Extensions to block adaptive weighted prediction

Abstract

The present disclosure generally relates to video encoding / decoding, in particular to providing extensions to block adaptive weighted prediction (BAWP). A method includes receiving an encoded video bitstream; determining, based on syntax elements signaled in the encoded video bitstream, a prediction mode for predicting the current block based on the reference block, where the prediction mode comprises a linear equation; deriving a scale factor for the current block from at least one of: a plurality of scale factors of neighboring blocks with respect to the current block, or a stored scale factor library; and reconstructing the current block based on the reference block and the identified scaling factor according to a linear equation.

Description

[0001] Incorporation by reference

[0002] This application is based on and claims the benefit of priority of U.S. Provisional Application No. 63 / 464,776, filed on May 8, 2023, which is incorporated herein by reference in its entirety. This application is also based on and claims the benefit of priority of U.S. Non-Provisional Patent Application No. 18 / 464,578, filed on September 11, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure describes a set of advanced video / stream encoding / decoding techniques. More specifically, the disclosed techniques relate to extensions to block adaptive weighted prediction (BAWP) to compensate for local illumination variations. Background Art

[0004] Uncompressed digital video may include a series of pictures and may have specific bit rate requirements for transmission bandwidth in storage, data processing, and streaming applications. One purpose of video encoding and video decoding may be to reduce redundancy in an uncompressed input video signal through various compression techniques. Summary of the invention

[0005] The present disclosure describes various embodiments of methods, apparatus, and computer-readable storage media that extend Block Adaptive Weighted Prediction (BAWP) by better referencing scale factors.

[0006] According to one aspect, an embodiment of the present disclosure provides a method for decoding a current block of a current frame in a coded video bitstream. The method includes receiving a coded video bitstream by a device. The device includes a memory storing instructions and a processor communicating with the memory. The method also includes: determining, by the device based on the coded video bitstream (e.g., based on a syntax element represented by a signal in the coded video bitstream), a prediction mode for predicting the current block based on a reference block, wherein the prediction mode includes a linear equation; deriving (or determining or identifying) a scale factor for the current block from at least one of the following: a plurality of scale factors of neighboring blocks relative to the current block, or a stored scale factor library; and reconstructing the current block by the device based on the reference block and the identified scale factor according to the linear equation.

[0007] According to another aspect, an embodiment of the present disclosure provides a device for processing a current block of a current frame in a coded video bitstream. The device includes a memory storing instructions; and a processor communicating with the memory. When the processor executes the instructions, the processor is configured to cause the device to perform the above-mentioned method for video decoding and / or encoding.

[0008] In another aspect, an embodiment of the present disclosure provides a non-transitory computer-readable medium storing instructions, which, when executed by a computer for video decoding and / or encoding, causes the computer to perform the above-mentioned method for video decoding and / or encoding.

[0009] The above-mentioned aspects and other aspects and their implementations are described in more detail in the drawings, the description and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Additional features, properties, and various advantages of the disclosed subject matter will become more apparent from the following detailed description and accompanying drawings, in which:

[0011] Figure 1 A schematic illustration showing a simplified block diagram of a communication system (100) according to an example embodiment;

[0012] Figure 2 A schematic illustration showing a simplified block diagram of a communication system (200) according to an example embodiment;

[0013] Figure 3 A schematic illustration showing a simplified block diagram of a video decoder according to an example embodiment;

[0014] Figure 4 A schematic illustration showing a simplified block diagram of a video encoder according to an example embodiment;

[0015] Figure 5 shows a block diagram of a video encoder according to another example embodiment;

[0016] Figure 6 shows a block diagram of a video decoder according to another example embodiment;

[0017] Figure 7 A scheme for dividing coding blocks according to an exemplary embodiment of the present disclosure is shown;

[0018] Figure 8 Another scheme of coding block partitioning according to an example implementation of the present disclosure is shown;

[0019] Fig. 9 Another scheme of coding block partitioning according to an example implementation of the present disclosure is shown;

[0020] Fig.10 Examples of templates for the current block and the reference block are shown;

[0021] Fig.11 An example of spatial neighbor motion for motion vector prediction is shown;

[0022] Fig.12 An example of a reference motion vector candidate library update process is shown;

[0023] Fig.13 shows an example of neighboring blocks used in overlapping block motion compensation processing;

[0024] Fig.14 An example logic flow of a method in the present disclosure is shown; and

[0025] Fig.15 A schematic diagram of a computer system according to an example implementation of the present disclosure is shown. DETAILED DESCRIPTION

[0026] The present invention will now 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 implementation. However, it is noted that the present invention may be implemented in a variety of different forms, and therefore, the subject matter covered or claimed is intended to be interpreted as not being limited to any of the implementations to be set forth below. It is also noted that the present invention may be implemented as a method, device, component or system. Therefore, embodiments of the present invention may, for example, take the form of hardware, software, firmware or any combination thereof.

[0027] Throughout the specification and claims, terms may have nuanced meanings that are suggested or implied in the context beyond the explicitly stated 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 the phrases "in another implementation" or "in other implementations" as used herein do not necessarily refer to different implementations. For example, it is intended that the claimed subject matter includes a combination of all or part of the exemplary embodiments / implementations.

[0028] Typically, terms can be understood at least in part from usage in context. For example, terms such as "and", "or" or "and / or" as used herein can include a variety of meanings depending at least in part on the context in which such terms are used. Typically, "or" (if used in an associative list, e.g., A, B, or C) is intended to mean: A, B, and C, used here in an inclusive sense; and A, B, or C, used here in an exclusive sense. In addition, depending at least in part on the context, the terms "one or more" or "at least one" as used herein 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, or characteristics in a plural sense. Similarly, terms such as "one", "an", or "the" can also be understood to convey singular usage or to convey plural usage, depending at least in part on the context. In addition, the term "based on" or "determined by..." can be understood to not necessarily be intended to convey an exclusive set of factors, and can alternatively allow the presence of additional factors that are not necessarily explicitly described, which also depends at least in part on the context.

[0029] 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 disclosure may not be so limited. The embodiments of the present disclosure can be implemented in desktop computers, laptop computers, tablet computers, media players, wearable computers, special video conferencing devices, etc. Network (150) 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 (150) 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.

[0030] As examples of applications for the disclosed subject matter, Figure 2 The placement of the video encoder and video decoder in a video streaming environment is shown. The disclosed subject matter can be equally applicable to other video applications, including, for example, video conferencing, digital TV broadcasting, gaming, virtual reality, storing compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0031] like Figure 2As shown, a video streaming system may include a video capture subsystem (213) that may include a video source (201), such as a digital camera, for creating an uncompressed video picture or image stream (202). In an example, the video picture stream (202) includes samples recorded by the digital camera of the video source (201). The video picture stream (202) is depicted as a thick line to emphasize the high amount of data when compared to the encoded video data (204) (or encoded video bitstream), and the video picture stream (202) may be processed by an electronic device (220) coupled to the video source (201) including a video encoder (203). 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. The encoded video data (204) (or encoded video bitstream (204)) is depicted as a thin line to emphasize the lower data volume when compared to the uncompressed video picture stream (202), and the encoded video data (204) can be stored on the streaming server (205) for future use or directly to a downstream video device (not shown). One or more streaming client subsystems such as Figure 2 The client subsystems (206) and (208) in the streaming server (205) can access the streaming server (205) to retrieve copies (207) and (209) of the encoded video data (204). The client subsystem (206) can include, for example, a video decoder (210) in the electronic device (230). The video decoder (210) decodes the incoming copy (207) of the encoded video data and creates an outgoing video picture stream (211) that is uncompressed and can be presented on a display (212) (e.g., a display screen) or other presentation device (not depicted).

[0032] Figure 3 A block diagram of a video decoder (310) of an electronic device (330) according to any embodiment of the present disclosure below is shown. The electronic device (330) may include a receiver (331) (e.g., receiving circuitry). The video decoder (310) may be used to replace Figure 2 A video decoder (210) in an example of FIG.

[0033] like Figure 3As shown, a receiver (331) can receive one or more encoded video sequences from a channel (301). To prevent network jitter and / or process playback timing, a buffer memory (315) can be set between the receiver (331) and an entropy decoder / parser (320) (hereinafter referred to as "parser (320)"). The parser (320) can reconstruct 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 information that may be used to control a rendering device such as a display (312) (e.g., a display screen). The parser (320) can parse / entropy decode the encoded video sequence. The parser (320) can extract a set of subgroup parameters for at least one of the pixel subgroups in the video decoder from the encoded video sequence. The subgroups can include groups of pictures (Groups of Picture, GOP), pictures, tiles, slices, macroblocks, coding units (Coding Unit, CU), blocks, transform units (Transform Unit, TU), prediction units (Prediction Unit, PU), etc. The parser (320) may also extract information such as transform coefficients (e.g., Fourier transform coefficients), quantizer parameter values, motion vectors, etc. from the encoded video sequence. The reconstruction of the symbols (321) may involve a number of different processing or functional units. The units involved and how they are involved may be controlled by subgroup control information parsed by the parser (320) from the encoded video sequence.

