Multiple source based extended taps for adaptive loop filters in video coding

Abstract

A mechanism for processing video data is disclosed. The mechanism includes applying an adaptive loop filter (ALF) to a first component of a video unit. The ALF includes one or more extension taps. The one or more extended taps utilize input sources other than the spatial domain adjacent sample points of the first component. A conversion between the visual media data and the bitstream is performed based on the ALF.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of International Patent Application No. PCT / CN2022 / 103891, filed on July 5, 2022. All of the above patent applications are incorporated herein by reference in their entirety. Technical Field

[0003] This patent document relates to the generation, storage and use of digital audio and video media information in file format. Background Art

[0004] Digital video accounts for the largest share of bandwidth used on the Internet and other digital communications networks. As the number of connected user devices capable of receiving and displaying video increases, the bandwidth requirements for digital video usage are likely to continue to grow. Summary of the invention

[0005] A first aspect relates to a method for processing video data, comprising: determining to apply an adaptive loop filter (ALF) to a first component of a video unit, the ALF comprising one or more extension taps, wherein the one or more extension taps use an input source other than spatially adjacent samples of the first component; and performing conversion between visual media data and a bitstream based on the ALF.

[0006] A second aspect relates to a device for processing video data, comprising: a processor; and a non-transitory memory, wherein instructions are stored in the memory, and when the instructions are executed by the processor, the processor executes the method described in the above aspects.

[0007] A third aspect relates to a non-transitory computer-readable medium, including a computer program product for use with a video codec device, the computer program product including computer executable instructions stored on the non-transitory computer-readable medium, which, when executed by a processor, causes the video codec device to perform the method of any of the aforementioned aspects.

[0008] A fourth aspect relates to a non-transitory computer-readable recording medium storing a bitstream of a video generated by a method performed by a video processing device, wherein the method includes: determining to apply an adaptive loop filter (ALF) to a first component of a video unit, the ALF including one or more extension taps, wherein the one or more extension taps use an input source other than spatially adjacent samples of the first component; and generating the bitstream based on the determination.

[0009] A fifth aspect relates to a method for storing a bitstream of a video, comprising: determining to apply an adaptive loop filter (ALF) to a first component of a video unit, the ALF comprising one or more extension taps, wherein the one or more extension taps use an input source other than spatially adjacent samples of the first component; generating a bitstream based on the determination; and storing the bitstream in a non-transitory computer-readable recording medium.

[0010] For clarity, any of the foregoing embodiments may be combined with one or more of the other foregoing embodiments to create new embodiments within the scope of the present disclosure.

[0011] These and other features will become more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] For a more complete understanding of the present disclosure, reference is now made to the following brief description taken in conjunction with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

[0013] Figure 1 An example of nominal vertical and horizontal positions of 4:2:2 luma and chroma samples in a picture is shown.

[0014] Figure 2 An example encoder block diagram is shown.

[0015] Figure 3 An example picture segmented into raster scan strips is shown.

[0016] Figure 4 An example picture segmented into rectangular scan strips is shown.

[0017] Figure 5 An example picture divided into bricks is shown.

[0018] FIG. 6A to FIG. 6C An example of a codec tree block (CTB) crossing a picture boundary is shown.

[0019] Figure 7 An example of an intra prediction mode is shown.

[0020] Figure 8 Examples of block boundaries in a picture are shown.

[0021] Fig. 9 An example of pixels involved in filter usage is shown.

[0022] Fig.10 An example of a filter shape of an adaptive loop filter (ALF) is shown.

[0023] Fig.11 An example of transform coefficients supported by a 5×5 diamond filter is shown.

[0024] Fig.12 An example of relative coordinates supported by a 5×5 diamond filter is shown.

[0025] Fig.13 An example shape of at least one spatial tap is shown.

[0026] Fig.14 An example shape of at least one spatial tap is shown.

[0027] Fig.15 An example shape of at least one extension tap is shown.

[0028] Fig.16 An example shape of at least one extension tap is shown.

[0029] Fig.17 An example shape of at least one extension tap is shown.

[0030] Fig.18 An example shape of at least one extension tap is shown.

[0031] Fig.19 An example shape of at least one extension tap is shown.

[0032] Figures 20 to 46 Examples of shapes of one or more extension taps are shown.

[0033] Fig.47 is a block diagram illustrating an example video processing system.

[0034] Fig.48 is a block diagram of an example video processing device.

[0035] Fig.49 is a flow chart of an example method for video processing.

[0036] Fig.50 is a block diagram illustrating an example video codec system.

[0037] Fig.51 is a block diagram illustrating an example encoder.

[0038] Fig.52 is a block diagram illustrating an example decoder.

[0039] Fig.53 is a flow chart of an example method for video processing. DETAILED DESCRIPTION

[0040] First, it should be understood that although illustrative implementations of one or more embodiments are provided below, the disclosed systems and / or methods may be used with any number of technical facts, whether currently known or yet to be developed. The present disclosure should not be limited in any way to the exemplary implementations, drawings, and techniques shown below, including the exemplary designs and implementations shown and described herein, but may be modified within the full scope of the appended claims and their equivalents.

[0041] The section titles used in this document are for ease of understanding and do not limit the applicability of the techniques and embodiments disclosed in each section to only that section. In addition, the techniques described herein are applicable to other video codec protocols and designs.

[0042] 1. Preliminary Discussion

[0043] This article relates to video codec technology. In particular, it relates to loop filters and other coding tools in image / video codecs. These ideas can be applied to video codecs, such as High Efficiency Video Codec (HEVC), Versatile Video Codec (VVC), or other video codec technologies, alone or in various combinations.

