Explicit signaling to improve block adaptive weighting factors

Abstract

The embodiment of the invention relates to video coding and decoding, in particular to improvement of block adaptive weighted prediction (BAWP). A method includes receiving a video bitstream, the video bitstream including a current block and a reference block, the reference block being used to predict the current block and identified by a motion vector associated with the current block; from the video bitstream, determining a first syntax element indicating a scaling factor, the scaling factor stored in a first lookup table among at least two lookup tables maintained by a decoder for storing a plurality of candidate scaling factors or a plurality of candidate scaling factor differences, the plurality of candidate scaling factor differences refer to differences between the plurality of candidate scaling factors and a threshold value; determining the first lookup table; determining the scaling factor based on the value of the first syntax element and the first lookup table; predicting the current block based on the reference block, the scaling factor, and an offset; and reconstructing the current block on the basis of the predicted current block.

Description

[0001] This application claims priority to U.S. Application No. 18 / 461,759, filed on September 6, 2023, and U.S. Provisional Application No. 63 / 462,482, filed on April 27, 2023, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The embodiments of the present application are related to a set of advanced video / stream coding and decoding technologies. In particular, the disclosed technology is related to enhancing block adaptive weighted prediction (BAWP) and local illumination compensation (LIC) to compensate for local illumination changes. Background Art

[0003] Uncompressed digital video may include a series of pictures and impose specific bit rate requirements on transmission bandwidth in storage, data processing, and streaming applications. One purpose of video encoding and decoding may be to reduce redundancy in the uncompressed input video signal through various compression techniques. Summary of the invention

[0004] Embodiments of the present application relate to methods, apparatuses, and computer storage media for enhancing block adaptive weighted prediction (BAWP) to model local illumination compensation (LIC).

[0005] According to one aspect, an embodiment of the present application provides a method for processing video data in a decoder, the method comprising:

[0006] Receiving a video bitstream, the video bitstream comprising a current block and a reference block, the reference block being used to predict the current block and being identified by a motion vector associated with the current block;

[0007] Determine, from the video bitstream, a first syntax element indicating a scaling factor α, wherein the scaling factor is stored in a first lookup table of at least two lookup tables, wherein the at least two lookup tables are maintained by a decoder and are used to store a plurality of candidate scaling factors or a plurality of candidate scaling factor differences, wherein the plurality of candidate scaling factor differences refer to differences between the plurality of candidate scaling factors and a threshold;

[0008] determining the first lookup table storing the scaling factor;

[0009] Determining the scaling factor α based on the value of the first syntax element and the first lookup table;

[0010] Predicting the current block based on the reference block, the scaling factor α and the offset; and

[0011] Based on the predicted current block, the current block is reconstructed.

[0012] According to another aspect, an embodiment of the present application further provides a device for processing a current block of a current frame in an encoded video bitstream. The device comprises: a memory for storing computer instructions, and a processor communicating with the memory, wherein when the processor executes the computer instructions, the processor is configured to cause the device to perform the above-mentioned video decoding method.

[0013] According to another aspect, an embodiment of the present application further provides a non-transitory computer-readable storage medium having instructions stored thereon, which, when executed by a computer for video decoding and / or encoding, enables the computer to implement the above-mentioned video decoding method.

[0014] The above and other aspects and implementations thereof are described in more detail in the drawings, the description and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Other features, properties and various advantages of the disclosed subject matter will become further apparent from the following detailed description and accompanying drawings, in which:

[0016] Figure 1 is a schematic diagram of a simplified block diagram of a communication system (100) according to an embodiment;

[0017] Figure 2 is a schematic diagram of a simplified block diagram of a communication system (200) according to another embodiment;

[0018] Figure 3 is a schematic diagram of a simplified block diagram of a video decoder according to an embodiment;

[0019] Figure 4 is a schematic diagram of a simplified block diagram of a video encoder according to an embodiment;

[0020] Figure 5 shows a block diagram of a video encoder according to another embodiment;

[0021] Figure 6 shows a block diagram of a video decoder according to another embodiment;

[0022] Figure 7 A scheme for partitioning coding blocks according to an embodiment of the present application is shown;

[0023] Figure 8 Another scheme for coding block partitioning according to an embodiment of the present application is shown;

[0024] Fig. 9 Another scheme of coding block partitioning according to an embodiment of the present application is shown;

[0025] Fig.10 Compound motion compensation is shown;

[0026] Fig.11 An exemplary interpolated reference frame for motion compensation is shown;

[0027] Fig.12 An example of a template of a current block and a template of a reference block is shown;

[0028] Fig.13 An example of a logic flow of a method according to an embodiment of the present application is shown;

[0029] Fig.14 is a schematic diagram of a computer system according to an embodiment. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to the accompanying drawings, which form a part of the present invention and show by way of illustration specific examples of embodiments. However, please note that the present invention may be embodied in a variety of different forms and, therefore, the subject matter covered or claimed is intended to be construed as not limited to any embodiment described below. Please also note that the present invention may be embodied as a method, apparatus, assembly or system. Thus, embodiments of the present invention may, for example, take the form of hardware, software, firmware or any combination thereof.

[0031] Throughout the specification and claims, terms may have subtle meanings that are implied or suggested in the context rather than the express meaning. The phrases "in one embodiment" or "in some embodiments" as used herein do not necessarily refer to the same embodiment, and the phrases "in another embodiment" or "in other embodiments" as used herein do not necessarily refer to different embodiments. Similarly, the phrases "in one implementation" or "in some implementations" as used herein do not necessarily refer to the same implementation, and "in another implementation" or "in other implementations" as used herein do not necessarily refer to different implementations. For example, the claimed subject matter includes all or part of the combination of exemplary embodiments / implementations.

[0032] In general, terms can be understood at least in part from usage in context. For example, terms used herein, such as "and", "or", "and / or", can include multiple meanings, which can depend at least in part on the context in which these terms are used. Typically, "or", if used in an associative list, such as a, B, or C, means a, B, and C, which are used here in an inclusive sense, and a, B, or C, which are used here only in an exclusive sense. In addition, the terms "at least one" or "at least one" used herein, depending at least in part on the context, can be used to describe any feature, structure, or characteristic in a singular sense, or can be used to describe a combination of features, structures, and characteristics in a plural sense. Similarly, terms, such as "a", "an", or "the", can also be understood to convey singular or plural usage, depending at least in part on the context. In addition, the terms "based on" or "by" can be understood to not necessarily be intended to convey a set of exclusive factors, but rather to allow for the presence of other factors that are not necessarily explicitly described, again, depending at least in part on the context.

[0033] like Figure 1 As shown, the terminal device can be implemented as a server, a personal computer and a smart phone, but the applicability of the basic principles of the present application may not be limited thereto. Embodiments of the present application can be implemented in desktop computers, laptop computers, tablet computers, media players, wearable computers, dedicated video conferencing equipment, etc. Network (130) represents any number or type of network that transmits encoded video data between terminal devices, including, for example, wired (wired) and / or wireless communication networks. Communication network (130) can exchange data in circuit switching, packet switching and / or other types of channels. Representative networks include telecommunication networks, local area networks, wide area networks and / or the Internet.

[0034] As an example, Figure 2 The video encoder and video decoder are shown in a streaming environment. The subject matter disclosed in this application is equally applicable to other video-enabled applications, including, for example, video conferencing, digital TV, storing compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0035] like Figure 2As shown, the streaming system may include an acquisition subsystem (213), which may include a video source (201), such as a digital camera, for creating an uncompressed video picture stream (202). In an embodiment, the video picture stream (202) includes samples captured by the digital camera of the video source (201). Compared to the encoded video data (204) (or the encoded video bitstream), the video picture stream (202) is depicted as a thick line to emphasize the high data volume of the video picture stream, and the video picture stream (202) can be processed by an electronic device (420), which includes a video encoder (203) coupled to the video source (201). The video encoder (203) may include hardware, software, or a combination of hardware and software to implement or implement various aspects of the disclosed subject matter as described in more detail below. Compared to the video picture stream (202), the encoded video data (204) (or the encoded video bitstream (204)) is depicted as a thin line to emphasize the lower amount of data of the encoded video data (204) (or the encoded video bitstream (204)), which can be stored on the streaming server (205) for future use. At least one streaming client subsystem, such as Figure 3 The client subsystem (206) and the client subsystem (208) in the video transmission server (205) can access the streaming server (205) to retrieve the copy (207) and the copy (209) of the encoded video data (204). The client subsystem (206) can include, for example, a video decoder (210) in the electronic device (330). The video decoder (210) decodes the incoming copy (207) of the encoded video data and produces an output video picture stream (211) that can be presented on a display (212) (such as a display screen) or another presentation device (not depicted).

[0036] Figure 3 1 is a block diagram of a video decoder (310) according to an embodiment disclosed in the present application. The video decoder (310) may be provided in an electronic device (330). The electronic device (330) may include a receiver (331) (e.g., a receiving circuit). The video decoder (310) may be used to replace Figure 2 A video decoder (210) of an embodiment.

[0037] A receiver (331) may receive at least one encoded video sequence to be decoded by a video decoder (310). To prevent network jitter, a buffer memory (315) may be coupled between the receiver (331) and an entropy decoder / parser (320) (hereinafter referred to as "parser (320)"). The parser (320) reconstructs symbols (321) based on the encoded video sequence. The categories of these symbols include information for managing the operation of the video decoder (310) and potential information for controlling a display device such as a display device (312) (e.g., a display screen). The parser (320) may extract a subgroup parameter set for at least one subgroup of subgroups of pixels in the video decoder from the encoded video sequence based on at least one parameter corresponding to the group. The subgroup may include a group of pictures (Group of Pictures, GOP), a picture, a tile, a slice, a macroblock, a coding unit (Coding Unit, CU), a block, a transform unit (Transform Unit, TU), a prediction unit (Prediction Unit, PU), etc. The parser (320) may also extract information from the coded video sequence, such as transform coefficients, quantizer parameter values, motion vectors, and the like. The reconstruction of the symbols (321) may involve a number of different units. Which units are involved and how they are involved may be controlled by subgroup control information that the parser (320) parses from the coded video sequence. For the sake of brevity, such subgroup control information flow between the parser (320) and the various units below is not described.

