Method, apparatus and computer program for video coding

Abstract

To provide a method, a system, and a computer program for video encoding.SOLUTION: A method and a system include computer codes configured to execute the following steps of: acquiring video data for one or more processors; parsing video parameter set (VPS) syntax of the video data; determining whether a syntax element value of the VPS syntax indicates a picture order count (POC) value of an access unit (AU) of the video data; setting at least one of a plurality of pictures, slices, and tiles of the video data in the AU on the basis of the syntax element value.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 62 / 904,338, filed September 23, 2019, and U.S. Patent Application No. 17 / 024,288, filed September 17, 2020, both of which are incorporated herein in their entireties.

[0002] The disclosed subject matter relates to video coding and decoding, and more particularly to signaling profile / layer / level information for supporting temporal / spatial scalability via sub-picture partitioning. [Background technology]

[0003] Coding and decoding video 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, 1920 × 1080 luminance samples and associated chrominance samples. The sequence of images can have a fixed or variable image rate (also informally called the frame rate), for example, 60 images per second or 60 Hz. Uncompressed video has significant bitrate requirements. For example, 1080p60 4:2:0 video (1920 × 1080 luminance sample resolution at a 60 Hz frame rate) with 8 bits per sample requires a bandwidth approaching 1.5 Gbit / s. One hour of such video requires more than 600 GBytes of storage space.

[0004] One goal of video coding and decoding can be to reduce redundancy in an input video signal through compression. Compression can help reduce the aforementioned bandwidth or storage requirements by two or more orders of magnitude, in some cases. Both lossless and lossy compression, as well as combinations of them, may be used. Lossless compression refers to techniques that allow an exact copy of the original signal to be reconstructed from a compressed version. With lossy compression, 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 the 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 can tolerate higher distortion than users of television contribution applications. The achievable compression ratio can reflect that the higher the acceptable / tolerable distortion, the higher the compression ratio.

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

[0006] Historically, video encoders and decoders have tended to operate mostly on a given picture size that was defined and remained constant for a coded video sequence (CVS), group of pictures (GOP), or similar multi-picture timeframe. For example, in MPEG-2, system designs have been known to vary the horizontal resolution (and thus the picture size) depending on factors such as scene activity, but only in I-pictures, and thus typically for GOPs. Resampling of reference pictures to use different resolutions within a CVS is known, for example, in ITU-T Rec. H.263 Annex P. However, here the picture size does not change; only the reference picture is resampled, and only a portion of the image canvas may be used (in the case of downsampling) or only a portion of the scene may be captured (in the case of upsampling). Furthermore, H.263 Annex Q allows for resampling of individual macroblocks upward or downward by a factor of two (in each dimension). Again, the picture size remains the same. Because the macroblock size is fixed in H.263, it does not need to be signaled.

[0007] Resizing predicted images has become more mainstream in modern video coding. For example, VP9 allows for resampling of reference images and changing the resolution of the entire image. Similarly, specific proposals made for VVC (e.g., Hendry, et. al., “On adaptive resolution change (ARC) for VVC,” Joint Video Team document JVET-M0135-v1, Jan 9-19, 2019, incorporated herein in its entirety) allow for resampling of the entire reference image to different—higher or lower—resolutions. In that document, different candidate resolutions are proposed, coded within the sequence parameter set and referenced by per-image syntax elements within the picture parameter set. Summary of the Invention [Means for solving the problem]

[0008]

[0009] Methods and apparatuses include memory configured to store computer program code and one or more processors configured to access the computer program code and operate as instructed by the computer program code, the computer program code including: acquiring code configured to cause at least one processor to acquire video data; parsing code configured to cause the at least one processor to parse a video parameter set (VPS) syntax of the video data; determining code configured to cause the at least one processor to determine whether a value of a syntax element of the VPS syntax indicates a picture order count (POC) value of an access unit (AU) of the video data; and setting code configured to cause the at least one processor to set at least one of a plurality of images, slices, and tiles of the video data to the AU based on the value of the syntax element.

[0009] According to an example embodiment, the value of the syntax element indicates a sequential number among multiple pictures, slices, and tiles of video data set in the AU.

[0010] According to an example embodiment, a VPS syntax is included in the VPS of the video data to identify the number of enhancement layers of at least one type of the video data.

[0011] According to an exemplary embodiment, the code for determining is further configured to cause the at least one processor to determine whether the VPS syntax includes a flag indicating whether the POC value increases uniformly per AU.

[0012] According to an example embodiment, there is further present calculating code configured to cause the at least one processor to calculate an access unit count (AUC) from the POC values ​​and picture level values ​​of the video data in response to determining that the VPS includes a flag, the flag indicating that the POC values ​​do not increase uniformly per AU.

[0013] According to an exemplary embodiment, there is further present calculating code configured to cause the at least one processor to calculate an access unit count (AUC) from the POC values ​​and sequence level values ​​of the video data in response to determining that the VPS includes a flag, the flag indicating that the POC values ​​increase uniformly per AU.

[0014] According to an example embodiment, the code for determining is further configured to cause the at least one processor to determine whether the VPS syntax includes a flag indicating whether at least one of the images is divided into multiple sub-regions.

[0015] According to an example embodiment, the setting code is further configured to, in response to determining that the VPS syntax includes a flag, the flag indicating that at least one of the images is not divided into multiple sub-regions, cause the at least one processor to set an input picture size of at least one of the images to a coded picture size signaled in a sequence parameter set (SPS) of the video data.

[0016] According to an example embodiment, the determining code is further configured to, in response to determining that the VPS syntax includes a flag, the flag indicating that at least one of the images is divided into a plurality of sub-regions, cause the at least one processor to determine whether the SPS includes a syntax element signaling an offset corresponding to a layer of the video data.

[0017] According to an exemplary embodiment, the offset includes a widthwise offset and a heightwise offset.

[0018] Further features, nature and various advantages of the disclosed subject matter will become more apparent from the following detailed description and accompanying drawings. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram of a simplified block diagram of a communication system according to an embodiment. [Figure 2] FIG. 1 is a schematic diagram of a simplified block diagram of a communication system according to an embodiment. [Figure 3] FIG. 2 is a schematic diagram of a simplified block diagram of a decoder according to an embodiment; [Figure 4] FIG. 2 is a schematic diagram of a simplified block diagram of an encoder according to an embodiment; [Figure 5A] 1 is a schematic diagram of options for signaling ARC parameters according to the related art; [Figure 5B] 1 is a schematic diagram of options for signaling ARC parameters according to the related art; [Figure 5C] FIG. 10 is a schematic diagram of options for signaling ARC parameters according to an embodiment. [Figure 5D] FIG. 10 is a schematic diagram of options for signaling ARC parameters according to an embodiment. [Figure 5E] FIG. 10 is a schematic diagram of options for signaling ARC parameters according to an embodiment. [Figure 6] FIG. 10 is a diagram illustrating an example of a syntax table according to an embodiment. [Figure 7] FIG. 1 is a schematic diagram of a computer system according to an embodiment. [Figure 8] FIG. 1 illustrates an example of a prediction structure for scalability with adaptive resolution change. [Figure 9] FIG. 10 is a diagram illustrating an example of a syntax table according to an embodiment. [Figure 10] FIG. 10 is a schematic diagram of a simplified block diagram for parsing and decoding poc cycles per access unit and access unit count values ​​according to an embodiment. [Figure 11] 1 is a schematic diagram of a video bitstream structure including multi-layer sub-images according to an embodiment; [Figure 12] 10 is a schematic diagram of a display of a selected sub-image with enhanced resolution according to an embodiment; [Figure 13] FIG. 1 is a block diagram of a process for decoding and displaying a video bitstream containing multi-layer sub-images, according to an embodiment. [Figure 14] FIG. 1 is a schematic diagram of a 360 video display with a sub-image enhancement layer, according to an embodiment. [Figure 15] FIG. 1 illustrates an example of layout information for a sub-image and its corresponding layer and image prediction structure, according to an embodiment. [Figure 16] FIG. 10 illustrates an example of layout information for a sub-image and its corresponding layer and image prediction structure with local region spatial scalability aspects, according to an embodiment. [Figure 17] FIG. 10 illustrates an example of a syntax table for sub-image layout information, according to an embodiment. [Figure 18] FIG. 10 illustrates an example syntax table of an SEI message for sub-image layout information, according to an embodiment. [Figure 19] FIG. 1 illustrates an example syntax table showing profile / tier / level information for output layers and each output layer set, according to an embodiment. [Figure 20] FIG. 10 illustrates an example syntax table showing the output layer mode for each output layer set according to an embodiment. [Figure 21] FIG. 10 illustrates an example syntax table showing the current sub-image for each layer of each output layer set, according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] The proposed features described below may be used separately or combined in any order. Furthermore, the embodiments may be implemented by processing circuitry (e.g., one or more processors or one or more integrated circuits). In one example, the one or more processors execute a program stored on a non-transitory computer-readable medium.

[0021] Recently, the compression-domain aggregation or extraction of multiple semantically independent image portions into a single video image has attracted some attention. In particular, for example, in the context of 360 coding or certain surveillance applications, multiple semantically independent source images (e.g., six cubic surfaces of a cubically projected 360 scene, or individual camera inputs in a multi-camera surveillance setup) may require separate adaptive resolution settings to address different scene-specific activity at a given time. In other words, an encoder can choose to use different resampling factors for the different semantically independent images that make up the entire 360 ​​or surveillance scene at a given time. When combined into a single image, it requires that reference image resampling be performed and adaptive resolution coding signaling be available for portions of the coded image.

[0022] 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 the case of one-way data transmission, a first terminal (110) may code video data at a local location for transmission to another terminal (120) via the network (150). A second terminal (120) may receive the coded video data of the other terminal from the network (150), decode the coded data, and display the recovered video data. One-way data transmission may be common in media serving applications, for example.

