specification in a standards document when other specified constraints are met.

[0237] Additionally, in some instances, within a bitstream conforming to the Main 12 Still Picture, Main 12 4:4:4 Still Picture, or Main 16 4:4:4 Still Picture profiles, the bitstream should contain only one picture.

[0238] In some examples, for bitstreams conforming to the Main 12, Main 12 4:4:4, Main 16 4:4:4, Main 12 Intra, Main 12 4:4:4 Intra, or Main 16 4:4:4 Intra profiles, the syntax element indicating the level of the bitstream should not indicate the highest level because in some examples there is only one layer, such as the base layer in the bitstream, which cannot have the highest level. In one example, a syntax element in the general constraint information (e.g., syntax structure (1300), syntax structure (1420)), such as that represented by general_level_idc, is used to indicate an identifier for the level of the bitstream. In some examples, the level is represented by two numbers, a major number (represented by majorNum) and a minor number (represented by minorNum). The identifier for the level can be calculated based on the major number and the minor number. In one example, the identifier for the level is in the range of [0,255] and is calculated according to equation (4). general_level_idc=majorNum×16+minorNum×3 Equation (4) Then, in one example, the highest level is 15.5 and the identifier for the highest level is 255.

[0239] In some examples, signaling a higher level than necessary may limit the ability of a video decoder to decode the bitstream. Thus, in some examples, the bitstream adaptation process may check a syntax element for indicating a level in the PTL information to determine whether a constraint on the level is satisfied.

[0240] FIG. 18 shows a flowchart outlining a process (1800) according to one embodiment of the disclosure. The process (1800) may be performed by any suitable device, such as the electronic device (420), the electronic device (430), the server device (405), and / or another device. In some examples, some or all of the operations of the process (1800) may be performed by the electronic device (420). In some examples, some or all of the operations of the process (1800) may be performed by the electronic device (430). In some examples, some or all of the operations of the process (1800) may be performed by the server device (405). In some examples, some of the operations of the process (1800) may be performed by the electronic device (420) and some of the operations of the process (1800) may be performed by the electronic device (430).

[0241] At (S1810), a bitstream having a profile for an extended operating range with high bit depth is acquired by the device. In one example, the electronic device (420) can acquire the bitstream by encoding video data. In another example, the electronic device (430) can receive the bitstream from a network, the bitstream carrying the encoded video data. In another example, the server device (405) receives the bitstream from a capture subsystem (413), the bitstream carrying the encoded video data. In some examples, the bitstream can be stored in and read from a computer-readable medium.

[0242] At (S1820), a bitstream adaptation process is performed by the device. In some examples, the device may perform a bitstream adaptation process that determines whether a bitstream including an encoded representation of the video data conforms to various constraints, such as those defined in a video coding standard. As part of the bitstream adaptation process, the device may determine whether the bitstream conforms to constraints associated with a profile for extended operating range with high bit depth, such as those indicated by (S1822) and (S1825).

[0243] At (S1822), the device determines that the profile information of the bitstream indicates a profile for an extended operating range with a high bit depth (e.g., higher than 8 bit depth). In some examples, the profile is one of a Main 12 profile, a Main 12 4:4:4 profile, a Main 16 4:4:4 profile, a Main 12 Intra profile, a Main 12 4:4:4 Intra profile, a Main 16 4:4:4 Intra profile, a Main 12 Still Picture profile, a Main 12 4:4:4 Still Picture profile, a Main 16 4:4:4 Still Picture profile, etc.

[0244] At (S1825), the device checks at least the syntax elements of the bitstream to determine whether the syntax elements of the bitstream satisfy a constraint indicating a single layer for output at a decoder for decoding the bitstream.

[0245] In some embodiments, the device checks a first syntax element indicating a maximum number of layers in a referenced video parameter set (VPS) to determine whether the value of the first syntax element satisfies a constraint. In one example, the device checks a first syntax element equal to the maximum number of layers in the VPS minus 1 (e.g., vps_max_layers_minus1) to determine whether the value of the first syntax element is equal to 0.

