Warping-based decoded picture resampling supplementary enhancement information message

Abstract

To provide a method, an apparatus, and a non-transitory computer-readable storage medium for video decoding.SOLUTION: The apparatus includes a processing circuit configured to decode a current picture based on a bitstream. The processing circuit may determine, from a supplemental enhancement information (SEI) message, a first flag that indicates whether a warping process is applied to a current decoded picture. Based on the first flag indicating that the warping process is applied to the current decoded picture, the processing circuit may determine warping information of the warping process based on the SEI message. The processing circuit may determine a warped picture from the current decoded picture based on the warping information.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 63 / 215,906, entitled "Techniques for Warping-Based Decoded Picture Resamples with SEI Messages for Coding Video Streams," filed on June 28, 2021, which claims the benefit of priority to U.S. Provisional Application No. 17 / 850,641, entitled "Warping-Based Decoded Picture Resamples with Supplemental Enhancement Information Messages," filed on June 27, 2022. The disclosures of the prior applications are incorporated herein by reference in their entireties.

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

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

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

[0005] One objective of image and / or video coding and decoding may be the reduction of redundancy in the input image and / or video signal through compression. Compression may help reduce the aforementioned bandwidth and / or storage space requirements, possibly by more than one order of magnitude. The description herein uses video encoding / decoding as an illustrative example, but the same techniques may be applied to image encoding / decoding in a similar manner without departing from the spirit of this disclosure. Both lossless and lossy compression, and combinations thereof, may be employed. Lossless compression refers to techniques where an exact copy of the original signal can be reconstructed from a compressed original signal. With lossy compression, the reconstructed signal may not be identical to the original signal, but the distortion between the original signal and the reconstructed signal is small enough to make the reconstructed signal useful for the intended application. For video, lossy compression is widely adopted. The amount of acceptable distortion depends on the application, e.g., a user of a particular consumer streaming application may tolerate higher distortion than a user of a television distribution application. The achievable compression ratio may reflect that a higher acceptable / tolerable distortion may result in a higher compression ratio.

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

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

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

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

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

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

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

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

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

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

[0016] FIG. 1B shows a schematic diagram (110) showing 65 intra prediction directions with JEM to illustrate the increasing number of prediction directions over time.

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

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

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

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

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

[0022] Aspects of the present disclosure provide a method and apparatus for video encoding and decoding. In some examples, the apparatus for video decoding includes a processing circuit. The processing circuit is configured to decode a current picture based on a bitstream. The processing circuit can determine a first flag indicating whether a warping process is applied to the current decoded picture from a supplemental enhancement information (SEI) message. Based on the first flag indicating that the warping process is applied to the current decoded picture, the processing circuit can determine warping information of the warping process based on the SEI message. The processing circuit can determine a warping picture from the current decoded picture based on the warping information.

[0023] In one embodiment, the SEI message is a display oriented SEI message in the bitstream.

[0024] In one embodiment, the SEI message is a warping-based decoded picture resampling (WDPR) SEI message in the bitstream.

[0025] In one embodiment, the warping information indicates four corner vectors between the corners of the current decoded picture and the corresponding corners of the warped picture.

[0026] In one embodiment, the processing circuit determines a vector between a sample position in the current decoded picture and a corresponding position in the warped picture based on the four corner vectors.

[0027] In one embodiment, based on a first flag indicating that the warping process indicated by the previous SEI message has been cancelled, the warping process is not applied to the current decoded picture.

[0028] In one embodiment, the warping information includes a second flag. Based on the second flag having a first value, the SEI message is applied only to the current decoded picture. Based on the second flag having a second value, the SEI message is applied to the current decoded picture and one or more subsequently decoded pictures of the current layer in output order until a condition is met.

[0029] In one example, the second flag has a second value. The processing circuit can decode subsequent pictures of the current layer that follow the current picture in output order. The processing circuit can determine a warping picture from the subsequently decoded pictures based on the warping information.

[0030] In one embodiment, the condition includes a new coding layer video sequence (CLVS) for the current layer.

[0031] In one embodiment, the warping information indicates a warping mode. The processing circuitry can determine the four corner vectors based on the warping mode.

[0032] Aspects of the present disclosure also provide a non-transitory computer-readable storage medium storing a program executable by at least one processor to perform a method for video decoding.

[0033] Further features, nature and various advantages of the disclosed subject matter will become more apparent from the following detailed description and the accompanying drawings. [Brief description of the drawings]

[0034] [Figure 1A] FIG. 2 is a schematic diagram of an example subset of intra-prediction modes. [Figure 1B] FIG. 2 is a diagram of an example intra-prediction direction. [Diagram 2] FIG. 2 illustrates a current block (201) and surrounding samples according to one embodiment. [Diagram 3] 1 is a schematic diagram of a simplified block diagram of a communication system (300), according to one embodiment. [Figure 4] FIG. 4 is a schematic diagram of a simplified block diagram of a communication system (400) according to one embodiment. [Diagram 5] FIG. 2 is a schematic diagram of a simplified block diagram of a decoder according to one embodiment. [Figure 6] FIG. 2 is a schematic diagram of a simplified block diagram of an encoder according to one embodiment. [Figure 7] FIG. 4 is a simplified block diagram of an encoder according to another embodiment. [Figure 8] FIG. 4 is a simplified block diagram of a decoder according to another embodiment. [Figure 9] FIG. 2 illustrates an example vector used for warping, according to one embodiment of the present disclosure. [Figure 10A]FIG. 2 illustrates an exemplary warping process in image stabilization, according to one embodiment of the present disclosure. [Figure 10B] FIG. 2 illustrates an exemplary warping process for compensating for global motion in multiple input pictures, according to one embodiment of this disclosure. [Figure 11] 1 is a flowchart outlining an encoding process according to one embodiment of the present disclosure. [Figure 12] 1 is a flowchart outlining a decoding process according to one embodiment of the present disclosure. [Figure 13] FIG. 1 is a schematic diagram of a computer system according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] FIG. 3 illustrates a simplified block diagram of a communication system (300) according to one embodiment of the present disclosure. The communication system (300) includes a plurality of terminal devices that can communicate with each other, for example, via a network (350). For example, the communication system (300) includes a first pair of terminal devices (310) and (320) interconnected via the network (350). In the example of FIG. 3, the first pair of terminal devices (310) and (320) perform unidirectional transmission of data. For example, the terminal device (310) can code video data (e.g., a stream of video pictures captured by the terminal device (310)) for transmission to another terminal device (320) via the network (350). The encoded video data can be transmitted in the form of one or more coded video bitstreams. The terminal device (320) can receive the coded video data from the network (350), decode the coded video data to reconstruct the video pictures, and display the video pictures according to the reconstructed video data. Unidirectional data transmission may be common, such as in media serving applications.

[0036] In another example, the communication system (300) includes a second pair of terminal devices (330) and (340) performing bidirectional transmission of coded video data, such as may occur during a video conference. In the case of bidirectional transmission of data, in one example, each of the terminal devices (330) and (340) can code video data (e.g., a stream of video pictures captured by the terminal device) for transmission to the other of the terminal devices (330) and (340) over the network (350). Each of the terminal devices (330) and (340) can also receive coded video data transmitted by the other of the terminal devices (330) and (340), can decode the coded video data to recover the video pictures, and can display the video pictures on an accessible display device according to the recovered video data.

[0037] In the example of FIG. 3, the terminal devices (310), (320), (330), and (340) may be depicted as a server, a personal computer, and a smartphone, although the principles of the present disclosure need not be so limited. Embodiments of the present disclosure find application with laptop computers, tablet computers, media players, and / or dedicated video conferencing equipment. The network (350) represents any number of networks that convey coded video data between the terminal devices (310), (320), (330), and (340), including, for example, wired (wired) and / or wireless communication networks. The communication network (350) may exchange data over circuit-switched and / or packet-switched channels. Representative networks include telecommunications networks, local area networks, wide area networks, and / or the Internet. For purposes of this description, the architecture and topology of the network (350) may not be important to the operation of the present disclosure, unless otherwise described herein below.

[0038] 4 shows an arrangement of a video encoder and a video decoder in a streaming environment as one example for application of the disclosed subject matter. The disclosed subject matter may be equally applicable to other video-enabled applications including, for example, video conferencing, digital television, storage of compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0039] The streaming system may include a capture subsystem (413) that may include a video source (401), such as a digital camera, that generates a stream of uncompressed video pictures (402). In one example, the stream of video pictures (402) includes samples taken by a digital camera. The stream of video pictures (402), depicted as thick lines to emphasize a high amount of data compared to the encoded video data (404) (or coded video bitstream), may be processed by an electronic device (420) that includes a video encoder (403) coupled to the video source (401). The video encoder (403) may include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter, as described in more detail below. The encoded video data (404) (or coded video bitstream), depicted as thin lines to emphasize a smaller amount of data compared to the stream of video pictures (402), may be stored in a streaming server (405) for future use. One or more streaming client subsystems, such as the client subsystems (406) and (408) of FIG. 4, can access the streaming server (405) to retrieve copies (407) and (409) of the encoded video data (404). The client subsystem (406) can include, for example, a video decoder (410) in an electronic device (430). The video decoder (410) decodes an input copy (407) of the encoded video data and creates an output stream (411) of video pictures that can be rendered on a display (412) (e.g., a display screen) or other rendering device (not depicted). In some streaming systems, the encoded video data (404), (407), and (409) (e.g., a video bitstream) can be encoded according to a particular video coding / compression standard. Examples of such standards include ITU-T Recommendation H.265.In one example, the developing video coding standard is informally known as Versatile Video Coding (VVC), and the disclosed subject matter may be used in the context of VVC.