[0044] 2. Abbreviations

[0045] This disclosure includes the following abbreviations. Advanced Video Codec (Rec.ITU-T H.264|ISO / IEC 14496-10) (AVC), Codec Picture Buffer (CPB), Clean Random Access (CRA), Codec Tree Unit (CTU), Codec Video Sequence (CVS), Decode Picture Buffer (DPB), Decoding Parameter Set (DPS), Generic Constraint Information (GCI), High Efficiency Video Codec (also known as Rec.ITU-T H.265|ISO / IEC 23008-2, (HEVC)), Joint Exploration Model (JEM), Motion Constrained Slice Set (MCTS), Network Abstraction Layer (NAL), Output Layer Set (OLS), Picture Header (PH), Picture Parameter Set (PPS), Profile, Tier and Level (PTL), Picture Unit (PU), Reference Picture Resampled (RPR), Raw Byte Sequence Payload (RBSP), Supplemental Enhancement Information (SEI), Slice Header (SH), Sequence Parameter Set (SPS), Video Codec Layer (VCL), Video Parameter Set (VPS), Versatile Video Codec (also known as Rec.ITU-T H.266|ISO / IEC 23090-3) (VVC), VVC Test Model (VTM), Video Usability Information (VUI), Transform Unit (TU), Codec Unit (CU), Deblocking Filter (DF), Sample Adaptive Offset (SAO), Adaptive Loop Filter (ALF), Codec Block Flag (CBF), Quantization Parameter (QP), Rate-Distortion Optimization (RDO) and Bilateral Filter (BF).

[0046] 3. Video Codec Standards

[0047] Video codec standards have evolved primarily through the development of standards by the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) and the International Organization for Standardization (ISO) / International Electrotechnical Commission (IEC). ITU-T developed H.261 and H.263, ISO / IEC developed the Moving Picture Experts Group (MPEG-1) and MPEG-4 Vision, and the two organizations jointly developed the H.262 / MPEG-2 Video and H.264 / MPEG-4 Advanced Video Codec (AVC) and H.265 / HEVC[1] standards. Since H.262, video codec standards have been based on a hybrid video codec structure that utilizes temporal prediction plus transform coding. To explore future video codec technologies beyond HEVC, the Video Codec Experts Group (VCEG) and MPEG jointly established the Joint Video Exploration Team (JVET). JVET adopted many of the approaches and put them into a reference software called the Joint Exploration Model (JEM)[2]. When the Versatile Video Codec (VVC) project was officially launched, JVET was renamed the Joint Video Experts Team (JVET). VVC is a codec standard that aims to reduce the bit rate by 50% compared to HEVC. The VVC working draft and VVC test model (VTM) are continuously updated.

[0048] The Video Coding Experts Group (VCEG) of the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) and the Joint Technical Committee (JTC) 1 / Subcommittee (SC) 29 / Working Group (WG) 11 of the International Organization for Standardization and the International Electrotechnical Commission (ISO / IEC) Moving Picture Experts Group (MPEG) are studying the potential need for standardization of future video codec technologies with compression capabilities significantly exceeding the current VVC standard. This future standardization action could take the form of an extension of VVC or an entirely new standard. These groups work together on this development activity in a joint collaborative effort known as the Joint Video Development Team (JVET) to evaluate the compression technology designs proposed by their experts in the field. The first Exploration Experiment (EE) was established by JVET and uses reference software called the Enhanced Compression Model (ECM). The test model ECM is continuously updated.

[0049] 3.1 Color Space and Chroma Subsampling

[0050] A color space (also called a color model (or color system)) is a mathematical model that describes the range of colors as a tuple of numbers, such as 3 or 4 values ​​or color components (e.g., RGB). In general, a color space is a detailed description of coordinate systems and subspaces. For video compression, the most commonly used color spaces are Luma, Blue-Difference Chroma, and Red-Difference Chroma (YCbCr) and Red, Green, Blue (RGB).

[0051] YCbCr, Y'CbCr or YPb / CbPr / Cr (also written as YCBCR or Y'CBCR) is a series of color spaces used as part of the color image pipeline in video and digital photography systems. Y' is the luminance component, and CB and CR are the blue difference chrominance component and the red difference chrominance component. Y' (with a prime) is different from Y (luminance), which means that the light intensity is non-linearly encoded based on the gamma-corrected RGB primaries.

[0052] Chroma subsampling is the practice of encoding an image at a lower resolution for chroma information than for luminance information by exploiting the fact that the human visual system is less sensitive to color differences than to luminance. 3.1.1 4:4:4

[0054] In 4:4:4, each of the three Y'CbCr components has the same sampling rate. Therefore there is no chroma subsampling. This scheme is sometimes used in high-end film scanners and film post-production. 3.1.2 4:2:2

[0056] In 4:2:2, the two chroma components are sampled at half the sampling rate of luma. The horizontal chroma resolution is halved, while the vertical chroma resolution is unchanged. This reduces the bandwidth of the uncompressed video signal by one third, but there is little visual difference. Figure 1 Examples of nominal vertical and horizontal positions for a 4:2:2 color format are shown. 3.1.3 4:2:0

[0058] In the 4:2:0 format, the horizontal sampling is doubled compared to 4:1:1, but in this scheme the vertical resolution is halved since the Cb and Cr channels are sampled only on every alternate line. Therefore, the data rate is the same. Cb and Cr are each subsampled with a sampling factor equal to 2 in both horizontal and vertical directions. There are three variants of the 4:2:0 scheme, each with different horizontal and vertical addressing.

[0059] In MPEG-2, Cb and Cr are co-located horizontally. Cb and Cr are located between pixels (i.e., in the gaps) vertically. In Joint Photographic Experts Group (JPEG) / JPEG File Interchange Format (JFIF), H.261, and MPEG-1, Cb and Cr are located in the gaps between alternate luminance samples. In 4:2:0DV, Cb and Cr are co-located horizontally. Vertically, they are located on alternate lines.

