Adjustment based local illumination compensation

Abstract

To provide a method and an apparatus for a video decoding.SOLUTION: An apparatus includes a processing circuit to decode prediction information of one or more blocks including a current block from a coded video bitstream. The prediction information indicates that a local illumination compensation (LIC) is applied to one or more blocks, and includes LIC information of the one or more blocks. The processing circuit determines a final scaling factor αf1 and a final offset βf1 of a first sub-block in a current block based on the LIC information. The processing circuit determines an updated first predictor sub-block in a predictor corresponding to the current block based on the final scaling factor αf1, the final offset βf1, and the first predictor sub-block. An updated value of a first sample in the first predictor sub-block is equal to αf1×pi1+βf1. The pi1 is a value of the first sample.SELECTED DRAWING: Figure 19

Description

Technical Field

[0001] INCORPORATION BY REFERENCE This application claims the benefit of priority to U.S. Provisional Application No. 63 / 298,788, filed on Jan. 12, 2022, entitled “ADJUSTMENT BASED LOCAL ILLUMINATION COMPENSATION,” and to U.S. Patent Application No. 17 / 903,697, filed on Sep. 6, 2022, entitled “ADJUSTMENT BASED LOCAL ILLUMINATION COMPENSATION.” The disclosure of the prior applications is hereby incorporated by reference in its entirety.

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

Background Art

[0003] The description of the background art provided herein is for the purpose of generally presenting the context of the disclosure. Aspects of the description that are not within the scope of this background art section and that might not have been considered prior art at the time of filing are not admitted to be prior art to this disclosure, either expressly or by implication.

[0004] Uncompressed digital images and / or video can include a series of pictures, each of which can have, for example, a spatial dimension of 1920×1080 luminance samples and associated chrominance samples. The series of pictures can have, for example, a fixed or variable picture rate of 60 pictures per second or 60 Hz (informally also known as the frame rate). Uncompressed images and / or video have specific bitrate requirements. For example, 1080p60 4:2:0 video (1920×1080 luminance sample resolution at a frame rate of 60 Hz) with 8 bits per sample requires a bandwidth close to 1.5 Gbit / s. One hour of such video requires storage space exceeding 600 GBytes.

[0005] One purpose of the coding and decoding of images and / or videos can be the reduction of redundancy in the input image and / or video signal by compression. Compression can help reduce the aforementioned bandwidth and / or memory space requirements, in some cases by more than two orders of magnitude. The description in this specification uses video encoding / decoding as an example, but the same techniques can be applied to the encoding / decoding of images in a similar manner without departing from the spirit of the present disclosure. It is possible to employ both reversible compression and irreversible compression, and combinations thereof. Reversible compression refers to a technique in which an exact copy of the original signal can be reconstructed from the compressed original signal. When using irreversible 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 its intended purpose. In the case of video, irreversible compression is widely adopted. The amount of distortion tolerated depends on the application. For example, a user of a particular consumer streaming application can tolerate higher distortion than a user of a television distribution application. The achievable compression ratio may reflect the fact that higher acceptable / tolerable distortion can result in a higher compression ratio.

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

[0007] Video coding technology can include techniques known as intracoding. In intracoding, sample values are represented without reference to samples from previously reconstructed reference pictures or other data. In some video coders, a picture is spatially subdivided into blocks of samples. When all blocks of samples are coded in an intra mode, that picture can be an intra picture. Those derivatives such as intra pictures and independent decoder refresh pictures can be used to reset the decoder state and thus can be used as the first picture in a coded video bitstream and video session or as a still image. Samples of an intra block can undergo a transform, and the transform coefficients can be quantized prior to entropy coding. Intra prediction can be a technique that minimizes sample values in a pre-transform region. In some cases, the smaller the post-transform DC value 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] For example, conventional intracoding used in MPEG-2 generation coding technology does not use intra prediction. However, some newer video compression technologies include techniques that attempt to perform prediction based on, for example, surrounding sample data and / or metadata obtained during encoding and / or decoding of blocks of data. Such techniques are hereinafter referred to as "intra prediction" techniques. Note that in at least some cases, intra prediction uses only reference data from the current picture being reconstructed and does not use reference data from reference pictures.

[0009] Intra prediction can have many different forms. When two or more of such techniques can be used in a given video coding technique, the particular technique in use can be coded as a particular intra prediction mode that uses the particular technique. In certain cases, the intra prediction mode can have sub - modes and / or parameters, and the sub - modes and / or parameters can be coded individually or can be included in a mode codeword that defines the prediction mode being used. Which codeword to use for a given combination of mode, sub - mode, and / or parameter can affect the coding efficiency improvement through intra prediction, and thus can also affect the entropy coding technique used to convert the codeword into a bitstream.

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

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

[0012] Referring further to FIG. 1A, a square block (104) of 4×4 samples in the upper left is shown (indicated by the thick dashed line). The square block (104) contains 16 samples, each labeled with its position in the "S", 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 within block (104). Since the block is 4×4 samples in size, S44 is in the lower right. Reference samples following a similar numbering scheme are further shown. The reference samples are labeled with "R", their Y position (e.g., row index) relative to block (104), and their X position (column index). In both H.264 and H.265, the predicted samples are adjacent to the block being reconstructed, and thus negative values need not be used.

[0013] Intra-picture prediction can function by copying the reference sample value from adjacent samples indicated by the signaled prediction direction. For example, a coded video bitstream includes signaling indicating a prediction direction that matches arrow (102) for this block, i.e., it is assumed that the samples are predicted at an angle of 45 degrees from horizontal, going from sample to the upper right. In that case, samples S41, S32, S23, S14 are predicted from the same reference sample R05. Then, sample S44 is predicted from reference sample R08.

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

[0015] The number of possible directions has been increasing as video coding technology develops. In H.264 (2003), nine different directions could be represented. This increased to 33 in H.265 (2013). Currently, 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 less likely directions. Furthermore, the direction itself may be predicted from adjacent directions used in adjacent, already decoded blocks.

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

[0017] The mapping of intra prediction direction bits representing directions within a coded video bitstream can vary depending on the video coding technology. Such mapping can range from simple direct mapping to complex adaptive schemes including codewords, most probable modes, and similar techniques. However, in most cases, there can exist certain directions within the video content that are statistically less likely to occur than certain other directions. Since the purpose of video compression is redundancy reduction, those less likely directions are represented with more bits than the more likely directions in a well - functioning video coding technology.

[0018] Coding and decoding of images and / or video can be performed using inter - picture prediction with motion compensation. Motion compensation can be an irreversible compression technique, and is related to a technique in which a block of sample data from a previously reconstructed picture or a part thereof (reference picture) is spatially shifted in the direction indicated by a motion vector (hereinafter, MV) and then used for prediction of a newly reconstructed picture or a part of the picture. In some cases, the reference picture can be the same as the picture currently being reconstructed. The MV can have two dimensions X and Y, or three dimensions, where the third dimension is an indication of the reference picture in use (the latter can be indirectly the temporal dimension).

[0019] In some video compression techniques, the motion vectors (MVs) applicable to a particular area of sample data can be predicted from other MVs, for example, from MVs related to other areas of sample data that are spatially adjacent to the area being reconstructed and that precede that MV in decoding order. By doing so, the amount of data required for coding the MVs can be significantly reduced, thereby eliminating redundancy and increasing the compression ratio. MV prediction can function effectively, for example, when coding an input video signal derived from a camera (known as natural video), because areas larger than the area to which a single MV is applicable move in a similar direction and thus, in some cases, there is a statistical likelihood that they can be predicted using a similar motion vector derived from the MVs of adjacent areas. As a result, the MV detected for a given area becomes similar or identical to the MV predicted from surrounding MVs, which can be represented in fewer bits than the number of bits that would have been used if the MV were coded directly, after entropy coding. In some cases, MV prediction can be an example of lossless compression of a signal (i.e., the MV) derived from the original signal (i.e., the sample stream). In other cases, MV prediction itself can be lossy, for example, due to rounding errors when calculating predictors 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). Of the many MV prediction mechanisms provided by H.265, the one described with reference to FIG. 2 is a technique hereinafter referred to as "spatial merge".

[0021] Referring to FIG. 2, the current block (201) is found to include samples that can be predicted from previous blocks of the same size that have been spatially shifted by the encoder during the motion search process. Instead of directly coding the MV, the MV can be derived from metadata associated with one or more reference pictures, for example, from the latest reference picture (in decoding order), using the MV associated with any one of five surrounding samples denoted as A0, A1, and B0, B1, B2 (202 to 206 respectively). In H.265, MV prediction can use predictors from the same reference picture that adjacent blocks are using. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0022] Aspects of the present disclosure provide methods and apparatus for video encoding and decoding. In some examples, an apparatus for video decoding includes processing circuitry. The processing circuitry is configured to decode prediction information for one or more blocks from a coded video bitstream. The prediction information indicates that local illumination compensation (LIC) is applied to one or more blocks and includes LIC information for the one or more blocks. The one or more blocks include a current block to be reconstructed. The processing circuitry determines a final scaling factor α f1 and a final offset β f1 for a first sub-block within the current block based on the LIC information. The processing circuitry determines an updated first predictor sub-block within a predictor corresponding to the current block based on the final scaling factor α f1 , the final offset β f1 , and a first predictor sub-block. In one example, the updated value of a first sample within the first predictor sub-block in the predictor is equal to α f1 ×p i1 +β f1 where p i1is the value of the first sample in the first predictor sub-block in the predictor. The processing circuit reconstructs the first sub-block in the current block based on the updated first predictor sub-block in the predictor.

[0023] In one embodiment, the initial scaling factor α of the first sub-block in the current block i1 and the initial offset β of the first sub-block in the current block i1 are determined based on the first part of the current template of the current block and the first part of the reference template of the reference block. The predictor can be based on the reference block. The LIC information of one or more blocks is signaled in the coded video bitstream, indicating at least one of the first parameter μ1 of the one or more blocks and the second parameter μ2 of the one or more blocks. The processing circuit determines the final scaling factor α of the first sub-block in the current block based on the first parameter μ1 of the one or more blocks and the initial scaling factor α of the first sub-block in the current block i1 The processing circuit determines the final offset β of the first sub-block in the current block based on the second parameter μ2 of the one or more blocks and the initial offset β of the first sub-block in the current block f1 i1 f1

[0024] In one example, the LIC information of one or more blocks indicates (i) the first parameter μ1 and (ii) one of the second parameters μ2, and the other of (i) the first parameter μ1 and (ii) the second parameters μ2 is determined based on one of (i) the first parameter μ1 and (ii) the second parameters μ2.

[0025] In one example, one of (i) the first parameter μ1 and (ii) the second parameters μ2 is equal to zero, and the LIC information of one or more blocks does not indicate one of (i) the first parameter μ1 and (ii) the second parameters μ2. ​​​

[0026] In one example, the LIC information of one or more blocks includes at least one index indicating at least one of the first parameter μ1 or the second parameter μ2.

[0027] In one example, at least one of the first parameter μ1 or the second parameter μ2 is a floating-point value, quantized in multiple bits, and the LIC information of one or more blocks includes multiple bits.

[0028] In one example, the processing circuit determines the final scaling factor α of the first sub-block within the current block f1 to be the sum of the first parameter μ1 of one or more blocks and the initial scaling factor α of the first sub-block within the current block i1 .

[0029] In one example, the processing circuit determines the parameter T of the first sub-block within the current block based on at least one of the first part of the current template or the first part of the reference template avg,1 , and determines the final offset β of the first sub-block within the current block f1 to be (β i1 + μ2 × T avg,1 ).

[0030] In one example, the LIC information of one or more blocks is signaled at the coding unit (CU) level.