[0038] The first unit is a sealer / inverse transform unit (351). The sealer / inverse transform unit (351) receives quantized transform coefficients as symbols (321) from the parser (320) and control information including which transform method to use, block size, quantization factor, quantization scaling matrix, etc. The sealer / inverse transform unit (351) may output a block including sample values, which may be input into an aggregator (355).

[0039] In some cases, the output samples of the scaler / inverse transform unit (351) may belong to an intra-coded block; that is, a block that does not use predictive information from a previously reconstructed picture, but may use predictive information from a previously reconstructed portion of the current picture. Such predictive information may be provided by an intra-picture prediction unit (352). In some cases, the intra-picture prediction unit (352) generates surrounding blocks of the same size and shape as the block being reconstructed using reconstructed information extracted from a current picture buffer (358). For example, the current picture buffer (358) buffers a partially reconstructed current picture and / or a fully reconstructed current picture. In some cases, the aggregator (355) adds the prediction information generated by the intra-prediction unit (352) to the output sample information provided by the scaler / inverse transform unit (351) on a per-sample basis.

[0040] In other cases, the output samples of the scaler / inverse transform unit (351) may belong to an inter-coded and potentially motion compensated block. In this case, the motion compensated prediction unit (353) may access the reference picture memory (357) to extract samples for prediction. After motion compensation of the extracted samples according to the symbols (321), these samples may be added to the output of the scaler / inverse transform unit (351) (in this case referred to as residual samples or residual signal) by an aggregator (355) to generate output sample information.

[0041] The output samples of the aggregator (355) can be used by various loop filtering techniques in the loop filter unit (356). The output of the loop filter unit (356) can be a sample stream that can be output to the display device (312) and stored in the reference picture memory (357) for subsequent inter-frame picture prediction.

[0042] Figure 4 4 is a block diagram of a video encoder (403) according to an embodiment disclosed in the present application. The video encoder (403) is provided in an electronic device (420). The electronic device (420) includes a transmitter (440) (e.g., a transmission circuit). The video encoder (403) can be used to replace Figure 4 A video encoder (403) in an embodiment.

[0043] The video encoder (403) may receive video samples from a video source (401). According to an embodiment, the video encoder (403) may encode and compress pictures of a source video sequence into an encoded video sequence (443) in real time or under any other time constraints required by the application. Implementing an appropriate encoding speed is a function of the controller (450). In some embodiments, the controller (450) controls other functional units as described below and is functionally coupled to these units. The parameters set by the controller (450) may include rate control related parameters (picture skipping, quantizer, lambda value of rate-distortion optimization techniques, etc.), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc.

[0044] In some embodiments, the video encoder (403) operates in a coding loop. As a simple description, in an embodiment, the coding loop may include a source encoder (430) (e.g., responsible for creating symbols, such as a symbol stream, based on the input picture to be encoded and the reference picture) and a (local) decoder (433) embedded in the video encoder (403). It can be observed at this point that any decoder technology other than parsing / entropy decoding present in the decoder must also exist in the corresponding encoder in substantially the same functional form. For this reason, the present application focuses on the decoder operation. The description of the encoder technology can be simplified because the encoder technology is mutually inverse to the decoder technology described comprehensively. A more detailed description is only required in certain areas and is provided below.

[0045] During operation, in some embodiments, the source encoder (430) may perform motion compensated predictive coding, which predictively encodes an input picture with reference to at least one previously encoded picture from a video sequence designated as a "reference picture."

[0046] The local video decoder (433) can decode the encoded video data that can be designated as a reference picture. The local video decoder (433) replicates the decoding process that can be performed by the video decoder on the reference picture and can cause the reconstructed reference picture to be stored in the reference picture cache (434). In this way, the video encoder (403) can locally store a copy of the reconstructed reference picture that has common content (absent transmission errors) with the reconstructed reference picture that will be obtained by the remote video decoder.

[0047] The predictor (435) may perform prediction search for the encoding engine (432). That is, for a new picture to be encoded, the predictor (435) may search the reference picture memory (434) for sample data (as a candidate reference pixel block) or certain metadata, such as reference picture motion vector, block shape, etc., that may serve as a suitable prediction reference for the new picture.

[0048] The controller (450) may manage encoding operations of the source encoder (430), including, for example, setting parameters and subgroup parameters for encoding video data.

[0049] The outputs of all of the above functional units may be entropy encoded in an entropy encoder (445). The transmitter (440) may buffer the encoded video sequence created by the entropy encoder (445) in preparation for transmission over a communication channel (460), which may be a hardware / software link to a storage device where the encoded video data will be stored. The transmitter (440) may combine the encoded video data from the video encoder (403) with other data to be transmitted, such as encoded audio data and / or auxiliary data streams (source not shown).

[0050] The controller (450) may manage the operation of the video encoder (403). During encoding, the controller (450) may assign a certain coded picture type to each coded picture, but this may affect the coding techniques that may be applied to the corresponding picture. For example, a picture may generally be assigned to any of the following picture types: intra picture (I picture), predictive picture (P picture), bidirectional predictive picture (B picture), multiple predicted pictures. A source picture may generally be spatially subdivided into a plurality of sample coding blocks, as described in further detail below.

[0051] Figure 5 1 is a diagram of a video encoder (503) according to another embodiment disclosed in the present application. The video encoder (503) is used to receive a processed block (e.g., a prediction block) of sample values ​​in a current video picture in a video picture sequence, and encode the processed block into an encoded picture that is part of an encoded video sequence. In this embodiment, the video encoder (503) is used to replace Figure 4 A video encoder (403) in an embodiment.

[0052] For example, the video encoder (503) receives a matrix of sample values ​​for a processing block. The video encoder (503) uses, for example, rate-distortion (RD) optimization to determine whether to use intra mode, inter mode, or bi-prediction mode to encode the processing block.

[0053] exist Figure 5 In an embodiment of the present invention, the video encoder (503) includes: Figure 5 Shown are an inter-frame encoder (530), an intra-frame encoder (522), a residual calculator (523), a switch (526), ​​a residual encoder (524), a general controller (521), and an entropy encoder (525) coupled together.

[0054] The inter-frame encoder (530) is used to receive samples of a current block (e.g., a processing block), compare the block with at least one reference block in a reference picture (e.g., blocks in a previous picture and a subsequent picture), generate inter-frame prediction information (e.g., redundant information description according to an inter-frame coding technique, motion vectors, merge mode information), and calculate an inter-frame prediction result (e.g., a predicted block) based on the inter-frame prediction information using any suitable technique. In some embodiments, the reference picture is a decoded reference picture decoded based on the encoded video information.

[0055] The intra-frame encoder (522) is used to receive samples of a current block (e.g., a processing block), compare the block with an encoded block in the same picture in some cases, generate quantization coefficients after transformation, and in some cases also generate intra-frame prediction information (e.g., intra-frame prediction direction information according to at least one intra-frame coding technique). In an embodiment, the intra-frame encoder (522) also calculates an intra-frame prediction result (e.g., a predicted block) based on the intra-frame prediction information and a reference block in the same picture.

[0056] The general controller (521) is used to determine general control data and control other components of the video encoder (503) based on the general control data, for example, determining a prediction mode of a block and providing a control signal to a switch (526) based on the prediction mode.

[0057] The residual calculator (523) is used to calculate the difference (residual data) between the received block and the prediction result selected from the intra-frame encoder (522) or the inter-frame encoder (530). The residual encoder (524) is used to operate based on the residual data to encode the residual data to generate a transform coefficient. The transform coefficient is then quantized to obtain a quantized transform coefficient. In various embodiments, the video encoder (503) also includes a residual decoder (528). The residual decoder (528) is used to perform an inverse transform and generate decoded residual data. The decoded residual data can be used appropriately by the intra-frame encoder (722) and the inter-frame encoder (730). The entropy encoder (525) is used to format the code stream to produce an encoded block.

[0058] Figure 6 FIG. 6 is a diagram of a video decoder (610) according to another embodiment disclosed in the present application. The video decoder (610) is used to receive an encoded image as part of an encoded video sequence and decode the encoded image to generate a reconstructed picture. In an embodiment, the video decoder (610) is used to replace Figure 4 A video decoder (410) of an embodiment.

[0059] exist Figure 6 In one embodiment, the video decoder (610) includes: Figure 6An entropy decoder (671), an inter-frame decoder (680), a residual decoder (673), a reconstruction module (674) and an intra-frame decoder (672) coupled together are shown in FIG.

[0060] The entropy decoder (671) is used to reconstruct certain symbols from the encoded picture, which represent the syntax elements constituting the encoded picture. The inter-frame decoder (680) is used to receive inter-frame prediction information and generate an inter-frame prediction result based on the inter-frame prediction information. The intra-frame decoder (672) is used to receive intra-frame prediction information and generate a prediction result based on the intra-frame prediction information. The residual decoder (673) is used to perform inverse quantization to extract dequantized transform coefficients, and process the dequantized transform coefficients to convert the residual from the frequency domain to the spatial domain. The reconstruction module (674) is used to combine the residual output by the residual decoder (673) with the prediction result (which can be output by the inter-frame prediction module or the intra-frame prediction module) in the spatial domain to form a reconstructed block, which can be part of the reconstructed picture, and the reconstructed picture can then be part of the reconstructed video. It should be noted that other suitable operations such as deblocking operations can be performed to improve visual quality.

[0061] It should be noted that the video encoder (203), video encoder (403) and video encoder (503) and video decoder (210), video decoder (310) and video decoder (610) may be implemented using any suitable technology. In an embodiment, the video encoder (203), video encoder (403) and video encoder (503) and video decoder (210), video decoder (310) and video decoder (610) may be implemented using at least one integrated circuit. In another embodiment, the video encoder (203), video encoder (403) and video encoder (503) and video decoder (210), video decoder (310) and video decoder (610) may be implemented using at least one processor that executes software instructions.

