Techniques for bitstream extraction for subpicture in coded video stream

Abstract

To provide a method, computer program and computer system for video coding.SOLUTION: Video data having one or more subpictures is received. Resampling parameters and spatial scalability parameters corresponding to the subpictures are extracted. The resampling and spatial scalability parameters correspond to one or more flags signaled in a parameter set associated with the video data. The video data is decoded based on the extracted resampling and spatial scalability parameters.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority from U.S. Provisional Patent Application No. 63 / 037,202 (filed June 10, 2020) and U.S. Patent Application No. 17 / 335600 (filed June 1, 2021) in the U.S. Patent and Trademark Office, both of which are incorporated herein by reference in their entireties.

[0002] TECHNICAL FIELD This disclosure relates generally to the field of data processing, and more particularly to video coding. [Background technology]

[0003] Video encoding and decoding using inter-picture prediction with motion compensation has been known for decades. Uncompressed digital video can consist of a sequence of images, each with spatial dimensions of, for example, 1920x1080 luminance samples and associated chrominance samples. The sequence of images can have a fixed or variable frame rate (also informally called the frame rate), for example, 60 frames per second or 60 Hz. Uncompressed video has significant bitrate requirements. For example, 1080p60 4:2:0 video with 8 bits per sample (1920x1080 luminance sample resolution at a 60 Hz frame rate) requires a bandwidth approaching 1.5 Gbit / s. One hour of such video requires more than 600 gigabytes of storage space.

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

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

[0006] Historically, video encoders and decoders have tended to operate with a given picture size, most often defined for a coded video sequence (CVS), group of pictures (GOP), or similar multi-picture time frame. For example, in MPEG-2, system designs have been known to change horizontal resolution (and therefore picture size) depending on factors such as scene activity, but only in I-pictures, and thus typically for GOPs. Resampling reference images to use different resolutions in a CVS is known, for example from ITU-T Rec. H.263 Annex P. However, here the picture size is not changed; only the reference image is resampled, resulting in either only a portion of the image 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 individual macroblocks to be resampled upward or downward by a factor of two (in each dimension). Again, the picture size remains the same. The macroblock size is fixed in H.263 and does not need to be signaled.

[0007] In modern video coding, image resizing in predicted images has become mainstream. For example, VP9 allows for resampling of reference images and changing the resolution of the entire image. Similarly, certain proposals made for VVC (including, for example, Hendry et al., "On adaptive resolution change (ARC) for VVC," Joint Video Team document JVET-M0135-v1, January 9-19, 2019, which is incorporated herein in its entirety) allow for resampling of the entire reference image to a different resolution (either higher or lower). This document proposes that different candidate resolutions be coded in the sequence parameter set and referenced by per-image syntax elements in the picture parameter set. Summary of the Invention [Means for solving the problem]

[0008] Embodiments relate to methods, systems, and computer-readable media for video encoding. According to one aspect, a method for video encoding is provided. The method may include receiving video data having one or more sub-images. Re-sampling parameters and spatial scalability parameters corresponding to the sub-images are extracted. The re-sampling and spatial scalability parameters correspond to one or more flags signaled in a parameter set associated with the video data. The video data is decoded based on the extracted re-sampling and spatial scalability parameters.

[0009] According to another aspect, a computer system for video encoding is provided. The computer system may include one or more processors, one or more computer-readable memories, one or more computer-readable tangible storage devices, and program instructions stored in at least one of the one or more storage devices for execution by at least one of the one or more processors via at least one of the one or more memories, thereby enabling the computer system to perform a method. The method may include receiving video data having one or more sub-images. Re-sampling parameters and spatial scalability parameters corresponding to the sub-images are extracted. The re-sampling and spatial scalability parameters correspond to one or more flags signaled in a parameter set associated with the video data. The video data is decoded based on the extracted re-sampling and spatial scalability parameters.

[0010] According to yet another aspect, a computer-readable medium for video encoding is provided. The computer-readable medium may include one or more computer-readable storage devices and program instructions stored in at least one of the one or more tangible storage devices, the program instructions being executable by a processor. The program instructions are executable by the processor to perform a method that may optionally include receiving video data having one or more sub-images. Resampling parameters and spatial scalability parameters corresponding to the sub-images are extracted. The resampling and spatial scalability parameters correspond to one or more flags signaled in a parameter set associated with the video data. The video data is decoded based on the extracted resampling and spatial scalability parameters.

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

[0012] [Figure 1] FIG. 1 is a schematic diagram of a simplified block diagram of a communication system according to one embodiment. [Figure 2] FIG. 1 is a schematic diagram of a simplified block diagram of a communication system according to one embodiment. [Figure 3] FIG. 2 is a schematic diagram of a simplified block diagram of a decoder according to one embodiment. [Figure 4] FIG. 2 is a schematic diagram of a simplified block diagram of an encoder according to one embodiment. [Figure 5] As shown, there is a schematic diagram of options for signaling ARC parameters according to one embodiment. [Figure 6] 1 is an example of a syntax table according to one embodiment. [Figure 7] 1 is a schematic diagram of a computer system according to one embodiment. [Figure 8] 1 is an example of a prediction structure for scalability by adaptive resolution change. [Figure 9] 1 is an example of a syntax table according to one embodiment. [Figure 10] FIG. 10 is a simplified block diagram schematic of parsing and decoding poc cycles per access unit and access unit count values. [Figure 11] 1 is a schematic diagram of a video bitstream structure containing multi-layer sub-pictures. [Figure 12] FIG. 10 is a schematic diagram of displaying a selected sub-image with increased resolution. [Figure 13] FIG. 1 is a block diagram of a decoding and display process for a video bitstream containing multi-layer sub-pictures. [Figure 14] Schematic diagram of a 360-degree video display using sub-image enhancement layers. [Figure 15] 1 is an example of sub-image layout information and corresponding layer and image prediction structures. [Figure 16] 10 is an example of sub-picture layout information and corresponding layer and picture prediction structure with local region spatial scalability modality. [Figure 17] 10 is an example of a syntax table for sub-image layout information. [Figure 18] 10 is an example of a syntax table for an SEI message about sub-image layout information. [Figure 19] 10 is an example syntax table showing the output layer and profile / tier / level information for each output layer set. [Figure 20] 10 is an example syntax table showing that output layer mode is on for each output layer set. [Figure 21]An example syntax table showing the current subimage of each layer for each output layer set. [Figure 22] 10 is an example of a syntax table for a video parameter set RBSP. [Figure 23] 10 is an example of a syntax table showing an output layer set in output layer set mode. [Figure 24] 10 is an example of a syntax table showing resampling and resolution changes of reference images within a coded video sequence in SPS. [Figure 25] This is an example of a syntax table showing image sizes in PPS. [Figure 26] This is an example of inter-prediction within the same layer and inter-layer prediction with reference image resampling using a scaling window. [Figure 27] An example of sub-image sub-bitstream extraction with scaling window resizing. [Figure 28] This is an example of extracting a sub-bitstream of a sub-image using only an offset shift, without scaling or resizing the window. DETAILED DESCRIPTION OF THE INVENTION

[0013] Although detailed embodiments of the claimed structures and methods are disclosed herein, it can be understood that the disclosed embodiments are merely exemplary of the claimed structures and methods, which may be embodied in various forms. However, these structures and methods may be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. In the description, details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the presented embodiments.

[0014] Embodiments relate generally to the field of data processing, and more particularly to video coding. The exemplary embodiments described below provide, among other things, systems, methods, and computer programs for sub-image bitstream extraction in coded video streams having multiple layers. Accordingly, some embodiments are capable of improving the field of computing by enabling improved video encoding and decoding based on reference image resampling and spatial scalability parameter signaling in the video bitstream.

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

[0016] FIG. 1 shows a simplified block diagram of a communication system (100) according to one embodiment of the present disclosure. The system (100) may include at least two terminals (110-120) interconnected via a network (150). In a one-way data transmission scenario, a first terminal (110) may locally encode video data 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 encoded data, and display the decoded video data. One-way data transmission may be common in media serving applications, for example.

[0017] 1 illustrates a second pair of terminals (130, 140) provided to support bidirectional transmission of encoded video, such as might occur during a video conference. For bidirectional transmission of data, each terminal (130, 140) can encode video data captured at its local location for transmission to the other terminal over the network (150). Each terminal (130, 140) can also receive encoded video data transmitted by the other terminal, decode the encoded data, and display the decoded video data on a local display device.

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

[0019] Figure 2 illustrates the placement of a video encoder and decoder in a streaming environment as an example of an application of the disclosed subject matter. The disclosed subject matter is equally applicable to other video-enabled applications, including, for example, video conferencing, digital television, and storage of compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0020] The streaming system may include a video source (201), such as a capture subsystem (213), which may include a digital camera, generating an uncompressed video sample stream (202). The sample stream (202), depicted in bold to emphasize its large amount of data compared to an encoded video bitstream, may be processed by an encoder (203) coupled to the camera (201). The encoder (203) may include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter, as described in more detail below. The encoded video bitstream (204), depicted in thin to emphasize its small amount of data 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 copies (207, 209) of the encoded video bitstream (204). The client (206) may include a video decoder (210) that decodes an incoming copy of the encoded video bitstream (207) and creates an outgoing video sample stream (211) that can be rendered on a display (212) or other rendering device (not shown). In some streaming systems, the video bitstreams (204, 207, 209) may be encoded according to a particular video encoding / compression standard. Examples of these standards include ITU-T Recommendation H.265. Also under development is a video coding standard informally known as Versatile Video Coding, or VVC. The disclosed subject matter may be used in the context of VVC.

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

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

[0023] The video decoder (210) may include a parser (320) for reconstructing symbols (321) from the entropy-encoded video sequence. These symbol categories potentially include information used to manage the operation of the decoder (210) and information for controlling a rendering device, such as a display (212) that is not an integral part of the decoder but may be coupled to the decoder, as shown in FIG. 2. The rendering device control information may be in 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 and entropy decode the received coded video sequence. The coding of the coded video sequence may follow a video coding technique or standard, such as variable-length coding, Huffman coding, or arithmetic coding with or without context sensitivity, among other principles well known to those skilled in the art. The parser (320) can extract, in the video decoder, a set of subgroup parameters for at least one of the subgroups of pixels from the coded video sequence based on at least one parameter corresponding to the group. The subgroups may include groups of pictures (GOPs), images, tiles, slices, macroblocks, coding units (CUs), blocks, transform units (TUs), prediction units (PUs), etc. The entropy decoder / parser can also extract information from the coded video sequence, such as transform coefficients, quantizer parameter values, and motion vectors.

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

[0025] The reconstruction of the symbols (321) can involve several different units, depending on the type of coded video image or part thereof (inter- and intra-image, inter- and intra-block, etc.), and other factors. Which units are involved and how can be controlled by subgroup control information parsed from the coded video sequence by the parser (320). The flow of such subgroup control information between the parser (320) and the following units is not depicted for clarity.

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

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

[0028] In some cases, the output samples of the scaler / inverse transform (351) may relate to intra-coded blocks, i.e., blocks that do not use prediction information from a previously reconstructed image but can use prediction information from a previously reconstructed portion of the current image. Such prediction information may be provided by an intra-image prediction unit (352). In some cases, the intra-image 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) image (356). The aggregator (355) may add, on a sample-by-sample basis, the prediction information generated by the intra-prediction unit (352) to the output sample information provided by the scaler / inverse transform unit (351).

[0029] In other cases, the output samples of the scalar / inverse transform unit (351) may relate to an inter-coded, potentially motion-compensated block. In such cases, the motion-compensated prediction unit (353) may access a reference picture memory (357) to fetch samples to use for prediction. After motion-compensating the fetched samples according to the symbols (321) associated with the block, these samples may be added by an aggregator (355) to the output of the scalar / inverse transform unit (in this case, referred to as residual samples or residual signals) to generate output sample information. The addresses in the reference picture memory from which the motion compensation unit fetches prediction samples may be controlled by motion vectors available to the motion compensation unit, for example, in the form of symbols (321) that may have 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, as well as motion vector prediction mechanisms.

[0030] The output samples of the aggregator (355) can be subjected to various loop filtering techniques in the loop filter unit (356). Video compression techniques can include in-loop filtering techniques 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 the decoding of previous parts (in decoding order) of the coded image or coded video sequence, or can respond to previously reconstructed and loop-filtered sample values.

[0031] The output of the loop filter unit (356) can be a sample stream that can be output to the rendering device (212) as well as stored in a reference image memory (356) for use in future inter-image prediction.

[0032] Once a particular coded image is fully reconstructed, it can be used as a reference image for future predictions. Once a coded image is fully reconstructed and the coded image is identified as a reference image (e.g., by the parser (320)), the current reference image (356) can become part of the reference image buffer (357), and a new current image memory can be reallocated before starting the reconstruction of a subsequent coded image.

[0033] The video decoder 320 may perform decoding operations according to a given video compression technology, which may be documented in a standard such as ITU-T Rec. H.265. The coded video sequence may conform to the syntax specified by the video compression technology or standard being used, in the sense that it conforms to the syntax of the video compression technology or standard as specified 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 a range defined by the level of the video compression technology or standard. In some cases, the level imposes limitations on the maximum picture size, maximum frame rate, maximum reconstruction sample rate (e.g., measured in megasamples per second), maximum reference picture size, etc. The limitations imposed by the level may in some cases be further constrained by the specification of a hypothetical reference decoder (HRD) and metadata for HRD buffer management signaled in the coded video sequence.

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

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

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

[0037] The video source (201) can provide a source video sequence to be encoded 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 suitable 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) can be a storage device that stores previously processed video. In a video conferencing system, the video source (203) can be a camera that captures local image information as a video sequence. The video data can be provided as multiple individual images that, when viewed sequentially, create a sense of motion. The image itself can be organized as a spatial array of pixels, each of which can contain one or more samples, depending on the sampling structure, color space, etc., in use. Those skilled in the art can easily understand the relationship between pixels and samples. The following discussion focuses on samples.

[0038] In one embodiment, the encoder (203) can encode and compress images of a source video sequence into a coded video sequence (443) in real time or under any other time constraint required by the application. Enforcing an appropriate coding rate is one function of the controller (450). The controller controls and is functionally coupled to other functional units, as described below. For clarity, this coupling is not depicted. Parameters set by the controller include rate control-related parameters (e.g., picture skip, quantizer, lambda value for rate-distortion optimization techniques), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. Those skilled in the art can readily identify other functions of the controller (450) as they may be relevant to a video encoder (203) optimized for a particular system design.

[0039] Some video encoders operate in a "coding loop," which will be readily apparent to those skilled in the art. As an overly simplified explanation, the coding loop consists of an encoding portion, an encoder (430) (hereinafter, "source coder") (responsible for generating symbols based on the input image to be coded and a reference image), and a (local) decoder (433) embedded in the encoder (203) that reconstructs the symbols and generates sample data that the (remote) decoder also generates (since the video compression techniques considered in the disclosed subject matter ensure that any compression between the symbols and the coded video bitstream is lossless). This reconstructed sample stream is input into a reference image memory (434). Because decoding the symbol stream yields bit-exact results regardless of the decoder's location (local or remote), the contents of the reference image buffer are also bit-exact between the local and remote encoders. In other words, the predictive portion of the encoder "sees" the exact same sample values ​​as the decoder "sees" when using prediction during decoding. This basic principle of reference image synchrony (and the resulting drift if synchrony cannot be maintained, e.g., due to channel errors) is well known to those skilled in the art.

