Video coding and decoding method and device and storage medium

Abstract

Aspects of the disclosure include methods, apparatuses, and storage media for video encoding and decoding. A video decoding apparatus includes a processing circuit. A processing circuit decodes prediction information of a current block in a current picture. The current picture is part of an encoded video sequence. The prediction information indicates a plurality of combinations of processed reconstructed samples. The processing circuitry performs a filtering process on the processed reconstructed sample combination of the first color component of the current block. Wherein the processing circuitry determines an output value of the filtering process based on one of a default value, a predicted output value, and an output value indicated in the prediction information. Wherein the combination of processed reconstructed samples of the first color is not included in the plurality of combinations. The processing circuitry reconstructs the current block based on an output value of the filtering process being applied to a reconstructed sample of a second color component of the current block. The second color component is different from the first color component.

Description

Incorporation by Reference

[0001] This application claims priority to U.S. Patent Application No. 17 / 360,840, filed on June 28, 2021, "METHOD AND APPARATUS FOR VIDEO CODING," which claims priority to U.S. Provisional Application No. 63 / 113,120, filed on November 12, 2020, "IMPROVED CROSS-COMPONENT SAMPLE OFFSET." The entire disclosures of these prior applications are hereby incorporated by reference in their entirety. Technical Field

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

[0003] The background description provided herein is intended to present the background of the present application as a whole. The extent to which the work of the presently named inventors described in the background section and various aspects of this specification is performed does not indicate that it is prior art at the time of filing this application, and it is never explicitly or implicitly admitted that it is prior art for this application.

[0004] Video encoding and decoding can be performed using inter-picture prediction with motion compensation. Uncompressed digital video may include a series of pictures, each picture having spatial dimensions of, for example, 1920×1080 luma samples and associated chroma samples. The series of pictures has a fixed or variable picture rate (also informally referred to as a frame rate), such as 60 pictures per second or 60Hz. Uncompressed video has very large bitrate requirements. For example, 1080p60 4:2:0 video (1920x1080 luma sample resolution, 60Hz frame rate) with 8 bits per sample requires close to 1.5Gbit / s bandwidth. One hour of such video requires more than 600GB of storage space.

[0005] One goal of video encoding and decoding is to reduce redundant information in the input video signal through compression. Video compression can help reduce the bandwidth or storage space requirements mentioned above, in some cases by two or more orders of magnitude. Both lossless and lossy compression, as well as combinations of the two, can be used. Lossless compression refers to techniques that reconstruct an exact replica of the original signal from the compressed original signal. When lossy compression is used, the reconstructed signal may not be exactly the same as the original signal, but the distortion between the original and the reconstructed signal is small enough that the reconstructed signal can be used for the intended application. Lossy compression is widely used in video. The amount of distortion allowed depends on the application. For example, users of some consumer streaming applications may tolerate higher distortion than users of television applications. The achievable compression ratio reflects that higher allowed / tolerable distortion results in higher compression ratios.

[0006] Video encoders and decoders may utilize several broad categories of techniques including, for example: motion compensation, transforms, quantization, and entropy coding.

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

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

[0009] There can be many different forms of intra-frame prediction. When more than one such technique can be used in a given video coding technique, the techniques used can be encoded as intra-frame prediction modes. In some cases, a mode can have sub-modes and / or parameters, and these modes can be encoded separately or included in a mode codeword. Which codeword is used for a given mode, sub-mode and / or parameter combination affects the coding efficiency gain through intra-frame prediction, and therefore the entropy coding technique used to convert the codeword into a bitstream.

[0010] H.264 introduced an intra prediction mode, which was improved in H.265 and further improved in newer coding techniques such as the Joint Exploration Model (JEM), Versatile Video Coding (VVC), Benchmark Sets (BMS), etc. A prediction block can be formed by using neighboring sample values ​​belonging to samples that are already available. The sample values ​​of neighboring samples are copied to the prediction block in a certain direction. A reference to the direction used can be encoded in the bitstream or can itself be predicted.

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

[0012] Still referring to FIG. 1A , a square block (104) comprising 4×4 samples is shown at the upper left (indicated by the thick dashed line). The square block (104) consists of 16 samples, each of which is labeled with "S" and its position in the Y dimension (e.g., row index) and its position in the X dimension (e.g., column index). For example, sample S21 is the second sample in the Y dimension (starting from the top) and the first sample in the X dimension (starting from the left). Similarly, sample S44 is the fourth sample in the block (104) in both the Y dimension and the X dimension. Since the block is a 4×4 size sample, S44 is located in the lower right corner. Reference samples following a similar numbering scheme are also shown. The reference samples are labeled with "R" and their Y position (e.g., row index) and X position (e.g., column index) relative to the block (104). In H.264 and H.265, the prediction samples are adjacent to the block being reconstructed, so there is no need to use negative values.

[0013] Intra-picture prediction can be performed by copying reference sample values ​​from neighboring samples occupied by a signaled prediction direction. For example, assume that the encoded video bitstream includes signaling that, for this block, indicates a prediction direction consistent with arrow (102), i.e., the sample is predicted based on one or more prediction samples to the upper right at a 45 degree angle to the horizontal direction. In this case, samples S41, S32, S23, and S14 are predicted based on the same reference sample R05. Then, sample S44 is predicted based on reference sample R08.

[0014] In some cases, such as by interpolation, the values ​​of multiple reference samples may be combined in order to compute the reference sample, particularly when the direction is not divisible by 45 degrees.

[0015] As video coding techniques have evolved, the number of possible directions has increased. In H.264 (2003), nine different directions could be represented. This increased to 33 in H.265 (2013) and JEM / VVC / BMS, and at the time of this application, up to 65 directions can be supported. Experiments have been conducted to identify the most likely directions, and certain techniques in entropy coding are used to represent those possible directions using a small number of bits, accepting some penalty for less likely directions. Additionally, the direction itself can sometimes be predicted based on neighboring directions used in adjacent, already decoded blocks.

[0016] FIG. 1B is a schematic diagram ( 105 ) depicting 65 intra prediction directions according to JEM to illustrate the increase in the number of prediction directions over time.

[0017] The mapping of the intra prediction direction bits in the coded video bitstream representing the direction may vary from one video coding technique to another, and may, for example, range from a simple direct mapping of the prediction direction of the intra prediction mode to the codeword, to complex adaptive schemes including the most probable mode and similar techniques. However, in all cases, there may be certain directions in the video content that are statistically less likely to occur than other directions. Since the goal of video compression is to reduce redundancy, in a well-functioning video coding technique, those less likely directions will be represented using a larger number of bits than more likely directions.

[0018] Motion compensation may be a lossy compression technique and may involve the following technique: a block of sample data from a previously reconstructed picture or part thereof (reference picture), after being spatially shifted in a direction indicated by a motion vector (hereinafter MV), is used for the prediction of a newly reconstructed picture or part of a picture. In some cases, the reference picture may be the same as the picture currently being reconstructed. The MV may have two dimensions, X and Y, or three dimensions, the third dimension indicating the reference picture in use (indirectly, the latter may be the temporal dimension).

[0019] In some video compression techniques, an MV that can be applied to a certain area of ​​sample data can be predicted from other MVs, such as those MVs that are related to another area of ​​sample data that is spatially adjacent to the area being reconstructed and that precede the MV in decoding order. Doing so can significantly reduce the amount of data required to encode the MV, thereby eliminating redundancy and increasing compression. MV prediction can work effectively, for example, because when encoding an input video signal derived from a camera (called natural video), areas larger than the area where a single MV is applicable are statistically likely to move in similar directions. Therefore, in some cases these areas (areas larger than the area where a single MV is applicable) can be predicted using similar MVs derived from MVs of adjacent areas. This results in the MV found for a given area being similar or identical to the MV predicted from the surrounding MVs, and compared to encoding the MV directly, after entropy coding, the MV in turn can be represented with fewer bits than when the MV is directly encoded. In some cases, MV prediction can be an example of lossless compression of a signal (i.e., MV) derived from the original signal (i.e., sample stream). In other cases, the MV prediction itself may be lossy, for example due to rounding errors when computing the prediction value from several surrounding MVs.

[0020] Various MV prediction mechanisms are described in H.265 / HEVC (ITU-T H.265 Recommendation, "High Efficiency Video Coding", December 2016). Among the various MV prediction mechanisms provided by H.265, this application describes a technique referred to below as "spatial merging".

[0021] Referring to FIG. 1C , the current block (111) includes samples that have been discovered by the encoder during the motion search process, and the samples can be predicted based on the previous block of the same size that has generated a spatial offset. In addition, the MV can be derived from metadata associated with one or more reference pictures instead of encoding the MV directly. For example, the MV is derived from the metadata of the nearest reference picture (in decoding order) using the MV associated with any of the five surrounding samples A0, A1 and B0, B1, B2 (corresponding to 112 to 116, respectively). In H.265, MV prediction can use the prediction value of the same reference picture that the neighboring blocks are also using. Summary of the invention

[0022] Aspects of the present disclosure provide methods, devices and storage media for video encoding and decoding. A video decoding device includes a processing circuit. The processing circuit decodes prediction information of a current block in a current picture. The current picture is part of an encoded video sequence. The prediction information is used to indicate multiple combinations of processed reconstructed samples. The processing circuit performs a filtering process on the processed reconstructed sample combination of the first color component of the current block. The processing circuit determines the output value of the filtering process based on one of the following: a default value, a predicted output value, and one of the output values ​​indicated in the prediction information. The processed reconstructed sample combination of the first color is not included in the multiple combinations. The processing circuit reconstructs the current block based on the output value of the filtering process applied to the reconstructed samples of the second color component of the current block. The second color component is different from the first color component.

[0023] In one embodiment, the processing circuit determines one of a first value and a second value as the output value of the filtering process. The first value is one of the output values ​​indicated in the prediction information, and the second value is the opposite of the first value.

[0024] In one embodiment, each processed reconstructed sample in the combination of processed reconstructed samples of the first color component is the inverse of a corresponding processed reconstructed sample in one of the plurality of combinations, and one of the output values ​​corresponds to the one of the plurality of combinations.

[0025] In one embodiment, the sum of a first index of the processed reconstructed sample combination of the first color component in a mapping table of the filtering process and a second index of one of the output values ​​indicated in the prediction information in the mapping table is equal to a maximum index of the mapping table.

[0026] In one embodiment, the processing circuit determines the default value as the output value of the filtering process based on the prediction information indicating that the plurality of combinations are a subset of a total number of combinations of processed reconstructed samples in the filtering process.

[0027] In one embodiment, the predicted output value is determined by an output value of a filtering process applied to another coding block based on an output value of the filtering process.

[0028] In one embodiment, the processed reconstructed sample combination of the first color component is determined based on the reconstructed samples of the first color component output from a first encoding module, and the reconstructed samples of the second color component are output from the first encoding module or from a second encoding module applied after the first encoding module.

[0029] Aspects of the present disclosure provide a method for video decoding. In the method, prediction information of a current block in a current picture is decoded. The current picture is part of an encoded video sequence. The prediction information indicates multiple combinations of processed reconstructed samples. A filtering process is performed on the processed reconstructed sample combination of a first color component of the current block. The output value of the filtering process is determined based on one of the following: a default value, a predicted output value, and one of the output values ​​indicated in the prediction information. The processed reconstructed sample combination of the first color is not included in the multiple combinations. The output value of the filtering process is applied to the reconstructed samples of the second color component of the current block to reconstruct the current block. The second color component is different from the first color component.