[0040] It should be noted that the electronic devices (420) and (430) may include other components (not shown). For example, the electronic device (420) may include a video decoder (not shown), and the electronic device (430) may also include a video encoder (not shown).

[0041] 5 shows a block diagram of a video decoder (510) according to one embodiment of the present disclosure. The video decoder (510) may be included in an electronic device (530). The electronic device (530) may include a receiver (531) (e.g., a receiving circuit). The video decoder (510) may be used in place of the video decoder (410) of the example of FIG. 4.

[0042] The receiver (531) may receive one or more coded video sequences to be decoded by the video decoder (510), or 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 may be received from a channel (501), which may be a hardware / software link to a storage device that stores the coded video data. The receiver (531) may receive the coded video data along with other data, e.g., coded audio data and / or auxiliary data streams, that may be forwarded to their respective using entities (not depicted). The receiver (531) may separate the coded video sequences from the other data. To combat network jitter, a buffer memory (515) may be coupled between the receiver (531) and the entropy decoder / parser (520) (hereinafter "parser (520)"). In certain applications, the buffer memory (515) is part of the video decoder (510). In other applications, the buffer memory (515) may be external to the video decoder (510) (not depicted). In yet other applications, there may be a buffer memory (not depicted) external to the video decoder (510), e.g., to combat network jitter, plus another buffer memory (515) internal to the video decoder (510), e.g., to handle playout timing. When the receiver (531) is receiving data from a store / forward device of sufficient bandwidth and controllability, or from an isosynchronous network, the buffer memory (515) may not be needed or may be small. For use with best-effort packet networks such as the Internet, the buffer memory (515) may be needed and may be relatively large, advantageously adaptively sized, and may be implemented at least in part in an operating system or similar element (not depicted) external to the video decoder (510).

[0043] The video decoder (510) may include a parser (520) to reconstruct symbols (521) from the coding video sequence. These categories of symbols include information used to manage the operation of the video decoder (510) and potentially information for controlling a rendering device such as a rendering device (512) (e.g., a display screen) that is not an integral part of the electronic device (530) but may be coupled to the electronic device (530) as shown in FIG. 5. The control information for the rendering device(s) may be in the form of a Supplemental Enhancement Information (SEI) message or a Video Usability Information (VUI) parameter set fragment (not depicted). The parser (520) may parse / entropy decode the received coding video sequence. The coding of the coding video sequence may follow a video coding technique or standard and may follow various principles including variable length coding with or without context sensitivity, Huffman coding, arithmetic coding, etc. The parser (520) can extract a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder from the coded video sequence based on at least one parameter corresponding to the group. The subgroups can include groups of pictures (GOPs), pictures, tiles, slices, macroblocks, coding units (CUs), blocks, transform units (TUs), prediction units (PUs), etc. The parser (520) can also extract information from the coded video sequence, such as transform coefficients, quantization parameter values, motion vectors, etc.

[0044] The parser (520) can perform entropy decoding / parsing operations on the video sequence received from the buffer memory (515) to produce symbols (521).

[0045] The reconstruction of the symbols (521) can involve several different units, depending on the type of coded video picture or part thereof (inter-picture and intra-picture, inter-block and intra-block, etc.), as well as other factors. Which units are involved and how can be controlled by subgroup control information parsed from the coded video sequence by the parser (520). The flow of such subgroup control information between the parser (520) and the following units is not depicted for clarity.

[0046] Other than the functional blocks already mentioned, the video decoder (510) 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.

[0047] The first unit is a scalar / inverse transform unit (551), which receives quantized transform coefficients as well as control information including which transform to use, block size, quantization coefficients, quantization scaling matrices, etc. as symbol(s) (521) from the parser (520). The scalar / inverse transform unit (551) can output blocks containing sample values ​​that can be input to an aggregator (555).

[0048] In some cases, the output samples of the scaler / inverse transform (551) may relate to intra-coded blocks, i.e., blocks that do not use prediction information from a previously reconstructed picture, but can use prediction information from a previously reconstructed portion of the current picture. Such prediction information may be provided by an intra-picture prediction unit (552). In some cases, the intra-picture prediction unit (552) generates a block of the same size and shape as the block being reconstructed using surrounding already reconstructed information fetched from a current picture buffer (558). The current picture buffer (558) buffers, for example, a partially reconstructed current picture and / or a fully reconstructed current picture. The aggregator (555) may add the prediction information generated by the intra-prediction unit (552) to the output sample information from the scaler / inverse transform unit (551) on a sample-by-sample basis.

[0049] In other cases, the output samples of the scalar / inverse transform unit (551) may relate to an inter-coded, potentially motion-compensated block. In such cases, the motion compensated prediction unit (553) may access the reference picture memory (557) to fetch samples used for prediction. After motion compensating the fetched samples according to the symbols (521) associated with the block, these samples may be added to the output of the scalar / inverse transform unit (551) by the aggregator (555) to generate output sample information (in this case referred to as residual samples or residual signals). The addresses in the reference picture memory (557) from which the motion compensated prediction unit (553) fetches the prediction samples may be controlled by motion vectors available to the motion compensated prediction unit (553) in the form of symbols (521), which may have, for example, X, Y, and reference picture components. Motion compensation may also include interpolation of sample values ​​fetched from the reference picture memory (557) when sub-sample accurate motion vectors are used, motion vector prediction mechanisms, and the like.

[0050] The output samples of the aggregator (555) may be subjected to various loop filtering techniques in a loop filter unit (556). The video compression techniques may include in-loop filter techniques controlled by parameters contained in the coded video sequence (also called the coded video bitstream) and made available to the loop filter unit (556) as symbols (521) from the parser (520), but may also be responsive to meta-information obtained during decoding of previous parts (in decoding order) of the coded picture or coded video sequence, or may be responsive to previously reconstructed and loop filtered sample values.

[0051] The output of the loop filter unit (556) may be a sample stream that can be stored in a reference picture memory (557) for use in future inter-picture prediction as well as output to a rendering device (512).

[0052] Once a particular coded picture is fully reconstructed, it can be used as a reference picture for future prediction. For example, once a coded picture corresponding to a current picture is fully reconstructed and the coded picture is identified as a reference picture (e.g., by the parser (520)), the current picture buffer (558) can become part of the reference picture memory (557), and a new current picture buffer can be reallocated before beginning reconstruction of the next coded picture.

[0053] The video decoder (510) may perform decoding operations according to a given video compression technique in a standard such as ITU-T Rec. H.265. The coding video sequence may conform to a syntax specified by the video compression technique or standard being used, in the sense that the coding video sequence conforms to both the syntax of the video compression technique or standard and a profile documented in the video compression technique. Specifically, the profile may select a particular tool as the only tool available under that profile, among all tools available in the video compression technique or standard. Compliance may also require that the complexity of the coding video sequence be within a range prescribed by the level of the video compression technique or standard. In some cases, the level limits the maximum picture size, maximum frame rate, maximum reconstruction sample rate (e.g., measured in megasamples per second), maximum reference picture size, etc. The limits set by the level may in some cases be further limited by a hypothetical reference decoder (HRD) specification and metadata for HRD buffer management signaled in the coding video sequence.

[0054] In one embodiment, the receiver (531) can receive additional (redundant) data along with the coded video. The additional data may be included as part of the coded video sequence(s). The additional data may be used by the video decoder (510) to properly decode the data and / or to more accurately reconstruct the original video data. The additional data may be in the form of, for example, temporal, spatial, or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0055] 6 shows a block diagram of a video encoder (603) according to one embodiment of the present disclosure. The video encoder (603) is included in an electronic device (620). The electronic device (620) includes a transmitter (640) (e.g., a transmission circuit). The video encoder (603) can be used in place of the video encoder (403) of the example of FIG. 4.

[0056] The video encoder (603) may receive video samples from a video source (601) (which is not part of the electronic device (620) in the example of FIG. 6) that may capture a video image(s) that is coded by the video encoder (603). In another example, the video source (601) is part of the electronic device (620).

[0057] The video source (601) may provide a source video sequence to be coded by the video encoder (603) in the form of a digital video sample stream that may be of any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, ...), any color space (e.g., BT.601 Y CrCB, RGB, ...), and any suitable sampling structure (e.g., Y CrCb 4:2:0, Y CrCb 4:4:4). In a media serving system, the video source (601) may be a storage device that stores previously prepared video. In a video conferencing system, the video source (601) may be a camera that captures local image information as a video sequence. The video data may be provided as multiple individual pictures that convey motion when viewed in sequence. The pictures themselves may be organized as a spatial array of pixels, each of which may contain one or more samples, depending on the sampling structure, color space, etc., in use. Those skilled in the art can easily understand the relationship between pixels and samples. The following description focuses on samples.

[0058] According to one embodiment, the video encoder (603) can code and compress pictures of a source video sequence into a coded video sequence (643) in real-time or under any other time constraint required by the application. Enforcing an appropriate coding rate is one function of the controller (650). In some embodiments, the controller (650) controls and is operatively coupled to other functional units described below. For clarity, couplings are not depicted. Parameters set by the controller (650) can include rate control related parameters (picture skip, quantizer, lambda value for rate distortion optimization techniques, ...), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. The controller (650) can be configured to have other appropriate functions for the video encoder (603) optimized for a particular system design.