[0023] 1 illustrates a second pair of terminals (130, 140) provided to support bidirectional transmission of coded video, such as may occur during a video conference. For bidirectional transmission of data, each terminal (130, 140) can code video data captured at a local location for transmission to the other terminal over a network (150). Each terminal (130, 140) can also receive coded video data transmitted by the other terminal, decode the coded data, and display the recovered video data on a local display device.

[0024] In FIG. 1 , the terminals (110, 120, 130, 140) may be illustrated as servers, personal computers, and smartphones, although the principles of the present disclosure are not so limited. Embodiments of the present disclosure find application in 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, 120, 130, 140), including, for example, wired and / or wireless communication networks. The communication network (150) may exchange data over circuit-switched and / or packet-switched channels. Exemplary networks include telecommunications networks, local area networks, wide area networks, and / or the Internet. For purposes of this discussion, the architecture and topology of the network (150) may not be important to the operation of the present disclosure, unless otherwise described herein below.

[0025] 2 shows the arrangement of a video encoder and decoder in a streaming environment as an example of an application for the disclosed subject matter. The disclosed subject matter may be equally applicable to other video-enabled applications including, for example, video conferencing, digital TV, storage of compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0026] The streaming system may include a capture subsystem (213), which may include a video source (201), such as a digital camera, that creates an uncompressed video sample stream (202). The sample stream (202), shown with a bold line to emphasize its high data volume compared to an encoded video bitstream, may be processed by an encoder (203) connected 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), shown with a thin line to emphasize its low data volume compared to the sample stream, may be stored on a streaming server (205) for future use. One or more streaming clients (206, 208) may access the streaming server (205) to obtain copies (207, 209) of the encoded video bitstream (204). The client (206) may include a video decoder (210) that decodes an incoming copy of the encoded video bitstream (207) and creates an outgoing video sample stream (211) that can be rendered to 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 coding / compression standard. Examples of these standards include ITU-T Recommendation H.265. The developing video coding standard is informally known as Versatile Video Coding, or VVC. The disclosed subject matter may be used in the context of VVC.

[0027] FIG. 3 may be a functional block diagram of a video decoder (210) according to one embodiment of the disclosure.

[0028] The receiver (310) can receive one or more codec video sequences to be decoded by the decoder (210), in the same or another embodiment, 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 / software link to a storage device that stores the encoded video data. The receiver (310) can receive the encoded video data along with other data, such as coded audio data and / or auxiliary data streams, that can be forwarded to respective using entities (not shown). The receiver (310) can separate the coded video sequences from other data. To combat 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 control, or from an isochronous network, the buffer (315) may not be needed or may be small. For use with best-effort packet networks such as the Internet, the buffer (315) may be needed and may be relatively large and advantageously adaptively sized.

[0029] The video decoder (210) may include a parser (320) for reconstructing symbols (321) from the entropy-coded video sequence. These symbol categories include information used to manage the operation of the decoder (210) and, in some cases, information for controlling a rendering device, such as a display (212), which 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 supplemental enhancement information (SEI) message or a video usability information (VUI) parameter set fragment (not shown). The parser (320) may parse / entropy decode the received coded video sequence. The coding of the coded video sequence may conform to a video coding technique or standard and may follow principles well known to those skilled in the art, including variable length coding, Huffman coding, arithmetic coding with or without context-dependent coding, etc. The parser (320) may extract a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder from the coded video sequence based on at least one parameter corresponding to the group. The subgroups 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 may also extract from coded video sequence information such as transform coefficients, quantizer parameter values, motion vectors, etc.

[0030] The parser (320) can perform entropy decoding / parsing operations on the video sequence received from the buffer (315) to create symbols (321).

[0031] The reconstruction of the symbols (321) can include many different units, depending on the type of coded video picture or portion thereof (e.g., inter- and intra-pictures, inter- and intra-blocks, etc.), and other factors. Which units are included and how they are included 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 many units is not shown for clarity.

[0032] 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, the following conceptual subdivision into functional units is appropriate.

[0033] 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 the transform used, block size, quantization coefficients, quantization scaling matrix, etc. It can output blocks containing sample values ​​that can be input to the aggregator (355).

[0034] 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).

[0035] In other cases, the output samples of the scalar / inverse transform unit (351) may relate to an inter-coded, possibly motion-compensated, block. In such cases, the motion-compensated prediction unit (353) may access a reference picture memory (357) to fetch samples used for prediction. After motion-compensating the fetched samples according to the symbols (321) related to 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 a motion vector and made available to the motion compensation unit in the form of a symbol (321) that may have, for example, X, Y, and reference picture components. Motion compensation may also include interpolation of sample values ​​fetched from the reference picture memory when sub-sample accurate motion vectors are used, motion vector prediction mechanisms, and the like.

[0036] The output samples of the aggregator (355) may be subjected to various loop filtering techniques in a loop filter unit (356). Video compression techniques may include in-loop filter techniques controlled by parameters included in the coded video bitstream and provided to the loop filter unit (356) as symbols (321) from the parser (320), but may also be responsive to meta-information obtained during decoding of previous (in decode order) portions of the coded image or coded video sequence, and to previously reconstructed loop-filtered sample values.

[0037] The output of the loop filter unit (356) may be a sample stream that can be output to the rendering device (212) and stored in the reference image memory (356) for use in future inter-image prediction.

[0038] Once a particular coded picture is fully reconstructed, it can be used as a reference picture for future predictions. Once a coded picture is fully reconstructed and the coded picture is identified as a reference picture (e.g., by the parser (320)), the current reference picture (356) can become part of the reference picture buffer (357), and a new current picture memory can be reallocated before starting reconstruction of the next coded picture.

[0039] The video decoder 320 can perform decoding operations according to a predetermined video compression technology, which may be documented in a standard, such as ITU-T Rec. H.265. A coded video sequence can comply with the syntax specified by the video compression technology or standard used in the sense that it adheres to the syntax of the video compression technology or standard specified in the video compression technology document or standard, particularly the 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 set 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.

[0040] In one embodiment, the receiver (310) can receive additional (redundant) data along with the encoded video. The additional data may be included as part of the coded video sequence. The additional data can be used by the video decoder (320) to properly decode the data and / or more accurately reconstruct the original video data. The additional data can be in the form of, for example, temporal, spatial, or SNR (signal-to-noise / quality scalability) enhancement layers, redundant slices, redundant images, forward error correction codes, etc.

[0041] FIG. 4 may be a functional block diagram of a video encoder (203) according to one embodiment of the present disclosure.

[0042] The encoder (203) can receive video samples from a video source (201) (not part of the encoder) that can capture video images to be coded by the encoder (203).

[0043] The video source (201) can provide a source video sequence to be coded by the encoder (203) in the form of a digital video sample stream, which can be of any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, ...), any color space (e.g., BT.601 Y CrCB, RGB, ...), and any suitable sampling structure (e.g., Y CrCb 4:2:0, Y CrCb 4:4:4). In a media serving system, the video source (201) can be a storage device that stores previously prepared 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, impart 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 readily understand the relationship between pixels and samples. The following discussion focuses on samples.

[0044] According to one embodiment, the encoder (203) can code and compress images of a source video sequence into a coded video sequence (443) in real time or under any other time constraint, as required by the application. Enforcing an appropriate coding rate is one of the functions of the controller (450). The controller controls and is operatively coupled to other functional units, as described below. For clarity, coupling is not depicted. Parameters set by the controller can include parameters related to rate control (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 optimizing the video encoder (203) for a particular system design.

[0045] Some video encoders operate in what those skilled in the art will readily recognize as a "coding loop." As an overly simplified explanation, the coding loop may consist of an encoding portion, an encoder (430) (hereafter "source coder") (responsible for creating symbols based on the input image being coded and a reference image), and a (local) decoder (433) embedded in the encoder (203) that reconstructs the symbols to create sample data that a (remote) decoder will also create (since any compression between the symbols and the coded video bitstream is lossless in the video compression techniques contemplated by the disclosed subject matter). That reconstructed sample stream is input into a reference image memory (434). Because decoding the symbol stream produces 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 would "see" if it used prediction during decoding. This basic principle of reference image synchrony (and the drift that occurs when synchrony cannot be maintained, for example due to channel errors) is well known to those skilled in the art.

[0046] The operation of the "local" decoder (433) can be the same as the operation of the "remote" decoder (210), which has already been described in detail above in connection with Figure 3. However, with brief reference also to Figure 3, the entropy decoding portion of the decoder (210), including the channel (312), receiver (310), buffer (315), and parser (320), need not be entirely implemented in the local decoder (433), because symbols are available and the encoding / decoding of the symbols into a coded video sequence by the entropy coder (445) and parser (320) can be lossless.

[0047] An observation that can be made at this point is that any decoder technology other than parsing / entropy decoding that is present in a decoder must necessarily be present 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 technology can be omitted, as it is the reverse of the decoder technology that has been comprehensively described. Only in certain areas is more detailed description necessary, and is provided below.

[0048] As part of its operation, the source coder (430) can 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 can be selected as predictive references for the input frame.

[0049] The local video decoder (433) can decode the coded video data of frames that may be designated as reference frames based on symbols created by the source coder (430). The operation of the coding engine (432) can 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 will typically be a replica of the source video sequence with some errors. The local video decoder (433) can replicate the decoding process that may be performed by the video decoder 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 common content as reconstructed reference frames (without transmission errors) obtained by the far-end video decoder.

[0050] The predictor (435) can perform the prediction search for the coding engine (432). That is, for a new frame to be coded, the predictor (435) can search the reference picture memory (434) for sample data (as candidate reference pixel blocks) or specific metadata, such as motion vectors and block shapes, of reference pictures, which can serve as appropriate prediction references for the new picture. The predictor (435) can operate on a sample block-by-pixel block basis to find appropriate prediction references. In some cases, as determined by the search results obtained by the predictor (435), the input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory (434).