[0062] Turning to block partitioning for encoding and decoding, general partitioning can start from basic blocks and can follow a predefined set of rules, a specific pattern, a partition tree, or any partition structure or scheme. Partitioning can be hierarchical and recursive. After following any example partitioning procedure or other procedures described below or a combination thereof to divide or partition basic blocks, a final set of partitions or coding blocks can be obtained. Each of these partitions can be in one of the various partition levels in the partition hierarchy and can have various shapes. Each of the partitions can be referred to as a coding block (CB). For various example partitioning implementations further described below, each generated CB can have any allowed size and partitioning level. Such partitions are called coding blocks because they can form units to which some basic coding / decoding decisions can be made, and coding / decoding parameters can be optimized, determined, and signaled in the encoded video code stream. The highest or deepest level in the final partition represents the depth of the coding block partition structure of the tree. The coding block can be a luminance coding block or a chrominance coding block. The CB tree structure for each color can be referred to as a coding block tree (CBT). The coding blocks of all color channels may be collectively referred to as coding units (CUs). The hierarchical structure of all color channels may be collectively referred to as coding tree units (CTUs). The partitioning modes or structures of various color channels in a CTU may be the same or different.

[0063] In some embodiments, the partition tree schemes or structures for the luma and chroma channels may not have to be the same. In other words, the luma and chroma channels may have independent coding tree structures or modes. In addition, whether the luma and chroma channels use the same or different coding partition tree structures and the actual coding partition tree structures to be used may depend on whether the stripe being encoded is a P stripe, a B stripe, or an I stripe. For example, for an I stripe, the chroma channel and the luma channel may have independent coding partition tree structures or coding partition tree structure modes, while for a P stripe or a B stripe, the luma and chroma channels may share the same coding partition tree scheme. When independent coding partition tree structures or modes are applied, the luma channel may be partitioned into CBs by one coding partition tree structure, and the chroma channel may be partitioned into chroma CBs by another coding partition tree structure.

[0064] Figure 7 An example of a predefined 10-way partitioning structure / pattern is shown, which allows recursive partitioning to form a partition tree.The root block may start at a predefined level (eg, starting from a basic block at a 128x128 or 64x64 level). Figure 7 Example partition structures include various 2:1 / 1:2 and 4:1 / 1:4 rectangular partitions. In some example embodiments, further subdivision is not allowed. Figure 7The coding tree depth may be further defined to indicate the depth of the partition from the root node or the root block. For example, the coding tree depth of the root node or the root block may be set to 0, and after the root block is further partitioned once, as Figure 7 As shown, the coding tree depth is increased by 1. In some embodiments, only all square partitions in 710 may be allowed, following Figure 7 The mode recursively partitions to the next level of the partition tree.

[0065] In some other example implementations for coding block partitioning, a quadtree structure may be used. This quadtree segmentation may be applied hierarchically and recursively to any square-shaped partition. Whether a basic block or an intermediate block or partition is further quadtree segmented may be applicable to various local characteristics of the basic block or intermediate block / partition.

[0066] In yet other examples, a ternary partitioning scheme may be used to partition a basic block or any intermediate block, such as Figure 8 The ternary mode can be implemented vertically, as shown in 802, or horizontally, as shown in 804. Although Figure 8 The example segmentation ratio in is shown as 1:2:1, but other ratios may be predefined. In some embodiments, at least two different ratios may be predefined. In some embodiments, the width and height of the partitions of the example ternary tree are always powers of 2 to avoid additional transformations.

[0067] The above partitioning schemes can be combined in any manner at different partitioning levels. As an example, the above quadtree and binary partitioning schemes can be combined to partition basic blocks into a quadtree-binary tree (QTBT) structure. In this scheme, basic blocks or intermediate blocks / partitions can be quadtree-partitioned or binary-partitioned, if specified, subject to a predefined set of conditions. Fig. 9A specific example is illustrated in , where a basic block is first partitioned by a quadtree into four partitions, as shown in 902, 904, 906, and 908. Thereafter, each of the resulting partitions is partitioned by a quadtree into four additional partitions (such as 908) at the next level, or is binary partitioned into two additional partitions (horizontally or vertically, such as 902 or 906, for example, both are symmetrical), or is non-partitioned (such as 904). For square-shaped partitions, binary or quadtree partitioning can be recursively allowed, as shown in the entire example partitioning pattern of 910 and the corresponding tree structure / representation in 920, where solid lines represent quadtree partitioning and dashed lines represent binary partitioning. A flag can be used for each binary partition node (non-leaf binary partition) to indicate whether the binary partitioning is horizontal or vertical. For example, as shown in 920, consistent with the partitioning structure of 910, a flag "0" can represent a horizontal binary partition, and a flag "1" can represent a vertical binary partition. For quadtree partitioning, there is no need to indicate the partitioning type, because quadtree partitioning always partitions a block or partition horizontally and vertically to produce 4 sub-blocks / partitions of equal size. In some embodiments, a flag "1" may represent horizontal binary partitioning, and a flag "0" may represent vertical binary partitioning.

[0068] In some example implementations of QTBT, the quadtree and binary segmentation rule set may be represented by the following predefined parameters and corresponding functions associated therewith:

[0069] CTU size: the root node size of the quadtree (the size of the basic block)

[0070] MinQTSize: The minimum allowed size of a quadtree leaf node

[0071] MaxBTSize: Maximum allowed binary tree root node size

[0072] MaxBTDepth: Maximum allowed binary tree depth

[0073] MinBTSize: The minimum allowed binary tree leaf node size

[0074] In some example implementations of the QTBT partition structure, the CTU size can be set to 128×128 luma samples with two corresponding 64×64 chroma sample blocks (when example chroma subsampling is considered and used), MinQTSize can be set to 16×16, MaxBTSize can be set to 64×64, MinBTSize (for both width and height) can be set to 4×4, and MaxBTDepth can be set to 4. Quadtree partitioning can be first applied to the CTU to generate quadtree leaf nodes. Quadtree leaf nodes can have sizes from their minimum allowed size of 16×16 (i.e., MinQTSize) to 128×128 (i.e., the CTU size). If the node is 128×128, it will not be split by the binary tree first because the size exceeds the MaxBTSize (i.e., 64×64). Otherwise, nodes that do not exceed MaxBTSize can be partitioned by the binary tree. Fig. 9 In the example of , the basic block is 128×128. According to a predefined set of rules, the basic block can only be split by a quadtree. The basic block has a partition depth of 0. Each of the four resulting partitions is 64×64, not exceeding MaxBTSize, and can be further split by a quadtree or binary tree at level 1. The process continues. When the binary tree depth reaches MaxBTDepth (i.e., 4), further splitting can be ignored. When the binary tree node has a width equal to MinBTSize (i.e., 4), further horizontal splitting can be ignored. Similarly, when the binary tree node has a height equal to MinBTSize, further vertical splitting is not considered.

[0075] In some example embodiments, the above QTBT scheme can be configured to support the flexibility of having the same QTBT structure or independent QTBT structures for luma and chroma. For example, for P and B slices, the luma and chroma CTBs in one CTU can share the same QTBT structure. However, for I slices, the luma CTB can be partitioned into CBs by the QTBT structure, and the chroma CTB can be partitioned into chroma CBs by another QTBT structure. This means that a CU can be used to refer to different color channels in an I slice, for example, an I slice can consist of coding blocks of a luma component or coding blocks of two chroma components, and a CU in a P slice or a B slice can consist of coding blocks of all three color components.

[0076] The above various CB partitioning schemes and further partitioning of CB to PB can be combined in any manner.The following specific implementations are provided as non-limiting examples.

[0077] Inter prediction may be implemented, for example, in a single reference mode or a composite reference mode. In some embodiments, a skip flag may first be included in the codestream of the current block (or at a higher level) to indicate whether the current block is inter-coded and not skipped. If the current block is inter-coded, another flag may be further included in the codestream as a signal to indicate whether a single reference mode or a composite reference mode is used for prediction of the current block. For a single reference mode, one reference block may be used to generate a prediction block for the current block. For a composite reference mode, at least two reference blocks may be used to generate a prediction block (for example) by weighted averaging. At least one reference block may be identified using at least one reference frame index and additionally using at least one corresponding motion vector, which indicates at least one shift between at least one reference block and the current block in a position relative to the frame (for example, in horizontal and vertical pixels). For example, an inter-frame prediction block for a current block can be generated from a single reference block identified by a motion vector in a reference frame as a prediction block in a single reference mode, while for a composite reference mode, a prediction block can be generated by a weighted average of two reference blocks in two reference frames indicated by two reference frame indices and two corresponding motion vectors. At least one motion vector can be encoded in various ways and included in a code stream.

[0078] In some example embodiments, at least one reference picture list containing identifications of short-term and long-term reference frames for inter prediction may be formed based on information in a reference picture set (RPS). For example, a single picture reference list may be formed for unidirectional inter prediction, denoted as L0 reference (or reference list 0), while two picture reference lists may be formed for bidirectional inter prediction, denoted as L0 (or reference list 0) and L1 (or reference list 1) for each of the two prediction directions. The reference frames included in the L0 and L1 lists may be ordered in various predetermined ways. The lengths of the L0 and L1 lists may be signaled in the video bitstream. When multiple references used to generate a prediction block by weighted averaging in a composite prediction mode are on the same side of the frame where the block to be predicted is located, the unidirectional inter prediction may be in a single reference mode or in a composite reference mode. Bidirectional inter prediction may be a composite mode only because bidirectional inter prediction involves at least two reference blocks.

[0079] In some embodiments, a merge mode (MM) for inter prediction may be implemented. Typically, for merge mode, at least one of the motion vectors of c or the motion vectors in the composite reference prediction may be derived from at least one other motion vector, rather than being calculated and signaled independently. For example, in an encoding system, at least one current motion vector for a current PB may be represented by at least one difference between at least one current motion vector and at least one other already encoded motion vector (referred to as a reference motion vector). Such at least one difference in at least one motion vector, rather than the entirety of at least one current motion vector, may be encoded and included in a bitstream, and may be linked to at least one reference motion vector. Correspondingly, in a decoding system, at least one motion vector corresponding to the current PB may be derived based on at least one decoded motion vector difference and at least one decoded reference motion vector linked thereto. As a specific form of general merge mode (MM) inter prediction, such inter prediction based on at least one motion vector difference may be referred to as merge mode with motion vector difference (MMVD). Therefore, general MM or specific MMVD may be implemented to improve coding efficiency by utilizing the correlation between motion vectors associated with different PBs. For example, adjacent PBs may have similar motion vectors, and thus MVD may be small and may be efficiently encoded. For another example, motion vectors may be correlated in time (between frames) for blocks of similar location / position in space.