[0034] The first unit may include a scaler / inverse transform unit (351). The scaler / inverse transform unit (351) may receive quantized transform coefficients as (one or more) symbols (321) and control information from the parser (320), including information indicating which inverse transform to use, block size, quantization factors / parameters, quantization scaling matrix, etc. The scaler / inverse transform unit (351) may output blocks including sample values ​​that may be input into an aggregator (355).

[0035] In some cases, the output samples of the scaler / inverse transform (351) may belong to an intra-coded block, i.e., 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) may use surrounding block information that has already been reconstructed and stored in a current picture buffer (358) to generate a block of the same size and shape as the block being reconstructed. For example, the current picture buffer (358) buffers a partially reconstructed current picture and / or a fully reconstructed current picture. In some implementations, the aggregator (355) may add the prediction information that has been generated by the intra-prediction unit (352) to the output sample information as provided by the scaler / inverse transform unit (351) on a per-sample basis.

[0036] 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 such a case, the motion compensated prediction unit (353) may access the reference picture memory (357) based on the motion vector to obtain samples for inter-picture prediction. After motion compensation of the obtained reference samples according to the symbols (321) belonging to the block, these samples may be added to the output of the scaler / inverse transform unit (351) (the output of unit 351 may be referred to as residual samples or residual signal) by an aggregator (355) to generate output sample information.

[0037] The output samples of the aggregator (355) may be subjected to various loop filtering techniques in a loop filter unit (356) which may include several types of loop filters. The output of the loop filter unit (356) may be a sample stream which may be output to a rendering device (312) and stored in a reference picture memory (357) for future inter-picture prediction.

[0038] Figure 4 A block diagram of a video encoder (403) according to an example implementation of the present disclosure is shown. The video encoder (403) may be included in an electronic device (420). The electronic device (420) may also include a transmitter (440) (e.g., a transmission circuit system). The video encoder (403) may be used to replace Figure 4 A video encoder (403) in an example.

[0039] The video encoder (403) may receive video samples from a video source (401). According to some example embodiments, 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 an application. Implementing an appropriate encoding speed constitutes a function of a controller (450). In some embodiments, the controller (450) may be functionally coupled to and control other functional units as described below. Parameters set by the controller (450) may include rate control related parameters (picture skipping, quantizer, lambda value for rate distortion optimization techniques, ...), picture size, picture group (GOP) layout, maximum motion vector search range, etc.

[0040] In some example embodiments, the video encoder (403) may be configured to operate in a coding loop. The coding loop may include a source encoder (430) and a (local) decoder (433) embedded in the video encoder (403). The decoder (433) reconstructs symbols to create sample data in a manner similar to that in which the (remote) decoder would create sample data, although the embedded decoder 433 processes the coded video stream of the source encoder 430 without entropy coding (because in the video compression technology considered in the disclosed subject matter, any compression between the coded video bitstream in the symbol and the entropy coding can be lossless). At this point, it can be observed that any decoder technology other than parsing / entropy decoding that may only exist in the decoder may also necessarily need to exist in the corresponding encoder in substantially the same functional form. For this reason, the disclosed subject matter may sometimes focus on the decoder operation associated with the decoding portion of the encoder. Therefore, the description of the encoder technology can be simplified because the encoder technology is opposite to the decoder technology described comprehensively. A more detailed description of the encoder is provided below only in certain areas or aspects.

[0041] During operation, in some example implementations, the source encoder (430) may perform motion compensated predictive coding, which predictively encodes an input picture with reference to one or more previously encoded pictures from a video sequence designated as "reference pictures."

[0042] The local video decoder (433) can decode the encoded video data of the picture that can be designated as the 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 store a copy of the reconstructed reference picture locally that has common content (absent transmission errors) with the reconstructed reference picture to be obtained by the far-end (remote) video decoder.

[0043] The predictor (435) can perform prediction search for the encoding engine (432). That is, for a new picture to be encoded, the predictor (435) can search the reference picture memory (434) for sample data (as candidate reference pixel blocks) or certain metadata, such as reference picture motion vectors, block shapes, etc., that can be used as suitable prediction references for the new picture.

[0044] The controller (450) can manage encoding operations of the source encoder (430), including, for example, setting parameters and subgroup parameters for encoding video data.

[0045] 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(s) created by the entropy encoder (445) in preparation for transmission via a communication channel (460), which may be a hardware / software link to a storage device storing the encoded video data. 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).

[0046] The controller (450) may manage the operation of the video encoder (403). During encoding, the controller (450) may assign a particular encoding picture type to each encoded picture, which may affect the encoding techniques that may be applied to the corresponding picture. For example, a picture may generally be designated as one of the following picture types: intra picture (I picture), predictive picture (P picture), bidirectional predictive picture (B picture), multi-predictive picture. A source picture may generally be spatially subdivided into a plurality of sample coding blocks, as described in further detail below.

[0047] Figure 5 A diagram of a video encoder (503) according to another example implementation of the present disclosure is shown. The video encoder (503) is configured to receive a processed block (e.g., a predicted block) of sample values ​​within a current video image in a video image sequence and encode the processed block into an encoded picture that is part of an encoded video sequence. The example video encoder (503) may be used instead of Figure 4 A video encoder (403) in an example.

[0048] For example, the video encoder (503) receives a matrix of sample values ​​for a processing block. The video encoder (503) then uses, for example, rate-distortion optimization (RDO) to determine whether to best encode the processing block using intra mode, inter mode, or bi-prediction mode.

[0049] exist Figure 5 In the example of FIG. 5 , the video encoder ( 503 ) includes: Figure 5 The example arrangement shown in FIG. 1 includes 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.

[0050] The inter-frame encoder (530) is configured to: receive samples of a current block (e.g., a processing block); compare the block with one or more reference blocks in a reference picture (e.g., a block in a previous picture and a block in a subsequent picture in display order); generate inter-frame prediction information (e.g., motion vectors, merge mode information, description of redundant information according to inter-frame coding techniques); and calculate an inter-frame prediction result (e.g., a predicted block) based on the inter-frame prediction information using any suitable technique.

[0051] The intra encoder (522) is configured to: receive samples of a current block (e.g., a processing block); compare the block with already encoded blocks in the same picture; and generate quantized coefficients after transformation; and in some cases also generate intra prediction information (e.g., intra prediction direction information according to one or more intra coding techniques).

[0052] The general controller (521) can be configured to determine general control data and control other components of the video encoder (503) based on the general control data, for example, to determine a prediction mode for a block and provide a control signal to the switch (526) based on the prediction mode.

[0053] The residual calculator (523) may be configured to calculate the difference (residual data) between the received block and the prediction result of the block selected from the intra encoder (522) or the inter encoder (530). The residual encoder (524) may be configured to encode the residual data to generate a transform coefficient. The transform coefficient is then quantized to obtain a quantized transform coefficient. In various example embodiments, the video encoder (503) further includes a residual decoder (528). The residual decoder (528) is configured to perform an inverse transform and generate decoded residual data. The entropy encoder (525) may be configured to format the bitstream to include the coded block and perform entropy coding.

[0054] Figure 6 A diagram of an example video decoder (610) according to another embodiment of the present disclosure is shown. The video decoder (610) is configured to receive an encoded picture as part of an encoded video sequence and decode the encoded picture to generate a reconstructed picture. In an example, the video decoder (610) may be used instead of Figure 4A video decoder (410) in an example of FIG.

[0055] exist Figure 6 In the example of FIG. 6 , the video decoder ( 610 ) includes Figure 6 An 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 the example arrangement of.

[0056] The entropy decoder (671) may be configured to reconstruct certain symbols according to the coded picture, which represent the syntax elements constituting the coded picture. The inter-frame decoder (680) may be configured 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) may be configured to receive intra-frame prediction information and generate a prediction result based on the intra-frame prediction information. The residual decoder (673) may be configured 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) may be configured to combine the residual output by the residual decoder (673) with the prediction result (output by the inter-frame prediction module or the intra-frame prediction module, as the case may be) in the spatial domain to form a reconstructed block, which forms a part of the reconstructed picture as a part of the reconstructed video.

[0057] Note that the video encoders (203), (403) and (503) and the video decoders (210), (310) and (610) may be implemented using any suitable technology. In some example embodiments, the video encoders (203), (403) and (503) and the video decoders (210), (310) and (610) may be implemented using one or more integrated circuits. In another embodiment, the video encoders (203), (403) and (503) and the video decoders (210), (310) and (610) may be implemented using one or more processors executing software instructions.