[0060]

[0061] Table 1. SubWidthC and SubHeightC values ​​derived from chroma_format_idc and Separate_colour_plane_flag

[0062] 3.2 Example encoding process of video codec

[0063] Figure 2 An example encoder block diagram of VVC is shown, which contains three loop filter blocks: deblocking filter (DF), sample adaptive offset (SAO) and ALF. Unlike DF, which uses a predefined filter, SAO and ALF use the original samples of the current picture to reduce the mean square error between the original samples and the reconstructed samples by adding an offset and applying a finite impulse response (FIR) filter, respectively, using the codec's side information to signal the offset and filter coefficients. ALF is located at the last processing stage of each picture and can be seen as a tool that attempts to capture and repair artifacts produced by previous stages.

[0064] 3.3 Definition of Video / Codec Unit

[0065] A picture is divided into one or more slice rows and one or more slice columns. A slice is a sequence of CTUs covering a rectangular area of ​​a picture. A slice can be divided into one or more bricks, each of which contains multiple CTU rows. A slice that is not divided into multiple bricks can also be called a brick. However, a brick that is a proper subset of a slice cannot be called a slice. A strip contains several slices of a picture or several bricks of a slice.

[0066] Two strip modes are supported, namely, raster scan strip mode and rectangular strip mode. In raster scan strip mode, a strip contains a series of slices in the slice raster scan of the picture. In rectangular strip mode, a strip contains multiple bricks of the picture, which together form a rectangular area of ​​the picture. The bricks within a rectangular strip are arranged in the order of the brick raster scan of the strip. Figure 3 An example picture partitioned into raster scan strips is shown. Raster scan strip partitioning is employed, where a picture with 18 by 12 luma CTUs is divided into 12 slices and 3 raster scan strips.

[0067] Figure 4 An example image is shown that is segmented into rectangular scan strips. Figure 4 In , a picture with 18 by 12 luma CTUs is partitioned into 24 slices (6 slice columns and 4 slice rows) and 9 rectangular strips.

[0068] Figure 5An example image partitioned into tiles is shown, where the image is divided into 4 slices (2 slice columns and 2 slice rows), 11 bricks (the upper left slice contains 1 brick, the upper right slice contains 5 bricks, the lower left slice contains 2 bricks, and the lower right slice contains 3 bricks), and 4 rectangular strips.

[0069] 3.3.1 CTU / CTB size

[0070] In VVC, the CTU size (signaled in the sequence parameter set (SPS) through the syntax element log2_ctu_size_minus2) can be as small as 4×4.

[0071] 7.3.2.3 Sequence parameter set RBSP syntax

[0072]

[0073]

[0074]

[0075] log2_ctu_size_minus2 plus 2 specifies the luma coding tree block size for each CTU. log2_min_luma_coding_block_size_minus2 plus 2 specifies the minimum luma coding block size. The variables CtbLog2SizeY, CtbSizeY, MinCbLog2SizeY, MinCbSizeY, MinTbLog2SizeY, MaxTbLog2SizeY, MinTbSizeY, MaxTbSizeY, PicWidthInCtbsY, PicHeightInCtbsY, PicSizeInCtbsY, PicWidthInMinCbsY, PicHeightInMinCbsY, PicSizeInMinCbsY, PicSizeInSamplesY, PicWidthInSamplesC, and PicHeightInSamplesC are derived as follows:

[0076] CtbLog2SizeY=log2_ctu_size_minus2+2 (7-9)

[0077] CtbSizeY=1< <CtbLog2SizeY (7-10)

[0078] MinCbLog2SizeY=log2_min_luma_coding_block_size_minus2+2(7-11)

[0079] MinCbSizeY=1<<MinCbLog2SizeY(7-12)

[0080] MinTbLog2SizeY=2 (7-13)

[0081] MaxTbLog2SizeY=6 (7-14)

[0082] MinTbSizeY=1<<MinTbLog2SizeY (7-15)

[0083] MaxTbSizeY=1<<MaxTbLog2SizeY (7-16)

[0084] PicWidthInCtbsY=Ceil(pic_width_in_luma_samples÷CtbSizeY) (7-17)

[0085] PicHeightInCtbsY=Ceil(pic_height_in_luma_samples÷CtbSizeY) (7-18)

[0086] PicSizeInCtbsY=PicWidthInCtbsY*PicHeightInCtbsY (7-19)

[0087] PicWidthInMinCbsY=pic_width_in_luma_samples / MinCbSizeY (7-20)

[0088] PicHeightInMinCbsY=pic_height_in_luma_samples / MinCbSizeY (7-21)

[0089] PicSizeInMinCbsY=PicWidthInMinCbsY*PicHeightInMinCbsY (7-22)

[0090] PicSizeInSamplesY=pic_width_in_luma_samples*pic_height_in_luma_samples (7-23)

[0091] PicWidthInSamplesC=pic_width_in_luma_samples / SubWidthC (7-24)

[0092] PicHeightInSamplesC = pic_height_in_luma_samples / SubHeightC (7 - 25)

[0093] 3.3.2 CTUs in a Picture

[0094] Assume that the CTB / largest coding unit (LCU) size is represented by M × N (usually M equals N), and for a CTB located at the picture boundary (or slice or strip or other type of boundary, taking the picture boundary as an example), K × L samples are within the picture boundary, where K < M or L < N. For FIG. 6A to FIG. 6C those CTBs shown in, the CTB size is still equal to M × N. However, the lower boundary / right boundary of the CTB is outside the picture. FIG. 6A to FIG. 6C Examples of CTBs crossing the picture boundary are shown. In Fig. 6A , the CTB crosses the bottom picture boundary. In Figure 6B , the CTB crosses the right picture boundary. In Figure 6C , the CTB crosses the bottom - right picture boundary.