[0030] Aspects of the present disclosure also provide a non-volatile computer-readable medium storing instructions, which, when executed by at least one processor, cause the at least one processor to perform any one or a combination of methods for video decoding. The present disclosure also provides a method for video encoding, comprising: obtaining prediction information of a current block in a current picture, the prediction information being used to indicate a plurality of combinations of processed reconstructed samples; performing a filtering process on a processed reconstructed sample combination of a first color component of the current block; wherein an output value of the filtering process is determined based on one of the following: a default value, a predicted output value, and one of the output values ​​indicated in the prediction information; the processed reconstructed sample combination of the first color is not included in the plurality of combinations indicated in the prediction information; and the output value of the filtering process is applied to a reconstructed sample of a second color component of the current block to reconstruct the current block, the second color component being different from the first color component. The present disclosure also provides a video encoding device, comprising a processing circuit, the processing circuit being configured to: execute a method according to an embodiment of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Additional features, properties, and various advantages of the disclosed subject matter will become more apparent from the following detailed description and accompanying drawings, in which:

[0032] FIG1A is a diagram illustrating an exemplary subset of intra prediction modes;

[0033] FIG1B is a diagram of exemplary intra prediction directions;

[0034] FIG1C is a schematic diagram of a current block and its surrounding spatial merging candidates in an example;

[0035] Figure 2 is a schematic diagram of a simplified block diagram of a communication system according to an embodiment;

[0036] Figure 3is a schematic diagram of a simplified block diagram of a communication system according to an embodiment;

[0037] Figure 4 is a schematic diagram of a simplified block diagram of a decoder according to an embodiment;

[0038] Figure 5 is a schematic diagram of a simplified block diagram of an encoder according to an embodiment;

[0039] Figure 6 shows a block diagram of an encoder according to another embodiment;

[0040] Figure 7 shows a block diagram of a decoder according to another embodiment;

[0041] FIG. 8A to FIG. 8B shows an exemplary diamond filter shape for an adaptive loop filter (ALF) according to some embodiments;

[0042] 9A to 9D shows exemplary sub-sampling positions for gradient calculation in the vertical direction, the horizontal direction, and two diagonal directions, respectively, according to some embodiments;

[0043] Fig.10 shows an exemplary modified block classification applied to a luma component according to an embodiment;

[0044] Fig.11 shows an exemplary modified ALF of a luma component at a virtual boundary according to some embodiments;

[0045] Fig.12 shows an exemplary largest coding unit (LCU) aligned picture quadtree partitioning according to an embodiment;

[0046] Fig.13 shows an exemplary quadtree split flag encoded in z-order according to an embodiment;

[0047] Fig.14A illustrates an exemplary arrangement of a cross-component adaptive loop filter (CC-ALF) according to an embodiment;

[0048] Fig. 14B shows an exemplary linear diamond filter applied to the luma channel of each chroma component during CC-ALF operation according to an embodiment;

[0049] Fig.15 illustrates exemplary positions of chroma samples relative to luma samples according to some embodiments;

[0050] Fig.16 shows an exemplary directional search of an 8×8 block according to an embodiment;

[0051] Fig.17 shows an exemplary subspace projection according to an embodiment;

[0052] Fig.18 illustrates an exemplary filter support region of a cross-component sample offset (CCSO) filter according to an embodiment;

[0053] FIG. 19A to FIG. 19B A table is shown that lists 81 exemplary combinations of nonlinear mappings in a CCSO filter according to an embodiment;

[0054] Fig.19C A table is shown according to an embodiment, which lists 40 exemplary combinations of non-linear mappings that are not signaled and can be based on Fig.19A to export the table shown in;

[0055] Fig.19D Another table according to an embodiment is shown, which lists 40 exemplary combinations of non-linear mappings that are not signaled and can be based on Fig.19A to export the table shown in;

[0056] Fig.19E shows a table listing 17 signaled combinations of non-linear mappings in a CCSO filter according to an embodiment;

[0057] Fig.19F shows a table listing 16 signaled combinations of non-linear mappings in a CCSO filter according to an embodiment;

[0058] Figure 19G shows a table listing 33 signaled combinations of non-linear mappings in a CCSO filter according to an embodiment;

[0059] Fig.19H shows a table listing 32 signaled combinations of non-linear mappings in a CCSO filter according to an embodiment;

[0060] Fig. 20 shows an exemplary flow chart according to an embodiment; and

[0061] Fig.21 is a schematic diagram of a computer system according to an embodiment. DETAILED DESCRIPTION

[0062] I. Video Decoder and Encoder Systems

[0063] Figure 22 is a simplified block diagram of a communication system (200) according to an embodiment disclosed in the present application. The communication system (200) includes a plurality of terminal devices, which can communicate with each other through, for example, a network (250). For example, the communication system (200) includes a first terminal device (210) and a second terminal device (220) interconnected through the network (250). Figure 2 In an embodiment of the present invention, the first terminal device (210) and the second terminal device (220) perform unidirectional data transmission. For example, the first terminal device (210) may encode video data (e.g., a video picture stream collected by the first terminal device (210)) for transmission to the second terminal device (220) via the network (250). The encoded video data is transmitted in the form of one or more encoded video code streams. The second terminal device (220) may receive the encoded video data from the network (250), decode the encoded video data to restore the video data, and display the video picture based on the restored video data. Unidirectional data transmission is more common in applications such as media services.

[0064] In another embodiment, the communication system (200) includes a third terminal device (230) and a fourth terminal device (240) that perform bidirectional transmission of encoded video data, which can occur, for example, during a video conference. For bidirectional data transmission, each of the third terminal device (230) and the fourth terminal device (240) can encode video data (e.g., a video picture stream collected by the terminal device) to transmit to the other terminal device of the third terminal device (230) and the fourth terminal device (240) through a network (250). Each of the third terminal device (230) and the fourth terminal device (240) can also receive the encoded video data transmitted by the other terminal device of the third terminal device (230) and the fourth terminal device (240), and can decode the encoded video data to restore the video data, and can display the video picture on an accessible display device based on the restored video data.

[0065] exist Figure 2In the embodiment of the present invention, the first terminal device (210), the second terminal device (220), the third terminal device (230) and the fourth terminal device (240) may be servers, personal computers and smart phones, but the principles disclosed in the present application may not be limited thereto. The embodiments disclosed in the present application are applicable to laptop computers, tablet computers, media players and / or dedicated video conferencing equipment. The network (250) represents any number of networks that transmit encoded video data between the first terminal device (210), the second terminal device (220), the third terminal device (230) and the fourth terminal device (240), including, for example, wired (wired) and / or wireless communication networks. The communication network (250) may exchange data in circuit switching and / or packet switching channels. The network may include a telecommunications network, a local area network, a wide area network and / or the Internet. For the purpose of the present application, unless explained below, the architecture and topology of the network (250) may be irrelevant to the operation disclosed in the present application.

[0066] As an example, Figure 3 The video encoder and video decoder are shown in a streaming environment. The subject matter disclosed in this application is equally applicable to other video-enabled applications, including, for example, video conferencing, digital TV, storing compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0067] The streaming system may include an acquisition subsystem (313), which may include a video source (301) such as a digital camera, which creates an uncompressed video picture stream (302). In an embodiment, the video picture stream (302) includes samples taken by a digital camera. Compared to the encoded video data (304) (or the encoded video bitstream), the video picture stream (302) is depicted as a thick line to emphasize the high data volume of the video picture stream, and the video picture stream (302) can be processed by an electronic device (320), which includes a video encoder (303) coupled to the video source (301). The video encoder (303) may include hardware, software, or a combination of hardware and software to implement or implement various aspects of the disclosed subject matter as described in more detail below. Compared to the video picture stream (302), the encoded video data (304) (or the encoded video bitstream (304)) is depicted as a thin line to emphasize the lower amount of data of the encoded video data (304) (or the encoded video bitstream (304)), which can be stored on the streaming server (305) for future use. One or more streaming client subsystems, such as Figure 3The client subsystem (306) and the client subsystem (308) in the video transmission system can access the streaming server (305) to retrieve the copy (307) and the copy (309) of the encoded video data (304). The client subsystem (306) may include, for example, a video decoder (310) in the electronic device (330). The video decoder (310) decodes the incoming copy (307) of the encoded video data and generates an output video picture stream (311) that can be presented on a display (312) (e.g., a display screen) or another presentation device (not depicted). In some streaming transmission systems, the encoded video data (304), the video data (307), and the video data (309) (e.g., a video bitstream) can be encoded according to certain video encoding / compression standards. Examples of these standards include ITU-T H.265. In an embodiment, the video coding standard under development is informally referred to as Versatile Video Coding (VVC), and the present application can be used in the context of the VVC standard.

[0068] It should be noted that the electronic device (320) and the electronic device (330) may include other components (not shown). For example, the electronic device (320) may include a video decoder (not shown), and the electronic device (330) may also include a video encoder (not shown).

[0069] Figure 4 4 is a block diagram of a video decoder (410) according to an embodiment disclosed in the present application. The video decoder (410) may be provided in an electronic device (430). The electronic device (430) may include a receiver (431) (e.g., a receiving circuit). The video decoder (410) may be used to replace Figure 3 A video decoder (510) of an embodiment.

[0070] The receiver (431) may receive one or more encoded video sequences to be decoded by the video decoder (410); in the same or another embodiment, one encoded video sequence is received at a time, wherein the decoding of each encoded video sequence is independent of the other encoded video sequences. The encoded video sequence may be received from a channel (401), which may be a hardware / software link to a storage device storing the encoded video data. The receiver (431) may receive the encoded video data as well as other data, such as encoded audio data and / or auxiliary data streams that may be forwarded to their respective consuming entities (not shown). The receiver (431) may separate the encoded video sequence from the other data. To prevent network jitter, a buffer memory (415) may be coupled between the receiver (431) and the entropy decoder / parser (420) (hereinafter referred to as "parser (420)"). In some applications, the buffer memory (415) is part of the video decoder (410). In other cases, the buffer memory (415) may be provided external to the video decoder (410) (not shown). In other cases, a buffer memory (not shown) is provided outside the video decoder (410) to prevent network jitter, for example, and another buffer memory (415) may be configured inside the video decoder (410) to handle broadcast timing, for example. When the receiver (431) receives data from a storage / forward device with sufficient bandwidth and controllability or from an isochronous network, it may not be necessary to configure the buffer memory (415), or the buffer memory may be made smaller. Of course, in order to use on a service packet network such as the Internet, a buffer memory (415) may also be required, and the buffer memory may be relatively large and have an adaptive size, and may be at least partially implemented in an operating system or a similar element (not shown) outside the video decoder (410).

[0071] The video decoder (410) may include a parser (420) to reconstruct symbols (421) from the encoded video sequence. The types of symbols include information used to manage the operation of the video decoder (410) and potential information used to control a display device such as a display device (412) (e.g., a display screen) that is not part of the electronic device (430) but can be coupled to the electronic device (430), such as Figure 4As shown in . The control information for the display device may be a parameter set fragment (not indicated) of Supplemental Enhancement Information (SEI message) or Video Usability Information (VUI). The parser (420) may parse / entropy decode the received coded video sequence. The encoding of the coded video sequence may be performed according to a video coding technique or standard, and may follow various principles, including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, and the like. The parser (420) may extract a subgroup parameter set of at least one subgroup of the subgroups of pixels in the video decoder from the coded video sequence based on at least one parameter corresponding to the group. The subgroup may include a Group of Pictures (GOP), a picture, a tile, a slice, a macroblock, a Coding Unit (CU), a block, a Transform Unit (TU), a Prediction Unit (PU), and the like. The parser (420) may also extract information from the encoded video sequence, such as transform coefficients, quantizer parameter values, MVs, and so on.

[0072] The parser (420) may perform entropy decoding / parsing operations on the video sequence received from the buffer memory (415), thereby creating symbols (421).

[0073] Depending on the type of coded video picture or portion of coded video picture (e.g., inter- and intra-pictures, inter- and intra-blocks) and other factors, the reconstruction of the symbol (421) may involve multiple different units. Which units are involved and how they are involved may be controlled by subgroup control information parsed by the parser (420) from the coded video sequence. For the sake of brevity, such subgroup control information flow between the parser (420) and the multiple units below is not described.

[0074] In addition to the functional blocks already mentioned, the video decoder (410) can be conceptually subdivided into several functional units as described below. In a practical embodiment operating under commercial constraints, many of these units interact closely with each other and can be integrated with each other. However, for the purpose of describing the disclosed subject matter, the conceptual subdivision into the following functional units is appropriate.

[0075] The first unit is a sealer / inverse transform unit (451). The sealer / inverse transform unit (451) receives quantized transform coefficients as symbols (421) from the parser (420) and control information, including which transform method to use, block size, quantization factor, quantization scaling matrix, etc. The sealer / inverse transform unit (451) can output a block including sample values, which can be input into an aggregator (455).

[0076] In some cases, the output samples of the sealer / inverse transform unit (451) may belong to an intra-coded block; that is, a block that does not use predictive information from a previously reconstructed picture, but may use predictive information from a previously reconstructed portion of the current picture. Such predictive information may be provided by an intra-picture prediction unit (452). In some cases, the intra-picture prediction unit (452) generates surrounding blocks of the same size and shape as the block being reconstructed using reconstructed information extracted from the current picture buffer (458). For example, the current picture buffer (458) buffers a partially reconstructed current picture and / or a fully reconstructed current picture. In some cases, the aggregator (455) adds the prediction information generated by the intra-picture prediction unit (452) to the output sample information provided by the sealer / inverse transform unit (451) on a per-sample basis.