[0058] Turning to the block partitioning for encoding and decoding, the general partitioning can start from the basic block and can follow a predefined set of rules, a specific pattern, a partitioning tree, or any partitioning structure or scheme. The partitioning can be hierarchical and recursive. After following any of the example partitioning processes described below or other processes or combinations thereof to block or partition the basic block, a final set of partitions or coding blocks can be obtained. Each of these partitions can be at one of the various partitioning levels in the partitioning hierarchy and can have various shapes. Each of the partitions can be referred to as a coding block (CB). For the 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 the following units, for which some basic encoding / decoding decisions can be made and encoding / decoding parameters can be optimized, determined, and represented in the encoded video bitstream with signals. The highest or deepest level in the final partition represents the depth of the coding block partitioning structure of the tree. The coding block can be a luminance coding block or a chrominance coding block. The CB tree structure of 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 division modes or structures for various color channels in a CTU may be the same or different.

[0059] In some implementations, the partitioning tree schemes or structures for the luma channel and the chroma channel may not need to be the same. In other words, the luma channel and the chroma channel may have separate coding tree structures or modes. In addition, whether the luma channel and the chroma channel use the same or different coding partitioning tree structures and the actual coding partitioning tree structures to be used may depend on whether the slice being encoded is a P slice, a B slice, or an I slice. For example, for an I slice, the chroma channel and the luma channel may have separate coding partitioning tree structures or coding partitioning tree structure modes, while for a P slice or a B slice, the luma channel and the chroma channel may share the same coding partitioning tree scheme. When a separate coding partitioning tree structure or mode is applied, the luma channel is divided into CBs by one coding partitioning tree structure, and the chroma channel may be divided into chroma CBs by another coding partitioning tree structure.

[0060] Figure 7 An example predefined 10-way partitioning structure / pattern is shown that allows recursive partitioning to form a partition tree. A root block may start from a predefined level (eg, from a basic block at a 128x128 level or a 64x64 level). Figure 7 Example partition structures include various 2:1 / 1:2 and 4:1 / 1:4 rectangular partitions. In some example implementations, Figure 7 The rectangular partitions of are not allowed to be further subdivided. The coding tree depth can be further defined to indicate the split depth starting from the root node or root block. For example, the coding tree depth of the root node or root block can be set to 0, and the root block can be divided into Figure 7 After one further split, the coding tree depth increases by 1. In some implementations, only full square partitions in 710 may be allowed to be Figure 7 The pattern is recursively partitioned to the next level of the partitioning tree.

[0061] In some other example implementations for coding block partitioning, a quadtree structure may be used. Such a quadtree split may be applied hierarchically and recursively to any square-shaped partition. Whether a basic block or an intermediate block or partition is further quadtree split may be adapted to various local characteristics of the basic block or intermediate block / partition.

[0062] In still other examples, the ternary partitioning scheme can be used to partition the basic block or any intermediate block, such as Figure 8 The ternary pattern can be implemented vertically as shown in 802, or horizontally as shown in 804. Although Figure 8 The example split ratio in is shown as 1:2:1, but other ratios may be predefined. In some implementations, two or more different ratios may be predefined. In some implementations, the width and height of the partitions of the example ternary tree are always powers of 2 to avoid additional transformations.

[0063] The above partitioning schemes can be combined in any way at different partitioning levels. As an example, the above quadtree partitioning scheme and binary partitioning scheme can be combined to partition the basic block into a quadtree-binary-tree (QTBT) structure. In such a scheme, the basic block or intermediate block / partition can be quadtree split or binary split, subject to a set of predefined conditions (if specified). Fig. 9A specific example is shown in , where the basic block is first split into four partitions by a quadtree, as shown in 902, 904, 906 and 908. Thereafter, each of the generated partitions is divided into four additional partitions (such as 908) by a quadtree at the next level, or is binary split into two additional partitions (e.g., horizontally or vertically, such as 902 or 906, both of which are symmetrical), or is not split (such as 904). For square-shaped partitions, binary splitting or quadtree splitting can be recursively allowed, as shown in the entire example partitioning pattern of 910 and the corresponding tree structure / representation in 920, where the solid line represents the quadtree split and the dotted line represents the binary split. A flag can be used for each binary split node (non-leaf binary partition) to indicate whether the binary split is horizontal or vertical. For example, as shown in 920, consistent with the partitioning structure of 910, the flag "0" can represent a horizontal binary split, and the flag "1" can represent a vertical binary split. For quadtree split partitioning, there is no need to indicate the split type, because quadtree splitting always splits a block or partition horizontally and vertically to produce 4 sub-blocks / partitions of equal size. In some implementations, a flag "1" may indicate a horizontal binary split, and a flag "0" may indicate a vertical binary split.

[0064] In some example implementations of QTBT, the quadtree and binary splitting rule set may be represented by the following predefined parameters and corresponding functions associated therewith:

[0065] –CTU size: the root node size of the quadtree (the size of the basic block)

[0066] –MinQTSize: Minimum allowed quadtree leaf node size

[0067] –MaxBTSize: Maximum allowed binary tree root node size

[0068] –MaxBTDepth: Maximum allowed binary tree depth

[0069] –MinBTSize: The minimum allowed binary tree leaf node size

[0070] In some example implementations of the QTBT partitioning structure, the CTU size can be set to 128×128 luma samples with two corresponding 64×64 blocks of chroma samples (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 first be 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 first through the binary tree because the size exceeds MaxBTSize (i.e., 64×64). Otherwise, nodes that do not exceed MaxBTSize can be split through 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 quadtree split. The basic block has a partition depth of 0. Each of the four partitions generated is 64×64 - not exceeding MaxBTSize, and further quadtree or binary tree splits are possible at level 1. Continue with this process. When the binary tree depth reaches MaxBTDepth (i.e., 4), no further splits can be considered. When the width of the binary tree node is equal to MinBTSize (i.e., 4), no further horizontal splits can be considered. Similarly, when the height of the binary tree node is equal to MinBTSize, no further vertical splits are considered.

[0071] In some example implementations, the above QTBT scheme can be configured to support the flexibility of having the same QTBT structure or separate QTBT structures for luma and chroma. For example, for P slices and B slices, the luma CTB and chroma CTB in one CTU can share the same QTBT structure. However, for I slices, the luma CTB can be divided into CBs by the QTBT structure, and the chroma CTB can be divided 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.

[0072] The above various CB partitioning schemes and further partitioning of CB to PB may be combined in any manner. The following specific implementations are provided as non-limiting examples.

[0073] Inter prediction may be implemented, for example, in a single reference mode or a composite reference mode. In some implementations, a skip flag may be first included in the bitstream of the current block (or at a higher level) to indicate whether the current block is inter-coded and is not skipped. If the current block is inter-coded, another flag may be further included in the bitstream as a signal indicating 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, two or more reference blocks may be used to generate a prediction block, for example, by weighted averaging. One or more reference blocks may be identified using one or more reference frame indexes and additionally using one or more corresponding motion vectors indicating the displacement between the reference block(s) and the current block relative to the frame (e.g., in horizontal and vertical pixels). For example, in single reference mode, an inter-frame prediction block for a current block may be generated from a single reference block identified as a prediction block by a motion vector in a reference frame, while for composite reference mode, a prediction block may 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. The motion vector(s) may be encoded and included in the bitstream in various ways.

[0074] In some example implementations, one or more reference picture lists including identifications of short-term reference frames and long-term reference frames for inter-frame 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-frame prediction, the single picture reference list being denoted as L0 reference (or reference list 0), while two picture reference lists may be formed for bidirectional inter-frame prediction, the two picture reference lists being 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 list and the L1 list may be ordered in various predetermined ways. The lengths of the L0 list and the L1 list 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-frame prediction may be in a single reference mode or in a composite reference mode. Bidirectional inter-frame prediction may be performed only in composite mode because bidirectional inter-frame prediction involves at least two reference blocks.

[0075] In some implementations, a merge mode (MM) for inter-frame prediction may be implemented. Typically, for merge mode, one or more of the motion vectors in the single reference prediction of the current PB or the motion vectors in the composite reference prediction may be derived from (one or more) other motion vectors, rather than being independently calculated and represented by a signal. For example, in an encoding system, the (one or more) current motion vectors of the current PB may be represented by (one or more) differences between (one or more) current motion vectors and one or more other already encoded motion vectors (referred to as reference motion vectors). Such (one or more) differences in (one or more) motion vectors, rather than the entirety of (one or more) current motion vectors, may be encoded and included in the bitstream, and may be linked to (one or more) reference motion vectors. Accordingly, in a decoding system, (one or more) motion vectors corresponding to the current PB may be derived based on (one or more) decoded motion vector differences and (one or more) decoded reference motion vectors linked thereto. As a specific form of general merge mode (MM) inter-frame prediction, such inter-frame prediction based on (one or more) motion vector differences may be referred to as a merge mode with motion vector difference (MMVD). Therefore, MM in general or MMVD in particular may be implemented to exploit the correlation between motion vectors associated with different PBs to improve coding efficiency. For example, adjacent PBs may have similar motion vectors, so the MVD may be small and may be efficiently encoded. For another example, for blocks that are similarly positioned / located in space, the motion vectors may be correlated in time (between frames).