[0031] In one example, the LIC information of one or more blocks is signaled at a level higher than the CU level.

[0032] In one example, the first sub-block includes the current block, the first predictor sub-block includes the predictor, the first part of the current template includes the current template, and the first part of the reference template includes the reference template.

[0033] In one example, the current block includes a first sub-block and a second sub-block, and at least one of a first parameter μ1 or a second parameter μ2 indicated in the LIC information of one or more blocks is applied to the first sub-block and the second sub-block, and the second sub-block has an initial scaling factor α i1 different from that of the first sub-block i2 and a different initial offset β from the initial offset of the first sub-block i2 associated therewith.

[0034] 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.

[0035] Further features, properties, 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

[0036]

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DETAILED DESCRIPTION OF THE INVENTION

[0037] Figure 3 shows an exemplary block diagram of a communication system (300). 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 a 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) may code video data (e.g., a stream of video pictures captured by the terminal device (310)) for transmission to the other terminal device (320) via the network (350). The coded video data may be transmitted in the form of one or more coded video bitstreams. The terminal device (320) may receive the coded video data from the network (350), decode the coded video data to recover the video pictures, and display the video pictures according to the recovered video data. Unidirectional data transmission may be common in media serving applications and the like.

[0038] In another example, the communication system (300) includes a second pair of terminal devices (330) and (340) that perform bidirectional transmission of coded video data, for example, during a video conference. In the case of bidirectional data transmission, in one example, each of the terminal devices (330) and (340) may 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) via the network (350). Each of the terminal devices (330) and (340) may also receive the coded video data transmitted by the other of the terminal devices (330) and (340), decode the coded video data to recover the video pictures, and display the video pictures on an accessible display device according to the recovered video data.

[0039] In the example of FIG. 3, the terminal devices (310), (320), (330), and (340) are illustrated as a server, a personal computer, and a smartphone, respectively, but the principles of the present disclosure may not be so limited. Embodiments of the present disclosure are applicable with laptop computers, tablet computers, media players, and / or dedicated video conferencing equipment. The network (350) represents any number of networks that transmit coded video data among 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 channels and / or packet-switched channels. Representative networks include telecommunications networks, local area networks, wide area networks, and / or the Internet. For the purposes of this description, the architecture and topology of the network (350) may not be important for the operation of the present disclosure, unless otherwise described herein below.

[0040] FIG. 4 shows a video encoder and a video decoder in a streaming environment as an example of the use of the disclosed subject matter. The disclosed subject matter may be equally applicable to other video-related applications, including, for example, video conferencing, digital television, streaming services, storage of compressed video on digital media, including CDs, DVDs, memory sticks, and the like.

[0041] A streaming system may include, for example, a video source (401) that creates a stream (402) of uncompressed video pictures, and a capture subsystem (413) that may include, for example, a digital camera. In one example, the stream (402) of video pictures includes samples taken by a digital camera. The stream (402) of video pictures, shown as a thick line to emphasize the larger amount of data when 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) connected 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 encoded video bitstream), depicted as a thin line to emphasize the smaller amount of data compared to the stream (402) of video pictures, 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, may access the streaming server (405) to retrieve copies (407) and (409) of the encoded video data (404). The client subsystem (406) may include, for example, a video decoder (410) within 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 may be rendered on a display (412) (e.g., a display screen) or other rendering device (not shown). In some streaming systems, the encoded video data (404), (407), and (409) (e.g., video bitstreams) may be encoded according to a particular video coding / compression standard. Examples of these standards include ITU-T Recommendation H.265. In one example, a video coding standard under development is informally known as Versatile Video Coding (VVC).The disclosed subject matter may be used in the context of VVC.

[0042] It should be noted that electronic devices (420) and (430) can include other components (not shown). For example, electronic device (420) can include a video decoder (not shown), and electronic device (430) can also include a video encoder (not shown).

[0043] FIG. 5 shows an exemplary block diagram of a video decoder (510). The video decoder (510) can be included in an electronic device (530). The electronic device (530) can include a receiver (531) (e.g., a receiving circuit). The video decoder (510) can be used in place of the video decoder (410) in the example of FIG. 4.

[0044] The receiver (531) may receive one or more coded video sequences to be decoded by the video decoder (510). In one embodiment, one coded video sequence is received at a time, and the decoding of each coded video sequence is independent of the decoding of other coded video sequences. The coded video sequence may be received from a channel (501), which may be a hardware / software link to a storage device storing the encoded video data. The receiver (531) may receive the encoded video data along with other data, such as a coded audio data stream and / or an auxiliary data stream, which may be transferred to respective usage entities (not shown). The receiver (531) may separate the coded video sequence from the other data. A buffer memory (515) may be connected between the receiver (531) and the entropy decoder / parser (520) (hereinafter, “parser (520)”) to counter network jitter. 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 shown). In still other applications, for example, to counter network jitter, there may be a buffer memory external to the video decoder (510), and in addition, for example, to handle playout timing, there may be another buffer memory (515) inside the video decoder (510). When the receiver (531) is receiving data from a storage / transfer device with sufficient bandwidth and controllability or from an isochronous network, the buffer memory (515) may be unnecessary or may be made small. For use in a best-effort packet network such as the Internet, the buffer memory (515) may be required, may be relatively large, and advantageously may be of an adaptable size and may be at least partially implemented in an operating system or similar element (not shown) external to the video decoder (510).

[0045] Video decoder (510) may include a parser (520) to reconstruct symbols (521) from the coded video sequence. The categories of these symbols include information used to manage the operation of the video decoder (510), and potentially, information for controlling a rendering device (such as a display screen) (512) which is not an essential part of the electronic device (530) but can be connected to the electronic device (530) as shown in FIG. 5. The control information for the (one or more) rendering devices may be in the form of a supplementary enhancement information (SEI) message or a video user capability information (VUI) parameter set fragment (not depicted). The parser (520) may perform syntax analysis / entropy decoding on the received coded video sequence. The coding of the coded video sequence can follow video coding techniques or standards and can follow various principles including variable length coding with or without context dependency, Huffman coding, arithmetic coding, etc. The parser (520) may extract a set of at least one subgroup parameter of a subgroup of pixels within the video decoder from the coded video sequence based on at least one parameter corresponding to a group. The subgroups can include picture groups (GOP), pictures, tiles, slices, macroblocks, coding units (CU), blocks, transform units (TU), prediction units (PU), etc. The parser (520) can also extract information such as transform coefficients, quantization parameter values, motion vectors, etc. from the coded video sequence.

[0046] The parser (520) may perform an entropy decoding / syntax analysis operation on the video sequence received from the buffer memory (515) to create symbols (521).

[0047] The reconstruction of symbol (521) can involve multiple different units depending on the type of the coded video picture or a portion thereof (such as inter-picture and intra-picture, inter-block and intra-block, etc.), as well as other factors. How each unit is involved can be controlled by subgroup control information parsed from the coded video sequence by parser (520). Such a flow of subgroup control information between parser (520) and the following multiple units is not depicted for clarity.

[0048] In addition to the function blocks already described, 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 interact closely with each other and can be at least partially integrated with each other. However, for the purpose of describing the disclosed subject matter, the following conceptual subdivision into functional units is appropriate.

[0049] The first unit is a scaler / inverse transform unit (551). The scaler / inverse transform unit (551) receives quantization transform coefficients, as well as control information including which transform to use, block size, quantization coefficients, quantization scaling matrix, etc., from parser (520) as (one or more) symbols (521). The scaler / inverse transform unit (551) can output a block including sample values that can be input to aggregator (555).

[0050] In some cases, the output samples of the scaler / inverse transform unit (551) may be related to intra-coded blocks. An intra-coded block is a block that does not use prediction information from a previously reconstructed picture and can use prediction information from a previously reconstructed portion of the current picture. Such prediction information may be provided by the intra-picture prediction unit (552). In some cases, the intra-picture prediction unit (552) uses the surrounding already reconstructed information fetched from the current picture buffer (558) to generate a block of the same size and shape as the block being reconstructed. The current picture buffer (558) buffers, for example, a partially reconstructed current picture and / or a fully reconstructed current picture. The aggregator (555) may, in some cases, add, sample by sample, the prediction information generated by the intra prediction unit (552) to the output sample information provided by the scaler / inverse transform unit (551).

[0051] In other cases, the output samples of the scaler / inverse transform unit (551) may relate to inter-coded and potentially motion-compensated blocks. In such cases, the motion compensation prediction unit (553) can access the reference picture memory (557) to fetch the samples used for prediction. After motion-compensating the samples fetched according to the symbols (521) related to the block, these samples can be added to the output of the scaler / inverse transform unit (551) by the aggregator (555) to generate output sample information (in this case, called residual samples or residual signals). The address in the reference picture memory (557) from which the motion compensation prediction unit (553) fetches the prediction samples can be controlled, for example, by the motion vectors available to the motion compensation prediction unit (553) in the form of symbols (521) that can have X, Y, and reference picture components. Motion compensation can also include interpolation of the sample values fetched from the reference picture memory (557) when exact sub-sample motion vectors are used, a motion vector prediction mechanism, etc.

[0052] The output samples of the aggregator (555) can undergo various loop filtering techniques in the loop filter unit (556). The video compression technology is controlled by the parameters included in the coded video sequence (also called the coded video bitstream) and can include in-loop filter techniques provided to the loop filter unit (556) as symbols (521) from the parser (520). Video compression can also be performed in response to meta-information obtained during the decoding of the previous part (in decoding order) of the coded picture or coded video sequence, and can also be performed in response to previously reconstructed and loop-filtered sample values.

[0053] The output of the loop filter unit (556) can be a sample stream that is not only output to the rendering device (512) but also stored in the reference picture memory (557) for use in future inter-picture prediction.

[0054] Once a particular coded picture is fully reconstructed, it can be used as a reference picture for future prediction. For example, when the coding picture corresponding to the current picture is fully reconstructed and the coding 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 starting the reconstruction of the next coded picture.

[0055] The video decoder (510) can perform a decoding operation according to a predetermined video compression technology or standard such as ITU-T Rec. H.265. The coded video sequence can conform to the syntax specified by the video compression technology or standard being used, in the sense that the coded video sequence complies with both the syntax of the video compression technology or standard and the profile documented in the video compression technology or standard. Specifically, the profile may select specific tools from all the tools available in the video compression technology or video compression standard as the only tools available under that profile. Also, for compliance, it may be necessary that the complexity of the coded video sequence is within the range defined by the level of the video compression technology or standard. In some cases, the level limits, for example, the maximum picture size, the maximum frame rate, the maximum reconstruction sample rate (measured in megasamples per second), the maximum reference picture size, etc. The limitations set by the level can, in some cases, be further restricted by the specifications of the hypothetical reference decoder (HRD) and the metadata for HRD buffer management signaled within the coded video sequence.

[0056] In one embodiment, the receiver (531) can receive additional (redundant) data along with the encoded video. The additional data can be included as part of the (one or more) coded video sequences. The additional data can 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 can 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, and the like.

[0057] FIG. 6 shows an exemplary block diagram of a video encoder (603). 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.

[0058] The video encoder (603) can receive video samples from a video source (601) that can capture video images to be coded by the video encoder (603) (not part of the electronic device (620) in the example of FIG. 6). In another example, the video source (601) is part of the electronic device (620).

[0059] The video source (601) can provide the source video sequence to be coded by the video encoder (603) in the form of a digital video sample stream that can be of any suitable bit depth (e.g., 8 bits, 10 bits, 12 bits, …), 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 pre-prepared video. In a video conferencing system, the video source (601) can be a camera that captures local image information as a video sequence. The video data may be provided as a plurality of individual pictures that convey motion when viewed in order. Each picture itself can be organized as a spatial array of pixels, and each pixel can include 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.