[0077] In other cases, the output samples of the scaler / inverse transform unit (451) may belong to inter-frame coded and potentially motion compensated blocks. In this case, the motion compensated prediction unit (453) may access the reference picture memory (457) to extract samples for prediction. After the extracted samples are motion compensated according to the symbols (421), these samples may be added to the output of the scaler / inverse transform unit (451) (in this case referred to as residual samples or residual signals) by the aggregator (455) to generate output sample information. The acquisition of prediction samples by the motion compensated prediction unit (453) from the address in the reference picture memory (457) may be controlled by a motion vector, and the motion vector is provided to the motion compensated prediction unit (453) in the form of the symbols (421), for example, including X, Y and reference picture components. Motion compensation may also include interpolation of sample values ​​extracted from the reference picture memory (457) when using sub-sample accurate motion vectors, motion vector prediction mechanisms, and the like.

[0078] The output samples of the aggregator (455) may be employed by various loop filtering techniques in a loop filter unit (454). The video compression techniques may include in-loop filter techniques controlled by parameters included in the encoded video sequence (also referred to as the encoded video bitstream) and available to the loop filter unit (456) as symbols (421) from the parser (420). However, in other embodiments, the video compression techniques may also be responsive to meta-information obtained during decoding of a previous (in decoding order) portion of an encoded picture or encoded video sequence, as well as to previously reconstructed and loop filtered sample values.

[0079] The output of the loop filter unit (456) may be a sample stream that may be output to a display device (412) and stored in a reference picture memory (457) for subsequent inter-picture prediction.

[0080] Once fully reconstructed, certain coded pictures may be used as reference pictures for future prediction. For example, once the coded picture corresponding to the current picture is fully reconstructed, and the coded picture is identified as a reference picture (e.g., by the parser (420)), the current picture buffer (458) may become part of the reference picture memory (457), and a new current picture buffer may be reallocated before starting to reconstruct a subsequent coded picture.

[0081] The video decoder (410) may perform decoding operations according to a predetermined video compression technique, such as in the ITU-T H.265 standard. The encoded video sequence may conform to the syntax specified by the video compression technique or standard used in the sense that the encoded video sequence follows the syntax of the video compression technique or standard and the profile recorded in the video compression technique or standard. Specifically, the profile may select certain tools from all the tools available in the video compression technique or standard as the only tools available for use under the profile. For compliance, the complexity of the encoded video sequence is also required to be within the range defined by the hierarchy of the video compression technique or standard. In some cases, the hierarchy limits the maximum picture size, the maximum frame rate, the maximum reconstruction sampling rate (measured in, for example, mega samples per second), the maximum reference picture size, etc. In some cases, the limits set by the hierarchy may be further limited by the Hypothetical Reference Decoder (HRD) specification and metadata of the HRD buffer management signaled in the encoded video sequence.

[0082] In an embodiment, the receiver (431) may receive additional (redundant) data along with the encoded video. The additional data may be part of the encoded video sequence. The additional data may be used by the video decoder (410) to properly decode the data and / or more accurately reconstruct the original video data. The additional data may be in the form of, for example, temporal, spatial or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, etc.

[0083] Figure 5 1 is a block diagram of a video encoder (503) according to an embodiment disclosed in the present application. The video encoder (503) is provided in an electronic device (520). The electronic device (520) includes a transmitter (540) (e.g., a transmission circuit). The video encoder (503) can be used to replace Figure 3 A video encoder (303) in an embodiment.

[0084] The video encoder (503) can be used to obtain the video source (501) (not Figure 5 In another embodiment, the video source (501) is a part of the electronic device (520) to receive video samples, and the video source can collect video images to be encoded by the video encoder (503). In another embodiment, the video source (501) is a part of the electronic device (520).

[0085] The video source (501) may provide a source video sequence in the form of a digital video sample stream to be encoded by the video encoder (503), wherein the digital video sample stream may have any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, ...), any color space (e.g., BT.601 Y CrCB, RGB, ...), and any suitable sampling structure (e.g., Y CrCb 4:2:0, Y CrCb 4:4:4). In a media service system, the video source (501) may be a storage device storing previously prepared videos. In a video conferencing system, the video source (501) may be a camera that captures local image information as a video sequence. The video data may be provided as a plurality of separate pictures that are given motion when viewed sequentially. The pictures themselves may be constructed as a spatial pixel array, wherein each pixel may include one or more samples depending on the sampling structure, color space, etc. used. The relationship between pixels and samples may be easily understood by those skilled in the art. The following description focuses on the samples.

[0086] According to an embodiment, the video encoder (503) may encode and compress pictures of a source video sequence into an encoded video sequence (543) in real time or under any other time constraints required by the application. Implementing an appropriate encoding speed is a function of the controller (550). In some embodiments, the controller (550) controls other functional units as described below and is functionally coupled to these units. For the sake of brevity, couplings are not shown in the figure. The parameters set by the controller (550) may include rate control related parameters (picture skipping, quantizer, lambda value of rate distortion optimization technology, etc.), picture size, group of pictures (GOP) layout, maximum motion vector reference area allowed, etc. The controller (550) can be used to have other suitable functions that are related to the video encoder (503) optimized for a certain system design.

[0087] In some embodiments, the video encoder (503) operates in a coding loop. As a simple description, in embodiments, the coding loop may include a source encoder (530) (e.g., responsible for creating symbols, such as a symbol stream, based on an input picture to be encoded and a reference picture) and a (local) decoder (533) embedded in the video encoder (503). The decoder (533) reconstructs the symbols to create sample data in a manner similar to how the (remote) decoder creates sample data (because in the video compression technology considered in this application, any compression between the symbols and the encoded video code stream is lossless). The reconstructed sample stream (sample data) is input to a reference picture memory (534). Since the decoding of the symbol stream produces bit-accurate results that are independent of the decoder location (local or remote), the contents of the reference picture memory (534) are also bit-accurate between the local encoder and the remote encoder. In other words, the reference picture samples "seen" by the prediction part of the encoder are exactly the same as the sample values ​​that the decoder will "see" when using the prediction during decoding. This basic principle of reference picture synchronization (and the drift that occurs when synchronization cannot be maintained, eg due to channel errors) is also used in some related techniques.

[0088] The operation of the "local" decoder (533) may be combined with, for example, Figure 4 The "remote" decoder described in detail for the video decoder (410) is identical. However, additional brief reference is made to Figure 4 , when symbols are available and the entropy encoder (545) and parser (420) are capable of losslessly encoding / decoding the symbols into an encoded video sequence, the entropy decoding portion of the video decoder (410), including the buffer memory (415) and the parser (420), may not be fully implemented in the local decoder (533).

[0089] At this point, it can be observed that any decoder technology other than the parsing / entropy decoding present in the decoder must also be present in the corresponding encoder in substantially the same functional form. For this reason, the present application focuses on decoder operation. The description of encoder technology can be simplified because encoder technology is mutually inverse to the decoder technology described comprehensively. A more detailed description is only needed in certain areas and is provided below.

[0090] During operation, in some embodiments, the source encoder (530) may perform motion compensated predictive coding. The motion compensated predictive coding predictively encodes an input picture with reference to one or more previously encoded pictures from a video sequence designated as "reference pictures." In this manner, the encoding engine (532) encodes the differences between pixel blocks of the input picture and pixel blocks of a reference picture that may be selected as a prediction reference for the input picture.

[0091] The local video decoder (533) may decode the encoded video data of the picture that may be designated as the reference picture based on the symbol created by the source encoder (530). The operation of the encoding engine (532) may be a lossy process. When the encoded video data is available at the video decoder ( Figure 5 When the video sequence is decoded at a remote location (not shown), the reconstructed video sequence may typically be a copy of the source video sequence with some errors. The local video decoder (533) replicates the decoding process that may be performed by the video decoder on the reference picture and may cause the reconstructed reference picture to be stored in the reference picture cache (534). In this way, the video encoder (503) may locally store a copy of the reconstructed reference picture that has common content (absent transmission errors) with the reconstructed reference picture to be obtained by the remote video decoder.

[0092] The predictor (535) may perform a prediction search for the encoding engine (532). That is, for a new picture to be encoded, the predictor (535) may search the reference picture memory (534) for sample data (as candidate reference pixel blocks) or certain metadata, such as reference picture motion vectors, block shapes, etc., that may serve as appropriate prediction references for the new picture. The predictor (535) may operate pixel-by-pixel based on sample blocks to find a suitable prediction reference. In some cases, based on the search results obtained by the predictor (535), it may be determined that the input picture may have prediction references taken from a plurality of reference pictures stored in the reference picture memory (534).

[0093] The controller (550) may manage encoding operations of the source encoder (530), including, for example, setting parameters and subgroup parameters for encoding video data.

[0094] The outputs of all the above functional units may be entropy encoded in an entropy encoder (545). The entropy encoder (545) performs lossless compression on the symbols generated by the various functional units according to techniques such as Huffman coding, variable length coding, arithmetic coding, etc., thereby converting the symbols into a coded video sequence.

[0095] The transmitter (540) may buffer the encoded video sequence created by the entropy encoder (545) in preparation for transmission over a communication channel (560), which may be a hardware / software link to a storage device where the encoded video data will be stored. The transmitter (540) may combine the encoded video data from the video encoder (503) with other data to be transmitted, such as encoded audio data and / or ancillary data streams (source not shown).

[0096] The controller (550) may manage the operation of the video encoder (503). During encoding, the controller (550) may assign a certain coded picture type to each coded picture, but this may affect the coding techniques that can be applied to the corresponding picture. For example, a picture may generally be assigned to any of the following picture types:

[0097] An intra picture (I picture) may be a picture that can be encoded and decoded without using any other picture in the sequence as a prediction source. Some video codecs allow different types of intra pictures, including, for example, Independent Decoder Refresh ("IDR") pictures. Those skilled in the art are aware of the variations of I pictures and their corresponding applications and features.

[0098] A predictive picture (P picture) may be a picture that can be encoded and decoded using intra prediction or inter prediction, which uses at most one motion vector and a reference index to predict sample values ​​for each block.

[0099] Bidirectional predictive pictures (B pictures), which can be pictures that can be encoded and decoded using intra prediction or inter prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multiple predictive pictures can use more than two reference pictures and associated metadata for reconstruction of a single block.

[0100] The source picture may typically be spatially subdivided into blocks of samples (e.g., blocks of 4×4, 8×8, 4×8, or 16×16 samples), and coded block by block. These blocks may be predictively coded with reference to other (already coded) blocks, which are determined according to the coding allocation applied to the block's corresponding picture. For example, blocks of an I picture may be non-predictively coded, or the blocks may be predictively coded (spatial prediction or intra prediction) with reference to already coded blocks of the same picture. Blocks of pixels of a P picture may be predictively coded by spatial prediction with reference to one previously coded reference picture or by temporal prediction. Blocks of a B picture may be predictively coded by spatial prediction with reference to one or two previously coded reference pictures or by temporal prediction.

[0101] The video encoder (503) may perform encoding operations according to a predetermined video encoding technique or standard, such as ITU-T H.265 Recommendation. In operation, the video encoder (503) may perform various compression operations, including predictive encoding operations that exploit temporal and spatial redundancy in an input video sequence. Thus, the encoded video data may conform to the syntax specified by the video encoding technique or standard used.

[0102] In an embodiment, the transmitter (540) may transmit additional data when transmitting the encoded video. The source encoder (530) may include such data as part of the encoded video sequence. The additional data may include other forms of redundant data such as temporal / spatial / SNR enhancement layers, redundant pictures and slices, SEI messages, VUI parameter set fragments, etc.

[0103] The captured video may be taken as a plurality of source pictures (video pictures) in a temporal sequence. Intra-picture prediction (often simplified to intra-prediction) exploits spatial correlations in a given picture, while inter-picture prediction exploits (temporal or other) correlations between pictures. In an embodiment, a particular picture being encoded / decoded is divided into blocks, and the particular picture being encoded / decoded is referred to as the current picture. When a block in the current picture is similar to a reference block in a reference picture that was previously encoded in the video and is still buffered, the block in the current picture may be encoded by a vector called a motion vector. The motion vector points to a reference block in a reference picture, and in the case where multiple reference pictures are used, the motion vector may have a third dimension that identifies the reference picture.

