Method, device and computer program for decoding an encoded video bitstream

Abstract

To provide a method and a device for decoding a video bit stream.SOLUTION: The method includes obtaining, from an encoded video bitstream, a first flag indicating that reference picture resampling is enabled for a coded video sequence (CVS), determining a value of a second flag indicating whether a picture resolution is changed in the CVS, decoding the CVS with reference picture resampling for spatial scalability and adaptive resolution change (ARC) based on the value of the second flag indicating that the picture resolution is changed in the CVS, and decoding the CVS with reference picture resampling for spatial scalability and without reference picture resampling for ARC based on the value of the second flag indicating that the picture resolution is not changed in the CVS.SELECTED DRAWING: Figure 25A

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority under 35 U.S.C. § 119 in the United States Patent and Trademark Office to U.S. Provisional Patent Application No. 63 / 027835, filed May 20, 2020, U.S. Provisional Patent Application No. 63 / 035647, filed June 5, 2020, U.S. Provisional Patent Application No. 63 / 036174, filed June 8, 2020, U.S. Provisional Patent Application No. 63 / 036342, filed June 8, 2020, and U.S. Patent Application No. 17 / 211236, filed March 24, 2021. The disclosures of these prior applications are incorporated herein by reference in their entirety.

[0002] [Technical field] The disclosed subject matter relates to video coding and decoding, and more particularly to signaling combination of reference picture resampling and spatial scalability in multi-layer coded video streams. [Background technology]

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

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

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

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

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

[0008] In an embodiment, a method of decoding an encoded video bitstream using at least one processor comprises: obtaining a first flag from the encoded video bitstream indicating that reference picture resampling is enabled for a coded video sequence (CVS); determining a value of a second flag indicating whether picture resolution is changed in said CVS; decoding the CVS using the reference picture resampling for spatial scalability and Adaptive Resolution Change (ARC) based on the value of the second flag indicating that the picture resolution is changed in the CVS; decoding the CVS with the reference picture resampling for the spatial scalability and without the reference picture resampling for the ARC based on a value of the second flag indicating that the picture resolution is not changed in the CVS; A method is provided comprising:

[0009] In an embodiment, a device for decoding an encoded video bitstream comprises: at least one memory configured to store program code; at least one processor configured to read the program code and to act as directed by the program code; and The program code first obtaining code that causes the at least one processor to obtain, from the encoded video bitstream, a first flag that indicates that reference picture resampling is enabled for a coded video sequence (CVS); decision code that causes the at least one processor to determine a value of a second flag that indicates whether picture resolution is changed in the CVS; first decoding code that causes the at least one processor to decode the CVS using the reference picture resampling for spatial scalability and adaptive resolution change (ARC) based on a value of the second flag indicating that the picture resolution is changed in the CVS; second decoding code that causes the at least one processor to decode the CVS using the reference picture resampling for the spatial scalability and without the reference picture resampling for the ARC based on a value of the second flag indicating that the picture resolution is not changed in the CVS; Including, A device is provided.

[0010] In an embodiment, a non-transitory computer-readable medium storing instructions includes: The instruction: When executed by one or more processors of a device that decodes an encoded video bitstream, the one or more processors are obtaining a first flag from the encoded video bitstream indicating that reference picture resampling is enabled for a coded video sequence (CVS); determining a value of a second flag indicating whether picture resolution is changed in said CVS; decoding the CVS using the reference picture resampling for spatial scalability and adaptive resolution change (ARC) based on a value of the second flag indicating that the picture resolution is changed in the CVS; decoding the CVS with the reference picture resampling for the spatial scalability and without the reference picture resampling for the ARC based on a value of the second flag indicating that the picture resolution is not changed in the CVS; having one or more instructions for executing A non-transitory computer-readable medium is provided.

[0011] Further features, nature and various advantages of the disclosed subject matter will become more apparent from the following detailed description and accompanying drawings. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of a simplified block diagram of a communication system according to an embodiment. [Figure 2] 1 is a schematic diagram of a simplified block diagram of a communication system according to an embodiment. [Figure 3] FIG. 2 is a schematic block diagram of a decoder according to an embodiment. [Figure 4] FIG. 2 is a schematic block diagram of an encoder according to an embodiment. [Figure 5A] 10 is a schematic diagram of options for signaling ARC parameters according to an embodiment. [Figure 5B] 10 is a schematic diagram of options for signaling ARC parameters according to an embodiment. [Figure 5C] 10 is a schematic diagram of options for signaling ARC parameters according to an embodiment. [Figure 5D] 10 is a schematic diagram of options for signaling ARC parameters according to an embodiment. [Figure 5E] 10 is a schematic diagram of options for signaling ARC parameters according to an embodiment. [Figure 6A] 3 is a schematic diagram of an example of a syntax table according to an embodiment. [Figure 6B] 3 is a schematic diagram of an example of a syntax table according to an embodiment. [Figure 7] 1 is an example of a prediction structure for scalability through adaptive resolution change, according to an embodiment. [Figure 8] 1 is an example of a syntax table according to an embodiment. [Figure 9] FIG. 10 is a schematic diagram of a simplified block diagram of a POC cycle per access unit and parsing and decoding of an access unit count value according to an embodiment. [Figure 10] 1 is a schematic diagram of a video bitstream structure including multi-layer sub-pictures according to an embodiment. [Figure 11] 1 is a schematic diagram of a display of a selected sub-picture with enhanced resolution according to an embodiment. [Figure 12] FIG. 2 is a block diagram of a decoding and display process for a video bitstream containing multi-layer sub-pictures, according to an embodiment. [Figure 13] 1 is a schematic diagram of a 360-degree video display with a sub-picture enhancement layer according to an embodiment; [Figure 14] 1 is an example of layout information for a sub-picture and its corresponding layer and picture prediction structure according to an embodiment. [Figure 15] 1 is an example of layout information of a sub-picture and its corresponding layer and picture prediction structure with local region spatial scalability modality according to an embodiment. [Figure 16A]10 is an example of a syntax table for sub-picture layer information, according to an embodiment. [Figure 16B] 10 is an example of a syntax table for sub-picture layer information, according to an embodiment. [Figure 17] 10 is an example of a syntax table of an SEI message for sub-picture layout information according to an embodiment. [Figure 18] 10 is an example syntax table showing output layers and profile / tier / level information for each output layer set, according to an embodiment. [Figure 19] 10 is an example syntax table showing output layer mode on for each output layer set, according to an embodiment. [Figure 20] 10 is an example syntax table showing the current sub-picture of each layer for each output layer set according to an embodiment. [Figure 21] 10 is an example of a syntax table of a video parameter set Raw Byte Sequence Payload (RBSP). [Figure 22] 10 is an example of a syntax table showing an output layer set in an output layer set mode. [Figure 23] 1 is an example of a syntax table illustrating reference picture resampling and resolution conversion in a video sequence coded with a Sequence Parameter Set (SPS). [Figure 24] 10 is an example of a syntax table showing picture sizes in PPS. [Figure 25A] 1 is a flowchart of an example process for decoding an encoded video bitstream, according to an embodiment. [Figure 25B] 1 is a flowchart of an example process for decoding an encoded video bitstream, according to an embodiment. [Figure 25C] 1 is a flowchart of an example process for decoding an encoded video bitstream, according to an embodiment. [Figure 26] FIG. 1 is a schematic diagram of a computer system according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1 illustrates a simplified block diagram of a communication system (100) according to an embodiment of the present disclosure. The system (100) may include at least two terminals (110, 120) interconnected via a network (150). For one-way data transmission, a first terminal (110) may code video data at a local location for transmission to another terminal (120) via the network (150). The second terminal (120) may receive the other terminal's encoded video data from the network (150), decode the coded data, and display the recovered video data. One-way data transmission may be common in media serving applications, for example.

[0014] 1 depicts a second pair of terminals (130, 140) equipped to support bidirectional transmission of coded video, such as may occur during a video conference. For bidirectional transmission of data, each terminal (130, 140) may code video data captured at a local location for transmission to the other terminal over the network (150). Each terminal (130, 140) may also receive coded video data transmitted by the other terminal, decode the coded data, and display the recovered video data on a local display device.

[0015] In FIG. 1 , the terminals (110-140) may be represented as servers, personal computers, and smartphones, although the principles of the present disclosure need not be so limited. Embodiments of the present disclosure find application in laptop computers, tablet computers, media players, and / or dedicated videoconferencing devices. The network (150) represents any number of networks that convey coded video data between the terminals (110-140), including, for example, wireline and / or wireless communication networks. The communication network (150) may exchange data over circuit-switched and / or packet-switched channels. Exemplary networks include telecommunications networks, local area networks, wide area networks, and / or the Internet. For purposes of this discussion, the architecture and topology of the network (150) may be irrelevant to the operation of the present disclosure, unless otherwise described hereinafter.

[0016] 2 depicts the placement of a video encoder and decoder in a streaming environment as an example application of the disclosed subject matter, which may be similarly applicable to other video-enabled applications including, for example, video conferencing, digital TV, storage of compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0017] The streaming system may include a video source (201) and a capture subsystem (213), which may include, for example, a digital camera, that generates uncompressed video samples. The sample stream (202), represented as a bold line to emphasize its high data volume compared to an encoded video bitstream, may be processed by an encoder (203) coupled to the camera (201). The encoder (203) may include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter, as described in further detail below. The encoded video bitstream (204), represented as a thin line to emphasize its low data volume compared to the sample stream, may be stored on a streaming server (205) for future use. One or more streaming clients (206, 208) may access the streaming server (205) to retrieve a copy of the encoded video bitstream (204). The client (206) can include a video decoder that decodes an incoming copy of the encoded video bitstream (207) and generates an outgoing video sample stream (211) that can be rendered on a display (212) or other rendering device (not shown). In some streaming systems, the video bitstreams (204, 207, 209) can be encoded according to a particular video coding / compression standard. An example of such a standard is ITU-T Recommendation H.265. A video coding standard commonly known as Versatile Video Coding, or VVC, is under development. The disclosed subject matter may be used in conjunction with VVC.

[0018] FIG. 3 illustrates a functional block diagram of a video decoder (210) according to an embodiment of the present disclosure.

[0019] The receiver (310) may receive one or more coded video sequences to be decoded by the decoder (210), one coded video sequence at a time, in the same or another embodiment. Decoding of each coded video sequence is independent of other coded video sequences. The coded video sequences may be received from a channel (312), which may be a hardware / software link to a storage device that stores the encoded video data. The receiver (310) may receive the encoded video data along with other data, such as coded audio data and / or auxiliary data streams, which may be forwarded to their respective using entities (not shown). The receiver (310) may separate the coded video sequences from other data. To combat network jitter, a buffer memory (315) may be coupled between the receiver (310) and the entropy decoder / parser (320) (hereinafter "parser"). When the receiver 310 is receiving data from a store-and-forward device with sufficient bandwidth and controllability, or from an isosynchronous network, the buffer 315 may not be needed or may be small. For use with best-effort packet networks such as the Internet, the buffer 315 may be needed and can be relatively large and adaptively sized.

[0020] The video decoder (210) may include a parser (320) for reconstructing symbols (321) from the entropy-coded video sequence. These symbol categories include information used to manage the operation of the decoder (210) and, potentially, information for controlling a rendering device, such as a display (212), which is not an internal part of the decoder but may be coupled to the decoder, as depicted in FIG. 3. Control information for the rendering device may take the form of a Supplementary Enhancement Information (SEI) message or a Video Usability Information (VUI) parameter set fragment (not shown). The parser (320) may parse / entropy decode the received coded video sequence. The coding of the coded video sequence may follow a video coding technique or standard and may follow principles well known to those skilled in the art, including variable length coding, Huffman coding, context-dependent or non-context-dependent arithmetic coding, etc. The parser (320) may extract from the coded video sequence a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder based on at least one parameter corresponding to the group. A subgroup may include a Group of Pictures (GOP), a picture, a subpicture, a tile, a slice, a brick, a macroblock, a Coding Tree Unit (CTU), a coding unit (CU), a block, a transform unit (TU), a prediction unit (PU), etc. A tile may refer to a rectangular region of a CU / CTU within a particular tile column and row in a picture. A brick may refer to a rectangular region of a CU / CTU row within a particular tile. A slice may refer to one or more bricks of a picture contained in a NAL unit. A subpicture may refer to a rectangular region of one or more slices in a picture.The entropy decoder / parser may also extract quantization parameter values, motion vectors, etc. from coded video sequence information such as transform coefficients.

[0021] The parser (320) may perform entropy decoding / parsing operations on the video sequence received from the buffer (315) to generate symbols (321).

[0022] The reconstruction of the symbols (321) can have a wide variety of units depending on the type of coded video picture or portion thereof (e.g., inter- and intra-picture, inter- and intra-block) and other factors. Which units are included and how they are included can be controlled by subgroup control information parsed by the parser (320) from the coded video sequence. The flow of such subgroup control information between the parser (320) and the following units is not shown for clarity.

[0023] Beyond the functional blocks already mentioned, decoder 210 may be conceptually subdivided into a number of functional units, which are described below. In an actual implementation operating under commercial constraints, many of these units may interact closely with each other and may be at least partially integrated with each other. However, for purposes of describing the disclosed subject matter, the following conceptual subdivision into functional units is appropriate.