[0246] In some embodiments, the device checks a second syntax element of a sequence parameter set (SPS) that is an identifier for a video parameter set (VPS) to which the SPS refers to determine whether the value of the second syntax element satisfies a constraint. In one example, the device checks a second syntax element of the SPS (e.g., sps_video_parameter_set_id) to determine whether the value of the second syntax element is equal to 0.

[0247] In some embodiments, the device checks a third syntax element indicating enabling / disabling of multi-layer extensions in the bitstream to determine whether the value of the third syntax element satisfies the constraint. In one example, the device checks a third syntax element (e.g., ptl_multilayer_enabled_flag) to determine whether the value of the third syntax element indicates disabling of multi-layer extensions.

[0248] In some embodiments, the device also checks some syntax elements, such as those illustrated by the table (1700) of FIG. 17, to determine whether the syntax element satisfies the constraints associated with the profile. In one example, the device checks a syntax element indicating a bit depth (e.g., sps_bitdepth_minus8) to determine whether the value of the syntax element satisfies the constraints associated with the profile. In another example, the device checks a syntax element indicating an index associated with a chroma format (e.g., sps_chroma_format_idc) to determine whether the value of the syntax element satisfies the constraints associated with the profile. In another example, the device checks a syntax element indicating palette mode enable / disable (e.g., sps_palette_enabled_flag) to determine whether the value of the syntax element satisfies the constraints associated with the profile. In another example, the device checks a syntax element indicating extended dynamic range use / non-use (e.g., sps_extended_precision_flag) to determine whether the value of the syntax element satisfies the constraints associated with the profile. In another example, the device checks a syntax element indicating the presence / absence of a transform skip flag in the residual coding syntax (e.g., sps_ts_residual_coding_rice_present_in_sh_flag) to determine whether the value of the syntax element satisfies the constraints associated with the profile. In another example, the device checks a syntax element indicating the use / non-use of Rice coding in regular residual coding (e.g., sps_rrc_rice_extension_flag) to determine whether the value of the syntax element satisfies the constraints associated with the profile.In another example, the device checks a syntax element indicating enable / disable of persistent Rice parameter adaptation (e.g., sps_persistent_rice_adaption_enabled_flag) to determine whether the value of the syntax element satisfies the constraint associated with the profile. In another example, the device checks a syntax element indicating a scanning pattern from the last significant coefficient (e.g., sps_reverse_last_sig_coeff_enabled_flag) to determine whether the value of the syntax element satisfies the constraint associated with the profile.

[0249] Additional conformance checks may be performed. In one example, in response to the profile being a still image profile, the device checks whether the bitstream includes only one picture. In another example, in response to the profile being one of the Main 12, Main 12 4:4:4, Main 16 4:4:4, Main 12 Intra, Main 12 4:4:4 Intra, or Main 16 4:4:4 Intra profiles, the device checks a syntax element indicating a level of the bitstream to determine whether the level satisfies a constraint. In one example, the device checks whether a value of a syntax element (e.g., general_level_idc) is not equal to 255.

[0250] At (S1830), the device determines whether the bitstream conformance process determines that the bitstream conforms to the constraints. In response to determining that the bitstream conforms to the constraints, the process (1800) proceeds to (S1840); otherwise, the process (1800) proceeds to (S1850).

[0251] At (S1840), the device can provide the bitstream to a video decoder. In one example, the bitstream is provided to the video decoder (410). In another example, the device can output the bitstream to a computer-readable medium for subsequent transmission to a destination electronic device.

[0252] At (S1850), the device can reject the bitstream and can generate an error message.

[0253] The process (1800) may be adapted as appropriate. Steps within the process (1800) may be modified and / or omitted. Additional steps may be added. Any suitable order of performance may be used.

[0254] The techniques described above (e.g., techniques for signaling constraint flags, adaptive resolution parameters, etc.) can be implemented as computer software using computer readable instructions and physically stored on one or more computer readable media. For example, Figure 19 illustrates a computer system (1900) suitable for implementing certain embodiments of the disclosed subject matter.