[0059] In some embodiments, the video encoder (603) is configured to operate in a coding loop. As an oversimplified explanation, in one example, the coding loop can include a source coder (630) (e.g., responsible for creating symbols, such as a symbol stream, based on an input picture to be coded and reference picture(s)) and a (local) decoder (633) embedded in the video encoder (603). The decoder (633) reconstructs the symbols to create sample data in a similar manner that a (remote) decoder would also create (since any compression between the symbols and the coding video bitstream is lossless in the video compression techniques contemplated by the disclosed subject matter). The reconstructed sample stream (sample data) is input to a reference picture memory (634). Since the decoding of the symbol stream leads to a bit-exact result regardless of the location of the decoder (local or remote), the content in the reference picture memory (634) is also bit-exact between the local and remote encoders. In other words, the prediction part of the encoder "sees" exactly the same sample values ​​as the reference picture samples that the decoder "sees" when using the prediction during decoding. This basic principle of reference picture synchrony (and the drift that occurs when synchrony cannot be maintained, e.g., due to channel errors) is also used in several related technologies.

[0060] The operation of the "local" decoder (633) may be the same as the operation of a "remote" decoder, such as the video decoder (510), already described in detail above in conjunction with Figure 5. However, with brief reference also to Figure 5, because symbols are available and the encoding / decoding of symbols into a coded video sequence by the entropy coder (645) and parser (520) may be lossless, the entropy decoding portion of the video decoder (510), including the buffer memory (515), and the parser (520), may not be fully implemented in the local decoder (633).

[0061] In one embodiment, the decoder technology, except for parsing / entropy decoding, present in the decoder, is present in the corresponding encoder in the same or substantially the same functional form. Thus, the disclosed subject matter focuses on the operation of the decoder. The description of the encoder technology can be omitted since it is the inverse of the decoder technology described generically. Only in certain areas is more detailed description required and is provided below.

[0062] In operation, in some examples, the source coder (630) may perform motion-compensated predictive coding, which predictively codes an input picture with reference to one or more previously coded pictures from a video sequence designated as “reference pictures.” In this manner, the coding engine (632) codes differences between pixel blocks of the input picture and pixel blocks of the reference picture(s) that may be selected as the predictive reference(s) to the input picture.

[0063] The local video decoder (633) may decode coded video data of pictures that may be designated as reference pictures based on symbols created by the source coder (630). The operation of the coding engine (632) may advantageously be a lossy process. When the coded video data may be decoded in a video decoder (not shown in FIG. 6), the reconstructed video sequence may be a copy of the source video sequence, usually with some errors. The local video decoder (633) may replicate the decoding process that may be performed by the video decoder on the reference pictures and store the reconstructed reference pictures in a reference picture cache (634). In this way, the video encoder (603) may locally store copies of reconstructed reference pictures that have common content as reconstructed reference pictures obtained by a far-end video decoder (without transmission errors).

[0064] The predictor (635) may perform the prediction search of the coding engine (632). That is, for a new picture to be coded, the predictor (635) may search the reference picture memory (634) for sample data (as candidate reference pixel blocks) or specific metadata, such as reference picture motion vectors, block shapes, etc., that may serve as suitable prediction references for the new picture. The predictor (635) may operate on sample blocks, pixel blocks at a time, to find suitable prediction references. In some cases, as determined by the search results obtained by the predictor (635), the input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory (634).

[0065] The controller (650) may manage the coding operations of the source coder (630), including, for example, setting the parameters and subgroup parameters used to encode the video data.

[0066] The output of all the aforementioned functional units may undergo entropy coding in an entropy coder (645), which converts the symbols produced by the various functional units into a coded video sequence by losslessly compressing the symbols according to techniques such as Huffman coding, variable length coding, arithmetic coding, etc.

[0067] The transmitter (640) may buffer the coded video sequence(s) created by the entropy coder (645) in preparation for transmission over a communications channel (660), which may be a hardware / software link to a storage device that will store the encoded video data. The transmitter (640) may merge the coded video data from the video encoder (603) with other data to be transmitted, such as coded audio data and / or auxiliary data streams (sources not shown).

[0068] The controller (650) may manage the operation of the video encoder (603). During coding, the controller (650) may assign a particular coding picture type to each coding picture, which may affect the coding technique that may be applied to the respective picture. For example, pictures are often assigned as one of the following picture types:

[0069] An intra picture (I-picture) may be one that can be coded and decoded without using any other picture in a sequence as a source of prediction. Some video codecs allow different types of intra pictures, including, for example, independent decoder refresh ("IDR") pictures. Those skilled in the art are aware of these variations of I-pictures and their respective uses and functions.

[0070] A predictive picture (P picture) may be one that can be coded and decoded using intra- or inter-prediction, which predicts the sample values ​​of each block using at most one motion vector and reference index.

[0071] A bidirectionally predicted picture (B-picture) may be one that can be coded and decoded using intra- or inter-prediction, which predicts the sample values ​​of each block using up to two motion vectors and reference indexes. Similarly, a multi-predicted picture may use more than two reference pictures and associated metadata for the reconstruction of a single block.

[0072] A source picture may generally be spatially subdivided into multiple sample blocks (e.g., 4x4, 8x8, 4x8, or 16x16 blocks each) and coded block by block. Blocks may be predictively coded with reference to other (already coded) blocks as determined by the coding assignment applied to the respective picture of the block. For example, blocks of an I picture may be non-predictively coded, or they may be predictively coded with reference to already coded blocks of the same picture (spatial or intra prediction). Pixel blocks of a P picture may be predictively coded via spatial prediction or via temporal prediction with reference to one previously coded reference picture. Blocks of a B picture may be predictively coded via spatial prediction or via temporal prediction with reference to one or two previously coded reference pictures.

[0073] The video encoder (603) may perform coding operations according to a given video coding technique or standard, such as ITU-T Rec. H.265. In its operations, the video encoder (603) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancies in the input video sequence. Thus, the coded video data may conform to a syntax specified by the video coding technique or standard being used.

[0074] In one embodiment, the transmitter (640) can transmit additional data along with the encoded video. The source coder (630) 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, SEI messages, VUI parameter set fragments, etc.

[0075] A video may be captured in time sequence as multiple source pictures (video pictures). Intra-picture prediction (often abbreviated as intra prediction) exploits spatial correlation in a given picture, while inter-picture prediction exploits correlation (temporal or other) between pictures. In one example, a particular picture being coded / decoded, called the current picture, is divided into blocks. When a block in the current picture is similar to a reference block in a reference picture that was previously coded and is still buffered in the video, the block in the current picture may be coded by a vector called a motion vector. A motion vector points to a reference block in a reference picture and may have a third dimension that identifies the reference picture when multiple reference pictures are used.

[0076] In some embodiments, bi-prediction techniques can be used in inter-picture prediction. According to bi-prediction techniques, two reference pictures, such as a first reference picture and a second reference picture, both of which precede the current picture in decoding order in a video (but may be in the past and future, respectively, in display order), are used. A block in the current picture can be coded by a first motion vector that points to a first reference block in the first reference picture and a second motion vector that points to a second reference block in the second reference picture. A block can be predicted by a combination of the first reference block and the second reference block.

[0077] Furthermore, merge mode techniques can be used in inter-picture prediction to improve coding efficiency.

[0078] According to some embodiments of the present disclosure, predictions such as inter-picture prediction and intra-picture prediction are performed on a block-by-block basis. For example, according to the HEVC standard, a picture in a sequence of video pictures is divided into coding tree units (CTUs) for compression, and the CTUs in a picture have the same size, such as 64x64 pixels, 32x32 pixels, or 16x16 pixels. In general, a CTU includes three coding tree blocks (CTBs), which are one luma CTB and two chroma CTBs. Each CTU can be recursively quadtree partitioned into one or more coding units (CUs). For example, a CTU of 64x64 pixels can be partitioned into one CU of 64x64 pixels, or four CUs of 32x32 pixels, or 16 CUs of 16x16 pixels. In one example, each CU is analyzed to determine the prediction type of the CU, such as an inter-prediction type or an intra-prediction type. The CU is partitioned into one or more prediction units (PUs) depending on the temporal and / or spatial predictability. In general, each PU includes one luma prediction block (PB) and two chroma PBs. In one embodiment, the prediction operation in coding (encoding / decoding) is performed on a prediction block basis. Using a luma prediction block as an example of a prediction block, the prediction block includes a matrix of pixel values ​​(e.g., luma values) of 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, etc.

[0079] 7 shows a diagram of a video encoder (703) according to another embodiment of the present disclosure. The video encoder (703) is configured to receive a processed block (e.g., a predictive block) of sample values ​​in a current video picture in a sequence of video pictures and to encode the processed block into a coding picture that is part of a coding video sequence. In one example, the video encoder (703) is used in place of the video encoder (403) of the example of FIG. 4.

[0080] In an HEVC example, the video encoder (703) receives a matrix of sample values ​​for a processing block, such as a predictive block of 8×8 samples. The video encoder (703) determines whether the processing block is best coded using intra mode, inter mode, or bi-predictive mode, for example using rate-distortion optimization. When the processing block is coded in intra mode, the video encoder (703) may use intra prediction techniques to code the processing block into a coding picture, and when the processing block is coded in inter mode or bi-predictive mode, the video encoder (703) may use inter prediction techniques or bi-predictive techniques, respectively, to code the processing block into a coding picture. In certain video coding techniques, the merge mode may be an inter-picture prediction sub-mode in which motion vectors are derived from one or more motion vector predictors without the benefit of coded motion vector components outside the predictors. In certain other video coding techniques, there may be motion vector components applicable to the current block. In one example, the video encoder (703) includes other components, such as a mode decision module (not shown) for determining the mode of the processing block.

