Method and apparatus for chroma motion compensation using adaptive cross-component filtering

Abstract

Methods, apparatus, and non-transitory computer-readable storage media for video decoding and encoding are provided. In a method for video decoding, a decoder may obtain a plurality of first motion compensation sample points of a first channel and a plurality of second motion compensation sample points of a second channel for a current inter-frame coding block, obtain a nonlinear filter, and obtaining a plurality of filtered motion compensation samples for the first channel based on the non-linear filter, the first motion compensation samples for the first channel, and the second motion compensation samples for the second channel.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is filed based on and claims priority to U.S. Provisional Application No. 63 / 358,524, filed on July 5, 2022, entitled “Methods and apparatus on chromamotion compensation using adaptive cross-component filtering,” the entire contents of which are incorporated by reference for all purposes. Technical Field

[0003] The present disclosure relates to video coding and compression, and in particular, but not limited to, to methods and apparatus for improving coding efficiency of inter blocks that apply cross-component filtering to generate prediction samples for chroma components of the blocks. Background Art

[0004] Various video codec technologies can be used to compress video data. Video coding is performed according to one or more video codec standards. For example, video codec standards include Versatile Video Codec (VVC), High Efficiency Video Codec (H.265 / HEVC), Advanced Video Codec (H.264 / AVC), Moving Picture Experts Group (MPEG) codec, etc. Video codecs typically use prediction methods (e.g., inter-frame prediction, intra-frame prediction, etc.) that exploit redundancy present in video images or sequences. An important goal of video coding technology is to compress video data into a form that uses a lower bit rate while avoiding or minimizing the degradation of video quality.

[0005] The first version of the VVC standard was completed in July 2020, which provides approximately 50% bitrate savings or equivalent perceptual quality compared to the previous generation video codec standard HEVC. Although the VVC standard provides significant codec improvements over its predecessor, there is evidence that superior codec efficiency can be achieved by adopting additional codec tools. Recently, the Joint Video Exploration Team (JVET), in collaboration with ITU-TVECG and ISO / IEC MPEG, began exploring advanced technologies that can significantly improve codec efficiency over VVC. In April 2021, a software code base named Enhanced Compression Model (ECM) was established for future video codec exploration work. The ECM reference software is based on the VVC Test Model (VTM) developed by JVET for VVC, and further extends and / or improves several existing modules (e.g., intra / inter prediction, transform, loop filter, etc.). In the future, any new codec tools beyond the VVC standard will need to be integrated into the ECM platform and tested using the JVET Common Test Conditions (CTC). Summary of the invention

[0006] This disclosure provides examples of techniques related to improving encoding and decoding efficiency of inter blocks.

[0007] According to a first aspect of the present disclosure, a method for video decoding of an inter-frame coding block is provided. In the method, a decoder may obtain a plurality of first motion compensation samples of a first channel and a plurality of second motion compensation samples of a second channel for a current inter-frame coding block, obtain a non-linear filter, and obtain a plurality of filtered motion compensation samples of the first channel based on the non-linear filter, the first motion compensation samples of the first channel, and the second motion compensation samples of the second channel.

[0008] According to a second aspect of the present disclosure, a method for video encoding of an inter-frame coding block is provided. In the method, an encoder may obtain a plurality of first motion compensation samples of a first channel and a plurality of second motion compensation samples of a second channel for a current inter-frame coding block, obtain a non-linear filter, and obtain a plurality of filtered motion compensation samples of the first channel based on the non-linear filter, the first motion compensation samples of the first channel, and the second motion compensation samples of the second channel.

[0009] According to a third aspect of the present disclosure, a device for video decoding is provided. The device may include one or more processors and a memory coupled to the one or more processors and configured to store instructions executable by the one or more processors. In addition, the one or more processors are configured to perform the method according to the first aspect when executing the instructions.

[0010] According to a fourth aspect of the present disclosure, a device for video encoding is provided. The device may include one or more processors and a memory coupled to the one or more processors and configured to store instructions executable by the one or more processors. In addition, the one or more processors are configured to perform the method according to the second aspect when executing the instructions.

[0011] According to a fifth aspect of the present disclosure, a non-temporary computer-readable storage medium for storing computer-executable instructions is provided. When the computer-executable instructions are executed by one or more computer processors, the one or more computer processors perform the method according to the first aspect or the second aspect based on the bit stream.

[0012] According to a sixth aspect of the present disclosure, there is provided a non-transitory computer-readable storage medium for storing a bit stream to be decoded by the method according to the first aspect.

[0013] According to a seventh aspect of the present disclosure, there is provided a non-transitory computer-readable storage medium for storing a bit stream generated by the method according to the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] A more specific description of examples of the present disclosure will be presented by reference to specific examples shown in the accompanying drawings. Given that these drawings depict only some examples and are therefore not to be considered limiting in scope, the examples will be described and explained with additional specificity and detail through the use of the accompanying drawings.

[0015] Figure 1A is a block diagram illustrating a system for encoding and decoding video blocks according to some examples of the present disclosure.

[0016] Figure 1B is a block diagram of an encoder according to some examples of the present disclosure.

[0017] Figure 1C-1F is a block diagram showing how to recursively partition a frame into multiple video blocks of different sizes and shapes according to some examples of the present disclosure.

[0018] Figure 1G is a block diagram illustrating an exemplary video encoder according to some examples of the present disclosure.

[0019] Figure 2A is a block diagram of a decoder according to some examples of the present disclosure.

[0020] Figure 2B is a block diagram illustrating an exemplary video decoder according to some examples of the present disclosure.

[0021] Figure 3A is a schematic diagram illustrating block partitioning in a multi-type tree structure according to some examples of the present disclosure.

[0022] Figure 3B is a schematic diagram illustrating block partitioning in a multi-type tree structure according to some examples of the present disclosure.

[0023] Figure 3C is a schematic diagram illustrating block partitioning in a multi-type tree structure according to some examples of the present disclosure.

[0024] Figure 3D is a schematic diagram illustrating block partitioning in a multi-type tree structure according to some examples of the present disclosure.

[0025] Figure 3E is a schematic diagram illustrating block partitioning in a multi-type tree structure according to some examples of the present disclosure.

[0026] Figure 4 Some examples according to the present disclosure are shown. x is the level value of MV and d y is an example of a vertical value of MV.

[0027] Figure 5 An example is shown in which an MV has a fractional value and an interpolation filter is applied to generate corresponding prediction samples at fractional sample locations according to some examples of the present disclosure.

[0028] FIG. 6 shows examples of two diamond filter shapes according to some examples of the present disclosure.

[0029] Figure 7 A subsampled 1-D Laplacian computation applied to gradient computation in all directions according to some examples of the present disclosure is shown.

[0030] Figure 8 The filtering operation in CC-ALF implemented by applying a diamond filter to the luma channel according to some examples of the present disclosure is shown.

[0031] Fig. 9 is a block diagram showing a video encoder when CC-MCP according to the present disclosure is applied.

[0032] Fig.10 The content of this disclosure is received by Fig. 9 Block diagram of a decoder for the bit stream produced by an encoder.

[0033] Fig.11 is a schematic diagram illustrating a computing environment coupled with a user interface according to some examples of the present disclosure.

[0034] Fig.12 is a flowchart illustrating a method for video decoding according to an example of the present disclosure.

[0035] Fig.13 is a flowchart illustrating steps for deriving coefficients of a non-linear filter in a method for video decoding according to an example of the present disclosure.

[0036] Fig.14 is a flowchart illustrating a method for video encoding according to an example of the present disclosure.

[0037] Fig.15 A flowchart illustrating steps for deriving coefficients of a non-linear filter in a method for video encoding according to an example of the present disclosure.

[0038] Specific implementation

[0039] Reference will now be made in detail to specific implementations, examples of which are shown in the accompanying drawings. In the following detailed description, many non-limiting specific details are set forth to aid in understanding the subject matter presented herein. However, it will be apparent to one of ordinary skill in the art that various alternatives may be used. For example, it will be apparent to one of ordinary skill in the art that the subject matter presented herein may be implemented on many types of electronic devices having digital video capabilities.

[0040] The terms used in this disclosure are only used for the purpose of describing specific embodiments and are not intended to limit the disclosure. Unless otherwise clearly indicated throughout the disclosure, the singular forms of "one", "said" and "the" in this disclosure and the appended claims are also intended to include plural forms. It should also be understood that the term "and / or" used in this disclosure refers to and includes one or any or all possible combinations of the listed multiple associated items.

[0041] References throughout this specification to "one embodiment," "an embodiment," "an example," "some embodiments," "some examples," or similar language mean that the particular features, structures, or characteristics described are included in at least one embodiment or example. Unless explicitly stated otherwise, features, structures, elements, or characteristics described in conjunction with one or some embodiments are also applicable to other embodiments.

[0042] Unless otherwise expressly stated, throughout the present disclosure, the terms "first", "second", "third", etc. are used only as references to related elements (e.g., devices, components, compositions, steps, etc.), without implying any spatial or temporal order. For example, "first device" and "second device" may refer to two separately formed devices, or two parts, components, or operating states of the same device, and may be named arbitrarily.

[0043] The terms "module", "sub-module", "circuit", "sub-circuit", "circuitry", "sub-circuitry", "unit", or "sub-unit" may include a memory (shared, dedicated, or a memory group) that stores code or instructions that can be executed by one or more processors. A module may include one or more circuits with or without stored code or instructions. A module or circuit may include one or more components that are directly or indirectly connected. These components may or may not be physically attached to each other, or may be adjacent to each other.

[0044] As used herein, the terms "if" or "when..." may be understood to mean "at..." or "in response to...", depending on the context. If these terms appear in the claims, they may not indicate that the associated limitation or feature is conditional or optional. For example, a method may include the following steps: i) when condition X exists or if condition X exists, perform function or action X', and ii) when condition Y exists or if condition Y exists, perform function or action Y'. The method may be implemented with the ability to perform function or action X' and the ability to perform function or action Y'. Therefore, both functions X' and Y' may be performed at different times on multiple executions of the method.

[0045] A unit or module may be implemented purely by software, purely by hardware, or by a combination of hardware and software. In a pure software implementation, for example, a unit or module may include functionally related code blocks or software components that are linked together directly or indirectly to perform a specific function.

[0046] Figure 1A is a block diagram illustrating an exemplary system 10 for encoding and decoding video blocks in parallel according to some embodiments of the present disclosure. Figure 1A As shown in , system 10 includes a source device 12 that generates and encodes video data to be later decoded by a destination device 14. Source device 12 and destination device 14 may include any of a wide variety of electronic devices, including desktop or laptop computers, tablet computers, smart phones, set-top boxes, digital televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, etc. In some implementations, source device 12 and destination device 14 are equipped with wireless communication capabilities.

[0047] In some embodiments, the target device 14 may receive the encoded video data to be decoded via the link 16. The link 16 may include any type of communication medium or device capable of moving the encoded video data from the source device 12 to the target device 14. In one example, the link 16 may include a communication medium that enables the source device 12 to send the encoded video data directly to the target device 14 in real time. The encoded video data may be modulated according to a communication standard (e.g., a wireless communication protocol) and sent to the target device 14. The communication medium may include any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form a portion of a packet-based network (e.g., a local area network, a wide area network, or a global network such as the Internet). The communication medium may include a router, a switch, a base station, or any other device that may be beneficial to facilitate communication from the source device 12 to the target device 14.