[0060] According to one embodiment, the video encoder (603) can code and compress the pictures of the source video sequence into a coded video sequence (643) in real time or under any other required time constraints. Enforcing an appropriate coding speed is one function of the controller (650). In some embodiments, the controller (650) controls and is functionally connected to other functional units described below. For clarity, the connections are not depicted. The parameters set by the controller (650) can include rate control related parameters (picture skip, quantizer, lambda value of rate distortion optimization techniques, …), picture size, picture group (GOP) layout, maximum motion vector search range, etc. The controller (650) can be configured to have other appropriate functions related to the video encoder (603) optimized for a particular system design.

[0061] In some embodiments, the video encoder (603) is configured to operate in a coding loop. As an overly simplified explanation, in one example, the coding loop can include a source coder (630) (which, for example, is responsible for creating symbols such as a symbol stream based on an input picture to be coded and one or more reference pictures), and a (local) decoder (633) incorporated in the video encoder (603). The decoder (633) reconstructs symbols in a manner similar to that which would also be done by a (remote) decoder to create sample data. The reconstructed sample stream (sample data) is input into the reference picture memory (634). Since the decoding of the symbol stream results in a bit-exact result regardless of the location of the decoder (local or remote), the content of the reference picture memory (634) is also bit-exact between the local encoder and the remote encoder. In other words, the prediction part of the encoder "sees" the same sample values as the reference picture samples that the decoder would "see" when using prediction during decoding. This basic principle of reference picture synchronization (and the resulting drift if synchronization cannot be maintained, for example, due to channel errors) is also used in some related technologies.

[0062] The operation of the "local" decoder (633) can be the same as that of a "remote" decoder such as the video decoder (510), which has already been described in detail above in conjunction with FIG. 5. However, referring briefly to FIG. 5 as well, since symbols are available and the encoding / decoding of symbols into the coded video sequence by the entropy encoder (645) and the parser (520) can be reversible, the entropy decoding part of the video decoder (510) including the buffer memory (515), and the parser (520) may not be fully implemented in the local decoder (633).

[0063] In one embodiment, decoder techniques other than syntax analysis / entropy decoding present in the decoder exist in the corresponding encoder in the same or substantially the same functional form. Accordingly, the disclosed subject matter focuses on the operation of the decoder. Since the description of encoder techniques is the reverse of the decoder techniques described comprehensively, it can be omitted. In certain areas, more detailed descriptions are provided below.

[0064] During operation, in some examples, the source coder (630) can perform motion-compensated predictive coding that predictively codes an input picture by referring to one or more previously coded pictures from a video sequence designated as a "reference picture". In this way, the coding engine (632) codes the difference between a pixel block of the input picture and a pixel block of the (one or more) reference pictures that can be selected as the (one or more) prediction references to the input picture.

[0065] The local video decoder (633) can decode the coded video data of a picture that can be designated as a reference picture based on the symbols created by the source coder (630). The operation of the coding engine (632) may advantageously be an irreversible process. When the coded video data can be decoded by a video decoder (not shown in FIG. 6), the reconstructed video sequence can typically be a replica of the source video sequence with some errors. The local video decoder (633) can replicate the decoding process that can be performed by the video decoder for the reference picture and store the reconstructed reference picture in the reference picture memory (634). In this way, the video encoder (603) can locally store a copy of the reconstructed reference picture having common content as the reconstructed reference picture that would be obtained by a remote video decoder (without transmission errors).

[0066] The predictor (635) can perform a predictive search for the coding engine (632). That is, in the case of a new picture to be coded, the predictor (635) can search the reference picture memory (634) for sample data (as a candidate reference pixel block) or specific metadata such as reference picture motion vectors and block shapes that can serve as an appropriate prediction reference for the new pixels. The predictor (635) can operate on the sample blocks for each pixel block to find an appropriate prediction reference. In some cases, the input picture may have prediction references drawn from a plurality of reference pictures stored in the reference picture memory (634) as determined by the search results obtained by the predictor (635).

[0067] The controller (650) can manage the coding operations of the source coder (630), including for example, setting the parameters and subgroup parameters used to encode video data.

[0068] The outputs of all the aforementioned functional units can undergo entropy coding in the entropy coder (645). The entropy coder (645) converts the symbols generated by the various functional units into a coded video sequence by applying reversible compression to the symbols according to techniques such as Huffman coding, variable-length coding, arithmetic coding, etc.

[0069] The transmitter (640) can buffer for transmission via the communication channel (660), which can be a hardware / software link to a storage device that will store the encoded video data, the (one or more) coded video sequences created by the entropy coder (645). The transmitter (640) can merge the coded video data from the video encoder (603) with other data to be transmitted, such as coded audio data and / or an auxiliary data stream (source not shown).

[0070] The controller (650) may manage the operation of the video encoder (603). During coding, the controller (650) can assign a specific coded picture type to each coded picture, which may affect the coding techniques applicable to each picture. For example, a picture can often be assigned as one of the following picture types.

[0071] An intra picture (I picture) can be coded and decoded without using other pictures in the sequence as a prediction source. 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, as well as their respective uses and characteristics.

[0072] A predicted picture (P picture) can be coded and decoded using intra prediction or inter prediction that uses at most one motion vector and a reference index to predict the sample values of each block.

[0073] A bi-directionally predicted picture (B picture) can be coded and decoded using intra prediction or inter prediction that uses at most two motion vectors and reference indices to predict the sample values of each block. Similarly, multiple predicted pictures can use three or more reference pictures and associated metadata for the reconstruction of a single block.

[0074] The source picture can generally be spatially subdivided into a plurality of sample blocks (e.g., blocks of 4×4, 8×8, 4×8, or 16×16 samples respectively) and coded block by block. The blocks can be coded predictively by referring to other (already coded) blocks determined by the coding assignment applied to each picture of the block. For example, the blocks of an I picture can be coded non-predictively or predictively by referring to already coded blocks of the same picture (spatial prediction or intra prediction). The pixel blocks of a P picture can be coded predictively via spatial prediction or via temporal prediction by referring to one previously coded reference picture. The blocks of a B picture can be coded predictively via spatial prediction or via temporal prediction by referring to one or two previously coded reference pictures.

[0075] The video encoder (603) can perform coding operations according to a predetermined video coding technology or standard such as ITU-T Recommendation H.265. In that operation, the video encoder (603) can perform various compression operations including predictive coding operations that utilize the temporal and spatial redundancies in the input video sequence. Thus, the coded video data can conform to the syntax specified by the video coding technology or standard being used.

[0076] 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 extension layers, other forms of redundant data such as redundant pictures and slices, SEI messages, VUI parameter set fragments, and the like.

[0077] Videos can be captured in time series as a plurality of source pictures (video pictures). Intra-picture prediction (often abbreviated as intra prediction) utilizes the spatial correlation within a given picture, while inter-picture prediction utilizes the (temporal or other) correlation between pictures. In one example, a particular picture being encoded / decoded, called the current picture, is divided into blocks. When a block within the current picture is similar to a reference block within a reference picture that has been previously coded and is still buffered within the video, the block within the current picture can be coded by a vector called a motion vector. The motion vector points to the reference block within the reference picture and can have a third dimension that identifies the reference picture when multiple reference pictures are being used.

[0078] In some embodiments, dual prediction techniques can be used for inter-picture prediction. According to the dual prediction technique, two reference pictures, such as a first reference picture and a second reference picture, are used, both of which are prior to the current picture within the video in decoding order (however, the display order may be past and future respectively). A block within the current picture can be coded by a first motion vector that points to a first reference block within the first reference picture and a second motion vector that points to a second reference block within the second reference picture. The block can be predicted by a combination of the first reference block and the second reference block.

[0079] Furthermore, to improve coding efficiency, merge mode techniques can be used in inter-picture prediction.

[0080] According to some embodiments of the present disclosure, predictions such as inter-picture prediction and intra-picture prediction are performed in units of blocks. For example, according to the HEVC standard, pictures in a sequence of video pictures are divided into coding tree units (CTUs) for compression, and CTUs within a picture have the same size such as 64×64 pixels, 32×32 pixels, 16×16 pixels, etc. Generally, a CTU includes three coding tree blocks (CTBs), which are one luma CTB and two chroma CTBs. Each CTU can be recursively quad-tree divided into one or more coding units (CUs). For example, a 64×64 pixel CTU can be divided into one 64×64 pixel CU, or four 32×32 pixel CUs, or sixteen 16×16 pixel CUs. In one example, each CU is analyzed to determine the prediction type of the CU, such as an inter-prediction type or an intra-prediction type. The CU is divided into one or more prediction units (PUs) according to temporal predictability and / or spatial predictability. Generally, each PU includes one luma prediction block (PB) and two chroma PBs. In one embodiment, the prediction operation in coding (encoding / decoding) is performed in units of prediction blocks. 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) such as 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, etc.

[0081] FIG. 7 shows an exemplary diagram of a video encoder (703). The video encoder (703) receives a processing block (e.g., a prediction block) of sample values within a current video picture in a sequence of video pictures and is configured to encode the processing block into a coded picture that is part of a coded video sequence. In one example, the video encoder (703) is used instead of the video encoder (403) of the example of FIG. 4.

[0082] In an example of HEVC, a video encoder (703) receives a matrix of sample values for a processing block, such as an 8×8 sample prediction block. The video encoder (703) determines whether the processing block is best coded using an intra mode, an inter mode, or a bi-prediction mode, for example, using rate-distortion optimization. If the processing block is to be coded in the intra mode, the video encoder (703) uses intra prediction techniques to encode the processing block into the coded picture. If the processing block is to be coded in the inter mode or the bi-prediction mode, the video encoder (703) may use inter prediction techniques or bi-prediction techniques, respectively, to encode the processing block into the coded picture. In certain video coding techniques, the merge mode may be an inter-picture prediction sub-mode in which the motion vector is derived from one or more motion vector predictors without the aid of coded motion vector components outside the predictor. In certain other video coding techniques, there may be motion vector components applicable to the target block. In one example, the video encoder (703) includes other components, such as a mode decision module (not shown), to determine the mode of the processing block.

[0083] 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-purpose controller (721), and an entropy encoder (725) connected to each other as shown in FIG. 7.

[0084] The inter encoder (730) is configured to receive samples of a current block (e.g., a processing block), compare the block with one or more reference blocks (e.g., blocks in a previous picture and a subsequent picture) in a reference picture, generate inter prediction information (e.g., description of redundant information by an inter coding technique, motion vectors, merge mode information), and calculate an inter prediction result (e.g., a predicted block) based on the inter prediction information using any suitable technique. In some examples, the reference picture is a decoded reference picture decoded based on coded video information.

[0085] The intra encoder (722) is configured to receive samples of a current block (e.g., a processing block), optionally compare the block with already coded blocks in the same picture, generate quantized coefficients after transformation, and optionally also generate intra prediction information (e.g., intra prediction direction information by one or more intra coding techniques). In one example, the intra encoder (722) also calculates an intra prediction result (e.g., a predicted block) based on the intra prediction information and reference blocks in the same picture.

[0086] The general-purpose controller (721) is configured to determine general-purpose control data and control other components of the video encoder (703) based on the general-purpose control data. In one example, the general-purpose controller (721) determines the mode of a block and provides a control signal to the switch (726) based on the mode. For example, when the mode is the intra mode, the general-purpose controller (721) controls the switch (726) to select the intra mode result for use by the residual calculator (723), controls the entropy encoder (725) to select the intra prediction information, includes the intra prediction information in the bitstream, and when the mode is the inter mode, the general-purpose controller (721) controls the switch (726) to select the inter prediction result for use by the residual calculator (723), controls the entropy encoder (725) to select the inter prediction information, and includes the inter prediction information in the bitstream.