[0051] The controller (450) can manage the coding operations of the video coder (430), including, for example, setting parameters and subgroup parameters used to code the video data.

[0052] The outputs of all the aforementioned functional units may undergo entropy coding in an entropy coder (445), which converts the symbols produced by the various functional units into a coded video sequence by losslessly compressing the symbols according to techniques known to those skilled in the art, such as Huffman coding, variable length coding, arithmetic coding, etc.

[0053] 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 will store the encoded 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).

[0054] The controller (450) can manage the operation of the encoder (203). During coding, the controller (450) can assign a particular coded picture type to each coded picture, which can affect the coding technique that can be applied to the respective picture. For example, in many cases, pictures can be assigned as one of the following frame types:

[0055] An intra-picture (I-picture) may be one that can be coded and decoded without using any other frame in a sequence as a source of prediction. Some video codecs can use various types of intra-pictures, such as independent decoder refresh pictures. Those skilled in the art are aware of these variations of I-pictures and their respective uses and characteristics.

[0056] 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.

[0057] Bidirectionally predicted images (B-pictures) may be those that can be coded and decoded using intra- or inter-prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multiple predicted images may use more than two reference images and associated metadata to reconstruct a single block.

[0058] A source image is typically spatially divided into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples each) and coded block by block. Blocks may be predictively coded with reference to other (already coded) blocks, as determined by the coding assignment applied to the respective image of the block. For example, blocks of an I-image may be nonpredictively coded, or they may be predictively coded with reference to previously coded blocks of the same image (spatial prediction or intra-prediction). Pixel blocks of a P-image may be nonpredictively coded via spatial prediction or via temporal prediction with reference to one previously coded reference image. Blocks of a B-image may be nonpredictively coded via spatial prediction or via temporal prediction with reference to one or two previously coded reference images.

[0059] The video coder (203) may perform coding operations in accordance with 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 redundancy in the input video sequence. Thus, the coded video data may conform to a syntax specified in the video coding technique or standard being used.

[0060] In one embodiment, the transmitter (440) can transmit additional data along with the encoded video. The video coder (430) can include such data as part of the coded video sequence. The additional data can include temporal / spatial / SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, Supplemental Enhancement Information (SEI) messages, Visual Usability Information (VUI) parameter set fragments, etc.

[0061] 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 this description.

[0062] Hereinafter, a sub-image refers to a possibly rectangular arrangement of samples, blocks, macroblocks, coding units, or similar entities that can be semantically grouped and coded independently at varying resolutions. There can be one or more sub-images per 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 in the compressed domain without transcoding the coded image 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.

[0063] Hereinafter, adaptive resolution change (ARC) refers to a mechanism that enables changing the resolution of an image or sub-image in a coded video sequence, for example, by reference image resampling. Hereinafter, ARC parameters refer to the control information needed to perform adaptive resolution change, which may include, for example, filter parameters, scaling factors, output image and / or reference image resolutions, various control flags, etc.

[0064] The above description focuses on the coding and decoding of a single semantically independent coded video picture. Before describing the implications of coding / decoding multiple sub-pictures with independent ARC parameters and the additional complexity that it implies, options for signaling the ARC parameters shall be described.

[0065] 5A-5E, several novel options for signaling ARC parameters are shown. As noted for each option, they have certain advantages and disadvantages in terms of coding efficiency, complexity, and architecture. A video coding standard or technology may select one or more of these options, or options known from the prior art, for signaling ARC parameters. It is contemplated that the options may not be mutually exclusive and may be interchanged based on application needs, related standard technologies, or encoder preferences.

[0066] The classes of ARC parameters can include: - Separate or combined up / downsample coefficients in the X and Y dimensions, - up / down sample coefficients with an additional time dimension, which indicate a constant speed of zooming in / out for a given number of images;

[0067] Any of the above two may include the coding of one or more putatively short syntax elements that can point to a table containing coefficients, -Resolution of the X or Y dimension of the input image, output image, reference image, coded image, combined or individual, in units of sample, block, macroblock, CU, 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 ​​can be inferred from another set of values; this can be gated, for example, by using flags; see below for more detailed examples). - "warping" coordinates are of appropriate granularity, as described above, similar to those used in H.263 Annex P (H.263 Annex P defines one efficient way of coding such warping coordinates, but it is contemplated that other, potentially more efficient ways may be devised. For example, according to an embodiment, the variable-length reversible "Huffman" style coding of Annex P warping coordinates is replaced by appropriate-length binary coding, where the length of the binary codewords may, for example, be derived from the maximum image size, possibly multiplied by a specific factor and offset by a specific value, thereby allowing "warping" outside the bounds of the maximum image size); and / or - Up- or downsample filter parameters. In the simplest case, there may be only a single filter for upsampling and / or downsampling. However, in certain cases, it may be advantageous to allow more flexibility in filter design, which may require signaling of filter parameters. Such parameters may be selected via an index in a list of possible filter designs, the filter may be fully specified (e.g., via a list of filter coefficients using an appropriate entropy coding technique), the filter may be selected implicitly via the up / downsample ratio, which is signaled according to any of the mechanisms described above, and so on.

[0068] In the following, the description assumes coding of a finite set of up / downsample coefficients (the same coefficients used in both the X and Y dimensions) indicated by a codeword. The codeword can advantageously be variable-length coded, for example, using Ext-Golomb codes common to certain syntax elements in 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:

[0069] [Table 1]

[0070] 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. The table can be expanded to include more values. The values ​​may also be represented by entropy coding mechanisms other than Ext-Golomb codes, for example, using binary coding. This can have particular advantages when the resampling factor is external to the video processing engine itself (the encoder and decoder are the most important), for example, by MANE. Note that in the (probably) most common case where no resolution change is required, a short Ext-Golomb code can be chosen. In the table above, there is only a single bit. This can have coding efficiency advantages over using binary codes in the most common case.

[0071] The number of entries in the table, as well as their semantics, may be fully or partially configurable. For example, a basic overview of the table may be conveyed in a "high" parameter set, such as a sequence or decoder parameter set. Alternatively or additionally, one or more such tables may be defined in a video coding technology or standard and may be selected, for example, via a decoder or sequence parameter set.

[0072] The following describes how the upsample / downsample coefficients (ARC information) coded as described above can be included in a video coding technique or standard syntax. Similar considerations can also apply to one or several codewords that control an up / downsample filter. See below for a description of when a filter or other data structure requires a relatively large amount of data.

[0073] As shown in the example of Figure 5A, diagram (500A) shows that 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 may 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 very high, and because picture headers may be transient in nature, scaling factors may not be relevant across picture boundaries. Furthermore, as shown in the example of Figure 5B, diagram (500B) shows that JVET-M 0135 includes PPS information (504), ARC reference information (505), SPS information (507), and target Res table information (506).

[0074] According to an exemplary embodiment, FIG. 5C shows an example (500C) in which tile group header information (508) and ARC information (509) are shown, FIG. 5D shows an example (500D) in which tile group header information (514), ARC reference information (513), SPS information (516) and ARC information (515) are shown, and FIG. 5E shows an example (500E) in which adaptation parameter set (APS) information (511) and ARC information (512) are shown.

[0075] JVCET-M 135-v1 includes ARC reference information (505) (index) located within an image parameter set (504), which indexes a table (506) containing target resolutions located within a sequence parameter set (507). The placement of possible solutions in table (506) within sequence parameter set (507) can be justified by using SPS as an interoperability negotiation point during capability exchange, according to oral statements made by the authors. Resolution can vary within the limits set by the values ​​in table (506) for each image by referencing the appropriate image parameter set (504).

[0076] 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 certain advantages over existing techniques, as discussed above. Options may coexist in the same video coding technique or standard.

[0077] In one embodiment, ARC information (509), such as a resampling (zoom) factor, 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 may be appropriate when the ARC information is small, e.g., a single variable-length ue(v) or a fixed-length codeword of a few bits, as shown above. Having the ARC information directly in the tile group header has the added advantage that the ARC information may be applicable to, for example, 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 assumes whole-image adaptive resolution changes (e.g., as opposed to tile-group-based adaptive resolution changes), placing the ARC information in a tile group header has certain advantages in terms of error resilience.

[0078] In the same or another embodiment, the ARC information (512) itself may reside in an appropriate parameter set (511), such as a picture parameter set, a header parameter set, a tile parameter set, an adaptive parameter set, etc. (the adaptive parameter set shown). The scope of that parameter set may advantageously be no larger than a picture, e.g., a tile group. Use of the ARC information is implicit by activation of the associated parameter set. For example, if a video coding technology or standard only contemplates picture-based ARC, a picture parameter set or equivalent may be appropriate.

[0079] In the same or another embodiment, the ARC reference information (513) may be present in a tile group header (514) or similar data structure, and may point to a subset of the ARC information (515) available in a parameter set (516) with a scope greater than a single image, such as a sequence parameter set or a decoder parameter set.

[0080] The implicit activation of the additional level of indirection of PPS from the tile group header PPS / SPS used in JVET-M 0135-v1 appears unnecessary, according to an exemplary embodiment, because picture parameter sets, like sequence parameter sets, can be used for capability negotiation or announcement (and are included in certain standards, such as RFC 3984). However, if the ARC information should be applicable to, for example, sub-images also represented by tile groups, a parameter set with activation scope limited to the tile group, such as an adaptive parameter set or a header parameter set, may be a better choice. Also, if the ARC information is of non-negligible size, for example, if it contains filter control information such as a large number of filter coefficients, parameters may be a better choice than using the header (508) directly from the perspective of coding efficiency, because these settings may be reusable by future images or sub-images by referencing the same parameter set according to an exemplary embodiment.