[0048] In some other embodiments, the encoded video data may be sent from the output interface 22 to the storage device 32. The encoded video data in the storage device 32 may then be accessed by the target device 14 via the input interface 28. The storage device 32 may include any of a variety of distributed or locally accessed data storage media, such as a hard drive, a Blu-ray disc, a digital versatile disc (DVD), a compact disc read-only memory (CD-ROM), a flash memory, a volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data. In another example, the storage device 32 may correspond to a file server or another intermediate storage device that may hold the encoded video data generated by the source device 12. The target device 14 may access the stored video data from the storage device 32 via streaming or downloading. The file server may be any type of computer capable of storing encoded video data and sending the encoded video data to the target device 14. Exemplary file servers include a network server (e.g., for a website), a file transfer protocol (FTP) server, a network attached storage (NAS) device, or a local disk drive. Target device 14 may access the encoded video data through any standard data connection suitable for accessing encoded video data stored on a file server, including a wireless channel (e.g., a Wireless Fidelity (Wi-Fi) connection), a wired connection (e.g., a Digital Subscriber Line (DSL), a cable modem, etc.), or a combination of both wireless channels and wired connections. The transmission of the encoded video data from storage device 32 may be a streaming transmission, a download transmission, or a combination of both streaming and download transmissions.

[0049] like Figure 1A As shown in , source device 12 includes video source 18, video encoder 20 and output interface 22. Video source 18 may include sources such as or a combination of such sources: a video capture device (e.g., a camera), a video archive containing previously captured video, a video feed interface for receiving video from a video content provider, and / or a computer graphics system for generating computer graphics data as source video. As an example, if video source 18 is a camera of a security monitoring system, source device 12 and target device 14 may form a camera phone or a video phone. However, the embodiments described in this application may be generally applicable to video encoding and decoding, and may be applied to wireless and / or wired applications.

[0050] The captured, pre-captured, or computer-generated video may be encoded by the video encoder 20. The encoded video data may be sent directly to the target device 14 via the output interface 22 of the source device 12. The encoded video data may also (or alternatively) be stored on a storage device 32 for later access by the target device 14 or other device for decoding and / or playback. The output interface 22 may further include a modem and / or a transmitter.

[0051] Target device 14 includes input interface 28, video decoder 30, and display device 34. Input interface 28 may include a receiver and / or a modem and receives encoded video data via link 16. The encoded video data transmitted via link 16 or provided on storage device 32 may include various syntax elements generated by video encoder 20 for use by video decoder 30 in decoding the video data. Such syntax elements may be included within the encoded video data sent over a communication medium, stored on a storage medium, or stored on a file server.

[0052] In some implementations, the target device 14 may include a display device 34, which may be an integrated display device or an external display device configured to communicate with the target device 14. The display device 34 displays the decoded video data to a user, and may include any of a variety of display devices, such as a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.

[0053] The video encoder 20 and the video decoder 30 can operate according to a proprietary standard or an industry standard (e.g., VVC, HEVC, Part 10 of MPEG-4, AVC) or an extension of such a standard. It should be understood that the present application is not limited to a specific video encoding / decoding standard and can be applied to other video encoding / decoding standards. It is generally believed that the video encoder 20 of the source device 12 can be configured to encode the video data according to any of these current standards or future standards. Similarly, it is also generally believed that the video decoder 30 of the target device 14 can be configured to decode the video data according to any of these current standards or future standards.

[0054] The video encoder 20 and the video decoder 30 can be implemented as any of a variety of suitable encoder and / or decoder circuits, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic devices, software, hardware, firmware, or any combination thereof. When partially implemented in software, the electronic device can store instructions for the software in a suitable non-transitory computer-readable medium, and use one or more processors to execute the instructions in the hardware to perform the video encoding / decoding operations disclosed in the present disclosure. Each of the video encoder 20 and the video decoder 30 can be included in one or more encoders or decoders, and either of the encoders or decoders can be integrated as part of a combined encoder / decoder (CODEC) in the corresponding device.

[0055] Like HEVC, VVC is built on a block-based hybrid video coding framework. Figure 1B 1 is a block diagram illustrating a block-based video encoder according to some embodiments of the present disclosure. In the encoder 100, the input video signal is processed block by block in a coding unit (CU). The encoder 100 may be as follows: Figure 1A The video encoder 20 shown in . In VTM-1.0, a CU can be as high as 128x128 pixels. However, unlike HEVC, which is based only on quadtree partition blocks, in VVC, a coding tree unit (CTU) is partitioned into CUs to adapt to local characteristics based on quadtree / binary / ternary tree changes. In addition, the concept of multiple partition unit types in HEVC is removed, that is, the separation of CU, prediction unit (PU), and transform unit (TU) no longer exists in VVC; instead, each CU is always used as a basic unit for prediction and transformation without further partitioning. In a multi-type tree structure, a CTU is first divided by a quadtree structure. Then, each quadtree leaf node can be further divided by a binary tree and a ternary tree structure.

[0056] Figure 3A-3E is a schematic diagram illustrating multiple types of tree splitting modes according to some embodiments of the present disclosure. Figure 3A-3E Five segmentation types are shown, including four-element segmentation ( Figure 3A ), vertical binary segmentation ( Figure 3B ), horizontal binary segmentation ( Figure 3C ), vertical ternary segmentation ( Figure 3D ) and horizontal ternary segmentation ( Figure 3E ).

[0057] For each given video block, spatial prediction and / or temporal prediction can be performed. Spatial prediction (or "intra-frame prediction") uses pixels from samples of already encoded neighboring blocks (which are called reference samples) in the same video picture / slice to predict the current video block. Spatial prediction reduces the spatial redundancy inherent in the video signal. Temporal prediction (also known as "inter-frame prediction" or "motion compensated prediction") uses reconstructed pixels from already encoded video pictures to predict the current video block. Temporal prediction reduces the temporal redundancy inherent in the video signal. The temporal prediction signal for a given CU is typically transmitted by signaling one or more motion vectors (MVs) indicating the amount and direction of motion between the current CU and its temporal reference. In addition, if multiple reference pictures are supported, a reference picture index is additionally sent, which is used to identify which reference picture in the reference picture storage stores the temporal prediction signal.

[0058] After spatial and / or temporal prediction, the intra / inter mode decision circuit 121 in the encoder 100 selects the best prediction mode, for example based on a rate-distortion optimization method. The block predictor 120 is then subtracted from the current video block; and the resulting prediction residual is decorrelated using the transform circuit 102 and the quantization circuit 104. The resulting quantized residual coefficients are inverse quantized by the inverse quantization circuit 116 and inverse transformed by the inverse transform circuit 118 to form a reconstructed residual, which is then added back to the prediction block to form a reconstructed signal for the CU. In addition, in-loop filtering 115 (such as a deblocking filter, sample adaptive offset (SAO) and / or adaptive loop filter (ALF)) can be applied to the reconstructed CU before it is placed in the reference picture storage of the picture buffer 117 and used to encode and decode future video blocks. To form the output video bitstream 114, the coding mode (inter or intra), prediction mode information, motion information, and quantized residual coefficients are all sent to the entropy coding unit 106 to be further compressed and packed to form a bitstream.

[0059] For example, deblocking filters are available in AVC, HEVC, and now the current version of VVC. In HEVC, an additional loop filter called SAO is defined to further improve the coding efficiency. In the current version of the VVC standard, another loop filter called ALF is being actively studied and has a good chance of being included in the final standard.

[0060] These loop filter operations are optional. Performing these operations helps improve codec efficiency and visual quality. They can also be turned off as a decision presented by the encoder 100 to save computational complexity.

[0061] It should be noted that if the encoder 100 turns on these filter options, intra prediction is typically based on unfiltered reconstructed pixels, while inter prediction is based on filtered reconstructed pixels.

[0062] Figure 2A is a block diagram illustrating a block-based video decoder 200 that can be used in conjunction with many video codec standards. The decoder 200 is similar to the one present in Figure 1B The block-based video decoder 200 may be as follows: Figure 1A . In the decoder 200, an incoming video bitstream 201 is first decoded by entropy decoding 202 to derive quantized coefficient levels and prediction related information. The quantized coefficient levels are then processed by inverse quantization 204 and inverse transform 206 to obtain reconstructed prediction residuals. The block predictor mechanism implemented in the intra / inter mode selector 212 is configured to perform intra prediction 208 or motion compensation 210 based on the decoded prediction information. A set of unfiltered reconstructed pixels is obtained by summing the reconstructed prediction residuals from the inverse transform 206 and the prediction output generated by the block predictor mechanism using a summer 214.

[0063] The reconstructed block may further pass through a loop filter 209 before it is stored in a picture buffer 213 acting as a reference picture storage. The reconstructed video in the picture buffer 213 may be sent to drive a display device, as well as to predict future video blocks. With the loop filter 209 turned on, filtering operations are performed on these reconstructed pixels to derive a final reconstructed video output 222.

[0064] Figure 1G is a block diagram illustrating another exemplary video encoder 20 according to some embodiments described in the present application. The video encoder 20 can perform intra-frame prediction coding and inter-frame prediction coding on video blocks within a video frame. Intra-frame prediction coding relies on spatial prediction to reduce or remove spatial redundancy in video data within a given video frame or picture. Inter-frame prediction coding relies on temporal prediction to reduce or remove temporal redundancy in video data within adjacent video frames or pictures of a video sequence. It should be noted that in the field of video coding and decoding, the term "frame" can be used as a synonym for the term "image" or "picture".

[0065] like Figure 1GAs shown in FIG. 1 , the video encoder 20 includes a video data memory 40, a prediction processing unit 41, a decoded picture buffer (DPB) 64, an adder 50, a transform processing unit 52, a quantization unit 54, and an entropy coding unit 56. The prediction processing unit 41 further includes a motion estimation unit 42, a motion compensation unit 44, a segmentation unit 45, an intra-frame prediction processing unit 46, and an intra-frame block copy (BC) unit 48. In some embodiments, the video encoder 20 also includes an inverse quantization unit 58, an inverse transform processing unit 60, and an adder 62 for video block reconstruction. A loop filter 63 such as a deblocking filter can be located between the adder 62 and the DPB 64 to filter the block boundary to remove the block effect from the reconstructed video. In addition to the deblocking filter, another loop filter (e.g., a sample adaptive offset (SAO) filter and / or an adaptive loop filter (ALF)) can also be used to filter the output of the adder 62. In some examples, the loop filter can be omitted, and the decoded video block can be directly provided to the DPB 64 by the adder 62. Video encoder 20 may take the form of a fixed or programmable hardware unit, or may be distributed among one or more of the illustrated fixed or programmable hardware units.

[0066] Video data memory 40 may store video data to be encoded by components of video encoder 20. Figure 1A The video source 18 shown obtains video data in the video data memory 40. The DPB 64 is a buffer that stores reference video data (e.g., reference frames or pictures) for use by the video encoder 20 (e.g., in intra-frame or inter-frame prediction coding mode) when encoding the video data. The video data memory 40 and the DPB 64 can be formed by any of a variety of memory devices. In various examples, the video data memory 40 can be on-chip with other components of the video encoder 20, or off-chip relative to those components.