[0087] The residual calculator (723) is configured to calculate the difference (residual data) between the received block and the prediction result selected from the intra encoder (722) or the inter encoder (730). The residual encoder (724) is configured to operate to generate a conversion coefficient by encoding the residual data based on the residual data. In one example, the residual encoder (724) is configured to convert the residual data from the spatial domain to the frequency domain and generate a conversion coefficient. The conversion coefficient then undergoes quantization processing to obtain a quantized conversion coefficient. In various embodiments, the video encoder (703) also includes a residual decoder (728). The residual decoder (728) is configured to perform inverse conversion and generate decoded residual data. The decoded residual data can be appropriately used by the intra encoder (722) and the inter encoder (730). 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 block is appropriately processed to generate a decoded picture, and the decoded picture is buffered in a memory circuit (not shown) and can be used as a reference picture in some examples.

[0088] The entropy encoder (725) is configured to format the bitstream to include the encoded block. The entropy encoder (725) is configured to include various information in the bitstream according to an appropriate standard such as the HEVC standard. In one example, the entropy encoder (725) is configured to include general control data, selected prediction information (e.g., intra prediction information or inter prediction information), residual information, and other appropriate information in the bitstream. Note that according to the disclosed subject matter, there is no residual information when coding a block in either the merge submode of the inter mode or the bi-prediction mode.

[0089] FIG. 8 shows an exemplary diagram of a video decoder (810). The video decoder (810) is configured to receive a coded picture that is part of a coded video sequence and decode the coded picture to generate a reconstructed picture. In one example, the video decoder (810) is used in place of the video decoder (410) of the example of FIG. 4.

[0090] 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) connected together as shown in FIG. 8.

[0091] The entropy decoder (871) may be configured to reconstruct from the coded picture certain symbols that represent syntax elements from which the coded picture is composed. Such symbols can include, for example, the mode in which a block is coded (e.g., intra mode, inter mode, bi-prediction mode, merge sub-mode or other sub-modes of inter mode and bi-prediction mode, etc.), and prediction information (e.g., intra prediction information or inter prediction information, etc.) that can identify specific samples or metadata used for prediction by the intra-decoder (872) or the inter-decoder (880), respectively. The symbols can also include, for example, residual information in the form of quantized transform coefficients. In one example, when the prediction mode is inter mode or bi-prediction mode, inter prediction information is provided to the inter-decoder (880), and when the prediction type is intra prediction type, 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).

[0092] The inter-decoder (880) is configured to receive inter prediction information and generate an inter prediction result based on the inter prediction information.

[0093] The intra decoder (872) is configured to receive intra prediction information and generate a prediction result based on the intra prediction information.

[0094] The residual decoder (873) is configured to perform inverse quantization to extract inverse quantization transform coefficients, process the inverse quantization transform coefficients, and convert the residual information from the frequency domain to the spatial domain. The residual decoder (873) may also require certain control information (to include quantization parameter (QP)), and that information may be provided by the entropy decoder (871) (since this may be only a small amount of control information, the data path is not depicted).

[0095] The reconstruction module (874) is configured to combine, in the spatial domain, the residual information output by the residual decoder (873) and the prediction result (optionally output by the inter prediction module or the intra prediction module) to form a reconstruction block that can be part of a reconstructed picture, and the reconstructed picture can be part of a reconstructed video. Note that other appropriate operations, such as a deblocking operation, can be performed to improve visual quality.

[0096] Note that the video encoders (403), (603), and (703), and the video decoders (410), (510), and (810) can be implemented using any suitable technology. In one embodiment, the video encoders (403), (603), and (703), and the video decoders (410), (510), and (810) can 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) can be implemented using one or more processors that execute software instructions.

[0097] In VVC, various inter-prediction modes can be used. For an inter-predicted CU, the motion parameters can include one or more MVs, one or more reference picture indices, a reference picture list use index, and additional information about specific coding features to be used for generating the inter-predicted samples. The motion parameters can be signaled either explicitly or implicitly. When a CU is coded in skip mode, the CU can be associated with a PU and cannot have significant residual coefficients, coded motion vector deltas, MV differences (e.g., MVD), or reference picture indices. If the motion parameters of the current CU are obtained from one or more neighboring CUs that include spatial candidates and / or temporal candidates, and optionally additional information such as that introduced in VVC, the merge mode can be specified. The merge mode can be applied not only to skip mode but also to inter-predicted CUs. In one example, an alternative to the merge mode is the explicit transmission of motion parameters, in which case one or more MVs, the corresponding reference picture indices for each reference picture list, and reference picture list use flags and other information are signaled explicitly for each CU.

[0098] In one embodiment such as VVC, the VVC Test Model (VTM) reference software includes one or more improved inter-prediction coding tools including extended merge prediction, merge motion vector difference (MMVD) mode, adaptive motion vector prediction (AMVP) mode using symmetric MVD signaling, affine motion compensation prediction, sub-block based temporal motion vector prediction (SbTMVP), adaptive motion vector resolution (AMVR), motion field storage (1 / 16 luma sample MV storage and 8×8 motion field compression), bi-prediction using CU level weighting (BCW), bi-directional optical flow (BDOF), prediction refinement using optical flow (PROF), decoder side motion vector refinement (DMVR), combined inter and intra prediction (CIIP), geometric partitioning mode (GPM), etc. Inter-prediction and related methods are described in detail below.

[0099] In some examples, enhanced merge prediction may be used. In one example such as VTM4, the merge candidate list is constructed by sequentially including the following five types of candidates: (one or more) spatial motion vector predictors (MVPs) from (one or more) spatially adjacent CUs, (one or more) temporal MVPs from (one or more) aligned CUs, (one or more) history-based MVPs from a first-in first-out (FIFO) table, (one or more) average MVPs of (one or more) pairs, and (one or more) zero MV.

[0100] The size of the merge candidate list may be signaled in the slice header. In one example, the maximum allowable size of the merge candidate list is 6 in VTM4. For each CU coded in merge mode, the index of the best merge candidate (e.g., the merge index) may be coded using truncated unary binary coding (TU). The first bin of the merge index can be coded in context (e.g., context adaptive binary arithmetic coding (CABAC)), and bypass coding can be used for the other bins.

[0101] Some examples of the process for generating merge candidates of different categories are provided below. In one embodiment, the (one or more) spatial candidates are derived as follows. The derivation of spatial merge candidates in VVC or the like can be the same as that in HEVC. In one example, up to four merge candidates are selected from among the candidates placed at the positions shown in FIG. 9. FIG. 9 shows the positions of spatial merge candidates according to an embodiment of the present disclosure. Referring to FIG. 9, the order of derivation is B1, A1, B0, A0, and B2. The position B2 is considered only when none of the CUs at the positions A0, B0, B1, and A1 are available (for example, because the CU belongs to another slice or another tile), or when it is intra-coded. After the candidate at position A1 is added, the addition of the remaining candidates is subject to a redundancy check that ensures that candidates having the same motion information are excluded from the candidates so as to improve coding efficiency.

[0102] To reduce the computational complexity, in some embodiments, not all possible candidate pairs are considered in the redundancy check where all possible candidate pairs are mentioned. Instead, only specific pairs such as the pairs connected using the arrows in FIG. 10 are considered, and a candidate is added to the candidate list only if the corresponding candidates used in the redundancy check do not have the same motion information. FIG. 10 shows the candidate pairs considered for the redundancy check of spatial merge candidates according to an embodiment of the present disclosure. Referring to FIG. 10, the pairs connected by each arrow include A1 and B1, A1 and A0, A1 and B2, B1 and B0, and B1 and B2. Therefore, the candidates at positions B1, A0, and / or B2 can be compared with the candidates at position A1, and the candidates at positions B0 and / or B2 can be compared with the candidates at position B1.

[0103] In one embodiment, the (one or more) temporal candidates are derived as follows. In one example, only one temporal merge candidate is added to the candidate list. FIG. 11 shows an exemplary motion vector scaling of a temporal merge candidate. To derive the temporal merge candidate of the current CU (1111) in the current picture (1101), the scaled MV (1121) (e.g., indicated by the dotted line in FIG. 11) can be derived based on the collocated CU (1112) belonging to the arranged reference pictures (1104). The reference picture list used to derive the collocated CU (1112) can be explicitly signaled in the slice header. The scaled MV (1121) for the temporal merge candidate can be obtained as shown by the dotted line in FIG. 11. The scaled MV (1121) can be scaled from the MV of the collocated CU (1112) using the picture order count (POC) distances tb and td. The POC distance tb can be defined as the POC difference between the current reference picture (1102) of the current picture (1101) and the current picture (1101). The POC distance td can be defined as the POC difference between the collocated reference picture (1104) of the collocated picture (1103) and the collocated picture (1103). The reference picture index of the temporal merge candidate can be set to zero.

[0104] FIG. 12 shows exemplary candidate positions (e.g., C0 and C1) of the temporal merge candidate of the current CU. The position of the temporal merge candidate can be selected between the candidate positions C0 and C1. The candidate position C0 is located at the lower right corner of the collocated CU (1210) of the current CU. The candidate position C1 is located at the center of the collocated CU (1210) of the current CU (1210). If the CU at the candidate position C0 is not available, is intra-coded, or is outside the current row of the CTU, the candidate position C1 is used to derive the temporal merge candidate. Otherwise, for example, if the CU at the candidate position C0 is available, is intra-coded, is in the current row of the CTU, the candidate position C0 is used to derive the temporal merge candidate.

[0105] In some examples, the translational motion model is applied to motion compensation prediction (MCP). However, the translational motion model may not be suitable for modeling zoom in / out, rotation, perspective motion, and other irregular motions. In some embodiments, block-based affine transform motion compensation prediction is applied. In FIG. 13A, the affine motion field of a block is described by two control point motion vectors (CPMVs), CPMV0 and CPMV1, of two control points (CPs), CP0 and CP1, when a four-parameter affine model is used. In FIG. 13B, the affine motion field of a block is described by three CPMVs, CPMV0, CPMV1, and CPMV3, of CPs, CP0, CP1, and CP2, when a six-parameter affine model is used.

[0106] In a four-parameter affine motion model, the motion vector at a sample position (x, y) within a block is derived as follows.

Equation

[0107] In a six-parameter affine motion model, the motion vector at a sample position (x, y) within a block is derived as follows.

Equation

[0108] In Equations 1-2, (mv 0x , mv 0y ) is the motion vector of the upper left corner control point, (mv 1x , mv 1y ) is the motion vector of the lower left corner control point, and (mv 2x , mv 2y ) is the motion vector of the lower left corner control point. In addition, the coordinates (x, y) are relative to the upper left corner of each block, and W and H indicate the width and height of each block, respectively.

[0109] To simplify motion compensation prediction, in some embodiments, sub-block-based affine transform prediction is applied. For example, in FIG. 14, a four-parameter affine motion model is used, and two CPMVs [Number] are determined. To derive a motion vector for each 4×4 (sample) luma sub-block (1402) divided from the current block (1410), the motion vector (1401) of the central sample of the sub-block (1402) is calculated according to Equation 1 and rounded to 1 / 16 fractional precision. Then, a motion compensation interpolation filter is applied to generate a prediction for each sub-block (1402) using the derived motion vector (1401). The sub-block size of the chroma component is set to be 4×4. The MV of a 4×4 chroma sub-block is calculated as the average of the MVs of four corresponding 4×4 luma sub-blocks.

[0110] Similar to translational motion inter-prediction, in some embodiments, two affine motion inter-prediction modes, the affine merge mode and the affine AMVP mode, are adopted.