[0081] In the example of FIG. 7, the video encoder (703) includes an inter-encoder (730), an intra-encoder (722), a residual calculator (723), a switch (726), a residual encoder (724), a general controller (721), and an entropy encoder (725), coupled to each other as shown in FIG. 7.

[0082] The inter-encoder (730) is configured to receive samples of a current block (e.g., a processing block), compare the block to one or more reference blocks in a reference picture (e.g., blocks in a previous picture and a subsequent picture), generate inter-prediction information (e.g., a description of redundancy information, motion vectors, merge mode information according to an inter-encoding technique), and calculate an inter-prediction result (e.g., a prediction block) based on the inter-prediction information using any suitable technique. In some examples, the reference picture is a decoded reference picture that is decoded based on the coded video information.

[0083] The intra encoder (722) is configured to receive samples of a current block (e.g., a processing block), possibly compare the block with already coded blocks in the same picture, generate quantized coefficients after transformation, and possibly also generate intra prediction information (e.g., intra prediction direction information according to one or more intra encoding techniques). In one example, the intra encoder (722) also calculates intra prediction results (e.g., a prediction block) based on the intra prediction information and reference blocks in the same picture.

[0084] The generic controller (721) is configured to determine generic control data and control other components of the video encoder (703) based on the generic control data. In one example, the generic controller (721) determines the mode of the block and provides a control signal to the switch (726) based on the mode. For example, when the mode is an intra mode, the generic controller (721) controls the switch (726) to select an intra mode result for use by the residual calculator (723) and controls the entropy encoder (725) to select intra prediction information and include the intra prediction information in the bitstream, and when the mode is an inter mode, the generic controller (721) controls the switch (726) to select an inter prediction result for use by the residual calculator (723) and controls the entropy encoder (725) to select inter prediction information and include the inter prediction information in the bitstream.

[0085] The residual calculator (723) is configured to calculate a difference (residual data) between a received block and a prediction result selected from the intra encoder (722) or the inter encoder (730). The residual encoder (724) is configured to operate based on the residual data to encode the residual data to generate transform coefficients. In one example, the residual encoder (724) is configured to transform the residual data from a spatial domain to a frequency domain to generate transform coefficients. The transform coefficients then undergo a quantization process to obtain quantized transform coefficients. In various embodiments, the video encoder (703) also includes a residual decoder (728). The residual decoder (728) is configured to perform an inverse transform and generate decoded residual data. The decoded residual data can be used by the intra encoder (722) and the inter encoder (730) as appropriate. For example, the inter encoder (730) can generate a decoded block based on the decoded residual data and the inter prediction information, and the intra encoder (722) can generate a decoded block based on the decoded residual data and the intra prediction information. The decoded blocks are suitably processed to generate a decoded picture, which may be buffered in a memory circuit (not shown) and may be used as a reference picture in some examples.

[0086] The entropy encoder (725) is configured to format the bitstream to include the encoded blocks. The entropy encoder (725) is configured to include various information in accordance with an appropriate standard, such as the HEVC standard. In one example, the entropy encoder (725) is configured to include in the bitstream general control data, selected prediction information (e.g., intra-prediction information or inter-prediction information), residual information, and other appropriate information. It should be noted that, according to the disclosed subject matter, when coding a block in a merged sub-mode of either the inter-mode or the bi-prediction mode, no residual information is present.

[0087] 8 shows a diagram of a video decoder (810) according to another embodiment of the present disclosure. The video decoder (810) is configured to receive coding pictures that are part of a coding video sequence and to decode the coding pictures to generate reconstructed pictures. In one example, the video decoder (810) is used in place of the video decoder (410) of the example of FIG. 4.

[0088] In the example of FIG. 8, the video decoder (810) includes an entropy decoder (871), an inter-decoder (880), a residual decoder (873), a reconstruction module (874), and an intra-decoder (872), coupled to each other as shown in FIG.

[0089] The entropy decoder (871) can be configured to reconstruct from the coding picture certain symbols that represent the syntax elements of which the coding picture is composed. Such symbols can include, for example, prediction information (e.g., intra prediction information or inter prediction information) that can identify the mode in which the block is coded (e.g., intra mode, inter mode, bi-predictive mode, merged sub-mode or another sub-mode, the latter two of which), certain samples or metadata used for prediction by the intra decoder (872) or the inter decoder (880), respectively, such as residual information in the form of quantized transform coefficients. In one example, when the prediction mode is an inter mode or a bi-predictive mode, the inter prediction information is provided to the inter decoder (880), and when the prediction type is an intra prediction type, the intra prediction information is provided to the intra decoder (872). The residual information can undergo inverse quantization and is provided to the residual decoder (873).

[0090] The inter decoder (880) is configured to receive the inter prediction information and to generate inter prediction results based on the inter prediction information.

[0091] The intra decoder (872) is configured to receive the intra prediction information and to generate a prediction result based on the intra prediction information.

[0092] The residual decoder (873) is configured to perform inverse quantization to extract inverse quantized transform coefficients, and to process the inverse quantized transform coefficients to transform the residual from the frequency domain to the spatial domain. The residual decoder (873) may also require certain control information (to include quantization parameters (QPs)), which may be provided by the entropy decoder (871) (a data path is not depicted since this may be only a small amount of control information).

[0093] The reconstruction module (874) is configured to combine, in the spatial domain, the residual output by the residual decoder (873) and the prediction result (possibly output by the inter-prediction module or the intra-prediction module) to form a reconstructed block that may become part of a reconstructed picture, which may become part of a reconstructed video. It should be noted that other suitable operations, such as a deblocking operation, may be performed to improve visual quality.

[0094] It should be noted that the video encoders (403), (603), and (703) and the video decoders (410), (510), and (810) may be implemented using any suitable technology. In one embodiment, the video encoders (403), (603), and (703) and the video decoders (410), (510), and (810) may be implemented using one or more integrated circuits. In another embodiment, the video encoders (403), (603), and (603) and the video decoders (410), (510), and (810) may be implemented using one or more processors executing software instructions.

[0095] According to an embodiment of the present disclosure, a bitstream may include one or more coding video sequences (CVSs). A CVS may be coded independently of other CVSs. Each CVS may include one or more layers, where each layer may be a representation of a video with a particular quality (e.g., spatial resolution) or a representation of a particular component interpretation characteristic, such as a depth map, a transparency map, or a perspective view. In the temporal dimension, each CVS may include one or more access units (AUs). Each AU may include one or more pictures of different layers corresponding to the same time instant. A coding layer video sequence (CLVS) is a per-layer CVS that may include a sequence of picture units in the same layer. If a bitstream has multiple layers, a CVS in the bitstream may have one or more CLVSs per layer.

[0096] In one embodiment, the CVS includes a sequence of AUs, where the sequence of AUs includes, in decoding order, an intra random access point (IRAP) AU, followed by zero or more AUs that are not IRAP AUs. In one example, the zero or more AUs include all subsequent AUs up to, but not including, any subsequent AU that is an IRAP AU. In one example, the CLVS includes a sequence of pictures and associated non-video coding layer (VCL) network abstraction layer (NAL) units of a base layer of the CVS.

[0097] The SEI message(s) may contain information not necessary for decoding, such as decoded samples of a coding picture from a VCL NAL unit. The SEI message(s) may be used in processes related to decoding, display, or other purposes. The SEI message(s) may be options for configuring luma or chroma samples by the decoding process. The SEI message(s) may optionally be processed by conforming decoders for output order compliance to a particular standard (e.g., HEVC 265 or VVC). In one embodiment, the SEI message(s) are present in the bitstream.

[0098] Table 1 illustrates an example display orientation SEI message syntax according to one embodiment of the disclosure.

[0099] [Table 1]

[0100] The display orientation SEI message semantics may be described as follows: When a decoded picture has a picture output flag (e.g., PicOutputFlag) equal to 1, the display orientation SEI message may inform the decoder of a transformation to be applied to the cropped decoded picture before display. The cropped decoded picture may be obtained by cropping the decoded picture based on a cropping window (e.g., an adapted cropping window). In one example, the cropping window is specified in a sequence parameter set (SPS) referenced by the corresponding coded picture.

[0101] The picture output flag (e.g., PicOutputFlag) may include whether to output the decoded picture. For example, when the picture output flag (e.g., PicOutputFlag) is 1, the decoded picture may be sent from the decoded picture buffer as output. When the picture output flag (e.g., PicOutputFlag) is 0, the decoded picture may not be sent from the decoded picture buffer as output.

[0102] display_orientation_cancel_flag equal to 1 may indicate that the display orientation SEI message cancels the persistence of any previous display orientation SEI messages in output order. display_orientation_cancel_flag equal to 0 may indicate that display orientation information follows. The display orientation information may include a horizontal flip flag, a vertical flip flag, a counterclockwise rotation, and a display orientation persistence flag.

[0103] A horizontal flip flag (e.g., hor_flip) equal to 1 may indicate that the cropped decoded picture is to be flipped horizontally for display. A horizontal flip flag (e.g., hor_flip) equal to 0 may indicate that the decoded picture is not to be flipped horizontally.

[0104] A vertical flip flag (e.g., ver_flip) equal to 1 may indicate that the cropped decoded picture is to be flipped vertically for display (e.g., in addition to being flipped horizontally when hor_flip is equal to 1). A vertical flip flag (e.g., ver_flip) equal to 0 may indicate that the decoded picture is not to be flipped vertically.