[0024] The first unit is a scaler and / or inverse transform unit (351), which receives quantized transform coefficients as symbols (321) from the parser (320), along with control information including the transform to use, block size, quantization coefficients, quantization scaling matrices, etc. The scaler and / or inverse transform unit (351) can output blocks containing sample values ​​that can be input to an aggregator (355).

[0025] In some cases, the output samples of the scaler and / or inverse transform unit (351) may relate to intra-coded blocks, i.e., blocks that do not use prediction information from a previously reconstructed picture but can use prediction information from a previously reconstructed portion of the current picture. Such prediction information may be provided by an intra-picture prediction unit (352). In some cases, the intra-picture prediction unit (352) generates blocks of the same size and shape as the block being reconstructed using surrounding already reconstructed information fetched from the current (partially reconstructed) picture (358). The aggregator (355), in some cases, adds, on a sample-by-sample basis, the prediction information generated by the intra-prediction unit (352) to the output sample information provided by the scaler and / or inverse transform unit (351).

[0026] In other cases, the output samples of the scaler and / or inverse transform unit (351) may relate to an inter-coded, and potentially motion-compensated, block. In such cases, the motion-compensated prediction unit (353) may access a reference picture memory (357) to fetch samples used for prediction. After motion-compensating the fetched samples according to the block-related symbols (321), the samples may be added by an aggregator (355) to the output of the scaler and / or inverse transform unit (in this case, referred to as a residual sample or residual signal) to generate output sample information. The addresses in the reference picture memory from which the motion-compensated prediction unit fetches prediction samples may be controlled by a motion vector. A motion vector is available to the motion-compensated prediction unit in the form of a symbol (321), which may have, for example, X, Y, and reference picture components. Motion compensation may also include interpolation of sample values ​​fetched from the reference picture memory when sub-sample accurate motion vectors are used, motion vector prediction mechanisms, and the like.

[0027] The output samples of the aggregator (355) can be subjected to various loop filtering techniques in the loop filter unit (356). Video compression techniques can include in-loop filter techniques that are controlled by parameters contained in the coded video bitstream and made available to the loop filter unit (356) as symbols (321) from the parser (320), but can also respond to meta-information obtained during decoding of previous portions (in decoding order) of the coded picture or coded video sequence, and can even respond to previously constructed loop-filtered sample values.

[0028] The output of the loop filter unit (356) can be a sample stream that can be output to the render device (212) and further stored in a reference picture memory for use in future inter-picture prediction.

[0029] Once a particular coded picture is fully reconstructed, it can be used as a reference picture for future prediction. Once a coded picture is fully reconstructed and the coded picture is identified as a reference picture (e.g., by the parser (320)), the current reference picture (358) can become part of the reference picture memory (357), and any unused current picture memory can be reallocated before beginning reconstruction of a subsequent coded picture.

[0030] The video decoder (210) may perform decoding operations according to a predetermined video compression technology, which may be documented in a standard such as ITU-T Rec. H.265. A coded video sequence may conform to the syntax prescribed by the video compression technology or standard in use, in the sense that it conforms to the syntax of the video compression technology or standard as defined in the video compression technology document or standard, specifically in a profile document therein. Compliance also requires that the complexity of the coded video sequence be within the boundaries defined by the level of the video compression technology or standard. In some cases, the level limits the maximum picture size, maximum frame rate, maximum reconstruction sample rate (e.g., measured in megasamples per second), maximum reference picture size, etc. The limits set by the level may, in some cases, be further constrained through a Hypothetical Reference Decoder (HRD) specification and metadata for HRD buffer management signaled in the coded video sequence.

[0031] In embodiments, the receiver (310) may receive additional (redundant) data along with the encoded video. The additional data may also be included as part of the coded video sequence. The additional data may be used by the video decoder (210) to properly decode the data and / or to more accurately reconstruct the original video data. The additional data may take the form of, for example, temporal, spatial, or SNR enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0032] FIG. 4 may be a functional block diagram of a video encoder (203) according to an embodiment of the present disclosure.

[0033] The encoder (203) may receive video samples from a video source (201) (not part of the encoder) that may capture video images to be coded by the encoder (203).

[0034] The video source (201) may provide a source video sequence to be coded by the encoder (203) in the form of a digital video sample stream, which can be of any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, etc.), any color space (e.g., BT.601 YCrCB, RGB, etc.), and any suitable sampling structure (e.g., YCrCb 4:2:0, YCrCb 4:4:4). In a media serving system, the video source (201) may be a storage device storing previously prepared video. In a video conferencing system, the video source (201) may be a camera capturing local image information as a video sequence. The video data may be provided as multiple individual pictures that, when viewed in sequence, impart motion. The pictures themselves may be organized as a spatial array of pixels, each of which may have one or more samples depending on the sampling structure, color space, etc., in use. Those skilled in the art will readily understand the relationship between pixels and samples. This specification will focus on samples hereafter.

[0035] According to an embodiment, the encoder (203) may code and compress pictures of a source video sequence into a coded video sequence (443) in real time or under any other time constraints required by the application. Imposing an appropriate coding rate is one function of the controller (450). The controller may also control and be operatively coupled to other functional units, as described below. Coupling is not shown for clarity. Parameters set by the controller may include parameters related to rate control (picture skip, quantizer, lambda value for rate-distortion optimization techniques, etc.), picture size, group-of-picture (GOP) layout, maximum motion vector search range, etc. Those skilled in the art will readily identify other functions of the controller (450) as they may be relevant to optimizing the video encoder (203) for a particular system design.

[0036] Some video encoders operate in what those skilled in the art readily realize as a "coding loop." As an overly simplified description, the coding loop can consist of an encoding portion of an encoder (430) (hereinafter "source coder") (responsible for generating symbols based on an input picture to be coded and reference pictures), and a (local) decoder (433) embedded in the encoder (203) that reconstructs the symbols to generate sample data that a (remote) decoder will also generate (when any compression between the symbols and the coded video bitstream is lossless with the video compression techniques contemplated in the disclosed subject matter). The reconstructed sample stream is input to a reference picture memory (434). Because decoding of the symbol stream yields bit-exact results independent of the location of the decoder (local or remote), the contents of the reference picture memory are also bit-perfect between the local and remote encoders. That is, the prediction part of the encoder "sees" as reference picture samples exactly the same sample values ​​that the decoder will "see" when using the prediction during decoding. This basic principle of reference picture synchronicity (and the resulting drift when synchronicity cannot be maintained, e.g., due to channel errors) is well known to those skilled in the art.

[0037] The operation of the "local" decoder (433) can be the same as the "remote" decoder (210), already described in detail above in conjunction with Figure 3. Referring also briefly to Figure 4, however, because symbols are available and the encoding / decoding of symbols into a coded video sequence by the entropy coder (445) and parser (320) can be lossless, the entropy decoding portion of the decoder (210), including the channel (312), receiver (310), buffer (315), and parser (320), need not be fully implemented in the local decoder (433).

[0038] An observation that can be made at this point is that any decoder technique, with the exception of parsing / entropy decoding, that is present in the decoder must necessarily be present in substantially the same functional form in the corresponding encoder. For this reason, the disclosed subject matter focuses on the operation of the decoder. A description of the encoder techniques can be omitted, as they are the inverse of the decoder techniques that are generically described. Only to certain extents is a more detailed description required, and is provided below.

[0039] As part of its operation, the source coder (430) may perform motion-compensated predictive coding, which predictively codes an input picture with reference to one or more previously coded frames from the video sequence designated as "reference pictures." In this manner, the coding engine (432) codes differences between pixel blocks of the input picture and pixel blocks of the reference pictures that may be selected as predictive references for the input picture.

[0040] The local video decoder (433) may decode coded video data of frames that may be designated as reference frames based on symbols generated by the source coder (430). The operation of the coding engine (432) may advantageously be a lossy process. When the coded video data is decoded by a video decoder (not shown in FIG. 4), the reconstructed video sequence may typically be a copy of the source video sequence, with some errors. The local video decoder (433) may replicate the decoding process that may be performed by the video decoder on the reference frames, causing the reconstructed reference frames to be stored in a reference picture cache (434). In this way, the encoder (203) may locally store copies of reconstructed reference frames that have content in common with reconstructed reference frames that would be obtained by a far-end video decoder (without transmission errors).

[0041] The predictor (435) may perform the prediction search of the coding engine (432). That is, for a new picture to be coded, the predictor (435) may search the reference picture memory (434) for specific metadata, such as reference picture motion vectors, block shapes, or sample data (as candidate reference pixel blocks) that can serve as suitable prediction references for the new picture. The predictor (435) may operate on a sample block-by-pixel block basis to find suitable prediction references. In some cases, as determined by the search results obtained by the predictor (435), the input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory (434).

[0042] The controller (450) may manage the coding operations of the video coder (430), including, for example, setting the parameters and subgroup parameters used to encode the video data.

[0043] The output of all of the above functional units may undergo entropy coding in an entropy coder (445), which converts the symbols produced by the various functional units into a coded video sequence by losslessly compressing the symbols according to techniques known to those skilled in the art, such as Huffman coding, variable length coding, arithmetic coding, etc.

[0044] The transmitter (440) may buffer the coded video sequence produced by the entropy coder (445) to prepare it for transmission over a communication channel (460), which may be a hardware / software link to a storage device that stores the encoded video data. The transmitter (440) may merge the coded video data from the video coder (430) with other data to be transmitted, such as coded audio data and / or auxiliary data streams (sources not shown).

[0045] A controller (450) may manage the operation of the encoder (203). During coding, the controller (450) may assign a particular coded picture type to each coded picture, which may affect the coding technique that may be applied to each picture. For example, pictures may often be assigned as one of the following frame types:

[0046] An Intra Picture (I-picture) may be a picture that can be coded and decoded without using any other picture in the sequence as a source of prediction. Some video codecs allow various types of Intra pictures, including, for example, Independent Decoder Refresh (IDR) pictures. Those skilled in the art are aware of such variations of I-pictures and their respective applications and characteristics.

[0047] A Predictive Picture (P-picture) may be a picture that can be coded and decoded by intra-prediction or inter-prediction using at most one motion vector and reference index to predict the sample values ​​of each block.

[0048] A Bi-directionally Predictive Picture (B-picture) may be a picture that can be coded and decoded by intra- or inter-prediction using at most two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multiple-predictive pictures can use more than two reference pictures and associated metadata for the reconstruction of a single block.

[0049] A source picture is generally spatially subdivided into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples, respectively) and may be coded block by block. Blocks may be predictively coded with reference to other (already coded) blocks as determined by the coding assignment applied to each picture of the blocks. For example, blocks of an I-picture may be coded non-predictively, or they may be predictively coded with reference to already coded blocks of the same picture (spatial prediction or intra-prediction). Pixel blocks of a P-picture may be coded non-predictively, or with spatial prediction or temporal prediction with reference to one previously coded reference picture. Blocks of a B-picture may be coded non-predictively, or with spatial prediction or temporal prediction with reference to one or two previously coded reference pictures.

[0050] The video coder (203) may perform coding operations according to a predetermined video coding technique or standard, such as ITU-T Rec. H.265. During its operation, the video coder (203) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancy in the input video sequence. Thus, the coded video data may conform to a syntax defined by the video coding technique or standard being used.

[0051] In embodiments, the transmitter (440) may transmit additional data along with the encoded video. The video coder (430) may include such data as part of the coded video sequence. The additional data may include temporal / spatial / SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, SEI messages, VUI parameter set fragments, etc.

[0052] In recent years, compressed domain aggregation or extraction of multiple semantically independent picture portions into a single video picture has attracted attention. In particular, for example, in connection with 360-degree coding or certain surveillance applications, multiple semantically independent source pictures (e.g., six cubic sides of a cubic-projected 360-degree scene, or individual camera inputs in the case of other camera surveillance setups) may require separate adaptive resolution settings to address different scene-specific activity at a given time. That is, an encoder may choose to use different resampling factors for the different semantically independent pictures that make up the entire 360-degree or surveillance scene at a given time. When combined into a single picture, reference picture resampling then needs to be performed, and adaptive resolution coding signaling is available for the coded picture portions.

[0053] Below are introduced a few items that will be referenced in the remainder of this specification.

[0054] A subpicture may refer to a rectangular arrangement of samples, blocks, macroblocks, coding units, or similar entities that are semantically grouped and may be coded independently at varying resolutions. One or more subpictures may form a picture. One or more coded subpictures may form a coded picture. One or more subpictures may be combined into a picture, and one or more subpictures may be extracted from a picture. In certain circumstances, one or more coded subpictures may be combined into a picture coded in the compressed domain without transcoding to the same level, and in the same or other cases, one or more coded subpictures may be extracted from a subpicture coded in the compressed domain.

[0055] Adaptive Resolution Change (ARC) may refer to a mechanism that allows for changing the resolution of pictures or subpictures within a coded video sequence, for example, by reference picture resampling. ARC parameters hereafter refer to the control information needed to perform adaptive resolution change and may include, for example, filter parameters, scaling factors, output and / or reference picture resolutions, various control flags, etc.

[0056] In an embodiment, coding and decoding may be performed on a single, semantically independent coded video picture. Before describing the implications of coding / decoding multiple sub-pictures with independent ARC parameters and the additional complexity it implies, options for signaling the ARC parameters should be explained.