[0081] When using a sequence parameter set or another higher parameter set with a range spanning multiple images, certain considerations may apply. 1. The parameter set for storing the ARC information table (516) may be a sequence parameter set in some cases, but a decoder parameter set is advantageous in other cases. A decoder parameter set can have multiple CVSs, i.e., activation ranges of all coded video bits in the coded video stream, i.e., from the start of a session to the end of a session. Such ranges may be more appropriate because possible ARC factors may be decoder functions implemented in hardware, and hardware functions tend not to change with CVS (at least in some entertainment systems, groups of pictures of half length or less). However, placing the table in a sequence parameter set is clearly included in the deployment options described herein, especially in connection with point 2 below. 2. The ARC reference information (513) can advantageously be placed directly in the image / slice / GOB / tile group header (hereafter referred to as the tile group header) (514) rather than in the picture parameter set as in JVCET-M 0135-v1. The reason is that if an 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. Assume that only the ARC reference information is changed, but other information, such as quantization matrix information in the PPS, remains. Such information can be substantial in size and needs to be retransmitted to complete the new PPS. The ARC reference information can be a single codeword, such as an index into the table (513), and since it is the only value that changes, retransmitting all of the quantization matrix information, for example, would be cumbersome and wasteful. To that extent, it can be significantly better in terms of coding efficiency to avoid the indirection through the PPS, as proposed in JVET-M 0135-v1. Similarly, putting the ARC reference information in the PPS has the further disadvantage that, since the scope of the image parameter set activation is the image, the ARC information referenced by the ARC reference information (513) must apply to the entire image, not necessarily a sub-image.

[0082] In the same and other embodiments, signaling of ARC parameters can follow a detailed example as outlined in Figure 6. Figure 6 shows a syntax diagram of an expression (600) used in a video coding standard. The notation in such a syntax diagram loosely follows C-style programming. Bolded lines indicate syntax elements present in the bitstream, while non-bolded lines often indicate control flow or variable settings.

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

[0084] 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, the 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] When adaptive resolution is used, according to an exemplary embodiment, it is the output resolution in samples that is coded (613). Reference numeral 613 refers to both output_pic_width_in_luma_samples and output_pic_height_in_luma_samples, which together can define the resolution of the output image. Elsewhere in a video coding technology or standard, specific restrictions on either value can be defined. For example, a level definition can limit the number of total output samples that can be the product of the values ​​of those two syntax elements. Also, a particular video coding technology or standard, or an external technology or standard, such as a system standard, can limit the numbering range (e.g., one or both dimensions must be divisible by a power of two) or the aspect ratio (e.g., width and height must have a relationship such as 4:3 or 16:9). Such restrictions may be introduced to facilitate hardware implementation or for other reasons.

[0086] In certain applications, it may be desirable for an encoder to instruct a decoder to use a particular reference picture size rather than implicitly assuming that size is the output picture size. In this example, the syntax element reference_pic_size_present_flag (614) gates the conditional presence of the reference picture dimension (615) (again, the code refers to 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 coded value is zero, there is one table entry. If the value is 5, there are six table entries. For each "line" 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, allowing for different decoded sizes, in effect zoom factors, per tile group.

[0089] Certain video coding techniques or standards, such as VP9, ​​support spatial scalability by implementing a particular form of reference picture resampling (signaled quite differently than the disclosed subject matter) in conjunction with temporal scalability to enable spatial scalability. In particular, certain reference pictures 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 and other embodiments, values ​​in the NAL unit header, e.g., a Time ID field, can be used to indicate not only temporal layers but also spatial layers. Doing so has certain advantages in certain system designs. For example, existing selective forwarding units (SFUs) created and optimized for temporal layer selective forwarding based on NAL unit header Time ID values ​​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, which is indicated by the Time ID field in the NAL unit header.

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

[0092] In HEVC and certain other video coding technologies, a picture order count (POC) value can be used to indicate a reference picture selected from multiple reference pictures stored in a decoded picture buffer (DPB). When an access unit (AU) includes one or more pictures, slices, or tiles, each picture, slice, or tile belonging to the same AU can have the same POC value, from which it can be derived that they were created from content with the same composition time. In other words, in a scenario where two pictures / slices / tiles carry the same given POC value, it can indicate two pictures / slices / tiles that belong to the same AU and have the same composition time. Conversely, two pictures / tiles / slices with different POC values ​​can indicate those pictures / slices / tiles that belong to different AUs and have different composition times.

[0093] According to example 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 AU, it becomes possible to use the POC values ​​to identify potentially independently decodable pictures / slices / tiles that have 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 and other embodiments, the access unit count (AUC) may be signaled in a high-level syntax structure, such as a NAL unit header, a slice header, a tile group header, an SEI message, a parameter set, or an AU delimiter. The AUC value may be used to identify NAL units, pictures, slices, or tiles that belong to a given AU. The AUC value may correspond to distinct composition time instances. 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 due to the small constraints on 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 and other embodiments, the value of the Picture Order Count (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 the number of different consecutive POC values ​​that may be associated with the same AU. For example, if the value of poc_cycle_au is equal to 4, then pictures, slices, or tiles with POC values ​​equal to 0 to 3 are associated with AUs with AUC values ​​equal to 0, and pictures, slices, or tiles with POC values ​​equal to 4 to 7 are associated with AUs with AUC values ​​equal to 1. Thus, the value of AUC can be inferred by dividing the POC value by the value of poc_cycle_au.

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

[0098] In the same or another embodiment, FIG. 9 shows an example syntax table (900) for signaling the vps_poc_cycle_au syntax element in the VPS (or SPS) indicating the poc_cycle_au used for all pictures / slices in the coded video sequence, and the slice_poc_cycle_au syntax element indicating the poc_cycle_au of the current slice in the slice header. If the POC value increases uniformly per AU, vps_contant_poc_cycle_per_au in the VPS is set to 1, and vps_poc_cycle_au is signaled in the VPS. In this case, slice_poc_cycle_au is not explicitly signaled, and the AUC value 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 equal to 0. In this case, vps_access_unit_cnt is not signaled, and slice_access_unit_cnt is signaled in the slice header for each slice or picture. Each slice or picture may have a different 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 a related workflow (1000), where in S100, the VPS / SPS is parsed to identify whether the POC cycle per AU is constant, and in S101, the POC cycle per AU constant in the coded video sequence is determined. If not, in S103, the value of the access unit count is calculated from the picture-level poc_cycle_au value and the POC value; if yes, in S102, the value of the access unit count is calculated from the sequence-level poc_cycle_au_value and the POC value.In S104, consideration is again given to parsing the VPS / SPS and identifying whether the POC cycle per AU is constant, which continues periodically or may otherwise be one or more parts of the workflow (1000).

[0099] In the same and 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 if the POC values ​​of the images, slices, or tiles are different. Thus, all or a subset of images, slices, or tiles associated with the same AU may be decoded in parallel and output simultaneously, without dependency between parsing / decoding across images, slices, or tiles within the same AU.

[0100] In the same and 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 the composition time is included in the container format, images can be displayed at the same time instance if they have the same composition time, even if they correspond to different AUs.

[0101] In the same and 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 and 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] FIG. 8 shows an example (800) of a video sequence structure having combinations of temporal_id, layer_id, POC, and AUC values ​​with adaptive resolution change. In this example, an image, slice, or tile in the first AU with AUC=0 may have temporal_id=0 and layer_id=0 or 1, while an image, slice, or tile in the second AU with AUC=1 may have temporal_id=1 and layer_id=0 or 1, respectively. Regardless of the values ​​of temporal_id and layer_id, the value of POC increases by 1 for each image. In this example, the value of poc_cycle_au may be equal to 2. Preferably, the value of poc_cycle_au may be set equal to the number of (spatial scalability) layers. Thus, in this example, the value of POC increases by 2 and the value of AUC increases by 1.

[0103] In an example embodiment, 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 may be used to indicate the inter-picture or inter-layer prediction structure without changing the signaling, but with the following restrictions: 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.

[0104] In the same and other embodiments, the scaling of motion vectors based on POC differences for temporal motion vector prediction can be disabled across multiple images within an access unit. Thus, although each image can 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 be reference images with the same time instance. Thus, in an exemplary embodiment, if the reference image belongs to the AU associated with the current image, the motion vector scaling function can return 1.

[0105] In the same and other embodiments, if the spatial resolution of the reference image is different from that of the current image, scaling of motion vectors based on POC difference for temporal motion vector prediction can be optionally disabled across multiple images. If 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.

[0106] In the same or another embodiment, motion vectors may be scaled based on the AUC difference instead of the POC difference for temporal motion vector prediction, especially when poc_cycle_au has non-uniform values ​​(when vps_contant_poc_cycle_per_au==0). Otherwise (when vps_contant_poc_cycle_per_au==1), the scaling of motion vectors based on the AUC difference may be identical to the scaling of motion vectors based on the POC difference.

[0107] In the same or another embodiment, when a motion vector is scaled based on the AUC difference, a reference motion vector within the same AU (having the same AUC value) as the current image is not scaled based on the AUC difference and is used for motion vector prediction without scaling or with scaling based on the spatial resolution ratio between the current image and the reference image.

[0108] In the same and other embodiments, the AUC value is used to identify AU boundaries and is used for hypothetical reference decoder (HRD) operations that require input and output timing with AU granularity. In most cases, the decoded image with the top layer within the AU can be output for display. The AUC value and layer_id value can be used to identify the output image.

[0109] In an exemplary embodiment, an image may be composed of one or more sub-images. Each sub-image may cover a local region or the entire region of the image. The region supported by a sub-image may or may not overlap the region supported by another sub-image. The region 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 region supported by a sub-image is the same as the region supported by the image.

[0110] In the same and other embodiments, 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 depend on another sub-image or coded image. A sub-image may or may not have a parsing dependency from another sub-image or coded image.

[0111] In the same and other embodiments, 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.

[0112] In the same and other embodiments, a sub-picture having (W,H) may be coded and included in the coded bitstream corresponding to layer 0, where W denotes the width of the sub-picture and H denotes the height of the sub-picture, respectively, while (W*S w,k ,H* S h,k ) may be coded and included in the coded bitstream corresponding to layer k, where S w,k ,S h,k denotes 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. On the other hand, if S w,k , S h,k If the value of is less than 1, resampling is equivalent to downsampling.