[0105] A counterclockwise rotation (e.g., anticlockwise_rotation) may specify a counterclockwise rotation of the decoded picture before display (e.g., after applying a horizontal flip and / or vertical flip based on the horizontal flip flag and vertical flip flag).

[0106] Equivalent transformations can be expressed in several ways using the syntax elements described above.

[0107] A display orientation persistence flag (e.g., display_orientation_persistence_flag) may specify the persistence of the display orientation SEI message for the current layer. A display orientation persistence flag (e.g., display_orientation_persistence_flag) equal to 0 may specify that the display orientation SEI message applies only to the current decoded picture. A display orientation persistence flag (e.g., display_orientation_persistence_flag) equal to 1 may specify that the display orientation SEI message may persist for the current layer in output order until one or more conditions become true. The one or more conditions may include: (i) a new CLVS for the current layer begins, (ii) the bitstream ends, and / or (iii) immediately after the invocation of the decoding process for the picture order count of the other picture, another picture of the current layer in an access unit containing a display orientation SEI message applicable to the current layer is output, where the picture order count (POC) of the other picture is greater than the POC of the current picture.

[0108] A resampling or warping process can be applied to a picture to generate a resampled picture (or warped picture). Warping processes can be used in reference picture resampling, image stabilization, compensation of global motion, etc. In one embodiment, a resampling process, such as a reference picture resampling process, is applied to a previous picture (e.g., a previously decoded reference picture) to generate a warped picture for use in predicting a current picture, as used in H.263 Annex P and described in this disclosure. In one example, the resampling syntax specifies the relationship of the current picture to previous pictures having different source formats. The reference picture resampling mode can be used to adaptively change the resolution of a picture during encoding. Fast algorithms can be used to generate bilinear interpolation coefficients. In one example, the resampling syntax specifies global motion warping changes of the shape, size, and position of the previous picture relative to the current picture, e.g., due to global motion.

[0109] 9 illustrates example vectors used for warping, according to one embodiment of this disclosure. The resampling process (e.g., reference picture resampling) (900) can be described with the displacement of four corners A-D of a current picture region (910). In the luma field of the current picture (910) with horizontal size H and vertical size V, four vectors (e.g., four conceptual MVs) v 00 , v H0 , v 0V , v HV can be defined for the top left corner A, the top right corner B, the bottom left corner C, and the bottom right corner D of the picture (910), respectively. 00 , v H0 , v 0V , v HVcan describe how to move the four corners A to D of the current picture (910) in order to map them onto the corresponding corners A' to D' of the previous decoded picture (920). 00 , v H0 , v 0V , v HV The units of x,y may be the same as those in the reference picture grid. v To generate (x,y), we can use a bilinear interpolation approximation as in Equation 1.

number

[0110] The resampling process is v (x,y) based on the horizontal and vertical size H and V of the current picture, and the horizontal size H of the reference picture. R and vertical size V R can be indicated in the picture header. In one example, if the picture width or picture height is not divisible by 16, additional area can be generated by adding pixels to the resampled picture using the same fill mode used in the resampling process.

[0111] In addition to reference picture resampling, the warping process may be used for image stabilization and / or compensation of global motion, and warping information indicating the warping parameters (e.g., four vectors) may be signaled. The warping parameters may be included in an SEI message, as described below.

[0112] This disclosure includes video coding techniques that involve SEI messages (e.g., warping-based decoded picture resampling (WDPR) SEI messages) for coding video streams. The warping process can be used in image stabilization, where an SEI message (e.g., a WDPR SEI message) can provide warping parameters used in image stabilization to reduce unintended jittering motion of the video.

[0113] The warping process can be used to compensate for global movement (or global motion) in the multiple input pictures, where warping parameters in an SEI message (e.g., a WDPR SEI message) can be used for more efficient or improved motion compensated prediction. In one embodiment, the warping process includes a forward warping process applied to the multiple input pictures as a pre-processing and a backward warping process applied to the multiple decoded pictures as a post-processing. In one example, the multiple decoded pictures correspond to the multiple input pictures.

[0114] The SEI message may be adopted as a new SEI message, such as the WDPR SEI message, or the SEI message may be combined with another existing SEI message, such as the display orientation SEI message described above with reference to Table 1. In one example, the warping process is based on the resampling process described above with reference to FIG. 9, as used in H.263 Annex P.

[0115] Image stabilization is widely used to reduce undesirable motion jitter in image sequences. For example, motion jitter is caused by camera shaking during camera shutter release or by fast moving objects. Motion anomalies caused by unstable external sources or environments can result in unpleasant visual effects in video sequences. To improve the subjective visual quality, a warping process can be applied to the decoded pictures. The warping process can be applied as a post-processing, for example at the decoder side.

[0116] FIG. 10A illustrates an exemplary warping process (1000A) in image stabilization according to one embodiment of the present disclosure. The capture side device can determine (e.g., detect or sense) camera jitter and other external motion. The frame-by-frame or picture-by-picture motion can be parameterized into warping information (e.g., warping parameters). In the example illustrated in FIG. 10A, the parameterized warping information is transmitted to the decoder side, such as through an SEI message (1051). The decoder can utilize the received warping information to apply a warping process (e.g., image stabilization process) (1000A) to a decoded picture (1053). In one example, the decoded picture (1053) is a cropped output picture with motion jitter (1005). The warped picture (1055) can be generated from the output picture (1053) cropped by the warping process (1000A). Motion jitter (1005) in the cropped output picture (1053) can be reduced to produce a stabilized picture, such as a warped picture (1055) with reduced motion jitter (1006).

[0117] As mentioned above, the warping parameters in the SEI message (e.g., WDPR SEI message) can be used for motion compensated prediction by applying a forward warping process to the input pictures as pre-processing and a backward warping process to the decoded pictures as post-processing. FIG. 10B illustrates an exemplary warping process (1000B) for compensating for global motion in the input pictures according to one embodiment of the present disclosure. In one example, the input pictures (1011)-(1013) are part of a CLVS. The input pictures (1011)-(1013) exhibit a global motion such as a shift towards the upper right direction indicated by the vector (1001). For example, the same feature is located at different positions (1091)-(1093) in the input pictures (1011)-(1013), respectively. The displacement between feature locations (e.g., locations (1091)-(1092)) in adjacent pictures (e.g., (1011)-(1012)) is vector (1001). At the encoder side, the global translation (e.g., vector (1001)) can be determined based on multiple input pictures (1011)-(1013). According to one embodiment of the present disclosure, a warping process (1000B) can be applied to multiple input pictures to improve coding efficiency as follows:

[0118] Referring to FIG. 10B, on the encoder side, a transformation, such as a shift operation opposite to the global motion, can be determined based on the global motion of the multiple input pictures (1011)-(1013). A warping parameter(s), such as a vector (1002) opposite to the vector (1001), can be determined. A forward warping process based on the vector (1002) can be applied to the multiple input pictures (1011)-(1013) to compensate for the global motion. For example, forward warped pictures (1021)-(1023) are generated from the corresponding input pictures (1011)-(1013) based on the vector (1002). Referring to FIG. 10B, static pictures (e.g., (1021)-(1023)) with similar or identical characteristics are generated from a video sequence (e.g., input pictures (1011)-(1013)) with different characteristics, and thus coding static pictures with similar characteristics may be more efficient than coding a video sequence with different characteristics, thereby improving coding efficiency.

[0119] The forward warped pictures (1021)-(1023) can be encoded at the encoder side to form a coding picture. In one example, the warping information including the warping parameter(s) (e.g., vector (1002)) or vector (1001)) is parameterized and coded in an SEI message (e.g., WDPR SEI message). In one example, the warping information (e.g., including vector (1001)) used in the unwarping process on the decoder side is denoted as unwarping information. The coding picture and the SEI message can be transmitted to the decoder side.

[0120] Referring to FIG. 10B, at the decoder side, the coding pictures can be decoded into decoded pictures (1031)-(1033), which correspond to the input pictures (1011)-(1013), respectively. The warping parameter(s) (e.g., vector (1002) or vector (1001)) can be determined based on the warping information in the encoded SEI message. To restore the original positions (1091)-(1093), an inverse warping process can be applied to the decoded pictures (1031)-(1033) to generate inverse warped pictures (1041)-(1043), thus restoring the original global motion. In the example shown in FIG. 10B, the inverse warping process includes a shift of the decoded picture in the upper right direction based on vector (1001).

[0121] The warping process (1000B) can be adapted appropriately when the global motion is more complex, such as a global motion that includes warping changes of the shape(s), size(s), and position(s) of the sequence of pictures. In one example, the global motion is represented by the four vectors of Figure 9, and the warping process (1000B) can be based on the four vectors, as described with reference to Figure 9.

[0122] FIG. 11 shows a flow chart outlining an encoding process (1100) according to one embodiment of the present disclosure. The process (1100) can be used to encode multiple input pictures. In one example, the process (1100) includes performing a forward warping process. In various embodiments, the process (1100) is performed by processing circuitry, such as processing circuitry in terminal devices (310), (320), (330), and (340), processing circuitry performing the functions of a video encoder (e.g., (403), (603), (703)). In some embodiments, the process (1100) is implemented with software instructions, and thus the processing circuitry performs the process (1100) as the processing circuitry executes the software instructions. The process starts at (S1101) and proceeds to (S1110).