[0040] The operation of the "local" decoder (433) may be the same as that of the "remote" decoder (210), as described in detail above in connection with Figure 3. However, briefly referring also to Figure 3, because symbols are available and can be losslessly encoded / decoded into the coded video sequence by the entropy coder (445) and parser (320), the entropy decoding portion of the decoder (210), including the channel (312), receiver (310), buffer (315), and parser (320), may not be fully implemented in the local decoder (433).

[0041] At this point, it can be observed that decoder techniques, excluding analysis / entropy decoding, present in a decoder must necessarily exist in the corresponding encoder in substantially identical functional form. For this reason, the disclosed subject matter focuses on decoder operation. A description of the encoder techniques can be omitted, as they are the opposite of the decoder techniques, which are described comprehensively. Only in certain areas is a more detailed description necessary, which is provided below.

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

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

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

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

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

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

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

[0049] An Intra Picture (I-picture) may be one that can be coded and decoded without using other frames in the sequence as a source of prediction. Some video codecs allow for different types of Intra Pictures, e.g., Independent Decoder Refresh Pictures. Those skilled in the art are aware of these variants of I-pictures, as well as their respective applications and characteristics.

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

[0051] Bidirectionally predicted images (B-pictures) may be encoded and decoded using intra- or inter-prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multiple predicted images may use more than two reference images and associated metadata for the reconstruction of a single block.

[0052] A source image is typically spatially subdivided into multiple sample blocks (e.g., 4x4, 8x8, 4x8, or 16x16 sample blocks, 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 image of the block. For example, blocks of an I-image may be coded nonpredictively or predictively with reference to previously coded blocks of the same image (spatial prediction or intraprediction). Pixel blocks of a P-image may be coded nonpredictively, via spatial prediction, or via temporal prediction, with reference to one previously coded reference image. Blocks of a B-image may be coded nonpredictively, via spatial prediction, or via temporal prediction, with reference to one or two previously coded reference images.

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

[0054] In one embodiment, the transmitter (440) can transmit additional data along with the coded video. The video coder (430) can include such data as part of the coded video sequence. The additional data can include temporal, spatial, or SNR enhancement layers, other forms of redundant data such as redundant images and slices, Supplementary Enhancement Information (SEI) messages, Visual Usability Information (VUI) parameter set fragments, etc.

[0055] Before describing particular aspects of the disclosed subject matter in more detail, it is necessary to introduce certain terms that will be referenced in the remainder of the specification.

[0056] Hereinafter, a sub-image refers to a rectangular arrangement of samples, blocks, macroblocks, coding units, or similar entities that can be semantically grouped and coded independently at varying resolutions, possibly together. One or more sub-images can form an image. One or more coded sub-images can form a coded image. One or more sub-images can be assembled into an image, and one or more sub-images can be extracted from an image. In certain circumstances, one or more coded sub-images can be assembled into a coded image in the compressed domain without transcoding to the sample level, and in the same or certain other cases, one or more coded sub-images can be extracted from a coded image in the compressed domain.

[0057] Hereinafter, Adaptive Resolution Change (ARC) refers to a mechanism by which the resolution of an image or sub-image in a coded video sequence can be changed, for example by resampling a reference image. Hereinafter, ARC parameters refer to the control information needed to perform the adaptive resolution change, which may include, for example, filter parameters, scaling factors, output and / or reference image resolutions, various control flags, etc.

[0058] The above description focuses on encoding and decoding a single, semantically independent coded video image. Before describing the implications of encoding / decoding multiple sub-images with independent ARC parameters and the additional complexities that they imply, options for signaling the ARC parameters can be discussed.

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

[0060] Classes of ARC parameters may include:

[0061] - Separate or combined up / downsample coefficients in the X and Y dimensions.

[0062] - An up / down-sampling factor with an added temporal dimension, which indicates a constant speed of zooming in / out for a given number of images.

[0063] Either of the above two may involve the encoding of one or more possibly short syntax elements that may point to tables containing the coefficients.

[0064] - Resolution in the X or Y dimension of the combined or separate input, output, reference, or coded images, in units of samples, blocks, macroblocks, CUs, or other suitable granularity. If there are two or more resolutions (e.g., one for the input image and one for the reference image), in some cases one set of values ​​may be inferred from another set of values. This may be gated, for example, using a flag. See below for more detailed examples.

[0065] - "Warping" coordinates are similar to those used in H.263 Annex P, again with the appropriate granularity as described above. H.263 Annex P defines one efficient way to encode such warping coordinates, but other, potentially more efficient, methods could conceivably be devised. For example, the variable-length, reversible "Huffman"-style encoding of Annex P's warping coordinates could be replaced by an appropriate-length binary encoding, where the length of the binary codeword could be derived, for example, from the maximum image size, possibly multiplied by a specific factor and offset by a specific value to allow "warping" outside the bounds of the maximum image size.

[0066] - Up- or downsample filter parameters. In the simplest case, there may be only one filter for upsampling and / or downsampling. However, in some cases it may be advantageous to have more flexibility in the filter design, which may require signaling of the filter parameters. Such parameters may be selected via an index into a list of possible filter designs, the filter may be fully specified (e.g., via a list of filter coefficients using an appropriate entropy coding technique), the filter may be selected implicitly via the up / downsample ratio and signaled accordingly according to one of the mechanisms mentioned above, etc.

[0067] Hereinafter, the description assumes the encoding of a finite set of up / downsample coefficients (the same coefficients used in both the X and Y dimensions) indicated via codewords. The codewords can advantageously be coded with variable length, for example using Ext-Golomb codes common to certain syntax elements of video coding specifications such as H.264 and H.265. One suitable mapping of values ​​to up / downsample coefficients can, for example, follow the table below:

[0068] [Table 1]

[0069] Many similar mappings can be devised, depending on the needs of the application and the capabilities of the upscaling and downscaling mechanisms available in the video compression technology or standard. This table can be expanded to include many more values. The values ​​can also be represented using entropy coding mechanisms other than Ext-Golomb codes, such as binary coding. This has particular advantages when the resampling factor is important outside the video processing engine itself (encoder and decoder are paramount), for example, by MANE. Note that in the (probably) most common case where no resolution change is required, a short Ext-Golomb code (only a single bit in the table above) can be chosen. This may be more coding efficient than using binary coding in the most common case.

[0070] The number of entries in a table, and their semantics, may be fully or partially configurable. For example, the basic outline of the table may be conveyed in a "higher" parameter set, such as a sequence or decoder parameter set. Alternatively, or in addition, one or more such tables may be defined in a video coding technology or standard and may be selected, for example, via a decoder or sequence parameter set.

[0071] Below we explain how the upsample / downsample coefficients (ARC information) coded as described above are included in video coding techniques or standard syntax. Similar considerations may apply to one or several codewords that control the up / downsample filters. See below for a discussion of when a filter or other data structure requires a relatively large amount of data.

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

[0073] The JVCET-M135-v1 cited above includes an ARC reference (505) (index) located in an image parameter set (504), which indexes a table (506) containing target resolutions located in a sequence parameter set (507). The placement of possible resolutions in the table (506) of the sequence parameter set (507) can be justified by the use of the SPS as an interoperability negotiation point during capability exchange, according to a linguistic statement by the implementer. Resolution can be varied from image to image, within the limits set by the values ​​in the table (506), by referencing the appropriate image parameter set (504).

[0074] Continuing with reference to Figure 5, the following additional options may exist for conveying ARC information in a video bitstream: Each of these options has specific advantages over existing techniques such as those described above. Options may coexist within the same video coding technology or standard.

[0075] In one embodiment, ARC information (509), such as the resampling (zoom) ratio, can be present in a slice header, a GOB header, a tile header, or a tile group header (hereafter referred to as a tile group header) (508). This is sufficient when the ARC information is small, such as a single variable-length ue(v) or a fixed-length codeword of a few bits, as described above. Having the ARC information directly in the tile group header has the added advantage that the ARC information may apply to, for example, a sub-image represented by that tile group, rather than the entire image. See also below. Additionally, even if a video compression technology or standard only allows for image-wide adaptive resolution changes (as opposed to, for example, tile group-based adaptive resolution changes), having the ARC information in the tile group header rather than in an H.263-style image header offers certain advantages from an error resilience perspective.

[0076] In the same or another embodiment, the ARC information (512) itself can reside in an appropriate parameter set (511), such as a picture parameter set, a header parameter set, a tile parameter set, or an adaptive parameter set (an adaptive parameter set is shown). It may be advantageous for the scope of the parameter set to be no larger than the image, e.g., a tile group. The use of the ARC information is implicit through the activation of the associated parameter set. For example, if a video coding technology or standard only contemplates image-based ARC, a picture parameter set or its equivalent may be appropriate.

[0077] In the same or another embodiment, 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) that has a scope beyond a single image, such as a sequence parameter set or a decoder parameter set.

[0078] The implicit activation of an additional level of indirection from the tile group header PPS (SPS) as used in JVET-M0135-v1 seems unnecessary because picture parameter sets, similar to sequence parameter sets, can be used for capability negotiation or announcement (as used in certain standards such as RFC3984). However, if the ARC information should also be applicable to sub-pictures represented by tile groups, for example, a parameter set with activation scope limited to the tile group, such as an adaptive parameter set or a header parameter set, may be a better choice. Also, if the size of the ARC information exceeds a negligible size (e.g., if it contains filter control information such as a large number of filter coefficients), it may be a better choice from the perspective of coding efficiency than directly using the header (508), since the parameters may be reusable by future pictures or sub-pictures by referencing the same parameter set.

[0079] When using a sequence parameter set or another higher level parameter set with a range that spans multiple images, certain considerations may apply.

[0080] 1. The parameter set for storing the ARC information table (516) may be a sequence parameter set in some cases, but may also advantageously be a decoder parameter set in other cases. A decoder parameter set can have multiple CVSs, i.e., activation ranges for all coded video bits in the coded video stream, i.e., from the start of the session to the end of the session. Such ranges may be more appropriate because possible ARC coefficients may represent decoder capabilities that may be implemented in hardware, and hardware capabilities tend not to change across CVSs (for image sequences of one second or less in length, at least in some entertainment systems). That said, placing the table in a sequence parameter set is explicitly included in the deployment options described herein, particularly in connection with point 2 below.

[0081] 2. It is advantageous to place the ARC reference information (513) directly in the Picture / Slice / Tile / GOB / Tile Group Header (hereafter referred to as the Tile Group Header) (514) rather than in the picture parameter set as in JVCET-M0135-v1. The reason is as follows: If the encoder wants to change a single value in the picture parameter set, such as the ARC reference information, it needs to create a new PPS and reference the new PPS. It is assumed that only the ARC reference information is changed, and other information, such as the quantization matrix information of the PPS, remains the same. This information can be quite large and needs to be retransmitted to complete the new PPS. Since the ARC reference information can be a single codeword, such as an index into the table (513), and is the only value that changes, it would be cumbersome and wasteful to retransmit all the quantization matrix information, for example. To that extent, avoiding indirect referencing via the PPS, as proposed in JVET-M0135-v1, may be significantly better in terms of coding efficiency. Similarly, putting the ARC reference information in the PPS has the additional disadvantage that the scope of the image parameter set activation is the image, so the ARC information referenced by the ARC reference information (513) must necessarily apply to the entire image, not a sub-image.

[0082] In the same or another embodiment, signaling of ARC parameters can follow a detailed example as outlined in Figure 6. Figure 6 shows a syntax diagram in a representation used in video coding standards since at least 1993. The notation of such syntax diagrams roughly follows C-style programming. Bolded lines indicate syntax elements present in the bitstream, while non-bolded lines often indicate control flow or variable setting.

[0083] The Tile Group Header (601), an example syntax structure for a header applicable to a (possibly rectangular) portion of an image, can conditionally contain the variable-length Exp-Golom coding syntax element dec_pic_size_idx (602) (shown in bold). The presence of this syntax element in the Tile Group Header, the value of the flag not shown here in bold, can gate the use of adaptive resolution (603), which means that the flag is present in the bitstream at the point where it occurs in the syntax diagram. Whether adaptive resolution is used for this image or part of it may be signaled in any higher-level syntax structure, inside or outside the bitstream. In the example shown, it is signaled in the sequence parameter set, as outlined below.

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

[0085] If adaptive resolution is used, in this example, it is the output resolution in samples that is encoded (613). 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 image. Elsewhere in the video coding technology or standard, specific limits on either value can be defined. For example, a level definition might limit the total number of output samples, which might be the product of the values ​​of these two syntax elements. Also, a particular video coding technology or standard, or an external technology or standard such as a system standard, might limit the range of numerical values ​​(e.g., one or both dimensions must be divisible by a power of 2) or aspect ratios (e.g., width and height must have a relationship such as 4:3 or 16:9). Such limits may be introduced to facilitate hardware implementation or for other reasons and are well known in the art.

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

[0087] Finally, a table of possible decoded image widths and heights is shown. Such a table can be represented, for example, by the table notation (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 encoded value is zero, there is one table entry. If the value is 5, there are six table entries. Then, for each "row" in the table, the syntax includes the width and height of the decoded image (617).

[0088] The presented table entries (617) can be indexed using the syntax element dec_pic_size_idx (602) in the tile group header, thus allowing for different decoding sizes (actually zoom ratios) per tile group.

[0089] Certain video coding technologies or standards, such as VP9, ​​support spatial scalability by implementing a specific form of reference picture resampling (signaled in a manner entirely different from the disclosed subject matter) along with temporal scalability to enable spatial scalability. In particular, certain reference pictures can be upsampled to higher resolutions using ARC-style techniques to form the basis of spatial enhancement layers. These upsampled pictures can then be refined using regular prediction mechanisms at higher resolutions to add detail.

[0090] The disclosed subject matter can be used in such environments. In some cases, in the same or another embodiment, values ​​in the NAL unit header, e.g., the Temporal ID field, can be used to indicate not only temporal but also spatial layers. Doing so may have certain advantages for certain system designs; for example, existing Selected Forwarding Units (SFUs) created and optimized for selective forwarding of temporal layers based on the Temporal ID value in the NAL unit header can be used without modification for scalable environments. To enable this, there may be a requirement for a mapping between coded picture size and temporal layers, indicated by the Temporal ID field in the NAL unit header.

[0091] In some video coding techniques, an access unit (AU) may refer to a coded picture, slice, tile, NAL unit, etc. that is captured at a given time instance and composited into a bitstream for the respective picture / slice / tile / NAL unit. This time instance may be the composition time.

[0092] HEVC and certain other video coding technologies use a picture order count (POC) value to indicate a selected reference picture among multiple reference pictures stored in a decoded picture buffer (DPB). When an access unit (AU) is composed of 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 inferred that they were created from content with the same composition time. In other words, a scenario in which two pictures / slices / tiles carry the same specific POC value can indicate that the two pictures / slices / tiles belong to the same AU and have the same composition time. Conversely, two pictures / tiles / slices with different POC values ​​can indicate that the respective pictures / slices / tiles belong to different AUs and have different composition times.