[0111] In some embodiments, for a CU whose both width and height are 8 or more, the affine merge mode may be applied. The affine merge candidates of the current CU may be generated based on the motion information of spatially adjacent CUs. There may be up to five affine merge candidates, and an index is signaled to indicate which one is used for the current CU. For example, to form an affine merge candidate list, the following three types of affine merge candidates are used. (i) Inherited affine merge candidates extrapolated from the CPMVs of adjacent CUs; (ii) Constructed affine merge candidates derived using the translational MVs of adjacent CUs; and (iii) Zero MV.

[0112] In some embodiments, there may be up to two inherited affine candidates derived from the affine motion models of adjacent blocks, one derived from the left adjacent CU and the other from the upper adjacent CU. The candidate blocks can be arranged, for example, at the positions shown in FIG. 9. For the left predictor, the scanning order is A0 > A1, and for the upper predictor, the scanning order is B0 > B1 > B2. Only the first inheritance candidate from each side is selected. No pruning check is performed between the two inheritance candidates.

[0113] When an adjacent affine CU is identified, the CPMV of the identified adjacent affine CU is used to derive the CPMV within the affine merge list of the current CU. As shown in FIG. 15, the adjacent lower left block A of the current CU (1510) is coded in the affine mode. The motion vectors at the upper left corner, upper right corner, and lower left corner of the CU (1520) containing block A

Number

Number

Number

Number

[0114] By combining the translational motion information adjacent to each control point, a construction affine candidate is constructed. The motion information of the control points is derived from the specified spatial neighborhood and temporal neighborhood shown in FIG. 16. CPMVk (k = 1, 2, 3, 4) represents the k-th control point. In CPMV1, the B2 > B3 > A2 blocks are checked in order, and the MV of the first available block is used. In CPMV2, the B1 > B0 blocks are checked, and in CPMV3, the A1 > A0 blocks are checked. The TMVP in block T is used as CPMV4 if available.

[0115] After the MVs of the four control points are achieved, an affine merge candidate is constructed based on the motion information. To construct it, the following combinations of control point MVs are used in order: {CPMV1, CPMV2, CPMV3}, {CPMV1, CPMV2, CPMV4}, {CPMV1, CPMV3, CPMV4}, {CPMV2, CPMV3, CPMV4}, {CPMV1, CPMV2}, {CPMV1, CPMV3}.

[0116] The combination of three CPMVs constructs a 6-parameter affine merge candidate, and the combination of two CPMVs constructs a 4-parameter affine merge candidate. To avoid motion scaling processing, when the reference indices of the control points are different, the related combinations of control point MVs are discarded.

[0117] After the inherited affine merge candidate and the constructed affine merge candidate are checked, if the list is not yet full, a zero MV is inserted at the end of the merge candidate list.

[0118] In some embodiments, for CUs where both the width and height are 16 or greater, the affine AMVP mode may be applied. To indicate whether the affine AMVP mode is used, a CU-level affine flag is signaled in the bitstream, and another flag is signaled to indicate whether 4-parameter affine or 6-parameter affine is used. The difference between the CPMV of the current CU and its predictors is signaled in the bitstream. The affine AVMP candidate list size is 2, and can be generated by using the following four types of CPVM candidates in order. (i) Inherited affine AMVP candidates extrapolated from the CPMV of adjacent CUs; (ii) Constructed affine AMVP candidates derived using the translational MVs of adjacent CUs; (iii) Translational MVs from adjacent CUs; and (iv) zero MVs.

[0119] The check order of the inherited affine AMVP candidates is the same as the check order of the inherited affine merge candidates in one example. The difference is that for AVMP candidates, affine CUs having the same reference picture as the current block are considered. The pruning process is not applied when inserting the inherited affine motion predictor into the candidate list.

[0120] The constructed AMVP candidates are derived from the vicinity of the designated space shown in FIG. 16. The same checking order as that performed in affine merge candidate construction is used. Additionally, the reference picture indexes of adjacent blocks are also checked. The first block in the checking order that is inter-coded and has the same reference picture as the current CU is used. When the current CU is coded with a 4-parameter affine model and both CPMV0 and CPMV1 are available, the available CPMV is added as one candidate in the affine AMVP list. When the current CU is coded with a 6-parameter affine mode and all three CPMVs (CPMV0, CPMV1, and CPMV2) are available, the available CPMV is added as one candidate in the affine AMVP list. Otherwise, the constructed AMVP candidates are set as unavailable.

[0121] The affine AMVP list candidates are still less than 2 after the inherited affine AMVP candidates and the constructed AMVP candidates are checked, and the translational motion vectors adjacent to the control points are added to predict all the control point MVs of the current CU if available. Finally, if the affine AMVP list is not yet full, zero MVs are used to fill the affine AMVP list.

[0122] In one embodiment, an affine merge with motion vector difference (affine MMVD) mode can be used. The available affine merge candidates can be selected from the sub-block based merge list as base predictors. A motion vector offset can be applied to the motion vector value of each control point from the base predictor. If no affine merge candidates are available, the affine MMVD is not used. If the affine MMVD is used, the distance index and the offset direction index can be signaled later.

[0123] A distance index (IDX) can be signaled to indicate which distance offset to use from an offset table such as that shown in Table 1.

[0124] [Table 1]

[0125] The distance index represents four directions, as shown in Table 2, and only the x or y direction, not both directions, can have an MV difference.

[0126] [Table 2]

[0127] When the inter prediction is a single prediction, the signaled distance offset can be applied to the offset direction for each control point predictor. The result can be the MV value of each control point.

[0128] When the inter prediction is a dual prediction, the signaled distance offset can be applied to the signaled offset direction for the L0 motion vector of the control point predictor, and the offset applied to the L1 MV can be applied based on mirroring or scaling as specified below.

[0129] When the inter prediction is a dual prediction, the signaled distance offset is applied to the signaled offset direction for the L0 motion vector of the control point predictor. For the L1 CPMV, the offset can be applied based on mirroring where the same amount of distance offset in the opposite direction is applied.

[0130] In one embodiment, a POC distance-based offset mirroring method can be used for dual prediction. When a base candidate is dual predicted, the offset applied to L0 is signaled, and the offset on L1 can depend on the temporal positions of the reference pictures on list 0 and list 1. If both reference pictures are on the same temporal side of the current picture, the same distance offset and the same offset direction can be applied to the CPMV of L0 and L1. When the two reference pictures are on different sides of the current picture, the CPMV of L1 can have a distance offset applied in the opposite offset direction.

[0131] In one embodiment, a POC distance-based offset scaling method is used for dual prediction. When a base candidate is dual predicted, the offset applied to L0 is as signaled, and the offset applied to L1 can be scaled based on the temporal distances of the reference pictures on list 0 and list 1.

[0132] In one embodiment, the distance offset value range is extended to three offset tables, such as three different entries shown in Table 3. Each offset table (e.g., each row of Table 3) is adaptively selected based on the picture resolution. In one example, the offset table is selected based on the picture resolution. Referring to FIG. 3, the first offset table (e.g., "distance offset 1") is selected when the picture height is 1080 or more. The second offset table (e.g., "distance offset 2") is selected when the picture height is less than 1080 and 720 or more. The third offset table (e.g., "distance offset 3") is selected when the picture height is less than 720.

[0133] [Table 3]

[0134] Local illumination compensation (LIC) is a prediction technique such as an inter-prediction technique for modeling local illumination variations between a current block and a predictor of the current block (also called a predictor block) using a linear function. LIC can be applied to the single prediction mode but is not limited to the single prediction mode. The predictor can be determined based on a reference block of the current block. The reference block is within the reference picture. In one example such as the single prediction mode, the MV of the current block points to the reference block from the current block, and the predictor is the reference block of the current block. In one example, the value p of a sample (e.g., a reference sample) within the predictor (e.g., the reference block) i [x,y] is the updated value p of the sample within the updated predictor as shown in Equation 3 f is modified using a function for determining [x,y]. p f [x,y]=α×p i [x,y]+β Equation 3

[0135] The parameters of the linear function can be represented by a scaling coefficient (also called a scale) α and an offset β for compensating for illumination changes. p i [x,y] may be a reference sample at the position [x,y] on the reference picture, and the reference sample can be indicated by the MV of the current block. The scaling coefficient α and the offset β can be derived based on the current template of the current block (also called the current block template) and the reference template of the reference block (also called the reference block template) using any suitable method such as the least squares method. In various embodiments, the scaling coefficient α and the offset β are not signaled, and no signaling overhead is required for the scaling coefficient α and the offset β. In one example, an LIC flag is signaled to indicate the use of LIC. LIC can be used in any suitable standard such as within and beyond VVC

[0136] The current block can be coded based on an updated predictor in merge mode, skip mode, etc. The current block can be coded based on an updated predictor and additional information such as residual data in AMVP mode.

[0137] In related art, the LIC only uses a flag (e.g., LIC flag) to indicate whether the LIC is enabled, and does not have parameter adjustment to improve the accuracy of illuminance compensation when the LIC is enabled.

[0138] According to one aspect of the present disclosure, one or more parameters of a parameter set of the LIC (e.g., including a scaling factor α and an offset β) can be adjusted. The one or more parameters can be adjusted using a single index or a plurality of indexes. In one example, the scaling factor α and / or the offset β are adjusted using one or more indexes.

[0139] FIG. 17 shows an exemplary LIC with parameter adjustment. A current block (1701) in a current picture has a current template (also referred to as an adjacent reconstruction template) (1721). The current template (1721) can have any suitable shape and any suitable size. The current template (1721) can include samples (e.g., reconstructed samples) of the (one or more) adjacent reconstruction blocks of the current block (1701).

[0140] In the example shown in FIG. 17, the current template (1721) of the current block (1701) includes an upper template (1722) and a left template (1723). Each of the upper template (1722) and the left template (1723) can have any suitable shape and any suitable size. The upper template (1722) can include samples within one or more upper adjacent blocks of the current block (1701). In one example, the upper template (1722) includes four rows of samples within one or more upper adjacent blocks of the current block (1701). The left template (1723) can include samples within one or more left adjacent blocks of the current block (1701). In one example, the left template (1723) includes four columns of samples within one or more left adjacent blocks of the current block (1701).

[0141] In one example, the current template of the current block (1701) includes only the upper template (1722) or only the left template (1723). In one example, the current template of the current block (1701) includes the upper template (1722), the left template (1723), and an upper left template (1731).

[0142] The MV (1702) of the current block (1701) can point to a reference block (1703) in the reference picture. The reference block (1703) can have a reference template such as a reference template (1725) corresponding to the current template (1721).

[0143] The reference template (1725) can have the same shape and the same size as the shape and size of the current template respectively. In the example of FIG. 17, the reference template (1725) of the reference block (1703) includes an upper template (1726) and a left template (1727). The upper template (1726) corresponding to the upper template (1722) can include samples in one or more upper adjacent blocks of the reference block (1703). The left template (1727) corresponding to the left template (1723) can include samples in one or more left adjacent blocks of the reference block (1703).

[0144] The predictor of the current block (1701) can be determined based on the reference block (1703). In an example such as the single prediction mode, the predictor is the reference block (1703). For example, the sample value of the predictor is equal to the respective sample value of the reference block (1703).

[0145] The sample value of the predictor of the current block (1701) can be modified using LIC to compensate for local illumination variations. According to one embodiment of the present disclosure, the updated value p of the sample (e.g., reference sample) within the predictor f [x,y] is the value p of the sample within the predictor as shown in Equation 4 i can be based on a linear function of p f [x,y]=(α + μ1)×p i [x,y]+(β + μ2×T avg ) Equation 4

[0146] Equation 4 can be described as the following Equation 5 p f [x,y]=α f ×p i [x,y]+β f Equation 5

[0147] In Equation 5, the final scaling coefficient α f is equal to the sum of the scaling coefficient α and the first parameter μ1, and the final offset β fis based on the offset β and the second parameter μ2. In one example, the final offset β f is equal to (β + μ2 × T avg ). Equation 5 shows that the updated predictor can be determined based on the final scaling coefficient α f , the final offset β f , and the predictor (e.g., the reference block (1703)).