[0067] like Figure 1GAs shown in , after receiving the video data, the segmentation unit 45 within the prediction processing unit 41 segments the video data into video blocks. This segmentation may also include segmenting the video frame into strips, tiles (e.g., a set of video blocks) or other larger coding units (CUs) according to a predefined splitting structure associated with the video data (e.g., a quadtree (QT) structure). A video frame is or can be viewed as a two-dimensional array or matrix of samples having sample values. The samples in the array may also be referred to as pixels or picture elements (pel). The number of samples in the horizontal and vertical directions (or axes) of the array or picture defines the size and / or resolution of the video frame. For example, a video frame may be divided into multiple video blocks by using QT segmentation. A video block is again or may be viewed as a two-dimensional array or matrix of samples having sample values, but its dimension is smaller than the dimension of a video frame. The number of samples in the horizontal and vertical directions (or axes) of a video block defines the size of the video block. The video block may be further partitioned into one or more block partitions or sub-blocks (which may again form blocks) by, for example, iteratively using QT partitioning, binary tree (BT) partitioning or ternary tree (TT) partitioning or any combination thereof. It should be noted that the term "block" or "video block" used herein may be a portion of a frame or picture, in particular a rectangular (square or non-square) portion. With reference to, for example, HEVC and VVC, a block or video block may be or correspond to a coding tree unit (CTU), a CU, a prediction unit (PU) or a transform unit (TU) and / or may be or correspond to a corresponding block (e.g., a coding tree block (CTB), a coding block (CB), a prediction block (PB) or a transform block (TB)) and / or a sub-block.

[0068] The prediction processing unit 41 may select one of a plurality of feasible prediction coding modes for the current video block based on the error results (e.g., coding rate and distortion level), such as one of one or more inter-frame prediction coding modes in a plurality of intra-frame prediction coding modes. The prediction processing unit 41 may provide the resulting intra-frame prediction coding block or inter-frame prediction coding block to the adder 50 to generate a residual block, and to the adder 62 to reconstruct the coding block for subsequent use as part of a reference frame. The prediction processing unit 41 also provides syntax elements (e.g., motion vectors, intra-frame mode indicators, partition information, and other such syntax information) to the entropy coding unit 56.

[0069] To select an appropriate intra-prediction coding mode for the current video block, intra-prediction processing unit 46 within prediction processing unit 41 may perform intra-prediction coding of the current video block in relation to one or more neighboring blocks in the same frame as the current block to be encoded to provide spatial prediction. Motion estimation unit 42 and motion compensation unit 44 within prediction processing unit 41 may perform inter-prediction coding of the current video block in relation to one or more prediction blocks in one or more reference frames to provide temporal prediction. Video encoder 20 may perform multiple encoding passes, for example, to select an appropriate coding mode for each block of video data.

[0070] In some embodiments, motion estimation unit 42 determines an inter-prediction mode for a current video frame by generating a motion vector according to a predetermined pattern within a sequence of video frames, the motion vector indicating the displacement of a video block within the current video frame relative to a prediction block within a reference video frame. Motion estimation performed by motion estimation unit 42 is the process of generating a motion vector that estimates the motion of a video block. For example, a motion vector may indicate the displacement of a video block within a current video frame or picture relative to a prediction block within a reference frame associated with a current block being encoded within the current frame. The predetermined pattern may designate a video frame in a sequence as a P frame or a B frame. Intra BC unit 48 may determine a vector (e.g., a block vector) for intra BC coding in a manner similar to the motion vector determined by motion estimation unit 42 for inter prediction, or may utilize motion estimation unit 42 to determine a block vector.

[0071] In terms of pixel differences, the prediction block for the video block may be or may correspond to a block or reference block of a reference frame that is considered to closely match the video block to be encoded, and the pixel difference may be determined by the sum of absolute differences (SAD), the sum of squared differences (SSD), or other difference metrics. In some embodiments, the video encoder 20 may calculate values ​​for sub-integer pixel positions of the reference frames stored in the DPB 64. For example, the video encoder 20 may interpolate values ​​for quarter-pixel positions, eighth-pixel positions, or other fractional pixel positions of the reference frame. Thus, the motion estimation unit 42 may perform a motion search relative to full pixel positions and fractional pixel positions and output a motion vector with fractional pixel accuracy.

[0072] Motion estimation unit 42 calculates a motion vector for a video block in an inter-prediction coded frame by comparing the position of the video block to the position of a prediction block of a reference frame selected from a first reference frame list (list 0) or a second reference frame list (list 1), each of which identifies one or more reference frames stored in DPB 64. Motion estimation unit 42 sends the calculated motion vector to motion compensation unit 44 and then to entropy encoding unit 56.

[0073] The motion compensation performed by the motion compensation unit 44 may involve obtaining or generating a prediction block based on the motion vector determined by the motion estimation unit 42. After receiving the motion vector for the current video block, the motion compensation unit 44 may locate the prediction block pointed to by the motion vector in one of the reference frame lists, retrieve the prediction block from the DPB 64, and forward the prediction block to the adder 50. The adder 50 then forms a residual video block of pixel difference values ​​by subtracting the pixel values ​​of the prediction block provided by the motion compensation unit 44 from the pixel values ​​of the current video block being encoded. The pixel difference values ​​forming the residual video block may include luminance component differences or chrominance component differences or both. The motion compensation unit 44 may also generate syntax elements associated with the video block of the video frame for use by the video decoder 30 when decoding the video block of the video frame. The syntax elements may include, for example, syntax elements defining a motion vector for identifying a prediction block, any flag indicating a prediction mode, or any other syntax information described herein. It should be noted that the motion estimation unit 42 and the motion compensation unit 44 may be highly integrated, but are described separately for conceptual purposes.

[0074] In some embodiments, the intra BC unit 48 may generate vectors and obtain prediction blocks in a manner similar to that described above in conjunction with the motion estimation unit 42 and the motion compensation unit 44, but these prediction blocks are in the same frame as the current block being encoded, and these vectors are referred to as block vectors rather than motion vectors. Specifically, the intra BC unit 48 may determine the intra prediction mode to be used to encode the current block. In some examples, the intra BC unit 48 may encode the current block using various intra prediction modes, for example, during separate encoding passes, and test their performance through rate-distortion analysis. Next, the intra BC unit 48 may select a suitable intra prediction mode to use among the various tested intra prediction modes and generate an intra mode indicator accordingly. For example, the intra BC unit 48 may calculate rate-distortion values ​​for the various tested intra prediction modes using rate-distortion analysis, and select an intra prediction mode with the best rate-distortion characteristic among the tested modes as a suitable intra prediction mode to use. The rate-distortion analysis generally determines the amount of distortion (or error) between a coded block and the original uncoded block that was encoded to produce the coded block, as well as the bit rate (i.e., the number of bits) used to produce the coded block. Intra BC unit 48 may calculate ratios based on the distortion and rate for the various coded blocks to determine which intra-prediction mode exhibits the best rate-distortion value for the block.

[0075] In other examples, intra BC unit 48 may use, in whole or in part, motion estimation unit 42 and motion compensation unit 44 to perform such functions for intra BC prediction in accordance with embodiments described herein. In either case, for intra block copying, the prediction block may be a block that is considered to closely match the block to be encoded in terms of pixel differences, which may be determined by SAD, SSD, or other difference metrics, and identifying the prediction block may include calculating values ​​for sub-integer pixel positions.

[0076] Regardless of whether the prediction block is from the same frame according to intra-frame prediction or from a different frame according to inter-frame prediction, video encoder 20 can form a residual video block by subtracting the pixel values ​​of the prediction block from the pixel values ​​of the current video block being encoded. The pixel difference values ​​forming the residual video block may include both luma component differences and chroma component differences.

[0077] As an alternative to the inter-frame prediction performed by the motion estimation unit 42 and the motion compensation unit 44 or the intra-frame block copy prediction performed by the intra BC unit 48 as described above, the intra-frame prediction processing unit 46 can perform intra-frame prediction on the current video block. Specifically, the intra-frame prediction processing unit 46 can determine the intra-frame prediction mode for encoding the current block. To this end, the intra-frame prediction processing unit 46 can use various intra-frame prediction modes to encode the current block, for example, during separate encoding passes, and the intra-frame prediction processing unit 46 (or in some examples, the mode selection unit) can select a suitable intra-frame prediction mode from the tested intra-frame prediction modes to use. The intra-frame prediction processing unit 46 can provide information indicating the intra-frame prediction mode selected for the block to the entropy coding unit 56. The entropy coding unit 56 can encode the information indicating the selected intra-frame prediction mode into the bitstream.

[0078] After prediction processing unit 41 determines a prediction block for the current video block via inter-prediction or intra-prediction, adder 50 forms a residual video block by subtracting the prediction block from the current video block. The residual video data in the residual block may be included in one or more TUs and provided to transform processing unit 52. Transform processing unit 52 transforms the residual video data into residual transform coefficients using a transform (e.g., a discrete cosine transform (DCT) or a conceptually similar transform).

[0079] Transform processing unit 52 may send the resulting transform coefficients to quantization unit 54. Quantization unit 54 quantizes the transform coefficients to further reduce the bit rate. The quantization process may also reduce the bit depth associated with some or all of the coefficients. The degree of quantization may be modified by adjusting a quantization parameter. In some examples, quantization unit 54 may then perform a scan on the matrix including the quantized transform coefficients. Alternatively, entropy encoding unit 56 may perform the scan.

[0080] After quantization, entropy coding unit 56 entropy encodes the quantized transform coefficients into a video bitstream using, for example, context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), syntax-based context adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding, or another entropy coding method or technique. The encoded bitstream may then be sent to a video bitstream such as a Figure 1A The video decoder 30 shown, or archived as Figure 1A The video frame may be stored in storage device 32 as shown for later transmission to or retrieval by video decoder 30. Entropy encoding unit 56 may also entropy encode motion vectors and other syntax elements for the current video frame being encoded.

[0081] Inverse quantization unit 58 and inverse transform processing unit 60 apply inverse quantization and inverse transform, respectively, to reconstruct the residual video block in the pixel domain for use in generating reference blocks for predicting other video blocks. As noted above, motion compensation unit 44 may generate a motion compensated prediction block from one or more reference blocks of a frame stored in DPB 64. Motion compensation unit 44 may also apply one or more interpolation filters to the prediction block to calculate sub-integer pixel values ​​for use in motion estimation.

[0082] Adder 62 adds the reconstructed residual block to the motion compensated prediction block generated by motion compensation unit 44 to generate a reference block for storage in DPB 64. The reference block may then be used as a prediction block by intra BC unit 48, motion estimation unit 42, and motion compensation unit 44 to inter-predict another video block in a subsequent video frame.

[0083] Figure 2B 1 is a block diagram showing another exemplary video decoder 30 according to some embodiments of the present application. The video decoder 30 includes a video data memory 79, an entropy decoding unit 80, a prediction processing unit 81, an inverse quantization unit 86, an inverse transform processing unit 88, an adder 90, and a DPB 92. The prediction processing unit 81 further includes a motion compensation unit 82, an intra-frame prediction unit 84, and an intra-frame BC unit 85. The video decoder 30 may perform the above-mentioned operations in combination with the above-mentioned operations. Figure 1G The encoding process is substantially the inverse of the decoding process described with respect to video encoder 20. For example, motion compensation unit 82 may generate prediction data based on motion vectors received from entropy decoding unit 80, and intra-prediction unit 84 may generate prediction data based on intra-prediction mode indicators received from entropy decoding unit 80.