[0093] In embodiments of the disclosed subject matter, the aforementioned strict relationship can be relaxed in that an access unit can contain pictures, slices, or tiles with different POC values. By allowing different POC values ​​within an access unit, it becomes possible to use the POC values ​​to identify potentially independently decodable pictures / slices / tiles at the same presentation time. This can enable support for multiple scalable layers without modifying reference picture selection signaling (e.g., reference picture set signaling or reference picture list signaling), as described in more detail below.

[0094] However, for other images / slices / tiles with different POC values, it is still desirable to be able to identify the AU to which the image / slice / tile belongs from the POC value alone. This can be achieved as described below.

[0095] In the same or other embodiments, the access unit count (AUC) may be signaled in a high-level syntax structure such as a NAL unit header, slice header, tile group header, SEI message, parameter set, or AU delimiter. The AUC value can be used to identify which NAL unit, picture, slice, or tile belongs to a given AU. The AUC value may correspond to a distinct synthesis time instance. The AUC value may be equal to a multiple of the POC value. The AUC value can be calculated by dividing the POC value by an integer value. In some cases, the division operation may impose a certain burden on the decoder implementation. In such cases, the division operation can be replaced with a shift operation by slightly restricting the numbering space of the AUC values. For example, the AUC value may be equal to the most significant bit (MSB) value of the POC value range.

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

[0097] In the same or another embodiment, the value of poc_cycle_au may be derived from information located, for example, in a video parameter set (VPS) that identifies the number of spatial or SNR layers in the coded video sequence. Such possible relationships are briefly described below. While the derivation described above may save a few bits in the VPS and improve coding efficiency, it may be advantageous to explicitly code poc_cycle_au in an appropriate higher-level syntax structure hierarchically lower in the video parameter set, allowing poc_cycle_au to be minimized for specific subportions of the bitstream, such as pictures. This optimization may potentially save more bits than those saved in the derivation process described above, since the POC value (and / or the values ​​of syntax elements that indirectly reference POC) may be coded in lower-level syntax structures.

[0098] In the same or another embodiment, Figure 9 shows an example of a syntax table for signaling the vps_poc_cycle_au syntax element in the VPS (or SPS), which indicates the poc_cycle_au to be used for all pictures / slices of a coded video sequence, and the slice_poc_cycle_au syntax element in the slice header, which indicates the poc_cycle_au of the current slice. If the POC value increases uniformly per AU, vps_contant_poc_cycle_per_au in the VPS is set equal to 1, and vps_poc_cycle_au in the VPS is signaled. In this case, slice_poc_cycle_au is not explicitly signaled, and the AUC value for each AU is calculated by dividing the POC value by vps_poc_cycle_au. If the POC value does not increase uniformly per AU, vps_contant_poc_cycle_per_au in the VPS is set to 0. In this case, vps_access_unit_cnt is not signaled, but slice_access_unit_cnt is signaled in the slice header of each slice or image. Each slice or image may have a different value of slice_access_unit_cnt. The AUC value for each AU is calculated by dividing the POC value by slice_poc_cycle_au. Figure 10 shows a block diagram illustrating the related workflow.

[0099] In the same or other embodiments, images, slices, or tiles corresponding to AUs with the same AUC value may be associated with the same decoding or output time instance, even though the POC values ​​of the images, slices, or tiles may differ. Thus, all or a subset of images, slices, or tiles associated with the same AU may be decoded in parallel and output simultaneously, without any inter-analysis / decoding dependency between images, slices, or tiles within the same AU.

[0100] In the same or other embodiments, images, slices, or tiles corresponding to AUs with the same AUC value may be associated with the same composition / display time instance, even if the images, slices, or tiles have different POC values. If composition time is included in the container format, images can be displayed at the same time instance even if they correspond to different AUs if their composition time is the same.

[0101] In the same or other embodiments, each image, slice, or tile may have the same temporal identifier (temporal_id) within the same AU. All or a subset of images, slices, or tiles corresponding to a time instance may be associated with the same temporal sublayer. In the same or other embodiments, each image, slice, or tile may have the same or different spatial layer id (layer_id) within the same AU. All or a subset of images, slices, or tiles corresponding to a time instance may be associated with the same or different spatial layers.

[0102] The techniques for signaling adaptive resolution parameters described throughout may be implemented as computer software using computer-readable instructions and physically stored on one or more computer-readable media. For example, Figure 7 illustrates a computer system 700 suitable for implementing certain embodiments of the disclosed subject matter.

[0103] Computer software may be coded using any suitable machine or computer language, which may be subject to mechanisms such as assembly, compilation, linking, etc. to generate code containing instructions that may be executed by a computer central processing unit (CPU), graphics processing unit (GPU), etc., directly, or via interpretation, microcode execution, etc.

[0104] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smart phones, gaming devices, Internet of Things devices, and the like.

[0105] 7 for computer system 700 are exemplary in nature and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing embodiments of the present disclosure, nor should the arrangement of components be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary embodiment of computer system 700.

[0106] The computer system 700 may include certain human interface input devices that may respond to input by one or more human users, for example, via tactile input (e.g., keystrokes, swipes, data glove movements), audio input (e.g., voice, clapping), visual input (e.g., gestures), or olfactory input (not shown). Human interface devices may also be used to capture certain media not necessarily directly associated with conscious human input, such as audio (e.g., speech, music, ambient sounds), images (e.g., scanned images, photographic images obtained from a still image camera), and video (e.g., two-dimensional video, three-dimensional video, including stereoscopic video).

[0107] The input human interface devices may include one or more (only one of each shown) of a keyboard 701, a mouse 702, a trackpad 703, a touch screen 710, a data glove 704, a joystick 705, a microphone 706, a scanner 707, and a camera 708.

[0108] The computer system 700 may also include certain human interface output devices. Such human interface output devices may stimulate one or more of the human user's senses, for example, through tactile output, sound, light, and smell / taste. Such human interface output devices may include haptic output devices (e.g., haptic feedback devices that may include haptic feedback via a touch screen 710, data gloves 704, or joystick 705, but do not function as input devices), audio output devices (e.g., speakers 709, headphones (not shown)), visual output devices (e.g., screen 710, including CRT screens, LCD screens, plasma screens, and OLED screens, each with or without touch screen input capability, each with or without haptic feedback capability, some of which may provide two-dimensional visual output or output in more than three dimensions, such as via stereoscopic graphics output, virtual reality glasses (not shown), holographic displays, smoke tanks (not shown), and printers (not shown)).

[0109] The computer system 700 may also include human-accessible storage devices and associated media, such as optical media including a CD / DVD ROM / RW 720 with media 721 such as CDs / DVDs, thumb drives 722, removable hard drives or solid state drives 723, legacy magnetic media such as tape or floppy disks (not shown), and specialized ROM / ASIC / PLD-based devices (not shown) such as security dongles.

[0110] Those skilled in the art should also understand that the term "computer-readable medium" as used in connection with the subject matter of this disclosure does not include transmission media, carrier waves, or other transitory signals.

[0111] The computer system 700 may also include interfaces to one or more communication networks. The networks may be, for example, wireless, wired, or optical. The networks may further be local, wide area, metropolitan, vehicular, and industrial, real-time, delay-tolerant, and the like. Examples of networks include local area networks such as Ethernet; cellular networks including WLAN, GSM, 3G, 4G, 5G, LTE, and the like; TV wired or wireless wide area digital networks including cable TV, satellite TV, and terrestrial broadcast TV; vehicular and industrial networks including CANBus; and the like. Particular networks typically require an external network interface adapter connected to a particular general-purpose data port or peripheral bus (749) (e.g., a USB port on the computer system 700); others are typically built into the core of the computer system 700 by attaching to a system bus such as those described below (e.g., an Ethernet interface to a PC computer system or a cellular network interface to a smart phone computer system). Using any of these networks, the computer system 700 can communicate with other entities. Such communication can be unidirectional, receive only (e.g., broadcast television), unidirectional transmit only (e.g., from a CANbus to a particular CANbus device), or bidirectional (e.g., to another computer system using a local or wide area digital network). Specific protocols and protocol stacks can be used with each of these networks and network interfaces, as described above.

[0112] The aforementioned human interface devices, human-accessible storage devices, and network interfaces may be attached to core 740 of computer system 700 .

[0113] The core 740 may include one or more central processing units (CPUs) 741, graphics processing units (GPUs) 742, dedicated programmable processing units in the form of field programmable gate areas (FPGAs) 743, hardware accelerators 744 for specific tasks, etc. These devices, along with read-only memory (ROM) 745, random access memory 746, and internal mass storage such as an internal non-user-accessible hard drive, SSD, etc. 747, may be connected via a system bus 748. In some computer systems, the system bus 748 is accessible in the form of one or more physical plugs, allowing expansion with additional CPUs, GPUs, etc. Peripheral devices may be connected directly to the core's system bus 748 or via a peripheral bus 749. Peripheral bus architectures include PCI, USB, etc.

[0114] The CPU 741, GPU 742, FPGA 743, and accelerator 744, combined, may execute specific instructions that may constitute the aforementioned computer code, which may be stored in ROM 745 or RAM 746. Transient data may also be stored in RAM 746, while permanent data may be stored, for example, in internal mass storage device 747. Cache memory, which may be closely associated with one or more of the CPU 741, GPU 742, mass storage device 747, ROM 745, RAM 746, etc., may be used to enable fast storage and retrieval to any of the memory devices.

[0115] The computer-readable medium may contain computer code for performing various computer-implemented operations. The medium and computer code may be those specially designed and constructed for the purposes of the present disclosure, or they may be of the kind well known and available to those skilled in the computer software arts.

[0116] By way of example and not limitation, computer system 700 having the architecture, and specifically core 740, may 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 may be user-accessible mass storage devices, as introduced above, as well as media associated with specific storage devices of core 740 that are non-transitory in nature, such as core-internal mass storage device 747 or ROM 745. Software implementing various embodiments of the present disclosure may be stored on such devices and executed by core 740.

[0117] The computer-readable medium may include one or more memory devices or chips, depending on particular needs. Software may cause the core 740, and in particular the processors therein (including CPUs, GPUs, FPGAs, etc.), to perform certain processes or portions of certain processes described herein, including defining data structures stored in RAM 746 and modifying such data structures according to software-defined processes. Additionally, or alternatively, the computer system may provide functionality as a result of logic hardwired or otherwise embodied in circuitry (e.g., accelerator 744) that can operate in place of or in conjunction with software to perform certain processes or portions of certain processes described herein.

[0118] Where appropriate, references to software can encompass logic, and vice versa. References to computer-readable media can encompass, where appropriate, circuitry (such as an integrated circuit (IC)) that stores software for execution, circuitry that embodies logic for execution, or both. The present disclosure encompasses any appropriate combination of hardware and software.

[0119] Figure 8 shows an example of a video sequence structure with adaptive resolution change by combining temporal_id, layer_id, POC, and AUC values. In this example, an image, slice, or tile in the first AU with AUC=0 can have temporal_id=0 and layer_id=0 or 1, while an image, slice, or tile in the second AU with AUC=1 can have temporal_id=1 and layer_id=0 or 1, respectively. The value of POC increases by 1 for each image, regardless of the values ​​of temporal_id and layer_id. In this example, the value of poc_cycle_au can be equal to 2. Preferably, the value of poc_cycle_au may be set equal to the number of (spatial scalability) layers. Thus, in this example, the value of POC increases by 2 and the value of AUC increases by 1.

[0120] 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 RPS or RPL, the selected reference picture is indicated by signaling the value of POC or the delta value of POC between the current picture and the selected reference picture. For the disclosed subject matter, RPS and RPL can be used to indicate the inter-picture or inter-layer prediction structure without changing the signaling, with the following limitations: If the value of temporal_id of a reference picture is greater than the value of 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 layer_id of a reference picture is greater than the value of layer_id of the current picture, the current picture may not use the reference picture for motion compensation or other prediction.

[0121] In the same and other embodiments, motion vector scaling based on POC differences for temporal motion vector prediction may be disabled across multiple images within an access unit. Thus, although each image may have a different POC value within an access unit, the motion vectors are not scaled and are not used for temporal motion vector prediction within the access unit. This is because reference images with different POCs within the same AU are considered to have the same time instance. Thus, in this embodiment, if the reference image belongs to the AU associated with the current image, the motion vector scaling function may return 1.

[0122] In the same and other embodiments, scaling of motion vectors based on POC difference for temporal motion vector prediction may be optionally disabled across multiple images if the spatial resolution of the reference image differs from the spatial resolution of the current image. When motion vector scaling is allowed, the motion vectors are scaled based on both the POC difference and the spatial resolution ratio between the current image and the reference image.

[0123] In the same or another embodiment, for temporal motion vector prediction, motion vectors may be scaled based on the AUC differential instead of the POC differential, especially when poc_cycle_au has non-uniform values ​​(when vps_contant_poc_cycle_per_au==0), otherwise (when vps_contant_poc_cycle_per_au==1), the scaling of motion vectors based on the AUC differential may be identical to the scaling of motion vectors based on the POC differential.

[0124] In the same or another embodiment, when a motion vector is scaled based on the AUC difference, a reference motion vector (having the same AUC value) in the same AU as the current image is not scaled based on the AUC difference, but is used for motion vector prediction with or without scaling based on the spatial resolution ratio between the current image and the reference image.

[0125] In the same and other embodiments, the AUC value is used to identify AU boundaries and is used for hypothetical reference decoder (HRD) operations that require input and output timing at AU granularity. In most cases, the decoded image with the top layer within the AU is output for display. The AUC value and layer_id value can be used to identify the output image.

[0126] In one embodiment, an image can be composed of one or more sub-images. Each sub-image can cover a local region or the entire region of the image. The area supported by a sub-image may or may not overlap with the area supported by another sub-image. The area comprised by one or more sub-images may or may not cover the entire region of the image. When an image is composed of sub-images, the area supported by a sub-image is the same as the area supported by the image.

[0127] In the same embodiment, a sub-image may be coded by a coding method similar to that used for the coded image. A sub-image may be coded independently or may be coded dependently on another sub-image or coded image. A sub-image may or may not have an analytical dependency from another sub-image or coded image.

[0128] In the same embodiment, the coded sub-images may be included in one or more layers. The coded sub-images within a layer may have different spatial resolutions. The original sub-images may be spatially resampled (upsampled or downsampled), coded with different spatial resolution parameters, and included in the bitstream corresponding to the layer.

[0129] In the same or another embodiment, a sub-image of (W, H), where W denotes the width of the sub-image and H denotes the height of the sub-image, may be coded and included in the coded bitstream corresponding to layer 0, while a sub-image of (W*S), upsampled (or downsampled) from the sub-image with the original spatial resolution, may be coded and included in the coded bitstream corresponding to layer 1. w,k ,H*S h,k ) may be encoded and included in the coded bitstream corresponding to layer k, where S w,k、 S h,k indicates the horizontal and vertical resampling ratio. S w,k、 S h,k If the value of is greater than 1, resampling is equivalent to upsampling. w,k、 S h,k If the value of is less than 1, resampling is equivalent to downsampling.