[0255] The computer software may be coded using any suitable machine or computer language that can be assembled, compiled, linked, or similar mechanisms to produce code including instructions that can be executed by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc., directly, or via interpretation, microcode execution, etc.

[0256] The instructions may be executed on various types of computers or components thereof including, for example, personal computers, tablet computers, servers, smart phones, gaming devices, Internet of Things devices, and the like.

[0257] 19 with respect to the computer system (1900) 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 the embodiments of the present disclosure. The arrangement of components should not be interpreted as having any dependency or requirement regarding any one or combination of components illustrated in the exemplary embodiment of the computer system (1900).

[0258] The computer system (1900) may include certain human interface input devices. Such human interface input devices may respond to input by one or more human users, for example, via tactile input (such as keystrokes, swipes, data glove movements), audio input (such as voice, clapping), visual input (such as gestures), or olfactory input (not depicted). Human interface devices may also be used to capture certain media not necessarily directly associated with conscious human input, such as audio (such as voice, music, ambient sounds), images (such as scanned images, photographic images obtained from a still camera), and video (such as two-dimensional video, three-dimensional video including stereoscopic video).

[0259] The input human interface devices may include one or more of a keyboard (1901), a mouse (1902), a trackpad (1903), a touch screen (1910), a data glove (not shown), a joystick (1905), a microphone (1906), a scanner (1907), and a camera (1908) (only one of each is depicted).

[0260] The computer system (1900) 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, via haptic output, sound, light, and smell / taste. Such human interface output devices may include haptic output devices (e.g., haptic feedback via a touch screen (1910), data gloves (not shown), or joystick (1905), although there may be haptic feedback devices that do not function as input devices), audio output devices (such as speakers (1909), headphones (not depicted)), visual output devices (such as screens (1910), including CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch screen input capability, each with or without haptic feedback capability, some of which may be capable of outputting two-dimensional visual output or three or more dimensional output via means such as stereographic output, virtual reality glasses (not depicted), holographic displays, and smoke tanks (not depicted)), and printers (not depicted).

[0261] The computer system (1900) may also include human accessible storage devices and their associated media, such as optical media, including CD / DVD ROM / RW (1920) with CD / DVD or similar media (1921), thumb drives (1922), removable hard drives or solid state drives (1923), legacy magnetic media such as tapes and floppy disks (not depicted), and specialized ROM / ASIC / PLD based devices (not depicted) such as security dongles.

[0262] Those skilled in the art should also understand that the term "computer-readable medium" as used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transitory signals.

[0263] The computer system (1900) may also include an interface (1954) to one or more communication networks (1955). The network may be, for example, wireless, wired, optical. The network 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, wireless LAN, cellular networks including GSM, 3G, 4G, 5G, LTE, etc., TV wired or wireless wide area digital networks including cable TV, satellite TV, and terrestrial broadcast TV, vehicular and industrial including CANBus, etc. Certain networks typically require an external network interface adapter attached to a particular general-purpose data port (e.g., a USB port of the computer system (1900)) or peripheral bus (1949), while other networks are typically integrated into the core of the computer system (1900) by attachment to a system bus described below (e.g., an Ethernet interface to a PC computer system or a cellular network interface to a smartphone computer system). Using any of these networks, the computer system (1900) can communicate with other entities. Such communications may be one-way receive only (e.g., broadcast TV), one-way transmit only (e.g., CANbus to a specific CANbus device), or bidirectional, for example, with other computer systems using local or wide area digital networks. Specific protocols and protocol stacks may be used with each of these networks and network interfaces described above.

[0264] The aforementioned human interface devices, human accessible storage devices, and network interfaces may be attached to a core (1940) of the computer system (1900).