[0104] In some embodiments, bidirectional prediction techniques may be used in inter-picture prediction. According to the bidirectional prediction technique, two reference pictures are used, for example, a first reference picture and a second reference picture that are both before the current picture in the video in decoding order (but may be in the past and future in display order, respectively). A block in the current picture may be encoded by a first motion vector pointing to a first reference block in the first reference picture and a second motion vector pointing to a second reference block in the second reference picture. Specifically, the block may be predicted by a combination of the first reference block and the second reference block.

[0105] In addition, merge mode technology can be used in inter-picture prediction to improve coding efficiency.

[0106] According to some embodiments disclosed in the present application, predictions such as inter-picture prediction and intra-picture prediction are performed in blocks. For example, according to the HEVC standard, pictures in a video picture sequence are divided into coding tree units (CTUs) for compression, and the CTUs in the pictures have the same size, such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTU includes three coding tree blocks (CTBs), which are a luminance CTB and two chrominance CTBs. Furthermore, each CTU can be split into one or more coding units (CUs) using a quadtree. For example, a 64×64 pixel CTU can be split into a 64×64 pixel CU, or 4 32×32 pixel CUs, or 16 16×16 pixel CUs. In an embodiment, each CU is analyzed to determine the prediction type for the CU, such as an inter-prediction type or an intra-prediction type. In addition, depending on temporal and / or spatial predictability, the CU is split into one or more prediction units (PUs). Typically, each PU includes a luminance prediction block (PB) and two chrominance PBs. In an embodiment, the prediction operation in encoding (encoding / decoding) is performed in units of prediction blocks. Taking the luminance prediction block as an example of a prediction block, the prediction block includes a matrix of pixel values ​​(e.g., luminance values), such as 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, and the like.

[0107] Figure 6 1 is a diagram of a video encoder (603) according to another embodiment disclosed in the present application. The video encoder (603) is used to receive a processed block (e.g., a prediction block) of sample values ​​in a current video picture in a video picture sequence, and encode the processed block into an encoded picture that is part of an encoded video sequence. In this embodiment, the video encoder (603) is used to replace Figure 3A video encoder (303) in an embodiment.

[0108] In an HEVC embodiment, a video encoder (603) receives a matrix of sample values ​​for a processing block, such as a prediction block of 8×8 samples. The video encoder (603) uses, for example, rate-distortion optimization to determine whether to use intra mode, inter mode, or bidirectional prediction mode to encode the processing block. When encoding the processing block in intra mode, the video encoder (603) may use intra prediction techniques to encode the processing block into an encoded picture; and when encoding the processing block in inter mode or bidirectional prediction mode, the video encoder (603) may use inter prediction or bidirectional prediction techniques to encode the processing block into an encoded picture, respectively. In some video encoding techniques, the merge mode may be an inter-picture prediction submode, in which a motion vector is derived from one or more motion vector predictors without the aid of an encoded motion vector component external to the predictor. In some other video encoding techniques, there may be a motion vector component applicable to the subject block. In an embodiment, the video encoder (603) includes other components, such as a mode decision module (not shown) for determining the processing block mode.

[0109] exist Figure 6 In an embodiment of the present invention, the video encoder (603) includes: Figure 6 Shown are an inter-frame encoder (630), an intra-frame encoder (622), a residual calculator (623), a switch (626), a residual encoder (624), a common controller (621), and an entropy encoder (625) coupled together.

[0110] The inter-frame encoder (630) is used to receive samples of a current block (e.g., a processing block), compare the block with one or more reference blocks in a reference picture (e.g., blocks in a previous picture and a subsequent picture), generate inter-frame prediction information (e.g., redundant information description according to an inter-frame coding technique, motion vectors, merge mode information), and calculate an inter-frame prediction result (e.g., a prediction block) based on the inter-frame prediction information using any suitable technique. In some embodiments, the reference picture is a decoded reference picture decoded based on the encoded video information.

[0111] The intra-frame encoder (622) is used to receive samples of a current block (e.g., a processing block), compare the block with an encoded block in the same picture in some cases, generate quantization coefficients after transformation, and in some cases also generate intra-frame prediction information (e.g., intra-frame prediction direction information according to one or more intra-frame coding techniques). In an embodiment, the intra-frame encoder (622) also calculates an intra-frame prediction result (e.g., a prediction block) based on the intra-frame prediction information and a reference block in the same picture.

[0112] The general controller (621) is used to determine the general control data and control other components of the video encoder (603) based on the general control data. In an embodiment, the general controller (621) determines the mode of the block and provides a control signal to the switch (626) based on the mode. For example, when the mode is intra mode, the general controller (621) controls the switch (626) to select the intra mode result for use by the residual calculator (623) and controls the entropy encoder (625) to select the intra prediction information and add the intra prediction information to the bitstream; and when the mode is inter mode, the general controller (621) controls the switch (626) to select the inter prediction result for use by the residual calculator (623) and controls the entropy encoder (625) to select the inter prediction information and add the inter prediction information to the bitstream.

[0113] The residual calculator (623) is used to calculate the difference (residual data) between the received block and the prediction result selected from the intra-frame encoder (622) or the inter-frame encoder (630). The residual encoder (624) is used to operate based on the residual data to encode the residual data to generate a transform coefficient. In an embodiment, the residual encoder (624) is used to convert the residual data from the time domain to the frequency domain and generate a transform coefficient. The transform coefficient is then processed by quantization to obtain a quantized transform coefficient. In various embodiments, the video encoder (603) also includes a residual decoder (628). The residual decoder (628) is used to perform an inverse transform and generate decoded residual data. The decoded residual data can be used appropriately by the intra-frame encoder (622) and the inter-frame encoder (630). For example, the inter-frame encoder (630) can generate a decoded block based on the decoded residual data and the inter-frame prediction information, and the intra-frame encoder (622) can generate a decoded block based on the decoded residual data and the intra-frame prediction information. The decoded blocks are appropriately processed to generate a decoded picture, and in some embodiments, the decoded picture may be buffered in a memory circuit (not shown) and used as a reference picture.

[0114] The entropy encoder (625) is used to format the code stream to produce an encoded block. The entropy encoder (625) generates various information according to a suitable standard such as HEVC. In an embodiment, the entropy encoder (625) is used to obtain general control data, selected prediction information (such as intra-frame prediction information or inter-frame prediction information), residual information, and other suitable information in the code stream. It should be noted that according to the disclosed subject matter, when the block is encoded in the inter-frame mode or the merge sub-mode of the bidirectional prediction mode, there is no residual information.

[0115] Figure 7FIG. 7 is a diagram of a video decoder (710) according to another embodiment disclosed in the present application. The video decoder (710) is used to receive an encoded image as part of an encoded video sequence and decode the encoded image to generate a reconstructed picture. In an embodiment, the video decoder (710) is used to replace Figure 3 A video decoder (310) of an embodiment.

[0116] exist Figure 7 In one embodiment, the video decoder (710) includes: Figure 7 An entropy decoder (771), an inter-frame decoder (780), a residual decoder (773), a reconstruction module (774) and an intra-frame decoder (772) coupled together are shown in FIG.

[0117] The entropy decoder (771) may be used to reconstruct certain symbols from the encoded picture, which represent syntax elements constituting the encoded picture. Such symbols may include, for example, a mode for encoding the block (e.g., intra mode, inter mode, bidirectional prediction mode, a merged sub-mode of the latter two, or another sub-mode), prediction information (e.g., intra prediction information or inter prediction information) that may identify certain samples or metadata for prediction by the intra decoder (772) or the inter decoder (780), respectively, residual information in the form of, for example, quantized transform coefficients, and the like. In an embodiment, when the prediction mode is inter or bidirectional prediction mode, the inter prediction information is provided to the inter decoder (780); and when the prediction type is an intra prediction type, the intra prediction information is provided to the intra decoder (772). The residual information may be inverse quantized and provided to the residual decoder (773).

[0118] The inter-frame decoder (780) is used for receiving the inter-frame prediction information and generating an inter-frame prediction result based on the inter-frame prediction information.

[0119] The intra-frame decoder (772) is used to receive intra-frame prediction information and generate a prediction result based on the intra-frame prediction information.

[0120] The residual decoder (773) is used to perform inverse quantization to extract dequantized transform coefficients, and process the dequantized transform coefficients to convert the residual from the frequency domain to the spatial domain. The residual decoder (773) may also require some control information (to obtain the quantizer parameter QP), and this information can be provided by the entropy decoder (771) (the data path is not indicated because this is only low-volume control information).

[0121] The reconstruction module (774) is used to combine the residual output by the residual decoder (773) with the prediction result (which can be output by the inter-frame prediction module or the intra-frame prediction module) in the spatial domain to form a reconstructed block, which can be part of a reconstructed picture, which in turn can be part of a reconstructed video. It should be noted that other suitable operations such as deblocking operations can be performed to improve visual quality.

[0122] It should be noted that the video encoder (303), video encoder (503) and video encoder (603), and video decoder (310), video decoder (410) and video decoder (710) may be implemented using any suitable technology. In an embodiment, the video encoder (303), video encoder (503) and video encoder (603), and video decoder (310), video decoder (410) and video decoder (710) may be implemented using one or more integrated circuits. In another embodiment, the video encoder (303), video encoder (503) and video encoder (603), and video decoder (310), video decoder (410) and video decoder (710) may be implemented using one or more processors that execute software instructions.

[0123] II. Adaptive Loop Filter

[0124] In some related examples such as VVC draft 8, an adaptive loop filter (ALF) with block-based filter adaptation can be applied. For the luma component, one of 25 filters can be selected for each 4×4 block based on its directionality and local gradient activity.

[0125] FIG. 8A to FIG. 8B An exemplary diamond filter shape for an ALF according to some embodiments of the present disclosure is shown. Fig. 8A shows a 5×5 diamond shape that can be applied to the chroma components, and Figure 8B A 7×7 diamond shape is shown that may be applied to the luma component.

[0126] In some related examples, for the luma component, each 4×4 block can be classified into one of 25 categories. The quantized value and directionality D of the 4×4 block are derived as follows:

[0127] In order to calculate D and The 1-D Laplacian operator can be used to first calculate the gradients in the horizontal, vertical, and two diagonal directions of the 4×4 block as follows: where indices i and j refer to the coordinates of the top left sample within the 4×4 block, and R(i,j) indicates the reconstructed sample at coordinate (i,j).

[0128] To reduce the complexity of block classification, a sub-sampled 1-D Laplacian calculation may be applied. 9A to 9D Exemplary sub-sampling positions for gradient calculation in the vertical direction, the horizontal direction, and the two diagonal directions are shown, respectively.

[0129] Then, the maximum and minimum values ​​of the horizontal and vertical gradients can be set as:

[0130] The maximum and minimum values ​​of the gradients in the two diagonal directions can be set as:

[0131] In order to derive a value for the directivity D, these values ​​can be compared with one another and with two threshold values ​​t1 and t2 .

[0132] Step 1: If and If both are true, D is set to 0.

[0133] Step 2: If Continue from step 3; otherwise, continue from step 4.

[0134] Step 3: If If yes, set D to 2; otherwise, set D to 1.

[0135] Step 4: If Then set D to 4; otherwise, set D to 3.

[0136] The activity value A is calculated as:

[0137] A is further quantized to the range of 0 to 4 (inclusive), and the quantized value is represented as

[0138] No classification method is applied to the chrominance components in the picture. For example, a single set of ALF coefficients may be applied to each chrominance component.

[0139] Before filtering each 4×4 luma block, geometric transformations such as rotation, diagonal flipping, 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 respective blocks. This is equivalent to applying these transformations to the samples in the filter support area in order to make different blocks where the ALF is applied more similar by aligning the direction of the ALF.