[0057] 5A-5E, several embodiments for signaling ARC parameters are shown. As each of the embodiments is described, they may have certain advantages and disadvantages from a coding efficiency, complexity, and architecture perspective. A video coding standard or technology may select one or more of these embodiments, or options known from the related art, for signaling ARC parameters. The embodiments may not be mutually exclusive and may conceivably be interchanged based on application needs, related standard technology, or encoder choice.

[0058] The classification of ARC parameters includes: Separate or combined upsample and / or downsample coefficients in the X and Y dimensions, Upsampling and / or downsampling factors with an added time dimension that indicates a constant speed of zooming in / out for a given number of pictures may be included.

[0059] Either of the above two may involve coding one or more, possibly short, syntax elements that may point to a table containing the coefficients.

[0060] Resolution may refer to the resolution in the X or Y dimension, in combination or separately, of an input picture, an output picture, a reference picture, a coded picture sample, a block, a macroblock, a CU, or any other suitable unit of granularity. When there is more than one resolution (e.g., one for the input picture and one for the reference picture), one set of values ​​may be inferred from the other set of values ​​in certain cases. Resolution may also be gated, for example, by the use of a flag. See below for more detailed examples.

[0061] The "warping" coordinates may be similar to those used in H.263 Annex P, and again at the appropriate granularity described above. H.263 Annex P defines one efficient method for coding such warping coordinates, but other, potentially more efficient methods may conceivably be devised. For example, the variable-length reversible "Huffman"-style coding of Annex P's warping coordinates may be replaced by appropriate-length binary coding, where the length of the binary codewords may be derived, for example, from the maximum picture size, and possibly multiplied by a specific factor and offset by a specific value to allow "warping" outside the bounds of the maximum picture size.

[0062] Upsample and / or Downsample Filter Parameters. In embodiments, there may be only a single filter for upsampling and / or downsampling. However, in embodiments, it may be desirable to allow more flexibility in filter design, which may require signaling of filter parameters. Such parameters may be selected by an index in a list of possible filter designs, the filter may be fully specified (e.g., through a list of filter coefficients using an appropriate entropy coding technique), or the filter may be implicitly selected by an upsample and / or downsample ratio signaled according to any of the mechanisms described above, etc.

[0063] Hereafter, the description assumes coding of a finite set of upsample and / or downsample coefficients indicated by a codeword, where the same coefficients are used in both the X and Y dimensions. The codeword may be variable length coded, for example, by using Ext-Golomb codes common to certain syntax elements in video coding standards such as H.264 and H.265. One suitable mapping of values ​​to upsample and / or downsample coefficients may, for example, follow Table 1 below. [Table 1]

[0064] Many similar mappings can be devised according to the needs and capabilities of the application of up- and down-scaling mechanisms available in video compression technologies or standards. The table may be extended to more values. The values ​​may also be represented by entropy coding mechanisms other than Ext-Golomb codes, for example, using binary coding. This may have particular advantages when the resampling factor is significant outside the video processing engines (primarily the encoder and decoder) themselves, for example, by MANE. It should be noted that for situations where resolution change is not required, short (e.g., only a single bit in the above table) Ext-Golomb codes can be selected, which may be more coding efficient than using binary codes for the most general cases.

[0065] The number of entries in the table and their semantics may be fully or partially configurable. For example, the basic outline of the table may be conveyed in a "high" parameter set, such as a sequence or decoder parameter set. In an embodiment, one or more such tables may be defined in a video coding technology or standard and may be selected, for example, by a decoder or sequence parameter set.

[0066] The following describes how the upsample and / or downsample coefficients (ARC information) coded as described above can be included in a video coding technique or standard syntax. Similar considerations apply to one or several codewords that control the upsample and / or downsample filters. See below for a discussion of when a relatively large amount of data may be required for a filter or other data structure.

[0067] As shown in Figure 5A, H.263 Annex P includes ARC information (502) in the form of four warping coordinates within the picture header (501), specifically in the H.263 PLUSPTYPE (503) header extension. This can be a reasonable design choice when (a) there is a picture header available and (b) frequent changes in ARC information are expected. However, the overhead when using H.263-style signaling can be quite high, and scaling factors may not adhere to picture boundaries due to the transient nature of picture headers.

[0068] As shown in Figure 5B, JVCET-M135-v1 includes an ARC reference (505) (index) located in a picture parameter set (504) that indexes a table (506) containing target resolutions located in a sequence parameter set (507). The placement of possible resolutions in table (506) in a sequence parameter set (507) can be justified, according to verbal statements by the authors, by using the SPS (507) as an interoperability negotiation point during capability exchange. Resolution can be varied within limits set by the values ​​in table (506) on a picture-by-picture basis by referencing the appropriate picture parameter set (504).

[0069] 5E-5E, the following embodiments may exist for carrying ARC information in a video bitstream. Each of these options has certain advantages over the above embodiments. The embodiments may exist simultaneously within the same video coding technology or standard.

[0070] In embodiments, such as the embodiment shown in FIG. 5C, ARC information (509), such as a resampling (zoom) factor, may be present in a slice header, a GOB header, a tile header, or a tile group header. FIG. 5C illustrates an embodiment in which a tile group header (508) is used. This can be appropriate when the ARC information is small, such as a single variable-length ue(v) or fixed-length codeword of a few bits, as described above. Having the ARC information directly in the tile group header has the additional advantage that the ARC information may be applicable, for example, to the sub-picture represented by that tile group, rather than to the entire picture. See also below. Furthermore, even if a video compression technology or standard contemplates resolution changes that are applicable only to the entire picture (as opposed to, for example, adaptive resolution changes based on tile groups), placing the ARC information in the tile group header, as opposed to placing it in an H263-style picture header, has certain advantages from an error resilience perspective.

[0071] In embodiments, such as the embodiment shown in FIG. 5D, the ARC information (512) itself may reside in an appropriate parameter set, such as a picture parameter set, a header parameter set, a tile parameter set, an adaptive parameter set, etc. FIG. 5D depicts an embodiment in which an adaptive parameter set (511) is used. The scope of that parameter set advantageously is no larger than a picture and can be, for example, a tile group. The use of the ARC information may be implicit through the activation of an associated parameter set. For example, if a video coding technology or standard only contemplates picture-based ARC, a picture parameter set or equivalent may be appropriate.

[0072] In an embodiment, such as the embodiment shown in Figure 5E, the ARC reference information (513) may reside in a tile group header (514) or similar data structure, and may reference a subset of the ARC information (515) available in a parameter set (516) with a scope beyond a single picture, such as a sequence parameter set or a decoder parameter set.

[0073] As shown in FIG. 6A, the tile group header (601), an example syntax structure for a header applicable to a (possibly rectangular) portion of a picture, can conditionally contain the variable-length Exp-Golomb coded syntax element dec_pic_size_idx (602) (shown in bold). The presence of this syntax element in the tile group header can be gated on the use of adaptive resolution (603). Here, the flag value is not shown in bold, which means that the flag is present in the bitstream at the time it occurs in the syntax diagram. Whether adaptive resolution is in use for this picture or its portion can be signaled in any higher-level syntax structure within or outside the bitstream. In the example shown, adaptive resolution is signaled in the sequence parameter set, as described below.

[0074] Referring to Figure 6B, an excerpt of a sequence parameter set (610) is also shown. The first syntax element shown is adaptive_pic_resolution_change_flag (611). If true, that flag may indicate the use of adaptive resolution, which in turn may require specific control information. In the example, such control information is conditionally present based on the value of the flag based on an if() statement in the parameter set (612) and the tile group header (600).

[0075] When adaptive resolution is in use, the output resolution is coded in units of samples (613), in this example. The number 613 refers to both output_pic_width_in_luma_samples and output_pic_height_in_luma_samples, which together can define the resolution of the output picture. Specific restrictions on either value may be defined elsewhere in the video coding technology or standard. For example, a level definition may limit the total number of output samples that can be the product of the values ​​of those two syntax elements. Also, a particular video coding technology or standard, or an external technology or standard such as a system standard, may limit the numbering range (e.g., one or both dimensions should be divisible by a power of 2) or the aspect ratio (e.g., width and height must have a relationship such as 4:3 or 16:9). Such restrictions may be introduced to facilitate hardware implementation or for other reasons and are well known in the art.

[0076] In certain applications, it may be wise for an encoder to instruct a decoder to use a particular picture size rather than implicitly assuming that size to be the output picture size. In this example, the syntax element reference_pic_size_present_flag (614) gates the conditional presence of the reference picture dimensions (615) (again, the numbers refer to both width and height).

[0077] Finally, a table of possible decoded picture widths and heights is shown. Such a table can be represented, for example, by a table directive (num_dec_pic_size_in_luma_samples_minus1) (616). "minus1" can refer to the interpretation of the value of that syntax element. For example, if the coded value of the syntax element is 0, there is one table entry. If the coded value is 5, there are six table entries. For each "row" of the table, the decoded picture width and height are then included in the syntax (617).

[0078] The represented table entry (617) can be indexed using the syntax element dec_pic_size_idx (602) in the tile group header, thereby allowing different decoding sizes, in effect zoom factors, per tile group.

[0079] Certain video coding techniques or standards, e.g., VP9, ​​support spatial scalability by implementing a particular form of reference picture resampling (signaled entirely separately from the disclosed subject matter) along with temporal scalability to enable spatial scalability. In particular, certain reference pictures may be upsampled to higher resolutions using ARC-style techniques to form the basis of spatial enhancement layers. These upsampled pictures may then be refined using conventional prediction mechanisms at the higher resolutions to add detail.

[0080] The embodiments described herein can be used in such environments. In certain cases, in the same or other embodiments, values ​​in NAL unit headers, e.g., in a Temporal ID field, can be used to indicate not only temporal layers but also spatial layers. Doing so can have certain advantages for certain system designs. For example, existing Selected Forwarding Units (SFUs) that are generated and optimized for temporal layer selective forwarding based on the Temporal ID value in the NAL unit header can be used without modification for scalable environments. To make that possible, the mapping between coded pictures and temporal layers needs to be indicated by the Temporal ID field in the NAL unit header.

[0081] In some video coding techniques, an Access Unit (AU) can refer to a coded picture, slice, tile, NAL unit, etc. captured at a given point in time and organized into a respective picture, slice, tile, and / or NAL unit bitstream. Such a point in time can be composition time.

[0082] In HEVC and certain other video coding technologies, a Picture Order Count (POC) value may be used to indicate a reference picture selected from multiple reference pictures stored in a Decoded Picture Buffer (DPB). When an access unit (AU) includes one or more pictures, slices, or tiles, each picture, slice, or tile belonging to the same AU may carry the same POC value, from which it can be derived that they were generated from content with the same composition time. That is, in a scenario where two pictures / slices / tiles carry the same given POC value, it can be determined that the two pictures / slices / tiles belong to the same AU and have the same composition time. In contrast, two pictures / tiles / slices with different POC values ​​may indicate that the pictures / slices / tiles belong to different AUs and have different composition times.

[0083] In embodiments, this rigid relationship may be relaxed in that an access unit may contain pictures, slices, or tiles with different POC values. By allowing different POC values ​​within an AU, it becomes possible to use the POC values ​​to identify potentially independently decodable pictures / slices / tiles that have the same presentation time. This, in turn, may enable support for multiple scalable layers without changes to reference picture selection signaling, e.g., reference picture set signaling or reference picture list signaling, as described in more detail below.

[0084] However, it is still desirable to be able to identify the AU to which a picture / slice / tile belongs, relative to other pictures / slices / tiles with different POC values, from the POC value alone. This can be achieved as described below.

[0085] In an embodiment, an Access Unit Count (AUC) may be signaled in a high-level syntax structure such as a NAL unit header, a slice header, a tile group header, an SEI message, a parameter set, or an AU delimiter. The value of AUC may be used to identify which NAL unit, picture, slice, or tile belongs to a given AU. The value of AUC may correspond to a distinct compositing time instance. The AUC value is equal to a multiple of the POC value. The AUC value may be calculated by dividing the POC value by an integer value. In certain cases, the division may impose a certain burden on the decoder implementation. In such cases, a small limitation in the numbering space of AUC values ​​may allow for the replacement of the division by a shift operation. For example, the AUC value is equal to the most significant bit (MSB) value of the POC value range.

[0086] In an embodiment, the value of the POC cycle per AU (poc_cycle_au) may be signaled in a high-level syntax structure, such as a NAL unit header, a slice header, a tile group header, an SEI message, a parameter set, or an AU delimiter. poc_cycle_au may indicate how multiple different consecutive POC values ​​can be associated with the same AU. For example, if the value of poc_cycle_au is equal to 4, pictures, slices, or tiles having POC values ​​equal to or greater than 0 and equal to or less than 3 may be associated with AUs having AUC values ​​equal to 0, and pictures, slices, or tiles having POC values ​​equal to or greater than 4 and equal to or less than 7 may be associated with AUs having AUC values ​​equal to 1. Thus, the value of AUC may be inferred by dividing the POC value by poc_cycle_au.