[0080] In some example embodiments of the MMVD, a reference motion vector (RMV) or MV predictor candidate list for motion vector prediction may be formed for the block being predicted. The RMV candidate list may contain a predetermined number (e.g., 2) of MV predictor candidate blocks whose motion vectors may be used to predict the current motion vector. The RMV candidate blocks may include blocks selected from adjacent blocks and / or temporal blocks in the same frame (e.g., blocks located in the same position in a continuation or subsequent frame of the current frame). These options represent blocks that may have similar or identical motion vectors as the current block at a spatial or temporal position relative to the current block. The size of the MV predictor candidate list may be predetermined. For example, the list may contain at least two candidates. In order to be on the RMV candidate list, for example, the candidate block may need to have at least one reference frame that is the same as the current block, must exist (e.g., when the current block is close to the edge of the frame, a boundary check needs to be performed), and must have been encoded during the encoding process, and / or decoded during the decoding process. In some embodiments, if spatial neighboring blocks are available and the above conditions are met, the merge candidate list can be first filled with spatial neighboring blocks (scanned in a specific predefined order) and then filled with temporal blocks if space is still available in the list. For example, the neighboring RMV candidate blocks can be selected from the left block and the top block of the current block. The RMV predictor candidate list can be dynamically formed as a dynamic reference list (DRL) at various levels (sequence, picture, frame, slice, super block, etc.). The DRL can be signaled in the bitstream.

[0081] In some embodiments, the actual MV predictor candidate used as a reference motion vector for predicting the motion vector of the current block can be signaled. In the case where the RMV candidate list contains two candidates, a one-bit flag called a merge candidate flag can be used to indicate the selection of the reference merge candidate. For the current block predicted in composite mode, each of the multiple motion vectors predicted using the MV predictor can be associated with a reference motion vector from the merge candidate list. The encoder can determine which RMV candidate more closely predicts the MV of the current coding block and signal the selection as an index to the DRL.

[0082] In some example embodiments of MMVD, after an RMV candidate is selected and used as a basic motion vector predictor for a motion vector to be predicted, a motion vector difference (MVD or delta MV, which represents the difference between the motion vector to be predicted and the reference candidate motion vector) may be calculated in the encoding system. Such an MVD may include information representing the magnitude of the MV difference and the direction of the MV difference, both of which may be signaled in the bitstream in various ways.

[0083] In some example implementations of the MMVD, a distance index may be used to specify the magnitude information of the motion vector difference and indicate one of a set of predefined offsets representing a predefined motion vector difference from a starting point (reference motion vector). The MV offset according to the signaled index may then be added to the horizontal or vertical component of the starting (reference) motion vector. An example predefined relationship between the distance index and the predefined offset is specified in Table 1.

[0084] Table 1 – Example relationship between distance index and predefined MV offsets

[0085]

[0086]

[0087] In some example embodiments of the MMVD, a direction index may be further signaled and used to indicate the direction of the MVD relative to a reference motion vector. In some embodiments, the direction may be limited to either a horizontal direction or a vertical direction. An example 2-bit direction index is shown in Table 2. In the example of Table 2, the interpretation of the MVD may vary depending on the information of the start / reference MV. For example, when the start / reference MV corresponds to a unidirectional prediction block or to a bidirectional prediction block, where the two reference frame lists point to the same side of the current picture (i.e., the POCs of both reference pictures are greater than the POC of the current picture, or are less than the POC of the current picture), the symbol in Table 2 may specify the sign (direction) of the MV offset added to the start / reference MV. When the start / reference MV corresponds to a bidirectional prediction block, where two reference pictures are on different sides of the current picture (i.e., the POC of one reference picture is greater than the POC of the current picture, and the POC of the other reference picture is less than the POC of the current picture), and the difference between the reference POC in picture reference list 0 and the current frame is greater than the difference between the reference POC in picture reference list 1 and the current frame, the symbols in Table 2 may specify the sign of the MV offset added to the reference MV corresponding to the reference picture in picture reference list 0, and the sign of the offset of the MV corresponding to the reference picture in picture reference list 1 may have an opposite value (opposite sign of the offset). Otherwise, if the difference between the reference POC in picture reference list 1 and the current frame is greater than the difference between the reference POC in picture reference list 0 and the current frame, the symbols in Table 2 may specify the sign of the MV offset added to the reference MV associated with picture reference list 1, and the sign of the offset of the reference MV associated with picture reference list 0 has an opposite value.

[0088] Table 2 - Example implementation of the sign of the MV offset specified by the direction index

[0089]

[0090]

[0091] In some example embodiments, the MVD may be scaled according to the difference in POC in each direction. If the difference in POC in both lists is the same, no scaling is required. Otherwise, if the difference in POC in reference list 0 is greater than the difference in POC in reference list 1, the MVD of reference list 1 is scaled. If the POC difference of reference list 1 is greater than list 0, the MVD of list 0 may be scaled in the same manner. If the starting MV is unidirectionally predicted, the MVD is added to the available or reference MV.

[0092] In some example embodiments of MVD encoding and signaling for bidirectional composite prediction, in addition to or as an alternative to separately encoding and signaling two MVDs, symmetric MVD encoding can be implemented so that only one MVD needs to be signaled, while the other MVD can be derived from the signaled MVD. In such embodiments, motion information including reference picture indices of list-0 and list-1 are not all signaled. Specifically, at the slice level, a flag called "mvd_l1_zero_flag" can be included in the bitstream to indicate whether reference list-1 is not signaled in the bitstream. If the flag is 1, indicating that reference list-1 is equal to zero (and therefore not signaled), the bidirectional prediction flag (called "BiDirPredFlag") can be set to 0, meaning that there is no bidirectional prediction. Otherwise, if mvd_l1_zero_flag is zero, if the nearest reference picture in list-0 and the nearest reference picture in list-1 form a front-to-back pair of reference pictures or a back-to-front pair of reference pictures, BiDirPredFlag may be set to 1, and both list-0 and list-1 reference pictures are short-term reference pictures. Otherwise, BiDirPredFlag is set to 0. BiDirPredFlag of 1 may indicate that a symmetric mode flag is additionally signaled in the bitstream. When BiDirPredFlag is 1, the decoder may extract the symmetric mode flag from the bitstream. For example, a symmetric mode flag may be signaled at the CU level (if necessary), and it may indicate whether a symmetric MVD coding mode is being used for the corresponding CU. When the symmetric mode flag is 1, it indicates the use of the symmetric MVD coding mode, and only the reference picture indexes of list-0 and list-1 (referred to as "mvp_l0_flag" and "mvp_l1_flag") are signaled with the MVD associated with list-0 (referred to as "MVD0"), and the other motion vector difference "MVD1" will be derived instead of signaled. For example, MVD1 can be derived as -MVD0. In this way, only one MVD is signaled in the example symmetric MVD mode.

[0093] In some other example implementations for MV prediction, a coordination scheme may be used to implement the general merge mode MMVD and some other types of MV prediction for single reference mode and composite reference mode MV prediction. Various syntax elements may be used to signal the manner in which the MV of the current block is predicted. For example, for a single reference mode, the following MV prediction modes may be signaled:

[0094] NEARMV - uses one of the motion vector predictors (MVP) in the list indicated by the DRL (Dynamic Reference List) index.

[0095] NEWMV—Uses one of the motion vector predictors (MVPs) in the list signaled by the DRL index as a reference and applies the delta to that MVP.

[0096] GLOBALMV – Use motion vectors based on frame-level global motion parameters.

[0097] Likewise, for the composite reference inter prediction mode using two reference frames corresponding to the two MVs to be predicted, the following MV prediction modes may be signaled:

[0098] NEAR_NEARMV—Use one of the motion vector predictors (MVP) in the list signaled by the DRL index.

[0099] NEAR_NEWMV—Uses one of the motion vector predictors (MVPs) in the list signaled by the DRL index as a reference and sends a delta MV of the second MV.

[0100] NEW_NEARMV—Uses one of the motion vector predictors (MVPs) in the list signaled by the DRL index as a reference and sends a delta MV of the first MV.

[0101] NEW_NEWMV—Uses one of the motion vector predictors (MVPs) in the list signaled by the DRL index as a reference and sends a delta MV of the two MVs.

[0102] GLOBAL_GLOBALMV – Use the MV from each reference based on its frame-level global motion parameters.

[0103] The term "NEAR" above refers to MV prediction using a reference MV as a general merge mode in the absence of MVD, while the term "NEW" refers to MV prediction involving the use of a reference MV and the motion vector difference (MVD) signaled as in MMVD mode to offset it. For composite inter prediction, the above reference basic motion vector and motion vector increment may generally be different or independent between the two references, even though they may be correlated, and this correlation may be exploited to reduce the amount of information required to signal the two motion vector increments. In this case, joint signaling of the two MVDs may be implemented and indicated in the bitstream.

[0104] The above dynamic reference list (DRL) can be used to store a set of indexed motion vectors that are dynamically maintained and considered as candidate motion vector predictors.

[0105] Motion Vector Differential Coding

[0106] In some example embodiments, in coding techniques such as AV1, fractional (such as 1 / 8 pixel (i.e., one eighth of a pixel)) motion vector precision (or accuracy) is allowed / supported, and the following syntax is used to signal the motion vector difference in reference frame list 0 (L0) or list 1 (L1).

[0107] mv_joint specifies which components of the motion vector difference are non-zero

[0108] ο0 indicates that there is no non-zero MVD in the horizontal or vertical direction

[0109] ο1 indicates that there is non-zero MVD only along the horizontal direction

[0110] ο2 indicates that there is non-zero MVD only in the vertical direction

[0111] o3 indicates that there is non-zero MVD in both horizontal and vertical directions

[0112] mv_sign specifies whether the motion vector difference is positive or negative

[0113] mv_class specifies the class of the motion vector difference. As shown in Table 3, a higher class means that the motion vector difference has a larger magnitude.