[0095] 3.4 Intra - prediction

[0096] Figure 7 Examples of 67 intra - prediction modes are shown. To capture any edge direction presented in natural videos, the number of directional intra - modes is extended from 33 used in HEVC to 65. Figure 7 Extended directional modes are shown, and the planar and direct current (DC) modes remain unchanged. These denser directional intra - prediction modes apply to all block sizes as well as luminance and chrominance intra - prediction.

[0097] The angular intra - prediction direction can be defined as from 45 degrees to - 135 degrees in the clockwise direction, as Figure 7 shown. In VTM, for non - square blocks, several angular intra - prediction modes are adaptively replaced with wide - angle intra - prediction modes. The replaced modes are signaled and remapped to the indices of the wide - angle modes after parsing. The total number of intra - prediction modes remains unchanged, e.g., 67, and the intra - mode coding remains unchanged.

[0098] In HEVC, each intra - coded block has a square shape, and the length of each side of the block is a power of 2. Therefore, no division operation is required to generate an intra - predictor using the DC mode. In VVC, blocks can have a rectangular shape, and in general, a division operation must be used for each block. To avoid the division operation for DC prediction, only the longer side is used to calculate the average value of non - square blocks.

[0099] 3.5 Inter - prediction

[0100] For each inter-predicted CU, the motion parameters include motion vector, reference picture index, reference picture list usage index, and new codec features for VVC for extended information of sample generation for inter-prediction. Motion parameters can be signaled explicitly or implicitly. When a CU is encoded and decoded using skip mode, the CU is associated with one PU and has no significant residual coefficients, no coded motion vector increments and / or reference picture indexes. A Merge mode is specified, by which the motion parameters of the current CU are obtained from neighboring CUs, including spatial and temporal candidates and extended scheduling introduced in VVC. Merge mode can be applied to any inter-predicted CU, not just skip mode. An alternative to Merge mode is to explicitly send motion parameters, where motion vectors, corresponding reference picture indexes for each reference picture list, reference picture list usage flags, and other useful information are explicitly signaled per CU.

[0101] 3.6 Deblocking Filter

[0102] Deblocking filtering is an example loop filter in a video codec. In VVC, the deblocking filtering process is applied to CU boundaries, transform subblock boundaries, and predicted subblock boundaries. Prediction subblock boundaries include prediction unit boundaries introduced by subblock-based temporal motion vector prediction (SbTMVP) and affine mode. Transform subblock boundaries include transform unit boundaries introduced by subblock transform (SBT) and intra sub-partitioning (ISP) mode, as well as transforms due to implicit partitioning of large CUs. The processing order of the deblocking filter is defined as first filtering the vertical edges of the entire image horizontally, and then filtering the horizontal edges vertically. This specific order enables multiple horizontal filtering or vertical filtering processes to be applied in parallel threads. The filtering process can also be implemented CTB by CTB, and the processing delay is very small.

[0103] First, filter the vertical edges in the picture. Then, use the samples modified by the vertical edge filtering process as input to filter the horizontal edges in the picture. The vertical and horizontal edges in the CTB of each CTU are processed separately according to the codec unit. Filter the vertical edges of the codec blocks in the codec unit starting from the edge on the left side of the codec block and proceeding to the edge on the right side of the codec block in the geometric order of the codec blocks. Filter the horizontal edges of the codec blocks in the codec unit starting from the edge at the top of the codec block and proceeding to the edge at the bottom of the codec block in the geometric order of the codec blocks.

[0104] Figure 8 Examples of block boundaries in a picture are shown. Figure 8Picture samples on an 8x8 grid are shown, along with horizontal and vertical block boundaries, and non-overlapping blocks of 8x8 samples, which can be deblocked in parallel.

[0105] 3.6.1 Boundary Decision

[0106] The filtering is applied to 8×8 block boundaries. In addition, such boundaries must be transform block boundaries or coding sub-block boundaries, for example due to the use of affine motion prediction (such as Advanced Temporal Motion Vector Prediction (ATMVP)). For other boundaries, deblocking filtering is disabled.

[0107] 3.6.2 Boundary strength calculation

[0108] For transform block boundaries / coding sub-block boundaries, if the boundary is within the 8×8 grid, the boundary can be filtered and the settings of bS[xDi][yDj] of the edge (where [xDi][yDj] represents the coordinates) are defined as in Table 2 and Table 3, respectively.

[0109]

[0110] Table 2 Boundary Strength (When SPS IBC is disabled)

[0111]

[0112] Table 3 Boundary Strength (When SPS IBC is Enabled)

[0113] 3.6.3 Deblocking Decision for Luminance Component

[0114] Fig. 9 An example of pixels involved in filter use is shown. Filter on / off decisions and strong / weak filter selection involve such pixels. The wider-stronger luminance filter is a filter that will be used only when conditions 1, 2, and 3 are all true (TRUE). Condition 1 is the "large block condition". This condition detects whether the samples on the P side and Q side belong to large blocks, represented by variables bSidePisLargeBlk and bSideQisLargeBlk, respectively. bSidePisLargeBlk and bSideQisLargeBlk are defined as follows.