[0087] In embodiments, the value of poc_cycle_au may be derived from information located, for example, in a video parameter set (VPS) that identifies the number of spatial or SNR layers in the coded video sequence. Examples of such possible relationships are briefly described below. While the derivation described above may save a few bits in the VPS and thus improve coding efficiency, in some embodiments, poc_cycle_au may be explicitly coded in an appropriate higher-level syntax structure hierarchically below the video parameter set to be able to minimize poc_cycle_au for a given small portion of the bitstream, such as a picture. This optimization may save more bits than would be possible through the above derivation process, because the POC value and / or values ​​of syntax elements that indirectly reference the POC may be coded in lower-level syntax structures.

[0088] In an embodiment, Figure 8 shows an example of a syntax table for signaling the vps_poc_cycle_au syntax element in the VPS (or SPS), which indicates the poc_cycle_au used for all pictures / slices in the coded video sequence, and the slice_poc_cycle_au syntax element, which indicates the poc_cycle_au of the current slice in the slice header. If the POC value increases uniformly per AU, vps_contant_poc_cycle_per_au in the VPS may be set equal to 1, and vps_poc_cycle_au may be signaled in the VPS. In this case, slice_poc_cycle_au may not be explicitly signaled, and the AUC value for each AU may be calculated by dividing the POC value by vps_poc_cycle_au. If the POC value does not increase uniformly per AU, vps_contant_poc_cycle_per_au in the VPS may be set equal to 0. In this case, vps_access_unit_cnt may not be signaled, while slice_access_unit_cnt may be signaled in the slice header for each slice or picture. Each slice or picture may have a different value of slice_access_unit_cnt. The value of AUC for each AU may be calculated by dividing the value of POC by slice_poc_cycle_au.

[0089] 9 shows a block diagram illustrating an example of the above process. For example, in operation S910, a VPS (or SPS) may be parsed, and in operation S920, it may be determined whether the POC cycle per AU is constant within the coded video sequence. If the POC cycle per AU is constant (YES in operation S920), then in operation S930, a value of the access unit count for a particular access unit may be calculated from the poc_cycle_au signaled for the coded video sequence and the POC value of the particular access unit. If the POC cycle per AU is not constant (NO in operation S920), then in operation S940, a value of the access unit count for a particular access unit may be calculated from the poc_cycle_au signaled at a particular level and the POC value of the particular access unit. In operation S950, a new VPS (or SPS) may be parsed.

[0090] In an embodiment, pictures, slices, or tiles corresponding to AUs having the same AUC value may be associated with the same decoding or output time instance, even though the POC values ​​of the pictures, slices, or tiles may be different. Thus, all or a subset of pictures, slices, or tiles associated with the same AU may be decoded in parallel and output at the same time instance, without any mutual parsing / decoding dependencies between pictures, slices, or tiles within the same AU.

[0091] In an embodiment, pictures, slices, or tiles corresponding to AUs with the same AUC value may be associated with the same composition / display time instance, even though the POC values ​​of the pictures, slices, or tiles may be different. If the composition time is included in the container format, pictures may be displayed at the same time instance if they have the same composition time, even if they correspond to different AUs.

[0092] In an embodiment, each picture, slice, or tile may have the same temporal identifier (temporal_id) in the same AU. All or a subset of pictures, slices, or tiles corresponding to a time instance may be associated with the same temporal sublayer. In an embodiment, each picture, slice, or tile may have the same or different spatial layer id (element layer_id) in the same AU. All or a subset of pictures, slices, or tiles corresponding to a time instance may be associated with the same or different spatial layers.

[0093] 7 shows an example of a video sequence structure with a combination of temporal_id, layer_id, and POC and AUC values ​​with adaptive resolution change. In this example, a picture, slice, or tile in the first AU with AUC=0 may have temporal_id=0 and layer_id=0 or 1, while a picture, slice, or tile in the second AU with AUC=1 may have temporal_id=1 and layer_id=0 or 1, respectively. The value of POC increases by 1 for each picture regardless of the values ​​of temporal_id and layer_id. In this example, the value of poc_cycle_au is equal to 2. In an embodiment, the value of poc_cycle_au may be set equal to the number of (spatial scalability) layers. Therefore, in this example, the value of POC increases by 2, while the value of AUC increases by 1.

[0094] In the above embodiments, all or a subset of the inter-picture or inter-layer prediction structure and reference picture indication may be supported by using the existing reference picture set (RPS) signaling or reference picture list (RPL) signaling in HEVC. In the RPS or RPL, the selected reference picture may be indicated by signaling the value of POC or the difference value of POC between the current picture and the selected reference picture. In embodiments, the RPS or RPL may be used to indicate the inter-picture or inter-layer prediction structure without any signaling changes, but with the following restrictions: If the value of the temporal_id of a reference picture is greater than the value of the temporal_id of the current picture, the current picture may not use the reference picture for motion compensation or other prediction. If the value of the layer_id of a reference picture is greater than the value of the layer_id of the current picture, the current picture may not use the reference picture for motion compensation or other prediction.

[0095] In an embodiment, motion vector scaling based on POC difference for temporal motion vector prediction may be disabled across multiple pictures within an access unit. Thus, although each picture may have a different POC value within an access unit, motion vectors may not be scaled and used for temporal motion vector prediction within the access unit. This is because reference pictures with different POCs in the same AU are considered to be reference pictures with the same time instance. Thus, in an embodiment, the motion vector scaling function may return 1 if the reference picture belongs to the AU associated with the current picture.

[0096] In an embodiment, motion vector scaling based on POC difference for temporal motion vector prediction may be optionally disabled across multiple pictures if the spatial resolution of the reference picture is different from the spatial resolution of the current picture. When motion vector scaling is allowed, the motion vector is scaled based on both the POC difference and the spatial resolution ratio between the current picture and the reference picture.

[0097] In an embodiment, motion vectors may be scaled based on the AUC differential instead of the POC differential for temporal motion vector prediction, especially when poc_cycle_au has a non-uniform value (when vps_contant_poc_cycle_per_au==0), otherwise (when vps_contant_poc_cycle_per_au==1), the motion vector scaling based on the AUC differential may be the same as the motion vector scaling based on the POC differential.

[0098] In an embodiment, when a motion vector is scaled based on an AUC difference, a reference motion vector (having the same AUC value) within the same AU containing the current picture is not scaled based on the AUC difference and is used for motion vector prediction with or without scaling based on the spatial resolution ratio between the current picture and the reference picture.

[0099] In an embodiment, the AUC value is used to identify AU boundaries and for hypothetical reference decoder (HRD) operations that require input and output timing at AU granularity. In an embodiment, a decoded picture having the top layer of an AU may be output for display. The AUC value and layer_id value may be used to identify the output picture.

[0100] In embodiments, a picture may contain one or more sub-pictures. Each sub-picture may cover a local area or the entire area of ​​the picture. The area supported by a sub-picture may or may not overlap with the area supported by other sub-pictures. The area covered by one or more sub-pictures may or may not cover the entire area of ​​the picture. When a picture contains a sub-picture, the area supported by the sub-picture may be the same as the area supported by the picture.

[0101] In embodiments, sub-pictures may be coded by a coding method similar to that used for the coded picture. Sub-pictures may be coded independently or may be coded with a dependency on other sub-pictures or coded pictures. Sub-pictures may or may not have any parsing dependency from other sub-pictures or coded pictures.

[0102] In embodiments, coded sub-pictures may be included in one or more layers. Coded sub-pictures within a layer may have different spatial resolutions. Original sub-pictures may be spatially resampled (upsampled or downsampled), coded with different spatial resolution parameters, and included in the bitstream corresponding to the layer.

[0103] In an embodiment, a sub-picture having (W, H), where W denotes the width of the sub-picture and H denotes the height of the sub-picture, may be coded and included in the coded bitstream corresponding to layer 0, while a sub-picture having (W×S), which is upsampled (or downsampled) from a sub-picture having the original spatial resolution, may have (W×S), which is downsampled (or upsampled) from a sub-picture having the original spatial resolution. w,k ,H×S h,k ) may be coded and included in the coded bitstream corresponding to layer k, where Sw,k , S h,k are the resampling ratios in the horizontal and vertical directions, respectively. w,k , S h,k If the value of is greater than 1, the resampling may be an upsampling. w,k , S h,k If the value of is less than 1, the resampling may be downsampling.

[0104] In embodiments, a coded subpicture within a layer may have a different visual quality than that of a coded subpicture in another layer, either in the same subpicture or in a different subpicture. For example, subpicture i in layer n may have a different visual quality than that of a coded subpicture in another layer, either in the same subpicture or in a different subpicture. i,n while subpicture j in layer m may be coded with quantization parameter Q j,m It may be coded as:

[0105] In an embodiment, coded sub-pictures within a layer may be independently decodable without any parsing or decoding dependency from coded sub-pictures in other layers of the same local region. A sub-picture layer that can be independently decodable without reference to other sub-picture layers of the same local region may be an independent sub-picture layer. Coded sub-pictures within an independent sub-picture layer may or may not have decoding or parsing dependencies from previously coded sub-pictures in the same sub-picture layer, but the coded sub-pictures may not have any dependencies from coded sub-pictures in other sub-picture layers.

[0106] In an embodiment, coded subpictures within a layer may be dependently decodable, having some parsing or decoding dependency from coded subpictures in other layers of the same local region. A subpicture layer that can be dependently decodable by reference to other subpicture layers of the same local region may be a dependent subpicture layer. A coded subpicture within a dependent subpicture layer may refer to coded subpictures belonging to the same subpicture, previously coded subpictures in the same subpicture layer, or both reference subpictures.

[0107] In an embodiment, a coded subpicture may include one or more independent subpicture layers and one or more dependent subpicture layers. However, at least one independent subpicture layer may exist for a coded subpicture. The value of the layer identifier (layer_id), which may be present in the NAL unit header or other high-level syntax structure of an independent subpicture layer, will be equal to 0. A subpicture layer with layer_id equal to 0 may be a base subpicture layer.

[0108] In an embodiment, a picture may include one or more foreground subpictures and one background subpicture. The area supported by a background subpicture may be equal to the area of ​​the picture. The area supported by a foreground subpicture may overlap the area supported by a background subpicture. A background subpicture may be a base subpicture layer, while a foreground subpicture may be a non-base (enhancement) subpicture layer. One or more non-base subpicture layers may reference the same base layer for decoding. Each non-base subpicture layer with layer_id equal to a may reference a non-base subpicture layer with layer_id equal to b, where a is greater than b.

[0109] In an embodiment, a picture may include one or more foreground subpictures, with or without background subpictures. Each subpicture may have its own base subpicture layer and one or more non-base (enhancement) layers. Each base subpicture layer may be referenced by one or more non-base subpicture layers. Each non-base subpicture layer with layer_id equal to a may reference a non-base subpicture layer with layer_id equal to b, where a is greater than b.

[0110] In an embodiment, a picture may contain one or more foreground subpictures with or without background subpictures. Each coded subpicture in a subpicture layer (base or non-base) may be referenced by one or more non-base layer subpictures that belong to the same subpicture and one or more non-base layer subpictures that do not belong to the same subpicture.

[0111] In an embodiment, a picture may include one or more foreground subpictures with or without background subpictures. A subpicture in layer a may be further partitioned into multiple subpictures within the same layer. One or more coded subpictures in layer b may reference a partitioned subpicture in layer a.

[0112] In an embodiment, a coded video sequence (CVS) may be a group of coded pictures. A CVS may contain one or more coded sub-picture sequences (CSPS), which may be a group of coded sub-pictures covering the same local region of a picture. A CSPS may have the same or a different temporal resolution than that of the coded video sequence.

[0113] In an embodiment, a CSPS may be coded and included in one or more layers. A CSPS may include one or more CSPS layers. Decoding one or more CSPS layers corresponding to a CSPS may reconstruct a sequence of sub-pictures corresponding to the same local region.

[0114] In an embodiment, the number of CSPS layers corresponding to a CSPS may be the same as or different from the number of CSPS layers corresponding to other CSPSs.

[0115] In an embodiment, a CSPS layer may have a different temporal resolution (e.g., frame rate) than other CSPS layers, and the original (uncompressed) sub-picture sequence may be temporally resampled (e.g., upsampled or downsampled), coded with different temporal resolution parameters, and included in the bitstream corresponding to the layer.

[0116] In an embodiment, a sub-picture sequence with a frame rate F may be coded and included in the coded bitstream corresponding to layer 0, while a sub-picture sequence with a frame rate F×S may be temporally upsampled (or downsampled) from the original sub-picture sequence. t,k may be coded and included in the coded bitstream corresponding to layer k, where S t,k denotes the temporal sampling ratio for layer k. t,k If the value of S is greater than 1, the temporal resampling process may be a frame rate up-conversion. t,k If is less than 1, the temporal resampling process may be a frame rate down-conversion.

[0117] In an embodiment, when a subpicture with CSPS layer a is referenced by a subpicture with CSPS layer b for motion compensation or some inter-layer prediction, if the spatial resolution of CSPS layer a is different from the spatial resolution of CSPS layer b, the decoded pixels in CSPS layer a are resampled and used for reference. The resampling process may use upsampling filtering or downsampling filtering.

[0118] Figure 10 shows an example of a video stream including a background video CSPS with layer_id equal to 0 and multiple foreground CSPS layers. A coded subpicture may include one or more CSPS layers, while background regions that do not belong to any foreground CSPS layer may include the base layer. The base layer may include background and foreground regions, while the enhancement CSPS layer may include foreground regions. The enhancement CSPS layer may have better visual quality than the base layer for the same region. The enhancement CSPS layer may reference the motion vectors and reconstructed pixels of the base layer corresponding to the same region.