[0084] In some examples, units of the video decoder 30 may be tasked to perform embodiments of the present application. In addition, in some examples, embodiments of the present disclosure may be dispersed in one or more of the units of the video decoder 30. For example, the intra BC unit 85 may perform embodiments of the present application alone or in combination with other units of the video decoder 30 (e.g., the motion compensation unit 82, the intra prediction unit 84, and the entropy decoding unit 80). In some examples, the video decoder 30 may not include the intra BC unit 85, and the functions of the intra BC unit 85 may be performed by other components of the prediction processing unit 81 (e.g., the motion compensation unit 82).

[0085] The video data memory 79 may store video data, such as an encoded video bitstream, to be decoded by other components of the video decoder 30. The video data stored in the video data memory 79 may be obtained, for example, from the storage device 32, from a local video source (e.g., a camera), via a wired or wireless network communication of video data, or by accessing a physical data storage medium (e.g., a flash drive or hard disk). The video data memory 79 may include a coded picture buffer (CPB) that stores encoded video data from an encoded video bitstream. The DPB 92 of the video decoder 30 stores reference video data for use by the video decoder 30 when decoding the video data (e.g., in an intra-frame or inter-frame prediction coding mode). The video data memory 79 and the DPB 92 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM) (including synchronous DRAM (SDRAM)), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. For illustrative purposes, the video data memory 79 and the DPB 92 are shown in FIG. Figure 2B 9 as two different components of the video decoder 30. However, it will be apparent to those skilled in the art that the video data memory 79 and the DPB 92 can be provided by the same memory device or a separate memory device. In some examples, the video data memory 79 can be on-chip with other components of the video decoder 30, or off-chip relative to those components.

[0086] During the decoding process, the video decoder 30 receives an encoded video bitstream representing video blocks of an encoded video frame and associated syntax elements. The video decoder 30 may receive syntax elements at the video frame level and / or the video block level. The entropy decoding unit 80 of the video decoder 30 entropy decodes the bitstream to generate quantization coefficients, motion vectors or intra-frame prediction mode indicators, and other syntax elements. The entropy decoding unit 80 then forwards the motion vectors or intra-frame prediction mode indicators, and other syntax elements to the prediction processing unit 81.

[0087] When a video frame is encoded as an intra-prediction coded (I) frame or for intra-coded prediction blocks in other types of frames, the intra-prediction unit 84 of the prediction processing unit 81 can generate prediction data for a video block of the current video frame based on the intra-prediction mode transmitted by the signal and reference data from a previously decoded block of the current frame.

[0088] When the video frame is encoded as an inter-frame prediction coding (i.e., B or P) frame, the motion compensation unit 82 of the prediction processing unit 81 generates one or more prediction blocks for the video block of the current video frame based on the motion vector and other syntax elements received from the entropy decoding unit 80. Each of the prediction blocks can be generated from a reference frame in one of the reference frame lists. The video decoder 30 can construct the reference frame lists, i.e., List 0 and List 1, based on the reference frames stored in the DPB 92 using a default construction technique.

[0089] In some examples, when a video block is encoded according to the intra BC mode described herein, intra BC unit 85 of prediction processing unit 81 generates a prediction block for the current video block based on the block vector and other syntax elements received from entropy decoding unit 80. The prediction block may be within a reconstructed region of the same picture as the current video block as defined by video encoder 20.

[0090] The motion compensation unit 82 and / or the intra BC unit 85 determine prediction information for the video block of the current video frame by parsing the motion vector and other syntax elements, and then use the prediction information to generate a prediction block for the current video block being decoded. For example, the motion compensation unit 82 uses some of the received syntax elements to determine the prediction mode (e.g., intra prediction or inter prediction) used to encode the video block of the video frame, the inter prediction frame type (e.g., B or P), the construction information for one or more of the reference frame lists for the frame, the motion vector for each inter prediction encoded video block of the frame, the inter prediction state for each inter prediction encoded video block of the frame, and other information for decoding the video block in the current video frame.

[0091] Similarly, the intra BC unit 85 may use some of the received syntax elements, such as flags, to determine whether the current video block is predicted using intra BC mode, construction information of which video blocks of the frame are within the reconstruction region and should be stored in the DPB 92, block vectors for each intra BC predicted video block of the frame, intra BC prediction status for each intra BC predicted video block of the frame, and other information for decoding the video block in the current video frame.

[0092] Motion compensation unit 82 may also perform interpolation using interpolation filters as used by video encoder 20 during encoding of the video blocks to calculate interpolated values ​​for sub-integer pixels of reference blocks. In this case, motion compensation unit 82 may determine the interpolation filters used by video encoder 20 based on the received syntax elements and use these interpolation filters to produce the prediction blocks.

[0093] Inverse quantization unit 86 inverse quantizes the quantized transform coefficients provided in the bitstream and entropy decoded by entropy decoding unit 80, using the same quantization parameters calculated by video encoder 20 for each video block in the video frame to determine the degree of quantization. Inverse transform processing unit 88 applies an inverse transform (e.g., an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process) to the transform coefficients to reconstruct the residual block in the pixel domain.

[0094] After the motion compensation unit 82 or the intra BC unit 85 generates a prediction block for the current video block based on the vector and other syntax elements, the adder 90 reconstructs the decoded video block for the current video block by adding the residual block from the inverse transform processing unit 88 to the corresponding prediction block generated by the motion compensation unit 82 and the intra BC unit 85. A loop filter 91 (e.g., a deblocking filter, an SAO filter, and / or an ALF) may be located between the adder 90 and the DPB 92 to further process the decoded video block. In some examples, the loop filter 91 may be omitted, and the decoded video block may be provided directly to the DPB 92 by the adder 90. Then, the decoded video block in a given frame is stored in the DPB 92, which stores a reference frame for subsequent motion compensation of the next video block. The DPB 92 or a memory device separated from the DPB 92 may also store the decoded video for later presentation on a display device (e.g., the display device 34 of FIG. 1).

[0095] In the current VVC and AVS3 standards, the motion information of the current coding block is copied from the spatial or temporal neighboring blocks specified by the merge candidate index, or obtained through explicit signaling of motion estimation. The focus of the present disclosure is to improve the accuracy of the motion vector used for the affine merge mode by improving the derivation method of the affine merge candidate. For the convenience of describing the present disclosure, the existing affine merge mode design in the VVC standard is used as an example to illustrate the proposed ideas. Please note that although the existing affine mode design in the VVC standard is used as an example in the present disclosure, for technicians in the field of modern video coding and decoding technology, the proposed technology can also be applied to different designs of affine motion prediction modes or other coding and decoding tools with the same or similar design spirit.

[0096] In a typical video encoding and decoding process, a video sequence usually includes an ordered set of frames or pictures. Each frame may include three sample arrays, denoted as SL, SCb, and SCr. SL is a two-dimensional array of luma samples. SCb is a two-dimensional array of Cb chroma samples. SCr is a two-dimensional array of Cr chroma samples. In other examples, a frame may be monochrome and therefore include only a two-dimensional array of luma samples.

[0097] like Figure 1C As shown in , the video encoder 20 (or more specifically, a segmentation unit in a prediction processing unit of the video encoder 20) generates an encoded representation of a frame by first segmenting the frame into a set of CTUs. A video frame may include an integer number of CTUs sequentially ordered from left to right and from top to bottom in a raster scan order. Each CTU is the largest logical coding unit, and the width and height of the CTU are signaled by the video encoder 20 in a sequence parameter set so that all CTUs in a video sequence have the same size, one of 128×128, 64×64, 32×32, and 16×16. It should be noted, however, that the present application is not necessarily limited to a particular size. As Figure 1D As shown in , each CTU may include one CTB for luma samples, two corresponding coding tree blocks for chroma samples, and syntax elements for encoding the samples of the coding tree blocks. The syntax elements describe the properties of different types of units of coding pixel blocks and how the video sequence can be reconstructed at the video decoder 30, including inter-frame prediction or intra-frame prediction, intra-frame prediction mode, motion vectors, and other parameters. In a monochrome picture or a picture with three separate color planes, a CTU may include a single coding tree block and syntax elements for encoding the samples of the coding tree block. The coding tree block may be an N×N block of samples.

[0098] To achieve better performance, the video encoder 20 may recursively perform tree partitioning, such as binary tree partitioning, ternary tree partitioning, quadtree partitioning, or a combination thereof, on the coding tree block of the CTU and divide the CTU into smaller CUs. Figure 1E As depicted in , a 64×64 CTU 400 is first divided into four smaller CUs, each CU having a block size of 32×32. Among the four smaller CUs, CU 410 and CU 420 are respectively divided into four CUs with a block size of 16×16. Two 16×16 CUs 430 and CU 440 are further divided into four CUs with a block size of 8×8. Figure 1F Depicted is a diagram showing Figure 1E The quadtree data structure of the final result of the partitioning process of the CTU 400 depicted in FIG. 4 corresponds to a CU of a corresponding size ranging from 32×32 to 8×8. Figure 1DEach CU may include a CB of luma samples and two corresponding coding blocks of chroma samples of the same size frame, and syntax elements for encoding the samples of the coding blocks. In a monochrome picture or a picture with three separate color planes, a CU may include a single coding block and syntax structures for encoding the samples of the coding block. It should be noted that Figure 1E-1F The quadtree partitioning depicted in FIG is for illustrative purposes only, and one CTU can be split into multiple CUs based on quadtree partitioning / ternary tree partitioning / binary tree partitioning to adapt to varying local characteristics. In a multi-type tree structure, one CTU is partitioned according to a quadtree structure, and each quadtree leaf CU can be further partitioned according to a binary and ternary tree structure. Figure 3A-3E As shown, there are five possible partitioning types for a coding block with width W and height H, namely, quadruple partitioning, horizontal binary partitioning, vertical binary partitioning, horizontal ternary partitioning, and vertical ternary partitioning.

[0099] In some embodiments, the video encoder 20 may further partition the coding block of the CU into one or more (M×N) PBs. A PB is a rectangular (square or non-square) sample block to which the same prediction (inter or intra) is applied. The PU of a CU may include a PB of luma samples, two corresponding PBs of chroma samples, and syntax elements for predicting the PBs. In a monochrome picture or a picture with three separate color planes, a PU may include a single PB and a syntax structure for predicting the PB. The video encoder 20 may generate a predicted luma block, a predicted Cb block, and a predicted Cr block for the luma PB, Cb PB, and Cr PB of each PU of the CU.

[0100] The video encoder 20 may use intra prediction or inter prediction to generate a prediction block for a PU. If the video encoder 20 uses intra prediction to generate a prediction block for a PU, the video encoder 20 may generate the prediction block for the PU based on decoded samples of a frame associated with the PU. If the video encoder 20 uses inter prediction to generate a prediction block for a PU, the video encoder 20 may generate the prediction block for the PU based on decoded samples of one or more frames other than the frame associated with the PU.