[0115] bSidePisLargeBlk = ((edge ​​type is vertical and p0 belongs to a CU with width>=32) || (edge ​​type is horizontal and p0 belongs to a CU with height>=32))? True: False

[0116] bSideQisLargeBlk = ((edge ​​type is vertical and q0 belongs to a CU with width>=32) || (edge ​​type is horizontal and q0 belongs to a CU with height>=32))? True: False

[0117] Based on bSidePisLargeBlk and bSideQisLargeBlk, condition 1 is defined as follows:

[0118] Condition 1 = (bSidePisLargeBlk || bSidePisLargeBlk)? True: False

[0119] Next, if condition 1 is true, we further check condition 2. First, we derive the following variables:

[0120] First, derive dp0, dp3, dq0, dq3 according to the HEVC method

[0121] if (side p is greater than or equal to 32)

[0122] dp0=(dp0+Abs(p50-2*p40+p30)+1)>>1

[0123] dp3=(dp3+Abs(p53-2*p43+p33)+1)>>1

[0124] if (q side is greater than or equal to 32)

[0125] dq0=(dq0+Abs(q50-2*q40+q30)+1)>>1

[0126] dq3=(dq3+Abs(q53-2*q43+q33)+1)>>1

[0127] Condition 2 = (d < β)? True: False

[0128] Where d=dp0+dq0+dp3+dq3.

[0129] If conditions 1 and 2 are valid, then further check if any of the blocks use sub-blocks:

[0130]

[0131] Finally, if both conditions 1 and 2 are valid, the deblocking method will check condition 3 (large block strong filter condition), which is defined as follows. In condition 3 StrongFilterCondition, the following variables are derived:

[0132] Derive dpq in the same way as HEVC.

[0133] Derived according to HEVC method sp3 = Abs (p3-p0)

[0134] if (side p is greater than or equal to 32)

[0135]

[0136] According to the HEVC method, sq3 = Abs (q0-q3) is derived

[0137] if (q side is greater than or equal to 32)

[0138]

[0139] According to HEVC, StrongFilterCondition = (dpq is less than (β>>2), sp3+sq3 is less than (3*β>>5), and Abs(p0-q0) is less than (5*tC+1)>>1)? True: False

[0140] 3.6.4 Stronger Luminance Deblocking Filter

[0141] When samples on either side of the boundary belong to a large block, a bilinear filter is used. When the width of the vertical edge is >= 32 and when the height of the horizontal edge is >= 32, the sample is defined as belonging to a large block. The bilinear filter is listed as follows. Block boundary samples pi (i=0 to Sp-1) and qi (j=0 to Sq-1), in the above HEVC deblocking, pi and qi are the i-th sample in the row for filtering the vertical edge, or the i-th sample in the column for filtering the horizontal edge, and then replaced by linear interpolation as shown below:

[0142] p i ′=(fi i *Middle s,t +(64-f i )*P s +32)>>6),clippedtop i ±tcPD i

[0143] q j ′=(g j *Middle s,t +(64-g j )*Q s +32)>>6),clippedtoq j ±tcPD j

[0144] where tcPD i and tcPD jThe term is the position-dependent clipping described above, and g j 、f i 、Middle s,t , P s and Q s Given below.

[0145] 3.6.5 Chroma Deblocking Decision

[0146] A chroma strong filter is used on both sides of the block boundary. Here, the chroma filter is selected when both sides of the chroma edge are greater than or equal to 8 (chroma position), and the decision that meets the following three conditions: The first decision is the decision of boundary strength and large blocks. This filter can be applied when the block width or height orthogonal to the block edge is equal to or greater than 8 in the chroma sample domain. The second and third decisions are basically the same as the HEVC luma deblocking decisions, which are on / off decisions and strong filtering decisions, respectively.

[0147] In the first decision, the boundary strength (bS) is modified for chroma filtering, and the conditions are checked sequentially. If the condition is met, the remaining conditions with lower priority are skipped. Chroma deblocking is performed when bS is equal to 2, or bS is equal to 1 when a large block boundary is detected. The second and third conditions are basically the same as the HEVC luma strong filter decision, as shown below.

[0148] Under the second condition, d is derived according to HEVC luma deblocking. The second condition will be true when d is less than β.

[0149] Under the third condition, StrongFilterCondition is derived as follows:

[0150] Derive dpq in the same way as HEVC.

[0151] Derived according to HEVC method sp3 = Abs (p3-p0)

[0152] According to the HEVC method, sq3 = Abs (q0-q3) is derived

[0153] According to HEVC design, StrongFilterCondition = (dpq is less than (β>>2), sp3+sq3 is less than (β>>3), and Abs(p0-q0) is less than (5*tC+1)>>1)

[0154] 3.6.6 Strong Deblocking Filter for Chroma

[0155] Define the following strong deblocking filter for chroma:

[0156] p2′=(3*p3+2*p2+p1+p0+q0+4)>>3

[0157] p1′=(2*p3+p2+2*p1+p0+q0+q1+4)>>3

[0158] p0′=(p3+p2+p1+2*p0+q0+q1+q2+4)>>3

[0159] The example chroma filter performs deblocking on a 4x4 grid of chroma samples.

[0160] 3.6.7 Position-dependent limiting

[0161] Position dependent clipping (tcPD) is applied to the output samples of the luma filtering process and involves strong and long filters that modify 7, 5, and 3 samples at the boundaries. Assuming a quantization error distribution, the clipping value can be increased for samples that are expected to have higher quantization noise, so the reconstructed sample values ​​are expected to deviate more from the true sample values.