[0076] In some example implementations of MMVD, a list of reference motion vectors (RMV) or MV predictor candidates for motion vector prediction may be formed for a block being predicted. The list of RMV candidates 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 neighboring blocks and / or temporal blocks in the same frame (e.g., blocks at the same position in a previous frame or subsequent frame of the current frame). These options represent blocks at a spatial position or temporal position relative to the current block that may have motion vectors similar to or identical to the current block. The size of the list of MV predictor candidates may be predetermined. For example, the list may contain two or more candidates. In order to be on the list of RMV candidates, for example, the candidate block may be required to have the same reference frame (or frame) 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 implementations, if available and the above conditions are met, the list of merge candidates can be first populated with spatially adjacent blocks (scanned in a specific predefined order), and then the list of merge candidates can be populated with temporal blocks if space is still available in the list. For example, adjacent RMV candidate blocks can be selected from the left and top blocks of the current block. The list of RMV predictor candidates 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.

[0077] In some implementations, 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 being 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 of the RMV candidates more closely predicts the MV of the current coding block and signal the selection as an index into the DRL.

[0078] In some example implementations of MMVD, after an RMV candidate is selected and used as a base motion vector predictor for a motion vector to be predicted, a motion vector difference (MVD or delta MV, representing the difference between the motion vector to be predicted and a 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.

[0079] In some example implementations of MMVD, a distance index may be used to specify magnitude information of a motion vector difference, and the distance index may be used to 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 component or the 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.

[0080] Table 1 - Example relationship between distance index and predefined MV offsets

[0081]

[0082] In some example implementations of MMVD, a direction index may also be signaled, and the direction index is used to indicate the direction of the MVD relative to a reference motion vector. In some implementations, 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 description of the MVD may vary according to the information of the start / reference MV. For example, when the start / reference MV corresponds to a unidirectional prediction block or corresponds to a bidirectional prediction block, where both 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 symbol (direction) of the MV offset added to the start / reference MV. When the start / reference MV corresponds to a bidirectional prediction block having two reference pictures at 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.

[0083] Table 2 - Example implementation of the sign of the MV offset specified by the direction index

[0084] Directions to IDX 00 01 10 11 x-axis (horizontal) + – N / A N / A y-axis (vertical) N / A N / A + –

[0085] In some example implementations, the MVD may be scaled according to the difference in POC in each direction. If the difference in POC is the same in both lists, no scaling is required. Otherwise, if the difference in POC in reference list 0 is greater than the difference in POC of reference list 1, the MVD of reference list 1 is scaled. If the difference in POC 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, then the MVD is added to the available or reference MV.

[0086] In some example implementations 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 such that only one MVD needs to be signaled and the other MVD can be derived from the signaled MVD. In such an implementation, motion information including reference picture indices of list 0 and list 1 is not signaled simultaneously. 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), then a 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, BiDirPredFlag may be set to 1 if the nearest reference picture in list 0 and the nearest reference picture in list 1 form a forward and backward pair of reference pictures or a backward and forward pair of reference pictures, and both the list 0 reference picture and the list 1 reference picture are short-term reference pictures. Otherwise, BiDirPredFlag is set to 0. BiDirPredFlag of 1 may indicate that a symmetry mode flag is additionally signaled in the bitstream. When BiDirPredFlag is 1, the decoder may extract the symmetry mode flag from the bitstream. For example, the symmetry mode flag may be signaled at the CU level (if necessary), and the symmetry mode flag may indicate whether a symmetric MVD coding mode is being used for the corresponding CU. When the symmetric mode flag is 1, it indicates that the symmetric MVD coding mode is used, and only the reference picture indexes of both list 0 and list 1 (referred to as "mvp_l0_flag" and "mvp_l1_flag") and the MVD associated with list 0 (referred to as "MVD0") are signaled, and another motion vector difference "MVD1" is derived instead of signaled. For example, MVD1 can be derived as -MVD0. Thus, in the example symmetric MVD mode, only one MVD is signaled.

[0087] In some other example implementations of MV prediction, for both single reference mode and composite reference mode MV prediction, a coordination scheme can be used to implement general merge mode MMVD and some other types of MV prediction. Various syntax elements can be used to signal the way to predict the MV of the current block. For example, for single reference mode, the following MV prediction modes can be signaled: NEARMV - directly using one of the motion vector predictors (MVPs) in the list indicated by the DRL (dynamic reference list) index without any MVD; NEWMV - using one of the motion vector predictors (MVPs) in the list indicated by the DRL index as a reference and applying an increment to the MVP (e.g., using MVD); and GLOBALMV - using motion vectors based on frame-level global motion parameters.

[0088] Similarly, for a composite reference inter-frame prediction mode using two reference frames corresponding to two MVs to be predicted, the following MV prediction modes may be signaled: NEAR_NEARMV - one of the motion vector predictors (MVPs) in the list signaled by the DRL index is used without an MVD for each of the two MVs to be predicted. NEAR_NEWMV - to predict the first of the two motion vectors, one of the motion vector predictors (MVPs) in the list signaled by the DRL index is used as a reference MV without an MVD; to predict the second of the two motion vectors, one of the motion vector predictors (MVPs) in the list signaled by the DRL index is used as a reference MV in combination with a delta MV (MVD) signaled separately. NEW_NEARMV - To predict the second of the two motion vectors, one of the motion vector predictors (MVPs) in the list signaled by the DRL index is used as a reference MV without MVD; to predict the first of the two motion vectors, one of the motion vector predictors (MVPs) in the list signaled by the DRL index is used as a reference MV in combination with a delta MV (MVD) also signaled. NEW_NEWMV - One of the motion vector predictors (MVPs) in the list signaled by the DRL index is used as a reference MV and is used in combination with a delta MV also signaled for prediction for each of the two MVs. GLOBAL_GLOBALMV - Uses MVs from each reference based on its frame level global motion parameters.

[0089] The term "NEAR" above refers to MV prediction using a reference MV as a general merge mode without any MVD, while the term "NEW" refers to MV prediction involving using a reference MV as in MMVD mode and offsetting the reference MV using a signaled or derived MVD. For composite inter prediction, the reference base motion vector and motion vector increment above may generally be different or independent between two references or two MVDs, even though the two MVDs may be correlated, for example, and such correlation may be exploited to reduce the amount of information required to signal the two motion vector increments. In order to exploit such correlation, joint signaling of the two MVDs may be implemented and indicated in the bitstream, as described in further detail below.

[0090] In some example implementations of the MVD, a predefined pixel resolution of the MVD may be allowed. For example, a motion vector precision (or accuracy) of 1 / 8 pixel may be allowed. The MVD described above in various MV prediction modes may be constructed and signaled in various ways. In some implementations, various syntax elements may be used to signal the one or more motion vector differences described above in reference frame list 0 or list 1.

[0091] For example, a syntax element called "mv_joint" may specify which components of the motion vector difference associated therewith are non-zero. For example, mv_joint having a value of 0 may indicate that there is no non-zero MVD in the horizontal or vertical direction; mv_joint having a value of 1 may indicate that there is a non-zero MVD only in the horizontal direction; mv_joint having a value of 2 may indicate that there is a non-zero MVD only in the vertical direction; and / or mv_joint having a value of 3 may indicate that there is a non-zero MVD in both the horizontal and vertical directions.

[0092] When the "mv_joint" syntax element of the MVD signals the absence of non-zero MVD components, no further MVD information is signaled. However, if the "mv_joint" syntax signals the presence of one or two non-zero components, additional syntax elements may be further signaled for each of the non-zero MVD components as described below.

[0093] For example, a syntax element called "mv_sign" may be used to additionally specify whether the corresponding motion vector difference amount is positive or negative.

[0094] For another example, a syntax element called "mv_class" can be used to specify the class of motion vector differences in a predefined set of classes for corresponding non-zero MVD components. For example, the predefined classes of motion vector differences can be used to divide the continuous magnitude space of motion vector differences into non-overlapping class ranges. Therefore, the MVD class represented by the signal indicates the magnitude range of the corresponding MVD component. In the example implementation shown in Table 3 below, a higher class corresponds to a motion vector difference with a larger magnitude range. The symbol (n, m] is used to represent a range of motion vector differences greater than n pixels and less than or equal to m pixels.