[0101] After the video encoder 20 generates the predicted luma block, predicted Cb block, and predicted Cr block for one or more PUs of a CU, the video encoder 20 may generate a luma residual block for the CU by subtracting the predicted luma block of the CU from the original luma coding block of the CU, so that each sample in the luma residual block of the CU indicates the difference between a luma sample in one of the predicted luma blocks of the CU and a corresponding sample in the original luma coding block of the CU. Similarly, the video encoder 20 may generate a Cb residual block and a Cr residual block for the CU, respectively, so that each sample in the Cb residual block of the CU indicates the difference between a Cb sample in one of the predicted Cb blocks of the CU and a corresponding sample in the original Cb coding block of the CU, and each sample in the Cr residual block of the CU may indicate the difference between a Cr sample in one of the predicted Cr blocks of the CU and a corresponding sample in the original Cr coding block of the CU.

[0102] In addition, if Figure 1E As shown in , the video encoder 20 can use quadtree partitioning to decompose the luma residual block, Cb residual block and Cr residual block of the CU into one or more luma transform blocks, Cb transform blocks and Cr transform blocks, respectively. A transform block is a rectangular (square or non-square) sample block to which the same transform is applied. A TU of a CU may include a transform block of luma samples, two corresponding transform blocks of chroma samples, and syntax elements for transforming the transform block samples. Therefore, each TU of a CU may be associated with a luma transform block, a Cb transform block and a Cr transform block. In some examples, the luma transform block associated with a TU may be a sub-block of the luma residual block of the CU. The Cb transform block may be a sub-block of the Cb residual block of the CU. The Cr transform block may be a sub-block of the Cr residual block of the CU. In a monochrome picture or a picture with three separate color planes, a TU may include a single transform block and a syntax structure for transforming the samples of the transform block.

[0103] The video encoder 20 may apply one or more transforms to the luma transform block of the TU to generate a luma coefficient block for the TU. The coefficient block may be a two-dimensional array of transform coefficients. The transform coefficient may be a scalar. The video encoder 20 may apply one or more transforms to the Cb transform block of the TU to generate a Cb coefficient block for the TU. The video encoder 20 may apply one or more transforms to the Cr transform block of the TU to generate a Cr coefficient block for the TU.

[0104] After generating a coefficient block (e.g., a luma coefficient block, a Cb coefficient block, or a Cr coefficient block), the video encoder 20 may quantize the coefficient block. Quantization generally refers to a process in which transform coefficients are quantized to potentially reduce the amount of data used to represent the transform coefficients, thereby providing further compression. After the video encoder 20 quantizes the coefficient block, the video encoder 20 may entropy encode syntax elements indicating the quantized transform coefficients. For example, the video encoder 20 may perform CABAC on the syntax elements indicating the quantized transform coefficients. Finally, the video encoder 20 may output a bitstream including a sequence of bits that form a representation of an encoded frame and associated data, and the bitstream is stored in the storage device 32 or sent to the target device 14.

[0105] After receiving the bitstream generated by the video encoder 20, the video decoder 30 can parse the bitstream to obtain syntax elements from the bitstream. The video decoder 30 can reconstruct a frame of video data based at least in part on the syntax elements obtained from the bitstream. The process of reconstructing video data is generally inverse to the encoding process performed by the video encoder 20. For example, the video decoder 30 can perform an inverse transform on the coefficient block associated with the TU of the current CU to reconstruct the residual block associated with the TU of the current CU. The video decoder 30 also reconstructs the coding block of the current CU by adding the samples of the prediction block for the PU of the current CU to the corresponding samples of the transform block of the TU of the current CU. After reconstructing the coding block for each CU of the frame, the video decoder 30 can reconstruct the frame.

[0106] As mentioned above, video coding mainly uses two modes, namely, intra-frame prediction (or intra-frame prediction) and inter-frame prediction (or inter-frame prediction) to achieve video compression. It should be noted that IBC can be regarded as intra-frame prediction or a third mode. Between the two modes, inter-frame prediction contributes more to coding efficiency than intra-frame prediction because motion vectors are used to predict the current video block based on the reference video block.

[0107] But with the ever-improving video data capture technology and finer video block sizes for retaining details in the video data, the amount of data required to represent the motion vector for the current frame has also increased significantly. One way to overcome this challenge benefits from the fact that not only a set of neighboring CUs in both the spatial and temporal domains have similar video data for prediction purposes, but also the motion vectors between these neighboring CUs are similar. Therefore, the motion information of spatially neighboring CUs and / or temporally co-located CUs can be used as an approximation of the motion information (e.g., motion vector) of the current CU (which is also called the "motion vector predictor" (MVP) of the current CU) by exploring their spatial and temporal correlations.

[0108] Instead of combining as above Figure 1BThe actual motion vector of the current CU determined by the motion estimation unit is encoded into the video bitstream, and the motion vector prediction value of the current CU is subtracted from the actual motion vector of the current CU to generate a motion vector difference (MVD) for the current CU. By doing so, it is not necessary to encode the motion vector determined by the motion estimation unit for each CU of the frame into the video bitstream, and the amount of data used to represent the motion information in the video bitstream can be significantly reduced.

[0109] Similar to the process of selecting a prediction block in a reference frame during inter-frame prediction of a coding block, both the video encoder 20 and the video decoder 30 need to adopt a set of rules for constructing a motion vector candidate list (also called a "merge list") for the current CU using those potential candidate motion vectors associated with the spatial neighboring CUs and / or temporal co-located CUs of the current CU, and then selecting a member from the motion vector candidate list as the motion vector prediction value for the current CU. By doing so, the motion vector candidate list itself does not need to be sent from the video encoder 20 to the video decoder 30, and the index of the selected motion vector prediction value within the motion vector candidate list is sufficient for the video encoder 20 and the video decoder 30 to use the same motion vector prediction value within the motion vector candidate list to encode and decode the current CU.

[0110] The present disclosure further enhances the chroma codec efficiency of the motion compensation module applied in ECM. Below, some relevant codec tools in the transform and entropy codec process applied in ECM are briefly reviewed. After that, some defects in the existing design of motion compensation are discussed. Finally, solutions are provided to improve the existing design.

[0111] Motion Compensated Prediction (MCP)

[0112] Motion compensated prediction (MCP), also known as motion compensation, is one of the most widely used video coding techniques in the development of modern video coding standards. In MCP, a video frame is divided into multiple blocks, called prediction units (PUs). Each PU is predicted based on equal-sized blocks from a temporal reference picture, so that the overhead required to transmit blocks with signals is significantly reduced. In all existing video coding standards, each inter-frame PU is associated with a set of motion parameters including one or two MVs and reference picture indexes. Inter-frame PUs in P slices have only one reference picture list, while PUs in B slices can use up to two reference picture lists. In MCP, corresponding inter-frame prediction samples are generated based on their corresponding areas in the reference picture as identified by the MV and the reference picture index. The MV specifies the horizontal and vertical displacement between the current block in the reference picture and its reference block. Figure 4 It shows that d x is the level value of MV and d yis an example of a vertical value of an MV. In practice, the value of an MV can be fractional precision. When an MV has a fractional value, an interpolation filter is applied to generate corresponding prediction samples at the fractional sample positions, such as Figure 5 As shown. In VVC, it supports the MV of luma MC and the MV of chroma MC. The unit of MV of luma MC is 1 / 16 of the distance between two adjacent luma samples, and the unit of MV of chroma MC is 1 / 32 of the distance between two adjacent chroma samples.

[0113] Adaptive loop filtering

[0114] In VVC and ECM, adaptive loop filtering (ALF) is used, where one of 25 filters is selected for each 4x4 block based on the direction and activity of the local gradient.

[0115] Filter shape: Use two diamond filter shapes (such as Figure 6A-6B ). A 7×7 diamond shape is applied to the luma component and a 5×5 diamond shape is applied to the chroma components.

[0116] Block classification: For the luminance component, each 4×4 block is classified into one of 25 categories. The classification index C is based on its directionality D and activity The quantized value of is derived as follows:

[0117]

[0118] In order to calculate D and First, use the 1-D Laplacian to calculate the gradient in the horizontal, vertical, and two diagonal directions:

[0119]

[0120]

[0121] where indexes i and j refer to the coordinates of the top left sample point within the 4×4 block, and R(i,j) indicates the reconstructed sample point at coordinate (i,j). In order to reduce the complexity of block classification, Figure 7 As shown, the subsampled 1-D Laplacian calculation is applied to the gradient calculation in all directions. Then, the maximum and minimum values ​​of the D gradients in the horizontal and vertical directions are set to:

[0122]

[0123] The maximum and minimum values ​​of the gradients in the two diagonal directions are set to:

[0124]

[0125] To derive the value of the directivity D, these values ​​are compared with each other and with two thresholds t1 and t2:

[0126] Step 1: If and If both are true, D is set to 0.

[0127] Step 2: If Then continue from step 3; otherwise continue from step 4.

[0128] Step 3: If D is set to 2; otherwise D is set to 1.

[0129] Step 4: If D is set to 4; otherwise D is set to 3.

[0130] The activity value A is calculated as:

[0131]

[0132] A is further quantized to the range of 0 to 4, inclusive, and the quantized value is represented as For the chrominance components of the picture, no classification method is applied.

[0133] Geometric transformation of filter coefficients and clipping values

[0134] Before filtering each 4×4 luma block, geometric transformations such as rotation or diagonal and vertical flipping are applied to the filter coefficients f(k,l) and the corresponding filter clipping values ​​c(k,l), depending on the gradient values ​​calculated for the block. This is equivalent to applying these transformations to the samples in the filter support region. The idea is to make different blocks with ALF applied more similar by aligning their directionality.

[0135] Provides three geometric transformations, including diagonal, vertical flip, and rotation:

[0136]

[0137] Where K is the size of the filter and 0≤k,l≤K-1 are the coefficient coordinates, so that the position (0,0) is at the upper left corner and the position (K-1,K-1) is at the lower right corner. Depending on the gradient value calculated for the block, a transform is applied to the filter coefficients f(k,l) and the clipping value c(k,l). The relationship between the transform and the four gradients in the four directions is summarized in Table 1 below.

[0138] Table 1

[0139]

[0140]

[0141] Table 1

[0142] Filtering process

[0143] When ALF is enabled for a CTB, each sample R(i,j) within the CU is filtered to produce a sample value R′(i,j) as shown below,

[0144]

[0145] where f(k, l) represents the decoded filter coefficients, K(x, y) is the clipping function and c(k, l) represents the decoded clipping parameters. The variables k and l are in and Where L represents the filter length. Clip3(-y,y,x) is a clipping function that clips the input value of x to the range [-y,y]. The clipping operation introduces nonlinearity to make the ALF more efficient by reducing the influence of adjacent sample values ​​that are too different from the current sample value.

[0146] Cross-component adaptive loop filter

[0147] A cross-component adaptive loop filter (CC-ALF) uses luma samples to refine each of the two chroma components by applying an adaptive linear filter to the luma channel and then using the output of this filtering operation for chroma refinement. Figure 8 As shown, the filtering operation in CC-ALF is implemented by applying a diamond filter to the luma channel. One filter is used for each chroma channel, and the operation is expressed as

[0148]

[0149] where (x,y) is the chromaticity position being refined, and (x Y ,y Y ) is based on the same brightness position at (x,y), S i is the filter support area in the luminance component, c i (x0,y0) represents the filter coefficients.