[0162] For each P or Q boundary filtered with an asymmetric filter, a position-dependent threshold table is selected from two tables (e.g., Tc7 and Tc3 listed below) that are provided to the decoder as auxiliary information, based on the result of the decision-making process:

[0163] Tc7={6,5,4,3,2,1,1}; Tc3={6,4,2};

[0164] tcPD=(Sp==3)? Tc3:Tc7;

[0165] tcQD=(Sq==3)? Tc3:Tc7;

[0166] For P or Q boundaries filtered with a short symmetric filter, a lower magnitude position-dependent threshold is applied:

[0167] Tc3 = {3, 2, 1};

[0168] After defining the thresholds, the filtered p'i and q'i sample values ​​are clipped according to the tcP and tcQ clipping values:

[0169] p”i=Clip3(p’i+tcPi,p’i–tcPi,p’i);

[0170] q”j=Clip3(q’j+tcQj,q’j–tcQ j,q’j);

[0171] Where p'i and q'i are the filtered sample values, p"i and q"j are the clipped output sample values, and tcPitcPi is the clipping threshold derived from the VVC tc parameters and tcPD and tcQD. Function Clip3 is the clipping function as specified in VVC.

[0172] 3.6.8 Sub-block deblocking adjustment

[0173] To achieve parallel-friendly deblocking using both long filters and sub-block deblocking, the long filter is restricted to modifying at most 5 samples on one side using sub-block deblocking (AFFINE or ATMVP or decoder-side motion vector refinement (DMVR)), as shown in the luma control of the long filter. In addition, sub-block deblocking is adjusted so that sub-block boundaries on the 8×8 grid close to CU or implicit TU boundaries are restricted to modifying at most two samples on each side.

[0174] The following applies to sub-block boundaries that are not aligned with CU boundaries.

[0175] If(mode block Q==SUBBLOCKMODE&&edge!=0){

[0176]

[0177] Where edge equal to 0 corresponds to a CU boundary, edge equal to 2 or equal to orthogonalLength-2 corresponds to a sub-block boundary 8 samples away from the CU boundary, etc. If implicit partitioning of TUs is used, implicitTU is true.

[0178] 3.7 Sample Adaptive Offset

[0179] Sample adaptive offset (SAO) is applied to the reconstructed signal after the deblocking filter by using the offset specified by the encoder for each CTB. The video encoder first decides whether to apply SAO processing to the current strip. If SAO is applied to the strip, each CTB will be classified into one of five SAO types, as shown in Table 4. The concept of SAO is to classify pixels into multiple categories and reduce distortion by adding offsets to pixels of each category. SAO operations include: edge offset (EO), which uses edge attributes for pixel classification in SAO types 1 to 4; and band offset (BO), which uses pixel intensity for pixel classification in SAO type 5. Each applicable CTB has SAO parameters, including sao_merge_left_flag, sao_merge_up_flag, SAO type, and four offsets. If sao_merge_left_flag is equal to 1, the current CTB will reuse the SAO type and offset of the left CTB. If sao_merge_up_flag is equal to 1, the current CTB will reuse the SAO type and offset of the CTB above.

[0180] SAO Type The type of sample adaptive offset to use Number of categories 0 none 0 1 1-D 0 degree pattern edge offset 4 2 1-D 90 degree pattern edge offset 4 3 1-D 135 degree pattern edge offset 4 4 1-D 45 degree pattern edge offset 4 5 Band offset 4

[0181] Table 4 SAO type regulations

[0182] 3.7 Adaptive Loop Filter

[0183] Adaptive loop filtering for video codecs minimizes the mean square error between the original samples and the decoded samples by using a Wiener-based adaptive filter. ALF is located at the last processing stage of each picture and can be regarded as a tool to capture and repair artifacts from previous stages. The appropriate filter coefficients are determined by the encoder and explicitly signaled to the decoder. In order to achieve better coding efficiency, especially for high-resolution video, local adaptation is used for the luminance signal by applying different filters to different areas or blocks in the picture. In addition to filter adaptation, filter on / off control at the codec tree unit (CTU) level also helps to improve coding efficiency. Syntactically, the filter coefficients are sent in a picture-level header called an adaptive parameter set, and the filter on / off flag of the CTU is interleaved at the CTU level in the slice data. This syntax design not only supports picture-level optimization, but also achieves lower coding latency.

[0184] 3.8.1 Signaling of parameters

[0185] According to the ALF design in VTM, the filter coefficients and clipping index are contained in the ALF APS. The ALF APS can include up to 8 chroma filters and one luminance filter set, for a total of up to 25 filters. For each of the 25 luminance classes, an index is also included. Classes with the same index share the same filter. By merging different classes, the number of bits required to represent the filter coefficients is reduced. The absolute value of the filter coefficient is represented using a 0th order Exp-Golomb code followed by the sign bit of the non-zero coefficient. When clipping is enabled, a two-bit fixed-length code is also used to signal the clipping index for each filter coefficient. The decoder can use up to 8 ALF APS simultaneously.

[0186] The filter control syntax elements of ALF in VTM include two types of information. First, the ALF on / off flag signal is signaled at the sequence, picture, slice, and CTB levels. The chroma ALF can be enabled at the picture and slice levels only when the luma ALF is enabled at the corresponding level. Secondly, if ALF is enabled at the picture, slice, and CTB levels, the filter usage information is signaled at that level. If all slices within a picture use the same APS, the referenced ALF APS ID is encoded at the slice level or picture level. The luma component can reference up to 7 ALF APSs, while the chroma component can reference up to 1 ALF APS. For the luma CTB, an index is signaled to indicate which ALF APS or offline trained luma filter set to use. For the chroma CTB, the index indicates which filter in the referenced APS to use.