[0130] In the same or another embodiment, the coded subimages within a layer may have different visual quality than the coded subimages within another layer, either within the same subimage or within a different subimage. For example, subimage i of layer n may have a quantization parameter Q i,n However, subimage j of layer m is coded with the quantization parameter Q j,m is encoded as

[0131] In the same or another embodiment, encoded sub-images within a layer may be independently decodable without any analysis or decoding dependency from encoded sub-images in another layer of the same local region. A sub-image layer that can be independently decodable without reference to another sub-image layer of the same local region is an independent sub-image layer. Encoded sub-images within an independent sub-image layer may or may not have decoding or analysis dependencies from previously encoded sub-images in the same sub-image layer, but encoded sub-images may not have dependencies from encoded sub-images in another sub-image layer.

[0132] In the same or another embodiment, coded sub-images within a layer may be dependently decodable, depending on any analysis or decoding from coded sub-images in another layer of the same local region. A sub-image layer that is dependently decodable by reference to another sub-image layer of the same local region is a dependent sub-image layer. Coded sub-images within a dependent sub-image may reference coded sub-images belonging to the same sub-image, previously coded sub-images in the same sub-image layer, or both.

[0133] In the same or another embodiment, a coded sub-picture consists of one or more independent sub-picture layers and one or more dependent sub-picture layers. However, at least one independent sub-picture layer may be present for a coded sub-picture. An independent sub-picture layer may have a layer identifier (layer_id) value, which may be present in the NAL unit header or another higher-level syntax structure, equal to 0. A sub-picture layer with layer_id equal to 0 is a base sub-picture layer.

[0134] In the same or another embodiment, an image may be composed of one or more foreground subimages and one background subimage. The area supported by the background subimage may be equal to the area of ​​the image. The area supported by the foreground subimage may overlap with the area supported by the background subimage. The background subimage may be a base subimage layer, while the foreground subimage may be a non-base (enhancement) subimage layer. One or more non-base subimage layers may reference the same base layer for decoding. Each non-base subimage layer with layer_id equal to a may reference a non-base subimage layer with layer_id equal to b, where a is greater than b.

[0135] In the same or another embodiment, an image may be composed of one or more foreground subimages, with or without a background subimage. Each subimage may have its own base subimage layer and one or more non-base (enhancement) layers. Each base subimage layer may be referenced by one or more non-base subimage layers. Each non-base subimage layer with layer_id equal to a may reference a non-base subimage layer with layer_id equal to b, where a is greater than b.

[0136] In the same or another embodiment, an image may be composed of one or more foreground subimages, with or without background subimages. Each coded subimage within a (base or non-base) subimage layer may be referenced by one or more non-base layer subimages that belong to the same subimage and one or more non-base layer subimages that do not belong to the same subimage.

[0137] In the same or another embodiment, an image may be composed of one or more foreground sub-images with or without background sub-images. A sub-image in layer a may be further divided into multiple sub-images within the same layer. One or more coded sub-images in layer b may reference divided sub-images in layer a.

[0138] In the same or another embodiment, a coded video sequence (CVS) may be a group of coded pictures. A CVS may be composed of one or more coded sub-picture sequences (CSPS), where a CSPS may be a group of coded sub-pictures covering the same local region of an image. A CSPS may have a temporal resolution that is the same as or different from the temporal resolution of the coded video sequence.

[0139] In the same or another embodiment, a CSPS may be coded and included in one or more layers. A CSPS may be composed of one or more CSPS layers. By decoding one or more CSPS layers corresponding to a CSPS, a sequence of sub-images corresponding to the same local region can be reconstructed.

[0140] In the same or another 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 another CSPS.

[0141] In the same or another embodiment, a CSPS layer can have a different temporal resolution (e.g., frame rate) than another CSPS layer, and the original (uncompressed) sub-image sequence may be temporally resampled (upsampled or downsampled), coded with different temporal resolution parameters, and included in the bitstream corresponding to the layer.

[0142] In the same or another embodiment, a sub-image sequence having a frame rate F may be coded and included in the coded bitstream corresponding to layer 0, while F*S t,k A sub-image sequence temporally upsampled (or downsampled) from the original sub-image sequence having S may be coded and included in the coded bitstream corresponding to layer k, where S t,k is the temporal sampling rate for layer k. S t,k If the value of is greater than 1, the temporal resampling process is equivalent to a frame rate up-conversion. t,k If the value of is less than 1, the temporal resampling process is equivalent to a frame rate down-conversion.

[0143] In the same or another embodiment, when a sub-image having CSPS layer a is referenced by a sub-image having CSPS layer b for motion compensation or any inter-layer prediction, if the spatial resolution of CSPS layer a differs from the spatial resolution of CSPS layer b, the decoded pixels in CSPS layer a are resampled and used for reference. The resampling process may require upsampling filtering or downsampling filtering.

[0144] FIG. 11 shows an example video stream including a background video CSPS with layer_id equal to 0 and multiple foreground CSPS layers. A coded sub-picture may consist of one or more CSPS layers, but background regions that do not belong to any foreground CSPS layer may consist of the base layer. The base layer may include background and foreground regions, while the enhancement CSPS layer includes 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 reconstructed pixels and motion vectors of the base layer corresponding to the same region.

[0145] In the same or another embodiment, the video bitstream corresponding to the base layer is included in a track, while the CSPS layers corresponding to each sub-image are included in separate tracks within the video file.

[0146] In the same or another 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.

[0147] In the same or another embodiment, each CSPS layer of each sub-image is stored in a separate track. Each track may or may not have an analysis or decoding dependency from one or more other tracks.

[0148] In the same or another embodiment, each track can include a bitstream corresponding to layers i to j of the CSPS layers of all or a subset of the sub-images, where 0 < i <= j <= k and k is the topmost layer of the CSPS.

[0149] In the same or another embodiment, the image is composed of one or more associated media data including a depth map, an alpha map, 3D geometry data, an occupancy map, etc. Such associated time-limited media data can each be divided into one or more data sub-streams corresponding to one sub-image.

[0150] In the same or another embodiment, FIG. 12 shows an example of a video conference based on the multi-layer sub-image method. The video stream includes one base-layer video bitstream corresponding to the background image and one or more enhancement-layer video bitstreams corresponding to the foreground sub-images. Each enhancement-layer video bitstream corresponds to a CSPS layer. On the display, the image corresponding to the base layer is displayed by default. This includes one or more picture-in-picture (PIP) of the users. When a specific user is selected by the control of the client, the enhancement CSPS layer corresponding to the selected user is decoded and displayed with improved quality or spatial resolution. FIG. 13 is a diagram showing the operation.

[0151] In the same or another embodiment, a network middlebox (such as a router) can select a subset of layers to send to a user depending on its bandwidth. The image / subimage configuration can be used for bandwidth adaptation. For example, if a user does not have the bandwidth, the router can remove layers or select some subimages depending on their importance or based on the setup being used; this can be done dynamically to adapt to the bandwidth.

[0152] Figure 14 illustrates a 360-degree video use case. When a spherical 360-degree image is projected onto a planar image, the projected 360-degree image may be split into multiple sub-images as a base layer. Enhancement layers for specific sub-images may be encoded and sent to the client. A decoder may be able to decode both the base layer containing all sub-images and the enhancement layer for a selected sub-image. If the current viewport is the same as the selected sub-image, the displayed image may be of higher quality with the decoded sub-image with the enhancement layer. Otherwise, the decoded image with the base layer may be displayed with lower quality.

[0153] In the same or another embodiment, optional layout information for display may be present in the file as supplemental information (such as an SEI message or metadata). Depending on the signaled layout information, one or more decoded sub-images may be rearranged and displayed. The layout information may be signaled by a streaming server or broadcaster, regenerated by a network entity or cloud server, or determined by a user's customized settings.

[0154] In one embodiment, when an input image 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-image size and position information may be signaled, such as image size (width, height) and upper-left corner offset information (x_offset, y_offset). Figure 15 shows an example of the layout of divided sub-images, their size and position information, and their corresponding image prediction structures. Layout information, including sub-image size and sub-image position, may be signaled in a high-level syntax structure, such as a parameter set, a slice or tile group header, or an SEI message.

[0155] In the same embodiment, each sub-image corresponding to an independent layer can have its unique POC value within the AU, and when a reference image among the images stored in the DPB is indicated using a syntax element of the RPS or RPL structure, the POC value of each sub-image corresponding to the layer can be used.

[0156] In the same or another embodiment, the layer_id may not be used to indicate the (inter-layer) prediction structure, but the POC(delta) value may be used.

[0157] In the same embodiment, a sub-image corresponding to a layer (or local region) with a POC value equal to N may or may not be used for motion compensated prediction as a reference image for a sub-image corresponding to the same layer (or the same local region) with a POC value equal to N+K. In most cases, the value of the number K may be equal to the maximum number of (independent) layers, which may be equal to the number of sub-regions.

[0158] In the same or another embodiment, Figure 16 shows an extended case of Figure 15. When an input image is divided into multiple (e.g., four) sub-regions, each local region may be coded with one or more layers. In this case, the number of independent layers may be equal to the number of sub-regions, and one or more layers may correspond to a sub-region. Thus, each sub-region may be coded with one or more independent layers and zero or more dependent layers.

[0159] In the same embodiment, in Figure 16, the input image may be divided into four sub-regions. The top right sub-region may be coded as two layers, Layer 1 and Layer 4, while the bottom right sub-region may be coded as two layers, Layer 3 and Layer 5. In this case, Layer 4 may refer to Layer 1 for motion compensation prediction, while Layer 5 may refer to Layer 3 for motion compensation.

[0160] In the same or another embodiment, in-loop filtering across layer boundaries (such as deblocking filtering, adaptive in-loop filtering, reshapers, bilateral filtering, or any deep learning-based filtering) may be disabled (if desired).

[0161] In the same or another embodiment, motion compensated prediction or intra block copying across layer boundaries may be disabled (if desired).

[0162] In the same or another embodiment, border padding for motion compensated prediction or in-loop filtering at sub-picture boundaries can optionally be processed. A flag indicating whether border 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.

[0163] In the same or another embodiment, layout information for sub-regions (or sub-pictures) may be signaled in the VPS or SPS. Figure 17 shows an example of syntax elements for the VPS and SPS. In this example, vps_sub_picture_dividing_flag is signaled in the VPS. 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 of the coded video sequence corresponding to the current VPS may not be divided into multiple sub-regions. In this case, the input picture size may be equal to the coded picture size (pic_width_in_luma_samples, pic_height_in_luma_samples) signaled in the SPS. 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_samples are signaled in the VPS. The values ​​of vps_full_pic_width_in_luma_samples and vps_full_pic_height_in_luma_samples may be equal to the width and height of the input image, respectively.

[0164] In the same embodiment, the values ​​of vps_full_pic_width_in_luma_samples and vps_full_pic_height_in_luma_samples may not be used for decoding, but may be used for compositing and display.

[0165] In the same embodiment, if 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) may be equal to the width and height of the sub-region corresponding to a specific layer. Also, the position of the upper left corner of the sub-region (pic_offset_x, pic_offset_y) may be signaled in the SPS.

[0166] In the same embodiment, the position information (pic_offset_x, pic_offset_y) of the top left corner of the sub-region may not be used for decoding, but may be used for compositing and display.

[0167] In the same or another embodiment, layout information (size and position) of all or a subset of subregions of the input image, as well as inter-layer dependency information, may be signaled in a parameter set or SEI message. Figure 18 shows example syntax elements for 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, and 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 may be equal to the value of num_sub_region. If one or more subregions are coded as multiple layers, the value of num_layers may be greater than the value of num_sub_region. The syntax element direct_dependency_flag[i][j] indicates the dependency from the jth layer to the ith layer. num_layers_for_region[i] indicates the number of layers associated with the i-th subregion. sub_region_layer_id[i][j] indicates the layer_id of the j-th layer associated with the i-th subregion. sub_region_offset_x[i] and sub_region_offset_y[i] indicate the horizontal and vertical positions, respectively, of the top left corner of the i-th subregion. sub_region_width[i] and sub_region_height[i] indicate the width and height, respectively, of the i-th subregion.

[0168] In one embodiment, one or more syntax elements specifying an output layer set indicating one of more layers to be output with or without profile hierarchical level information may be signaled in a high-level syntax structure, such as a VPS, DPS, SPS, PPS, APS, or SEI message. Referring to Figure 19, a syntax element num_output_layer_sets indicating the number of output layer sets (OLSs) in a coded video sequence that references a VPS may be signaled in the VPS. For each output layer set, output_layer_flag may be signaled as many times as the number of output layers.

[0169] In the same embodiment, output_layer_flag[i] equal to 1 specifies that the i-th layer is output. vps_output_layer_flag[i] equal to 0 specifies that the i-th layer is not output.

[0170] In the same or another embodiment, one or more syntax elements specifying profile hierarchical level information for each output layer set may be signaled in a higher-level syntax structure, such as a VPS, DPS, SPS, PPS, APS, or SEI message. Further referring to FIG. 19 , a syntax element num_profile_tile_level indicating the number of profile hierarchical level information per OLS in a coded video sequence referencing a VPS may be signaled in the VPS. For each output layer set, a set of syntax elements for profile hierarchical level information, or an index indicating a specific profile hierarchical level information among entries in the profile hierarchical level information, may be signaled as many times as the number of output layers.

[0171] In the same embodiment, profile_tier_level_idx[i][j] specifies the index within 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.

[0172] In the same or another embodiment, referring to FIG. 20, if the number of maximum layers is greater than 1 (vps_max_layers_minus1>0), the syntax elements num_profile_tile_level and / or num_output_layer_sets may be signaled.

[0173] In the same or another embodiment, referring to FIG. 20, a syntax element vps_output_layers_mode[i] may be present in the VPS indicating the mode of output layer signaling for the i-th output layer set.

[0174] In the same embodiment, vps_output_layers_mode[i] equal to 0 specifies that only the top layer with the i-th output layer set should be output. vps_output_layer_mode[i] equal to 1 specifies that all layers with the i-th output layer set should be output. vps_output_layer_mode[i] equal to 2 specifies that the layers to be output are those with the i-th output layer set and vps_output_layer_flag[i][j] equal to 1. More values ​​may be reserved.

[0175] In the same embodiment, output_layer_flag[i][j] may or may not be signaled depending on the value of vps_output_layers_mode[i] for the i-th output layer set.

[0176] In the same or another embodiment, referring to Figure 20, a flag vps_ptl_signal_flag[i] may be present for the ith output layer set. Depending on the value of vps_ptl_signal_flag[i], profile stratum level information for the ith output layer set may or may not be signaled.

[0177] In the same or another embodiment, referring to FIG. 21, the number of sub-pictures in the current CVS, max_subpics_minus1, may be signaled in a high level syntax structure, for example, a VPS, DPS, SPS, PPS, APS or SEI message.

[0178] In the same embodiment, referring to FIG. 21, if the number of sub-pictures is greater than 1 (max_subpics_minus1>0), the sub-picture identifier sub_pic_id[i] of the i-th sub-picture may be signaled.