[0095] Table 3: Motion vector difference magnitude categories

[0096] MV Category MVD value 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]

[0097] In some other examples, a syntax element called "mv_bit" may be further used to specify the integer part of the offset between the non-zero motion vector difference component and the start magnitude of the corresponding signaled MV class magnitude range. In some other examples, a syntax element called "mv_fr" may be further used to specify the first 2 fractional bits of the motion vector difference for the corresponding non-zero MVD component, and a syntax element called "mv_hp" may be used to specify the third fractional bit (high resolution bit) of the motion vector difference for the corresponding non-zero MVD component. The two bits "mv_fr" essentially provide 1 / 4 The MVD resolution of 1 / 8 pixel or higher may be supported, while the "mv_hp" bit may further provide a resolution of 1 / 8 pixel. In some other implementations, more than one "mv_hp" bit may be used to provide an MVD pixel resolution finer than 1 / 8 pixel. In some example implementations, an additional flag may be signaled at one or more of the various levels to indicate whether an MVD resolution of 1 / 8 pixel or higher is supported. If an MVD resolution is not applied to a particular coding unit, the above-mentioned syntax element for the corresponding unsupported MVD resolution may not be signaled.

[0098] In some example implementations, in bi-prediction with CU-level weight (BCW), a bi-prediction signal may be generated by averaging two prediction signals obtained from two different reference pictures and / or using two different motion vectors. In some other implementations, the bi-prediction mode may be extended beyond simple averaging to allow weighted averaging of two prediction signals. For example, P bi-pred =((8-w)*P 0 +w*P 1+4)>>3. Five weights, w∈{-2,3,4,5,10}, are allowed in weighted average bidirectional prediction. When w is equal to 4, equal weight factors are used to perform weighted averaging of two predicted samples. For each bidirectionally predicted CU, the weight w can be determined in one of the following two ways: 1) for non-merged CUs, the weight index is signaled after the motion vector difference; and / or 2) for merged CUs, the weight index is inferred from neighboring blocks based on the merge candidate index. BCW can be applied only to CUs with 256 or more luma samples (i.e., the CU width multiplied by the 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.

[0099] In some implementations, block adaptive weighted prediction (BAWP) may include block-level weighted prediction to model local illumination variations between a current block and its prediction block based on local illumination variations between a current block template (or a causal sample of the current block) and a reference block template. Fig.10 A template of a current block (1010) (or referred to as a current template, 1012) and a template of a reference block (1020) (or referred to as a reference template, 1022) are shown. The reference block may be indicated or determined by a motion vector (MV, 1030). 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 implementations, the function may be a linear function. The parameters of the function may be represented by a scale factor α and an offset β, which form a linear equation, i.e., α*p[x]+β, to compensate for illumination changes, where p[x] is the reference sample pointed to by the MV at position x on the reference picture. In some implementations, α and β may be derived based on the current block template and the reference block template, and they do not require signaling overhead. In some implementations, a BAWP flag may be signaled for a single inter prediction mode to indicate the use of BAWP. BAWP may be applied to blocks of size greater than or equal to 8×8 and encoded in a single inter prediction mode. In some implementations, BAWP may be applied only to luma components. In some implementations, BAWP may be referred to as local illumination compensation (LIC).

[0100] In some implementations of explicit signaling with BAWP, when a current block is predicted from a reference block of the current block using a linear function with a scale α and an offset β, the selection / value of the scale α and / or the offset β can be signaled into the bitstream and parsed at the decoder side to reconstruct the predicted block. The reference block is specified by a motion vector associated with the current block. All supporting values ​​of the scale α are stored in a predefined lookup table, and the index of the scale factor in the lookup table can be signaled in the bitstream and parsed at the decoder side. The offset value β can be derived from a linear equation between the reference block and the current block. The offset value β is set to (cur_template_mean-α*ref_template_mean), where cur_template_mean indicates the average value of the samples in the template of the current block, and ref_template_mean indicates the average value of the samples in the template of the reference block.

[0101] In some implementations, one or more spatial motion vector predictors (SMVP, both adjacent SMVP and non-adjacent SMVP), one or more temporal motion vector predictors (TMVP), one or more additional MV candidates and additionally derived MVPs and one or more reference library MVPs are additionally added. A stack with a fixed size can be generated at the encoder and decoder sides to store the MVP, which is called a motion vector predictor list.

[0102] The MVP list can be constructed to save a predefined number of reconstructed MVP candidates (SMVP, TMVP or other derived MVP or other types of MVP candidates) for the current coding block or super block on the encoder side and the decoder side. When the current prediction block is encoded in the inter-frame prediction mode, the encoder will select the MVP that provides the best coding efficiency from the candidates in the MVP candidate list as the predictor of the motion vector of the current prediction block. The index of the MVP selected in the MVP list can be represented by a signal in the bitstream. When the bitstream is reconstructed, the decoder will update the MVP list of the current coding block or super block accordingly, extract the MVP index of the prediction block of the current inter-frame prediction, obtain the MVP from the MVP candidate list according to the extracted MVP index in the MVP list, and use the MVP as the predictor of the motion vector of the current prediction block to reconstruct the motion vector of the current prediction block (for example, by combining the extracted motion vector predictor and the corresponding MVD from the MVP list). For example, the MVP list can represent a stack with a predefined fixed size.

[0103] The spatial motion vector predictor may be an adjacent SMVP or a non-adjacent SMVP. An adjacent SMVP may refer to a motion vector predictor belonging to a prediction block adjacent to a current coding block or super block. A non-adjacent SMVP may refer to a motion vector predictor belonging to a prediction block that is not immediately adjacent to the current coding block or super block. Other types of MVP candidates may be further derived from the reconstructed motion vectors. For another example, one or more additional MVP libraries may be maintained as one of the sources for establishing an MVP list, as described in further detail below.

[0104] like Fig.11 As shown, a spatial motion vector (MV) predictor may be derived from spatial neighboring blocks of a current block (1120). The spatial neighboring blocks of the current block may include: i) adjacent spatial neighboring blocks (indicated by 1101 and 1102), which are direct neighbors on the top and left of the current block, and ii) non-adjacent spatial neighboring blocks (e.g., indicated by 1106, 1108, 1105, 1107, 1104, or 1103), which are close to the current block but not directly adjacent to the current block. Fig.11 An example of a set of spatially neighboring blocks for a luma block is shown, where each spatially neighboring block is an 8×8 block.

[0105] In some implementations, spatially neighboring blocks are checked to find one or more MVs associated with the same reference frame index as the current block. For the current block, the search order for spatially neighboring 8×8 luma blocks is as follows: Fig.11 The sequence numbers 1101 to 1108 in FIG. 1 are shown as follows. 1. Check the top adjacent row from left to right. 2. Check the left adjacent column from top to bottom. 3. Check the top right adjacent block. 4. Check the top left adjacent block. 5. Check the first top non-adjacent row from left to right. 6. Check the first left non-adjacent column from top to bottom. 7. Check the second top non-adjacent row from left to right. 8. Check the second left non-adjacent column from top to bottom.

[0106] In some implementations, the adjacent candidates (1011 to 1103) may be a set of MVPs that are first placed in the MV predictor list before the TMVP; and / or non-adjacent candidates (also referred to as external candidates, i.e., candidates 1104 to 1108) may be placed in the MV predictor list after the TMVP. All SMVP candidates should have the same reference picture as the current block. That is, when the current block has a single reference picture, the MVP candidate may have a single reference picture and the reference picture is the same as the reference picture of the current block, or have a composite reference picture (2 reference pictures) and one of the reference pictures is the same as the reference picture of the current block, and the MVP candidate may be placed in the MV predictor list. In some other implementations, when the current block has two reference pictures, only when the MVP candidate has two reference pictures, both of which are the same as the reference picture of the current block. In some implementations, external lines 1105 and 1107 may be further removed from the non-adjacent candidates to reduce line memory.

[0107] In some implementations, a reference motion vector candidate library can be used. In some implementations, each buffer corresponds to a unique reference frame type, which corresponds to a single reference frame or a pair of reference frames covering a single inter-frame mode and a composite inter-frame mode, respectively. All buffers are the same size. When a new MV is added to a full buffer, the existing MV is driven out to make room for the new MV. In some implementations, in addition to the reference MV candidates obtained by the traditional reference MV list generation, the coding block can refer to the MV candidate library to collect reference MV candidates. After encoding the super block, the MV library is updated with the MV used by the coding block of the super block. In some implementations, each tile has an independent MV reference library used by all super blocks in the tile. At the beginning of encoding each tile, the corresponding library is cleared. Thereafter, when encoding each super block in the tile, the MV from the library can be used as an MV reference candidate. At the end of encoding the super block, the library is updated.

[0108] In some implementations, the library update process can be Fig.12 The library update process can be based on super blocks. That is, after a super block is encoded, the first (up to 64) candidate MVs used by each encoding block within the super block can be added to the library. During the update, the pruning process is also involved during the update.