[0119] In an embodiment, in a video file, the video bitstream corresponding to the base layer is contained in a track, while the CSPS layers corresponding to each sub-picture are contained in separate tracks.

[0120] In an embodiment, the video bitstream corresponding to the base layer is included in a track, while the CSPS layers with the same layer_id are included in separate tracks. In this example, the track corresponding to layer k includes only the CSPS layer corresponding to layer k.

[0121] In an embodiment, each CSPS layer of each subpicture is stored in a separate track, and each track may or may not have any parsing or decoding dependencies from one or more other tracks.

[0122] In an embodiment, each track may include a bitstream corresponding to layers i to j of the CSPS layer of all or a subset of subpictures, where 0 < i <= j <= k and k is the highest layer of CSPS.

[0123] In an embodiment, a picture includes one or more associated media data including a depth map, an alpha map, 3D geometry data, an occupancy map, etc. Such associated timed media data can be divided into one or more data substreams each corresponding to one subpicture.

[0124] FIG. 11 shows an example of a video conference based on a multi-layer subpicture method. The video stream includes one basic layer video bitstream corresponding to a background picture and one or more enhancement layer video bitstreams corresponding to foreground subpictures. Each enhancement layer video bitstream may correspond to a CSPS layer. On the display, the picture corresponding to the basic layer is displayed by default. The basic layer includes Picture In Picture (PIP) of one or more users. When a specific user is selected under the control of the client, the enhancement CSPS layer corresponding to the selected user can be decoded and displayed with improved quality or spatial resolution.

[0125] 12 shows a block diagram illustrating an example of the above process. For example, at operation S1210, a video bitstream including multiple layers may be decoded. At operation S1220, a background region and one or more foreground subpictures may be identified. At operation S1230, it may be determined whether a particular subpicture region, e.g., one of the foreground subpictures, is selected. If a particular subpicture region is selected (YES at operation S1240), the enhanced subpicture may be decoded and displayed. If a particular subpicture region is not selected (NO at operation S1240), the background region may be decoded and displayed.

[0126] In embodiments, a network middlebox (e.g., a router) may select a subset of layers to send to a user depending on its bandwidth. The picture / subpicture organization may be used for bandwidth adaptation. For example, if a user does not have the bandwidth, the router may remove layers or select some subpictures based on their importance or the settings being used. This may be done dynamically to adapt to the bandwidth.

[0127] 13 illustrates an embodiment related to a 360-degree video use case. When a spherical 360-degree picture, e.g., picture 1310, is projected onto a planar picture, the projected 360-degree picture may be partitioned into multiple subpictures as a base layer. For example, the multiple subpictures may include a back subpicture, a top subpicture, a right subpicture, a left subpicture, a front subpicture, and a ↓ subpicture. An enhancement layer for a particular subpicture, e.g., a front subpicture, may be coded and transmitted to a client. A decoder may be able to decode both the base layer including all subpictures and the enhancement layer for a selected subpicture. If the current viewport is the same as the selected subpicture, the displayed picture may have higher quality in the decoded subpicture with the enhancement layer. Otherwise, the decoded picture including the base layer may be displayed with lower quality.

[0128] In an embodiment, any layout information for display may be present in the file as supplemental information (e.g., SEI messages or metadata). One or more decoded sub-pictures may be rearranged or displayed according to the signaled layout information. The layout information may be signaled by a streaming server or broadcaster, or may be played by a network entity or cloud server, or may be determined by a user's customized settings.

[0129] In an embodiment, when an input picture is divided into one or more (rectangular) sub-regions, each sub-region may be coded as an independent layer. Each independent layer corresponding to a local region may have a unique layer_id value. For each independent layer, sub-picture size and position information may be signaled. For example, picture size (width, height) and upper-left corner offset information (x_offset, y_offset) may be signaled. Figure 14 shows an example of a layout of divided sub-pictures, their sub-picture size and position information, and their corresponding picture prediction structure. Layout information including sub-picture size and sub-picture position may be signaled in a higher-level syntax structure such as a parameter set, a slice or tile group header, or an SEI message.

[0130] In an embodiment, each sub-picture corresponding to an independent layer may have its unique POC value within the AU, and the POC value of each sub-picture corresponding to a layer may be used when a reference picture in a picture stored in the DPB is indicated by using a syntax element in the RPS or RPL structure.

[0131] In an embodiment, the layer_id may not be used and the POC (difference) value may be used to indicate the (inter-layer) prediction structure.

[0132] In an embodiment, a sub-picture having a POC value equal to N corresponding to a layer (or local region) may or may not be used as a reference picture for a sub-picture having a POC value equal to K+N corresponding to the same layer (or the same local region) for motion compensated prediction. In most cases, the value of the number K will be equal to the maximum number of (independent) layers, which may be the same as the number of sub-regions.

[0133] In an embodiment, Figure 15 represents an extended case of Figure 14. When an input picture is divided into multiple (e.g., four) sub-regions, each local region may be coded with one or more layers. In this case, the number of independent layers may be equal to the number of sub-regions, and one or more layers may correspond to one sub-region. Thus, each sub-region may be coded with one or more independent layers and zero or more dependent layers.

[0134] 15, the input picture may be divided into four sub-regions. For example, the top-right sub-region may be coded as two layers, Layer 1 and Layer 4, while the bottom-right sub-region may be coded as two layers, Layer 3 and Layer 5. In this case, Layer 4 may refer to Layer 1 for motion-compensated prediction, while Layer 5 may refer to Layer 3 for motion compensation.

[0135] In an embodiment, in-loop filtering across layer boundaries (e.g., deblocking filtering, adaptive in-loop filtering, reshaper, bilateral filtering, or any deep learning based filtering) may be (optionally) disabled.

[0136] In an embodiment, motion compensated prediction or intra block copying across layer boundaries may (optionally) be disabled.

[0137] In an embodiment, boundary padding for motion compensated prediction or in-loop filtering at sub-picture boundaries may be optionally processed. A flag indicating whether boundary padding is processed may be signaled in a higher level syntax structure, such as a parameter set (VPS, SPS, PPS, or APS), a slice or tile group header, or an SEI message.

[0138] In an embodiment, layout information for sub-regions (or sub-pictures) may be signaled in the VPS or the SPS. Figure 16A shows an example of syntax elements in the VPS, and Figure 16B shows an example of syntax elements in the SPS. In this example, vps_sub_picture_dividing_flag is signaled in the VPS. The flag may indicate whether the input picture is divided into multiple sub-regions. If the value of vps_sub_picture_dividing_flag is equal to 0, the input picture in the coded video sequence corresponding to the current VPS may not be divided into multiple sub-regions. In this case, the size of the input picture is equal to the coded picture size (pic_width_in_luma_samples, pic_height_in_luma_samples) signaled in the SPS. If the value of vps_sub_picture_dividing_flag is equal to 1, the input picture may be divided into multiple sub-regions. In this case, the syntax elements vps_full_pic_width_in_luma_samples and vps_full_pic_height_in_luma_samaples are signaled in the VPS. The values ​​of vps_full_pic_width_in_luma_samples and vps_full_pic_height_in_luma_samaples are equal to the width and height of the input picture, respectively.

[0139] In an embodiment, the values ​​of vps_full_pic_width_in_luma_samples and vps_full_pic_height_in_luma_samples may not be used for decoding, but may be used for synthesis and display.

[0140] In an embodiment, when the value of vps_sub_picture_dividing_flag is equal to 1, the syntax elements pic_offset_x and pic_offset_y may be signaled in the SPS corresponding to a specific layer. In this case, the size of the coded picture signaled in the SPS (pic_width_in_luma_samples, pic_height_in_luma_samples) is equal to the width and height of the sub-region corresponding to a specific layer. In addition, the position of the upper left corner of the sub-region (pic_offset_x, pic_offset_y) may be signaled in the SPS.

[0141] In an embodiment, the position information (pic_offset_x, pic_offset_y) of the top left corner of the sub-region may not be used for decoding, but may be used for synthesis and display.

[0142] In an embodiment, layout information (size and position) of all or a subset of subregions of an input picture, as well as inter-layer dependency information, may be signaled in a parameter set or an SEI message. Figure 17 shows an example of syntax elements indicating information about the layout of subregions, inter-layer dependencies, and the relationship between subregions and one or more layers. In this example, the syntax element num_sub_region indicates the number of (rectangular) subregions in the current coded video sequence. The syntax element num_layers indicates the number of layers in the current coded video sequence. The value of num_layers may be greater than or equal to the value of num_sub_region. If any subregion is coded as a single layer, the value of num_layers is equal to the value of num_sub_region. If one or more subregions are coded as multiple layers, the value of num_layers is greater than the value of num_sub_region. The syntax element direct_dependency_flag[i][j] indicates the dependency of the jth layer to the ith layer. num_layers_for_region[i] indicates the number of layers associated with the i-th subregion. sub_region_layer_id[i][j] indicates the layer_id of the j-th layer associated with the i-th subregion. sub_region_offset_x[i] and sub_region_offset_y[i] indicate the horizontal and vertical positions of the top left corner of the i-th subregion, respectively. sub_region_width[i] and sub_region_height[i] indicate the width and height of the i-th subregion, respectively.

[0143] In an embodiment, one or more syntax elements defining an output layer set to indicate one or more layers to be output with or without profile tier-level information may be signaled in a high-level syntax structure, such as a VPS, DPS, SPS, PPS, APS, or SEI message. With reference to Figure 18, a syntax element num_output_layer_sets indicating the number of output layer sets (OLS) in a coded video sequence that references a VPS may be signaled in the VPS. For each output layer set, output_layer_flag may be signaled as many times as the number of output layers.

[0144] In an embodiment, output_layer_flag equal to 1 may indicate that the i-th layer is output. Output_layer_flag equal to 0 may indicate that the i-th layer is not output.

[0145] In an embodiment, one or more syntax elements defining profile tier level information for each output layer set may be signaled in a high-level syntax structure, such as a VPS, DPS, SPS, PPS, APS, or SEI message. Still referring to Figure 18, a syntax element num_profile_tier_level indicating the number of profile tier level information per OLS in a coded video sequence that references a VPS may be signaled in the VPS. For each output layer set, an index indicating a particular profile tier level information among the set of syntax elements for profile tier level information or an entry within the profile tier level information may be signaled as many times as the number of output layers.

[0146] In an embodiment, profile_tier_level_idx[i][j] specifies the index into the list of profile_tier_level() syntax structures in the VPS of the profile_tier_level() syntax structure that applies to the jth layer of the ith OLS.

[0147] In an embodiment, referring to FIG. 19, the syntax elements num_profile_tile_level and / or num_output_layer_sets may be signaled if the number of maximum layers is greater than 1 (vps_max_layers_minus1>0).

[0148] In an embodiment, referring to FIG. 19, a syntax element vps_output_layers_mode[i] may be present in the VPS, indicating the mode of output layer signaling for the i-th output layer set.

[0149] In an embodiment, vps_output_layers_mode[i] equal to 0 may indicate that only the highest layer is output by the i-th output layer set. vps_output_layers_mode[i] equal to 1 may indicate that all layers are output by the i-th output layer set. vps_output_layers_mode[i] equal to 2 may indicate that the layer output by the i-th output layer set is the layer with vps_output_layer_flag[i][j] equal to 1. More values ​​may be reserved.

[0150] In an embodiment, output_layer_flag[i][j] may or may not be signaled depending on the value of vps_output_layers_mode[i] for the i-th output layer set.

[0151] In an embodiment, referring to Figure 19, a flag vps_ptl_flag[i] may be present for the i-th output layer set. Depending on the value of vps_ptl_flag[i], the profile tier level information of the i-th output layer set may or may not be signaled.

[0152] In an embodiment, referring to FIG. 20, the number of sub-pictures in the current CVS, max_subpics_minus1, may be signaled in a high-level syntax structure, for example, a VPS, DPS, SPS, PPS, APS, or SEI message.

[0153] In an embodiment, referring to FIG. 20, the sub-picture identifier sub_pic_id[i] of the ith sub-picture may be signaled if the number of sub-pictures is greater than 1 (max_subpics_minus1>0).

[0154] In an embodiment, one or more syntax elements indicating sub-picture identifiers belonging to each layer of each output layer set may be signaled in the VPS. Referring to Figure 20, sub_pic_id_layer[i][j][k] indicates the kth sub-picture present in the jth layer of the ith output layer set. With this information, a decoder may know which sub-pictures can be decoded and output for each layer of a particular output layer set.

[0155] In an embodiment, a picture header (PH) is a syntax structure that contains syntax elements that apply to all slices of a coded picture. A picture unit (PU) is a set of NAL units that are related to each other according to specific classification rules, are consecutive in decoding order, and contain exactly one coded picture. A PU may contain a picture header (PH) and one or more VCL NAL units that contain coded pictures.

[0156] In an embodiment, the SPS (RBSP) may be available to the decoding process before it is referenced, may be contained in at least one AU with TemporalID equal to 0, or may be supplied through external means.

[0157] In an embodiment, the SPS (RBSP) may be available to the decoding process before it is referenced, may be included in at least one AU with TemporalID equal to 0 in a CVS that contains one or more PPSs that reference the SPS, or may be supplied through external means.