[0179] In the same or another embodiment, one or more syntax elements may be signaled in the VPS indicating the subpicture identifiers belonging to each layer of each output layer set. Referring to Figure 22, sub_pic_id_layer[i][j][k] indicates the kth subpicture present in the jth layer of the ith output layer set. With this information, the decoder can know which subpictures can be decoded and output for each layer of a particular output layer set.

[0180] In one embodiment, a picture header (PH) is a syntax structure that contains syntax elements that apply to all slices of a coded picture. A picture unit (PU) is a set of NAL units that are related to each other according to specified classification rules, are consecutive in decoding order, and contain exactly one coded picture. A PU can contain a picture header (PH) and one or more VCL NAL units that make up the coded picture.

[0181] In one embodiment, the SPS (RBSP) may be available to the decoding process before being referenced, may be included in at least one AU with TemporalId equal to 0, or may be provided through external means.

[0182] In one embodiment, the SPS (RBSP) may be available to the decoding process before being referenced, may be included in at least one AU with TemporalId equal to 0 in the CVS that contains one or more PPSs that reference the SPS, or may be provided through external means.

[0183] In one embodiment, the SPS (RBSP) may be available to the decoding process before being referenced by one or more PPSs, may be contained within at least one PU whose nuh_layer_id is equal to the lowest nuh_layer_id value of a PPS NAL unit that references an SPS NAL unit in the CVS, including one or more PPSs that reference the SPS, or may be provided through external means.

[0184] In one embodiment, the SPS (RBSP) may be available to the decoding process before being referenced by one or more PPSs, may be included in at least one PU with TemporalId equal to 0 and nuh_layer_id equal to the lowest nuh_layer_id value of a PPS NAL unit that references the SPS NAL unit, or may be provided through external means.

[0185] In one embodiment, the SPS (RBSP) may be available to the decoding process before being referenced by one or more PPSs, may be included in at least one PU with TemporalId equal to 0 and nuh_layer_id equal to the lowest nuh_layer_id value of a PPS NAL unit that references the SPS in the CVS, including one or more PPSs that reference the SPS, or may be provided through external means.

[0186] In the same or another embodiment, pps_seq_parameter_set_id specifies the value of sps_seq_parameter_set_id for the referenced SPS. The value of pps_seq_parameter_set_id may be the same for all PPSs referenced by coded pictures in a CLVS.

[0187] In the same or another embodiment, all SPS NAL units with a particular value of sps_seq_parameter_set_id in the CVS may have the same content.

[0188] In the same or another embodiment, regardless of the nuh_layer_id value, SPS NAL units may share the same value space for sps_seq_parameter_set_id.

[0189] In the same or another embodiment, the nuh_layer_id value of an SPS NAL unit may be equal to the lowest nuh_layer_id value of the PPS NAL units that reference the SPS NAL unit.

[0190] In one 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 layer with nuh_layer_id equal to n or the (direct or indirect) reference layer of the layer with nuh_layer_id equal to m.

[0191] In one embodiment, the PPS (RBSP) may be available to the decoding process before being referenced, may be contained in at least one AU whose TemporalId is equal to the TemporalId of the PPS NAL unit, or may be provided through external means.

[0192] In one embodiment, the PPS (RBSP) may be available to the decoding process before being referenced, may be included within at least one AU whose TemporalId is equal to the TemporalId of the PPS NAL unit in the CVS that contains one or more PHs (or coded slice NAL units) that reference the PPS, or may be provided through external means.

[0193] In one embodiment, the PPS (RBSP) may be available to the decoding process before being referenced by one or more PHs (or coded slice NAL units), and may be included in at least one PU whose nuh_layer_id is equal to the lowest nuh_layer_id value of the coded slice NAL units that reference the PPS NAL unit in the CVS, including one or more PHs (or coded slice NAL units) that reference the PPS, or may be provided through external means.

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

[0195] In the same or another embodiment, ph_pic_parameter_set_id in PH specifies the value of pps_pic_parameter_set_id for the PPS referenced in the specification. The value of pps_seq_parameter_set_id may be the same in all PPSs referenced by coded pictures in CLVS.

[0196] In the same or another embodiment, all PPS NAL units with a particular value of pps_pic_parameter_set_id within a PU may have the same content.

[0197] In the same or another embodiment, PPS NAL units may share the same value space for pps_pic_parameter_set_id regardless of the nuh_layer_id value.

[0198] In the same or another embodiment, the nuh_layer_id value of a PPS NAL unit may be equal to the lowest nuh_layer_id value of any coded slice NAL unit that references a NAL unit that references the PPS NAL unit.

[0199] In one embodiment, when a PPS with nuh_layer_id equal to m is referenced by one or more coded slice NAL units with nuh_layer_id equal to n, the layer with nuh_layer_id equal to m may be the same as the layer with nuh_layer_id equal to n or the (direct or indirect) reference layer of the layer with nuh_layer_id equal to m.

[0200] In one embodiment, the PPS (RBSP) may be available to the decoding process before being referenced, may be contained in at least one AU whose TemporalId is equal to the TemporalId of the PPS NAL unit, or may be provided through external means.

[0201] In one embodiment, the PPS (RBSP) may be available to the decoding process before being referenced, may be included within at least one AU whose TemporalId is equal to the TemporalId of the PPS NAL unit in the CVS that contains one or more PHs (or coded slice NAL units) that reference the PPS, or may be provided through external means.

[0202] In one embodiment, the PPS (RBSP) may be available to the decoding process before being referenced by one or more PHs (or coded slice NAL units), and may be included in at least one PU whose nuh_layer_id is equal to the lowest nuh_layer_id value of the coded slice NAL units that reference the PPS NAL unit in the CVS, including one or more PHs (or coded slice NAL units) that reference the PPS, or may be provided through external means.

[0203] In one embodiment, the PPS (RBSP) may be available to the decoding process before being referenced by one or more PHs (or coded slice NAL units), and may be included within at least one PU containing one or more PHs (or coded slice NAL units) that reference the PPS, whose TemporalId is equal to the TemporalId of the PPS NAL unit and whose nuh_layer_id is equal to the lowest nuh_layer_id value of the coded slice NAL units that reference the PPS NAL units in the CVS, or may be provided through external means.

[0204] In the same or another embodiment, ph_pic_parameter_set_id in PH specifies the value of pps_pic_parameter_set_id for the PPS referenced in the specification. The value of pps_seq_parameter_set_id may be the same in all PPSs referenced by coded pictures in CLVS.

[0205] In the same or another embodiment, all PPS NAL units with a particular value of pps_pic_parameter_set_id within a PU may have the same content.

[0206] In the same or another embodiment, PPS NAL units may share the same value space for pps_pic_parameter_set_id regardless of the nuh_layer_id value.

[0207] In the same or another embodiment, the nuh_layer_id value of a PPS NAL unit may be equal to the lowest nuh_layer_id value of any coded slice NAL unit that references a NAL unit that references the PPS NAL unit.

[0208] In one embodiment, when a PPS with nuh_layer_id equal to m is referenced by one or more coded slice NAL units with nuh_layer_id equal to n, the layer with nuh_layer_id equal to m may be the same as the layer with nuh_layer_id equal to n or the (direct or indirect) reference layer of the layer with nuh_layer_id equal to m.

[0209] An output layer indicates a layer in the output layer set that is output. An output layer set (OLS) indicates a set of layers that consists of a specified set of layers, where one or more layers in the layer set are designated as output layers. The layer index of an output layer set (OLS) is the index of a layer in the OLS into the list of layers in the OLS.

[0210] A sub-layer indicates a temporally scalable layer of a temporally scalable bitstream, consisting of VCL NAL units with a particular value of the TemporalId variable and associated non-VCL NAL units. A sub-layer representation indicates a subset of a bitstream consisting of NAL units of a particular sub-layer and lower sub-layers.

[0211] The VPS RBSP may be used in the decoding process before being referenced, may be included in at least one AU with TemporalId equal to 0, or may be provided through external means. All VPS NAL units with a particular value of vps_video_parameter_set_id in a CVS may have the same content.

[0212] The vps_video_parameter_set_id provides an identifier for the VPS for reference by other syntax elements. The value of vps_video_parameter_set_id may be greater than 0.

[0213] vps_max_layers_minus1 plus 1 specifies the maximum number of layers allowed in each CVS that references the VPS.

[0214] vps_max_sublayers_minus1 plus 1 specifies 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 may be in the range 0 to 6 inclusive.

[0215] vps_all_layers_same_num_sublayers_flag equal to 1 specifies that all layers in each CVS that references the VPS have the same number of temporal sublayers. vps_all_layers_same_num_sublayers_flag equal to 0 specifies 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 is inferred to be equal to 1.

[0216] vps_all_independent_layers_flag equal to 1 specifies that all layers in the CVS are coded independently without using inter-layer prediction. vps_all_independent_layers_flag equal to 0 specifies that one or more layers in the CVS can use inter-layer prediction. If not present, the value of vps_all_independent_layers_flag is inferred to be equal to 1.

[0217] vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer. For any two non-negative integer values ​​of m and n, if m is less than n, the value of vps_layer_id[m] may be less than vps_layer_id[n].

[0218] vps_independent_layer_flag[i] equal to 1 specifies that the layer with index i does not use inter-layer prediction. vps_independent_layer_flag[i] equal to 0 specifies that the layer with index i can use inter-layer prediction and that the syntax element vps_direct_ref_layer_flag[i][j] for j in the range of 0 to i-1, inclusive, is present in the VPS. If not present, the value of vps_independent_layer_flag[i] is inferred to be equal to 1.

[0219] vps_direct_ref_layer_flag[i][j] equal to 0 specifies 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 specifies that the layer with index j is a direct reference layer for the layer with index i. For i and j in the range 0 to vps_max_layers_minus1, inclusive, if vps_direct_ref_layer_flag[i][j] is not present, it is inferred to be equal to 0. If vps_independent_layer_flag[i] is equal to 0, there may be at least one value of j in the range 0 to i-1, inclusive, for which the value of vps_direct_ref_layer_flag[i][j] is equal to 1.

[0220] The variables NumDirectRefLayers[i], DirectRefLayerIdx[i][d], NumRefLayers[i], RefLayerIdx[i][r], and LayerUsedAsRefLayerFlag[j] are derived as follows: for(i=0;i<=vps_max_layers_minus1;i++){ for(j=0;j<=vps_max_layers_minus1;j++){ dependencyFlag[i][j]=vps_direct_ref_layer_flag[i][j] for(k=0;k <i;k++) if(vps_direct_ref_layer_flag[i][k]&&dependencyFlag[k][j]) dependencyFlag[i][j]=1 } LayerUsedAsRefLayerFlag[i]=0 } for(i=0;i<=vps_max_layers_minus1;i++){ for(j=0,d=0,r=0;j<=vps_max_layers_minus1;j++){ if(vps_direct_ref_layer_flag[i][j]){ DirectRefLayerIdx[i][d++]=j LayerUsedAsRefLayerFlag[j]=1 } if(dependencyFlag[i][j]) RefLayerIdx[i][r++]=j } NumDirectRefLayers[i]=d NumRefLayers[i]=r }

[0221] The variable GeneralLayerIdx[i], which specifies the layer index of the layer whose nuh_layer_id is equal to vps_layer_id[i], is derived as follows: for(i=0;i<=vps_max_layers_minus1;i++) GeneralLayerIdx[vps_layer_id[i]]=i

[0222] It is a bitstream conformance requirement that for two different values ​​of i and j ranging from 0 to vps_max_layers_minus1, both inclusive, when dependencyFlag[i][j] is equal to 1, the values ​​of chroma_format_idc and bit_depth_minus8 applied to the ith layer can be equal to the values ​​of chroma_format_idc and bit_depth_minus8 applied to the jth layer, respectively.

[0223] max_tid_ref_present_flag[i] equal to 1 specifies that the syntax element max_tid_il_ref_pics_plus1[i] is present. max_tid_ref_present_flag[i] equal to 0 specifies that the syntax element max_tid_il_ref_pics_plus1[i] is not present.

[0224] max_tid_il_ref_pics_plus1[i] equal to 0 specifies 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 specifies that pictures with TemporalId greater than max_tid_il_ref_pics_plus1[i]-1 are not used as ILRP to decode pictures of the i-th layer. If not present, the value of max_tid_il_ref_pics_plus1[i] is inferred to be equal to 7.

[0225] each_layer_is_an_ols_flag equal to 1 specifies that each OLS contains only one layer, and each layer in the CVS that references the VPS is itself an OLS with its single contained layer as its only output layer. each_layer_is_an_ols_flag equal to 0 specifies that an OLS can contain more than one layer. If vps_max_layers_minus1 is equal to 0, the value of each_layer_is_an_ols_flag is inferred to be equal to 1. Otherwise, if vps_all_independent_layers_flag is equal to 0, the value of each_layer_is_an_ols_flag is inferred to be equal to 0.

[0226] ols_mode_idc equal to 0 specifies 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 from 0 to i, inclusive, and for each OLS, only the top layer of the OLS is output.

[0227] ols_mode_idc equal to 1 specifies that the total number of OLSs specified by the VPS is equal to vps_max_layers_minus1+1, where the i-th OLS contains layers with layer indices from 0 to i, inclusive, and for each OLS, all layers in the OLS are output.

[0228] ols_mode_idc equal to 2 specifies that the total number of OLSs specified by the VPS is explicitly signaled, the output layer for each OLS is explicitly signaled, and other layers are layers that are direct or indirect reference layers of the output layer of the OLS.

[0229] The value of ols_mode_idc may be in the range 0 to 2 inclusive. The value 3 of ols_mode_idc is reserved for future use by ITU-T|ISO / IEC.

[0230] 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 is inferred to be equal to 2.

[0231] num_output_layer_sets_minus1 plus 1 specifies the total number of OLSs specified by the VPS if ols_mode_idc is equal to 2.

[0232] The variable TotalNumOlss, which specifies the total number of OLSs specified by the VPS, is derived as follows: if(vps_max_layers_minus1==0) TotalNumOlss=1 else if(each_layer_is_an_ols_flag||ols_mode_idc==0||ols_mode_idc==1) TotalNumOlss=vps_max_layers_minus1+1 else if(ols_mode_idc==2) TotalNumOlss=num_output_layer_sets_minus1+1

[0233] ols_output_layer_flag[i][j] equal to 1 specifies 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 specifies 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.