[0114] Table 3: Magnitude classes of motion vector differences

[0115] Music Videos MVD Magnitude MV_CLASS_0 (0，2] MV_CLASS_1 (2，4] MV_CLASS_2 (4，8] MV_CLASS_3 (8，16] MV_CLASS_4 (16，32] MV_CLASS_5 (32，64] MV_CLASS_6 (64，128] MV_CLASS_7 (128，256] MV_CLASS_8 (256，512] MV_CLASS_9 (512，1024] MV_CLASS_10 (1024，2048]

[0116] mv_bit specifies the integer part of the offset between the motion vector difference and the starting amplitude for each MV class

[0117] mv_fr specifies the first 2 fractional bits of the motion vector difference

[0118] mv_hp specifies the third fractional bit of the motion vector difference

[0119] Adaptive MVD resolution

[0120] In some example embodiments, the resolution of the MVD in various MVD amplitude classes can be distinguished. For example, a high resolution MVD for a large MVD amplitude of a higher MVD class may not provide a statistically significant improvement in compression efficiency. Thus, for a larger MVD amplitude range corresponding to a higher MVD amplitude class, the MVD can be encoded with a reduced resolution (integer pixel resolution or fractional pixel resolution). Similarly, typically for larger MVD values, the MVD can be encoded with a reduced resolution (integer pixel resolution or fractional pixel resolution). This MVD resolution that depends on the MVD class or depends on the MVD amplitude can generally be referred to as an adaptive MVD resolution.

[0121] Using adaptive MVD resolution, the number of signaling bits reduced by targeting a less accurate MVD may be greater than the additional bits required to encode the inter-frame prediction residual due to such less accurate MVD, due to the statistical observation that processing a MVD resolution of a large amplitude or high class MVD at a level similar to the resolution of a low amplitude or low class MVD in a non-adaptive manner may not significantly increase the inter-frame prediction residual coding efficiency of blocks with a large amplitude or high class MVD. In other words, for a large amplitude or high class MVD, using a higher MVD resolution may not produce more coding gain than using a lower MVD resolution.

[0122] In some example embodiments, further constraints may be imposed on the composite reference modes, such as the NEW_NEARMV and NEAR_NEWMV modes described above. Specifically, the accuracy of the motion vector difference (MVD) depends on the associated class and magnitude of the MVD.

[0123] In some example embodiments, fractional MVD is allowed only when the MVD magnitude is equal to or less than one pixel. Alternatively or additionally, only one MVD value is allowed when the value of the associated MV class is equal to or greater than MV_CLASS_1, and the MVD values ​​in each MV class are derived as 4, 8, 16, 32, 64 for MV class 1 (MV_CLASS_1), 2 (MV_CLASS_2), 3 (MV_CLASS_3), 4 (MV_CLASS_4), or 5 (MV_CLASS_5), respectively.

[0124] Exemplarily, the allowed MVD values ​​in each MV class are illustrated in Table 4.

[0125] Table 4: Adaptive MVD in each MV amplitude class

[0126]

[0127]

[0128] Additionally, if the current block is coded in NEW_NEARMV or NEAR_NEWMV mode, one context is used to signal mv_joint or mv_class. Otherwise, a different context is used to signal mv_joint or mv_class. Note that in AV1, mv_class specifies the class of the motion vector difference. A higher class means that the motion vector difference represents a larger update; mv_joint specifies which components of the motion vector difference are non-zero.

[0129] Improvements for adaptive MVD resolution

[0130] In some example embodiments, further improvements can be implemented for adaptive MVD. A new inter-frame coding mode called AMVDMV can be added to the single reference case. When the AMVDMV mode is selected and / or marked, it indicates that AMVD is applied to signal MVD, thereby adopting adaptive MVD resolution.

[0131] In one solution, a flag named amvd_flag is added in JOINT_NEWMV mode to indicate whether AMVD is applied in joint MVD coding mode. When adaptive MVD resolution is applied in joint MVD coding mode (which can also be named joint AMVD coding mode), the MVD of two reference frames is jointly signaled, and the accuracy of MVD is implicitly determined by, for example, MVD amplitude. Otherwise, the MVD of two (or more than two) reference frames is jointly signaled, and traditional MVD coding is applied.

[0132] Alternatively, the MVD of two (or more than two) reference frames can be jointly signaled and conventional MVD coding is applied. In this case, instead of adding amvd_flag as discussed above, a new inter-frame prediction mode called JOINT_AMVDNEWMV is added to indicate that AMVD is applied in the joint MVD coding mode.

[0133] Adaptive Motion Vector Resolution (AMVR)

[0134] In some example embodiments, AMVR can be implemented in various coding techniques such as AV1. For example, a total of 7 MV precisions are supported (e.g., 8, 4, 2, 1, 1 / 2, 1 / 4, 1 / 8). For each prediction block, the encoder (e.g., AVM, AV1 encoder) searches all supported precision values ​​and signals the best precision to the decoder.

[0135] In order to reduce the complexity of the encoder runtime, two precision sets are supported. Each precision set can contain, for example, 4 predefined precisions. One of the precision sets is adaptively selected at the frame level based on the maximum precision value of the frame. Exemplarily, the maximum precision can be signaled in the frame header. Table 5 summarizes the supported precision values ​​based on the maximum precision at the frame level.

[0136] Table 5: MV accuracy supported in two sets

[0137] Maximum frame-level accuracy Supported MV accuracy 1 / 8 1 / 8、1 / 2、1、4 1 / 4 1 / 4、1、4、8

[0138] In some example embodiments, there is a frame-level flag to indicate whether the MV of the frame contains sub-pixel (i.e., sub-pixel) precision. AMVR is enabled only when the value of the cur_frame_force_integer_mv flag is 0. Under AMVR, if the precision of the block is lower than the maximum precision, the motion model and interpolation filter are not signaled. If the precision of the block is lower than the maximum precision, the motion mode can be inferred to be translational motion, and the interpolation filter is inferred to be a REGULAR interpolation filter. Similarly, if the precision of the block is 4 pixels or 8 pixels, the inter-intra mode is not signaled and is inferred to be 0.

[0139] Joint MVD coding (JMVD)

[0140] In some example embodiments, in a coding technique such as AV1, an inter-coding mode named JOINT_NEWMV is applied to indicate whether to jointly signal the MVDs of two reference lists. If the inter-prediction mode is equal to JOINT_NEWMV mode, the MVDs of reference list 0 and reference list 1 are jointly signaled. In this case, only one MVD (named joint_mvd) is signaled and transmitted to the decoder, and the delta MVs of reference list 0 and reference list 1 are derived from joint_mvd.

[0141] In some example embodiments, the JOINT_NEWMV mode is signaled together with the NEAR_NEARMV, NEAR_NEWMV, NEW_NEARMV, NEW_NEWMV and GLOBAL_GLOBALMV modes. No additional context needs to be added.

[0142] When JOINT_NEWMV mode is signaled, and the picture order count (POC) distances between two reference frames and the current frame are different, the MVD is scaled for reference list 0 or reference list 1 based on the POC distance. Specifically, the distance between reference frame list 0 and the current frame is td0, and the distance between reference frame list 1 and the current frame is td1. If td0 is equal to or greater than td1, joint_mvd is the jointly signaled MVD and is used directly for reference list 0, and the mvd of reference list 1 is derived from joint_mvd based on equation (1):

[0143]

[0144] Otherwise, if td1 is equal to or greater than td0, joint_mvd is used directly for reference list 1, and mvd for reference list 0 is derived from joint_mvd based on equation (2):

[0145]

[0146] Improved joint MVD coding

[0147] In some example embodiments, in a coding technique such as AV1, if a block is coded as a joint MVD coding mode (e.g., JOINT_NEWMV or JOINT_AMVDNEWMV), a new syntax named mvd_scaling_factor_idx is signaled into the codestream to explicitly indicate the scaling factor of the MVD between reference frame 0 and reference frame 1.

[0148] Exemplarily, as shown in Tables 6 and 7, two predefined lookup tables can be used to store the supported / allowed scaling factors for JOINT_NEWMV or JOINT_AMVDNEWMV, respectively. The associated entry index of the selected scaling factor in the lookup table is signaled in the bitstream. For the JOINT_AMVDNEWMV mode, the same scaling factor is applied to the vertical and horizontal components of the MVD of the reference frame list 0 and / or 1. For the JOINT_NEWMV mode, the scaling factor of one component of the MVD (vertical component or horizontal component) is limited to 1, and the scaling factor of the other component of the MVD can be other values, such as 2 or 1 / 2. In one example, the MVD of the reference frame lists 0 and 1 is calculated in the following equation:

[0149] mvd_ref0=joint_mvd (3)

[0150]

[0151] Here, mvd_ref0 and mvd_ref1 represent the MVD of reference frame list 1 and the MVD of reference frame list 2, respectively. The distance between reference frame list 0 and the current frame is td0, and the distance between reference frame list 1 and the current frame is td1; joint_mvd represents the jointly signaled MVD; and jmvd_scale represents the scaling factor.

[0152] Table 6: Scaling factors for JOINT_AMVDNEWMV

[0153] index Scaling factors for the x-axis and y-axis 0 1 1 2 2 1 / 2

[0154] Table 7: Scaling factors for JOINT_NEWMV

[0155] index Scaling factor for the x-axis Scaling factor for the y-axis 0 1 1 1 1 2 2 2 1 3 1 1 / 2 4 1 / 2 1

[0156] Bidirectional prediction with CU-level weights (BCW)

[0157] In some example embodiments, in video coding techniques such as HEVC, a bidirectional prediction signal is generated by averaging two prediction signals obtained from two different reference pictures and / or using two different motion vectors. In VVC, the bidirectional prediction mode is extended beyond simple averaging to allow for a weighted average of the two prediction signals. For example, denoted as P 双向预测 The prediction using bidirectional can be calculated by using the following equation 5:

[0158] P 双向预测 =((8-w)*P0+w*P1+4)>>3 (5)

[0159] Exemplarily, five weights are allowed in weighted average bidirectional prediction, w∈{-2,3,4,5,10}. When w is equal to 4, the weighted average of the two prediction samples is performed using equal weighting factors. For each bidirectional prediction CU, the weight w is determined in one of two ways: 1) For non-merged CUs, the weight index is signaled after the motion vector difference; 2) For merged CUs, the weight index is inferred from neighboring blocks based on the merge candidate index.

[0160] In some example embodiments, BCW is only applied to CUs with 256 or more luma samples (i.e., CU width multiplied by CU height is greater than or equal to 256). For low-latency pictures, all 5 weights are used. For non-low-latency pictures, only 3 weights (w∈{3,4,5}) are used.

[0161] Local Illumination Compensation (LIC)

[0162] LIC is a video coding tool that can be utilized by video encoders and video decoders. In some example embodiments, LIC can be applied based on a linear model for compensating for illumination changes between at least one temporal reference picture and the current picture (e.g., in a motion compensation stage). The linear model is based on LIC parameters including a scaling factor α and an offset β, and is described in more detail in the block adaptive weighted prediction section below. LIC can be enabled or disabled via, for example, high-level signaling at various levels.