[0150] Up to 8 CC-ALF filters can be designed and sent per picture. The resulting filters are then indicated on a CTU basis for each of the two chroma channels. In addition, the following features are also included in the existing CC-ALF design:

[0151] • The design uses a 3x4 diamond shape with 8 taps.

[0152] Seven filter coefficients are sent in the APS.

[0153] • Each of the transmitted coefficients has a 6-bit dynamic range and is limited to values ​​that are powers of 2.

[0154] • Deriving the eighth filter coefficients at the decoder such that the sum of the filter coefficients is equal to zero.

[0155] ●APS can be referenced in the slice header.

[0156] • CC-ALF filter selection is controlled at CTU-level for each chroma component.

[0157] MCP plays a key role in ensuring the efficiency of inter-frame coding in all existing video codec standards. With MCP, the video signal to be encoded is predicted based on temporally adjacent signals, and only the prediction error, MV and reference picture index are sent. At the same time, both ALF and CC-ALF can effectively improve the quality of the reconstructed video, thereby improving the performance of inter-frame coding by providing high-quality reference pictures. However, the quality of the temporal reference pictures may not be sufficient to provide effective inter-frame prediction, especially for chroma components, due to the following reasons:

[0158] The video signal may be encoded and decoded using coarse quantization, i.e., high quantization parameter (QP) values. When coarse quantization is applied, the reconstructed picture may contain severe encoding and decoding artifacts, such as blocking artifacts, ringing artifacts, etc. This may cause some high-frequency information present in the original picture to be missing and / or distorted in the reconstructed picture, for example, in the form of distorted edges and blurred textures. Assuming that the reconstructed signal of the current picture will be used as a reference for temporal prediction, this missing and / or distorted high-frequency information may reduce the effectiveness of MCP and thus reduce the inter-frame encoding and decoding efficiency of subsequent pictures.

[0159] Since the human visual system is more sensitive to changes in brightness than to changes in color, video codec systems typically invest more bits in the luma component than in the chroma component, for example by adjusting the QP delta value between the luma component and the chroma component. In addition, the chroma component typically has a smaller dynamic range and is therefore smoother than the luma component. Therefore, more transform coefficients of the chroma component become zero after quantization. Therefore, the problem of lost or distorted high-frequency information may be more obvious in the reconstructed chroma signal. This may seriously affect the prediction efficiency of the chroma component because more bits need to be generated to encode and decode the chroma residual signal. Although CC-ALF may be able to recover the lost high-frequency information in the reconstructed picture, the lost high-frequency information may be attenuated in the motion compensation stage when they are used as reference pictures for inter-frame prediction.

[0160] In the present disclosure, a method is proposed to improve the efficiency of motion compensated prediction of chroma components and thus enhance the quality of temporal prediction. Specifically, it is proposed to apply adaptive cross-component filtering at the motion compensation stage, which is called cross-component motion compensated prediction (CC-MCP), which uses the high-frequency information of motion compensated luma samples as a guide to improve the quality of motion compensated chroma samples. In this way, the energy of the chroma residual is minimized, thereby reducing the overhead of signaling chroma signals.

[0161] Fig. 9 A block diagram of a video encoder when the proposed CC-MCP is applied is provided. First, similar to a conventional video encoder, a motion estimation and compensation module generates a motion-compensated luminance signal and a chrominance signal by matching a current block with a block in a reference picture using an optimal MV. An adaptive cross-component filter, i.e., CC-MCP filtering, is then provided, in which the motion-compensated chrominance signal is filtered using the proposed CC-MCP filter according to the corresponding motion-compensated luminance signal to generate a filtered motion-compensated chrominance signal. Thereafter, the original signal is subtracted from the prediction signal to remove temporal redundancy and generate a corresponding residual signal. Transformation and quantization are applied to the residual signal, which is then entropy encoded and output to a bitstream. In order to obtain a reconstructed signal, the reconstructed residual signal is made available by inverse quantization and inverse transformation. Then, the reconstructed residual is added to the motion-compensated prediction. In addition, a loop filtering process (e.g., deblocking, ALF, and SAO) is applied to the reconstructed video signal for output. As will be discussed later, the filter coefficients of the proposed CC-MCP filter can be derived directly from the adjacent reconstructed luma samples and reconstructed chroma samples at the decoder or derived at the encoder and sent to the decoder. In addition, in order to maximize the encoding and decoding gain of the proposed method, additional syntax can be signaled at a given block level (e.g., CTU, CU or PU level) to indicate whether the proposed CC-MCP filtering is applied to the current block for motion compensation.

[0162] Fig.10 shows a block diagram of the proposed decoder, which receives Fig. 9The bitstream produced by the encoder in . At the decoder, the bitstream is first parsed by an entropy decoder. The residual coefficients are then inverse quantized and inverse transformed to obtain the reconstructed residual. For temporal prediction, a prediction signal is first generated by obtaining a motion compensated block using the prediction information transmitted by the signal (i.e., MV and reference index). Then, if CC-MCP is enabled for the block as parsed from the bitstream, the motion compensated chrominance signal is further processed by the proposed CC-MCP filtering; otherwise, the motion compensated chrominance signal is not filtered. The motion compensated signal (filtered or unfiltered) and the reconstructed residual are then added together to obtain a reconstructed video. The reconstructed video can be additionally loop filtered and then stored in a reference picture store for display and / or for decoding future video signals.

[0163] CC-MCP filtering process of motion compensated chrominance signal

[0164] Since the human visual system is more sensitive to changes in brightness than to changes in color, the video codec system usually invests more bits in the luma component than in the chroma component, for example by adjusting the QP delta value between the luma component and the chroma component. Therefore, the chroma component is usually smoother than the luma component. As a result, more transform coefficients are quantized to zero, and there will be more blurred edges and textures in the reconstructed chroma signal. This may reduce the prediction efficiency of chroma, so more overhead is required to encode and decode the chroma residual. Although ALF can be applied to reduce the distortion between the reference chroma signal and the original chroma signal, due to the low-pass characteristics of the ALF filter, the ALF cannot recover the high-frequency information lost in the reconstructed chroma signal.

[0165] In the present disclosure, blurred edges and textures in the chroma channel of a temporal prediction signal can be restored or repaired by using corresponding neighboring samples in the luma channel. Specifically, cross-component filtering is applied during the motion compensation stage, which uses the high-frequency information of the motion compensated luma signal as a guide to improve the quality of the motion compensated chroma signal. Specifically, assume that C(x, y) and C′(x, y) indicate the original reconstructed chroma sample and the filtered reconstructed chroma sample at coordinates (x, y); f L (x, y) indicates the coefficients of the high-pass filter applied to the corresponding H×L neighboring region of the reconstructed luma sample Y(2x-i, 2y-j), where The proposed CC-MCP filtering can be calculated based on the following equation.

[0166]

[0167] In another embodiment, in addition to the linear filter coefficients (i.e., f in (9) cIn addition to (i, j)), it is proposed to introduce additional offset terms and nonlinear terms into the proposed CC-MCP filter design. Specifically, based on the same notation in (9), the chrominance prediction samples generated according to the CC-MCP process can be formulated as

[0168]

[0169] Among them c is the offset, and nl c is a nonlinear term, which is expressed as the sum of a series of powers (ie, k=2, ..., K-1) of co-located luminance samples Y(2x, 2y).

[0170] Decoder-side derivation of CC-MCP filter coefficients

[0171] In the following, a decoder-side method is proposed, where the coefficients of the proposed CC-MCP filter are derived at the decoder without signaling. Specifically, when CC-MCP filtering is applied to a block, the method derives the coefficients based on the neighboring reconstructed chroma samples of the current block and their corresponding luma and chroma prediction samples. Given a block B and its predefined neighboring region P (e.g., We can use the coded MV of the current block to find the corresponding luminance prediction sample point and chrominance prediction samples Then, the LMMSE method can be used by taking and The filter coefficients are derived as the input of the CC-MCP filter and used The difference between the output from CC-MCP filtering and the output from CC-MCP filtering is minimized, that is,

[0172]

[0173] Afterwards, the derived filter can be applied to enhance the chrominance prediction signal of the current block, as shown in equation (9).

[0174] When considering the offset term and nonlinear term in (10), the LMMSE-based CC-MCP filter coefficient derivation can be formulated as

[0175]

[0176] On the other hand, since the proposed method uses the motion compensation samples of the neighboring area at the target for LMMSE derivation, it may be more beneficial to apply the proposed decoder-side derivation method when the reconstructed signal of the current picture contains higher quality reconstruction information than the reference picture. Therefore, in one embodiment of the present disclosure, the proposed decoder-side derivation method is applied only when the reference picture uses a smaller QP value than the current picture.

[0177] Explicit signaling of CC-MCP filter coefficients

[0178] In the above method, CC-MCP filter coefficients are derived from neighboring reconstructed samples, which may be inaccurate considering that neighboring reconstructed samples may always be highly correlated with samples in the current block. To address this problem, in one embodiment, it is proposed to derive CC-MCP filter coefficients at the encoder and explicitly signal the CC-MCP filter coefficients to the decoder.

[0179] When such a signaling-based scheme is used in an actual video codec system, the adaptation of CC-MCP filter coefficients can be applied at various codec levels (e.g., sequence level, picture / slice level, and / or block level); and each adaptation level can provide a different tradeoff between codec efficiency and encoding / decoding complexity. For example, if the filter coefficients are adapted at the sequence level, the encoder needs to derive the filter coefficients for the entire video sequence, and all filter coefficients and the decision on whether to apply motion compensation filtering can be carried in a sequence level parameter set (e.g., a video parameter set (VPS) and a sequence parameter set (SPS)). If the filter coefficients are adapted at the picture level, the encoder needs to derive the filter coefficients for one picture, and all filter coefficients and the decision on whether to apply motion compensation filtering can be carried in a picture level parameter set (e.g., a picture parameter set (PPS)). If the filter coefficients are adapted at the slice level, the encoder needs to derive the filter coefficients for each individual slice, and all filter coefficients and the decision on whether to apply motion compensation filtering can be carried in a slice header. In addition, since the motivation of the present disclosure is to recover high frequency information in the motion compensated chrominance signal, the proposed filtering method may only benefit areas with rich edge and texture information. With this in mind, a region-based filter coefficient adaptation method may also be applied, where the motion compensation filter is signaled for different regions and applied only to regions containing rich high frequency details. In this way, a high pass filter will not be applied to prediction samples in flat regions, which may reduce encoding / decoding complexity. The encoder / decoder may determine whether a region is flat based on the motion compensated luma samples.

[0180] Using CC-MCP to handle unidirectional and bidirectional predictions

[0181] In modern video coding standards, there are two main prediction types used for motion compensated prediction, called unidirectional prediction and bidirectional prediction. For unidirectional prediction, unidirectional prediction is applied, where each block can be predicted using at most one motion compensated block from one reference picture; for bidirectional prediction, bidirectional prediction is applied, where one block can be predicted by averaging two motion compensated blocks from two reference pictures. All the above CC-MCP schemes are discussed based on the assumption that the prediction signal of the current video block to be coded is from one prediction direction (i.e., unidirectional prediction). For bidirectional predicted blocks, the proposed motion compensated filtering scheme can be applied in different ways.

[0182] In the first method, it is proposed to apply the CC-MCP filter only once to directly enhance the output chrominance prediction samples. Specifically, in this method, the encoder / decoder first generates a motion compensated prediction of the encoded video by averaging two prediction signals from two reference pictures; then the proposed CC-MCP is applied to enhance the quality of the resulting chrominance prediction signal.