[0234] The variable NumOutputLayersInOls[i] that specifies the number of output layers in the i-th OLS, the variable NumSubLayersInLayerInOLS[i][j] that specifies the number of sublayers in the j-th layer in the i-th OLS, the variable OutputLayerIdInOls[i][j] that specifies the nuh_layer_id value of the j-th output layer in the i-th OLS, and the variable LayerUsedAsOutputLayerFlag[k] that specifies whether the k-th layer is used as an output layer in at least one OLS are derived as follows: NumOutputLayersInOls[0]=1 OutputLayerIdInOls[0][0]=vps_layer_id[0] NumSubLayersInLayerInOLS[0][0]=vps_max_sub_layers_minus1+1 LayerUsedAsOutputLayerFlag[0]=1 for(i=1,i<=vps_max_layers_minus1;i++){ if(each_layer_is_an_ols_flag||ols_mode_idc<2) LayerUsedAsOutputLayerFlag[i]=1 else / *(!each_layer_is_an_ols_flag&&ols_mode_idc==2)* / LayerUsedAsOutputLayerFlag[i]=0 } for(i=1;i <TotalNumOlss;i++) if(each_layer_is_an_ols_flag||ols_mode_idc==0){ NumOutputLayersInOls[i]=1 OutputLayerIdInOls[i][0]=vps_layer_id[i] for(j=0;j <i&&(ols_mode_idc==0);j++) NumSubLayersInLayerInOLS[i][j]=max_tid_il_ref_pics_plus1[i] NumSubLayersInLayerInOLS[i][i]=vps_max_sub_layers_minus1+1 }else if(ols_mode_idc==1){ NumOutputLayersInOls[i]=i+1 for(j=0;j<NumOutputLayersInOls[i];j++){ OutputLayerIdInOls[i][j]=vps_layer_id[j] NumSubLayersInLayerInOLS[i][j]=vps_max_sub_layers_minus1+1 } }else if(ols_mode_idc==2){ for(j=0;j<=vps_max_layers_minus1;j++){ layerIncludedInOlsFlag[i][j]=0 NumSubLayersInLayerInOLS[i][j]=0 } for(k=0,j=0;k<=vps_max_layers_minus1;k++) if(ols_output_layer_flag[i][k]){ layerIncludedInOlsFlag[i][k]=1 LayerUsedAsOutputLayerFlag[k]=1 OutputLayerIdx[i][j]=k OutputLayerIdInOls[i][j++]=vps_layer_id[k] NumSubLayersInLayerInOLS[i][j]=vps_max_sub_layers_minus1+1 } NumOutputLayersInOls[i]=j for(j=0;j <NumOutputLayersInOls[i];j++){ idx=OutputLayerIdx[i][j] for(k=0;k <NumRefLayers[idx];k++){ layerIncludedInOlsFlag[i][RefLayerIdx[idx][k ]]=1 if(NumSubLayersInLayerInOLS[i][RefLayerIdx[idx][k ]]< max_tid_il_ref_pics_plus1[OutputLayerIdInOls[i][j]]) NumSubLayersInLayerInOLS[i][RefLayerIdx[idx][k ]]= max_tid_il_ref_pics_plus1[OutputLayerIdInOls[i][j]] } } }

[0235] For each value of i in the range from 0 to vps_max_layers_minus1, inclusive, the values ​​of LayerUsedAsRefLayerFlag[i] and LayerUsedAsOutputLayerFlag[i] may not both be equal to 0. In other words, there may be no layers that are neither the output layer of at least one OLS nor a direct reference layer of another layer.

[0236] For each OLS, there may be at least one layer that is the output layer. In other words, for any value of i in the range from 0 to TotalNumOlss-1, inclusive, the value of NumOutputLayersInOls[i] may be greater than or equal to 1.

[0237] The variable NumLayersInOls[i] that specifies the number of layers in the i-th OLS and the variable LayerIdInOls[i][j] that specifies the nuh_layer_id value of the j-th layer in the i-th OLS are derived as follows. NumLayersInOls[0]=1 LayerIdInOls[0][0]=vps_layer_id[0] for(i=1;i <TotalNumOlss;i++){ if(each_layer_is_an_ols_flag){ NumLayersInOls[i]=1 LayerIdInOls[i][0]=vps_layer_id[i] }else if(ols_mode_idc==0||ols_mode_idc==1){ NumLayersInOls[i]=i+1 for(j=0;j <NumLayersInOls[i];j++) LayerIdInOls[i][j]=vps_layer_id[j] }else if(ols_mode_idc==2){ for(k=0,j=0;k<=vps_max_layers_minus1;k++) if(layerIncludedInOlsFlag[i][k]) LayerIdInOls[i][j++]=vps_layer_id[k] NumLayersInOls[i]=j } }

[0238] The variable OlsLayerIdx[i][j], which specifies the OLS layer index of the layer whose nuh_layer_id is equal to LayerIdInOls[i][j], is derived as follows: for(i=0;i <TotalNumOlss;i++) for j=0;j <NumLayersInOls[i];j++) OlsLayerIdx[i][LayerIdInOls[i][j]]=j

[0239] The lowest layer of each OLS may be an independent layer. In other words, for each i in the range 0 to TotalNumOlss-1, inclusive, the value of vps_independent_layer_flag[GeneralLayerIdx[LayerIdInOls[i][0]]] may be equal to 1.

[0240] Each layer may be included in at least one OLS specified by the VPS. In other words, for each layer for which a particular value of nuh_layer_id nuhLayerId is 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 NumLayersInOls[i]-1 inclusive, such that the value of LayerIdInOls[i][j] is equal to nuhLayerId.

[0241] In one embodiment, the decoding process operates as follows for the current picture CurrPic: PictureOutputFlag is set as follows: If any of the following conditions are true, PictureOutputFlag is set to 0; Otherwise, PictureOutputFlag is set equal to pic_output_flag: - The current image is a RASL image and the associated IRAP image's NoOutputBeforeRecoveryFlag is 1. -gdr_enabled_flag is equal to 1 and the current image is a GDR image with NoOutputBeforeRecoveryFlag equal to 1. - gdr_enabled_flag is equal to 1, the current image is associated with a GDR image that has NoOutputBeforeRecoveryFlag equal to 1, and the current image's PicOrderCntVal is less than the associated GDR image's RpPicOrderCntVal. - sps_video_parameter_set_id is greater than 0, ols_mode_idc is equal to 0, and the current AU contains an image picA that satisfies all of the following conditions: - PicA has PictureOutputFlag equal to 1. -PicA has a larger nuh_layer_id nuhLid than the current image. -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.

[0242] After all slices of the current picture have been decoded, the current decoded picture is marked as "used for short-term reference" and each ILRP entry in RefPicList[0] or RefPicList[1] is marked as "used for short-term reference".

[0243] In the same or another embodiment, if each layer is an output layer set, PictureOutputFlag is set equal to pic_output_flag, regardless of the value of ols_mode_idc.

[0244] In the same or another embodiment, PictureOutputFlag is set to 0 if sps_video_parameter_set_id is greater than 0, each_layer_is_an_ols_flag is equal to 0, ols_mode_idc is equal to 0, and the current AU contains an image picA that satisfies all of the following conditions: PicA has PictureOutputFlag equal to 1, PicA has a nuh_layer_id nuhLid greater than the current image, and PicA belongs to an output layer of OLS (i.e., OutputLayerIdInOls[TargetOlsIdx][0] is equal to nuhLid).

[0245] In the same or another embodiment, 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, then PictureOutputFlag is set equal to 0.

[0246] Reference image resampling allows adaptive resolution changes within a coded (layered) video sequence, as well as inter-layer spatial scalability where there are dependencies between layers belonging to the same output layer set.

[0247] In one embodiment, sps_ref_pic_resampling_enabled_flag is signaled in a parameter set (e.g., a sequence parameter set) as shown in Figure 24. The flag sps_ref_pic_resampling_enabled_flag indicates whether reference picture resampling is used for adaptive resolution changes or inter-layer spatial scalability in a coded video sequence that references an SPS. sps_ref_pic_resampling_enabled_flag equal to 1 specifies that reference picture resampling is enabled and one or more image slices in the CLVS reference reference pictures of different spatial resolutions in active entries of the reference picture list. sps_ref_pic_resampling_enabled_flag equal to 0 specifies that reference picture resampling is disabled and no slices of images in the CLVS reference reference pictures with different spatial resolutions in active entries of the reference picture list.

[0248] In the same or another embodiment, if sps_ref_pic_resampling_enabled_flag is equal to 1, for the current picture, the reference picture with a different spatial resolution belongs either to the same layer as the layer containing the current picture or to a different layer.

[0249] In another embodiment, sps_ref_pic_resampling_enabled_flag equal to 1 specifies that reference image resampling is enabled and one or more slices of an image in the CLVS reference a reference image with a different spatial resolution or a different scaling window in an active entry of the reference image list. sps_ref_pic_resampling_enabled_flag equal to 0 specifies that reference image resampling is disabled and no slices of an image in the CLVS reference a reference image with a different spatial resolution or a different scaling window in an active entry of the reference image list.

[0250] In the same or another embodiment, sps_ref_pic_resampling_enabled_flag equal to 1 indicates that, for the current picture, a reference picture with a different spatial resolution or a different scaling window belongs either to the same layer as the layer containing the current picture, or to a different layer.

[0251] In the same or another embodiment, sps_res_change_in_clvs_allowed_flag indicates whether image resolution may be changed in a CLVS or a CVS. sps_res_change_in_clvs_allowed_flag equal to 1 specifies that the spatial resolution of an image may change in a CLVS that references an SPS. sps_res_change_in_clvs_allowed_flag equal to 0 specifies that the spatial resolution of an image may not change in a CLVS that references an SPS. If not present, the value of sps_res_change_in_clvs_allowed_flag is inferred to be equal to 0.

[0252] In the same or another 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 image resampling can be used for spatial scalability only, not adaptive resolution changes in CLVS.

[0253] In the same or another 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 image resampling can be used for both spatial scalability and adaptive resolution change in CLVS.

[0254] 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, then pps_scaling_window_explicit_signalling_flag may be equal to 1. This means that if the image resolution is constant in CLVs or CVS and reference picture resampling is used, the scaling window parameter must be explicitly signaled instead of inferring its value from the adaptation window parameter.

[0255] In one embodiment, the sps_virtual_boundaries_present_flag is signaled in the SPS as shown in Figure 24. The flag sps_virtual_boundaries_present_flag indicates whether virtual boundary information is signaled in the SPS.

[0256] In the same or another embodiment, sps_virtual_boundaries_present_flag is conditionally signaled only if sps_res_change_in_clvs_allowed_flag is equal to 0, since virtual boundary information may not be signaled in the SPS if reference image resampling is used.

[0257] In the same embodiment, sps_virtual_boundaries_present_flag equal to 1 specifies that virtual boundary information is signaled in the SPS. sps_virtual_boundaries_present_flag equal to 0 specifies that virtual boundary information is not signaled in the SPS. If there are one or more virtual boundaries signaled in the SPS, in-loop filtering operations across the virtual boundaries of the images that reference the SPS are disabled. 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 is inferred to be equal to 0.

[0258] In one embodiment, sps_subpic_info_present_flag is signaled in the SPS as shown in Figure 24. The flag sps_subpic_info_present_flag indicates whether the sub-picture split information is signaled in the SPS.

[0259] In the same or another embodiment, sps_subpic_info_present_flag is conditionally signaled only if sps_res_change_in_clvs_allowed_flag is equal to 0, since subpicture splitting information may not be signaled in the SPS when reference picture resampling is used.

[0260] In the same embodiment, sps_subpic_info_present_flag equal to 1 specifies that subpicture information is present for the CLVS and that there may be one or more subpictures for each image in the CLVS. sps_subpic_info_present_flag equal to 0 specifies that subpicture information is not present for the CLVS and that there is only one subpicture for each image in the CLVS. If not present, the value of sps_subpic_info_present_flag is inferred to be equal to 0.

[0261] In one embodiment, pps_res_change_in_clvs_allowed_flag may be signaled in a PPS as shown in Figure 25. The value of pps_res_change_in_clvs_allowed_flag of a PPS may be the same as the value of sps_res_change_in_clvs_allowed_flag of an SPS referenced by the PPS.

[0262] In the same embodiment, image width and height information may be signaled in the PPS only if the value of pps_res_change_in_clvs_allowed_flag is equal to 1. If pps_res_change_in_clvs_allowed_flag is equal to 0, the image width and height values ​​are inferred to be equal to the maximum image width and height values ​​signaled in the SPS.

[0263] In the same embodiment, pps_pic_width_in_luma_samples specifies the width of each decoded picture referencing the PPS in units of luma samples. pps_pic_width_in_luma_samples may not be equal to 0, may be an integer multiple of Max(8, MinCbSizeY), and may 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 is inferred to be equal to sps_pic_width_max_in_luma_samples. If sps_ref_wraparound_enabled_flag is equal to 1, the value of (CtbSizeY / MinCbSizeY+1) may be less than or equal to (pps_pic_width_in_luma_samples / MinCbSizeY-1). pps_pic_height_in_luma_samples specifies the height of each decoded picture referencing the PPS in units of luma samples. pps_pic_height_in_luma_samples may not be equal to 0, may be an integer multiple of Max(8, MinCbSizeY), and may 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 is inferred to be equal to sps_pic_height_max_in_luma_samples.

[0264] In the reference picture list, all active reference pictures for an image have the same sub-image layout as the image itself, and all active reference pictures are inter-layer reference pictures with a single sub-image.

[0265] In the same or another embodiment, the image referenced by each active entry in RefPicList[0] or RefPicList[1] has the same image size and the same sub-image layout as the current image (i.e., the SPSs referenced by that image and the current image have the same value of sps_num_subpics_minus1 and the same values ​​of sps_subpic_ctu_top_left_x[j], sps_subpic_ctu_top_left_y[j], sps_subpic_width_minus1[j], and sps_subpic_height_minus1[j], for each value of j in the range 0 to sps_num_subpics_minus1, inclusive). The image referenced by each active entry in RefPicList[0] or RefPicList[1] is an ILRP with a value of sps_num_subpics_minus1 equal to 0.

[0266] In the same or another embodiment, if sps_num_subpics_minus1 is greater than 0 and sps_subpic_treated_as_pic_flag[i] is equal to 1, then for each CLVS of the current layer that references an SPS, let targetAuSet be all AUs, inclusive, starting from the AU containing the first picture of the CLVS in decoding order to the AU containing the last picture of the CLVS in decoding order. It is a requirement of bitstream conformance that for targetLayerSet consisting of the current layer and all layers that have the current layer as a reference layer, all of the following conditions are true: - For each AU in targetAuSet, all images of layers in targetLayerSet may have the same value of pps_pic_width_in_luma_samples and the same value of pps_pic_height_in_luma_samples. In the -targetLayerSet, all SPSs referenced by layers that have the current layer as a reference layer may have the same value of sps_num_subpics_minus1, and for each value of j in the range from 0 to sps_num_subpics_minus1, inclusive, may have the same values ​​of sps_subpic_ctu_top_left_x[j], sps_subpic_ctu_top_left_y[j], sps_subpic_width_minus1[j], sps_subpic_height_minus1[j], and sps_subpic_treated_as_pic_flag[j]. - For each AU in targetAuSet, all images of layers that have the current layer in targetLayerSet as a reference layer may have the same value of SubpicIdVal[j] for each value of j ranging from 0 to sps_num_subpics_minus1 inclusive.

[0267] In the same or another embodiment, pps_scaling_win_left_offset, pps_scaling_win_right_offset, pps_scaling_win_top_offset, and pps_scaling_win_bottom_offset specify offsets applied to the image size for scaling ratio calculation. If not present, the values ​​of pps_scaling_win_left_offset, pps_scaling_win_right_offset, pps_scaling_win_top_offset, and pps_scaling_win_bottom_offset are inferred to be equal to pps_conf_win_left_offset, pps_conf_win_right_offset, pps_conf_win_top_offset, and pps_conf_win_bottom_offset, respectively.