[0163] In some example embodiments, a bidirectional prediction reference template may be generated for a template sample associated with a current block. The reference template sample may be identified based on at least one motion vector associated with the current block. For example, the reference template sample may include a neighboring temporal reference CU of the current CU and may correspond to a template sample of the current CU. The reference template sample may be jointly considered (e.g., averaged) in LIC parameter derivation.

[0164] In some example embodiments, a minimum mean square error (LMSE) algorithm may be applied to derive the LIC parameters. For example, a LMSE-based calculation may be performed to determine the LIC parameters so that the difference between the bidirectional prediction reference template reference samples and the template samples of the current CU may be minimized.

[0165] In some example embodiments, a similar approach may be used in unidirectional prediction. In this case, the LIC parameters may be determined so that the difference between the unidirectional prediction reference template reference sample and the template sample of the current CU may be minimized.

[0166] Note that the LMSE algorithm described herein is only an example of deriving LIC parameters. One or more other approaches / algorithms may be used.

[0167] Block Adaptive Weighted Prediction (BAWP)

[0168] In some example embodiments, BAWP is employed to simulate local illumination variations.

[0169] refer to Fig.12 For example, BAWP can be a block-level weighted prediction to model the local illumination variation between the current block and its predicted block as a function of the local illumination variation between the current block template (or the causal sample of the current block) and the reference block template. Fig.12, a template of a current block (1212) (or referred to as current template 1210) and a template of a reference block (1222) (or referred to as reference template 1220) are illustrated in FIG. The reference block may be indicated or determined by a motion vector (MV, 1230). The current block may be in a current picture (or current frame), and the reference block may be in a reference picture (or reference frame). In some embodiments, the function may be a linear function. The parameters of the function may be represented by a scaling factor α and an offset β, which form a linear equation. The scaling factor may also be referred to as a ratio, an α factor, or an α value.

[0170] When encoding a block in BAWP mode, an exemplary linear function for compensating for illumination changes is listed below:

[0171] p′(x′)=α*p(x)+β (6)

[0172] Where: p′(x′) is the prediction sample at position x′ in the current block (or the prediction sample in the prediction unit (PU) in the current block), p(x) is the sample at position x in the reference block corresponding to p′(x′), α is a scaling factor (or ratio), and β is an offset value. Note that the reference block can be identified or derived from the MV associated with the current block, and p(x) is the reference sample pointed to by the MV at position x on the reference picture. Note that in Equation 6, the reference sample and the prediction sample can have the same coordinates (i, j) in their respective blocks (i.e., the reference block and the current block, or the reference block and the prediction unit). Alternatively, the coordinates of the reference sample in the reference block can be based on the coordinates of the prediction sample in the current block. For example, the coordinates of the prediction sample can be adjusted by a delta value to obtain the coordinates of the corresponding reference sample (in the reference picture). In some example embodiments, p′(x′) and p(x) can be referred to as being in the same position - p(x) is the reference sample at position x in the reference block, corresponding to p′(x′) at position x′ in the current block. In some example embodiments, the correspondence between p'(x') and p(x) may be established by motion information (such as at least one motion vector).

[0173] In some example embodiments, α and β may be derived based on the current block template and the reference block template, and therefore, α and β do not require signaling overhead except for signaling a BAWP flag (e.g., bawp_flag) for a single inter prediction mode to indicate the use of BAWP. In some example embodiments, the BAWP method is only applied to blocks having a size greater than or equal to 8×8 and encoded in a single inter prediction mode. In some example embodiments, the BAWP method is only applied to the luma component.

[0174] Although deriving both the scaling factor and the offset (α and β) will save some signaling overhead, there may be some potential disadvantages during certain situations. For example, the effectiveness and / or accuracy of the scaling factor depends on the similarity between the current block and its template in the reference frame. When the correlation between the current block and its template in the reference frame is high, the derived scaling factor can significantly improve the prediction accuracy. However, if the current block and its template in the reference frame are significantly different, the scaling factor may be inaccurate and even useless, and the prediction accuracy may deteriorate.

[0175] In the present application, various embodiments for improving video encoding / decoding techniques in BAWP and / or LIC modes are disclosed, with the goal of enhancing prediction accuracy with minimal overhead in signaling cost. In particular, various methods for signaling and / or deriving scaling factors and offsets (α and β) as specified in Equation 6 are described.

[0176] Based on surveys and statistical observations, high-precision, high-accuracy scaling factors can help improve codec efficiency and increase codec gain. High precision is particularly advantageous when the magnitude of the scaling factor is small. Therefore, rather than deriving the scaling factor at the decoder end, it may be more advantageous to signal the scaling factor in the video bitstream. In addition, when the decoder stores supported (candidate) scaling factors, sorting them in a specific way can help improve entropy codec efficiency. In the present application, various embodiments for achieving these goals are described below.

[0177] In this application, the term block may refer to a transform block, a coded block, a prediction block, a coding block, a coding unit (CU), etc. The term chroma block may refer to a block in any chroma (color) channel. The direction of a reference frame is determined by whether the reference frame precedes the current frame in the display order or follows the current frame in the display order.

[0178] In this application, a sample may be interpreted as the pixel value of a pixel. The sample may generally refer to any component (luminance or chrominance).

[0179] In this application, the terms x-axis and y-axis refer to the horizontal and vertical components of a two-dimensional value. The x-axis and y-axis can also be replaced by two other axes, which are along two mutually perpendicular predefined directions, and the same embodiments are applicable. That is, the x-axis and y-axis can be rotated by a certain angle. For example, the x-axis and y-axis can be replaced by a 45-degree axis and a 135-degree axis.

[0180] In this application, conventional JMVD may refer to JMVD with conventional full MV resolution or JMVD with AMVR.

[0181] In the present application, unless otherwise specified, signaling may include one or more sub-signals, and one or more sub-signals may be transmitted together or separately.

[0182] For the embodiments described below, the coding block or the coded block may be coded in BAWP (or LIC, or composite weighted prediction (CWP)) mode, which is referred to as BAWP for simplicity of description. These embodiments may be implemented in a decoder and / or an encoder.

[0183] In one embodiment, when a current block is predicted from a reference block of the current block using a linear function with a scaling factor and an offset β (such as linear equation 6 shown above), the selection of the scaling factor and / or offset β can be signaled into the bitstream and parsed at the decoder to reconstruct the predicted block. The reference block can be specified by, for example, a motion vector associated with the current block. That is, the scaling factor and / or offset β can be explicitly signaled rather than derived by the decoder. In some example embodiments, only the scaling factor is signaled, and the offset β can be derived based on the scaling factor, or vice versa. In the present application, the scaling factor may also be referred to as a ratio, a scaling factor, a scaling factor α, or an α factor.

[0184] In one embodiment, all supported values ​​of the scaling factor may be stored in a predefined lookup table, and the index of the scaling factor in the lookup table may be signaled in the bitstream and parsed at the decoder end. In this case, by signaling the index of the lookup table, the signaling explicitly indicates or identifies the scaling factor.

[0185] In one embodiment, the support values ​​in the predefined lookup table are symmetrically distributed along a single threshold (TH). As an example, the support values ​​stored in the lookup table may be [TH–d0, TH–d1, TH–d2, … TH, …, TH+d2, TH+d1, TH+d0], where TH, d0, d1, and d2 are natural numbers. Exemplarily, TH=1, d0=0.1, d1=0.2, d2=0.3. In another example, TH itself is not included in the predefined lookup table (the values ​​in the lookup table are still symmetrically distributed along TH).

[0186] In some example embodiments, the value of TH is signaled in high-level signaling (HLS), which syntax may be signaled via at least one of the following levels: sequence parameter set (SPS) level, picture parameter set (SPS) level, picture level, slice level, tile level, coding tree unit (CTU) level. For example, the signaling may be carried in headers corresponding to these levels, such as CTU headers.

[0187] In some example embodiments, TH may be set to 0 or 1.

[0188] In one embodiment, the order of the numbers (scaling factors) in the lookup table may depend on the magnitude of each scaling factor, rather than the symmetrical distribution described above, so that those scaling factors with smaller values ​​have smaller indices. In other words, the lookup table may be sorted based on the magnitude of the scaling factors.

[0189] In one example, the order of the numbers in the lookup table may depend on the absolute difference between the magnitude of the scaling factor and TH. This difference may be referred to as the distance between the scaling factor and TH.

[0190] In one embodiment, in order to improve coding efficiency and increase coding gain, the context of the index or value of the scaling factor and / or the index or value of the offset (β) value used for entropy coding / decoding (signaling) may depend on decoded information associated with the current block and / or decoded information associated with the neighboring blocks, including but not limited to: block size; inter-frame prediction mode; reference frame of the current block; the distance between the reference frame associated with the reference block and the current frame to which the current block belongs; the temporal level of the current frame in the group of pictures (GOP) structure; the temporal level of the reference frame in the GOP structure; an index identifying a scaling factor stored in one of the at least two lookup tables, the scaling factor being used to decode the neighboring blocks of the current block; the value of the scaling factor used to decode the neighboring blocks of the current block, and the like.

[0191] In one embodiment, multiple predefined lookup tables can be supported, and the decoder can be configured and can maintain multiple predefined lookup tables. The selection of a specific lookup table for each block can be implicitly determined / derived based on decoded information associated with the current block and / or decoded information associated with neighboring blocks, including but not limited to: block size; inter-frame prediction mode; reference frame of the current block; distance between the reference frame associated with the reference block and the current frame to which the current block belongs; temporal level of the current frame in the GOP structure; temporal level of the reference frame in the GOP structure; index, the index identifies a scaling factor stored in one of the at least two lookup tables, the scaling factor used to decode the neighboring blocks of the current block; the value of the scaling factor used to decode the neighboring blocks of the current block, etc.

[0192] In one embodiment, multiple predefined lookup tables are supported, and the selection of the lookup table to use for each block is explicitly signaled into the bitstream and parsed at the decoder end.