[0265] The cores (1940) may include specialized programmable processing devices in the form of one or more central processing units (CPUs) (1941), graphics processing units (GPUs) (1942), field programmable gate areas (FPGAs) (1943), hardware accelerators for specific tasks (1944), graphics adapters (1950), and the like. These devices may be connected via a system bus (1948), along with read only memory (ROM) (1945), random access memory (1946), and internal mass storage (1947), such as an internal hard drive or SSD that is not user accessible. In some computer systems, the system bus (1948) may be accessible in the form of one or more physical plugs to allow expansion with additional CPUs, GPUs, and the like. Peripherals may be attached directly to the core's system bus (1948) or via a peripheral bus (1949). In one example, a screen (1910) may be connected to a graphics adapter (1950). Architectures for peripheral buses include PCI, USB, etc.

[0266] The CPU (1941), GPU (1942), FPGA (1943), and accelerator (1944) may combine to execute certain instructions that may constitute the aforementioned computer code. That computer code may be stored in ROM (1945) or RAM (1946). Persistent data may be stored, for example, in internal mass storage (1947), while transitory data may also be stored in RAM (1946). Rapid storage and retrieval from any of the memory devices may be enabled using cache memories that may be closely associated with one or more of the CPU (1941), GPU (1942), mass storage (1947), ROM (1945), RAM (1946), etc.

[0267] The computer-readable medium can have computer code thereon for performing various computer-implemented operations. The medium and computer code can be those specially designed and constructed for the purposes of the present disclosure, or they can be of the kind well known and available to those skilled in the computer software arts.

[0268] By way of example and not by way of limitation, a computer system (1900) having an architecture, and in particular a core (1940), can provide functionality as a result of a processor (including a CPU, GPU, FPGA, accelerator, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media can be the user-accessible mass storage introduced above, as well as media associated with a particular storage of the core (1940) of a non-transitory nature, such as the core internal mass storage (1947) or ROM (1945). Software implementing various embodiments of the present disclosure can be stored in such devices and executed by the core (1940). The computer-readable media can include one or more memory devices or chips, depending on particular needs. The software can cause the core (1940), and in particular the processors therein (including a CPU, GPU, FPGA, etc.) to perform certain processes or certain portions of certain processes described herein, including defining data structures stored in RAM (1946) and modifying such data structures according to processes defined by the software. Additionally, or alternatively, a computer system may provide functionality as a result of logic hardwired or otherwise embodied in circuitry (e.g., an accelerator (1944)) that may operate in place of or together with software to perform certain processes or certain portions of certain processes described herein. Where appropriate, references to software may encompass logic, and vice versa. Where appropriate, references to computer-readable media may encompass 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 suitable combination of hardware and software. Appendix A: Acronyms JEM: Joint Exploration Model VVC: Versatile Video Coding BMS: Benchmark Set MV: Motion Vector HEVC: High Efficiency Video Coding SEI: Supplemental Extended Information VUI: Video Usability Information GOP: Group of Pictures TU: conversion unit PU: Prediction unit CTU: Coding Tree Unit CTB: coding tree block PB: Predicted block HRD: Hypothetical Reference Decoder SNR: Signal to Noise Ratio CPU: Central Processing Unit GPU: Graphics Processing Unit CRT: cathode ray tube LCD: Liquid crystal display OLED: Organic Light Emitting Diode CD:Compact Disc DVD: Digital Video Disc ROM: Read-Only Memory RAM: Random Access Memory ASIC: Application Specific Integrated Circuit PLD: Programmable Logic Device LAN: Local Area Network GSM: Global System for Mobile Communications LTE: Long Term Evolution CANBus: Controller Area Network Bus USB: Universal Serial Bus PCI: Peripheral Component Interconnect FPGA: Field Programmable Gate Area SSD: Solid State Drive IC: Integrated Circuit CU: coding unit

[0269] While this disclosure describes several exemplary embodiments, there are alterations, permutations, and various alternative equivalents that fall within the scope of this disclosure. It will thus be appreciated that those skilled in the art will be able to 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]