[0148] The parameter adjustment is not applied to the LIC when the first parameter μ1 and the second parameter μ2 of Equation 4 are equal to zero.

[0149] As described above, the scaling coefficient α and the offset β can be determined based on the current template (e.g., the current template (1721)) of the current block (1701) and the reference template (e.g., the reference template (1725)) of the reference block (1703) using any suitable method such as the least squares method.

[0150] The parameter T avg can be determined from the reference template (e.g., the reference template (1725)) and / or the current template (e.g., the current template (1721)) of the current block (1701). In one example, the parameter T avg is the average value of the reference template (e.g., the reference template (1725)). For example, the parameter T avg is the average value of the sample values of the entire or a subset of the reference template (e.g., the reference template (1725)). In one example, the parameter T avg is the average value of the current template (e.g., the current template (1721)). For example, the parameter T avg is the average value of the sample values of the entire or a subset of the current template.

[0151] In one example, the parameter T avgThe reference template used to determine is different from the reference template used to determine the scaling factor α and the offset β. In one example, the parameter T avg The current template used to determine is different from the current plate used to determine the scaling factor α and the offset β.

[0152] In one example, the parameter T avg is 1, and thus the final offset β f is equal to (β + μ2). Thus, the updated value p f [x, y] is equal to (α + μ1) × p i [x, y] + (β + μ2).

[0153] The first parameter μ1 and / or the second parameter μ2 can be signaled, for example indicated, by the LIC information of one or more blocks including the current block (1701). In one embodiment, the LIC information of one or more blocks is signaled in a video bitstream.

[0154] The first parameter μ1 and / or the second parameter μ2 can be signaled within a limited range of values such as from -5 to +5. In one example, the first parameter μ1 is signaled within a limited range of positive values or a limited range of negative values. In one example, the second parameter μ2 is signaled within a limited range of positive values or a limited range of negative values.

[0155] In one embodiment, the LIC information of one or more blocks indicates one of the first parameter μ1 and the second parameter μ2, and the other of the first parameter μ1 and the second parameter μ2 can be determined based on one of the first parameter μ1 and the second parameter μ2.

[0156] In one example, μ2 = -μ1. The LIC information of one or more blocks indicates the first parameter μ1, and the second parameter μ2 is determined as -μ1 from the first parameter μ1. In one example, the LIC information of one or more blocks indicates the second parameter μ2, and the first parameter μ1 is determined as -μ2 from the second parameter μ2.

[0157] When the relationship between the first parameter μ1 and the second parameter μ2 (e.g., μ2 = -μ1) is known to, for example, a decoder, only the information (e.g., LIC information) indicating one of the first parameter μ1 and the second parameter μ2 is signaled in the bitstream. For example, μ2 = -μ1, which is the LIC information indicating only the first parameter μ1, is signaled in the bitstream. In one example, only the first parameter μ1 is signaled in the bitstream.

[0158] In one embodiment, one of (i) the first parameter μ1 and (ii) the second parameter μ2 is equal to zero, and one of (i) the first parameter μ1 and (ii) the second parameter μ2 is not signaled. In one embodiment, the LIC information of one or more blocks does not indicate one of (i) the first parameter μ1 and (ii) the second parameter μ2. For example, the first parameter μ1 is equal to zero, and the LIC information of one or more blocks does not indicate the first parameter μ1. In one example, the first parameter μ1 is equal to zero and is not signaled in the bitstream. In one example, the second parameter μ2 is equal to zero and is not signaled in the bitstream.

[0159] The LIC information of one or more blocks can include (i) the first parameter μ1 and / or the second parameter μ2 or (ii) one or more indexes indicating the first parameter μ1 and / or the second parameter μ2.

[0160] The first parameter μ1 can be a floating-point value and can be quantized with a first plurality of bits. The LIC information of one or more blocks can include the first plurality of bits. The second parameter μ2 can be a floating-point value and can be quantized with a second plurality of bits. The LIC information of one or more blocks can include the second plurality of bits.

[0161] The LIC information of one or more blocks can include at least one index indicating at least one of the first parameter μ1 or the second parameter μ2. The first parameter μ1 and / or the second parameter μ2 can be signaled by one or more indexes indicating a (one or more) look-up table.

[0162] In one example, the look-up table shows the relationship between an index and a corresponding parameter pair (e.g., the first parameter μ1 and the second parameter μ2), and the LIC information includes a single index indicating the first parameter μ1 and the second parameter μ2.

[0163] In one example, the first look-up table shows a first relationship between a first index and the first parameter μ1, the second look-up table shows a second relationship between a second index and the second parameter μ2, and thus the LIC information includes a first index indicating the first parameter μ1 and a second index indicating the second parameter μ2. When the first parameter μ1 or the second parameter μ2 is zero, a single index is used to indicate the non-zero first parameter μ1 or the second parameter μ2. When the relationship between the first parameter μ1 and the second parameter μ2 (e.g., μ2 = -μ1) is known, a single index can be used to indicate the first parameter μ1 or the second parameter μ2.

[0164] The LIC information of one or more blocks can be signaled at any appropriate level, such as at the coding unit (CU) level or a higher level than the CU level (e.g., CTU level, slice level, etc.).

[0165] In one example, the LIC information of one or more blocks is signaled at the CU level, the one or more blocks are within the same CU, and the first parameter μ1 and the second parameter μ2 are applicable to the CU. Different CUs can have different first parameters and / or different second parameters. For example, the first parameter μ1 and the second parameter μ2 of the first CU are different from the first parameter μ1 and the second parameter μ2 of the second CU, respectively.

[0166] In one example, the LIC information of one or more blocks is signaled at a higher level such as the slice level. The one or more blocks include blocks within multiple CUs in the slice. The first parameter μ1 and the second parameter μ2 are applicable to the multiple CUs within the slice. The multiple CUs within the slice can have the same first parameter μ1. The multiple CUs within the slice can have the same second parameter μ2.

[0167] In one example, one or more indexes indicating the first parameter μ1 and / or the second parameter μ2 are signaled at different levels such as the CU level, CTU level, slice level, etc.

[0168] The above-described embodiments can be suitably adapted when the LIC operates at the sub-block level within the CU, for example, when the LIC is executed at the sub-block level within the current block. The current block can include a plurality of sub-blocks. Each sub-block can include one or more samples within the current block. For example, each of the plurality of sub-blocks can be associated with the MV of its respective sub-block. The MVs associated with each of the plurality of sub-blocks can be different. Each MV can indicate its respective reference sub-block within the reference picture. The plurality of sub-blocks can be predicted respectively based on the plurality of reference sub-blocks associated with their respective MVs. In one example, the plurality of sub-blocks are predicted using an affine merge mode, an affine AMVP mode, an affine MMVD mode, etc.

[0169] The plurality of sub-blocks can include a first sub-block and a second sub-block. The LIC information of one or more blocks indicating the first parameter μ1 and / or the second parameter μ2 can be applied to one or more of the plurality of sub-blocks of the current block. The first parameter μ1 and the second parameter μ2 can be applied to the plurality of sub-blocks. For example, the first sub-block and the second sub-block have the same first parameter μ1, and the first sub-block and the second sub-block have the same second parameter μ2.

[0170] In one embodiment, each sub-block has its respective set of derived parameters used by the LIC.

[0171] In the first sub-block within the current block, Equation 4 can be adapted to Equation 6. The updated value p of the first sample within the first predictor sub-block (e.g., the first reference sub-block) f1 [x1,y1] is a linear function p of the value of the first sample i1 and can be [x1,y1]. p f1 [x1,y1]=(α i1 +μ1)×pi1 [x1, y1] + (β i1 + μ2 × T avg,1 ) Equation 6

[0172] The first MV of the first sub-block indicates the first reference sub-block. The first initial scaling factor α i1 and the first initial offset β i1 are associated with the first sub-block to compensate for local illumination changes for the first sub-block. The parameter T avg,1 can be associated with the first sub-block to compensate for local illumination changes for the first sub-block. The first initial scaling factor α i1 and the first initial offset β i1 can be determined based on the first part of the current template and the first part of the reference template. For example, the first part of the current template includes samples of the reconstructed spatially adjacent block(s) of the first sub-block. The first part of the reference template includes samples of the reconstructed spatially adjacent block(s) of the first reference sub-block. The parameter T avg,1 can be determined based on the first part of the current template and / or the first part of the reference template.

[0173] In the second sub-block within the current block, Equation 4 can be adapted to Equation 7. The updated value p f2 [x2, y2] of the second sample in the second predictor sub-block (e.g., the second reference sub-block) in the predictor can be a linear function of the value of the second sample p i2 [x2, y2]. p f2 [x2, y2] = (α i2 + μ1) × p i2 [x2, y2] + (β i2 + μ2 × T avg,2 ) Equation 7

[0174] The second MV of the second sub-block indicates the second reference sub-block. The second initial scaling factor αi2 and a second initial offset β i2 is associated with the second sub-block to compensate for local illumination changes to the second sub-block. Parameter T avg,2 is capable of being associated with the second sub-block to compensate for local illumination changes to the second sub-block. The second initial scaling factor α i2 and a second initial offset β i2 can be determined based on the second part of the current template and the second part of the reference template. For example, the second part of the current template includes samples of the reconfigured spatially adjacent block(s) of the second sub-block. The second part of the reference template includes samples of the reconfigured spatially adjacent block(s) of the second reference sub-block. Parameter T avg,2 can be determined based on the second part of the current template and / or the second part of the reference template.

[0175] In one embodiment, the plurality of sub-blocks share the same set of derived parameters (e.g., the first initial scaling factor α i1 , the first initial offset β i1 , and / or parameter T avg,1 ). For example, the first initial scaling factor α i1 is equal to the second initial scaling factor α i2 , and the first initial offset β i1 is equal to the second initial offset β i2 . In one example, parameter T avg,1 is parameter T avg,2Equal to. The shared parameter sets of multiple sub - blocks can be determined based on the current template and the reference template. In one example, the reference template can be determined based on the boundary sub - blocks of the current block that are in the vicinity of other (one or more) blocks outside the current block. For example, the MV associated with the boundary sub - block can point to multiple sub - blocks within the reference block, and the reference template includes samples of the re - configured spatially adjacent (one or more) blocks of the multiple sub - blocks within the reference block. In one example, the reference template includes a first portion of the reference template that can be determined based on a first MV and a second portion of the reference template that can be determined based on a second MV.

[0176] Figure 18 shows a flowchart outlining an encoding process (1800) according to an embodiment of the present disclosure. In various embodiments, the process (1800) is executed by a processing circuit such as a processing circuit within terminal devices (310), (320), (330), and (340), or a processing circuit that executes the functions of a video encoder (e.g., (403), (603), (703)). In some embodiments, the process (1800) is implemented by software instructions, and thus, when the processing circuit executes the software instructions, the processing circuit executes the process (1800). The process starts at (S1801) and proceeds to (S1810).

[0177] (S1810), an initial scaling factor α of the first sub - block within the current block i1 , an initial offset β of the first sub - block i1 , and at least one of a first parameter μ1 and a second parameter μ2 of one or more blocks can be determined. The one or more blocks can include the current block encoded by the LIC. The first MV of the first sub - block points to a first reference block of the reference block within the reference picture. The reference block corresponds to the current block.

[0178] The initial scaling coefficient α of the first sub-block within the current block i1 and the initial offset β of the first sub-block within the current block i1 can be determined based on the first part of the current template of the current block and the first part of the reference template of the reference block.