[0158] In an embodiment, the SPS (RBSP) may be available to the decoding process before it is referenced by one or more PPSs, or may be included in at least one PU with nuh_layer_id equal to the smallest nuh_layer_id value of the PPS NAL unit that references the SPS in a CVS that contains one or more PPSs that reference the SPS, or may be supplied through external means.

[0159] In an embodiment, the SPS (RBSP) may be available to the decoding process before it is referenced by one or more PPSs, or may be included in at least one PU with TemporalID equal to 0 and nuh_layer_id equal to the minimum nuh_layer_id value of the PPS NAL units that reference the SPS NAL unit, or may be supplied through external means.

[0160] In an embodiment, the SPS (RBSP) may be available to the decoding process before it is referenced by one or more PPSs, or may be included in at least one PU with TemporalID equal to 0 and nuh_layer_id equal to the minimum nuh_layer_id value of the PPS NAL units that reference the SPS NAL unit in their CVS, or may be supplied through external means.

[0161] In the same or other embodiments, pps_seq_parameter_set_id may specify the value of sps_seq_parameter_set_id for the referenced SPS. The value of pps_seq_parameter_set_id may be the same for all PPSs referenced by coded pictures in a coded layer-wise video sequence (CLVS).

[0162] In the same or other embodiments, all SPS NAL units with a particular value of sps_seq_parameter_set_id in the CVS may have the same content.

[0163] In the same or other embodiments, regardless of the nuh_layer_id value, SPS NAL units may share the same value space for sps_seq_parameter_set_id.

[0164] In the same or other embodiments, the nuh_layer_id value of an SPS NAL unit may be equal to the smallest nuh_layer_id value of the PPS NAL units that reference that SPS NAL unit.

[0165] In an embodiment, when an SPS with nuh_layer_id equal to m is referenced by one or more PPSs with nuh_layer_id equal to n, the layer with nuh_layer_id equal to m may be the same as the (direct or indirect) reference layer of the layer with nuh_layer_id equal to n or the layer with nuh_layer_id equal to m.

[0166] In an embodiment, the PPS (RBSP) may be available to the decoding process before it is referenced, may be contained in at least one AU with a TemporalID equal to the TemporalID of the PPS NAL unit, or may be supplied through external means.

[0167] In an embodiment, the PPS (RBSP) may be available to the decoding process before it is referenced, may be included in at least one AU with a TemporalID equal to the TemporalID of the PPS NAL unit in a CVS containing one or more PHs (or coded slice NAL units) that reference the PPS, or may be supplied through external means.

[0168] In an embodiment, the PPS (RBSP) may be available to the decoding process before it is referenced by one or more PHs (or coded slice NAL units), may be included in at least one PU with nuh_layer_id equal to the smallest nuh_layer_id value of the coded slice NAL units that reference the PPS NAL unit in the CVS containing one or more PHs (or coded slice NAL units) that reference the PPS, or may be supplied through external means.

[0169] In an embodiment, the PPS (RBSP) may be available to the decoding process before it is referenced by one or more PHs (or coded slice NAL units), or may be included in at least one PU with nuh_layer_id equal to the smallest nuh_layer_id value of the PPS NAL units referencing the PPS NAL unit in a CVS containing one or more PHs (or coded slice NAL units) referencing the PPS and TemporalID equal to the TemporalID of the PPS NAL unit, or may be supplied through external means.

[0170] In the same or other embodiments, ph_pic_parameter_set_id in PH may specify the value of pps_pic_parameter_set_id for the referenced PPS in use. The value of pps_seq_parameter_set_id may be the same for all PPSs referenced by coded pictures in CLVS.

[0171] In the same or other embodiments, all PPS NAL units with a particular value of pps_pic_parameter_set_id within a PU may have the same content.

[0172] In the same or other embodiments, PPS NAL units may share the same value space for pps_pic_parameter_set_id regardless of the nuh_layer_id value.

[0173] In the same or other embodiments, the nuh_layer_id of a PPS NAL unit may be equal to the smallest nuh_layer_id value of the coded slice NAL units that reference the NAL units that reference that PPS NAL unit.

[0174] In an embodiment, when a PPS with nuh_layer_id equal to m is referenced by one or more coded slice NAL units with nuh_layer_id equal to n, the layer with nuh_layer_id equal to m may be the same as the (direct or indirect) reference layer of the layer with nuh_layer_id equal to n or the layer with nuh_layer_id equal to m.

[0175] In an embodiment, the PPS (RBSP) may be available to the decoding process before it is referenced, may be included in at least one AU with a TemporalID equal to the TemporalID of the PPS NAL unit in a CVS containing one or more PHs (or coded slice NAL units) that reference the PPS, or may be supplied through external means.

[0176] In an embodiment, the PPS (RBSP) may be available to the decoding process before it is referenced by one or more PHs (or coded slice NAL units), may be included in at least one PU with nuh_layer_id equal to the smallest nuh_layer_id value of the coded slice NAL units that reference the PPS NAL unit in the CVS containing one or more PHs (or coded slice NAL units) that reference the PPS, or may be supplied through external means.

[0177] In an embodiment, the PPS (RBSP) may be available to the decoding process before it is referenced by one or more PHs (or coded slice NAL units), or may be included in at least one PU with nuh_layer_id equal to the smallest nuh_layer_id value of the PPS NAL units referencing the PPS NAL unit in a CVS containing one or more PHs (or coded slice NAL units) referencing the PPS and TemporalID equal to the TemporalID of the PPS NAL unit, or may be supplied through external means.

[0178] In the same or other embodiments, ph_pic_parameter_set_id in PH may specify the value of pps_pic_parameter_set_id for the referenced PPS in use. The value of pps_seq_parameter_set_id may be the same for all PPSs referenced by coded pictures in CLVS.

[0179] In the same or other embodiments, all PPS NAL units with a particular value of pps_pic_parameter_set_id within a PU may have the same content.

[0180] In the same or other embodiments, PPS NAL units may share the same value space for pps_pic_parameter_set_id regardless of the nuh_layer_id value.

[0181] In the same or other embodiments, the nuh_layer_id of a PPS NAL unit may be equal to the smallest nuh_layer_id value of the coded slice NAL units that reference the NAL units that reference that PPS NAL unit.

[0182] In an embodiment, when a PPS with nuh_layer_id equal to m is referenced by one or more coded slice NAL units with nuh_layer_id equal to n, the layer with nuh_layer_id equal to m may be the same as the (direct or indirect) reference layer of the layer with nuh_layer_id equal to n or the layer with nuh_layer_id equal to m.

[0183] When a picture is encoded in a bitstream that includes one or more instances with different resolutions, each coded video sequence of a layer may use reference picture resampling when the reference picture may have a different resolution than the current picture. It is desirable to specify a syntax element that indicates reference picture resampling for spatial scalability or adaptive picture resolution change (ARC).

[0184] 21, an output layer may indicate a layer of an output layer set that is output. An output layer set (OLS) may indicate a set of layers that includes a specified set of layers, where one or more layers in the set of layers are designated to be output layers. An output layer set (OLS) layer index is an index of a layer in the OLS relative to the list of layers in the OLS.

[0185] A sub-layer may indicate a temporal scalable layer of a temporal scalable bitstream that contains VCL NAL units and associated non-VCL NAL units with a particular value of the TemporalID variable. A sub-layer representation may indicate a subset of a bitstream that contains NAL units of a particular sub-layer and lower sub-layers.

[0186] The VPS RBSP may be available to the decoding process before it is referenced, may be contained in at least one AU with TemporalID equal to 0, or may be supplied through external means. All VPS NAL units with a particular value of vps_video_parameter_set_id in the CVS may have the same content.

[0187] 22, in an embodiment, vps_video_parameter_set_id provides identification of the VPS for reference by other syntax elements. The value of vps_video_parameter_set_id may be greater than 0.

[0188] In an embodiment, vps_max_layers_minus1 plus 1 may specify the maximum number of layers allowed in each CVS that references the VPS.

[0189] vps_max_sublayers_minus1 plus 1 may specify the maximum number of temporal sublayers that may exist in a layer in each CVS that references the VPS. The value of vps_max_sublayers_minus1 plus 1 may be in the range 0 to 6, inclusive.

[0190] In embodiments, vps_all_layers_same_num_sublayers_flag equal to 1 may specify that the number of temporal sublayers is the same for all layers in each CVS that references the VPS. vps_all_layers_same_num_sublayers_flag equal to 0 may specify that layers in each CVS that references the VPS may or may not have the same number of temporal sublayers. If not present, the value of vps_all_layers_same_num_sublayers_flag may be inferred to be equal to 1.

[0191] In an embodiment, vps_all_independent_layers_flag equal to 1 may specify that all layers in the CVS are coded independently without using inter-layer prediction.

[0192] In an embodiment, vps_all_independent_layers_flag equal to 0 may specify that one or more of the layers in the CVS may use inter-layer prediction. If not present, vps_all_independent_layers_flag may be inferred to be equal to 1.

[0193] In an embodiment, vps_layer_id[i] may specify the nuh_layer_id value of the i-th layer. For any two non-negative integer values ​​of m and n, when m is less than n, the value of vps_layer_id[m] is less than vps_layer_id[n].

[0194] In an embodiment, vps_independent_layer_flag[i] equal to 1 may specify that the layer with index i does not use inter-layer prediction. vps_independent_layer_flag[i] equal to 0 may specify that the layer with index i may use inter-layer prediction and that the syntax element vps_direct_ref_layer_flag[i][j], for j in the range 0 to i-1, inclusive, is present in the VPS. If not present, the value of vps_independent_layer_flag[i] may be inferred to be equal to 1.

[0195] In an embodiment, vps_direct_ref_layer_flag[i][j] equal to 0 may specify that the layer with index j is not a direct reference layer for the layer with index i. vps_direct_ref_layer_flag[i][j] equal to 1 may specify that the layer with index j is a direct reference layer for the layer with index i. If vps_direct_ref_layer_flag[i][j] is not present for i and j in the range from 0 to vps_max_layers_minus1, inclusive, it may be inferred to be equal to 0. There may be at least one value of j in the range from 0 to i-1, inclusive, such that if vps_independent_layer_flag[i] is equal to 0, then the value of vps_direct_ref_layer_flag[i][j] is equal to 1.

[0196] The variables NumDirectRefLayers[i], DirectRefLayerIdx[i][d], NumRefLayers[i], RefLayerIdx[i][r], and LayerUsedAsRefLayerFlag[j] may be derived as follows:

number

[0197] The variable GeneralLayerIdx[i], which specifies the layer index of the layer with nuh_layer_id equal to vps_layer_id[i], may be derived as follows:

number

[0198] For any two different values ​​of i and j, both of which range from 0 to vps_max_layers_minus1, it may be a bitstream conformance requirement that when dependencyFlag[i][j] is equal to 1, the values ​​of chroma_fomart_idc and bit_depth_minus8 applied to the i-th layer are equal to the values ​​of chroma_fomart_idc and bit_depth_minus8 applied to the j-th layer, respectively.

[0199] A max_tid_ref_present_flag[i] equal to 1 may specify that the syntax element max_tid_il_ref_pics_plas1[i] is present. A max_tid_ref_present_flag[i] equal to 0 may specify that the syntax element max_tid_il_ref_pics_plas1[i] is not present.

[0200] max_tid_il_ref_pics_plus1[i] equal to 0 may specify that inter-layer prediction is not used by non-IRAP pictures of the i-th layer. max_tid_il_ref_pics_plus1[i] greater than 0 may specify that pictures with TemporalID greater than max_tid_il_ref_pics_plus1[i]-1 are not used as ILRPs to decode pictures of the i-th layer. If not present, the value of max_tid_il_ref_pics_plus1[i] may be inferred to be equal to 7.

[0201] each_layer_is_an_ols_flag equal to 1 may specify that each OLS contains only one layer, and each layer in the CVS that references the VPS is itself an OLS, with the one contained layer being the only output layer. each_layer_is_an_ols_flag equal to 0 may specify that an OLS may contain more than one layer. If vps_max_layers_minus1 is equal to 0, the value of each_layer_is_an_ols_flag may be inferred to be equal to 1. Otherwise, when vps_all_independent_layers_flag is equal to 0, the value of each_layer_is_an_ols_flag may be inferred to be equal to 0.

[0202] ols_mode_idc equal to 0 may specify that the total number of OLSs specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer indices 0 to i, and for each OLS, only the highest layer in the OLS is output.

[0203] ols_mode_idc equal to 1 may specify that the total number of OLSs specified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLS contains layers with layer indices 0 to i, and for each OLS, all layers in the OLS are output.

[0204] ols_mode_idc equal to 2 may specify that the total number of OLSs specified by the VPS is explicitly signaled, and for each OLS, the output layer is explicitly signaled, and other layers are layers that are direct or indirect reference layers of the output layer of the OLS.

[0205] The value of ols_mode_idc may range from 0 to 2 inclusive. The value 3 of ols_mode_idc is reserved for future use by ITU-T|ISO / IEC.

[0206] If vps_all_independent_layers_flag is equal to 1 and each_layer_is_an_ols_flag is equal to 0, the value of ols_mode_idc may be inferred to be equal to 2.

[0207] num_output_layer_sets_minus1 plus 1 may specify the total number of OLSs specified by the VPS when ols_mode_idc is equal to 2.