[0140] The three geometric transformations (including diagonal flipping, vertical flipping, and rotation) can be described as follows: Diagonal: f D (k,l)=f(l,k),c D (k,l)=c(l,k)Equation (11) Flip vertically: f V (k,l)=f(k,Kl-1),c V (k, l) = c(k, Kl-1) Equation (12) Rotation: f R (k,l)=f(Kl-1,k),c R (k, l) = c(Kl-1, k) Equation (13) where K is the size of the filter and 0≤k, l≤K-1 are the coordinates of the transform coefficients such that the position (0, 0) is at the upper left corner and the position (K-1, K-1) is at the lower right corner. The filter coefficients f(k, l) and the clipping values ​​c(k, l) are transformed according to the gradient values ​​calculated for the corresponding block. The relationship between the transform and the gradients in the four directions can be summarized in Table 1. Table 1 Gradient Value Transform <![CDATA[g d2 <g d1 And g h <g v ]]> No transformation <![CDATA[g d2 <g d1 And g v <g h ]]> diagonal <![CDATA[g d1 <g d2 And g h <g v ]]> Flip Vertically <![CDATA[g d1 <g d2 And g v <g h ]]> Rotation

[0141] In some related examples such as VVC Draft 8, the filter parameters of ALF are signaled in an adaptive parameter set (APS). In one APS, up to 25 groups of luminance filter coefficients and clipping value indices, and up to 8 groups of chrominance filter coefficients and clipping value indices can be signaled. In order to reduce bit overhead, filter coefficients of different classifications of luminance components can be merged. In the slice header, the index of the APS for the current slice is signaled. In VVC Draft 8, the signaling of ALF is based on CTU.

[0142] The clip value index decoded from the APS allows the clip value to be determined using the clip value tables for the luminance component and the chrominance component. These clip values ​​depend on the internal bit depth. For example, the clip value table can be obtained by the following formula: AlfClip = {round(2 B-α*n ) for n∈[0..N-1]} Equation (14) Where B is equal to the internal bit depth, α is a predefined constant value equal to 2.35, and N is equal to 4, which is the number of clipping values ​​allowed in VVC draft 8. Table 2 shows an example of the output of equation (14). Table 2

[0143] In the slice header, up to 7 APS indices can be signaled to specify the luma filter set for the current slice. The filtering process can be further controlled at the CTB level. A flag can be signaled to indicate whether the ALF is applied to the luma CTB. The luma CTB can select a filter set from 16 fixed filter sets and the filter set from the APS. The filter set index for the luma CTB is signaled to indicate which filter set is applied. 16 fixed filter sets are predefined and hard-coded in the encoder and decoder.

[0144] For chroma components, an APS index may be signaled in the slice header to indicate the chroma filter set used for the current slice. At the CTB level, if more than one chroma filter set exists in the APS, the filter index for each chroma CTB may be signaled.

[0145] The filter coefficients may be quantized with a norm equal to 128. To limit the complexity of the multiplication operation, code stream consistency may be applied so that the coefficient values ​​at non-center positions may be in the range of -27 to 27-1 (inclusive). The center position coefficients are not signaled in the code stream and are considered equal to 128.

[0146] In some relevant examples such as VVC Draft 8, the syntax and semantics of the slice index and corresponding values ​​may be defined as follows.

[0147] alf_luma_clip_idx[sfIdx][j] specifies the clip index of the clip value to be used before multiplying the jth coefficient of the signaled luma filter indicated by sfIdx. A codestream conformance requirement is that the value of alf_luma_clip_idx[sfIdx][j] with sfIdx=0..alf_luma_num_filters_signalled_minus1 and j=0..11 shall be in the range of 0 to 3 (inclusive).

[0148] With bitDepth set equal to BitDepthY and clipIdx set to alf_luma_clip_idx[alf_luma_coeff_delta_idx[filtIdx]][j], the luma filter clipping values ​​AlfClipL[adaptation_parameter_set_id][filtIdx]][j] with elements AlfClipL[adaptation_parameter_set_id][filtIdx][j] (where filtIdx = 0..NumAlfFilters-1 and j = 0..11) are derived in Table 2.

[0149] alf_chroma_clip_idx[altIdx][j] specifies the clip index of the clip value to be used before multiplying the j-th coefficient of the optional chroma filter with index altIdx. A codestream conformance requirement is that the value of alf_chroma_clip_idx[altIdx][j] (where altIdx = 0.. alf_chroma_num_alt_filters_minus1, j = 0..5) should be in the range of 0 to 3 (inclusive).

[0150] Based on bitDepth being set equal to BitDepthC and clipIdx being set equal to alf_chroma_clip_idx[altIdx][j], the chroma filter clipping values ​​AlfClipC[adaptation_parameter_set_id][altIdx][j] with elements AlfClipC[adaptation_parameter_set_id][altIdx][j] (where altIdx=0..alf_chroma_num_alt_filters_minus1, j=0..5) are derived in Table 2.

[0151] At the decoder side, when ALF is enabled for a CTB, each sample R(i,j) within the CU is filtered, resulting in a corresponding sample value R′(i,j) as shown below. 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 =min(y,max(-y,x)), which corresponds to the function Clip3(-y,y,x). By incorporating the clipping function, the loop filtering method becomes a nonlinear process, known as nonlinear ALF. The selected clipping value is encoded in the "alf_data" syntax element using a Golomb coding scheme corresponding to the index of the clipping value in Table 2. This coding scheme is the same as the coding scheme used for the filter index.

[0152] Fig.10 An exemplary modified block classification applied to the luma component according to an embodiment of the present disclosure is shown. The modified block classification and filtering, for samples near the horizontal CTU boundary, can reduce the line buffer requirements of the ALF. Fig.10As shown in , a virtual boundary is defined as a line by shifting the horizontal CTU boundary with "N" samples, where N is equal to 4 for the luma component and N is equal to 2 for the chroma components.

[0153] For the computation of the 1D Laplacian gradient of the 4×4 block above the virtual boundary, only the samples above the virtual boundary are used. Similarly, for the computation of the 1D Laplacian gradient of the 4×4 block below the virtual boundary, only the samples below the virtual boundary are used. Considering the reduced number of samples used in the 1D Laplacian gradient computation, the quantization of the activity value A is scaled accordingly.

[0154] Fig.11 FIG. 4 shows a modified ALF of a luma component at an exemplary virtual boundary according to some embodiments. For filtering, a symmetric filling operation at the virtual boundary can be used for both luma and chroma components. Fig.11 As shown in , when the filtered sample is below the virtual boundary, the adjacent samples above the virtual boundary are filled in. At the same time, the corresponding samples on the other side are also filled symmetrically.

[0155] In order to improve the coding efficiency, ALP based on the coding unit synchronization picture quadtree is used in some related examples. The luma picture is divided into several multi-level quadtree partitions, and each partition boundary is aligned with the boundary of the largest coding unit (LCU). Each partition has its own filtering process and can therefore be called a filter unit (FU).

[0156] The 2-pass encoding flow is described as follows. In the first pass, the quadtree partitioning mode and the best filter for each FU are determined. During the decision process, the filter distortion is estimated by fast filter distortion estimation (FFDE). According to the determined quadtree partitioning mode and the selected filters for all FUs, the reconstructed picture is filtered. In the second pass, CU synchronous ALF on / off control is performed. According to the ALF on / off result, the filtered picture from the first pass is partially restored by the reconstructed picture.

[0157] Fig.12 An exemplary LCU-aligned picture quadtree partitioning according to an embodiment is shown. A top-down partitioning strategy is adopted to divide the picture into multiple levels of quadtree partitions using a rate-distortion criterion. Each partition is called a filter unit. The partitioning process aligns the quadtree partitions with the LCU boundary. The coding order of the FU follows the z-scan order. For example, Fig.12 As shown in , the picture is divided into 10 FUs, and the encoding order is FU0, FU1, FU2, FU3, FU4, FU5, FU6, FU7, FU8 and FU9.

[0158] Fig.13 Shows the corresponding Fig.12 To indicate the picture quadtree partitioning mode, the partitioning flag may be encoded and transmitted in z-order.

[0159] The filter for each FU can be selected from two filter sets based on the rate-distortion criterion. The first set has a 1 / 2 symmetric square filter and a diamond filter newly derived for the current FU. The second set comes from a delay filter buffer that stores filters previously derived for FUs of previous pictures. The filter with the minimum rate-distortion cost of these two sets can be selected for the current FU. Similarly, if the current FU is not the minimum FU and can be further divided into 4 sub-FUs, the rate-distortion cost of the 4 sub-FUs is calculated. By recursively comparing the rate-distortion costs of the segmented and non-segmented cases, the picture quadtree segmentation mode can be determined.

[0160] In some related examples, the maximum quadtree split level is 2, which means that the maximum number of FUs is 16. During the quadtree split decision, the correlation values ​​can be reused, and the correlation values ​​are used to derive the Wiener coefficients of the 16 FUs (the smallest FUs) at the bottom quadtree level. The remaining FUs can derive the Wiener filter from the correlation of the 16 FUs at the bottom quadtree level. Therefore, there is only one frame buffer access for deriving the filter coefficients for all FUs.

[0161] After determining the quadtree partitioning mode, in order to further reduce the filtering distortion, CU synchronous ALF on / off control can be performed. By comparing the filtering distortion and non-filtering distortion, the leaf CU can explicitly turn on / off the ALF in its local area. The coding efficiency can be further improved by redesigning the filter coefficients according to the ALF on / off results. However, the redesign process requires additional frame buffer access. In some related examples, there is no redesign process after the CU synchronous ALF on / off decision to minimize the number of frame buffer accesses.

[0162] III. Cross-Component Adaptive Loop Filter

[0163] In some related examples, a cross-component adaptive loop filter (CC-ALF) is employed. The CC-ALF uses luma sample values ​​to modify each chroma component.

[0164] Fig.14A An exemplary arrangement of a CC-ALF according to an embodiment of the present disclosure is illustrated. Fig. 14B An exemplary linear diamond filter is shown that is applied to the luma channel of each chroma component during CC-ALF operation. The filter coefficients may be transmitted in the APS, for example, by a factor of 2 10Scaling is performed and rounding is performed for fixed point representation. The application of filters is controlled over variable block sizes and is signaled by a context coding flag received for each sample block. Block size and CC-ALF enable flag are received for each chroma component at slice level. In an example, the following block sizes (in chroma samples) are supported: 16×16, 32×32, and 64×64.

[0165] Table 3 shows syntax elements related to CC-ALF. Table 3

[0166] In Table 3, the syntax elements alf_ctb_cross_component_cb_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] equal to 0 indicates that the cross-component Cb filter is not applied to the sample block in the Cb color component at luma position (xCtb, yCtb). alf_ctb_cross_component_cb_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is not equal to 0, indicating that the alf_ctb_cross_component_cb_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] cross-component Cb filters are applied to the block of samples in the Cb color component at luma position (xCtb,yCtb).

[0167] Syntax elements alf_ctb_cross_component_cr_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] equal to 0 indicates that the cross-component Cr filter is not applied to the sample block in the Cr color component at luma position (xCtb, yCtb). alf_ctb_cross_component_cr_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is not equal to 0, indicating that the alf_ctb_cross_component_cr_idc[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] cross-component Cr filters are applied to the block of samples in the Cr color component at luma position (xCtb, yCtb).

[0168] IV. Chroma Sampling Format

[0169] Fig.15 An exemplary relative position of the top left chroma sample is shown when chroma_format_idc is equal to 1 (4:2:0 chroma format) and chroma_sample_loc_type_top_field or chroma_sample_loc_type_bottom_field is equal to the value of the variable ChromaLocType. The region represented by the top left 4:2:0 chroma sample is shown relative to the region represented by the top left luma sample.

[0170] V. Constrained Directional Enhancement Filter

[0171] One goal of the in-loop constrained directional enhancement filter (CDEF) is to filter out coding artifacts while preserving image details. In some related examples such as HEVC, the sample adaptive offset (SAO) algorithm can achieve similar goals by defining signal offsets for different categories of pixels. Unlike SAO, CDEF is a nonlinear spatial filter. The design of this filter is constrained to be easy to vectorize (e.g., it can be implemented using single instruction multiple data (SIMD) operations), which is not the case for other nonlinear filters such as median filters and bilateral filters.

[0172] The CDEF design stems from the following observations. The amount of ringing artifacts in the encoded image tends to be roughly proportional to the quantization step size. The amount of detail is a property of the input image, but the smallest detail retained in the quantized image also tends to be proportional to the quantization step size. For a given quantization step size, the magnitude of the ringing is typically smaller than the magnitude of the detail.

[0173] CDEF works by identifying the orientation of each block and then adaptively filtering along the identified orientation, and to a lesser extent along the orientation rotated 45 degrees from the identified orientation. The filter strength is explicitly signaled, which allows a high degree of control over the blurring. An efficient encoder search is designed for the filter strength. CDEF is based on two previously proposed in-loop filters, and the combined filter is used in the emerging AOMedia Video 1 (AV1) codec.