[0113] In the same and other embodiments, coded subimages within a layer may have different visual qualities than coded subimages within another layer, either within the same subimage or within a different subimage. For example, subimage i within layer n may have a quantization parameter Q i,n and subimage j in layer m is coded with quantization parameter Q j,m It is coded as:

[0114] In the same and other embodiments, coded sub-images within a layer may be independently decodable without parsing or decoding dependency from coded sub-images in another layer of the same local region. A sub-image layer that may be independently decodable without reference to another sub-image layer of the same local region is an independent sub-image layer. Coded sub-images within an independent sub-image layer may or may not have decoding or parsing dependency from previous coded sub-images in the same sub-image layer, but coded sub-images may not have any dependency from coded sub-images in another sub-image layer.

[0115] In the same and other embodiments, coded subimages within a layer may be dependently decodable, with any parsing or decoding dependency from coded subimages in another layer of the same local region. A subimage layer that may be dependently decodable with reference to another subimage layer of the same local region is a dependent subimage layer. Coded subimages within a dependent subimage may reference coded subimages belonging to the same subimage, previous coded subimages in the same subimage layer, or both reference subimages.

[0116] In the same and other embodiments, a coded sub-picture is composed of one or more independent sub-picture layers and one or more dependent sub-picture layers. However, there may be at least one independent sub-picture layer for a coded sub-picture. An independent sub-picture layer may have a value of a layer identifier (layer_id), which may be present in the NAL unit header or another high-level syntax structure, equal to 0. A sub-picture layer with layer_id equal to 0 is a base sub-picture layer.

[0117] In the same and other embodiments, 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, and 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.

[0118] In the same or another embodiment, an image may be composed of one or more foreground sub-images, with or without background sub-images. Each sub-image may have its own base sub-image layer and one or more non-base (enhancement) layers. Each base sub-image layer may be referenced by one or more non-base sub-image layers. Each non-base sub-image layer with layer_id equal to a can reference a non-base sub-image layer with layer_id equal to b, where a is greater than b.

[0119] In the same and other embodiments, an image may be composed of one or more foreground sub-images, with or without background sub-images. Each coded sub-image in a (base or non-base) sub-image layer may be referenced by one or more non-base layer sub-images that belong to the same sub-image and one or more non-base layer sub-images that do not belong to the same sub-image.

[0120] In the same and other embodiments, 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.

[0121] In the same and other embodiments, a coded video sequence (CVS) may be a group of coded images. A CVS may be composed of one or more coded sub-image sequences (CSPS), which may be groups of coded sub-images 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.

[0122] In the same and other embodiments, 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.

[0123] In the same and other embodiments, the number of CSPS layers corresponding to a CSPS may be the same as or different from the number of CSPS layers corresponding to another CSPS.

[0124] In the same or another embodiment, a CSPS layer may have a different temporal resolution (e.g., frame rate) than another CSPS layer, and the original (uncompressed) sub-image sequence may be temporally resampled (upsampled or downsampled), coded with different temporal resolution parameters, and included in the bitstream corresponding to the layer.

[0125] 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, where F*S t,k A sub-image sequence that is 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 denotes the temporal sampling ratio of layer k. S t,k If the value of is greater than 1, the temporal resampling process is equivalent to frame rate up-conversion. t,k If the value of is less than 1, the temporal resampling process is equivalent to a frame rate down conversion.

[0126] In the same and other embodiments, when a sub-picture with CSPS layer a is referenced by a sub-picture with CSPS layer b for motion compensation or any inter-layer prediction, if the spatial resolution of CSPS layer a is different from the spatial resolution of CSPS layer b, the decoded pixels in CSPS layer a are resampled and used for reference. The resampling process may require upsampling or downsampling filtering.

[0127] FIG. 11 shows an example video stream (1100) including a background video CSPS with layer_id equal to 0 and multiple foreground CSPS layers. A coded sub-picture may be composed of one or more CSPS layers, but background regions that do not belong to any foreground CSPS layer may be composed 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 in the same region. The enhancement CSPS layer may reference reconstructed pixels and motion vectors of the base layer corresponding to the same region.

[0128] In the same and other embodiments, the video bitstream corresponding to the base layer is contained in a track, and the CSPS layers corresponding to each sub-image are contained in separate tracks within the video file.

[0129] In the same and other embodiments, the video bitstream corresponding to the base layer is included in a track, and 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.

[0130] In the same and other embodiments, each CSPS layer of each sub-image is stored in a separate track. Each track may or may not have parsing or decoding dependencies from one or more other tracks.

[0131] In the same and other embodiments, each track can include a bitstream corresponding to layer i to layer 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.

[0132] In the same and other embodiments, an 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.

[0133] In the same or other embodiments, FIG. 12 shows an example of a video conference (1200) based on a multi-layer sub-image method. The video stream includes one base layer video bitstream corresponding to a background image and one or more enhancement layer video bitstreams corresponding to 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, which includes one or more user-in-image (PIP) images. When a specific user is selected through client control, the enhancement CSPS layer corresponding to the selected user is decoded and displayed with enhanced quality or spatial resolution. FIG. 13 shows a diagram (1300) for operations including decoding a video bitstream with multiple layers in S130 and identifying a background region and one or more foreground sub-images in S131. It is determined in S132 whether a specific sub-image region has been selected. If not, the background region is decoded and displayed in S134, and if so, the enhanced sub-image is decoded and displayed in S133, and diagram (1300) may continue cyclically from there, or may proceed sequentially or in parallel with other operations.

[0134] In the same and other embodiments, a network intermediate box (such as a router) can select a subset of layers to send to a user depending on its bandwidth. The image / sub-image organization can be used for bandwidth adaptation. For example, if a user does not have the bandwidth, the router can select a strip of layers or some sub-images due to their importance or based on the settings used, which can be done dynamically to adopt the bandwidth.

[0135] FIG. 14 illustrates a 360 video use case (1400). When a spherical 360 image is projected onto a planar image, the projected 360 image may be divided into multiple sub-images as a base layer. Enhancement layers for specific sub-images may be coded and transmitted to the client. The decoder can 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 have higher quality for the decoded sub-image with the enhancement layer. Otherwise, the decoded image with the base layer may be displayed at a lower quality.

[0136] In the same and other embodiments, any layout information for display may be present in the file as supplemental information (such as an SEI message or metadata). One or more decoded sub-images may be rearranged and displayed according to the signaled layout information. The layout information may be signaled by a streaming server or broadcaster, regenerated by a network entity or cloud server, or determined by a user's customized settings.

[0137] In an exemplary 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. For example, image size (width, height), offset information of the upper left corner (x offset, y offset). Figure 15 shows an example (1500) of the layout of divided sub-images, their sub-image size and position information, and their corresponding image prediction structure. 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.

[0138] In the same or other embodiments, each sub-image corresponding to an independent layer may have a unique POC value within the AU. If 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 may be used.

[0139] In the same and other embodiments, the layer_id may not be used and the POC (delta) value may be used to indicate the (inter-layer) prediction structure.

[0140] In the same and other embodiments, a sub-image having a POC value equal to N corresponding to a layer (or local region) may or may not be used as a reference image for a sub-image having a POC value equal to N+K corresponding to the same layer (or the same local region) for motion compensation prediction. In most cases, the value of the number K may be equal to the maximum number of (independent) layers, which may be the same as the number of sub-regions.

[0141] In the same or another embodiment, Figure 16 shows an extended case (1600) of Figure 15. When the input image is divided into multiple (e.g., four) subregions, each local region can be coded with one or more layers. In this case, the number of independent layers may be equal to the number of subregions, and one or more layers may correspond to a subregion. Thus, each subregion can be coded using one or more independent layers and zero or more dependent layers.

[0142] In the same and other embodiments, in Figure 16, the input image may be divided into four sub-regions. The upper right sub-region may be coded as two layers, Layer 1 and Layer 4, and the lower right sub-region may be coded as two layers, Layer 3 and Layer 5. In this case, Layer 4 may refer to Layer 1 for motion compensation prediction, and Layer 5 may refer to Layer 3 for motion compensation.

[0143] In the same and other embodiments, in-loop filtering (such as a deblocking filter, adaptive in-loop filter, reshaper, bilateral filter, or any deep learning-based filtering) across layer boundaries can be (optionally) disabled.

[0144] In the same and other embodiments, motion compensated prediction or intrablock copying across layer boundaries can (optionally) be disabled.

[0145] In the same and other embodiments, border padding for motion compensated prediction or in-loop filtering at sub-image boundaries may be processed as an option. A flag indicating whether border padding is processed or not can be signaled in a high-level syntax structure such as a parameter set (VPS, SPS, PPS, or APS), a slice or tile group header, or an SEI message.

[0146] In the same and other embodiments, layout information of sub-regions (or sub-pictures) may be signaled in the VPS or SPS. Figure 17 shows an example (1700) of syntax elements in the VPS and SPS. In this example, vps_sub_picture_dividing_flag is signaled in the VPS. This flag may indicate whether the input picture is divided into multiple sub-regions. If the value of vps_sub_picture_dividing_flag is equal to 0, the input picture in the coded video sequence corresponding to the current VPS may not be divided into multiple sub-regions. In this case, the 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.

[0147] In the same and other embodiments, the values ​​of vps_full_pic_width_in_luma_samples and vps_full_pic_height_in_luma_samples may not be used for decoding, but may be used for synthesis and display.

[0148] In the same and other embodiments, 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 particular layer. In this case, the coded picture size (pic_width_in_luma_samples, pic_height_in_luma_samples) signaled in the SPS may be equal to the width and height of the sub-region corresponding to a particular 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.

[0149] In the same and other embodiments, the position information (pic_offset_x, pic_offset_y) of the top left corner of the sub-region may not be used for decoding, but may be used for synthesis and display.