[0123] At (S1110), warping parameters for the multiple input pictures can be determined based on a global translation associated with the multiple input pictures. The global translation can include warping modifications of the multiple input pictures. The warping modifications can include modification(s) to the shape(s), size(s), and / or position(s) of the multiple input pictures. The global translation can include any translation or combination of translations, such as translation(s), rotation(s), and modification(s) to the shape(s) of the multiple input pictures. For example, when the global translation includes more than translation(s) (e.g., translation(s) denoted by vector (1002) or (1001) in FIG. 10B), the global translation can be calculated by multiplying the four vectors v shown in FIG. 9 by the following: 00 , v H0 , v 0V , v HV The warping parameters can be represented by (i) a single vector (e.g., (1001) or (1002)) or (ii) multiple vectors (e.g., v 00 , v H0 , v 0V , v HV) may include horizontal component(s) and vertical component(s).

[0124] In (S1120), a warping process may be applied to the multiple input pictures based on the determined warping parameters. For example, the warping process may be a forward warping process as described with reference to FIG. 10B. A forward warped picture (e.g., (1021)-(1023)) may be generated when the global motion of the forward warped picture is smaller than the global motion of the multiple input pictures (e.g., (1011)-(1013)). Thus, encoding the forward warped picture may be more efficient than directly encoding the multiple input pictures.

[0125] When the process (1100) is used in a specific application, such as image stabilization, as in FIG. 10A, step (S1120) may be omitted in some applications.

[0126] In (S1130), the forward warped picture may be coded into a bitstream. A supplemental enhancement information (SEI) message may be coded, where the SEI message may include a first flag indicating that the warping process is applied to the multiple input pictures. The SEI message may indicate the warping parameters determined in (S1110). In one example, the SEI message is included in the bitstream.

[0127] According to one embodiment of the present disclosure, the warping process may be based on the resampling process described with reference to Figure 9. The SEI message may be a WDPR SEI message. Table 2 shows an example syntax of the WDPR SEI message syntax.

[0128] [Table 2]

[0129] The WDPR SEI message semantics can be described as follows: The WDPR SEI message can provide information for enabling a warping process of reconstructed samples of an output picture (e.g., a decoded picture) on the decoder side. In one example, the output picture (e.g., a decoded picture) is in a current layer and is part of the CLVS. With reference to FIG. 10A, the WDPR SEI message can provide information for enabling a warping process (1000A) of reconstructed samples of an output picture (e.g., a decoded picture (1053)) for the purpose of converting the output picture into a motion-stabilized picture (e.g., a warped picture (1055)) that provides a better visual experience. With reference to FIG. 10B, the WDPR SEI message can provide information for enabling a warping process (e.g., an inverse warping process in FIG. 10B) of reconstructed samples of an output picture (e.g., a decoded picture (1031)-(1033)) to restore the original global motion.

[0130] The first flag (e.g., warping_based_decoded_picture_resampling_cancel_flag) being true (e.g., equal to 1) may indicate that the WDPR SEI message cancels the persistence of any previous WDPR SEI messages in the output order applied to the current layer. The first flag (e.g., warping_based_decoded_picture_resampling_cancel_flag) being false (e.g., equal to 0) may indicate that warping information (e.g., WDPR information) follows. In one example, warping information is signaled when the first flag (e.g., warping_based_decoded_picture_resampling_cancel_flag) is false.

[0131] In one example, the first flag (e.g., warping_based_decoded_picture_resampling_cancel_flag) indicates whether the warping process is applied to the multiple input pictures. The first flag being true (e.g., equal to 1) may indicate that the warping process is not applied to the multiple input pictures. The first flag being false (e.g., equal to 0) may indicate that the warping process is applied to the multiple input pictures.

[0132] The warping information may include a second flag (eg, warping_based_decoded_picture_resampling_persistence_flag), a warping mode identifier (eg, warping_mode_idc), and warping parameters.

[0133] A second flag (e.g., warping_based_decoded_picture_resampling_persistence_flag) may specify persistence of the WDPR SEI message. The persistence may be specified, for example, for the current layer. The second flag (e.g., warping_based_decoded_picture_resampling_persistence_flag) being false (e.g., equal to 0) may specify that the WDPR SEI message applies only to the current decoded picture. For example, the current decoded picture is one of the output pictures of the current layer. The second flag (e.g., warping_based_decoded_picture_resampling_persistence_flag) being true (e.g., equal to 1) may specify that the WDPR SEI message applies to the current decoded picture and persists for all subsequent pictures of the current layer in output order until one or more conditions become true. The conditions may include one or more of: (i) a new CLVS for the current layer begins; (ii) the bitstream ends; and (iii) a picture of the current layer in an AU associated with a WDPR SEI message (e.g., different from the WDPR SEI message for the current decoded picture) that follows the current decoded picture in output order is output.

[0134] The warping mode identifier (e.g., warping_mode_idc) may specify a warping mode to be applied to the output picture (e.g., a cropped output picture). In one example, a warping mode identifier (e.g., warping_mode_idc) equal to 0 specifies that the warping process described above with reference to FIG. 9 (e.g., used in H.263 Annex P) with four corner vectors including eight parameters is applied. The warping parameters may include four corner vectors or eight parameters. When the warping mode identifier (e.g., warping_mode_idc) is equal to 0, four corner vectors, denoted as (corner_vector_x[i], corner_vector_y[i]), are present in the SEI message. Other values ​​of the warping mode identifier may indicate other warping modes. In one example, values ​​of the warping mode identifier (e.g., warping_mode_idc) greater than 1 are reserved for future use by ITU-T|ISO / IEC, etc.

[0135] The corner vectors are denoted by the variables corner_vector_x[i] and corner_vector_y[i]. Referring back to Figure 9, the four corner vectors v 00 , v H0 , v 0V , v HV The warping parameters, such as the values ​​of (corner_vector_x[0],corner_vector_y[0]), (corner_vector_x[1],corner_vector_y[1]), (corner_vector_x[2],corner_vector_y[2]), and (corner_vector_x[3],corner_vector_y[3]), respectively.

[0136] The process (1100) proceeds to (S1199) and ends.

[0137] The process (1100) can be adapted to various scenarios, and the steps in the process (1100) can be adjusted accordingly. One or more of the steps in the process (1100) can be adapted, omitted, repeated, and / or combined. Any suitable order can be used to perform the process (1100). Additional step(s) can be added.

[0138] In one example, the warping information described with reference to Table 2 is included in another SEI message, such as a display orientation SEI message. For example, one or more syntax elements of Table 2 are combined with the syntax elements of Table 1.

[0139] In one example, the process (1100) is used in a specific application that does not require step (S1120). For example, if the application is image stabilization, (S1120) can be omitted. The warping information in the SEI message can be used by the decoder at the decoder side to perform a warping process based on the warping information. (S1130) can be adapted so that multiple input pictures are coded instead of a forward warped picture.

[0140] In one example, the process (1100) is used to reduce global motion, and (S1120) is performed as a forward warping process. The warping information in the SEI message can be used by the decoder at the decoder side to perform a reverse warping process based on the warping information.

[0141] In one example, whether to perform a warping process on the multiple input pictures is determined based on global translation or motion jitter. If it is determined that the warping process is performed on the multiple input pictures at the encoder side and / or the corresponding decoded pictures at the decoder side, one or more steps of the process (1100) may be performed as described in this disclosure. If it is determined that the warping process is not performed, steps (S1110) and (S1120) are omitted. (S1130) may be adapted such that the multiple input pictures are encoded and the SEI message is not encoded.

[0142] FIG. 12 shows a flow chart outlining a decoding process (1200) according to one embodiment of the present disclosure. The process (1200) can be used to decode a current picture in a bitstream and perform a warping process on the current decoded picture. In various embodiments, the process (1200) is performed by processing circuitry in terminal devices (310), (320), (330), and (340), processing circuitry performing the functions of a video encoder (403), processing circuitry performing the functions of a video decoder (410), processing circuitry performing the functions of a video decoder (510), processing circuitry performing the functions of a video encoder (603), etc. In some embodiments, the process (1200) is implemented in software instructions, and thus the processing circuitry performs the process (1200) as the processing circuitry executes the software instructions. The process starts at (S1201) and proceeds to (S1210).

[0143] At (S1210), the current picture can be decoded based on the bitstream.

[0144] At (S1220), first information (e.g., a first flag) indicating whether a warping process is applied to the current decoded picture may be determined from the SEI message. In one example, the SEI message is a display orientation SEI message in a bitstream, where the display orientation SEI message includes syntax elements (e.g., a first flag, a second flag, a warping mode identifier, and a corner vector) as shown in Table 2. In one example, the SEI message is a WDPR SEI message in a bitstream, as described with reference to Table 2.

[0145] In one example, the first flag is denoted as warping_based_decoded_picture_resampling_cancel_flag described above. The first flag being false (e.g., equal to 0) may indicate that warping information is included in the SEI message and a warping process is applied. The first flag (e.g., warping_based_decoded_picture_resampling_cancel_flag) being true (e.g., equal to 1) may indicate that the SEI message cancels the persistence of any previous WDPR SEI messages in the output order applied to the current layer and that a warping process is not applied.

[0146] At (S1230), warping information of the warping process may be determined based on the SEI message based on first information (e.g., a first flag) indicating that the warping process is applied to the current decoded picture.

[0147] The warping information is the four corner vectors between the corners of the current decoded picture and the corresponding corners of the warped picture (e.g., v 00 , v H0 , v 0V , v HVIn some examples, the warping parameters may include a vector indicating a shift operation (e.g., vector (1001) or (1002) in FIG. 10B).

[0148] In one example, the warping information may indicate a warping mode (eg, a warping mode having a warping mode identifier of 0), and the four corner vectors may be determined based on the warping mode.