[0193] In one embodiment, the context for signaling an index of a lookup table may depend on decoded information associated with the current block and / or decoded information associated with a neighboring block, including but not limited to: block size; inter-frame prediction mode; reference frame of the current block; the distance between the reference frame associated with the reference block and the current frame to which the current block belongs; the temporal level of the current frame in the GOP structure; the temporal level of the reference frame in the GOP structure; an index identifying a scaling factor stored in one of the at least two lookup tables, the scaling factor being used to decode a neighboring block of the current block; the value of the scaling factor used to decode a neighboring block of the current block, and the like.

[0194] In one embodiment, the scaling factors may not be stored directly, but instead the differences between the amplitudes of all supported scaling factors and TH (the difference is called the scaling factor difference) may be stored in a predefined lookup table, and the index of the scaling factor difference in the lookup table may be signaled in the bitstream and parsed at the decoder end.

[0195] In some example embodiments, the values ​​or magnitudes of the scaling factor differences stored in the predefined lookup table are symmetrically distributed along a single threshold TH (such as 0).

[0196] In some example embodiments, the threshold TH may be predefined or signaled in the video stream.

[0197] In some example embodiments, the decoder may derive a scaling factor α (or a quantized value of the scaling factor α), and the derived scaling factor α may be used as a basis for determining a final more accurate scaling factor α. In this case, TH may be set to the derived scaling factor α (or a quantized value of the scaling factor α), and the derived scaling factor α may be calculated based on, for example, a local illumination change between a template of the current block (or a causal sample of the current block) and a template of a reference block.

[0198] In some example embodiments, once a new TH value is derived as described above, the lookup table may be updated and reordered based on the new TH value.

[0199] In some example implementations, zero is not included in the predefined lookup table.

[0200] In some example embodiments, the value of TH is signaled in high-level signaling (HLS), which syntax may be signaled via at least one of the following levels: sequence parameter set (SPS) level, picture parameter set (SPS) level, picture level, slice level, tile level, coding tree unit (CTU) level. For example, the signaling may be carried in headers corresponding to these levels, such as CTU headers.

[0201] In some example embodiments, TH may be set to 0 or 1.

[0202] In one embodiment, the order of the scaling factor differences in the lookup table may depend on the magnitude of each scaling factor difference, rather than the symmetrical distribution described above, so that those scaling factor differences with smaller values ​​have smaller indices. In other words, the lookup table may be sorted based on the magnitude of the scaling factor differences.

[0203] In one example, the order of the numbers (ie, scaling factor differences) in the lookup table may depend on the absolute difference between the magnitude of the scaling factor and TH. This difference may be referred to as the distance between the scaling factor and TH.

[0204] In one embodiment, the offset value β may be derived from a linear equation between the reference block and the current block.

[0205] In some example embodiments, the offset value β may be set to (cur_template_mean−α*ref_template_mean), where cur_template_mean is the mean of samples in the template of the current block, and ref_template_mean is the mean of samples in the template of the reference block.

[0206] In one embodiment, one of the scaling factor α or the offset β may be derived from neighboring reconstructed samples of the current block and neighboring reconstructed samples of the reference block, and the other is signaled in the codestream.

[0207] In one embodiment, the precision (eg, accuracy or step size) of the scaling factor α and the offset β may be different. In another embodiment, the scaling factor α and the offset β may have the same precision.

[0208] In some example embodiments, since the offset β is derived, it may have higher precision. On the other hand, given the constraints of signaling overhead, such as the number of bits allocated to signaling, the scaling factor may have lower precision to cover a larger range. With the same number of signaling bits, lower precision can accommodate a larger range.

[0209] In one embodiment, the prediction samples of the current block are obtained by subtracting the mean of the corresponding reference block from the reference samples, multiplying the result by a scaling factor α signaled for the block, and adding an offset value β.

[0210] For example, the prediction process can be expressed by the following equation 7:

[0211] Cur pred =α*(ref sample -ref mean )+Offset(7)

[0212] Where ref_sample is the reference sample (in the reference block) corresponding to the sample to be predicted in the current block, ref_mean is the mean (or average) value of the reference block, Cur pred is the prediction result of the sample to be predicted in the current block.

[0213] In some example embodiments, the offset value β in Equation 7 may be set to a mean (or average) value of the reference block.

[0214] In one embodiment, the scaling factor (the value of the scaling factor, or the index identifying the scaling factor in the lookup table) may be signaled into the codestream, and the offset β (the value of the offset β, or the index identifying the offset β in the lookup table) may be signaled or derived. In addition, whether to signal or derive β may be determined by, for example and not limited to, the current block coding mode, the adjacent block coding mode, the number of adjacent blocks encoded in the BAWP mode, an explicitly signaled flag, etc.

[0215] In the present application, signaling (e.g., syntax elements) may indicate values ​​such as scaling factors and / or offsets β in an explicit or implicit manner. Explicit indication may be by sending an index to a lookup table to look up the value, or by sending the value directly. When the value is sent implicitly, the decoder may need to perform further derivation based on the signaled syntax element. In the case of implicit indication, the syntax element may also be referred to as being "associated" with the value to be derived.

[0216] The various embodiments and / or implementations described in this application may be performed individually or in combination in any order. In addition, each of the method (or embodiment), encoder, and decoder may be implemented by a processing circuit (e.g., one or more processors or one or more integrated circuits). One or more processors execute a program stored in a non-volatile computer-readable medium. In this application, the term block may be interpreted as a prediction block, a coding block, or a coding unit (CU).

[0217] Fig.13A flowchart 1300 of an exemplary method is shown, which follows the basic principles of the above-mentioned embodiments for indicating scaling factors and / or offset values. The exemplary decoding method flow may include some or all of the following steps: S1310, receiving a video bitstream, the video bitstream comprising a current block and a reference block, the reference block being used to predict the current block and identified by a motion vector associated with the current block; S1320, determining from the video bitstream a first syntax element indicating a scaling factor (α), the scaling factor being stored in a first lookup table of at least two lookup tables, the at least two lookup tables being maintained by a decoder and being used to store a plurality of candidate scaling factors or a plurality of candidate scaling factor differences, the plurality of candidate scaling factor differences being differences between the plurality of candidate scaling factors and a threshold; S1330, determining the first lookup table storing the scaling factor; S1340, determining the scaling factor α based on the value of the first syntax element and the first lookup table; S1350, predicting the current block based on the reference block, the scaling factor α and the offset; and S1360, reconstructing the current block based on the predicted current block.

[0218] In any portion or combination of the above embodiments, the current block may be located in a current frame, and the reference block may be located in a reference frame.

[0219] In any part or combination of the above embodiments, the scaling factor may be a coefficient of a linear model p′(x′)=α*p(x)+β, where p′(x′) is a sample at position x′ in the current block, and p(x) is a reference sample corresponding to p′(x′) and located at position x in the reference block. p(x) may also be a change or adjustment of the reference sample, and β is an offset.

[0220] In any part or combination of the above embodiments, the variation of the reference sample is obtained by subtracting a mean value of the reference block from the reference sample; and the embodiments may further include determining the offset as the mean value of the reference block.

[0221] In any portion or combination of the above embodiments, the lookup table storing the scaling factor may be explicitly signaled (eg, as an index to the lookup table or the value of the scaling factor), or implicitly signaled (the scaling factor is derived using a signaled syntax element).

[0222] In the present application, the direction of the reference frame may be determined by whether the reference frame is before the current frame in the display order or after the current frame in the display order.

[0223] The above operations can be combined or arranged in any amount or order as needed. At least two steps and / or operations can be performed in parallel. The embodiments and implementation methods in this application can be used alone or in combination in any order. The steps in an embodiment / method can be divided to form multiple sub-methods, each of which can be independent of other steps in the embodiment and can form an independent solution. In addition, each of the method (or embodiment), encoder and decoder can be implemented by a processing circuit (e.g., at least one processor or at least one integrated circuit). In one example, at least one processor executes a program stored in a non-volatile computer-readable medium. The embodiments in this application can be applied to luminance blocks or chrominance blocks. The term block can be interpreted as a prediction block, a coding block or a coding unit, i.e., a CU. The term block can also be used here to refer to a transform block. In the following items, when the block size is said, it can refer to the block width or height, or the maximum value of the width and height, or the minimum value of the width and height, or the area size (width*height), or the aspect ratio of the block (width:height, or height:width).

[0224] The above techniques may be implemented as computer software via computer-readable instructions and physically stored in at least one computer-readable storage medium. Fig.14 A computer system (1800) is shown that is suitable for implementing certain embodiments of the disclosed subject matter.

[0225] The computer software may be encoded in any suitable machine code or computer language, and may be assembled, compiled, linked, or the like to create a code comprising instructions, which may be directly executed by at least one computer central processing unit (CPU), graphics processing unit (GPU), or the like, or executed by decoding, microcode, or the like.

[0226] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablets, servers, smartphones, gaming devices, IoT devices, etc.

[0227] Fig.14 The components shown for the computer system (1800) are exemplary in nature and are not intended to limit the scope of use or functionality of computer software implementing the embodiments of the present application. The configuration of the components should not be interpreted as having any dependency or requirement on any component or combination of components shown in the exemplary embodiment of the computer system (1800).

[0228] The computer system (1800) may include certain human-computer interface input devices. The human-computer interface input devices may include at least one of the following (only one of which is depicted): a keyboard (1801), a mouse (1802), a touch pad (1803), a touch screen (1810), a data glove (not shown), a joystick (1805), a microphone (1806), a scanner (1807), and a camera (1808).

[0229] The computer system (1800) may also include certain human-computer interface output devices. Such human-computer interface output devices may stimulate at least one sense of a human user through, for example, tactile output, sound, light, and smell / taste. Such human-computer interface output devices may include tactile output devices (e.g., tactile feedback through a touch screen (1810), a data glove (not shown), or a joystick (1805), but there may also be tactile feedback devices that are not used as input devices), audio output devices (e.g., speakers (1809), headphones (not shown)), visual output devices (e.g., screens (1810) including cathode ray tube screens, liquid crystal screens, plasma screens, organic light emitting diode screens, each of which has or does not have a touch screen input function, each of which has or does not have a tactile feedback function - some of which may output two-dimensional visual output or output of more than three dimensions by means such as stereoscopic picture output; virtual reality glasses (not shown), holographic displays, and smoke boxes (not shown)) and printers (not shown).