[0179] In one example, the initial scaling coefficient α of the first sub-block within the current block i1 and the initial offset β of the first sub-block within the current block i1 can be determined based on the current template of the current block and the reference template of the reference block.

[0180] The first parameter μ1 of one or more blocks and / or the second parameter μ2 of one or more blocks can be determined based on one or more blocks.

[0181] In one example, a higher level (e.g., CTU or slice) than the CU includes one or more first blocks coded by LIC and one or more second blocks not coded by LIC. One or more of the first blocks can have the same first parameter μ1 and the same second parameter μ2 determined based on, for example, one or more of the one or more first blocks. Alternatively, one or more of the first blocks can have different first parameters μ1 and different second parameters μ2.

[0182] (In S1820), in one example, the final scaling coefficient α of the first sub-block f1 is determined based on the first parameter μ1 and the initial scaling coefficient α i1 For example, the final scaling coefficient α of the first sub-block within the current block f1 is the first parameter μ1 of one or more blocks and the initial scaling coefficient α of the first sub-block within the current blocki1 is determined to be the sum with

[0183] In one example, the final offset β of the first sub-block f1 is determined based on the second parameter μ2 and the initial offset β i1 For example, the parameter T of the first sub-block within the current block avg,1 is determined based on at least one of the first part of the current template or the first part of the reference template. The final offset β of the first sub-block within the current block f1 is (β i1 + μ2 × T avg,1 ) and is determined to be so.

[0184] In one example, the parameter T avg,1 can be determined based on the current template of the current block and the reference template of the reference block.

[0185] (S1830) In this case, the updated first predictor sub-block (e.g., the updated first reference sub-block) within the predictor (e.g., the reference block) corresponding to the current block can be determined based on the final scaling factor α f1 the final offset β f1 and the first predictor sub-block (e.g., the first reference sub-block) within the predictor.

[0186] (S1840) In this case, the first sub-block within the current block can be coded based on the updated first predictor sub-block. The LIC information of one or more blocks indicating the first parameter μ1 and / or the second parameter μ2 can be coded.

[0187] The coded LIC information of one or more blocks can be signaled in the video bitstream. The LIC information of one or more blocks can be signaled at the coding unit (CU) level or a level higher than the CU level.

[0188] In one example, one of (i) the first parameter μ1 and (ii) the second parameter μ2 is equal to zero, and the LIC information of one or more blocks does not indicate one of (i) the first parameter μ1 and (ii) the second parameter μ2.

[0189] In one example, the LIC information of one or more blocks includes at least one index indicating at least one of the first parameter μ1 or the second parameter μ2.

[0190] In one example, at least one of the first parameter μ1 or the second parameter μ2 is a floating-point value, quantized in multiple bits, and the LIC information of one or more blocks includes multiple bits.

[0191] The process (1800) then proceeds to (S1899) and ends.

[0192] The process (1800) can be appropriately adapted to various scenarios, and the steps within the process (1800) can be adjusted accordingly. One or more of the steps within the process (1800) can be adapted, omitted, repeated, and / or combined. Any suitable order can be used to implement the process (1800). One or more additional steps may be added.

[0193] In one example, the LIC information of one or more blocks indicates one of (i) the first parameter μ1 and (ii) the second parameter μ2, and the other of (i) the first parameter μ1 and (ii) the second parameter μ2 is determined based on one of (i) the first parameter μ1 and (ii) the second parameter μ2.

[0194] In one example, the first sub-block within the current block is the current block, the first predictor sub-block within the predictor is the predictor (e.g., the reference block), the first portion of the current template is the current template, and the first portion of the reference template is the reference template. In one example, the updated predictor is determined using Equation 4 or Equation 5.

[0195] In one embodiment, the current block includes a first sub-block and a second sub-block, and at least one of the first parameter μ1 or the second parameter μ2 indicated in the LIC information of one or more blocks is applied to the first sub-block and the second sub-block. The second sub-block has an initial scaling factor α i1 which may be the same as or different from the initial scaling factor α i2 of the first sub-block and an initial offset β i1 which may be the same as or different from the initial offset β i2 associated with the first sub-block. The updated second predictor sub-block (e.g., the updated second reference sub-block) within the predictor corresponding to the second sub-block may be determined using Equation 7. The second sub-block may be encoded based on the updated second predictor sub-block.

[0196] FIG. 19 shows a flowchart outlining a decoding process (1900) according to an embodiment of the present disclosure. In various embodiments, the process (1900) is executed by processing circuitry such as in terminal devices (310), (320), (330), and (340), processing circuitry that executes the functions of video encoder (403), processing circuitry that executes the functions of video decoder (410), processing circuitry that executes the functions of video decoder (510), and processing circuitry that executes the functions of video encoder (603). In some embodiments, the process (1900) is implemented by software instructions, and thus, when the processing circuitry executes the software instructions, the processing circuitry executes the process (1900). The process starts at (S1901) and proceeds to (S1910).

[0197] (In S1910), prediction information of one or more blocks can be decoded from the coded video bitstream. The prediction information indicates that local illumination compensation (LIC) is applied to one or more blocks, and can include LIC information of one or more blocks including the current block to be reconstructed.

[0198] In one example, the LIC information of one or more blocks is signaled at the coding unit (CU) level.

[0199] In one example, the LIC information of one or more blocks is signaled at a level higher than the CU level.

[0200] (In S1920), the final scaling coefficient α of the first sub-block within the current block f1 and the final offset β of the first sub-block within the current block f1 can be determined based on the LIC information.

[0201] In one embodiment, the initial scaling coefficient α of the first sub-block within the current block i1 and the initial offset β of the first sub-block within the current block i1 are determined based on the first part of the current template of the current block and the first part of the reference template of the reference block.

[0202] In one example, the initial scaling coefficient α of the first sub-block within the current block i1 and the initial offset β of the first sub-block within the current block i1 can be determined based on the current template of the current block and the reference template of the reference block.

[0203] The LIC information of one or more blocks can be signaled in the coded video bitstream and can indicate at least one of the first parameter μ1 of the one or more blocks and the second parameter μ2 of the one or more blocks. The final scaling factor α of the first sub-block within the current block f1 can be determined based on the first parameter μ1 of the one or more blocks and the initial scaling factor α of the first sub-block within the current block i1 . The final offset β of the first sub-block within the current block f1 can be determined based on the second parameter μ2 of the one or more blocks and the initial offset β of the first sub-block within the current block i1 .

[0204] In one example, the final scaling factor α of the first sub-block within the current block f1 is determined to be the sum of the first parameter μ1 of the one or more blocks and the initial scaling factor α of the first sub-block within the current block i1 .

[0205] In one example, the parameter T of the first sub-block within the current block avg,1 is determined based on at least one of the first part of the current template or the first part of the reference template, and the final offset β of the first sub-block within the current block f1 is determined to be (β i1 + μ2 × T avg,1 ).

[0206] In one example, the parameter T avg,1 can be determined based on the current template of the current block and the reference template of the reference block.

[0207] In one example, the LIC information of one or more blocks indicates one of (i) a first parameter μ1 and (ii) a second parameter μ2, and the other of (i) the first parameter μ1 and (ii) the second parameter μ2 is determined based on one of (i) the first parameter μ1 and (ii) the second parameter μ2.

[0208] In one example, one of (i) the first parameter μ1 and (ii) the second parameter μ2 is equal to zero, and the LIC information of one or more blocks does not indicate one of (i) the first parameter μ1 and (ii) the second parameter μ2.

[0209] In one example, the LIC information of one or more blocks includes at least one index indicating at least one of the first parameter μ1 or the second parameter μ2.

[0210] In one example, at least one of the first parameter μ1 or the second parameter μ2 is a floating-point value, quantized in multiple bits, and the LIC information of one or more blocks includes multiple bits.

[0211] (S1930), the updated first predictor sub-block in the predictor corresponding to the current block is the final scaling factor α f1 , the final offset β f1 , and can be determined based on the first predictor sub-block. As described above, the predictor can be determined based on a reference block. In one example, the predictor is a reference block. For example, the sample values of the predictor are equal to the respective sample values of the reference block. The updated value of the first sample in the first predictor sub-block in the predictor is α f1 ×p i1 +β f1 and may be equal. p i1 can be the value of the first sample in the first predictor sub-block in the predictor.

[0212] In (S1940), the first sub-block within the current block can be reconstructed based on the updated first predictor sub-block within the predictor.

[0213] In one example, the sample values of the first sub-block within the current block are equal to the corresponding sample values within the updated first predictor sub-block in the predictor.

[0214] In one example, the first sub-block within the current block is reconstructed based on the updated first predictor sub-block within the predictor and additional information (e.g., residual data).

[0215] The process (1900) can be suitably adapted to various scenarios, and the steps within the process (1900) can be adjusted accordingly. One or more of the steps within the process (1900) can be adapted, omitted, repeated, and / or combined. Any suitable order can be used to implement the process (1900). One or more additional steps can be added.

[0216] In one embodiment, the first sub-block within the current block is the current block, the first predictor sub-block within the predictor is the predictor (e.g., the reference block of the current block), the first part of the current template is the current template, and the first part of the reference template is the reference template of the reference block. In one example, the updated predictor is determined using Equation 4 or Equation 5.

[0217] In one embodiment, the current block includes a first sub-block and a second sub-block, and at least one of the first parameter μ1 or the second parameter μ2 indicated in the LIC information of one or more blocks is applied to the first sub-block and the second sub-block. The second sub-block can have an initial scaling factor α i1 that is the same as or different from i2and an initial offset β of the first sub-block i1 Another initial offset β that may be the same as or different from i2 is associated. The updated second predictor sub-block in the predictor corresponding to the second sub-block can be determined using Equation 7. The second sub-block can be encoded based on the updated second predictor sub-block.

[0218] Embodiments of the present disclosure may be used separately or combined in any order. Further, each of the methods (or embodiments), encoders, and decoders may be implemented by a processing circuit (e.g., one or more processors or one or more integrated circuits). In one example, one or more processors execute a program stored in a non-transitory computer-readable medium.

[0219] The techniques described above can be implemented as computer software using computer-readable instructions physically stored on one or more computer-readable media. For example, FIG. 20 shows a computer system (2000) suitable for implementing certain embodiments of the disclosed subject matter.

[0220] The computer software can be coded using any suitable machine code or computer language that can undergo assembly, compilation, linking, or similar mechanisms to create code that includes instructions that can be executed directly by one or more computer central processing units (CPUs) and graphics processing units (GPUs), etc., or via interpretation, microcode execution, etc.

[0221] The instructions can be executed on various types of computers or computer components, including, for example, personal computers, tablet computers, servers, smartphones, game consoles, Internet of Things devices, etc.

[0222] Regarding the computer system (2000), the components shown in FIG. 20 are essentially exemplary and are not intended to suggest any limitation regarding the use or function scope of the computer software implementing the embodiments of the present disclosure. The configuration of the components should not be construed as having any dependency or requirement regarding any one or combination of the components shown in the exemplary embodiments of the computer system (2000).

[0223] The computer system (2000) may include a specific human interface input device. Such a human interface input device may respond to input by one or more human users via, for example, tactile input (e.g., keystrokes, swipes, movement of a data glove), audio input (e.g., voice, clapping), visual input (e.g., gestures), and olfactory input (not shown). The human interface device can also be used to capture specific media that is not necessarily directly related to conscious input by humans, such as audio (speech, music, ambient sound, etc.), images (scanned images, photographic images obtained from a still image camera, etc.), and video (two-dimensional video, three-dimensional video including stereoscopic video, etc.).