[0150] In the same or another embodiment, layout information (size and position) of all or a subset of subregions of an input image, as well as inter-layer dependency information, may be signaled in a parameter set or SEI message. FIG. 18 shows an example (1800) of syntax elements indicating information about the layout of subregions, inter-layer dependencies, and relationships between subregions and one or more layers. In this example (1800), the syntax element num_sub_region indicates the number of (rectangular) subregions in the current coded video sequence. The syntax element num_layers indicates the number of layers in the current coded video sequence. The value of num_layers may be greater than or equal to the value of num_sub_region. If any subregion is coded as a single layer, the value of num_layers 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 of the top-left corner of the i-th subregion, respectively. sub_region_width[i] and sub_region_height[i] indicate the width and height of the i-th subregion, respectively.

[0151] In one embodiment, one or more syntax elements specifying an output layer set to indicate one of multiple layers to be output with or without profile 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 the example (1900) of 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.

[0152] In the same or other embodiments, output_layer_flag[i] equal to 1 specifies that the i-th layer is to be output. vps_output_layer_flag[i] equal to 0 specifies that the i-th layer is not to be output.

[0153] In the same and other embodiments, one or more syntax elements specifying profile hierarchical level information for each output layer set may be signaled in a high-level syntax structure, such as a VPS, DPS, SPS, PPS, APS, or SEI message. Further referring to Figure 19, a syntax element num_profile_tile_level indicating the number of profile hierarchical level information per OLS in a coded video sequence that references a VPS may be signaled in the VPS. For each output layer set, a set of profile hierarchical level information syntax elements, or an index indicating a particular profile hierarchical level information among entries in the profile hierarchical level information, may be signaled in the same number as the number of output layers.

[0154] In the same and other embodiments, profile_tier_level_idx[i][j] specifies the index of the profile_tier_level() syntax structure that applies to the jth layer of the ith OLS within the list of profile_tier_level() syntax structures in the VPS.

[0155] In the same and other embodiments, referring to the example (2000) of Figure 20, the syntax elements num_profile_tile_level and / or num_output_layer_sets may be signaled if the maximum number of layers is greater than 1 (vps_max_layers_minus1>0).

[0156] In the same and other embodiments, referring to FIG. 20, there may be a syntax element vps_output_layers_mode[i] in the VPS that indicates the mode of output layer signaling for the i-th output layer set.

[0157] In the same or other embodiments, vps_output_layers_mode[i] equal to 0 specifies that only the top layer is output in the i-th output layer set. vps_output_layer_mode[i] equal to 1 specifies that all layers are output in the i-th output layer set. vps_output_layer_mode[i] equal to 2 specifies that the layer to be output is the layer with vps_output_layer_flag[i][j] equal to 1 set for the i-th output layer. More values ​​may be reserved according to the embodiment.

[0158] In the same or other embodiments, 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.

[0159] In the same and other embodiments, referring to Figure 20, there may be a flag vps_ptl_signal_flag[i] for the i-th output layer set. If the value of vps_ptl_signal_flag[i] is omitted, the profile stratum level information for the i-th output layer set may or may not be signaled.

[0160] In the same and other embodiments, referring to FIG. 21, the number of sub-pictures in the current CVS, max_subpics_minus1, may be signaled in a high-level syntax structure, such as a VPS, DPS, SPS, PPS, APS or SEI message.

[0161] In the same and other embodiments, 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.

[0162] In the same and other embodiments, one or more syntax elements indicating the sub-picture identifiers belonging to each layer of each output layer set may be signaled in the VPS. Referring to Figure 21, sub_pic_id_layer[i][j][k] indicates the kth sub-picture present in the jth layer of the ith output layer set. With this information, the decoder can know which sub-pictures may be decoded and output for each layer of a particular output layer set.

[0163] In the same and other embodiments, the following syntax elements can be used to define the layout of sub-images between layers or within a single layer: The output layer set with sub-image division may be signaled in the profile / layer / layer information of VPS or SPS. In PPS, updated layout information of sub-images may be present if the image size is updated by reference image resampling. For VPS, Table 2 can be considered.

[0164] [Table 2A] [Table 2B]

[0165] According to an exemplary embodiment, Table 2 vps_sub_picture_info_present_flag equal to 1 specifies that syntax elements indicating sub-picture layout and identifiers are present in the VPS. vps_sub_picture_info_present_flag equal to 0 specifies that syntax elements indicating sub-picture layout and identifiers are not present in the VPS.

[0166] According to an exemplary embodiment, vps_sub_pic_id_present_flag in Table 2 equal to 1 specifies that vps_sub_pic_id[i][j] is present in the VPS. vps_sub_pic_id_present_flag equal to 0 specifies that vps_sub_pic_id[i][j] is not present in the VPS.

[0167] According to an exemplary embodiment, Table 2 vps_sub_pic_id_length_minus1 plus 1 specifies the number of bits used to represent the syntax element vps_sub_pic_id[i][j]. The value of vps_sub_pic_id_length_minus1 shall be in the range of 0 to 15. If not present, the value of vps_sub_pic_id_length_minus1 is inferred to be equal to Ceil(Log2(Max(2,vps_num_sub_pic_in_pic_minus1[i]+1)))-1 for the i-th layer.

[0168] According to an example embodiment, Table 2 vps_sub_pic_id[i][j] specifies the sub-picture ID of the jth sub-picture of the ith layer. The length of the vps_sub_pic_id[i][j] syntax element is vps_sub_pic_id_length_minus1+1 bits. If not present, for each j in the range 0 to vps_num_sub_pic_in_pic_minus1[i], vps_sub_pic_id[i][j] is inferred to be equal to j.

[0169] According to an exemplary embodiment, Table 2 vps_pic_width_max_in_luma_samples[i] specifies the maximum width in luma sample units of each decoded image of the i-th layer. pic_width_max_in_luma_samples shall not be equal to 0 and shall be an integer multiple of MinCbSizeY.

[0170] According to an exemplary embodiment, Table 2 pic_height_max_in_luma_samples specifies the maximum height in luma sample units of each decoded image that references an SPS. pic_height_max_in_luma_samples shall not be equal to 0 and shall be an integer multiple of MinCbSizeY.

[0171] According to an exemplary embodiment, Table 2 vps_sub_pic_offset_x_in_luma_samples[i][j] specifies the horizontal offset in luma samples of the top-left corner luma sample of the jth sub-image of the ith layer relative to the top-left corner luma sample of the composite image. If not present, the value of vps_sub_pic_offset_x_in_luma_samples[i][j] is inferred to be equal to 0. vps_sub_pic_offset_x_in_luma_samples[i][j] shall be an integer multiple of the CTB size.

[0172] According to an exemplary embodiment, Table 2 vps_sub_pic_offset_y_in_luma_samples[i][j] specifies the vertical offset in luma samples of the top-left corner luma sample of the jth sub-image of the ith layer relative to the top-left corner luma sample of the composite image. If not present, the value of vps_sub_pic_offset_y_in_luma_samples[i][j] is inferred to be equal to 0. vps_sub_pic_offset_y_in_luma_samples[i][j] shall be an integer multiple of the CTB size.

[0173] According to an exemplary embodiment, Table 2 vps_sub_pic_width_in_luma_samples[i][j] specifies the width of the jth sub-image of the ith layer in luma samples. vps_sub_pic_width_in_luma_samples[i][j] shall be an integer multiple of the CTB size.

[0174] According to an exemplary embodiment, Table 2 vps_sub_pic_height_in_luma_samples[i][j] specifies the height of the jth sub-image of the ith layer in units of luma samples. vps_sub_pic_height_in_luma_samples[i][j] shall be an integer multiple of the CTB size.

[0175] According to an exemplary embodiment, Table 2 vps_num_output_layer_sets_minus1 plus 1 specifies the number of output layers set in a coded video sequence that references a VPS. If not present, the value of vps_num_output_layer_sets_minus1 is inferred to be equal to 0.

[0176] According to an example embodiment, Table 2 vps_num_profile_tile_levels_minus1 plus 1 specifies the number of profile / tier / level information in a coded video sequence that references a VPS. If not present, the value of vps_num_profile_tile_levels_minus1 is inferred to be equal to 0.

[0177] According to an exemplary embodiment, Table 2 vps_output_layers_mode[i] equal to 0 specifies that only the top layer is output in the i-th output layer set. vps_output_layer_mode[i] equal to 1 specifies that all layers are output in the i-th output layer set. vps_output_layer_mode[i] equal to 2 specifies that the layers to be output are those in the i-th output layer set for which vps_output_layer_flag[i][j] is equal to 1. The value of vps_output_layers_mode[i] shall range from 0 to 2. The value 3 for vps_output_layer_mode[i] is reserved for future use by ITU-T|ISO / IEC.

[0178] According to an exemplary embodiment, Table 2 vps_num_output_subpic_layer_minus1[i][j] specifies the number of sub-images in the jth layer of the ith output layer set.

[0179] According to an example embodiment, Table 2 vps_sub_pic_id_layer[i][j][k] specifies the subimage ID of the kth output subimage of the jth subimage of the ith layer. The length of the vps_sub_pic_id_layer[i][j][k] syntax element is vps_sub_pic_id_length_minus1+1 bits. If not present, for each j in the range 0 to num_output_subpic_layer_minus1[i][j], vps_sub_pic_id_layer[i][j][k] is inferred to be equal to k.

[0180] According to an example embodiment, Table 2 vps_output_layer_flag[i][j] equal to 1 specifies that the jth layer of the ith output layer set is output. vps_output_layer_flag[i][j] equal to 0 specifies that the jth layer of the ith output layer set is not output.

[0181] According to an exemplary embodiment, Table 2 vps_profile_tier_level_idx[i][j] specifies an index into the list of profile_tier_level() syntax structures in the VPS for the profile_tier_level() syntax structure that applies to the jth layer of the ith output layer set.