[0149] The warping information may include second information (e.g., a second flag). In one example, the second flag is denoted as warping_based_decoded_picture_resampling_persistence_flag. The second flag having a first value (e.g., 0) indicates that the SEI message applies only to the current decoded picture. The second flag having a second value (e.g., 1) indicates that the SEI message applies to the current decoded picture and one or more subsequent decoded pictures of the current layer in output order until a condition is met. The condition may include one or more of the following: (i) a new CLVS for the current layer begins; (ii) the bitstream ends; (iii) a picture of the current layer in an AU associated with a WDPR SEI message (e.g., different from the SEI message for the current decoded picture) following the current decoded picture in output order is output.

[0150] At (S1240), the warped picture may be determined from the currently decoded picture based on warping information such as warping parameters. In one example, the warping parameters may be determined based on four corner vectors (e.g., v 00 , v H0 , v 0V , v HV ), and vectors between sample positions in the current decoded picture and corresponding positions in the warped picture may be determined based on the four corner vectors, e.g., using Equation 1.

[0151] In one example, the second flag has a second value indicating that the SEI message applies to the current decoded picture and one or more subsequent decoded pictures of the current layer in output order. Subsequent pictures of the current layer that follow the current picture in output order may be decoded. Subsequent warping pictures may be determined from the subsequent decoded pictures based on the warping information.

[0152] The process (1200) proceeds to (S1299) and ends.

[0153] Process (1200) can be adapted to various scenarios as appropriate, and steps within process (1200) can be adjusted accordingly. One or more of the steps within process (1200) can be adapted, omitted, repeated, and / or combined. Any suitable order can be used to perform process (1200). Additional step(s) can be added.

[0154] In one example, based on the first flag indicating that the warping process indicated by the previous SEI message is canceled, the warping process is not applied to the current decoded picture. Thus, steps (S1230) and (S1240) are omitted.

[0155] The process (1200) can be used in certain applications, such as image stabilization, as shown in FIG. 10A, where no corresponding warping process is performed on the encoder side. The process (1200) can be used as an inverse warping process to compensate for global motion, as shown in FIG. 10B, where a corresponding forward warping process is performed on the encoder side. In one example, the warping parameters in the SEI message are adapted based on whether the process (1200) is for image stabilization or an inverse warping process to compensate for global motion. In one example, the warping parameters in the SEI message used for image stabilization or an inverse warping process in compensating for global motion are the same, and (S1240) can be adapted based on whether the process (1200) is for image stabilization or an inverse warping process to compensate for global motion.

[0156] The embodiments of the present disclosure may be used separately or combined in any order. Furthermore, each of the methods (or embodiments), the encoder, and the decoder may be implemented by a processing circuit (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.

[0157] The techniques 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 13 illustrates a computer system (1300) suitable for implementing certain embodiments of the disclosed subject matter.

[0158] Computer software can be coded using any suitable machine code or computer language that can be assembled, compiled, linked, or similar mechanisms to create code containing instructions that can be executed directly, or via interpretation, microcode execution, etc., by one or more computer central processing units (CPUs) and graphics processing units (GPUs), etc.

[0159] The instructions may be executed on various types of computers or computer components including, for example, personal computers, tablet computers, servers, smart phones, gaming consoles, Internet of Things devices, and the like.

[0160] 13 for computer system (1300) are exemplary in nature and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing the embodiments of the present disclosure. The arrangement of components should not be interpreted as having any dependency or requirement regarding any one or combination of components illustrated in the exemplary embodiment of computer system (1300).

[0161] The computer system (1300) may include certain human interface input devices. Such human interface input devices may be responsive to input by one or more human users, for example, via tactile input (keystrokes, swipes, data glove movements, etc.), audio input (voice, clapping, etc.), visual input (gestures, etc.), and olfactory input (not shown). The human interface devices may also be used to capture certain media not necessarily directly associated with conscious human input, such as audio (speech, music, ambient sounds, etc.), images (scanned images, photographic images obtained from still image cameras, etc.), and video (two-dimensional video, three-dimensional video including stereoscopic video, etc.).

[0162] The input human interface devices may include one or more of a keyboard (1301), a mouse (1302), a trackpad (1303), a touch screen (1310), a data glove (not shown), a joystick (1305), a microphone (1306), a scanner (1307), and a camera (1308) (only one of each is depicted).

[0163] The computer system (1300) may also include certain human interface output devices. Such human interface output devices may stimulate one or more of the senses of a human user, for example, through haptic output, sound, light, and smell / taste. Such human interface output devices may include haptic output devices (e.g., haptic feedback via a touch screen (1310), data gloves (not shown), or joystick (1305), although there may be haptic feedback devices that do not function as input devices), audio output devices (such as speakers (1309), headphones (not depicted)), visual output devices (such as screens (1310), including CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch screen input capability, each with or without haptic feedback capability, some of which may be capable of outputting two-dimensional visual output or three-dimensional or higher output via means such as stereographic output, virtual reality glasses (not depicted), holographic displays, and smoke tanks (not depicted)), and printers (not depicted).

[0164] The computer system (1300) may also include human-accessible storage devices and their associated media, such as optical media, including CD / DVD ROM / RW (1320) with CD / DVD or similar media (1321), thumb drives (1322), removable hard drives or solid state drives (1323), legacy magnetic media (not depicted) such as tapes and floppy disks, and specialized ROM / ASIC / PLD based devices (not depicted) such as security dongles.

[0165] Those skilled in the art should also understand that the term "computer-readable medium" as used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transitory signals.

[0166] The computer system (1300) may also include an interface (1354) to one or more communication networks (1355). The networks may be, for example, wireless, wired, optical. The networks may further be local, wide area, metropolitan, vehicular and industrial, real-time, delay tolerant, etc. Examples of networks include local area networks such as Ethernet, wireless LAN, cellular networks including GSM, 3G, 4G, 5G, LTE, etc., television wired or wireless wide area digital networks including cable television, satellite television, and terrestrial broadcast television, vehicular and industrial including CANBus, etc. Certain networks typically require an external network interface adapter connected to a particular general-purpose data port or peripheral bus (1349) (e.g., a USB port on the computer system (1300)), while others are generally integrated into the core of the computer system (1300) by connecting to a system bus, as described below (e.g., an Ethernet interface for a PC computer system, or a cellular network interface for a smartphone computer system). Using any of these networks, the computer system (1300) may communicate with other entities. Such communications may be one-way, receive-only (e.g., television broadcast), one-way transmit-only (e.g., from a CANbus to a particular CANbus device), or two-way, e.g., to other computer systems using local or wide area digital networks. Specific protocols and protocol stacks may be used with each of these networks and network interfaces, as described above.

[0167] The aforementioned human interface devices, human accessible storage devices, and network interfaces may be attached to a core (1340) of the computer system (1300).

[0168] The cores (1340) may include one or more central processing units (CPUs) (1341), graphics processing units (GPUs) (1342), dedicated programmable processing units in the form of field programmable gate areas (FPGAs) (1343), hardware accelerators for specific tasks (1344), graphics adapters (1350), and the like. These devices may be connected through a system bus (1348), along with read only memory (ROM) (1345), random access memory (1346), and internal mass storage (1347), such as an internal non-user accessible hard drive, SSD, and the like. In some computer systems, the system bus (1348) may be accessible in the form of one or more physical plugs to allow expansion with additional CPUs, GPUs, and the like. Peripheral devices may be attached directly to the core's system bus (1348) or through a peripheral bus (1349). In one example, a screen (1310) may be connected to a graphics adapter (1350). Peripheral bus architectures include PCI, USB, and the like.

[0169] The CPU (1341), GPU (1342), FPGA (1343) and accelerator (1344) may combine to execute certain instructions that may constitute the computer code described above. That computer code may be stored in ROM (1345) or RAM (1346). Persistent data may be stored, for example, in internal mass storage (1347), while transitory data may also be stored in RAM (1346). Rapid storage and retrieval from any of the memory devices may be enabled using cache memory, which may be closely associated with one or more of the CPU (1341), GPU (1342), mass storage (1347), ROM (1345), RAM (1346), etc.

[0170] The computer-readable medium can bear computer code for performing various computer-implemented operations. The medium and computer code may be those specially designed and constructed for the purposes of the present disclosure, or they may be of the available kind well known to those skilled in the computer software arts.

[0171] By way of example and not limitation, a computer system (1300) having an architecture, and specifically a core (1340), may provide functionality as a result of a processor (or processors) (including CPUs, GPUs, FPGAs, accelerators, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media may be user-accessible mass storage as described above, as well as media associated with specific storage of the core (1340) that is non-transitory in nature, such as the core internal mass storage (1347) or ROM (1345). Software implementing various embodiments of the present disclosure may be stored in such devices and executed by the core (1340). The computer-readable media may include one or more memory devices or chips, depending on the particular needs. The software may cause the core (1340), and specifically the processors therein (including CPUs, GPUs, FPGAs, etc.) to perform certain processes or certain portions of certain processes described herein, including defining data structures stored in RAM (1346) and modifying such data structures according to processes defined by the software. Additionally, or alternatively, a computer system may provide functionality as a result of hardwired or otherwise embodied logic in circuitry (e.g., accelerator (1344)) that can operate in place of or in conjunction with software to perform particular processes or particular portions of particular processes described herein. References to software may encompass logic, and vice versa, where appropriate. Where appropriate, references to computer-readable media may encompass circuitry (such as an integrated circuit (IC)) that stores software for execution, circuitry that embodies logic for execution, or both. The present disclosure encompasses any suitable combination of hardware and software.