[0174] Fig.16An exemplary directional search for an 8×8 block in accordance with an embodiment of the present disclosure is shown. The directional search operates on reconstructed pixels just after the deblocking filter. Since these pixels are available to the decoder, no signaling is required for the direction. The search is performed on 8×8 blocks, which are small enough to adequately handle non-straight edges while being large enough to reliably estimate the direction when applied to a quantized image. Having a constant direction over an 8×8 region also makes vectorization of the filter easier. For each block, the direction that best matches the pattern in the corresponding block is determined by minimizing the sum of squared differences (SSD) between the quantized block and the closest fully oriented block. A fully oriented block is a block where all pixels along a line in one direction have the same value.

[0175] One reason to identify a direction is to align the filter taps along that direction to reduce ringing while preserving directional edges or patterns. However, directional filtering alone sometimes does not reduce ringing sufficiently. It is also desirable to use filter taps on pixels that are not along the main direction. To reduce the risk of blurring, these additional taps are treated more carefully. For this reason, CDEF defines primary and secondary taps. The complete 2-D CDEF filter is represented as follows: Where D is the damping parameter, S (p) and S (s) are the strengths of the main tap and the secondary tap, respectively, and round(·) rounds ties away from zero, and and are the filter weights, and f(d, S, D) is a constraint function that operates on the difference between the filtered pixel and each neighboring pixel. For small differences, f(d, S, D) = d, making the filter work like a linear filter. When the difference is large, f(d, S, D) = 0, which effectively ignores the filter taps.

[0176] VI. Loop Restoration in AV1

[0177] In addition to traditional deblocking operations, a set of in-loop recovery schemes can be used in video post-coding deblocking to remove noise and improve edge quality in general. These schemes can be switched within the frame for each appropriately sized tile. The specific scheme described is based on a separable symmetric Wiener filter and a dual self-guided filter with subspace projection. Because content statistics can vary significantly within a frame, these tools are integrated in a switchable framework. Different tools in the switchable framework are triggered in different regions of the frame.

[0178] For the Wiener filter, each pixel in the degraded frame can be reconstructed as a non-causal filtered version of each pixel within a w×w window around each pixel, where w=2r+1 for an odd integer r. If the 2D filter taps are represented by w in column vectorized form 2 × 1 element vector F, then the direct linear minimum mean square error (LMMSE) optimization makes the filter parameters F = H -1 M is given, where H = E[XX T ] is the autocovariance of x (column-vectorized version of w2 samples in a w×w window around the pixel), and M=E[YX T ] is the cross-correlation of x to be estimated with the scalar source sample y. The encoder can estimate H and M from the deblocked frame and the realization in the source, and send the resulting filter F to the decoder. However, this will not only 2 The tapping results in a considerable bit rate cost and also results in non-separable filtering which makes decoding too complex. Therefore, several additional constraints are imposed on the properties of F. First, F is constrained to be separable so that the filtering can be implemented as separable horizontal and vertical w-tap convolutions. Second, each horizontal filter and vertical filter is constrained to be symmetric. Third, it is assumed that the sum of both the horizontal filter coefficients and the vertical filter coefficients is 1.

[0179] For the guided filtering process, the local linear model can be expressed as follows: y = F x + G Equation (17)

[0180] A local linear model is used to compute the filtered output y from the unfiltered sample x, where F and G are determined based on the statistics of the degraded image and the guidance image in the neighborhood of the filtered pixel. If the guidance image is the same as the degraded image, the resulting so-called self-guided filtering has the effect of edge-preserving smoothing. The specific form of self-guided filtering depends on two parameters: the radius r and the noise parameter e, and is listed below.

[0181] (1) Obtain the mean μ and variance σ of the pixels in the (2r+1)×(2r+1) window around each pixel 2 This can be efficiently achieved by box filtering based on integral imaging.

[0182] (2) Calculate for each pixel: f = σ 2 / (σ 2 +e); g = (1-f)μ.

[0183] (3) The F and G of each pixel are calculated as the average of the f and g values ​​in a 3×3 window around the pixel for use.

[0184] The filtering is controlled by r and e, where higher r means higher spatial variation, and higher e means higher range variation.

[0185] Fig.17 An exemplary subspace projection according to an embodiment is shown. Even if none of the cheap restorations X1 and X2 are close to the source Y, appropriate multipliers {α, β} can bring them closer to the source as long as they are slightly moved in the right direction. A cheap restoration refers to a restoration that applies relatively low complexity computations.

[0186] VII. Cross-component sample offset filter

[0187] A cross component sample offset (CCSO) filter is a loop filtering method that reduces distortion of reconstructed samples. In some embodiments, the reconstructed samples may be samples output from an aggregator (455). The reconstructed samples may be input to a loop filter (456). In a CCSO filter, given processed input reconstructed samples of a first color component, an output offset may be derived using a nonlinear mapping, and the output offset may be added to the reconstructed samples of a second color component during filtering by the CCSO filter. The input reconstructed samples of the first color component are located within the filter support region.

[0188] Fig.18 An exemplary filter support region according to an embodiment of the present disclosure is shown. The filter support region includes four reconstruction samples: p0, p1, p2, and p3. The four input reconstruction samples follow a cross shape in the vertical and horizontal directions. The center sample (denoted by c) in the first color component is at the same position as the sample to be filtered in the second color component. When processing the input reconstruction samples, the following steps are applied:

[0189] Step 1: First calculate the incremental values ​​between p0-p3 and c, expressed as m0, m1, m2 and m3.

[0190] Step 2: The incremental values ​​m0-m3 are further quantized. The quantized values ​​are represented as d0, d1, d2, and d3. The quantized values ​​can be -1, 0, and 1 based on the following quantization process: (a) if m<-N, then d=-1; (b) if -N<=m<=N, then d=0; and (c) if m>N, then d=1, where N is called the quantization step size, and example values ​​of N include 4, 8, 12, and 16.

[0191] The quantized values ​​d0-d3 can be used to identify a combination of nonlinear mappings. For example, Fig.18 The CCSO filter in has four filter taps d0-d3, and each filter tap can have one of three quantized values ​​(e.g., -1, 0, and 1), so there can be a total of 3 4 =81 combinations.

[0192] FIG. 19A to FIG. 19B A table is shown according to an embodiment, which lists 81 exemplary combinations of nonlinear mappings in a CCSO filter. The last column of the table represents the output offset value of each combination. The example offset values ​​are integers such as 0, 1, -1, 3, -3, 5, -5, and -7.

[0193] The final filtering process of the CCSO filter can be applied as follows: f′=clip(f+s) Equation (18) where f is the reconstructed sample to be filtered, and s is the FIG. 19A to FIG. 19B The filtered sample values ​​f′ are further clipped to a range associated with the bit depth.

[0194] VIII. Improved Cross-Component Sample Offset Filter

[0195] The present disclosure includes methods of improving the performance of CCSO filters, such as an improved cross-component sample offset method.

[0196] According to aspects of the present disclosure, the nonlinear mapping of the CCSO filter may include certain properties that allow the signaling overhead of indicating the mapping relationship to be compressed. The reduction in the size of the mapping relationship may result in less signaling overhead. Therefore, improved coding efficiency may be achieved.

[0197] In the present disclosure, a CCSO filter may be defined as a filtering process that uses reconstructed samples of a first color component as input (eg, Y, Cb, or Cr) and applies the output to a second color component that is different from the first color component.

[0198] In the CCSO filter, a nonlinear mapping can be derived at the encoder end. The nonlinear mapping describes the relationship between the input reconstructed samples of one color component and the offset to be added to another color component. The domain of the nonlinear mapping can be determined by different combinations of processed input reconstructed samples (such as input reconstructed samples that have been subjected to linear processing).

[0199] According to various aspects of the present disclosure, the nonlinear mapping of the CCSO filter can be compressed to reduce signaling overhead without significantly affecting the performance of the CCSO filter with respect to distortion reduction. Therefore, the overall coding efficiency can be improved.

[0200] In some embodiments, when a CCSO filter is applied, a nonlinear mapping can be used to derive an output offset given a processed input reconstruction sample. The overhead bits for signaling the nonlinear mapping can be reduced. For example, instead of explicitly signaling each entry of the nonlinear mapping, only a subset of the nonlinear mapping can be signaled.

[0201] According to aspects of the present disclosure, the output offset value of input combination A may not be signaled. Instead, the output offset value of input combination A may be derived from another input combination B. This derivation process may be referred to as mirror derivation. An input combination refers to a combination of processed input reconstruction samples as described above (e.g., d0-d3).

[0202] In one embodiment, the output offset value of input combination A can be derived as the opposite number (e.g., a number with the same absolute value and different sign) of the output offset value of input combination B, where A and B have opposite sign values ​​of input combinations d0-d3. For example, if the output offset value of input combination B (d0=a, d1=b, d2=c, d3=d) is s, then the output offset value of input combination A (d0=-a, d1=-b, d2=-c, d3=-d) is -s.

[0203] In one embodiment, the output offset value of input combination A can be derived as the same number as the output offset value of input combination B, where A and B have opposite sign values ​​of the processed input reconstructed samples d0-d3. For example, if the output offset value of input combination B (d0=a, d1=b, d2=c, d3=d) is s, then the output offset value of input combination A (d0=-a, d1=-b, d2=-c, d3=-d) is s.

[0204] In one embodiment, the output offset value may be signaled for input combination B. The signaling may be provided in high-level syntax elements such as APS, slice header, frame header, PPS, SPS, video parameter set (VPS), and the like.

[0205] According to various aspects of the present disclosure, a lookup table may be used to describe the compressed nonlinear mapping. Each row of the lookup table corresponds to an input combination d0-d3 and an associated output offset value. In some embodiments, FIG. 19A to FIG. 19B A portion of the table shown in may be used to describe a compressed nonlinear mapping. In an embodiment, a signal may be used to Fig.19A The output offset values ​​of the first 41 rows of the table shown in , and the output offset values ​​of the remaining 40 rows can be derived based on the signaled output offset values ​​of the first 41 rows. Fig.19CAn example is shown where the output offset value in the Nth row of the remaining 40 rows can be derived as the same number of output offset values ​​in the (80-N)th row signaled in the first 41 rows. Fig.19C As shown, the output offset value in line 41 is Fig.19A The output offset value s39 in line 39 of . Fig.19D Another example is shown, where the output offset value in the Nth row of the remaining 40 rows can be derived as the inverse of the output offset value in the (80-N)th row signaled in the first 41 rows. Fig.19D As shown in , the output offset value in line 41 is -s39, which is Fig.19A The opposite of the output offset value in line 39 of .

[0206] In one embodiment, a parameter indicating enabling mirror derivation may be signaled.Signaling may be provided in high-level syntax elements such as APS, slice header, frame header, PPS, SPS, VPS, etc.

[0207] According to aspects of the present disclosure, only a subset of nonlinear mappings is signaled. For input combinations that are not signaled, the output offset value can be derived as a default value. Examples of default values ​​are integers such as 0, 1, -1, 3, -3, 5, -5, and -7.

[0208] In some embodiments, different subsets may be used, and the subset signaled may be switched for different subsets. For example, the selection of the subset signaled for the nonlinear mapping may be signaled at the block level or in a high-level syntax element such as an APS, slice header, frame header, PPS, SPS, VPS, etc. In one example, support for FIG. 19A to FIG. 19B In another example, support is provided for 16 and 81 combinations of the nonlinear mappings in the table shown in , and the selection is indicated by a signal as a flag. FIG. 19A to FIG. 19B In another example, support is provided for 17 and 81 combinations of the nonlinear mappings in the table shown in , and the selection is indicated by a signal as a flag. FIG. 19A to FIG. 19B In another example, support is provided with 33 and 81 combinations of nonlinear mappings in the table shown in , and the selection is signaled as a flag. FIG. 19A to FIG. 19B In another example, support is provided for 16, 32 and 81 combinations of nonlinear mappings in the table shown in , and the selection is signaled by index. FIG. 19A to FIG. 19B In another example, support is provided for 17, 33 and 81 combinations of nonlinear mappings in the table shown in , and the selection is signaled by the index. FIG. 19A to FIG. 19BFive subsets of 16, 17, 32, 33 and 81 combinations of non-linear mappings in the table shown in , and the selection is signaled by the index.

[0209] Fig.19E An example is shown in which only the signal FIG. 19A to FIG. 19B 17 combinations of the nonlinear mapping in the table shown in , and the output offset values ​​of the remaining combinations can be derived as default values ​​(eg, 0).