[0270] 101 Samples 102 Arrow 103 Arrow 104 Square Block 180 Schematic diagram 201 Current Block 202 Ambient Samples 203 Ambient Samples 204 Ambient Samples 205 Ambient Samples 206 Ambient Samples 300 Communication Systems 310 Terminal Devices 320 Terminal Devices 330 Terminal Devices 340 Terminal Devices 350 Communication Network 400 Communication Systems 401 Video Source 402 Video Picture Stream 403 Video Encoder 404 Encoded Video Bitstream, Encoded Video Data 405 Streaming Server, Server Device 406 Client Subsystem 407 Copy video data 408 Client Subsystem 409 Input copy of encoded video data 410 Video Decoder 411 Video Picture Output Stream 412 Display 413 Capture Subsystem 420 Electronic Devices 430 Electronic Devices 501 Channel 510 Video Decoder 512 Rendering Device 515 Buffer Memory 520 Parser 521 Symbols 530 Electronic Devices 531 Receiver 551 Scaler / Descaler Unit 552 Intra-picture prediction unit 553 Motion Compensation Prediction Unit 555 Aggregator 556 Loop Filter Unit 557 Reference Picture Memory 558 Current Picture Buffer 601 Video Sources 603 Video Coder, Video Encoder 620 Electronic Devices 630 Source Coder 632 Coding Engine 633 Local Decoder 634 Reference Picture Memory 635 Predictor 640 Transmitter 643 coded video sequence 645 Entropy Coder 650 Controller 660 Communication Channels 703 Video Encoder 721 General-purpose controller 722 Intra Encoder 723 Residual Calculator 724 Residual Encoder 725 Entropy Encoder 726 Switch 728 Residual Decoder 730 InterEncoder 810 Video Decoder 871 Entropy Decoder 872 Intra Decoder 873 Residual Decoder 874 Recovery Module 880 Interdecoder 911 Picture Header 912 ARC information 913 H.263 PLUS PTYPE 924 PPS 925 ARC Reference Information 926 Target Resolution Table 927 SPS 938 Tile Group Header 939 ARC information 941 APS, parameter set 942 ARC information 953 ARC Reference Information 954 Tile Group Header 955 ARC information 956 SPS, parameter set 1000 Tables 1101 Tile Group Header 1102 Syntax element dec_pic_size_idx 1103 Flags (e.g., adaptive_pic_resolution_change_flag) 1110 SPS 1111 Flags, first syntax element 1112 if() statement 1113 Output Resolution 1114 Syntax elements (e.g., reference_pic_size_present_flag) 1115 Reference Picture Dimensions 1116 Table directive (e.g. syntax element num_dec_pic_size_in_luma_samples_minus1) 1117 Syntax Elements 1200 Syntax Structure Example 1300 Syntax Structure Example 1301 Constraint flag (e.g., no_lossless_coding_tool_constraint_flag) 1302 constraint flag (e.g., no_lossy_coding_tool_constraint_flag) 1303 gci_num_reserved_bytes 1304 gci_reserved_bytes[] 1305 Constraint flag (e.g., intra_only_constraint_flag) 1306 Constraint flag (e.g., no_alf_constraint_flag) 1401 Number of constraint flags (e.g., num_available_constraint_flags) 1410 Syntax Structure Example 1420 Syntax structure, Syntax examples 1500 General Constraint Information Syntax Structure 1501 Gate flag (e.g. general_frame_structure_constraint_group_flag) 1502 Gate flags (e.g., high_level_functionality_constraint_group_flag) 1503 Gate flags (e.g., scalability_constraint_group_flag) 1504 Gate flag (e.g., partitioning_constraint_group_flag) 1505 Gate flag (e.g., intra_coding_tool_constraint_group_flag) 1506 Gate flag (e.g., inter_coding_tool_constraint_group_flag) 1507 Gate flags (e.g., transform_contraint_group_flag) 1508 Gate flag (e.g., inloop_filtering_constraint_group_flag) 1510 Constraint Information Group 1511 Constraint flag, general_non_packed_constraint_flag 1512 Constraint flag, general_frame_only_constraint_flag 1513 Constraint flag, general_non_projected_constraint_flag 1514 Constraint flag, general_one_picture_only_constraint_flag 1520 Constraint Information Group 1530 Syntax (e.g. while loop) 1600 Syntax structure of sequence parameter set (SPS) range extension 1601 sps_extended_precision_flag 1603 sps_ts_residual_coding_rice_present_in_sh_flag 1605 sps_rrc_rice_extension_flag 1607 sps_persistent_rice_adaptation_enabled_flag 1609 sps_reverse_last_sig_coeff_enabled_flag 1700 Table 1800 Processes 1900 Computer Systems 1901 Keyboard 1902 Mouse 1903 Trackpad 1905 Joystick 1906 Microphone 1907 Scanner 1908 Camera 1909 Speaker 1910 Touch Screen 1920 CD / DVD ROM / RW 1921 CD / DVD or similar media 1922 Thumb Drive 1923 Removable Hard Drive or Solid State Drive 1940 Core 1941 Central Processing Unit (CPU) 1942 Graphics Processing Unit (GPU) 1943 Field Programmable Gate Area (FPGA) 1944 Hardware Accelerator 1945 Read-Only Memory (ROM) 1946 Random Access Memory, RAM 1947 Core Internal Mass Storage 1948 System Bus 1949 Peripheral Bus 1950 Graphics Adapter 1954 Interface 1955 Communication Network