[0172] Appendix A: Acronyms JEM: Joint Exploration Model VVC: Versatile Video Coding BMS: Benchmark Set MV: Motion Vector HEVC: High Efficiency Video Coding SEI:Supplementary Enhancement Information VUI: Video Usability Information GOP: Group of Pictures TU: conversion unit PU: Prediction unit CTU: Coding Tree Unit CTB: coding tree block PB: Predicted block HRD: Hypothetical Reference Decoder SNR: Signal to Noise Ratio CPU: Central Processing Unit GPU: Graphics Processing Unit CRT: cathode ray tube LCD: Liquid crystal display OLED: Organic Light Emitting Diode CD:Compact Disc DVD: Digital Video Disc ROM: Read-Only Memory RAM: Random Access Memory ASIC: Application Specific Integrated Circuit PLD: Programmable Logic Device LAN: Local Area Network GSM: Global System for Mobile Communications LTE: Long Term Evolution CANBus: Controller Area Network Bus USB: Universal Serial Bus PCI: Peripheral Component Interconnect FPGA: Field Programmable Gate Area SSD: Solid State Drive IC: Integrated Circuit CU: coding unit RD: Rate Distortion

[0173] While this disclosure has described several exemplary embodiments, there are modifications, substitutions, and various substitute equivalents, which are 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 which, 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]

[0174] 101 Samples 102 Arrow 103 Arrow 104 Block 201 Current Block 202 Ambient Samples 203 Ambient Samples 204 Ambient Samples 205 Ambient Samples 206 Ambient Samples 300 Communication Systems 310 Terminal Devices 320 Terminal Devices 330 Terminal Devices 340 Terminal Devices 350 Network 400 Communication Systems 401 Video Source 402 Stream 403 Video Encoder 404 Encoded Video Data 405 Streaming Server 406 Client Subsystem 407 Copy 408 Client Subsystem 409 Copy 410 Video Decoder 411 Output Stream 412 Display 413 Capture Subsystem 420 Electronic Devices 430 Electronic Devices 501 Channel 510 Video Decoder 512 Rendering Device 515 Buffer Memory 520 Parser 521 Symbols 530 Electronic Devices 531 Receiver 551 Scaler / Descaler Unit 552 Intra-picture prediction unit 553 Motion Compensation Prediction Unit 555 Aggregator 556 Loop Filter Unit 557 Reference Picture Memory 558 Current Picture Buffer 601 Video Sources 603 Video Encoder 620 Electronic Devices 630 Source Coder 632 Coding Engine 633 Local Decoder 634 Reference Picture Memory 635 Predictor 640 Transmitter 643 coding video sequence 645 Entropy Coder 650 Controller 660 Communication Channels 703 Video Encoder 721 General-purpose controller 722 Intra Encoder 723 Residual Calculator 724 Residual Encoder 725 Entropy Encoder 726 Switch 728 Residual Decoder 730 InterEncoder 810 Video Decoder 871 Entropy Decoder 872 Intra Decoder 873 Residual Decoder 874 Reconstruction Module 880 Interdecoder 900 Resampling Process 910 Current Picture Area 920 previous decoded picture 1000A Warping Process 1000B Warping Process 1001 Vector 1002 Vector 1005 Motion Jitter 1006 Motion Jitter 1011 Input Picture 1012 Input Picture 1013 Input Picture 1021 forward warping picture 1022 forward warping picture 1023 forward warping picture 1031 Decoded Picture 1032 Decoded Picture 1033 Decoded Picture 1041 Unwarped Pictures 1042 Unwarped Picture 1043 Unwarped Picture 1051 Supplemental Enhancement Information (SEI) Message 1053 Decoded Picture 1055 Warping Picture 1091 position 1092 position 1093 position 1100 Encoding Process 1200 Decryption Process 1300 Computer Systems 1301 Keyboard 1302 Mouse 1303 Trackpad 1305 Joystick 1306 Microphone 1307 Scanner 1308 Camera 1309 Speaker 1310 Touch Screen 1320 CD / DVD ROM / RW 1321 Medium 1322 Thumb Drive 1323 Removable Hard Drive or Solid State Drive 1340 cores 1341 Central Processing Unit (CPU) 1342 Graphics Processing Unit (GPU) 1343 Field Programmable Gate Area (FPGA) 1344 Hardware Accelerator 1345 Read-Only Memory (ROM) 1346 Random Access Memory 1347 Internal Mass Storage 1348 System Bus 1349 Surrounding bus 1350 Graphics Adapter 1354 Interface 1355 Communication Network

Claims

1. A method for video decoding performed by a video decoder, comprising: decoding a current picture included in the plurality of pictures based on the video bitstream; determining a first flag from a supplemental enhancement information (SEI) message indicating whether a warping process is applied to the current decoded picture; determining warping information of the warping process based on the SEI message based on the first flag indicating that the warping process is applied to the current decoded picture; determining a warped picture from the current decoded picture based on the warping information; The method of claim 1, wherein the warping information indicates a shift operation that is opposite to a determined global movement among the plurality of pictures.

2. The SEI message is a display orientation SEI message in the video bitstream. The method of claim 1.

3. The method described in claim 1, wherein the SEI message is a warping-based decoded picture resampling (WDPR) SEI message in the video bitstream.

4. The step of determining the warped picture comprises:

2. The method of claim 1, comprising determining vectors between sample positions in the current decoded picture and corresponding positions in the warped picture based on four corner vectors between corners of the current picture and corresponding corners of the warped picture.

5. The method of claim 4, wherein the warping process is not applied to the current decoded picture based on the first flag indicating that the warping process indicated by a previous SEI message has been canceled. The method of claim 1.

6. The warping information includes a second flag, the SEI message applies to only the current decoded picture based on the second flag having a first value; based on the second flag having a second value, the SEI message is applied to the current decoded picture and one or more subsequently decoded pictures of the current layer in output order until a condition is met. The method of claim 1.

7. The second flag has the second value, The method comprises: decoding a subsequent picture of the current layer that follows the current picture in the output order; and determining a warped picture from the subsequently decoded picture based on the warping information. The method of claim 6.

8. The method described in claim 6, wherein the condition includes the start of a new coding layer video sequence (CLVS) for the current layer.

9. The method of claim 6, wherein the condition includes the end of the video bitstream.

10. The warping information includes a warping mode, determining the warping information includes determining four corner vectors between corners of the current picture and corresponding corners of the warped picture based on the warping mode; The method of claim 1.

11. An apparatus configured to perform the method of any one of claims 1 to 10.

12. A computer program for causing a computer to execute the method according to any one of claims 1 to 10.

13. A method for video encoding performed by a video encoder, comprising: determining a global motion associated with a plurality of pictures including the current picture; generating a supplemental enhancement information (SEI) message including a first flag indicating whether a warping process is applied to the current picture; generating a video bitstream including coding information for the plurality of pictures and including the SEI message; Including, The method, wherein the warping process generates a warped picture by applying a shift operation to the current picture that is opposite to the global translation.

14. The method described in claim 13, wherein the SEI message is a display orientation SEI message in the video bitstream.

15. The method described in claim 13, wherein the SEI message is a warping-based decoded picture resampling (WDPR) SEI message in the video bitstream.

16. The method described in claim 13, further comprising a step of determining four corner vectors between corners of the current picture and corresponding corners of the warped picture to indicate vectors between sample positions in the current picture and corresponding positions in the warped picture.

17. The method described in claim 13, wherein when the first flag indicates that the warping process indicated by the previous SEI message has been canceled, the warping process is not applied to the current picture.

18. The SEI message includes a second flag; When the SEI message applies to the current picture only, the second flag has a first value; 14. The method of claim 13, wherein the second flag has a second value when the SEI message is applied to the current picture and one or more subsequently decoded pictures of a current layer in output order until a condition is met.

19. The second flag has the second value, The method of claim 18 , wherein the warping process is applied to subsequent pictures of the current layer that follow the current picture in the output order.

20. The method of claim 18, wherein the condition includes the start of a new coding layer video sequence (CLVS) for the current layer.

21. The method of claim 18, wherein the condition includes the end of the video bitstream.

22. An apparatus configured to perform a method according to any one of claims 13 to 21.

23. A computer program for causing a computer to execute the method according to any one of claims 13 to 21.

24. A method for processing virtual media data, the method comprising: performing a conversion between the virtual media file and a video bitstream of the virtual media data according to a format rule; the video bitstream includes a supplemental enhancement information (SEI) message including a first flag indicating whether a warping process is applied to a current picture included in a plurality of pictures; the format rules specify that warping information of the warping process is determined based on the SEI message, based on the first flag indicating that the warping process is to be applied to the current picture; a warped picture is generated from the current picture based on the warping information; The method of claim 1, wherein the warping information indicates a shift operation that is opposite to a determined global movement among the plurality of pictures.

25. An apparatus configured to perform the method of claim 24.

26. A computer program for causing a computer to carry out the method according to claim 24.

27. A computer-implemented method for storing a video bitstream, comprising: generating a video bitstream, determining a global motion associated with a plurality of pictures including the current picture; generating a supplemental enhancement information (SEI) message including a first flag indicating whether a warping process is applied to the current picture; generating a video bitstream including coding information for the plurality of pictures and including the SEI message; Including, generating a video bitstream, the warping process generating a warped picture by applying a shift operation to the current picture that is opposite to the global translation; storing the video bitstream on a computer-readable non-transitory storage medium; A method comprising:

28. An apparatus configured to perform the method of claim 27.

29. A computer program for causing a computer to carry out the method according to claim 27.

Images