[0208] The variable TotalNumOlss that specifies the OLS specified by the VPS may be derived as follows:

number

[0209] ols_output_layer_flag[i][j] equal to 1 may specify that the layer with nuh_layer_id equal to vps_layer_id[j] is the output layer of the i-th OLS when ols_mode_idc is equal to 2. ols_output_layer_flag[i][j] equal to 0 may specify that the layer with nuh_layer_id equal to vps_layer_id[j] is not the output layer of the i-th OLS when ols_mode_idc is equal to 2.

[0210] The variable NumOutputLayersInOls[i] specifying the number of output layers in the ith OLS, the variable NumSubLayersInLayerInOLS[i][j] specifying the number of sublayers in the jth layer in the ith OLS, the variable OutputLayerIdInOls[i][j] specifying the nuh_layer_id value of the jth output layer in the ith OLS, and the variable LayerUsedAsOutputLayerFlag[k] specifying whether the kth layer is used as an output layer in at least one OLS may be derived as follows:

number

[0211] For each value of i in the range 0 to vps_max_layers_minus1, inclusive, the values ​​of LayerUsedAsRefLayerFlag[i] and LayerUsedAsOutputLayerFlag[i] may not both be equal to 0. That is, there cannot be a layer that is not an output layer of at least one OLS or a direct reference layer of some other layer.

[0212] For each OLS, there may be at least one layer that is an output layer, i.e., for any value of i in the range 0 to TotalNumOlss-1, inclusive, the value of NumOutputLayersInOls[i] may be 0 or greater.

[0213] The variable NumLayersInOls[i], which specifies the number of layers in the i-th OLS, and the variable LayerIdInOls[i][j], which specifies the nuh_layer_id value of the j-th layer in the i-th OLS, may be derived as follows:

number

[0214] The variable OlsLayerIdx[i][j], which specifies the OLS layer index of the layer with nuh_layer_id equal to LayerIdInOls[i][j], is derived as follows:

[0215] The bottom layer in each OLS may be an independent layer, i.e., for each i in the range 0 to TotalNumOlss-1, inclusive, the value of vps_independent_layer_flag[GeneralLayerIdx[LayerIdInOls[i][j]]] is equal to 1.

[0216] Each layer may be included in at least one OLS specified by the VPS. That is, for each layer with a particular value of nuh_layer_id, nuhLayerId, equal to one of vps_layer_id[k], for k ranging from 0 to vps_max_layers_minus1, inclusive, there may be at least one pair of values ​​of i and j, where i ranges from 0 to TotalNumOlss-1, inclusive, and j ranges from 0 to NumLayersInOls[i]-1, inclusive, such that the value of LayerIdInOls[i][j] is equal to nuhLayerId.

[0217] In an embodiment, the decoding process may operate as follows for the current picture CuttPic: - PictureOutputFlag may be set as follows: - PictureOutputFlag may be set equal to 0 if one of the following conditions is true: - The current picture is an RASL and the associated IRAP picture's NoOutputBeforeRecoveryFlag is equal to 1. - gdr_enabled_flag is equal to 1 and the current picture is a GDR picture with NoOutputBeforeRecoveryFlag equal to 1. - gdr_enabled_flag is equal to 1, the current picture is associated with a GDR picture that has NoOutputBeforeRecoveryFlag equal to 1, and the current picture's PicOrderCntVal is less than the associated GDR picture's RpPicOrderCntVal. - sps_video_parameter_set_id is greater than 0, ols_mode_idc is equal to 0, and the current AU contains a picture PicA that satisfies all of the following conditions: - PicA has PictureOutputFlag equal to 1. - PicA has a nuh_layer_id nuhLid that is greater than that of the current picture. - PicA belongs to the output layer of OLS (i.e., OutputLayerIdInOls[TargetOlsIdx][0] is equal to nuhLid). - sps_video_parameter_set_id is greater than 0, ols_mode_idc is equal to 2, and ols_output_layer_flag[TargetOlsIdx][GeneralLayerIdx[nuh_layer_id]] is equal to 0. If no condition is true, PictureOutputFlag may be set equal to pic_output_flag.

[0218] After all slices of the current picture are decoded, the current decoded picture is marked as "used for short-term reference", and each ILRP entry in RefPicList[0] or RefPicList[1] is marked as "used for short-term reference".

[0219] In an embodiment, if each layer is an output layer set, PictureOutputFlag may be set equal to pic_output_flag regardless of the value of ols_mode_idc.

[0220] In an embodiment, PictureOutputFlag is set when sps_video_parameter_set_id is greater than 0, each_layer_is_an_ols_flag is equal to 0, ols_mode_idc is equal to 0, and the current AU satisfies the following conditions: PicA has PictureOutputFlag equal to 1, PicA has a nuh_layer_id nuhLid greater than that of the current picture, PicA belongs to the output layer of OLS (i.e., OutputLayerIdInOls[TargetOlsIdx][0] is equal to nuhLid). It may be set equal to 0 if it contains a picture PicA that satisfies all of the above.

[0221] In an embodiment, PictureOutputFlag may be set equal to 0 if sps_video_parameter_set_id is greater than 0, each_layer_is_an_ols_flag is equal to 0, ols_mode_idc is equal to 2, and ols_output_layer_flag[TargetOlsIdx][GeneralLayerIdx[nuh_layer_id]] is equal to 0.

[0222] Reference picture resampling may enable adaptive resolution changes within a coded (layered) video sequence and spatial scalability across layers with dependencies between layers belonging to the same output layer set.

[0223] In an embodiment, as shown in Figure 23, sps_ref_pic_resampling_enabled_flag is signaled in a parameter set (e.g., a sequence parameter set). The flag sps_ref_pic_resampling_enabled_flag may indicate whether reference picture resampling is used for adaptive resolution changes in a coded video sequence that references an SPS or for spatial scalability across layers. sps_ref_pic_resampling_enabled_flag equal to 1 may specify that reference picture resampling is enabled and that one or more slices of a picture in a CLVS reference a reference picture with a different spatial resolution in the active entry of the reference picture list. sps_ref_pic_resampling_enabled_flag equal to 0 may specify that reference picture resampling is disabled and that slices of a picture in a CLVS do not reference a reference picture with a different spatial resolution in the active entry of the reference picture list.

[0224] In an embodiment, if sps_ref_pic_resampling_enabled_flag is equal to 1, for the current picture, the reference pictures with different spatial resolutions belong to either the same layer as the layer containing the current picture or a different layer.

[0225] In other embodiments, sps_ref_pic_resampling_enabled_flag equal to 1 may specify that reference picture resampling is enabled and that one or more slices of a picture in the CLVS reference a reference picture with a different spatial resolution or a different scaling window in the active entry of the reference picture list. sps_ref_pic_resampling_enabled_flag equal to 0 may specify that reference picture resampling is disabled and that no slices of a picture in the CLVS reference a reference picture with a different spatial resolution or a different scaling window in the active entry of the reference picture list.

[0226] In an embodiment, if sps_ref_pic_resampling_enabled_flag is equal to 1, for the current picture, the reference pictures with different spatial resolutions or different scaling windows belong to either the same layer as the layer containing the current picture or a different layer.

[0227] In an embodiment, sps_res_change_in_clvs_allowed_flag may indicate whether picture resolution may change within a CLVS or a CVS. sps_res_change_in_clvs_allowed_flag equal to 1 may specify that picture spatial resolution may change within a CLVS that references an SPS. sps_res_change_in_clvs_allowed_flag equal to 0 may specify that picture spatial resolution may not change within any CLVS that references an SPS. If not present, the value of sps_res_change_in_clvs_allowed_flag may be inferred to be equal to 0.

[0228] In an embodiment, if sps_ref_pic_resampling_enabled_flag is equal to 1 and sps_res_change_in_clvs_allowed_flag is equal to 0, reference picture resampling is used only for spatial scalability and cannot be used for adaptive resolution change in CLVS.

[0229] In an embodiment, if sps_ref_pic_resampling_enabled_flag is equal to 1 and sps_res_change_in_clvs_allowed_flag is equal to 1, reference picture resampling may be used for both spatial scalability and adaptive resolution change in CLVS.

[0230] pps_scaling_window_explicit_signalling_flag is equal to 1 if sps_ref_pic_resampling_enabled_flag is equal to 1, sps_res_change_in_clvs_allowed_flag is equal to 0, and sps_video_parameter_set_id is equal to 0. It means that when the picture resolution is constant in CLVS or CVS and reference picture resampling is used, the scaling window parameters need to be explicitly signaled instead of inferring the values ​​from the adaptation window parameters.

[0231] In an embodiment, the sps_virtual_boundaries_present_flag is signaled in the SPS as shown in Figure 23. The flag sps_virtual_boundaries_present_flag may indicate whether virtual boundary information is signaled in the SPS.

[0232] In an embodiment, sps_virtual_boundaries_present_flag is conditionally signaled only if sps_res_change_in_clvs_allowed_flag is equal to 0. This is because when reference picture resampling is used, virtual boundary information may not be signaled in the SPS.

[0233] In an embodiment, sps_virtual_boundaries_present_flag equal to 1 may specify that virtual boundary information is signaled in the SPS. sps_virtual_boundaries_present_flag equal to 0 may specify that virtual boundary information is not signaled in the SPS. When there is one or more virtual boundaries signaled in the SPS, in-loop filtering operations are disabled between the virtual boundaries in pictures that reference the SPS. In-loop filtering operations include deblocking filters, sample adaptive offset filters, and adaptive loop filter operations. If not present, the value of sps_virtual_boundaries_present_flag may be inferred to be equal to 0.

[0234] In an embodiment, the sps_subpic_info_present_flag is signaled in the SPS, as shown in Figure 23. The flag sps_subpic_info_present_flag may indicate whether the sub-picture partitioning information is signaled in the SPS.

[0235] In an embodiment, sps_subpic_info_present_flag is conditionally signaled only if sps_res_change_in_clvs_allowed_flag is equal to 0. This is because subpicture partitioning information may not be signaled in the SPS when reference picture resampling is used.

[0236] In an embodiment, sps_subpic_info_present_flag equal to 1 may specify that subpicture information is present for the CLVS and that there may be one or more subpictures for each picture in the CLVS. sps_subpic_info_present_flag equal to 0 may specify that subpicture information is not present for the CLVS and that there is only one subpicture for each picture in the CLVS. If not present, the value of sps_subpic_info_present_flag may be inferred to be equal to 0.

[0237] In an embodiment, pps_res_change_in_clvs_allowed_flag may be signaled in the PPS as shown in Figure 24. The value of pps_res_change_in_clvs_allowed_flag in the PPS may be equal to the value of sps_res_change_in_clvs_allowed_flag in the SPS that the PPS references.

[0238] In an embodiment, picture width and height information may be signaled in the PPS only if pps_res_change_in_clvs_allowed_flag is equal to 1. If pps_res_change_in_clvs_allowed_flag is equal to 0, the picture width and height values ​​are inferred to be equal to the maximum picture width and height values ​​signaled in the SPS.

[0239] In an embodiment, pps_pic_width_in_luma_samples may specify the width of each decoded picture referring to the PPS in units of luma samples. pps_pic_width_in_luma_samples cannot be equal to 0, should be an integer multiple of Max(8,MinCbSizeY), and should be less than or equal to sps_pic_width_max_in_luma_samples. If not present, the value of pps_pic_width_in_luma_samples may be inferred to be equal to sps_pic_width_max_in_luma_samples. When sps_ref_wraparound_enabled_flag is equal to 1, the value of (CtbSizeY / MinCbSizeY+1) should be less than or equal to the value of (pps_pic_width_in_luma_samples / MinCbSizeY-1). pps_pic_height_in_luma_samples may specify the height of each decoded picture referencing the PPS in units of luma samples. pps_pic_height_in_luma_samples cannot be equal to 0, should be an integer multiple of Max(8,MinCbSizeY), and should be less than or equal to sps_pic_height_max_in_luma_samples. If not present, the value of pps_pic_height_in_luma_samples may be inferred to be equal to sps_pic_height_max_in_luma_samples.

[0240] 25A-25C are flowcharts illustrating example processes 2500A, 2500B, and 2500C for decoding an encoded video bitstream. In some implementations, one or more process blocks of FIGS. 25A-25C may be performed by decoder 210. In some implementations, one or more process blocks of FIGS. 25A-25C may be performed by another device or group of devices separate from or including decoder 210, such as encoder 203.

[0241] 25A, process 2500A may include obtaining a first flag from an encoded video bitstream indicating that reference picture resampling is enabled for a coded video sequence (CVS) (block 2511). In an embodiment, the first flag may correspond to sps_ref_pic_resampling_enabled_flag.

[0242] 25A, the process 2500A may include determining a value of a second flag indicating whether the picture resolution is changed in the CVS (block 2512). In an embodiment, the second flag may correspond to sps_res_change_in_clvs_allowed_flag.

[0243] As further shown in FIG. 25A, the process 2500A may include determining whether the value of the second flag indicates whether the picture resolution is changed in the CVS (block 2513).

[0244] As further shown in FIG. 25A, process 2500A may include decoding the CVS using reference picture resampling for spatial scalability and adaptive resolution change (ARC) (block 2515) based on the value of a second flag indicating that the picture resolution is changed in the CVS (YES at block 2513).