[0268] The value of SubWidthC*(Abs(pps_scaling_win_left_offset)+Abs(pps_scaling_win_right_offset)) may be less than pps_pic_width_in_luma_samples, and the value of SubHeightC*(Abs(pps_scaling_win_top_offset)+Abs(pps_scaling_win_bottom_offset)) may be less than pps_pic_height_in_luma_samples.

[0269] The variables CurrPicScalWinWidthL and CurrPicScalWinHeightL are derived as follows: CurrPicScalWinWidthL=pps_pic_width_in_luma_samples- SubWidthC*(pps_scaling_win_right_offset+pps_scaling_win_left_offset) CurrPicScalWinHeightL=pps_pic_height_in_luma_samples- SubHeightC*(pps_scaling_win_bottom_offset+pps_scaling_win_top_offset)

[0270] Let refPicScalWinWidthL and refPicScalWinHeightL be the CurrPicScalWinWidthL and CurrPicScalWinHeightL of the reference image of the current image that refers to this PPS. It is a requirement for bitstream conformance that all of the following conditions are met: -currPicScalWinWidthL*2 is greater than or equal to refPicScalWinWidthL. -currPicScalWinHeightL*2 is greater than or equal to refPicScalWinHeightL. -currPicScalWinWidthL is equal to or less than refPicScalWinWidthL*8. -currPicScalWinHeightL is less than or equal to refPicScalWinHeightL*8. -currPicScalWinWidthL*sps_pic_width_max_in_luma_samples is greater than or equal to refPicScalWinWidthL*(pps_pic_width_in_luma_samples-Max(8, MinCbSizeY)). -currPicScalWinHeightL*sps_pic_height_max_in_luma_samples is greater than or equal to refPicScalWinHeightL*(pps_pic_height_in_luma_samples-Max(8, MinCbSizeY)).

[0271] The value of SubWidthC*(Abs(pps_scaling_win_left_offset)+Abs(pps_scaling_win_right_offset)) may be less than pps_pic_width_in_luma_samples, and the value of SubHeightC*(Abs(pps_scaling_win_top_offset)+Abs(pps_scaling_win_bottom_offset)) may be less than pps_pic_height_in_luma_samples.

[0272] In the same or another embodiment, the value of SubWidthC*(pps_scaling_win_left_offset+pps_scaling_win_right_offset) may be greater than or equal to -pps_pic_width_in_luma_samples*15 and less than pps_pic_width_in_luma_samples, and the value of SubHeightC*(pps_scaling_win_top_offset+pps_scaling_win_bottom_offset) may be greater than or equal to -pps_pic_height_in_luma_samples*15 and less than pps_pic_height_in_luma_samples.

[0273] In the same or another embodiment, the value of SubWidthC*(pps_scaling_win_left_offset+pps_scaling_win_right_offset) may be greater than or equal to -pps_pic_width_in_luma_samples*7 and less than pps_pic_width_in_luma_samples, and the value of -SubHeightC*(pps_scaling_win_top_offset+pps_scaling_win_bottom_offset) may be greater than or equal to -pps_pic_height_in_luma_samples*7 and less than pps_pic_height_in_luma_samples.

[0274] In the same or another embodiment, when sps_ref_pic_resampling_enabled_flag is equal to 1, sps_res_change_in_clvs_allowed_flag is equal to 0, and sps_subpic_info_present_flag is equal to 1, the value of SubWidthC*(Abs(pps_scaling_win_left_offset)+Abs(pps_scaling_win_right_offset)) may be less than the minimum value of sps_subpic_width_minus1[i]+1, for i in the range from 0 to sps_num_subpics_minus1, and the value of SubHeightC*(Abs(pps_scaling_win_top_offset)+Abs(pps_scaling_win_bottom_offset)) may be less than the minimum value of sps_subpic_height_minus1[i]+1, for i in the range from 0 to sps_num_subpics_minus1.

[0275] In the same or another embodiment, if the value of the current layer sps_res_change_in_clvs_allowed_flag is equal to 1, the value of sps_subpic_info_present_flag may be equal to 0.

[0276] In the same or another embodiment, if the value of sps_res_change_in_clvs_allowed_flag of the current layer is equal to 1, the value of sps_subpic_info_present_flag of the layer that references the current layer may be equal to 0.

[0277] In the same or another embodiment, if the value of sps_res_change_in_clvs_allowed_flag of the current layer is equal to 1, the value of sps_subpic_info_present_flag of the current layer and all layers that reference the current layer may be equal to 0.

[0278] In the same or another embodiment, if the value of sps_subpic_info_present_flag of the current layer may be equal to 1, the value of sps_res_change_in_clvs_allowed_flag of the current layer may be equal to 0.

[0279] In the same or another embodiment, if the value of sps_subpic_info_present_flag of the current layer may be equal to 1, the value of sps_res_change_in_clvs_allowed_flag of the reference layer of the current layer may be equal to 0.

[0280] In the same or another embodiment, if the value of sps_subpic_info_present_flag of the current layer may be equal to 1, the value of sps_res_change_in_clvs_allowed_flag of the current layer and all reference layers of the current layer may be equal to 0.

[0281] In the same or another embodiment, if the value of sps_subpic_info_present_flag of the current layer may be equal to 1 and the value of sps_ref_pic_resampling_enabled_flag of the reference layer of the current layer may be equal to 1.

[0282] In one embodiment, a coded image in layer k may be divided into one or more sub-images, and may refer to one or more reference images in the same layer, or to one or more reference images in a reference layer of layer k, as shown in Figure 26. In the example of Figure 26, if the value of sps_ref_pic_resampling_enabled_flag (in Figure 24) is equal to 1, the current image and each reference image may have different scaling windows, even if the image sizes are the same.

[0283] In the same or another embodiment, when a subimage is extracted, the size and offset value of the scaling window used in the scaling ratio calculation for the reference image resampling may be updated according to the size and position of the subimage. When the size and offset value of the scaling window of the current image are updated, the size and offset value of the scaling window of one or more reference images of the current image may be updated accordingly. Figure 27 shows an example of updating the scaling windows of a reference image in the same layer and an inter-layer reference image in a different layer.

[0284] In the same or another embodiment, if an image in layer k is divided into one or more sub-images with the same division layout, an image in another layer that layer k references as a reference layer may not be divided into multiple sub-images.

[0285] In the same or another embodiment, when the scaling window size and offset values ​​are updated in the example of FIG. 27, the scaling window size may be rescaled in relation to the scaling ratio between the original image size and the extracted sub-image size. When the scaling window size is updated, depending on the original image size and the sub-image size, the updated scaling window size may have fractional pixel values ​​that cannot be represented by the scaling window offset values ​​(pps_scaling_win_left_offset, pps_scaling_win_right_offset, pps_scaling_win_top_offset, pps_scaling_win_bottom_offset) signaled in the PPS, as shown in FIG. 25. Furthermore, this approach may update all scaling offset values ​​of the reference image, which is a significant overhead.

[0286] In the same or another embodiment, as shown in FIG. 28, when a sub-image is extracted, in order to signal the same scaling ratio between the current image and the reference image, the size of the scaling window may not be changed compared to the original scaling window before extraction, but only the position of the scaling window is shifted by updating the values ​​of the scaling window offset values ​​(pps_scaling_win_left_offset, pps_scaling_win_right_offset, pps_scaling_win_top_offset, pps_scaling_win_bottom_offset) signaled in the PPS.

[0287] In the same embodiment, if the offset values ​​of the scaling window of the original image are orgScalingWinLeft, orgScalingWinRight, orgScalingWinTop, orgScalingWinBottom, which are equal to the values ​​of pps_scaling_win_left_offset, pps_scaling_win_right_offset, pps_scaling_win_top_offset, and pps_scaling_win_bottom_offset of the original image, respectively, the position and size of the extracted sub-image are represented by SubpicLeftBoundaryPos, SubpicRightBoundaryPos, SubpicTopBoundaryPos, SubpicBotBoundaryPos, where these values ​​are derived as follows: SubpicLeftBoundaryPos=sps_subpic_ctu_top_left_x[CurrSubpicIdx]*CtbSizeY SubpicRightBoundaryPos=Min(sps_pic_width_max_in_luma_samples-1, (sps_subpic_ctu_top_left_x[CurrSubpicIdx]+ sps_subpic_width_minus1[CurrSubpicIdx]+1)*CtbSizeY-1) SubpicTopBoundaryPos=sps_subpic_ctu_top_left_y[CurrSubpicIdx]*CtbSizeY SubpicBotBoundaryPos=Min(sps_pic_height_max_in_luma_samples-1 (sps_subpic_ctu_top_left_y[CurrSubpicIdx]+ sps_subpic_height_minus1[CurrSubpicIdx]+1)*CtbSizeY-1)

[0288] The values ​​of pps_scaling_win_left_offset, pps_scaling_win_right_offset, pps_scaling_win_top_offset, and pps_scaling_win_bottom_offset for the extracted sub-image are derived as follows: pps_scaling_win_left_offset=orgScalingWinLeft-(SubpicLeftBoundaryPos / SubWidthC); pps_scaling_win_right_offset=orgScalingWinRight-(SubpicLeftBoundaryPos / SubWidthC); pps_scaling_win_top_offset=orgScalingWinTop-(SubpicTopBoundaryPos / SubWidthC); pps_scaling_win_bottom_offset=orgScalingWinBottom-(SubpicTopBoundaryPos / SubWidthC).

[0289] In the same or another embodiment, the sub-picture sub-bitstream extraction process is as follows: The inputs to this process are the bitstream inBitstream, the target OLS index targetOlsIdx, the target highest TemporalId value tIdTarget, and the array of target sub-picture index values ​​for each layer subpicIdxTarget[]. The output of this process is the sub-bitstream outBitstream.

[0290] The requirement for bitstream conformance with respect to an input bitstream is that an output sub-bitstream that satisfies all of the following conditions is a conforming bitstream: An output sub-bitstream is the output of the process specified in this section that takes as input the bitstream, targetOlsIdx equal to an index into the list of OLSs specified by the VPS, and subpicIdxTarget[] equal to a subpicture index present in the OLS. An output sub-bitstream contains at least one VCL NAL unit with nuh_layer_id equal to each of the nuh_layer_id values ​​in LayerIdInOls[targetOlsIdx]. An output sub-bitstream contains at least one VCL NAL unit with TemporalId equal to tIdTarget. A conforming bitstream contains one or more coded slice NAL units with TemporalId equal to 0, but is not required to contain any coded slice NAL units with nuh_layer_id equal to 0. The output sub-bitstream contains at least one VCL NAL unit whose nuh_layer_id is equal to LayerIdInOls[targetOlsIdx][i] and whose sh_subpic_id is equal to the value of SubpicIdVal[subpicIdxTarget[i]], for each i in the range from 0 to NumLayersInOls[targetOlsIdx]-1, inclusive.

[0291] The output sub-bitstream outBitstream is derived as follows: the sub-bitstream extraction process is invoked with inBitstream, targetOlsIdx, and tIdTarget as inputs, and the output of the process is assigned to outBitstream. If some external means not specified here are available to provide replacement parameter sets for the sub-bitstream outBitstream, replace all parameter sets with the replacement parameter sets.

[0292] Otherwise, if a Subpicture Level Information SEI message is present in inBitstream, the following applies: The variable subpicIdx is set equal to the value of subpicIdxTarget[[NumLayersInOls[targetOlsIdx]-1]]. Rewrite the value of general_level_idc of the vps_ols_ptl_idx[targetOlsIdx]th entry of the list of profile_tier_level() syntax structures of all referenced VPS NAL units to be equal to SubpicLevelIdc for the set of subpics consisting of the subpictures with subpicture index equal to subpicIdx. If VCL HRD parameters or NAL HRD parameters exist, rewrite the values ​​of cpb_size_value_minus1[tIdTarget][j] and bit_rate_value_minus1[tIdTarget][j] of the jth CPB in the vps_ols_hrd_idx[MultiLayerOlsIdx[targetOlsIdx]]-th ols_hrd_parameters() syntax structure in all referenced VPS NAL units and in the ols_hrd_parameters() syntax structure in all SPS NAL units referenced by the ith layer so that they correspond to SubpicCpbSizeVcl[SubpicSetLevelIdx][subpicIdx] and SubpicCpbSizeNal[SubpicSetLevelIdx][subpicIdx], respectively.

[0293] SubpicBitrateVcl[SubpicSetLevelIdx][subpicIdx] and SubpicBitrateNal[SubpicSetLevelIdx][subpicIdx] for the subpicture whose subpicture index is equal to subpicIdx, j ranges from 0 to hrd_cpb_cnt_minus1 inclusive, and i ranges from 0 to NumLayersInOls[targetOlsIdx]-1 inclusive.

[0294] For the ith layer, where i ranges from 0 to NumLayersInOls[targetOlsIdx]-1, the following applies: The variable subpicIdx is set equal to the value of subpicIdxTarget[i]. The value of general_level_idc in the profile_tier_level() syntax structure of all referenced SPS NAL units with sps_ptl_dpb_hrd_params_present_flag equal to 1 is rewritten to be equal to SubpicLevelIdc for the set of subpics consisting of the subpictures with subpicture index equal to subpicIdx.

[0295] The variables subpicWidthInLumaSamples and subpicHeightInLumaSamples are derived as follows: subpicWidthInLumaSamples=min((sps_subpic_ctu_top_left_x[subpicIdx]+ sps_subpic_width_minus1[subpicIdx]+1)*CtbSizeY,pps_pic_width_in_luma_samples)- sps_subpic_ctu_top_left_x[subpicIdx]*CtbSizeY subpicHeightInLumaSamples=min((sps_subpic_ctu_top_left_y[subpicIdx]+ sps_subpic_height_minus1[subpicIdx]+1)*CtbSizeY,pps_pic_height_in_luma_samples)- sps_subpic_ctu_top_left_y[subpicIdx]*CtbSizeY

[0296] Rewrite the values ​​of sps_pic_width_max_in_luma_samples and sps_pic_height_max_in_luma_samples in all referenced SPS NAL units and the values ​​of pps_pic_width_in_luma_samples and pps_pic_height_in_luma_samples in all referenced PPS NAL units to be equal to subpicWidthInLumaSample and subpicHeightInLumaSamples, respectively. Rewrite the values ​​of sps_num_subpics_minus1 in all referenced SPS NAL units and the values ​​of pps_num_subpics_minus1 in all referenced PPS NAL units to 0. Rewrite the syntax elements sps_subpic_ctu_top_left_x[subpicIdx] and sps_subpic_ctu_top_left_y[subpicIdx] to 0 in all referenced SPS NAL units, if they exist. In all referenced SPS NAL units, for each j not equal to subpicIdx, remove the syntax elements sps_subpic_ctu_top_left_x[j], sps_subpic_ctu_top_left_y[j], sps_subpic_width_minus1[j], sps_subpic_height_minus1[j], sps_subpic_treated_as_pic_flag[j], sps_loop_filter_across_subpic_enabled_flag[j], and sps_subpic_id[j]. Rewrite all referenced PPS syntax elements for tile and slice signaling, removing all tile rows, tile columns, and slices that are not associated with a subpicture whose subpicture index is equal to subpicIdx.