[0109] In some implementations, with respect to library reference processing, after completing the reference MV candidate scan, when there is an open slot in the candidate list, the encoder and / or decoder can refer to the MV candidate library (in the buffer with the matching reference frame type) to obtain additional MV candidates. From the end of the buffer backward to the beginning, when the MV in the library buffer does not exist in the candidate list, it can be appended to the candidate list.

[0110] In some implementations, for inter-coded blocks, overlapped block motion compensation (OBMC) may be allowed when the following conditions are met: the current block uses a single reference prediction, the width or height of the coding block is greater than or equal to 8, and at least one of the neighboring blocks is inter-coded. In some implementations, when OBMC is applied to the current block, initial inter-prediction samples are first generated by using the MV associated with the current block. Then, the inter-prediction samples of the current block and the inter-prediction samples derived using the MVs from the top and left neighboring blocks are mixed to generate the final prediction samples. The maximum number of neighboring MVs may be limited by the size of the current block; a maximum of four MVs from each of the top and left neighboring blocks may be used in the OBMC process of the current block. For each of the top and left neighboring blocks, when more than four MVs have been identified, OBMC is applied only to the prediction samples associated with the first four MVs.

[0111] Fig.13 A non-limiting example of the processing order of neighboring blocks is shown, where the values ​​(0 to 4) marked in each block indicate the processing order of the MVs of the current block and the neighboring blocks. Specifically, the MV of the current block is first applied to generate the inter-frame prediction sample p 0 (x, y). Then, the MV of block 1 is applied to generate the prediction sample p 1 (x, y). Then, the prediction samples in the overlapping area between block 0 and block 1 (in Fig.13 Marked in gray in the figure) as p 0 (x,y) and p 1 The weighted average of (x,y) is given. The MVs of blocks 2, 3 and 4 are further applied and mixed in the same way. The weights w(x,y) are generated using a rising sine function as shown below: Where y = 0, 1, ..., and H / 2-1, H is the current block height.

[0112] In some other example implementations, a warp motion model may be used. Conventional motion compensation may assume a translational motion model between a reference block and a target block, and the warp motion may utilize an affine model, which may be represented by the following equation:

[0113]

[0114] Where [x, y] is the coordinate of the original pixel, and [x', y'] is the warped coordinate of the reference block. From the above equation, we can see that up to six parameters are required to specify the warp motion: a 3 and b 3 Specifies a regular translation MV; a 1 and b 2 specifies the scaling along the MV; and a 2 and b 1 Specifies the rotation.

[0115] In some implementations, when a block is encoded in BAWP mode, a flag may be signaled to indicate whether explicit or implicit signaling of the BAWP scale factor is used. When implicit signaling of the BAWP scale factor is employed, the BAWP scale factor and offset value may be derived from a linear equation based on a template of the current block and a template of a reference block pointed to by a motion vector of the current block. When explicit signaling of the BAWP scale factor is employed, another flag is signaled to indicate which scale factor is used for the current block, and the offset is derived as zero. The supported scale factors may be stored in one or more predefined lookup tables, and the index of the scale factor in the lookup table is signaled into the bitstream and parsed at the decoder side.

[0116] In the present disclosure, a lookup table may also be referred to as a list, and a scale factor lookup table may be referred to as a scale factor candidate list. In the present disclosure, a NEARMV mode may be referred to as a coding mode that inherits motion vectors of neighboring blocks; and / or a NEWMV mode may be referred to as a coding mode that signals a motion vector difference relative to a motion vector predictor selected from a spatially or temporally neighboring block; and / or an AMVDNEWMV mode may be referred to as a coding mode that signals a motion vector difference relative to a motion vector predictor selected from a spatially or temporally neighboring block and implicitly determines the precision of the motion vector based on the magnitude of the motion vector.

[0117] In some implementations, there are some issues or problems associated with the BAWP method, particularly how the scale factor information is signaled and / or indicated, which can be solved or improved to improve encoding / decoding efficiency. For non-limiting examples, the scale factor information from neighboring blocks is not used for the BAWP mode in the current block, and in some cases, there may be room for further improvement in the use of BAWP or other methods to improve encoding / decoding efficiency. The present disclosure describes various embodiments for providing extensions to BAWP, solving at least one of the above-mentioned problems or problems, improving encoding / decoding efficiency, and advancing video codec technology. Various embodiments can provide more accurate predictions by using multiple reference blocks for prediction; and / or can save signaling by deriving a model of motion vectors.

[0118] The various embodiments and / or implementations described in this disclosure 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 system (e.g., one or more processors or one or more integrated circuits). One or more processors execute a program stored in a non-transitory computer-readable medium. In this disclosure, the term block may be interpreted as a prediction block, a coding block, or a coding unit (CU). In this disclosure, the direction of a 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.

[0119] In some embodiments, if one or more linear models are used in BAWP / LIC mode to describe the linear relationship between the current block and one or more of its reference blocks, the scale factors of its adjacent / non-adjacent neighboring blocks or the scale factors stored in the library can be used for the current block. In one embodiment, if a linear model is used for the current block, a flag is signaled to indicate whether the scale factor is obtained from the adjacent / non-adjacent neighboring blocks or the scale factors stored in the library. If so, another flag is signaled to indicate which of these scale factors is used for the current block. In one embodiment, the scale factors from its adjacent / non-adjacent neighboring blocks or the scale factors from the library are stored together in a list, and the scanning order of these scale factors is the same as the scanning order in the MVP list generation process. In one embodiment, the scale factors for the coding blocks in the current frame / tile / slice / super block row can be stored in different libraries based on the reference frame. When the reference frame (or reference frame pair) of the current block matches the reference frame of the scale factor in the library, the scale factor can be extracted from the library. In one embodiment, all scale factors for the coding blocks in the current frame / tile / slice / super block row can be stored in one library. In one embodiment, when the library is full, a first in first out (FIFO) rule is used to update the scale factors in the library. Specifically, according to the disclosed method, an example decoder can receive a coded video bitstream. In addition, the decoder can determine a prediction mode for predicting a current block based on a reference block based on a syntax element represented by a signal in the coded video bitstream, wherein the prediction mode includes a linear equation. The decoder can also derive the scale factor for the current block from at least one of the following: a plurality of scale factors of neighboring blocks relative to the current block, or a stored scale factor library. The decoder can then reconstruct the current block based on the reference block and the identified scale factor according to the linear equation.

[0120] Fig.14A flowchart 1400 of an exemplary method for decoding a current block of a current frame in a coded video bitstream following the basic principles of the above implementation is shown, and the exemplary method can be performed by an electronic device (e.g., a decoder). The exemplary decoding method flow starts at 1401 and can include some or all of the following steps: S1410, receiving a coded video bitstream; S1420, based on syntax elements represented by signals in the coded video bitstream, determining a prediction mode for predicting a current block based on a reference block, wherein the prediction mode includes a linear equation; S1430, deriving a scale factor for the current block from at least one of the following: a plurality of scale factors of neighboring blocks relative to the current block, or a stored scale factor library; and / or S1440, reconstructing the current block based on the reference block and the identified scale factor according to the linear equation. The exemplary method stops at S1499.

[0121] In any part or combination of the above implementations, the neighboring blocks relative to the current block include one or more adjacent neighboring blocks and one or more non-adjacent neighboring blocks.

[0122] In any part or combination of the foregoing implementations, the one or more adjacent neighboring blocks include at least one of the following: one or more top adjacent neighboring blocks, one or more left adjacent neighboring blocks, or top right adjacent blocks; and / or the one or more non-adjacent neighboring blocks include at least one of the following: top left adjacent blocks, one or more nearest top non-adjacent neighboring blocks, one or more nearest left non-adjacent neighboring blocks, one or more second nearest top non-adjacent neighboring blocks, or one or more second nearest left non-adjacent neighboring blocks.

[0123] In any part or combination of the foregoing implementations, deriving (or identifying or determining) the scale factor for the current block includes: extracting a first flag based on a coded video bitstream, the first flag indicating whether the scale factor for the current block comes from a plurality of scale factors of neighboring blocks or a stored scale factor library; extracting a second flag based on the coded video bitstream, the second flag indicating which scale factor from a plurality of scale factors of neighboring blocks or a stored scale factor library is used as the scale factor for the current block; and / or identifying the scale factor for the current block based on the first flag and the second flag.

[0124] In any portion or combination of the above implementations, the scale factor list includes a plurality of scale factors for neighboring blocks and a stored scale factor library.

[0125] In any part or combination of the above implementations, deriving the scale factor for the current block includes: in response to the previously coded block using the scale factor from the scale factor list, identifying the scale factor for the previously coded block as the scale factor for the current block without additional signaling.

[0126] In any part or combination of the above implementations, deriving the scale factor for the current block includes: in response to the reference block using the scale factor from the scale factor list, identifying the scale factor for the reference block as the scale factor for the current block without additional signaling.