[0183] In the second method, two CC-MCP filtering processes are applied to enhance the motion compensation prediction signals from two reference pictures respectively. Specifically, for a bidirectional prediction block, the method first generates two prediction blocks from two reference picture lists; then CC-MCP is applied to enhance the quality of the two prediction blocks respectively, and the two prediction blocks are finally averaged to generate an output prediction signal.

[0184] Adaptive filtering of motion compensated signals for luminance components

[0185] Using the MCP of the luminance component, the video signal in the current picture is predicted based on the reconstructed signal of the temporally adjacent reference pictures, which may contain unexpected noise and quantization errors. As a result, some high-frequency information present in the original luminance signal may be lost or distorted in the reconstructed image. Therefore, in order to compensate for this distortion, it is proposed to apply a high-pass filtering process to the luminance component of the motion compensated signal to improve the quality of the motion compensated luminance signal. It is assumed that the proposed filter for the motion compensated luminance signal is composed of a 2D finite impulse response (FIR) filter comprising N×N taps, and the filter coefficients are calculated by f L (x,y) represents, where The proposed high-pass filtering process for motion compensated luminance signal can be calculated by 2D convolution based on the following equation.

[0186]

[0187] where Y(x,y) and Y′(x,y) are the motion compensated luminance signals before and after the filtering process; and * denotes a convolution operation.

[0188] Similar to (10), additional offset terms and nonlinear terms can be introduced into the proposed adaptive luminance MCP filtering process as follows:

[0189]

[0190] Among them L is the offset, and nl L is a nonlinear term, which is expressed as the sum of a series of powers (ie, k=2, ..., K-1) of the luma samples Y(x, y).

[0191] There may be different schemes for deriving the coefficients of the proposed luma MCP filter. In one approach, it is proposed to derive the coefficients of the proposed luma MCP filter at the decoder based on the neighboring reconstructed luma samples of the current CU. Specifically, when this scheme is applied, the decoder calculates the coefficients of the luma MCP filter based on the neighboring reconstructed luma samples of the current block. Given a block B and its predefined neighboring region P (e.g., The decoder can use the coded MV of the current block to find the corresponding luminance prediction sample point Then, the LMMSE method can be used to minimize and The filter coefficients are derived from the difference between

[0192]

[0193] In addition, when considering the offset term and nonlinear term in (14), the decoder-side filter coefficient derivation of the proposed luminance MCP filter can be formulated as

[0194]

[0195] In another scheme, it is proposed to derive the luma MCP filter directly at the encoder and signal the corresponding filter coefficients to the decoder. Given that the additional complexity of deriving the MCP filter coefficients can now be abandoned at the decoder, this scheme can reduce the decoding complexity of the proposed luma MCP filtering. In addition, when applying this signaling-based scheme, adaptation of the luma MCP filter can be performed at different codec levels. For example, VPS, SPS, PPS, picture header / slice header or even coding block level.

[0196] Fig.11A computing environment (or computing device) 1110 coupled to a user interface 1160 is shown. The computing environment 1110 may be part of a data processing server. In some embodiments, the computing device 1110 may perform any of the various methods or processes (e.g., encoding / decoding methods or processes) described above according to various examples of the present disclosure. The computing environment 1110 may include a processor 1120, a memory 1140, and an I / O interface 1150.

[0197] The processor 1120 generally controls the overall operation of the computing environment 1110, such as operations associated with display, data acquisition, data communication, and image processing. The processor 1120 may include one or more processors to execute instructions to perform all or some steps in the above method. In addition, the processor 1120 may include one or more modules that facilitate interaction between the processor 1120 and other components. The processor may be a central processing unit (CPU), a microprocessor, a single-chip machine, a GPU, etc.

[0198] The memory 1140 is configured to store various types of data to support the operation of the computing environment 1110. The memory 1140 may include predetermined software 1142. Examples of such data include instructions for any application or method operating on the computing environment 1110, video data sets, image data, etc. The memory 1140 may be implemented by using any type of volatile or non-volatile memory device or a combination thereof, such as a static random access memory (SRAM), an electrically erasable programmable read-only memory (EEPROM), an erasable programmable read-only memory (EPROM), a programmable read-only memory (PROM), a read-only memory (ROM), a magnetic memory, a flash memory, a magnetic disk, or an optical disk.

[0199] The I / O interface 1150 provides an interface between the processor 1120 and peripheral interface modules such as a keyboard, a click wheel, buttons, etc. The buttons may include, but are not limited to, a home button, a start scan button, and a stop scan button. The I / O interface 1150 may be coupled to an encoder and a decoder.

[0200] In some embodiments, a non-transitory computer-readable storage medium is also provided, which includes multiple programs, such as included in the memory 1140, which can be executed by the processor 1120 in the computing environment 1110 to perform the above method. For example, the non-transitory computer-readable storage medium can be a ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, etc.

[0201] A non-transitory computer-readable storage medium stores a plurality of programs for execution by a computing device having one or more processors, wherein the plurality of programs, when executed by the one or more processors, causes the computing device to perform the above-mentioned method for motion prediction.

[0202] In some embodiments, the computing environment 1110 may be implemented using one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), graphics processing units (GPUs), controllers, microcontrollers, microprocessors, or other electronic components to perform the above methods.

[0203] Fig.12 is a flow chart illustrating a method for video decoding according to an example of the present disclosure. The method can be implemented for decoding an inter-coded block.

[0204] In step 1201, the processor 1120 may obtain a plurality of first motion compensation samples of a first channel and a plurality of second motion compensation samples of a second channel for a current inter-frame coding block at the decoder side. In some examples, the plurality of first motion compensation samples and the plurality of second motion compensation samples may be obtained by the same prediction method based on the current inter-frame coding block. In some other examples, the plurality of first motion compensation samples and the plurality of second motion compensation samples may be obtained by two different prediction methods based on the current inter-frame coding block. For example, different interpolation filters (e.g., having different filter lengths and / or filter coefficients) may be applied to generate the first motion compensation samples and the second motion compensation samples.

[0205] In step 1202, the processor 1120 may obtain a nonlinear filter. The nonlinear filter is used to filter a plurality of first motion compensated samples of a first channel. In some examples, the filter may be obtained by deriving coefficients of the nonlinear filter.

[0206] In some examples, the coefficients of the nonlinear filter may include any one or any combination of linear coefficients, offset or nonlinear coefficients. For example, in equation (10), the linear coefficient may be f c (i,j), the offset can be o c , the nonlinear coefficient can be nl c .

[0207] In some examples, the processor 1120 may derive coefficients of the nonlinear filter based on the motion information of the current inter-frame coding block, the first adjacent reconstructed samples of the first channel, and the second adjacent reconstructed samples of the second channel. Figure 8As shown, the first / second adjacent reconstruction sample points may be located in a predefined adjacent area.

[0208] In step 1203, the processor 1120 may obtain a plurality of filtered motion compensated samples of the first channel based on the nonlinear filter, the first motion compensated samples of the first channel, and the second motion compensated samples of the second channel.

[0209] In some examples, processor 1120 may obtain multiple refinements of the first channel by applying a nonlinear filter to the second motion compensated samples of the second channel; and obtain multiple filtered motion compensated samples of the first channel based on the refinements of the first channel and the first motion compensated samples.

[0210] In some examples, the first channel may be a chroma channel and the second channel may be a luma channel.

[0211] In some other examples, the first channel and the second channel may be the same channel. For example, the same channel may be a luminance channel or a chrominance channel. In this case, the plurality of first motion compensation samples and the plurality of second motion compensation samples are the same.

[0212] In some examples, processor 1120 may receive one or more filter coefficients of a nonlinear filter signaled by an encoder, wherein the one or more filter coefficients are signaled at a specific level. For example, the specific level may include one of the following levels: sequence level, picture level, or block level.

[0213] Fig.13 is a flow chart illustrating steps for deriving coefficients of a non-linear filter in a method for video decoding according to an example of the present disclosure. The method may be implemented for decoding an inter-coded block.

[0214] In step 1301, the processor 1120 may obtain a plurality of first prediction samples of a first adjacent reconstruction sample of a first channel and a plurality of second prediction samples of a second adjacent reconstruction sample of a second channel based on motion information of a current inter-frame coding block, wherein the plurality of first adjacent reconstruction samples or the plurality of second adjacent reconstruction samples are located in a predefined adjacent region. For example, as shown in equation (12), the LMMSE method may be used by and The filter coefficients are derived as input to the CC-MCP filter.

[0215] In step 1302, the processor 1120 may obtain a plurality of output adjacent samples of the first channel based on a nonlinear filter and first predicted samples of first adjacent reconstructed samples of the first channel and second predicted motion compensated samples of second adjacent reconstructed samples of the second channel.

[0216] In step 1303, the processor 1120 may derive one or more coefficients for the nonlinear filter by minimizing the difference between the plurality of output adjacent samples of the first channel and the first adjacent reconstructed sample of the first channel. For example, as shown in equation (12), the LMMSE method may be used to minimize the difference between the plurality of output adjacent samples of the first channel and the first adjacent reconstructed sample of the first channel. and As the input of CC-MCP filter, The filter coefficients are derived by minimizing the difference between the output obtained from CC-MCP filtering.

[0217] In some examples, the processor 1120 may obtain a plurality of refinements of the first adjacent reconstructed samples of the first channel by applying a nonlinear filter to the second predicted samples of the second adjacent samples of the second channel; and obtain a plurality of output adjacent samples of the first channel based on the refinements of the first adjacent reconstructed samples of the first channel and the first predicted samples. For example, as shown in equation (12), the coefficients of the linear nonlinear filter (e.g., f c (i,j),o c and nl c ) for filtering To obtain

[0218] Fig.14 is a flow chart illustrating a method for video encoding according to an example of the present disclosure. The method can be implemented for encoding an inter-coded block.

[0219] In step 1401, on the encoder side, the processor 1120 may obtain a plurality of first motion compensation samples of a first channel and a plurality of second motion compensation samples of a second channel for a current inter-frame coding block.

[0220] In step 1402, the processor 1120 may obtain a nonlinear filter. The nonlinear filter is used to filter a plurality of first motion compensated samples of a first channel. In some examples, the filter may be obtained by deriving coefficients of the nonlinear filter.

[0221] In some examples, the coefficients of the nonlinear filter may include any one or any combination of linear coefficients, offset or nonlinear coefficients. For example, in equation (10), the linear coefficient may be f c (i,j), the offset can be o c , and the nonlinear coefficient can be nl c .

[0222] In some examples, the processor 1120 may derive coefficients of a nonlinear filter based on motion information of the current inter-frame coding block, first adjacent reconstructed samples of the first channel, and second adjacent reconstructed samples of the second channel. Figure 8 As shown, the first / second adjacent reconstruction sample points may be located in a predefined adjacent area.

[0223] In step 1403, the processor 1120 may obtain a plurality of filtered motion compensated samples of the first channel based on the nonlinear filter, the first motion compensated samples of the first channel, and the second motion compensated samples of the second channel.

[0224] In some examples, processor 1120 may obtain multiple refinements of the first channel by applying a nonlinear filter to second motion compensated samples of the second channel; and obtain multiple filtered motion compensated samples of the first channel based on the refinements of the first channel and the first motion compensated samples.