[0297] The variables subpicConfWinLeftOffset, subpicConfWinRightOffset, subpicConfWinTopOffset, and subpicConfWinBottomOffset are derived as follows. subpicConfWinLeftOffset = sps_subpic_ctu_top_left_x[subpicIdx] == 0 sps_conf_win_left_offset: 0 subpicConfWinRightOffset = (sps_subpic_ctu_top_left_x[subpicIdx] + sps_subpic_width_minus1[subpicIdx] + 1) * CtbSizeY >= sps_pic_width_max_in_luma_samples sps_conf_win_right_offset: 0 subpicConfWinTopOffset = sps_subpic_ctu_top_left_y[subpicIdx] == 0 sps_conf_win_top_offset: 0 subpicConfWinBottomOffset = (sps_subpic_ctu_top_left_y[subpicIdx] + sps_subpic_height_minus1[subpicIdx] + 1) * CtbSizeY >= sps_pic_height_max_in_luma_samples sps_conf_win_bottom_offset: 0

[0298] Rewrite the values ​​of sps_conf_win_left_offset, sps_conf_win_right_offset, sps_conf_win_top_offset, and sps_conf_win_bottom_offset of all referenced SPS NAL units and the values ​​of pps_conf_win_left_offset, pps_conf_win_right_offset, pps_conf_win_top_offset, and pps_conf_win_bottom_offset of all referenced PPS NAL units to be equal to subpicConfWinLeftOffset, subpicConfWinRightOffset, subpicConfWinTopOffset, and subpicConfWinBottomOffset, respectively. Rewrite the values ​​of pps_scaling_win_left_offset, pps_scaling_win_right_offset, pps_scaling_win_top_offset, and pps_scaling_win_bottom_offset as follows: pps_scaling_win_left_offset=orgScalingWinLeft-(SubpicLeftBoundaryPos / SubWidthC) pps_scaling_win_right_offset=orgScalingWinRight-(SubpicLeftBoundaryPos / SubWidthC) pps_scaling_win_top_offset=orgScalingWinTop-(SubpicTopBoundaryPos / SubWidthC) pps_scaling_win_bottom_offset=orgScalingWinBottom-(SubpicTopBoundaryPos / SubWidthC), where orgScalingWinLeft, orgScalingWinRight, orgScalingWinTop, and orgScalingWinBottom are equal to the values ​​of pps_scaling_win_left_offset, pps_scaling_win_right_offset, pps_scaling_win_top_offset, and pps_scaling_win_bottom_offset of the original coded picture. Remove from outBitstream all VCL NAL units whose nuh_layer_id is equal to the nuh_layer_id of the ith layer and whose sh_subpic_id is not equal to SubpicIdVal[subpicIdx].

[0299] If sli_cbr_constraint_flag is equal to 1, remove all NAL units whose nal_unit_type is equal to FD_NUT and filler payload SEI messages that are not associated with VCL NAL units of subpicIdTarget[], and set cbr_flag[tIdTarget][j] of the j-th CPB to 1, where j is in the range from 0 to hrd_cpb_cnt_minus1, in the vps_ols_hrd_idx[MultiLayerOlsIdx[targetOlsIdx]]-th ols_hrd_parameters() syntax structure of all referenced VPS NAL units and SPS NAL units. Otherwise (sli_cbr_constraint_flag is equal to 0), remove all NAL units whose nal_unit_type is equal to FD_NUT and filler payload SEI messages, and set cbr_flag[tIdTarget][j] to 0.

[0300] If outBitstream contains an SEI NAL unit that contains a scalable nesting SEI message applicable to outBitstream with sn_ols_flag equal to 1 and sn_subpic_flag equal to 1, extract the appropriate non-scalable nesting SEI message with payloadType equal to 1 (PT), 130 (DUI), or 132 (decoded image hash) from the scalable nesting SEI message and place the extracted SEI message in outBitstream.

[0301] Some embodiments may relate to systems, methods, and / or computer-readable media at any possible level of technical detail. The computer-readable media may include computer-readable non-transitory storage media having computer-readable program instructions for causing a processor to perform operations.

[0302] A computer-readable storage medium may be a tangible device capable of retaining and storing instructions for use by an instruction-execution device. A computer-readable storage medium may be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of computer-readable storage media includes portable computer diskettes, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disk read-only memory (CD-ROM), digital versatile disks (DVD), memory sticks, floppy disks, punch cards, or mechanically encoded devices such as ridge structures in grooves with instructions recorded thereon, and any suitable combination of the foregoing. Computer-readable storage media as used herein should not be construed as being ephemeral signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission medium (e.g., light pulses passing through fiber optic cable), or electrical signals transmitted through wires.

[0303] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device or to an external computer or storage device over a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network may include copper transmission cables, fiber optic transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium within the respective computing / processing device.

[0304] The computer-readable program code / instructions for carrying out operations may be either source code or object code written in any combination of one or more programming languages, including assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, integrated circuit configuration data, or object-oriented programming languages ​​such as Smalltalk®, C++, and procedural programming languages ​​such as the "C" programming language, or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA) can execute computer-readable program instructions by utilizing state information of the computer-readable program instructions to personalize the electronic circuitry to perform an aspect or operation.

[0305] These computer-readable program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus to produce a machine such that the instructions, executed by the processor of the computer or other programmable data processing apparatus, create means for performing the functions / acts specified in the flowchart and / or block diagram blocks. These computer-readable program instructions can also be stored on a computer-readable storage medium that can direct a computer, programmable data processing apparatus, and / or other device to function in a particular manner, such that the computer-readable storage medium having instructions stored therein comprises an article of manufacture containing instructions that implement aspects of the functions / acts specified in the flowchart and / or block diagram blocks.

[0306] The computer-readable program instructions may be loaded into a computer, other programmable data processing apparatus, or other device and cause a series of operational steps to be performed on the computer, other programmable apparatus, or other device, such that the instructions executing on the computer, other programmable apparatus, or other device perform the functions / acts specified in the flowchart and / or block diagram blocks, to create a computer-implemented process.

[0307] The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer-readable media according to various embodiments. In this regard, each block in the flowcharts or block diagrams may represent a module, segment, or portion of instructions that make up one or more executable instructions for implementing the specified logical function(s). The methods, computer systems, and computer-readable media may include additional, fewer, different, or differently arranged blocks than depicted in the figures. In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may actually be executed concurrently or substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending on the functionality involved. It should also be noted that each block of the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented by dedicated hardware-based systems that perform the specified functions or acts or execute a combination of dedicated hardware and computer instructions.

[0308] It will be apparent that the systems and / or methods described herein may be implemented in different forms of hardware, firmware, or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and / or methods is not intended to limit the implementation. Thus, although the operation and behavior of the systems and / or methods are described herein without reference to specific software code, it will be understood that software and hardware can be designed to implement the systems and / or methods based on the description herein.

[0309] No element, act, or instruction used herein should be construed as critical or required unless explicitly described as such. Also, as used herein, the articles "a" and "an" are intended to include one or more items and may be used interchangeably with "one or more." Furthermore, as used herein, the term "set" is intended to include one or more items (e.g., related items, unrelated items, combinations of related and unrelated items, etc.) and may be used interchangeably with "one or more." Where only one item is intended, the term "one" or similar language is used. Also, as used herein, terms such as "has," "have," and "having" are intended to be open-ended terms. Furthermore, the phrase "based on" is intended to mean "based at least in part on," unless otherwise specified.

[0310] The descriptions of various aspects and embodiments are presented for illustrative purposes but are not intended to be exhaustive or limited to the disclosed embodiments. Although combinations of features are recited in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure of possible implementations. Indeed, many of these features can be combined in ways not specifically recited in the claims and / or disclosed in the specification. While each dependent claim listed below may depend directly on only one claim, the disclosure of possible implementations includes each dependent claim in combination with all other claims in the claim set. Many modifications and variations will be apparent to those skilled in the art without departing from the scope of the described embodiments. The terminology used herein was selected to best explain the principles of the embodiments, practical applications, or technical improvements over technologies found in the marketplace, or to enable those skilled in the art to understand the embodiments disclosed herein. [Explanation of symbols]

[0311] 100 Communication Systems 110 Terminal 120 terminals 130 terminals 140 terminals 150 Communication Network 201 Video Sources, Cameras 202 Data Stream 203 Encoder 204 Video Bitstream 205 Streaming Server 206 Streaming Client 207 Copy Video Bitstream 208 Streaming Client 209 Copy Video Bitstream 210 decoder 211 video sample streams 212 Display, Rendering Devices 213 Capture Subsystem 310 receiver 312 channels 315 Buffer Memory 320 parser, video decoder 321 Symbol 351 Scaler / Descaler Unit 352 Inter-image prediction unit, intra-prediction unit 353 Motion Compensation Prediction Unit 355 Aggregator 356 Current Image or Loop Filter Unit 357 Reference Image Memory, Reference Image Buffer 430 encoder 432 encoding engine 433 Local Decoder 434 Reference Image Memory 435 Predictor 440 Transmitter 443 Video Sequences 445 Entropy Coder 450 Controller 460 Communication Channels 501 Image Header 502 ARC information 504 Image Parameter Sets 505 ARC Reference Information 506 Table 507 Sequence Parameter Set 508 Tile Group Header 509 ARC information 511 Parameter Set 512 ARC information 513 ARC Reference Information, Table 514 Tile Group Headers 515 ARC information 516 ARC Information Table, Set 601 Tile Group Header 602 Syntax Elements 603 Syntax Elements 610 Sequence Parameter Set 611 Syntax Elements 612 Parameter Set 613 Syntax Elements 614 Syntax Elements 615 Reference Image Dimension 616 Syntax Elements 617 Syntax Elements 700 Computer Systems 701 Keyboard 702 Mouse 703 Trackpad 704 Data Glove 705 Joystick 706 Microphone 707 Scanner 708 Camera 709 Speaker 710 screen 720 CD / DVD ROM / RW 721 Medium 722 thumb drive 723 Solid State Drive 740 cores 743 FPGA 741 CPU 742 GPU 743 FPGA 744 Accelerator 745 ROM 746 RAM 747 Internal Mass Storage 748 System Bus 749 Peripheral Bus

Claims

1. A method of video encoding performed by a processor, A step of generating video data having one or more sub-images, The process includes the step of generating a bitstream that includes sub-bitstreams configured to be extracted based on an array of target output layer set index, target highest time discrimination value, and target sub-image index values, and which include sub-bitstreams associated with resampling parameters and spatial scalability parameters corresponding to the sub-images, A method in which the resampling parameter and the spatial scalability parameter are used to scale the video data such that the left and right offset values ​​of the scaling window of the extracted subimage are updated based on the left boundary position of the extracted subimage, the top and bottom offset values ​​of the scaling window are updated based on the top boundary position of the extracted subimage, and the position of the scaling window is shifted based on the updated offset values.

2. The method according to claim 1, wherein the left and right offset values ​​of the scaling window and the top and bottom offset values ​​of the scaling window are updated according to the size and position of the sub-image.

3. The left and right offset values ​​of the scaling window are updated based on the width of the sub-image and the left boundary position of the sub-image. The method according to claim 1, wherein the upper and lower offset values ​​of the scaling window are updated based on the width of the sub-image and the upper boundary position of the sub-image.

4. The method according to claim 1, which enables adaptive resolution changes of the video data based on the resampling parameters.

5. The method according to claim 1, wherein the resampling parameter corresponds to one or more flags signaled in a parameter set associated with the video data.

6. The method according to claim 1, wherein the spatial scalability parameter corresponds to one or more flags signaled in a parameter set associated with the video data.

7. The method according to claim 1, wherein the resampling of the video data during encoding is disabled based on the resampling parameters.

8. A computer system for video encoding, One or more computer-readable non-transient storage media configured to store computer program code, A computer system comprising one or more computer processors configured to access the computer program code and to operate as instructed by the computer program code, wherein the computer program code is configured to cause one or more computer processors to perform the method according to any one of claims 1 to 7.

9. A computer program for video encoding, wherein the computer program is configured to cause one or more computer processors to perform the method described in any one of claims 1 to 7.

10. A method of video encoding performed by a processor, A step of generating video data having one or more sub-images, A step of generating a bitstream that includes sub-bitstreams configured to be extracted based on an array of target output layer set index, target highest time discrimination value, and target sub-image index values, and which include sub-bitstreams associated with resampling parameters and spatial scalability parameters corresponding to the sub-images, The resampling parameter and the spatial scalability parameter are configured to be used for scaling the video data such that the left and right offset values ​​of the scaling window of the extracted subimage are updated based on the left boundary position of the extracted subimage, the top and bottom offset values ​​of the scaling window are updated based on the top boundary position of the extracted subimage, and the position of the scaling window is shifted based on the updated offset values. The steps include generating a bitstream and A method comprising the step of transmitting the bitstream.

11. A method of video decoding performed by a processor, The steps include receiving a bitstream containing video data having one or more sub-images, A step of extracting sub-bitstreams associated with resampling parameters and spatial scalability parameters corresponding to one or more sub-images, wherein the sub-bitstreams are extracted from the bitstream associated with the video data based on an array of target output layer set indexes, target highest time identification values, and target sub-image index values ​​associated with the video data. The steps include decoding the video data based on the resampling parameters and spatial scalability parameters of the extracted subbitstream, The steps include scaling the video data based on the resampling parameter and spatial scalability parameter of the extracted subbitstream, Includes, The left and right offset values ​​of the scaling window of the extracted subimage, which is signaled with high-level syntax, are updated based on the left boundary position of the extracted subimage. The upper and lower offset values ​​of the scaling window of the extracted subimage, which are signaled by the high-level syntax, are updated based on the upper boundary position of the extracted subimage. The position of the scaling window is shifted based on the updated offset value. method.

12. The method according to claim 11, wherein the left and right offset values ​​of the scaling window and the top and bottom offset values ​​of the scaling window are updated according to the size and position of the sub-image.

13. The left and right offset values ​​of the scaling window are updated based on the width of the sub-image and the left boundary position of the sub-image. The method according to claim 11, wherein the upper and lower offset values ​​of the scaling window are updated based on the width of the sub-image and the upper boundary position of the sub-image.

14. The method according to claim 11, which enables adaptive resolution change of the received video data based on the resampling parameters.

15. The method according to claim 11, wherein the resampling parameter corresponds to one or more flags signaled in a parameter set associated with the video data.

16. The method according to claim 11, wherein the spatial scalability parameter corresponds to one or more flags signaled in a parameter set associated with the video data.

17. The method according to claim 11, wherein the resampling of the video data during decoding is disabled based on the resampling parameters.

18. A computer system for video decoding, One or more computer-readable non-transient storage media configured to store computer program code, A computer system comprising one or more computer processors configured to access the computer program code and to operate as instructed by the computer program code, wherein the computer program code is configured to cause one or more computer processors to perform the method according to any one of claims 11 to 17.

19. A computer program for video decoding, wherein the computer program is configured to cause one or more computer processors to perform the method described in any one of claims 11 to 17.

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