[0182] For SPS, Table 3 can be considered.

[0183] [Table 3A] [Table 3B]

[0184] According to an exemplary embodiment, Table 3 pic_width_max_in_luma_samples specifies the maximum width in luma sample units of each decoded image that references an SPS. pic_width_max_in_luma_samples shall not be equal to 0 and shall be an integer multiple of MinCbSizeY.

[0185] According to an exemplary embodiment, Table 3 pic_height_max_in_luma_samples specifies the maximum height in luma samples of each decoded image that references an SPS. pic_height_max_in_luma_samples shall not be equal to 0 and shall be an integer multiple of MinCbSizeY.

[0186] According to an example embodiment, subpics_present_flag in Table 3 equal to 1 indicates that the subpics parameter is present in the SPS RBSP syntax. Subpics_present_flag equal to 0 indicates that the subpics parameter is not present in the SPS RBSP syntax.

[0187] According to an exemplary embodiment, if the bitstream is the result of a sub-bitstream extraction process and contains only a subset of the sub-pictures of the input bitstream to the sub-bitstream extraction process, it may be necessary to set the value of subpics_present_flag equal to 1 in the RBSP of the SPS.

[0188] According to an exemplary embodiment, sps_sub_pic_id_present_flag in Table 3 equal to 1 specifies that sps_sub_pic_id[i] is present in the SPS, and sps_sub_pic_id_present_flag equal to 0 specifies that sps_sub_pic_id[i] is not present in the SPS.

[0189] According to an exemplary embodiment, Table 3 sps_sub_pic_id_length_minus1 plus 1 specifies the number of bits used to represent the syntax element sps_sub_pic_id[i][j]. The value of sps_sub_pic_id_length_minus1 shall be in the range of 0 to 15. If not present, the value of sps_sub_pic_id_length_minus1 is inferred to be equal to Ceil(Log2(Max(2,sps_num_sub_pic_in_pic_minus1+1)))-1.

[0190] According to an example embodiment, Table 3 sps_sub_pic_id[i] specifies the sub-picture ID of the i-th sub-picture. The length of the sps_sub_pic_id[i] syntax element is sps_sub_pic_id_length_minus1+1 bits. If not present, for each i in the range 0 to sps_num_sub_pic_in_pic_minus1, sps_sub_pic_id[i] is inferred to be equal to i.

[0191] According to an exemplary embodiment, Table 3 sps_sub_pic_offset_x_in_luma_samples[i] specifies the horizontal offset, in luma samples, of the top-left corner luma sample of the i-th sub-image relative to the top-left corner luma sample of the composite image. If not present, the value of sps_sub_pic_offset_x_in_luma_samples[i] is inferred to be equal to 0. sps_sub_pic_offset_x_in_luma_samples[i] shall be an integer multiple of the CTB size.

[0192] According to an exemplary embodiment, Table 3 sps_sub_pic_offset_y_in_luma_samples[i] specifies the vertical offset, in luma samples, of the top-left corner luma sample of the i-th sub-image relative to the top-left corner luma sample of the composite image. If not present, the value of sps_sub_pic_offset_y_in_luma_samples[i] is inferred to be equal to 0. sps_sub_pic_offset_y_in_luma_samples[i] shall be an integer multiple of the CTB size.

[0193] According to an exemplary embodiment, Table 3 sps_sub_pic_width_in_luma_samples[i] specifies the width of the ith sub-image in units of luma samples. sps_sub_pic_width_in_luma_samples[i] shall be an integer multiple of the CTB size.

[0194] According to an exemplary embodiment, Table 3 sps_sub_pic_height_in_luma_samples[i] specifies the height of the ith sub-image in units of luma samples. sps_sub_pic_height_in_luma_samples[i] shall be an integer multiple of the CTB size.

[0195] According to an example embodiment, Table 3 sps_num_output_subpic_sets_minus1 plus 1 specifies the number of output subpicture sets in a coded video sequence that references an SPS. If not present, the value of sps_num_output_layer_sets_minus1 is inferred to be equal to 0.

[0196] According to an exemplary embodiment, Table 3 sps_num_output_subpic_minus1[i] specifies the number of sub-images in the ith output sub-image set.

[0197] According to an exemplary embodiment, Table 3 sps_sub_pic_id_oss[i][j] specifies the subimage ID of the jth output subimage of the ith subimage. The length of the sps_sub_pic_id_oss[i][j] syntax element is sps_sub_pic_id_length_minus1+1 bits. If not present, for each i in the range 0 to sps_num_output_subpic_minus1[i], sps_sub_pic_id_oss[i][j] is inferred to be equal to j.

[0198] For PPS, Table 4 can be considered.

[0199] [Table 4]

[0200] According to an exemplary embodiment, subpics_updated_flag in Table 4 equal to 1 specifies that the subpics layout information is updated by the syntax element indicating updated subpics layout information in the PPS, and subpics_updated_flag equal to 0 specifies that the subpics layout information is not updated.

[0201] According to an exemplary embodiment, Table 4 pps_sub_pic_id_present_flag equal to 1 specifies that pps_sub_pic_id[i] is present in the PPS, and pps_sub_pic_id_present_flag equal to 0 specifies that pps_sub_pic_id[i] is not present in the PPS.

[0202] According to an exemplary embodiment, Table 4 pps_sub_pic_id_length_minus1 plus 1 specifies the number of bits used to represent the syntax element pps_sub_pic_id[i][j]. The value of pps_sub_pic_id_length_minus1 shall be in the range of 0 to 15. If not present, the value of pps_sub_pic_id_length_minus1 is inferred to be equal to Ceil(Log2(Max(2,pps_num_sub_pic_in_pic_minus1+1)))-1.

[0203] According to an example embodiment, Table 4 pps_sub_pic_id[i] specifies the sub-picture ID of the i-th sub-picture. The length of the pps_sub_pic_id[i] syntax element is sps_sub_pic_id_length_minus1+1 bits. If not present, for each i in the range 0 to pps_num_sub_pic_in_pic_minus1, pps_sub_pic_id[i] is inferred to be equal to i.

[0204] According to an exemplary embodiment, Table 4 pps_sub_pic_offset_x_in_luma_samples[i] specifies the horizontal offset, in luma samples, of the top-left corner luma sample of the i-th sub-image relative to the top-left corner luma sample of the composite image. If not present, the value of pps_sub_pic_offset_x_in_luma_samples[i] is inferred to be equal to 0. pps_sub_pic_offset_x_in_luma_samples[i] shall be an integer multiple of the CTB size.

[0205] According to an exemplary embodiment, Table 4 pps_sub_pic_offset_y_in_luma_samples[i] specifies the vertical offset, in luma samples, of the top-left corner luma sample of the i-th sub-image relative to the top-left corner luma sample of the composite image. If not present, the value of sps_sub_pic_offset_y_in_luma_samples[i] is inferred to be equal to 0. sps_sub_pic_offset_y_in_luma_samples[i] shall be an integer multiple of the CTB size.

[0206] According to an exemplary embodiment, Table 4 pps_sub_pic_width_in_luma_samples[i] specifies the width of the ith sub-image in units of luma samples. pps_sub_pic_width_in_luma_samples[i] shall be an integer multiple of the CTB size.

[0207] According to an exemplary embodiment, Table 4 pps_sub_pic_height_in_luma_samples[i] specifies the height of the ith sub-image in units of luma samples. pps_sub_pic_height_in_luma_samples[i] shall be an integer multiple of the CTB size.

[0208] According to an exemplary embodiment, Table 4 pps_num_output_subpic_sets_minus1 plus 1 specifies the number of output subpicture sets in the image that references the PPS. If not present, the value of pps_num_output_layer_sets_minus1 is inferred to be equal to 0.

[0209] According to an exemplary embodiment, Table 4 pps_num_output_subpic_minus1[i] specifies the number of sub-images in the ith output sub-image set.

[0210] According to an exemplary embodiment, Table 4 pps_sub_pic_id_oss[i][j] specifies the subimage ID of the jth output subimage of the ith subimage. The length of the pps_sub_pic_id_oss[i][j] syntax element is pps_sub_pic_id_length_minus1+1 bits. If not present, for each i in the range 0 to pps_num_output_subpic_minus1[i], pps_sub_pic_id_oss[i][j] is inferred to be equal to j.

[0211] The techniques for signaling adaptive resolution parameters described above 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.

[0212] Computer software can be coded using any suitable machine code or computer language that can be subjected to assembly, compilation, linking, or similar mechanisms by a computer central processing unit (CPU), graphics processing unit (GPU), etc. to produce code containing instructions that can be executed directly or through translation, microcode execution, etc.

[0213] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smartphones, gaming devices, Internet of Things devices, and the like.

[0214] 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 a dependency or requirement related to any one or combination of components illustrated in the exemplary embodiment of computer system (700).

[0215] The computer system (700) may include certain human interface input devices. Such human interface input devices may respond to input by one or more human users, for example, through tactile input (e.g., keystrokes, swipes, data glove movements), audio input (e.g., voice, clapping), visual input (e.g., gestures), or olfactory input (not shown). The human interface devices may also be used to capture certain media that do not necessarily involve direct conscious human input, such as sound (e.g., speech, music, environmental 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).

[0216] The input human interface devices may include one or more (only one of each is shown) of a keyboard (701), a mouse (702), a trackpad (703), a touchscreen (710), a joystick (705), a microphone (706), a scanner (707), and a camera (708).

[0217] The computer system (700) may also include certain human interface output devices. Such human interface output devices may stimulate one or more of a 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 via a touchscreen (710) or joystick (705), although some haptic feedback devices may not function as input devices), audio output devices (such as speakers (709), headphones (not shown)), visual output devices (such as screens (710), including CRT screens, LCD screens, plasma screens, and OLED screens, each with or without touchscreen input capabilities and with or without haptic feedback capabilities—some of which may output two-dimensional visual output or output in more than three dimensions via means such as stereographic output, virtual reality glasses (not shown), holographic displays, and smoke tanks (not shown)), and printers (not shown).