[0127] In any portion or combination of the above implementations, the scale factors in the scale factor list have a scanning order in which adjacent neighboring blocks precede non-adjacent neighboring blocks.

[0128] In any portion or combination of the above implementations, the scale factors in the scale factor list have the same scanning order as the motion vector predictor (MVP) in the MVP list.

[0129] In any portion or combination of the above implementations, the stored scale factor library includes all scale factors for previously coded blocks in one of the current frame, the current tile, the current slice, and the current super block.

[0130] In any part or combination of the above implementations, each of the stored scale factor libraries is based on a reference frame corresponding to a reference block of a previously coded block in one of a current frame, a current tile, a current slice, and a current super block; and / or a scale factor is identified from a stored scale factor library whose reference frame matches a reference frame of a reference block corresponding to the current block.

[0131] In any portion or combination of the above implementations, in response to the stored scale factor library being full, the stored scale factor library is updated according to a first-in-first-out (FIFO) model.

[0132] In any portion or combination of the above implementations, the current block includes more than one motion vector, each of the motion vectors corresponds to a linear model.

[0133] In various embodiments of the present disclosure, when one or more linear models are used in BAWP / LIC mode to describe the linear relationship between a current block and one or more reference blocks thereof, scaling factors of its adjacent / non-adjacent neighboring blocks or scaling factors stored in a library may be used for the current block.

[0134] In some implementations, the scale factor for the current block may not need to be signaled, and for non-limiting examples, a previously used scale factor in a scale factor list may be reused and / or a scale factor for an MVP reference block may be used to derive / indicate a scale factor for the current block if the MVP reference block uses a scale factor.

[0135] In some implementations, when a linear model is used for the current block, a flag may be signaled to indicate whether the scale factor is obtained from an adjacent / non-adjacent neighboring block or a scale factor stored in a library. When it is determined to signal a flag to indicate that the scale factor is obtained from an adjacent / non-adjacent neighboring block or a scale factor stored in a library, another flag may be signaled to indicate which of these scale factors is used for the current block. In some implementations, the adjacent / non-adjacent neighboring block may indicate Fig.11 In some implementations, the order of adjacent / non-adjacent adjacent blocks can follow Fig.11 Sorting of neighboring blocks in .

[0136] In some implementations, the scale factors from its adjacent / non-adjacent neighboring blocks or the scale factors from the library can be stored together in a list, and the scanning order of these scale factors can be the same as the scanning order in the MVP list generation process. For non-limiting examples, the scanning order of these scale factors can follow Fig.11 The order of adjacent blocks in .

[0137] In some implementations, the scale factors for the coding blocks in the current frame / tile / slice / superblock row may be stored in different libraries based on the reference frames, for example, there may be 5 different libraries corresponding to 5 reference frames. For a non-limiting example, when there are two reference frames (reference frame 0 and reference frame 1), two libraries may be used, where the first library stores the scale factors corresponding to reference frame 0, and the second library stores the scale factors corresponding to reference frame 1. In some implementations, the scale factor may be extracted from a library when the reference frame (or reference frame pair) of the current block matches the reference frame of a scale factor in the library.

[0138] In some implementations, all scale factors for coding blocks in the current frame / tile / slice / superblock row may be stored in one library, e.g., there may be a single library corresponding to multiple reference frames. For non-limiting example, when there are two reference frames (reference frame 0 and reference frame 1), a single library corresponding to reference frame 0 and reference frame 1 may be used.

[0139] In some implementations, when the library is full, the scale factors in the library may be updated using a first-in-first-out (FIFO) rule. In some implementations, the library update process may follow some or all of the other descriptions in this disclosure, such as with Fig.12 Related description.

[0140] In some implementations, deriving the scale factor for the current block includes deriving the scale factor for the current block according to a predefined configuration (or a default configuration); for non-limiting examples, the first scale factor in a library of scale factors, or a scale factor used by a top / left adjacent neighboring block, wherein the decoder can derive the scale factor without parsing the scale factor from any syntax element explicitly signaled in the encoded bitstream.

[0141] In some implementations, when the current block includes more than one motion vector and each motion vector points to a block in a reference frame, multiple linear models can be used in BAWP / LIC mode to describe the linear relationship between the current block and its multiple reference blocks. For each linear model, the linear function includes a scale factor α and an offset β, wherein the scale factor α and / or the offset β can be derived from a template of the current block and a template of each of the reference blocks, or the scale factor α and / or the offset β can be signaled into the bitstream by the encoder and then parsed by the decoder to reconstruct the predicted block to obtain the current block. Each of the reference blocks is specified by a motion vector associated with its reference frame.

[0142] In some implementations, when the current block includes more than one motion vector and each motion vector points to one of the reference blocks, at least one linear model is employed to describe a linear relationship between the current block and one of its reference blocks.

[0143] In some implementations, when the current block includes more than one motion vector and each motion vector points to a block in the reference frame, a linear model is used for each motion vector. For non-limiting example, when the current block has two motion vectors, two linear models are used for the two motion vectors.

[0144] In some implementations, the scaling factor or index of the scaling factor is signaled separately for each model, and / or the offset for each model is derived based on a linear model equation.

[0145] In some implementations, supported values ​​of the adjustment (or delta value) of the scale factor are stored in a predefined lookup table, and the index of the adjustment of the scale factor is signaled separately for each model, and the offset of each model is derived separately based on the linear model equation. The adjustment (or delta value) of the scale factor is based on the derived scale factor between the template of the current block and the template of the reference block pointed to by the motion vector.

[0146] In some implementations, the supported scaling factors or adjustments of scaling factors are symmetrically distributed around a threshold value (TH), and for non-limiting examples, TH is equal to 0 or 1.

[0147] In some implementations, a portion of the scale factor is signaled, while another portion of the scale factor is not signaled. The portion of the scale factor that is not signaled may be derived based on a template of the current block and a template of a reference block pointed to by a motion vector, or may be equal to a default value. For a non-limiting example, when the current block has two motion vectors, two linear models are used for the two motion vectors respectively; the scale factor for one linear model is signaled, and the scale factor for the other linear model takes a default value or is derived based on a template of the current block and a template of a reference block pointed to by a motion vector. In some implementations, the default value may be 1.

[0148] In some implementations, the decision as to which scale factor to signal may depend on the SAD / SSE cost between the template of the current block and the template of the current block predicted from the template of the reference block using the derived scale factor and offset. For non-limiting example, the scale factor with the larger SAD / SSE cost may be signaled, and the scale factor with the smaller SAD / SSE cost may be derived or defaulted.

[0149] In some implementations, the decision about which scale factor is signaled may depend on the POC of the reference block relative to the current block. For non-limiting example, the scale factor with the larger POC may be signaled, and the scale factor with the smaller POC may be derived or defaulted.

[0150] In some implementations, one or more syntaxes can be signaled by the encoder and / or parsed by the decoder to indicate which scale factor is selected for signaling or derivation.

[0151] In various embodiments, when the current block has more than one motion vector, each motion vector pointing to a different block in the reference frame, a linear model may be used to generate prediction samples for one of the motion vectors. Other modes (e.g., translational motion, warp motion, or OBMC) other than the linear model may be used for the other motion vectors to generate prediction samples. Two or more prediction blocks are then weighted and averaged to generate multi-prediction (e.g., bidirectional prediction for two motion vectors) prediction samples.

[0152] In some implementations, the decision about which motion vector to use with the linear model can be signaled in the bitstream by the encoder and resolved at the decoder side.

[0153] In some implementations, the decision about which motion vector to use with the linear model may be derived implicitly based on the encoding information of the current block and / or neighboring blocks. In one example, the decision may depend on the SAD / SSE cost between the template of the current block and the template of the current block predicted from the template of the reference block using the derived scale factor and offset. For non-limiting examples, the motion vector with the smaller SAD / SSE cost may use the linear model, and the motion vector with the larger SAD / SSE may use a model other than the linear model.

[0154] In some implementations, when it is decided not to use a linear model for a motion vector of the current block, another flag may be signaled to indicate which of the following models to use for the motion vector: translation model, warp model, or OBMC.

[0155] In various embodiments, when the current block includes more than one motion vector and each motion vector points to a block in the reference frame, a linear model is used for each motion vector. In some implementations, the linear models associated with the multiple motion vectors may share the same values ​​of some linear model parameters. For non-limiting examples, when the current block has two motion vectors, two linear models are used for the two motion vectors, respectively, and the two linear models may have different scale factors α but the same offset β.

[0156] Various embodiments of the present disclosure may include a method performed by an encoder for encoding a current block into a video bitstream, the method including inverse processing of any part or all of the processing described for a decoder. Various embodiments of the present disclosure may include a method for encoding a current block of a streaming video, the method performed by one or more electronic devices (e.g., a streaming media player), including any part or all of the processing of a decoder and / or any part or all of the processing described for an encoder.