[0210] Fig.19F An example is shown in which only the signal FIG. 19A to FIG. 19B An example of 16 combinations of nonlinear mapping in the table shown in , and the output offset values ​​of the remaining combinations can be derived as default values ​​(eg, 0).

[0211] Figure 19G An example is shown in which only the signal FIG. 19A to FIG. 19B 33 combinations of nonlinear mappings in the table shown in , and the output offset values ​​of the remaining combinations can be derived as default values ​​(eg, 0).

[0212] Fig.19H An example is shown in which only the signal FIG. 19A to FIG. 19B There are 32 combinations of nonlinear mappings in the table shown in , and the output offset values ​​of the remaining combinations can be derived as examples of default values ​​(eg, 0).

[0213] According to aspects of the present disclosure, the nonlinear mapping may be divided into a plurality of subsets, such as three subsets A, B, and C, where only subset B is signaled. The output offset values ​​of the input combinations in subset A may be derived from subset B. The output offset values ​​of the input combinations in subset C may be derived as default values. Examples of default values ​​are integers, such as 0, 1, -1, 3, -3, 5, -5, and -7.

[0214] In one embodiment, the output offset value of the input combination A1 in subset A can be derived as the opposite number of the output offset value of the input combination B1 in subset B, where A1 and B1 have opposite sign values ​​of the input combination d0-d3. The output offset value of the input combination in subset C can be derived as a default value (e.g., 0). For example, if the output offset value of the input combination B1 in subset B (d0=a, d1=b, d2=c, d3=d) is s, then the output offset value of the input combination A1 in subset A (d0=-a, d1=-b, d2=-c, d3=-d) is -s.

[0215] In one embodiment, the output offset value of the input combination A1 in subset A can be derived as the same number as the output offset value of the input combination B1 in subset B, where A1 and B1 have opposite sign values ​​of the input combination d0-d3. The output offset value of the input combination in subset C can be derived as a default value (e.g., 0). For example, if the output offset value of the input combination B1 in subset B (d0=a, d1=b, d2=c, d3=d) is s, then the output offset value of the input combination A1 in subset A (d0=-a, d1=-b, d2=-c, d3=-d) is s.

[0216] In one embodiment, a parameter may be signaled indicating that mirrored derivation of a subset of non-linear mappings is enabled.Signaling may be provided in high-level syntax elements such as APS, slice header, frame header, PPS, SPS, VPS, etc.

[0217] According to aspects of the present disclosure, only a limited set of selected output offset values ​​are supported in the non-linear mapping.

[0218] In one embodiment, the supported output offset value ranges may include [-4, +3], [-8, +7], [-16, +15], [-2 K ,2 K ], [K,L], a predefined integer, 0 and an odd integer, and 0 and an even integer, where K and L are integers.

[0219] In one example, a set of supported output offset values ​​may include 0 and a set of odd integers with different sign values, such as 0, 1, -1, 3, -3, 5, -5, and -7. In another example, a set of supported output offset values ​​may include 0 and a set of even integers with different sign values, such as 0, 2, -2, 4, -4, 6, -6, and -8.

[0220] In one embodiment, a set of supported output offset values ​​may be signaled.Signaling may be provided in high-level syntax elements such as APS, slice header, frame header, PPS, SPS, VPS, etc.

[0221] In one embodiment, an array of offset values ​​may be supported in non-linear mapping and the index may be signaled. Signaling may be provided in high-level syntax elements (such as APS, slice header, frame header, PPS, SPS, VPS, etc.) to indicate the output offset value selected for the input combination in the array.

[0222] In one embodiment, different input combinations may have different sets of supported output offset values.

[0223] In one embodiment, the set of supported offset values ​​may depend on the quantization parameter.

[0224] In one embodiment, fixed length encoding may be used to signal the output offset value or the index of the output offset value.

[0225] According to aspects of the present disclosure, an output offset value of an input combination applied to a current coding block in a current slice of a current picture may be predicted from output offset values ​​applied to a different picture, a different slice, or a different coding block.

[0226] In one embodiment, instead of signaling an output offset value, a delta value between the output offset value and a predicted output offset value is signaled.

[0227] In one embodiment, the output offset value of at least one input combination is not signaled and may be derived from a predicted output offset value.

[0228] In one embodiment, whether the output offset value is predicted is signaled by a flag.The flag may be provided in a high-level syntax element such as APS, slice header, frame header, PPS, SPS, VPS, etc.

[0229] The prediction of the output offset value may depend on coded information including but not limited to frame type, temporal layer, and quantization parameter.

[0230] In some related examples, one or more filtering processes may be applied to the reconstructed samples of the coded blocks. For example, a deblocking module may be applied to the reconstructed samples of the coded blocks. Then, a CDEF module may be applied to the filtered reconstructed samples output from the deblocking module, and a loop recovery filter module may be applied to the filtered reconstructed samples output from the CDEF module.

[0231] According to various aspects of the present disclosure, when a CCSO filter is applied to a reconstructed sample of a coded block, the input position and output position of the CCSO filter are flexible. The input position of the CCSO filter is the position where the input reconstructed sample of the CCSO filter is selected. The output position of the CCSO filter is the position where the output offset value of the CCSO filter is applied (e.g., CCSO filtering is applied).

[0232] In some embodiments, the input and output can share the same position. That is, there is no other coding module between the input position and the output position of the CCSO filter. In one example, the input position and the output position can be just before the deblocking module. In another example, the input position and the output position can be after the deblocking module and before the CDEF module. In another example, the input position and the output position can be after the CDEF module and before the loop recovery filter (LR) module. In another example, the input position and the output position can be after the LR module.

[0233] In some embodiments, the input position and the output position may be different, and the input position is before the output position. That is, at least one encoding module is placed between the input position and the output position of the CCSO filter. In one example, the input position may be just before the deblocking module, and the output position may be after the deblocking module and before the CDEF module. In another example, the input position may be after the deblocking module and before the CDEF module, and the output position may be after the CDEF module and before the LR module. In another example, the input position may be after the CDEF module and before the LR module, and the output position may be after the LR module.

[0234] In one embodiment, the CDEF module and the LR module in the above embodiment can be replaced by the SAO module and the ALF module respectively. The same method in the above embodiment can be applied to this embodiment.

[0235] IX. Flowchart

[0236] Fig. 20 A flowchart outlining an exemplary method (2000) according to an embodiment of the present disclosure is shown. In various embodiments, the method (2000) is performed by a processing circuit, such as a processing circuit in a terminal device (210), (220), (230) and (240), a processing circuit that performs the functions of a video encoder (303), a processing circuit that performs the functions of a video decoder (310), a processing circuit that performs the functions of a video decoder (410), a processing circuit that performs the functions of an intra-picture prediction unit (452), a processing circuit that performs the functions of a video encoder (503), a processing circuit that performs the functions of a predictor (535), a processing circuit that performs the functions of an intra-frame encoder (622), a processing circuit that performs the functions of an intra-frame decoder (772), and the like. In some embodiments, the method (2000) is implemented using software instructions, so when the processing circuit executes the software instructions, the processing circuit performs the method (2000).

[0237] The method (2000) may generally begin at step (S2010), in which the method (2000) decodes prediction information for a current block in a current picture, the current picture being part of an encoded video sequence. The prediction information is used to indicate a plurality of combinations of processed reconstructed samples. A filtering process may be used to reduce compression artifacts and distortion of the reconstructed samples. The filtering process may use the processed reconstructed samples of a first color component as input (e.g., Y, Cb, or Cr), and apply the output to a second color component different from the first color component. In some embodiments, the filtering process may be performed in a loop filter unit (456). Examples of filter processes include, but are not limited to, CCSO and CC-ALF. The method (2000) then proceeds to step (S2020).

[0238] At step (S2020), the method (2000) performs a filtering process on the processed reconstructed sample combination of the first color component of the current block. The processed reconstructed sample combination of the first color is not included in the multiple combinations. Then, the method (2000) proceeds to step (S2030).

[0239] At step (S2030), the method (2000) determines an output value of the filtering process based on one of: a default value, a predicted output value, and an output value indicated in the prediction information. Here, the output value is, for example, the output offset value mentioned above. Then, the process (2000) proceeds to step (S2040).

[0240] At step (S2040), the method (2000) reconstructs the current block based on the output values ​​of the filtering process being applied to the reconstructed samples of the second color component of the current block. The second color component is different from the first color component. Then, the method (2000) ends.

[0241] In one embodiment, the method (2000) determines one of a first value and a second value as the output value of the filtering process, the first value being one of the output values ​​indicated in the prediction information, and the second value being the opposite of the first value.

[0242] In one embodiment, each processed reconstructed sample in the combination of processed reconstructed samples of the first color component is the inverse of a corresponding processed reconstructed sample in one of the plurality of combinations, and one of the output values ​​corresponds to the one of the plurality of combinations.

[0243] In one embodiment, each processed reconstructed sample in the combination of processed reconstructed samples of the first color component is the inverse of a corresponding processed reconstructed sample in one of the plurality of combinations, and one of the output values ​​corresponds to the one of the plurality of combinations.

[0244] In one embodiment, the method (2000) determines the default value as the output value of the filtering process based on the prediction information indicating that the plurality of combinations are a subset of a total number of combinations of processed reconstructed samples in the filtering process.

[0245] In one embodiment, the predicted output value is determined by an output value of a filtering process applied to another coding block based on an output value of the filtering process.

[0246] In one embodiment, the processed reconstructed sample combination of the first color component is determined based on the reconstructed sample of the first color component output from the first encoding module, and the reconstructed sample of the second color component is output from the first encoding module or from a second encoding module applied after the first encoding module. In one embodiment, the processed reconstructed sample combination of the first color component of the current block is a combination of quantized values ​​d0, d1, d2 and d3 in the filter support area. The filter support area includes a central reconstructed sample c, and four surrounding reconstructed samples p0, p1, p2 and p3 around the central reconstructed sample c; the quantized values ​​d0, d1, d2 and d3 are quantized values ​​of the incremental values ​​m0, m1, m2 and m3 between the surrounding reconstructed samples p0-p3 and the central reconstructed sample c. In one embodiment, the multiple combinations indicated by the prediction information are a subset of a nonlinear mapping notified by a signal or a selection of the subset. The nonlinear mapping is used to represent the mapping relationship between the processed reconstructed sample combination of the first color component of the current block and the output value of the filtering process.

[0247] X. Computer System

[0248] The above techniques may be implemented as computer software via computer-readable instructions and physically stored in one or more computer-readable media. Fig.21 A computer system (2100) is shown that is suitable for implementing certain embodiments of the disclosed subject matter.

[0249] The computer software may be encoded in any suitable machine code or computer language, and may be assembled, compiled, linked, or the like to create a code comprising instructions, which may be directly executed by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc., or executed by decoding, microcode, or the like.

[0250] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablets, servers, smartphones, gaming devices, IoT devices, etc.

[0251] Fig.21 The components shown for the computer system (2100) are exemplary in nature and are not intended to impose any limitations on the scope of use or functionality of the computer software implementing the embodiments of the present application. Nor should the configuration of the components be interpreted as having any dependency or requirement on any component or combination of components shown in the exemplary embodiment of the computer system (2100).

[0252] The computer system (2100) may include certain human-computer interface input devices. Such human-computer interface input devices may respond to input from one or more human users through tactile input (e.g., keyboard input, sliding, data glove movement), audio input (e.g., sound, applause), visual input (e.g., gestures), and olfactory input (not shown). The human-computer interface devices may also be used to capture certain media that are not necessarily directly related to human conscious input, such as audio (e.g., speech, music, ambient sound), images (e.g., scanned images, photographic images obtained from a still image camera), and videos (e.g., two-dimensional video, three-dimensional video including stereoscopic video).

[0253] The human-computer interface input device may include one or more of the following (only one of which is drawn): keyboard (2101), mouse (2102), touchpad (2103), touch screen (2110), data gloves (not shown), joystick (2105), microphone (2106), scanner (2107), camera (2108).

[0254] The computer system (2100) may also include certain human-computer interface output devices. Such human-computer interface output devices may stimulate the senses of one or more human users through, for example, tactile output, sound, light, and smell / taste. Such human-computer interface output devices may include tactile output devices (e.g., tactile feedback through a touch screen (2110), a data glove (not shown), or a joystick (2105), but there may also be tactile feedback devices that are not used as input devices), audio output devices (e.g., speakers (2109), headphones (not shown)), visual output devices (e.g., screens (2110) including cathode ray tube screens, liquid crystal screens, plasma screens, organic light emitting diode screens, each of which has or does not have a touch screen input function, each of which has or does not have a tactile feedback function - some of which can output two-dimensional visual output or output of more than three dimensions by means such as stereoscopic picture output; virtual reality glasses (not shown), holographic displays, and smoke boxes (not shown)) and printers (not shown). These visual output devices (e.g., screens (2110)) may be connected to the system bus (2148) via a graphics adapter (2150).