[0187] The ALF data syntax elements associated with the LUMA component in the VTM are listed below:

[0188]

[0189]

[0190] alf_luma_filter_signal_flag equal to 1 specifies that the luma filter set is signaled. alf_luma_filter_signal_flag equal to 0 specifies that the luma filter set is not signaled. alf_luma_clip_flag equal to 0 specifies that linear adaptive loop filtering is applied to the luma component. alf_luma_clip_flag equal to 1 specifies that nonlinear adaptive loop filtering may be applied to the luma component. alf_luma_num_filters_signalled_minus1 plus 1 specifies the number of adaptive loop filter classes that may be signaled for the luma coefficient signal. The value of alf_luma_num_filters_signalled_minus1 shall be in the range of 0 to NumAlfFilters-1, inclusive. alf_luma_coeff_delta_idx[filtIdx] specifies the index of the signaled adaptive loop filter luma coefficient delta for the filter class indicated by filtIdx, in the range of 0 to NumAlfFilters-1. When alf_luma_coeff_delta_idx[filtIdx] is not present, it is inferred to be equal to 0. The length of alf_luma_coeff_delta_idx[filtIdx] is Ceil(Log2(alf_luma_num_filters_signalled_minus1+1)) bits. The value of alf_luma_coeff_delta_idx[filtIdx] shall be in the range of 0 to alf_luma_num_filters_signalled_minus1, inclusive.

[0191] alf_luma_coeff_abs[sfIdx][j] specifies the absolute value of the j-th coefficient of the signaled luma filter indicated by sfIdx. When alf_luma_coeff_abs[sfIdx][j] is not present, it is inferred to be equal to 0. The value of alf_luma_coeff_abs[sfIdx][j] shall be in the range of 0 to 128, inclusive. alf_luma_coeff_sign[sfIdx][j] specifies the sign of the j-th luma coefficient of the filter indicated by sfIdx, as follows:

[0192] If alf_luma_coeff_sign[sfIdx][j] is equal to 0, the corresponding luma filter coefficient has a positive value.

[0193] Otherwise (alf_luma_coeff_sign[sfIdx][j] is equal to 1), the corresponding luma filter coefficient has a negative value.

[0194] When alf_luma_coeff_sign[sfIdx][j] is not present, it is inferred to be equal to 0.

[0195] 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. When alf_luma_clip_idx[sfIdx][j] is not present, it is inferred to be equal to 0. The codec tree syntax elements associated with the LUMA component in the VTM are listed below:

[0196]

[0197]

[0198] alf_ctb_flag[cIdx][xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] equal to 1 specifies that the adaptive loop filter is applied to the codec tree block of the color component indicated by cIdx of the codec tree unit at luma position (xCtb, yCtb). alf_ctb_flag[cIdx][xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] equal to 0 specifies that the adaptive loop filter is not applied to the codec tree block of the color component indicated by cIdx of the codec tree unit at luma position (xCtb, yCtb).

[0199] When alf_ctb_flag[cIdx][xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is not present, it is inferred to be equal to 0. alf_use_aps_flag equal to 0 specifies that one of the fixed filter sets is applied to the luma CTB. alf_use_aps_flag equal to 1 specifies that the filter set from the APS is applied to the luma CTB. When alf_use_aps_flag is not present, it is inferred to be equal to 0. alf_luma_prev_filter_idx specifies the previous filter applied to the luma CTB. The value of alf_luma_prev_filter_idx should be in the range of 0 to sh_num_alf_aps_ids_luma-1, inclusive. When alf_luma_prev_filter_idx is not present, it is inferred to be equal to 0.

[0200] The variable AlfCtbFiltSetIdxY[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] specifies the filter set index of the luma CTB at position (xCtb, yCtb) derived as follows:

[0201] If alf_use_aps_flag is equal to 0, AlfCtbFiltSetIdxY[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is set equal to alf_luma_fixed_filter_idx.

[0202] Otherwise, AlfCtbFiltSetIdxY[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is set equal to 16+alf_luma_prev_filter_idx.

[0203] alf_luma_fixed_filter_idx specifies the fixed filter applied to the luma CTB. The value of alf_luma_fixed_filter_idx should be in the range of 0 to 15 (inclusive).

[0204] Based on the ALF design of VTM, the ALF design of ECM further introduces the concept of alternative filter sets into the luminance filter. Based on the updated luminance CTU ALF on / off decision of each alternative / round, the luminance filter is trained for multiple alternatives / rounds. In this way, there will be multiple filter sets associated with each training alternative, and the class merging results of each filter set may be different. Each CTU can select the best filter set by RDO and signal the relevant alternative information. The ALF data syntax elements associated with the LUMA component in ECM are listed below:

[0205]

[0206] alf_luma_num_alts_minus1 plus 1 specifies the number of alternative filter sets for the luma component. The value of alf_luma_num_alts_minus1 should be in the range of 0 to 3, inclusive. alf_luma_clip_flag[altIdx] equal to 0 specifies that linear adaptive loop filtering is applied to the alternative luma filter set with index altIdx luma component. alf_luma_clip_flag[altIdx] equal to 1 specifies that nonlinear adaptive loop filtering may be applied to the alternative luma filter set with index altIdx luma component. alf_luma_num_filters_signalled_minus1[altIdx] plus 1 specifies the number of adaptive loop filter classes that may signal luma coefficients to the alternative luma filter set with index altIdx. The value of alf_luma_num_filters_signalled_minus1[altIdx] should be in the range of 0 to NumAlfFilters-1, inclusive.

[0207] alf_luma_coeff_delta_idx[altIdx][filtIdx] specifies the index of the signaled adaptive loop filter luma coefficient delta for the filter class indicated by filtIdx, in the range 0 to NumAlfFilters–1 for the alternative luma filter set with index altIdx. When alf_luma_coeff_delta_idx[filtIdx][altIdx] is not present, it is inferred to be equal to 0. The length of alf_luma_coeff_delta_idx[altIdx][filtIdx] is Ceil(Log2(alf_luma_num_filters_signalled_minus1[altIdx]+1)) bits. The value of alf_luma_coeff_delta_idx[altIdx][filtIdx] shall be in the range of 0 to alf_luma_num_filters_signalled_minus1[altIdx], inclusive. alf_luma_coeff_abs[altIdx][sfIdx][j] specifies the absolute value of the j-th coefficient of the signaled luma filter indicated by sfIdx of the alternative luma filter set with index altIdx. When alf_luma_coeff_abs[altIdx][sfIdx][j] is not present, it is inferred to be equal to 0. The value of alf_luma_coeff_abs[altIdx][sfIdx][j] shall be in the range of 0 to 128, inclusive.