[0230] The computer system (1800) may also include human-accessible storage devices and their associated media, such as optical media including high-density read-only / rewritable compact disks (CD / DVD ROM / RW) (1820) with CD / DVD or similar media (1821), thumb drives (1822), removable hard disk drives or solid state drives (1823), traditional magnetic media such as tapes and floppy disks (not shown), special-purpose ROM / ASIC / PLD-based devices such as security software protectors (not shown), and the like.

[0231] Those skilled in the art should also understand that the term "computer-readable storage media" used in connection with the disclosed subject matter does not include transmission media, carrier waves, or other transient signals.

[0232] The computer system (1800) may also include an interface (1854) to at least one communication network (1855). For example, the network may be wireless, wired, or optical. The network may also be a local area network, a wide area network, a metropolitan area network, an in-vehicle network, an industrial network, a real-time network, a delay-tolerant network, and the like. The network also includes local area networks such as Ethernet, wireless local area networks, cellular networks (GSM, 3G, 4G, 5G, LTE, etc.), television wired or wireless wide area digital networks (including cable television, satellite television, and terrestrial broadcast television), in-vehicle and industrial networks (including CANBus), and the like. Some networks typically require an external network interface adapter for connecting to some universal data port or peripheral bus (1849) (e.g., a USB port of the computer system (1800)); other systems are typically integrated into the core of the computer system (1800) by connecting to a system bus as described below (e.g., an Ethernet interface integrated into a PC computer system or a cellular network interface integrated into a smart phone computer system). By using any of these networks, the computer system (1800) can communicate with other entities. The communication can be one-way, for receiving only (e.g., wireless television), one-way for sending only (e.g., CAN bus to certain CAN bus devices), or two-way, such as to other computer systems via a local or wide area digital network. Each of the above networks and network interfaces can use certain protocols and protocol stacks.

[0233] The above-mentioned human-machine interface devices, human-accessible storage devices, and network interfaces may be connected to the core (1820) of the computer system (1800).

[0234] The core (1820) may include at least one central processing unit (CPU) (1821), a graphics processing unit (GPU) (1842), a dedicated programmable processing unit in the form of a field programmable gate array (FPGA) (1843), a hardware accelerator for a specific task (1844), a graphics adapter (1830), etc. These devices, as well as a read-only memory (ROM) (1845), a random access memory (1846), an internal mass storage (e.g., an internal non-user accessible hard disk drive, a solid state drive, etc.) (1847), etc., may be connected via a system bus (1848). In some computer systems, the system bus (1848) may be accessed in the form of at least one physical plug so that it may be expanded by additional central processing units, graphics processing units, etc. Peripheral devices may be directly attached to the system bus (1848) of the core, or connected via a peripheral bus (1849). In one example, a screen (1810) may be connected to a graphics adapter (1830). The architecture of the peripheral bus includes a peripheral controller interface PCI, a universal serial bus USB, etc.

[0235] The computer readable storage medium may have computer code thereon for performing various computer-implemented operations. The medium and computer code may be specially designed and constructed for the purpose of this application, or may be medium and code well known and available to those skilled in the art of computer software.

[0236] Although the present application has described a number of exemplary embodiments, various changes, arrangements and various equivalent substitutions of the embodiments are within the scope of the present application. Therefore, it should be understood that those skilled in the art can design a variety of systems and methods, which, although not explicitly shown or described herein, embody the principles of the present application and are therefore within the spirit and scope of the present application.

Claims

1. A method for processing video data in a decoder, characterized in that: The method comprises: Receiving a video bitstream, the video bitstream comprising a current block and a reference block, the reference block being used to predict the current block and being identified by a motion vector associated with the current block; Determine, from the video bitstream, a first syntax element indicating a scaling factor α, wherein the scaling factor is stored in a first lookup table of at least two lookup tables, wherein the at least two lookup tables are maintained by a decoder and are used to store a plurality of candidate scaling factors or a plurality of candidate scaling factor differences, wherein the plurality of candidate scaling factor differences refer to differences between the plurality of candidate scaling factors and a threshold; determining the first lookup table storing the scaling factor; determining the scaling factor based on a value of the first syntax element and the first lookup table; predicting the current block based on the reference block, the scaling factor and the offset; and, Based on the predicted current block, the current block is reconstructed.

2. The method according to claim 1, characterized in that The determining the first lookup table storing the scaling factor comprises: The first lookup table is determined based on decoded information associated with the current block or the reference block, wherein the decoded information includes at least one of the following: Block size; Inter prediction mode; A reference frame of the current block; a distance between a reference frame associated with the reference block and a current frame to which the current block belongs; The temporal level of the current frame in the group of pictures GOP structure; the temporal level of the reference frame in the GOP structure; An index identifying a scaling factor stored in one of the at least two lookup tables, the scaling factor being used to decode a neighboring block of the current block; or, The value of the scaling factor used to decode the neighboring blocks of the current block.

3. The method according to claim 1, characterized in that The determining the first lookup table storing the scaling factor comprises: Determining, from the video bitstream, a second syntax element indicating the first lookup table; Based on a value of the second syntax element, the first lookup table is determined.

4. The method according to claim 3, characterized in that The context for entropy encoding the second syntax element is based on decoded information associated with the current block or the reference block, wherein the decoded information includes at least one of the following: Block size; Inter prediction mode; A reference frame of the current block; a distance between a reference frame associated with the reference block and a current frame to which the current block belongs; The temporal level of the current frame in the group of pictures GOP structure; the temporal level of the reference frame in the GOP structure; An index identifying a scaling factor stored in one of the at least two lookup tables, the scaling factor being used to decode a neighboring block of the current block; or, The value of the scaling factor used to decode the neighboring blocks of the current block.

5. The method according to claim 1, characterized in that In each of the at least two lookup tables, the plurality of candidate scaling factor difference values ​​are sorted.

6. The method according to claim 5, characterized in that In each of the at least two lookup tables, the plurality of candidate scaling factor difference values ​​are symmetrically distributed along the threshold value based on a magnitude of each candidate scaling factor difference value.

7. The method according to claim 6, further comprising: deriving a predicted scaling factor based on a local illumination change between a template of the current block and a template of the reference block; The threshold is set as a scaling factor for the prediction.

8. The method according to claim 5, further comprising: Determine, from the video bitstream, a high-level syntax element indicating the threshold, wherein the high-level syntax element is signaled at at least one of the following levels: Sequence parameter set SPS level; Picture parameter set SPS level; Picture level; Stripe level; Tile level; Coding Tree Unit CTU level.

9. The method according to claim 5, characterized in that The threshold is predefined to include 0 or 1.

10. The method according to claim 5, characterized in that In each of the at least two lookup tables, the plurality of candidate scale factor difference values ​​are ordered based on a magnitude of each candidate scale factor difference value.

11. The method according to claim 5, characterized in that The at least two lookup tables do not include zero.

12. The method according to claim 1, further comprising: The offset is determined using the following formula: β=(cur_template_mean–α*ref_template_mean) Wherein, cur_template_mean is the mean of samples in the template of the current block, and ref_template_mean is the mean of samples in the template of the reference block.

13. The method according to claim 1, further comprising: The offset is derived from neighboring reconstructed samples of the current block and neighboring reconstructed samples of the reference block.

14. The method according to claim 1, characterized in that The precision of the offset is higher than the precision of the scaling factor.

15. The method according to claim 1, further comprising: Determine whether to derive the offset or to obtain the offset using a third syntax element carried in the video bitstream based on one of the following: Flags that explicitly signal this; Current block encoding mode; Adjacent block coding mode; The number of a plurality of neighboring blocks of the current block, wherein the plurality of neighboring blocks are encoded in a block adaptive weighted prediction (BAWP) mode; When it is determined to use the third syntax element to obtain the offset, the offset is determined based on a value of the third syntax element.

16. The method according to claim 1, characterized in that The current block is encoded using one of the following modes: a block adaptive weighted prediction (BAWP) mode; or a local illumination compensation (LIC) mode.

17. The method according to claim 1, characterized in that The first syntax element comprises an index identifying the scaling factor in the first lookup table; The scaling factor α is used as the slope of the linear equation, which is shown below: p′(x′)=α*P(x)+β Wherein, p′(x′) is the predicted sample at position x′ in the current block, p(x) is the reference sample corresponding to p′(x′) at position x in the reference block or the variance of the reference sample, and β is the offset; The predicting the current block based on the reference block, the scaling factor and the offset comprises: Based on the reference block and the linear equation, the current block is predicted.

18. The method according to claim 17, characterized in that Obtaining a variance of the reference sample by subtracting a mean of the reference block from the reference sample; The method further comprises: A mean value of the reference blocks is determined as the offset.

19. A device for processing video data, characterized in that: The device comprises a memory for storing computer instructions, and a processor in communication with the memory, wherein when the processor executes the computer instructions, the processor is configured to cause the device to: Receiving a video bitstream, the video bitstream comprising a current block and a reference block, the reference block being used to predict the current block and being identified by a motion vector associated with the current block; Determine, from the video bitstream, a first syntax element indicating a scaling factor α, wherein the scaling factor is stored in a first lookup table of at least two lookup tables, wherein the at least two lookup tables are maintained by a decoder and are used to store a plurality of candidate scaling factors or a plurality of candidate scaling factor differences, wherein the plurality of candidate scaling factor differences refer to differences between the plurality of candidate scaling factors and a threshold; determining the first lookup table storing the scaling factor; Determining the scaling factor α based on the value of the first syntax element and the first lookup table; Predicting the current block based on the reference block, the scaling factor α and the offset; and Based on the predicted current block, the current block is reconstructed.

20. A non-volatile storage medium, characterized in that: For storing computer readable instructions which, when executed by a processor, cause the processor to: Receiving a video bitstream, the video bitstream comprising a current block and a reference block, the reference block being used to predict the current block and being identified by a motion vector associated with the current block; Determine, from the video bitstream, a first syntax element indicating a scaling factor α, wherein the scaling factor is stored in a first lookup table of at least two lookup tables, wherein the at least two lookup tables are maintained by a decoder and are used to store a plurality of candidate scaling factors or a plurality of candidate scaling factor differences, wherein the plurality of candidate scaling factor differences refer to differences between the plurality of candidate scaling factors and a threshold; determining the first lookup table storing the scaling factor; Determining the scaling factor α based on the value of the first syntax element and the first lookup table; Predicting the current block based on the reference block, the scaling factor α and the offset; and, Based on the predicted current block, the current block is reconstructed.

Images