Claims

1. 1. A method of video data processing performed by one or more processors, comprising: determining that profile information of the bitstream indicates a profile for an extended operating range with a bit depth higher than a predetermined value; checking at least a syntax element of the bitstream to determine whether the syntax element satisfies a constraint indicating a single layer for output at a decoder for decoding the bitstream, and checking to determine whether a second syntax element of a sequence parameter set (SPS), which is an identifier for a video parameter set (VPS) to which the SPS refers, is equal to 0 to determine whether the value of the second syntax element satisfies the constraint, wherein the value of the second syntax element is 0 when a general constraint information syntax indicates that there is only one picture coded in the bitstream.

2. The step of checking at least the syntax elements further comprises:

2. The method of claim 1, further comprising: checking a first syntax element indicating a maximum number of layers in the referenced VPS to determine whether a value of the first syntax element satisfies the constraint.

3. said step of checking the first syntax element further comprising:

3. The method of claim 2, comprising: checking a first syntax element equal to the maximum number of layers in the VPS minus 1 to determine whether the value of the first syntax element is equal to 0, the first syntax element being denoted by vps_max_layers_minus1.

4. The step of checking at least the syntax elements further comprises:

2. The method of claim 1, further comprising: checking a third syntax element indicating enabling / disabling of multi-layer enhancements in the bitstream to determine whether a value of the third syntax element satisfies the constraint.

5. said step of checking the third syntax element further comprising:

5. The method of claim 4, comprising checking the third syntax element to determine whether the value of the third syntax element indicates disabling of the multi-layer extensions.

6. checking at least one of a syntax element indicating a bit depth, a syntax element indicating an index associated with a chroma format, a syntax element indicating enabling / disabling of palette mode, a syntax element indicating use / non-use of extended dynamic range, a syntax element indicating the presence / absence of a transform skip flag in the residual coding syntax, a syntax element indicating use / non-use of Rice coding in regular residual coding, a syntax element indicating enabling / disabling of persistent Rice parameter adaptation, and a syntax element indicating a scan pattern from the last significant coefficient to determine whether a constraint associated with the profile is satisfied. The method of claim 1, further comprising:

7. in response to the profile being a still image profile, checking whether the bitstream contains only one picture. The method of claim 1, further comprising:

8. checking a syntax element indicating a level of the bitstream to determine whether the level satisfies the constraint. The method of claim 1, further comprising:

9. An apparatus comprising processing circuitry configured to carry out the method of any one of claims 1 to 8.

10. A computer program product for causing one or more processors to carry out the method according to any one of claims 1 to 8.

Images