[0255] The computer system (2100) may also include human-accessible storage devices and their associated media, such as optical media including high-density read-only / rewritable optical disks (CD / DVD ROM / RW) (2120) with CD / DVD or similar media (2121), thumb drives (2122), removable hard disk drives or solid state drives (2123), traditional magnetic media such as tapes and floppy disks (not shown), special-purpose ROM / ASIC / PLD-based devices such as security software protectors (not shown), and the like.

[0256] Those skilled in the art should also understand that the term "computer-readable media" used in connection with the disclosed subject matter does not include transmission media, carrier waves, or other transient signals.

[0257] The computer system (2100) may also include a network interface (2154) leading to one or more communication networks (2155). The one or more communication networks (2155) may be wireless, wired, or optical. The one or more communication networks (2155) may also be local area networks, wide area networks, metropolitan area networks, vehicle-mounted networks, and industrial networks, real-time networks, delay-tolerant networks, and the like. Examples of the one or more communication networks (2155) include local area networks such as Ethernet, wireless local area networks, cellular networks (GSM, 3G, 4G, 5G, LTE, etc.), television wired or wireless wide area digital networks (including cable television, satellite television, and terrestrial broadcast television), vehicle-mounted and industrial networks (including CANBus), and the like. Some networks typically require an external network interface adapter for connecting to some universal data ports or peripheral buses (2149) (e.g., a USB port of the computer system (2100)); other systems are typically integrated into the core of the computer system (2100) by connecting to a system bus as described below (e.g., an Ethernet interface integrated into a PC computer system or a cellular network interface integrated into a smart phone computer system). By using any of these networks, the computer system (2100) can communicate with other entities. The communication can be one-way, for reception only (e.g., wireless television), one-way for transmission only (e.g., CAN bus to certain CAN bus devices), or two-way, such as to other computer systems via local or wide area digital networks. Each of the above networks and network interfaces can use certain protocols and protocol stacks.

[0258] The above-mentioned human-machine interface devices, human-accessible storage devices, and network interfaces may be connected to the core (2140) of the computer system (2100).

[0259] The core (2140) may include one or more central processing units (CPUs) (2141), graphics processing units (GPUs) (2142), dedicated programmable processing units in the form of field programmable gate arrays (FPGAs) (2143), hardware accelerators for specific tasks (2144), etc. These devices, as well as read-only memory (ROM) (2145), random access memory (2146), internal mass storage (e.g., internal non-user accessible hard disk drives, solid-state drives, etc.) (2147), etc., may be connected via a system bus (2148). In some computer systems, the system bus (2148) may be accessed in the form of one or more physical plugs so that it may be expanded by additional central processing units, graphics processing units, etc. Peripheral devices may be directly attached to the core's system bus (2148), or connected via a peripheral bus (2149). In one example, a screen (2110) may be connected to a graphics adapter (2150). The architecture of the peripheral bus includes a peripheral controller interface PCI, a universal serial bus USB, etc.

[0260] The CPU (2141), GPU (2142), FPGA (2143) and accelerator (2144) can execute certain instructions, which can be combined to form the above-mentioned computer code. The computer code can be stored in ROM (2145) or RAM (2146). Transition data can also be stored in RAM (2146), while permanent data can be stored in, for example, internal mass storage (2147). Fast storage and retrieval of any memory device can be achieved by using a cache memory, which can be closely associated with one or more CPUs (2141), GPUs (2142), mass storage (2147), ROMs (2145), RAMs (2146), etc.

[0261] The computer readable medium may have computer code thereon for performing various computer-implemented operations. The medium and computer code may be specially designed and constructed for the purpose of this application, or may be medium and code well known and available to those skilled in the art of computer software.

[0262] As an example and not a limitation, a computer system having an architecture (2100), in particular a core (2140), can be provided as a processor (including a CPU, a GPU, an FPGA, an accelerator, etc.) to execute software contained in one or more tangible computer-readable media. Such a computer-readable medium can be a medium associated with the above-mentioned user-accessible mass storage, as well as a specific memory of the core (2140) having non-volatility, such as a core internal mass storage (2147) or a ROM (2145). Software implementing various embodiments of the present application can be stored in such a device and executed by the core (2140). Depending on specific needs, the computer-readable medium may include one or more storage devices or chips. The software can enable the core (2140), in particular the processor therein (including a CPU, a GPU, an FPGA, etc.) to perform a specific process or a specific part of a specific process described herein, including defining a data structure stored in the RAM (2146) and modifying such a data structure according to a software-defined process. Additionally or alternatively, the computer system may provide functionality hardwired in logic or otherwise contained in circuitry (e.g., accelerator (2144)) that may operate in place of or in conjunction with software to perform a particular process or a particular portion of a particular process described herein. Where appropriate, references to software may include logic and vice versa. Where appropriate, references to computer-readable media may include circuitry (e.g., an integrated circuit (IC)) storing the executing software, circuitry containing the executing logic, or both. The present application includes any suitable combination of hardware and software.

[0263] Although the present application has described a number of exemplary embodiments, various changes, arrangements and various equivalent substitutions of the embodiments are within the scope of the present application. Therefore, it should be understood that those skilled in the art can design a variety of systems and methods, which, although not explicitly shown or described herein, embody the principles of the present application and are therefore within the spirit and scope of the present application. Appendix A: Acronyms ALF: Adaptive Loop Filter AMVP: Advanced Motion Vector Prediction APS: Adaptation Parameter Set ASIC: Application-Specific Integrated Circuit ATMVP: Alternative / Advanced Temporal Motion Vector Prediction AV1: Alliance for Open Media Video 1 (AOMedia Video 1) AV2: Alliance for Open Media Video 2 (AOMedia Video 2) BMS: Benchmark set BV: Block Vector CANBus: Controller Area Network Bus CB: Coding Block CC-ALF: Cross-Component Adaptive Loop Filter CD: Compact Disc CDEF: Constrained Directional Enhancement Filter CPR: Current Picture Referencing CPU: Central Processing Unit CRT: Cathode Ray Tube CTB: Coding Tree Block CTU: Coding Tree Unit CU: Coding Unit DPB: Decoder Picture Buffer DPCM: Differential Pulse Code Modulation DPS: Decoding Parameter Set DVD: Digital Video Disc FPGA: Field Programmable Gate Area JCCR: Joint CbCr Residual Coding JVET: Joint Video Exploration Team GOP: Group of Pictures GPU: Graphics Processing Unit GSM: Global System for Mobile communications HDR: High Dynamic Range HEVC: High Efficiency Video Coding HRD: Hypothetical Reference Decoder IBC: Intra Block Copy IC:Integrated Circuit ISP: Intra Sub-Partitions JEM: Joint Exploration Model LAN: Local Area Network LCD: Liquid-Crystal Display LR: Loop Restoration Filter LRU: Loop Restoration Unit LTE: Long-Term Evolution MPM: Most Probable Mode MV: Motion Vector OLED: Organic Light-Emitting Diode PBs: Prediction Blocks PCI: Peripheral Component Interconnect PDPC: Position Dependent Prediction Combination PLD: Programmable Logic Device PPS: Picture Parameter Set PU: Prediction Unit RAM: Random Access Memory ROM: Read-Only Memory SAO: Sample Adaptive Offset SCC: Screen Content Coding SDR: Standard Dynamic Range SEI: Supplementary Enhancement Information SNR: Signal Noise Ratio SPS: Sequence Parameter Set SSD: Solid-state Drive TU: Transform Unit USB: Universal Serial Bus VPS: Video Parameter Set VUI: Video Usability Information VVC: Versatile Video Coding WAIP: Wide-Angle Intra Prediction

Claims

1. A video decoding method, characterized in that: include: Decoding prediction information for a current block in a current picture of a coded video sequence, the prediction information being used to indicate a subset of a plurality of combinations of processed reconstructed samples of a first color component of the coded block and corresponding offset values ​​for a filtering process applied to a second color component of the coded block; determining, based on a combination of processed reconstructed samples of a first color component of the current block, an offset value for a filtering process applied to reconstructed samples of a second color component of the coding block; as well as reconstructing the current block based on the determined offset value of the filtering process applied to the reconstructed samples of a second color component of the coding block, the second color component being different from the first color component; wherein, when the one combination of processed reconstructed samples of the first color component of the current block is a first combination in a subset of multiple combinations of processed reconstructed samples, the determined offset value is an offset value corresponding to the first combination of processed reconstructed samples indicated by the prediction information; as well as When the one combination of processed reconstructed samples of the first color component of the current block is different from each of a subset of multiple combinations of the processed reconstructed samples, the determined offset value is derived from an offset value of the filtering process corresponding to a second combination in the subset of multiple combinations of the processed reconstructed samples.

2. The method according to claim 1, wherein: The one combination of processed reconstructed samples of the first color component of the current block is different from each of a subset of a plurality of combinations of processed reconstructed samples, and the determined offset value is not indicated by the prediction information.

3. The method according to claim 1, wherein: The one combination of processed reconstructed samples of the first color component of the current block is different from each of a subset of multiple combinations of processed reconstructed samples, and the determined offset value is based on a predicted offset value of the filtering process applied to another coding block.

4. The method according to claim 1, wherein: The one combination of processed reconstructed samples of the first color component of the current block is different from each of a subset of multiple combinations of the processed reconstructed samples, and the determined offset value is derived from an offset value of the filtering process corresponding to a second combination in the subset of multiple combinations of the processed reconstructed samples indicated in the prediction information.

5. The method according to claim 4, wherein: The determined offset value of the filtering process is equal to the offset value of the filtering process corresponding to a second combination in the subset of the plurality of combinations of the processed reconstructed samples.

6. The method according to claim 1, wherein: The determined offset value of the filtering process is the inverse of the offset value of the filtering process corresponding to a second combination in the subset of the plurality of combinations of processed reconstructed samples.

7. The method according to claim 1, wherein: The one combination of processed reconstructed samples of the first color component of the current block is different from each of a subset of multiple combinations of the processed reconstructed samples, and the determined offset value of the filtering process is based on: (i) a filtering process offset value corresponding to a second combination of processed reconstructed samples indicated in the prediction information, and (ii) a syntax element indicating whether the offset value of the determined filter process and the offset value of the filtering process corresponding to the second combination of processed reconstructed samples have the same sign.

8. The method according to claim 1, wherein: The prediction information comprises a syntax element indicating which subset of a plurality of subsets of processed reconstructed samples is indicated by the prediction information.

9. A video encoding method, characterized in that: include: determining, based on a combination of processed reconstructed samples of a first color component of a current block, an offset value for a filtering process applied to reconstructed samples of a second color component of the current block; encoding the current block in a codestream based on the determined offset value applied to the reconstructed samples of a second color component of the current block, the second color component being different from the first color component; as well as encoding prediction information in the bitstream, the prediction information being used to indicate a subset of a plurality of combinations of processed reconstructed samples of a first color component of a coding block and corresponding offset values ​​for a filtering process applied to a second color component of the coding block; in, wherein, when the one combination of processed reconstructed samples of the first color component of the current block is a first combination in a subset of multiple combinations of processed reconstructed samples, the determined offset value is an offset value corresponding to the first combination of processed reconstructed samples indicated by the prediction information; as well as When the one combination of processed reconstructed samples of the first color component of the current block is different from each of a subset of multiple combinations of the processed reconstructed samples, the determined offset value is derived from an offset value of the filtering process corresponding to a second combination in the subset of multiple combinations of the processed reconstructed samples.

10. A video decoding device, characterized in that: The method comprises a processing circuit configured to perform the method according to any one of claims 1 to 8.

11. A video encoding device, characterized in that: The method comprises a processing circuit configured to perform the method according to claim 9.

12. A non-volatile computer-readable storage medium storing instructions, characterized in that: When the instructions are executed by at least one processor, the at least one processor is caused to execute: executing the method according to any one of claims 1 to 9.

13. A method for processing a video code stream, characterized in that: The video code stream is generated according to the encoding method according to claim 9, or is decoded based on the decoding method according to any one of claims 1 to 8.

Images