[0218] The computer system (700) may also include human-accessible storage and related media, such as optical media, including CD / DVD ROM / RW (720) with CD / DVD or similar media (721), thumb drives (722), removable hard drives or solid state drives (723), conventional magnetic media, such as tape and floppy disks (not shown), and dedicated ROM / ASIC / PLD-based devices, such as security dongles (not shown).

[0219] Those skilled in the art should also understand that the term "computer-readable medium" as used in connection with the subject matter disclosed herein does not encompass transmission media, carrier waves, or other transitory signals.

[0220] The computer system (700) may also include interfaces to one or more communication networks. Networks may be, for example, wireless, wired, or optical. Furthermore, networks may 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 and wireless LAN; cellular networks including GSM, 3G, 4G, 5G, LTE, and the like; television wired or wireless wide-area digital networks including cable TV, satellite TV, and terrestrial broadcast TV; and vehicular and industrial networks including CAN Bus. Certain networks generally 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)). Other networks are generally integrated into the core of the computer system (700) by attachment to a system bus, as described below (e.g., an Ethernet interface to a PC computer system or a cellular network interface to a smartphone computer system). Using any of these networks, the computer system (700) can communicate with other entities. Such communication may be unidirectional, receive only (e.g., broadcast TV), unidirectional transmit only (e.g., from a CANbus to a particular CANbus device), or bidirectional, e.g., communication to other computer systems using local-area or wide-area digital networks. As noted above, specific protocols and protocol stacks may be used with each of these networks and network interfaces.

[0221] The aforementioned human interface devices, human-accessible storage devices, and network interfaces may be attached to the core (740) of the computer system (700).

[0222] A 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 arrays (FPGAs) (743), task-specific hardware accelerators (744), etc. These devices, along with internal mass storage devices such as read-only memory (ROM) (745), random access memory (746), and non-user-accessible internal hard drives, SSDs (747), etc., 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.

[0223] The CPU (741), GPU (742), FPGA (743), and accelerator (744) can execute specific instructions that, in combination, can constitute the aforementioned computer code. That computer code can be stored in ROM (745) or RAM (746). Transient data can also be stored in RAM (746), while persistent data can be stored, for example, in internal mass storage (747). Rapid storage and retrieval from any of the memory devices can be enabled through the use of cache memory, which can be closely associated with one or more of the CPU (741), GPU (742), mass storage (747), ROM (745), RAM (746), etc.

[0224] The computer-readable medium may have computer code thereon for performing various computer-implemented operations. The media 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.

[0225] By way of example and not limitation, the architecture, and in particular the computer system (700) having the core (740), can provide functionality as a result of a processor (including a CPU, GPU, FPGA, accelerator, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media can be user-accessible mass storage devices, as introduced above, as well as media associated with the core's (740) specific storage device of a non-transitory nature, such as the core's internal mass storage device (747) or ROM (745). Software implementing various embodiments of the present disclosure can be stored in such devices and executed by the core (740). The computer-readable media can include one or more memory devices or chips according to particular needs. The software can cause the core (740) and in particular the processor therein (including a CPU, GPU, FPGA, etc.) to perform particular processes or particular portions of particular processes described herein, such as defining data structures stored in RAM (746) and modifying such data structures according to the software-defined processes. Additionally or alternatively, a computer system may provide functionality as a result of logic embedded in hardware or embedded in circuitry (e.g., accelerator (744)), which can operate in place of or in conjunction with software to perform particular processes or portions of particular processes described herein. References to software can include logic, and vice versa, where applicable. References to computer-readable media can encompass software for execution, circuitry embodying logic for execution, or circuitry (such as an integrated circuit (IC)) storing both, where applicable. The present disclosure encompasses any suitable combination of hardware and software.

[0226] While this disclosure has described several exemplary embodiments, there are alterations, permutations, and various substitute equivalents that fall within the scope of this disclosure. It will thus be appreciated that those skilled in the art will be able to devise numerous systems and methods that, although not explicitly shown or described herein, embody the principles of the present disclosure and are therefore within its spirit and scope. [Explanation of symbols]

[0227] 100 Communication Systems 110 First Terminal 120 Second Terminal 130 terminals 140 terminals 150 Communication Network 201 Camera / Video Source 202 uncompressed video sample streams 203 Video Encoder / Video Source 204 encoded video bitstream 205 Streaming Server 206 Streaming Client 207 Copy / Video Bitstream 208 Streaming Client 209 Copy / Video Bitstream 210 Video Decoder 211 Outgoing Video Sample Stream 212 Display / Rendering Devices 213 Capture Subsystem 310 Receiver 312 channels 315 Buffer Memory 320 Entropy Decoder / Parser 321 Symbol 351 Scaler / Descaler Unit 352 Intra-Image Prediction Unit 353 Motion Compensation Prediction Unit 355 Aggregator 356 Loop filter unit / reference image memory 357 Reference Image Memory 430 Source Coder / Video Coder 432 Coding Engine 433 Local Video Decoder 434 Reference Image Memory 435 Predictor 440 Transmitter 443 coded video sequence 445 Entropy Coder 450 Controller 460 Communication Channels 500A Diagram 500B Figure 500C example 500D Example 501 Image Header 502 ARC information 504 Image Parameter Set 505 ARC Reference Information 506 Target Res Table Information 507 Sequence Parameter Set 508 Tile Group Header Information 509 ARC information 511 Adaptive Parameter Set (APS) Information 512 ARC information 513 ARC Reference Information 514 Tile Group Header Information 515 ARC information 516 SPS Information 600 expressions 601 Tile Group Header 602 Syntax Elements 603 Adaptive Resolution 610 Sequence Parameter Set 611 Syntax Elements 612 parameter sets 613 samples 614 Syntax Elements 615 Reference Image Dimension 616 Table Display 617 table entries 700 Computer Systems 701 Keyboard 702 Mouse 703 Trackpad 705 Joystick 706 Mike 707 Scanner 708 Camera 709 Speaker 710 Touchscreen 721 Medium 722 thumb drive 723 Solid State Drive 740 cores 743 Field Programmable Gate Area (FPGA) 744 Hardware Accelerator 745 Read-Only Memory (ROM) 746 Random Access Memory 747 Internal Mass Storage 748 System Bus 749 Peripheral Bus 1000 Workflows 1100 video streams 1200 Video Conferencing 1300 Figures 1400 Use Cases 1600 Expansion Case 1700 Syntax Element Examples 1800 Syntax Element Examples 1900 Example of Figure 19 2000 Example of Figure 20

Claims

1. 1. A method for video encoding executed by at least one processor, comprising: generating encoded video data by the at least one processor, the encoded video data including a video parameter set (VPS) syntax and one or more images, the one or more images including one or more sub-regions; signaling the VPS syntax of the video data; If it is determined that each of one or more sub-regions included in one or more images of the video data is not to be coded as an independent layer, A method for video encoding, wherein at least one of a plurality of pictures, slices, and tiles belonging to the same access unit (AU) of the video data have the same picture order count value (POC value).

2. A value of a POC cycle for an AU of the video data is obtained based on the VPS syntax; An access unit count (AUC) value of any of the image, slice, and tile is obtained based on the value of the POC cycle and the POC value, and images, slices, and tiles having the same AUC value are associated with the same AU; The method for video encoding of claim 1 , wherein the value of the POC cycle indicates the number of different POC values ​​that can be associated with the same AU.

3. 3. A method for video coding according to claim 1 or 2, wherein a sub-region included in an image of said video data comprises an enhancement layer.

4. A value of a flag in the VPS syntax indicating whether the POC value increases uniformly for each AU is obtained; 3. A method for video encoding according to claim 2.

5. When the value of the flag indicates that the POC value increases uniformly per AU, the value of the POC cycle is vps_poc_cycle_au, which indicates the value used for all pictures / slices in the coded video sequence. A method for video encoding according to claim 4.

6. When the value of the flag indicates that the POC value does not increase uniformly per AU, the value of the POC cycle is slice_poc_cycle_au, which indicates the value used for the current slice. A method for video encoding according to claim 4.

7. It is determined whether the VPS syntax includes a flag indicating whether at least one of the images is divided into multiple sub-regions. A method for video coding according to any one of claims 1 to 3.

8. If the VPS syntax includes the flag, and the flag indicates that the at least one of the images is not divided into the plurality of sub-regions, then an input picture size of the at least one of the images is set to a coded picture size signaled in a sequence parameter set (SPS) of the video data. A method for video encoding according to claim 7.

9. If the VPS syntax includes the flag, and the flag indicates that the at least one of the images is divided into the plurality of sub-regions, it is determined whether a sequence parameter set (SPS) includes a syntax element that signals an offset of the video data. A method for video encoding according to claim 7.

10. 10. The method for video encoding of claim 9, wherein the offsets include a width offset and a height offset.

11. The method for video encoding of claim 1 , wherein a flag is obtained indicating whether boundary padding for motion compensated prediction or in-loop filtering at the boundaries of the sub-region is processed or not.

12. 10. The method for video encoding of claim 1, further comprising transmitting a video bitstream of the encoded video data.

13. Apparatus configured to perform the method of any one of claims 1 to 12.

14. A computer program for causing a computer to carry out the method according to any one of claims 1 to 12.

15. 1. A method for video decoding executed by at least one processor, the method comprising: acquiring video data; parsing a video parameter set (VPS) syntax of the video data; determining that each of one or more sub-regions included in an image of the video data is not coded as an independent layer; Including, A method for video decoding, wherein, if it is determined that each of one or more sub-regions included in an image of the video data is not coded as an independent layer, at least one of multiple images, slices, and tiles belonging to the same access unit (AU) of the video data have the same picture order count value (POC value).

16. 16. An apparatus configured to perform the method of claim 15.

17. A computer program product for causing a computer to carry out the method according to claim 15.

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