[0225] In some examples, the first channel may be a chroma channel and the second channel may be a luma channel.

[0226] In some other examples, the first channel and the second channel may be the same channel. For example, the same channel may be a luminance channel or a chrominance channel.

[0227] In some examples, processor 1120 may send one or more filter coefficients of a non-linear filter signaled by an encoder to a decoder, wherein the one or more filter coefficients are signaled at a specific level. For example, the specific level may include one of the following levels: sequence level, picture level, or block level.

[0228] Fig.15 The flowchart is a flowchart showing steps for deriving coefficients of a non-linear filter in a method for video encoding according to an example of the present disclosure. The method can be implemented for encoding an inter-coded block.

[0229] In step 1501, the processor 1120 may obtain a plurality of first prediction samples of a first adjacent reconstruction sample of a first channel and a plurality of second prediction samples of a second adjacent reconstruction sample of a second channel based on motion information of a current inter-frame coding block, wherein the plurality of first adjacent reconstruction samples or the plurality of second adjacent reconstruction samples are located in a predefined adjacent area. For example, as shown in equation (12), the LMMSE method may be used by dividing and The filter coefficients are derived as input to the CC-MCP filter.

[0230] In step 1502, the processor 1120 may obtain a plurality of output adjacent samples of the first channel based on a nonlinear filter and first predicted samples of first adjacent reconstructed samples of the first channel and second predicted motion compensated samples of second adjacent reconstructed samples of the second channel.

[0231] In step 1503, the processor 1120 may derive one or more coefficients of the nonlinear filter by minimizing the difference between the plurality of output adjacent samples of the first channel and the first adjacent reconstructed sample of the first channel. For example, as shown in equation (12), the LMMSE method may be used to minimize the difference between the plurality of output adjacent samples of the first channel and the first adjacent reconstructed sample of the first channel. and As the input of CC-MCP filter, The filter coefficients are derived by minimizing the difference between the output obtained from CC-MCP filtering.

[0232] In some examples, the processor 1120 may obtain a plurality of refinements of the first adjacent reconstructed samples of the first channel by applying a nonlinear filter to the second predicted samples of the second adjacent samples of the second channel; and obtain a plurality of output adjacent samples of the first channel based on the refinements of the first adjacent reconstructed samples of the first channel and the first predicted samples. For example, as shown in equation (12), the coefficients of the linear nonlinear filter (e.g., f c (i,j),o c and nl c ) for filtering To obtain

[0233] In some examples, a device for video encoding and decoding is provided. The device includes a processor 1120 and a memory 1140 configured to store instructions executable by the processor; wherein the processor is configured to perform the following when executing the instructions: Figure 12-Figure 15 Any method shown.

[0234] In some other examples, a non-transitory computer-readable storage medium is provided, in which instructions are stored. When the instructions are executed by the processor 1120, the instructions cause the processor to perform the following steps: Figure 12-Figure 15 In one example, multiple programs can be executed by processor 1120 in computing environment 1110 to receive (e.g., from Figure 1GThe video encoder 20 in the computing environment 1110 includes a bit stream or data stream of encoded video information (e.g., video blocks representing encoded video frames and / or one or more associated syntax elements, etc.), and can also be executed by the processor 1120 in the computing environment 1110 to perform the decoding method described above according to the received bit stream or data stream. In another example, multiple programs can be executed by the processor 1120 in the computing environment 1110 to perform the above encoding method to encode video information (e.g., video blocks representing video frames and / or one or more associated syntax elements, etc.) into a bit stream or data stream, and can also be executed by the processor 1120 in the computing environment 1110 to send the bit stream or data stream (e.g., to the processor 1120). Figure 2B Alternatively, a non-transitory computer-readable storage medium may store therein a video decoder 30 in the video decoder 30. Figure 1G The video encoder 20 in the embodiment of the present invention uses a bit stream or data stream of encoded video information (e.g., video blocks representing encoded video frames and / or associated one or more syntax elements, etc.) generated by the encoding method described above for use by a decoder (e.g., Figure 2B The video decoder 30 in the video decoder 30 is used when decoding video data. The non-transitory computer-readable storage medium may be, for example, a ROM, a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, etc.

[0235] By considering the specification and practice of the present disclosure disclosed herein, other examples of the present disclosure will be apparent to those skilled in the art. This application is intended to cover any changes, uses or adaptations of the present disclosure following the general principles of the present disclosure, including deviations from the present disclosure in known or customary practices in the art. This specification and examples are intended to be considered as exemplary only.

[0236] It will be understood that the present disclosure is not limited to the exact examples described above and shown in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof.

Claims

1. A method for video decoding of an inter-frame coded block, comprising: The decoder obtains a plurality of first motion compensation samples of a first channel and a plurality of second motion compensation samples of a second channel for the current inter-frame coding block; obtaining a nonlinear filter by the decoder; as well as A plurality of filtered motion compensated samples of the first channel are obtained by the decoder based on the non-linear filter, the first motion compensated samples of the first channel, and the second motion compensated samples of the second channel.

2. The method according to claim 1, wherein: Obtaining the plurality of filtered motion compensated samples of the first channel comprises: obtaining, by the decoder, a plurality of refinements of the first channel by applying the non-linear filter to the second motion compensated samples of the second channel; and The plurality of filtered motion compensated samples of the first pass are obtained by the decoder based on the refinement of the first pass and the first motion compensated samples.

3. The method according to claim 1, wherein: The coefficients of the nonlinear filter include any one or any combination of linear coefficients, offset or nonlinear coefficients.

4. The method according to claim 1, wherein: Obtaining the nonlinear filter comprises: The coefficients of the nonlinear filter are derived based on the motion information of the current inter-frame coding block, first adjacent reconstructed samples of the first channel, and second adjacent reconstructed samples of the second channel.

5. The method according to claim 4, wherein: Deriving coefficients of the nonlinear filter includes: The decoder obtains, based on the motion information of the current inter-frame coding block, a plurality of first prediction samples of the first adjacent reconstructed samples of the first channel and a plurality of second prediction samples of the second adjacent reconstructed samples of the second channel, wherein the plurality of the first adjacent reconstructed samples or the plurality of the second adjacent reconstructed samples are located in a predefined adjacent area; Obtaining, by the decoder, a plurality of output adjacent samples of the first channel based on the nonlinear filter and the first predicted samples of the first adjacent reconstructed samples of the first channel and the second predicted samples of the second adjacent reconstructed samples of the second channel; and One or more coefficients for the non-linear filter are derived by the decoder by minimizing differences between the plurality of output neighboring samples of the first channel and the first neighboring reconstructed samples of the first channel.

6. The method according to claim 5, wherein: Obtaining the plurality of output adjacent sample points of the first channel comprises: obtaining, by the decoder, a plurality of refinements of the first neighboring reconstructed samples of the first channel by applying the non-linear filter to the second predicted samples of the second neighboring samples of the second channel; and The plurality of output neighboring samples of the first channel are obtained by the decoder based on the refinement of the first neighboring reconstructed samples of the first channel and the first prediction samples.

7. The method according to claim 1, wherein: The first channel is a chrominance channel, and the second channel is a luma channel.

8. The method according to claim 1, wherein: The first channel and the second channel are the same channel.

9. The method according to claim 8, wherein: The same channel is the luminance channel.

10. The method according to claim 8, wherein: The same channel is the chrominance channel.

11. The method according to claim 1, further comprising: One or more filter coefficients of the non-linear filter signaled by an encoder are received by the decoder, wherein the one or more filter coefficients are signaled at a specific level.

12. The method according to claim 11, wherein: The specific level includes one of the following levels: sequence level, picture level or block level.

13. A method for video encoding, comprising: The encoder obtains, for the current inter-frame coding block, a plurality of first motion compensation samples of the first channel and a plurality of second motion compensation samples of the second channel; obtaining a nonlinear filter from the encoder; as well as A plurality of filtered motion compensated samples of the first channel are obtained by the encoder based on the non-linear filter, the first motion compensated samples of the first channel, and the second motion compensated samples of the second channel.

14. The method according to claim 13, wherein: Obtaining the plurality of filtered motion compensated samples of the first channel comprises: obtaining, by the encoder, a plurality of refinements of the first channel by applying the non-linear filter to the second motion compensated samples of the second channel; and The plurality of filtered motion compensated samples of the first pass are obtained by the encoder based on the refinement of the first pass and the first motion compensated samples.

15. The method according to claim 13, wherein: The coefficients of the nonlinear filter include any one or any combination of linear coefficients, offset or nonlinear coefficients.

16. The method according to claim 13, wherein: Obtaining the nonlinear filter comprises: The coefficients of the nonlinear filter are derived based on the motion information of the current inter-frame coding block, first adjacent reconstructed samples of the first channel, and second adjacent reconstructed samples of the second channel.

17. The method according to claim 16, wherein: Deriving coefficients of the nonlinear filter includes: The encoder obtains, based on the motion information of the current inter-frame coding block, a plurality of first prediction samples of the first adjacent reconstructed samples of the first channel and a plurality of second prediction samples of the second adjacent reconstructed samples of the second channel, wherein the plurality of the first adjacent reconstructed samples or the plurality of the second adjacent reconstructed samples are located in a predefined adjacent area; Obtaining, by the encoder, a plurality of output neighboring samples of the first channel based on the nonlinear filter and the first predicted samples of the first neighboring reconstructed samples of the first channel and the second predicted motion compensated samples of the second neighboring reconstructed samples of the second channel; and One or more coefficients for the non-linear filter are derived by the encoder by minimizing differences between the plurality of output neighboring samples of the first channel and the first neighboring reconstructed samples of the first channel.

18. The method according to claim 17, wherein: Obtaining the plurality of output adjacent sample points of the first channel comprises: obtaining, by the encoder, a plurality of refinements of the first neighboring reconstructed samples of the first channel by applying the non-linear filter to the second predicted samples of the second neighboring samples of the second channel; and The plurality of output neighboring samples of the first channel are obtained by the encoder based on the refinement of the first neighboring reconstructed samples of the first channel and the first prediction samples.

19. The method according to claim 13, wherein: The first channel is a chrominance channel, and the second channel is a luma channel.

20. The method according to claim 13, wherein: The first channel and the second channel are the same channel.

21. The method according to claim 20, wherein: The same channel is the luminance channel.

22. The method according to claim 20, wherein: The same channel is the chrominance channel.

23. The method of claim 13, further comprising: One or more filter coefficients of the non-linear filter are sent by the encoder to a decoder, wherein the one or more filter coefficients are signaled at a specific level.

24. The method according to claim 23, wherein: The specific level includes one of the following levels: sequence level, picture level or block level.

25. An apparatus comprising: one or more processors; as well as a memory coupled to the one or more processors and configured to store instructions executable by the one or more processors, Wherein, when executing the instructions, the one or more processors are configured to perform the method according to any one of claims 1-24.

26. A non-transitory computer-readable storage medium for storing computer-executable instructions, which, when executed by one or more computer processors, cause the one or more computer processors to perform the method of any one of claims 1-24.

27. A non-transitory computer-readable storage medium for storing a bit stream to be decoded by the method of any one of claims 1-12.

28. A non-transitory computer-readable storage medium for storing a bitstream generated by the method of any one of claims 13-24.

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