[0224] The input human interface device may include one or more (only one of each shown) of a keyboard (2001), a mouse (2002), a trackpad (2003), a touch screen (2010), a data glove (not shown), a joystick (2005), a microphone (2006), a scanner (2007), and a camera (2008).

[0225] The computer system (2000) may also include certain human interface output devices. Such human interface output devices can stimulate the senses of one or more human users, for example, by tactile output, sound, light, and smell / taste. Such human interface output devices include tactile output devices (e.g., tactile feedback by a touch screen (2010), a data glove (not shown), or a joystick (2005), although there may also be tactile feedback devices that do not function as input devices), audio output devices (e.g., speakers (2009), headphones (not shown)), visual output devices (e.g., screens (2010) including CRT screens, LCD screens, plasma screens, OLED screens, each with or without a touch screen input function and each with or without a tactile feedback function, some of which can output two-dimensional visual output, or stereoscopic images, virtual reality glasses (not shown), holographic displays, and four-dimensional or higher-dimensional output by means such as a smoke tank (not shown)), and may also include a printer (not shown).

[0226] The computer system (2000) may also include memory devices and their associated media accessible by humans, such as optical media including CD / DVD ROM / RW (2020) with media (2021) such as CD / DVDs, thumb drives (2022), removable hard drives or solid state drives (2023), legacy magnetic media such as tapes and floppy disks (not shown), dedicated ROM / ASIC / PLD-based devices such as security dongles (not shown), etc.

[0227] Those skilled in the art should also understand that the term "computer-readable medium" as used in connection with the subject matter of this disclosure does not include a transmission medium, a carrier wave, or other transient signals.

[0228] The computer system (2000) can also include an interface (2054) to one or more communication networks (2055). The network can be, for example, wireless, wired, or optical. The network can further be local, wide area, metropolitan, vehicular and industrial, real-time, delay tolerant, etc. Examples of networks include local area networks such as Ethernet and wireless LAN, cellular networks including GSM, 3G, 4G, 5G, LTE, etc., and television wired or wireless wide area digital networks including cable television, satellite television, and terrestrial broadcast television, and vehicular and industrial including CANBus. A particular network typically requires an external network interface adapter attached to a particular general-purpose data port or peripheral bus (2049) (such as a USB port of the computer system (2000)), and other networks are typically integrated into the core of the computer system (2000) by attaching to the system bus as described below (such as an Ethernet interface to a PC computer system or a cellular network interface to a smartphone computer system). Using any of these networks, the computer system (2000) can communicate with other entities. Such communication can be unidirectional, receive only (such as television broadcast), transmit only unidirectional (such as CANbus to a particular CANbus device), or bidirectional to other computer systems using, for example, local or wide area digital networks. Particular protocols and protocol stacks can be used for each of those networks and network interfaces as described above.

[0229] The aforementioned human interface device, human-accessible storage device, and network interface can be attached to the core (2040) of the computer system (2000).

[0230] The core (2040) can include one or more central processing units (CPUs) (2041), a graphics processing unit (GPU) (2042), a dedicated programmable processing device in the form of a field programmable gate array (FPGA) (2043), a hardware accelerator for specific tasks (2044), a graphics adapter (2050), etc. These devices can be connected via a system bus (2048) together with a read-only memory (ROM) (2045), a random access memory (2046), an internal mass storage such as an internal non-user-accessible hard drive, SSD (2047). In some computer systems, the system bus (2048) is accessible in the form of one or more physical plugs, enabling expansion by additional CPUs, GPUs, etc. Peripheral devices can be attached directly to the core's system bus (2048) or through a peripheral bus (2049). In one example, a screen (2010) can be connected to a graphics adapter (2050). Peripheral bus architectures include PCI, USB, etc.

[0231] The CPU (2041), GPU (2042), FPGA (2043), and accelerator (2044) can execute specific instructions that can be combined to form the aforementioned computer code. That computer code can be stored in the ROM (2045) or RAM (2046). Migration data can also be stored in the RAM (2046), while persistent data can be stored, for example, in the internal mass storage (2047). Fast storage and retrieval to any of the memory devices can be enabled by the use of cache memory that can be closely associated with one or more CPUs (2041), GPUs (2042), mass storage (2047), ROM (2045), RAM (2046), etc.

[0232] A computer-readable medium can have computer code for performing various computer-implemented operations. The medium and the computer code may be specially designed and constructed for the purposes of this disclosure, or may be of the kind well-known and available to those having skill in the computer software arts.

[0233] By way of example and not limitation, a computer system (2000) having an architecture, and in particular a core (2040), can provide functionality as a result of one or more processors (including, for example, a CPU, GPU, FPGA, accelerator, etc.) executing software embodied on one or more tangible computer-readable media. Such computer-readable media can be associated with user-accessible mass storage as described above, as well as media associated with particular storage of the core (2040) that is non-transitory in nature, such as core internal mass storage (2047) and ROM (2045). The software implementing various embodiments of the present disclosure can be stored on such devices and executed by the core (2040). The computer-readable media can include one or more memory devices or chips, depending on particular requirements. The software can cause the core (2040), specifically the processor(s) therein (including, for example, a CPU, GPU, FPGA, etc.), to define data structures stored in RAM (2046) and modify such data structures according to processes defined by the software, thereby executing particular processes or particular portions of particular processes described herein. Additionally or alternatively, the computer system can provide functionality as a result of logic embodied in circuitry (e.g., accelerator (2044)) in a hard-wired or other manner, which can operate in place of or in conjunction with software to execute particular processes or particular portions of particular processes described herein. References to software can, if desired, include logic, and vice versa. References to computer-readable media can, if desired, include 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.

[0234] Appendix A: Acronyms JEM: joint exploration model VVC: Versatile Video Coding (Multi-purpose Video Coding) BMS: Benchmark Set (Benchmark Set) MV: Motion Vector (Motion Vector) HEVC: High Efficiency Video Coding (High Efficiency Video Coding) SEI: Supplementary Enhancement Information (Supplementary Enhancement Information) VUI: Video Usability Information (Video Usability Information) GOP: Groups of Pictures (Picture Group) TU: Transform Units (Transform Units) PU: Prediction Units (Prediction Units) CTU: Coding Tree Units (Coding Tree Units) CTB: Coding Tree Blocks (Coding Tree Blocks) PB: Prediction Blocks (Prediction Blocks) HRD: Hypothetical Reference Decoder (Hypothetical Reference Decoder) SNR: Signal Noise Ratio (Signal Noise Ratio) CPU: Central Processing Units (Central Processing Unit) GPU: Graphics Processing Units (Graphics Processing Unit) CRT: Cathode Ray Tube (Cathode Ray Tube) LCD: Liquid-Crystal Display (Liquid Crystal Display) OLED: Organic Light-Emitting Diode (Organic Light-Emitting Diode) CD: Compact Disc (Compact Disc) DVD: Digital Video Disc (Digital Video Disk) ROM: Read-Only Memory (Read-Only Memory) RAM: Random Access Memory (Random Access Memory) ASIC: Application-Specific Integrated Circuit (Application-Specific Integrated Circuit) PLD: Programmable Logic Device (Programmable Logic Device) LAN: Local Area Network (Local Area Network) GSM: Global System for Mobile communications (Global System for Mobile Communications) LTE: Long-Term Evolution (Long-Term Evolution) CANBus: Controller Area Network Bus (Controller Area Network Bus) USB: Universal Serial Bus (Universal Serial Bus) PCI: Peripheral Component Interconnect (Peripheral Component Interconnect) FPGA: Field Programmable Gate Areas (Field Programmable Gate Areas) SSD: solid-state drive (Solid-State Drive) IC: Integrated Circuit (Integrated Circuit) CU: Coding Unit (Coding Unit) R-D: Rate-Distortion (Rate-Distortion)

[0235] Although this disclosure describes some exemplary embodiments, there are changes, substitutions, and various alternative equivalents that are within the scope of this disclosure. Accordingly, it will be understood by those skilled in the art that many systems and methods can be devised that embody the principles of this disclosure but are not explicitly shown or described herein and are thus within the spirit and scope of this disclosure.

Description of Reference Numerals

[0236] 101 Sample 102, 103 Arrows 104 Square Block 201 Current Block 202, 203, 204, 205, 206 Samples 300 Communication System 310, 320, 330, 340 Terminal Devices 350 Communication Network 400 Communication System 401 Video Source 402 Video Picture Stream 403 Video Encoder 404 Encoded Video Data 405 Streaming Server 406 Client Subsystem 407 Input Copy of Encoded Video Data 408 Client Subsystem 409 Copy of Encoded Video Data 410 Video Decoder 411 Output Stream of Video Picture 412 Display 413 Capture Subsystem 420 Electronic Device 430 Electronic Device 501 Channel 510 Video Decoder 512 Rendering Device 515 Buffer Memory 520 Entropy Decoder / Parser 521 symbols 530 Electronic device 531 Receiver 551 Scaler / inverse conversion 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 source 603 Video encoder 620 Electronic device 630 Source coder 632 Coding engine 633 Local video decoder 634 Reference picture memory 635 Predictor 640 Transmitter 643 Video sequence 645 Entropy coder 650 Controller 660 Communication channel 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 Inter encoder 810 Video decoder 871 Entropy decoder 872 Intra decoder 873 Residual decoder 874 Reconstruction module 880 Inter decoder 901 Current block 1101 Current picture 1102 Current reference picture 1103 Collocate picture 1104 Collocate reference picture 1111 Current CU 1112 Collocate CU 1121 Scaled MV 1401 Motion vector 1402 Luma sub-block 1410 Current block 1510 Current CU 1520 Current CU 1701 Current block 1703 Reference block 1721 Current template 1722 Upper template 1723 Left template 1725 Reference template 1727 Left template 1731 Upper left template 1800 Encoding process 1900 Decoding process 2000 Computer system 2001 Keyboard 2002 Mouse 2003 Track pad 2005 Joystick 2006 Microphone 2007 Scanner 2008 Camera 2009 Speaker 2010 Touch screen 2020 CD / DVD ROM / RW 2021 Media such as CD / DVD 2022 Thumb drive 2023 Removable hard drive or solid state drive 2040 Core 2041 Central processing unit (CPU) 2042 Graphics processing unit (GPU) 2043 Field Programmable Gate Array (FPGA) 2044 Hardware Accelerator 2045 Read Only Memory (ROM) 2046 Random Access Memory, RAM 2047 Internal Mass Storage 2048 System Bus 2049 Peripheral Bus 2050 Graphics Adapter 2054 Interface 2055 Communication Network

Claims

【Claim 1】 A method for video decoding in a video decoder, comprising: decoding prediction information of one or more blocks from a coded video bitstream, the prediction information indicating that local illumination compensation (LIC) is applied to the one or more blocks, and including LIC information of the one or more blocks, the one or more blocks including a current block to be reconstructed; The first parameter μ of the one or more blocks indicated by the LIC information 1 or at least one offset information of the second parameter μ of the one or more blocks 2 Based on this, the final scaling factor α of the first sub-block within the current block f1 and the final offset β of the first sub-block within the current block f1 A step of determining, wherein the final scaling factor α f1 is the initial scaling factor α i1 and the first parameter μ 1 Based on this, the final offset β f1 is the initial offset β i1 and the second parameter μ 2 Based on this, a step, the final scaling factor α f1 the final offset β f1 and determining an updated first predictor sub-block in the predictor corresponding to the current block based on the first predictor sub-block in the predictor, wherein an updated value of a first sample in the first predictor sub-block in the predictor is α f1 × p i1 + β f1 is equal to, where p i1 is a value of the first sample in the first predictor sub-block in the predictor, the step and reconstructing the first sub-block in the current block based on the updated first predictor sub-block in the predictor; and A method comprising the steps of.

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