[0245] 25B, process 2500B may include determining whether the value of the second flag indicates whether the picture resolution is changed in the CVS (block 2523). In an embodiment, block 2523 of process 2500B may correspond to block 2513 of process 2500A.

[0246] 25B, process 2500B may include obtaining a third flag indicating whether virtual boundary information is signaled (block 2525) based on the value of the second flag indicating that the picture resolution is not changed in CVS (NO at block 2523). In an embodiment, the third flag may correspond to sps_virtual_boundaries_present_flag.

[0247] As further shown in FIG. 25B, process 2500B may include that based on the value of the second flag indicating that the picture resolution is changed in CVS (YES at block 2523), the third flag may not be signaled (block 2524).

[0248] 25C, process 2500C may include determining whether the value of the second flag indicates whether the picture resolution is changed in CVS (block 2533). In an embodiment, block 2533 of process 2500C may correspond to block 2513 of process 2500A.

[0249] 25C, process 2500C may include obtaining a fourth flag indicating whether subpicture partitioning information is signaled (block 2535) based on the value of the second flag indicating that the picture resolution is not changed in the CVS (NO at block 2533). In an embodiment, the fourth flag may correspond to sps_subpic_info_present_flag.

[0250] As further shown in FIG. 25C, process 2500C may include that based on the value of the second flag indicating that the picture resolution is changed in CVS (YES at block 2533), the fourth flag may not be signaled (block 2534).

[0251] In embodiments, one or more blocks of processes 2500A, 2500B, and 2500C may be combined in any order. Additionally, although Figures 25A-25C illustrate example blocks of processes 2500A, 2500B, and 2500C, in some implementations, processes 2500A, 2500B, and 2500C may include additional, fewer, different, or otherwise arranged blocks compared to those depicted in Figures 25A-25C. Additionally, or alternatively, two or more of the blocks of processes 2500A, 2500B, and 2500C may be performed in parallel.

[0252] Furthermore, the proposed methods may be implemented by processing circuitry (e.g., one or more processors or one or more integrated circuits). In one example, one or more processors execute a program stored on a non-transitory computer-readable medium to perform one or more of the proposed methods.

[0253] The techniques described above can be implemented as computer software using computer-readable instructions and physically stored on one or more computer-readable media. For example, Figure 26 illustrates a computer system 2600 suitable for implementing certain embodiments of the disclosed subject matter.

[0254] Computer software can be coded in any suitable machine code or computer language that can be subjected to mechanisms such as assembly, compilation, linking, etc. to produce code containing instructions that can be executed by a central processing unit (CPU), graphics processing unit (GPU), etc. directly or through interpretation, microcode execution, etc.

[0255] The instructions may be executable by various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smartphones, gaming consoles, devices for the Internet of Things, and the like.

[0256] 26 for computer system 2600 are exemplary in nature and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing embodiments of the present disclosure. The arrangement of components should not be interpreted as having any dependency or requirement regarding any one or combination of components illustrated in the exemplary embodiment of computer system 2600.

[0257] The computer system 2600 may include certain human interface input devices. Such human interface input devices may respond to input by one or more users through, for example, tactile input (e.g., keyboard, swipe, data glove manipulation), audio input (e.g., voice, claps), visual input (e.g., gestures), or olfactory input (not shown). The human interface devices may also be used to capture certain media that are not necessarily directly related to conscious human input, such as audio (e.g., speech, music, ambient sounds), images (e.g., scanned images, photographic images obtained from a still camera), and video (e.g., two-dimensional video, three-dimensional video, including stereoscopic video).

[0258] Input human interface devices may include one or more (only one of each shown) of a keyboard 2601, a mouse 2602, a trackpad 2603, a touchscreen 2610 and associated graphics adapters, a data glove, a joystick 2605, a microphone 2606, a scanner 2607, and a camera 2608.

[0259] The computer system 2600 may also include certain human interface output devices. Such human interface output devices may stimulate one or more of the user's senses, for example, through tactile output, sound, light, and smell / taste. Such human interface output devices may include haptic output devices (e.g., haptic feedback via a touchscreen 2610, data gloves, or joystick 2605; however, haptic feedback devices that do not function as input devices may also be present). For example, such devices may include audio output devices (e.g., speakers 2609, headphones (not shown)), visual output devices (e.g., screen 2610 including CRT screens, LCD screens, plasma screens, and OLED screens, each with or without touchscreen input capability, each with or without haptic feedback capability, some of which may output two-dimensional visual output or output in more than three dimensions, such as by means of stereoscopic output, virtual reality glasses (not shown), holographic displays, and smoke tanks (not shown)), and printers (not shown).

[0260] The computer system 2600 may also include human-accessible storage devices and their associated media, such as CD / DVD ROM / RW 2620 along with CD / DVD or similar media 2621, thumb drives 2622, removable hard disks or solid state drives 2623, legacy magnetic media such as tape and floppy disks (not shown), dedicated ROM / ASIC / PLD-based devices such as security dongles (not shown), and the like.

[0261] Those skilled in the art will also understand that the term "computer-readable medium" as used in connection with the presently disclosed subject matter does not include transmission media, carrier waves, or other transitory signals.

[0262] The computer system 2600 may also include interfaces to one or more communications networks. Networks may be, for example, wireless, wireline, or optical. Networks may further be local, wide-area, metropolitan, vehicular, and industrial, real-time, delay-tolerant, and the like. Examples of networks include local area networks such as Ethernet; wireless LANs; cellular networks including GSM, 3G, 4G, 5G, LTE, and the like; TV wireline or wireless wide-area digital networks including cable TV, satellite TV, and terrestrial broadcast TV; and vehicle and factory networks including CAN bus. Particular networks generally require an external network interface adapter 2654 attached to a particular general-purpose digital port or peripheral bus 2649 (e.g., a USB port on the computer system 2600). Others are generally integrated into the core of the computer system 2600 by attachment to a system bus as described below (e.g., an Ethernet network interface to a PC computer system or a cellular network interface to a smartphone computer system). As an example, network 2655 may be connected to peripheral bus 2649 using network interface 2654. Using any of these networks, computer system 2600 can communicate with other entities. Such communication can be unidirectional receive-only (e.g., broadcast TV) or unidirectional transmit-only (e.g., a CAN bus to a specific CAN bus device), or can be bidirectional to other computer systems using, for example, a local or wide-area digital network. Specific protocols or protocol stacks can be used with each of the networks and network interface 2654, as described above.

[0263] The above-mentioned human interface devices, human-accessible storage devices, and network interfaces may be attached to the core 2640 of the computer system 2600.

[0264] The core 2640 may include one or more central processing units (CPUs) 2641, graphics processing units (GPUs) 2642, dedicated programmable processing units in the form of field programmable gate arrays (FPGAs) 2643, hardware accelerators 2644 for specific tasks, etc. These devices may be connected through a system bus 2648, along with read-only memory (ROM) 2645, random access memory (RAM) 2646, internal mass storage devices such as internal non-user-accessible hard drives, SSDs, etc. 2647. In some computer systems, the system bus 2648 may be accessible in the form of one or more physical plugs, allowing expansion with additional CPUs, GPUs, etc. Peripheral devices may be attached to the core's system bus 2648 directly or through a peripheral bus 2649. Architectures for peripheral buses include Peripheral Component Interconnect (PCI), USB, etc.

[0265] The CPU 2641, GPU 2642, FPGA 2643, and accelerator 2644 can execute specific instructions that, in combination, can constitute the above-mentioned computer code. The computer code can be stored in ROM 2645 or RAM 2646. Temporary data can also be stored in RAM 2646, while persistent data can be stored, for example, in an internal mass storage device 2647. Fast storage and retrieval from any of the memory devices can be enabled through the use of cache memory. The cache memory can be closely associated with one or more of the CPU 2641, GPU 2642, mass storage device 2647, ROM 2645, RAM 2646, etc.

[0266] The computer-readable medium can carry computer code for performing various computer-implemented operations. The medium and computer code can be those specially designed and constructed for the purposes of the present disclosure, or they can be of the kind well known and available to those of ordinary skill in the computer software arts.

[0267] By way of example, and not limitation, a computer system having architecture 2600, and specifically core 2640, can provide functionality as a result of a processor (including a CPU, GPU, FPGA, accelerator, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media can be media associated with the user-accessible mass storage devices introduced above, in addition to specific storage of core 2640 that is non-transitory in nature, such as core internal mass storage 2647 or ROM 2645. Software implementing various embodiments of the present disclosure can be stored on such devices and executable by core 2640. Computer-readable media can include one or more memory devices or chips, depending on particular needs. The software can cause core 2640, and specifically the processor therein (including a CPU, GPU, FPGA, etc.), to perform particular processes or particular portions of particular processes described herein, including defining data structures stored in RAM 2646 and modifying such data structures according to software-defined processes. Additionally, or alternatively, a computer system may provide functionality as a result of logic (e.g., accelerator 2644) implemented by hardware or otherwise embodied in circuitry that can operate in place of or in conjunction with software to perform particular processes or portions of particular processes described herein. References to software can encompass logic, where appropriate, and vice versa. References to computer-readable media can encompass circuitry (e.g., integrated circuits (ICs)) storing software for execution, circuitry embodying logic for execution, or both, where appropriate. The present disclosure encompasses any suitable combination of hardware and software.

[0268] While this disclosure has described several example embodiments, there are alterations, permutations, and various substitute equivalents that fall within the scope of this disclosure. It will thus be apparent to those skilled in the art that numerous systems and methods will be possible which embody the principles of the present disclosure and are therefore within its spirit and scope, even if not explicitly shown or described herein.

Claims

1. 1. A video encoding method executed by at least one processor, comprising: A method for encoding a video sequence to generate a coded video sequence (CVS), the CVS including one or more CLVSs each corresponding to a layer of the CVS, the generating of the CVS comprising: generating a first flag sps_ref_pic_resampling_enabled_flag indicating whether reference picture resampling (RPR) is enabled between the layers or within each CLVS when generating the CLVS, and setting the first flag sps_ref_pic_resampling_enabled_flag to a true value to enable the reference picture resampling, whereby the current picture has a different scaling window than the reference picture, or a different spatial resolution and a different scaling window than the reference picture. A method comprising:

2. By setting the first flag sps_ref_pic_resampling_enabled_flag to a false value, the RPR is disabled between the layers and within each CLVS, the spatial resolution is not changed, and no scaling window is applied. The method of claim 1.

3. The method further comprises the step of generating a second flag sps_res_change_in_clvs_allowed_flag indicating whether a change in spatial resolution is allowed in each CLVS; By setting the first flag sps_ref_pic_resampling_enabled_flag to a true value and the second flag sps_res_change_in_clvs_allowed_flag to a false value, the change of spatial resolution is not allowed in the CLVS, but the change of spatial resolution is allowed in the CVS. The method of claim 1.

4. and generating a third flag pps_scaling_window_explicit_signalling_flag indicating that a scaling window parameter is explicitly signaled, wherein the third flag pps_scaling_window_explicit_signalling_flag is set to 1 when the first flag sps_ref_pic_resampling_enabled_flag is set to a true value and the second flag sps_res_change_in_clvs_allowed_flag is set to a false value. The method of claim 3.

5. A video encoding device configured to perform the method according to any one of claims 1 to 4.

6. A computer program which, when executed on a computer, causes the computer to carry out the method according to any one of claims 1 to 4.

7. 1. A video encoding method executed by at least one processor, comprising: generating a bitstream by performing a step for video encoding, and storing the bitstream, wherein the step for video encoding includes: A method for encoding a video sequence to generate a coded video sequence (CVS), the CVS including one or more CLVSs each corresponding to a layer of the CVS, the generating of the CVS comprising: generating a first flag sps_ref_pic_resampling_enabled_flag indicating whether reference picture resampling (RPR) is enabled between the layers or within each CLVS when generating the CLVS, and setting the first flag sps_ref_pic_resampling_enabled_flag to a true value to enable the reference picture resampling, whereby the current picture has a different scaling window than the reference picture, or a different spatial resolution and a different scaling window than the reference picture. A method comprising:

8. 1. A video decoding method executed by at least one processor, comprising: A method for decoding a coded video sequence (CVS) included in a bitstream, the CVS including one or more CLVSs each corresponding to a layer of the CVS, the step of decoding the CVS including: obtaining a first flag sps_ref_pic_resampling_enabled_flag from the bitstream, the first flag indicating whether reference picture resampling (RPR) is enabled between the layers or within each CLVS, wherein the first flag sps_ref_pic_resampling_enabled_flag is true to enable the reference picture resampling, so that the current picture has a different scaling window than a reference picture, or has a different spatial resolution and a different scaling window than the reference picture; A method comprising:

9. When the first flag sps_ref_pic_resampling_enabled_flag is a false value, the RPR between the layers and within each CLVS is disabled, the spatial resolution is not changed, and a scaling window is not applied. The method of claim 8.

10. A step of obtaining a second flag sps_res_change_in_clvs_allowed_flag from the bitstream, which indicates whether a change in spatial resolution is allowed in each CLVS, and the first flag sps_ref_pic_resampling_enabled_flag is true and the second flag sps_res_change_in_clvs_allowed_flag is false, so that a change in spatial resolution is not allowed in the CLVS but is allowed in the CVS. The method of claim 8.

Images