[0157] As required, the above operations may be combined or arranged in any number or order. Two or more of the steps and / or operations may be performed in parallel. The embodiments and implementations in the present disclosure may be used alone or in any order. In addition, each of the methods (or embodiments), the encoder and the decoder may be implemented by a processing circuit system (e.g., one or more processors or one or more integrated circuits). In one example, one or more processors execute a program stored in a non-transitory computer-readable medium. The embodiments in the present disclosure may be applied to luminance blocks or chrominance blocks. The term block may be interpreted as a prediction block, a coding block, or a coding unit, i.e., a CU. The term block here may also be used to refer to a transform block. In the following items, when it comes to block size, it may refer to block width or height, the maximum value of width and height, or the minimum value of width and height, or area size (width×height), and aspect ratio of the block (width: height, or height: width).

[0158] The techniques described above may be implemented as computer software using computer-readable instructions and physically stored in one or more computer-readable media. Fig.15 A computer system (1800) suitable for implementing certain aspects of the disclosed subject matter is shown.

[0159] Computer software may be encoded using any suitable machine code or computer language, which may be assembled, compiled, linked, or the like to create code comprising instructions, which may be executed directly by one or more computer central processing units (CPU), graphics processing units (GPU), etc., or through interpretation, microcode execution, or the like.

[0160] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smart phones, gaming devices, Internet of Things devices, etc.

[0161] Fig.15 The components for the computer system (1800) shown in the example are exemplary in nature and are not intended to imply any limitation on the scope of use or functionality of computer software implementing embodiments of the present disclosure. Nor should the configuration of components be interpreted as having any dependency or requirement relating to any one or combination of components shown in the exemplary embodiment of the computer system (1800).

[0162] The computer system (1800) may include certain human interface input devices. The input human interface devices may include one or more of the following (only one of each is depicted): keyboard (1801), mouse (1802), touch pad (1803), touch screen (1810), data gloves (not shown), joystick (1805), microphone (1806), scanner (1807), camera (1808).

[0163] The computer system (1800) may also include certain human-computer interface output devices. Such human-computer interface output devices may stimulate one or more senses 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 (such as: speakers (1809), headphones (not depicted)), visual output devices (such as screens (1810), including CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch screen input capabilities, each with or without tactile feedback capabilities, some of which may output two-dimensional visual outputs or output more than three-dimensional outputs through methods such as stereographic outputs; virtual reality glasses (not depicted), holographic displays, and smoke boxes (not depicted)) and printers (not depicted).

[0164] The computer system (1800) may also include human-accessible storage devices and their associated media, such as optical media including CD / DVD ROM / RW (1820) with CD / DVD etc. media (1821), thumb drives (1822), removable hard drives or solid-state drives (1823), traditional magnetic media such as tapes and floppy disks (not depicted), dedicated ROM / ASIC / PLD based devices such as security dongles (not depicted), etc.

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

[0166] The computer system (1800) may also include an interface (1854) to one or more communication networks (1855). The network may be, for example, wireless, wired, optical. The network may also be local, wide area, urban, vehicular and industrial, real-time, delay tolerant, etc. Examples of networks include: local area networks, such as Ethernet, wireless LAN; cellular networks, including GSM, 3G, 4G, 5G, LTE, etc.; television wired or wireless wide area digital networks, including cable television, satellite television, and terrestrial broadcast television; vehicular and industrial networks, including CAN bus, etc.

[0167] The above-mentioned human-machine interface devices, human-accessible storage devices, and network interfaces may be attached to the core ( 1840 ) of the computer system ( 1800 ).

[0168] The core (1840) may include one or more central processing units (CPUs) (1841), graphics processing units (GPUs) (1842), dedicated programmable processing units in the form of field programmable gate areas (FPGAs) (1843), hardware accelerators for specific tasks (1844), graphics adapters (1850), etc. These devices, along with read-only memory (ROM) (1845), random access memory (1846), internal large-capacity storage devices such as internal non-user accessible hard drives, SSDs, etc. (1847) may be connected via a system bus (1848). In some computer systems, the system bus (1848) may be accessed in the form of one or more physical plugs to enable expansion by additional CPUs, GPUs, etc. Peripheral devices may be attached to the core's system bus (1848) directly or via a peripheral bus (1849). In an example, a screen (1810) may be connected to a graphics adapter (1850). The architecture of the peripheral bus includes PCI, USB, etc.

[0169] The computer readable medium may have thereon computer code for performing various computer-implemented operations. The medium and computer code may be those specially designed and constructed for the purposes of the present disclosure, or the medium and computer code may be of a type well known and available to those skilled in the art of computer software.

[0170] Although the present disclosure has described several exemplary embodiments, there are changes, permutations, and various replacement equivalents that fall within the scope of the present disclosure. It will therefore be understood that those skilled in the art will be able to conceive of a variety of systems and methods that, although not explicitly shown or described herein, embody the principles of the disclosure and therefore fall within the spirit and scope of the disclosure.

Claims

1. A method for decoding a current block of a current frame in a coded video bitstream, the method comprising: Receiving the encoded video bitstream by a device, the device comprising a memory storing instructions and a processor in communication with the memory; determining, by the device, based on syntax elements signaled in the coded video bitstream, a prediction mode for predicting the current block based on a reference block, wherein the prediction mode comprises a linear equation; deriving, by the device, a scale factor for the current block from at least one of: a plurality of scale factors of neighboring blocks relative to the current block, or a stored library of scale factors; as well as The current block is reconstructed by the device based on the reference block and the identified scale factor according to the linear equation.

2. The method according to claim 1, wherein: The neighboring blocks relative to the current block include one or more adjacent neighboring blocks and one or more non-adjacent neighboring blocks.

3. The method according to claim 2, wherein: The one or more adjacent neighboring blocks include at least one of: one or more top-adjacent neighboring blocks, one or more left-adjacent neighboring blocks, or top-right neighboring blocks; and The one or more non-adjacent neighboring blocks include at least one of the following: an upper left neighboring block, one or more nearest top non-adjacent neighboring blocks, one or more nearest left non-adjacent neighboring blocks, one or more second nearest top non-adjacent neighboring blocks, or one or more second nearest left non-adjacent neighboring blocks.

4. The method according to claim 1, wherein: Deriving the scale factor for the current block includes: extracting a first flag based on the encoded video bitstream, the first flag indicating whether a scale factor for the current block is from a plurality of scale factors of the neighboring blocks or the stored scale factor library; Extracting a second flag based on the encoded video bitstream, the second flag indicating which scale factor in the stored scale factor library or the plurality of scale factors of the neighboring blocks is used as a scale factor for the current block; and A scale factor for the current block is derived based on the first flag and the second flag.

5. The method according to claim 1, wherein: The scale factor list includes a plurality of scale factors of the neighboring blocks and the stored scale factor library.

6. The method according to claim 5, wherein: Deriving the scale factor for the current block includes: In response to a previously coded block using a scale factor from the scale factor list, the scale factor for the previously coded block is derived as the scale factor for the current block without additional signaling.

7. The method according to claim 5, wherein: Deriving the scale factor of the current block includes: In response to the reference block using a scale factor from the scale factor list, the scale factor for the reference block is derived as the scale factor for the current block without additional signaling.

8. The method according to claim 5, wherein: The scale factors in the scale factor list have a scanning order in which adjacent neighboring blocks precede non-adjacent neighboring blocks.

9. The method according to claim 5, wherein: The scale factors in the scale factor list have the same scanning order as the MVPs in the motion vector predictor (MVP) list.

10. The method of claim 1, wherein: The stored scale factor library includes all scale factors for previously coded blocks in one of a current frame, a current tile, a current slice, and a current super block.

11. The method according to claim 1, wherein: Each of the stored scale factors is based on a reference frame corresponding to a reference block of a previously coded block in one of a current frame, a current tile, a current slice, and a current superblock; as well as The scale factor is identified from the library of stored scale factors whose reference frame matches the reference frame of the reference block corresponding to the current block.

12. The method of claim 1, wherein: In response to the stored scale factor library being full, the stored scale factor library is updated according to a first-in-first-out (FIFO) model.

13. The method according to claim 1, wherein: Deriving the scale factor for the current block includes: A scaling factor for the current block is derived according to a predefined configuration.

14. An apparatus for decoding a current block of a current frame in a coded video bitstream, the apparatus comprising: a memory for storing instructions; as well as A processor in communication with the memory, wherein when the processor executes the instructions, the processor is configured to cause the apparatus to perform the method of any one of claims 1 to 13.

15. A non-transitory computer-readable storage medium storing instructions, wherein: When a processor executes the instructions, the instructions are configured to cause the processor to perform the method of any one of claims 1 to 13.

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