[0208] alf_luma_coeff_sign[altIdx][sfIdx][j] specifies the sign of the j-th luma coefficient of the filter indicated by sfIdx of the alternative luma filter set with index altIdx as follows:

[0209] If alf_luma_coeff_sign[altIdx][sfIdx][j] is equal to 0, the corresponding luma filter coefficient has a positive value.

[0210] Otherwise (alf_luma_coeff_sign[altIdx][sfIdx][j] is equal to 1), the corresponding luma filter coefficient has a negative value.

[0211] When alf_luma_coeff_sign[altIdx][sfIdx][j] is not present, it is inferred to be equal to 0.

[0212] alf_luma_clip_idx[altIdx][sfIdx][j] specifies the clip index of the clip value to be used before multiplying the j-th coefficient of the signaled luma filter represented by sfIdx of the alternative luma filter set indexed by altIdx. When alf_luma_clip_idx[altIdx][sfIdx][j] is not present, it is inferred to be equal to 0. The codec tree syntax elements associated with the luma component in the ECM are listed below:

[0213]

[0214]

[0215] alf_ctb_luma_filter_alt_idx[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] specifies the index of the alternative luma filter of the codec tree block applied to the luma component of the codec tree unit at luma position (xCtb, yCtb). When alf_ctb_luma_filter_alt_idx[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is not present, it is inferred to be equal to zero.

[0216] 3.8.2 Filter Shape

[0217] Fig.10 An example of filter shape for ALF is shown in FIG. 1 . In JEM, up to three diamond filter shapes can be selected for the luminance component (e.g. Fig.10 ). The filter shape for the luma component is indicated by a picture-level signaling index. Each square represents a sample, and Ci (i is 0 to 6 (left), 0 to 12 (middle), 0 to 20 (right)) represents the coefficient to be applied to the sample. For the chroma components in a picture, a 5×5 diamond shape is always used. In VVC, a 7×7 diamond shape is always used for luma, and a 5×5 diamond shape is always used for chroma.

[0218] 3.8.3 Classification of ALF

[0219] Each 2×2 (or 4×4) block is classified into one of 25 classes. The classification index C is based on the quantized value of its directionality D and activity The derivation is as follows:

[0220]

[0221] In order to calculate D and First, use the 1-dimensional Laplacian operator to calculate the gradient in the horizontal, vertical and two diagonal directions:

[0222]

[0223]

[0224] The indices i and j refer to the coordinates of the upper left sample point in the 2×2 block, and R(i,j) indicates the reconstructed sample point at the coordinate (i,j). Then, the maximum and minimum values ​​of the gradients D in the horizontal and vertical directions are set as:

[0225]

[0226] And the maximum and minimum values ​​of the gradients in the two diagonal directions are set to:

[0227]

[0228] To derive the value of the directionality D, these values ​​are compared with each other and with two thresholds t1 and t2:

[0229] Step 1. If and If both are true, D is set to 0.

[0230] Step 2. If Then continue from step 3; otherwise continue from step 4;

[0231] Step 3. If If yes, set D to 2; otherwise, set D to 1.

[0232] Step 4. If Then set D to 4; otherwise, set D to 3.

[0233] The activity value A is calculated as:

[0234]

[0235] A is further quantized into a range of 0 to 4 (inclusive), and the quantized value is represented as For the two chrominance components in a picture, no classification method is used, ie, a set of ALF coefficients is applied to each chrominance component.

[0236] 3.8.3 Geometric Transformation of Filter Coefficients

[0237] Before filtering each 2×2 block, geometric transformations such as rotation or diagonal and vertical flipping are applied to the filter coefficients f(k,l) associated with the coordinates (k,l) according to the gradient values ​​calculated for that block. This is equivalent to applying these transformations to the samples in the filter support region. The idea is to make different blocks more similar by aligning their directionality, to which the ALF is applied.

[0238] Introduce three geometric transformations, including diagonal transformation, vertical flip and rotation:

[0239] Diagonal: f D (k,l)=f(l,k),

[0240] Flip vertically: f V (k,l)=f(k,Kl-1),

[0241] Rotation: f R (k,l)=f(Kl-1,k).

[0242] Where K is the size of the filter, and 0≤k,l≤K-1 are the coefficient coordinates, so that the position (0,0) is at the upper left corner, and the position (K-1,K-1) is at the lower right corner. The transform is applied to the filter coefficients f(k,l) according to the gradient value calculated for the block. Table 5 summarizes the relationship between the transform and the four gradients in the four directions. Fig.11 An example of transform coefficients used as relative coordinates for a 5×5 diamond filter support is shown.

[0243] 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

[0244] Table 5. Gradient maps and transformations computed for a block.

[0245] 3.8.3 Filtering process

[0246] At the decoder side, when ALF is enabled for a block, each sample R(i,j) within the block is filtered to obtain the sample value R′(i,j) as shown below, where L represents the filter length and f m,n represents the filter coefficient, and f(k,l) represents the decoded filter coefficient.

[0247]

[0248] Fig.12 An example of relative coordinates for a 5×5 diamond filter support is shown, assuming that the coordinates (i, j) of the current sample point are (0, 0). Samples in different coordinates filled with the same color are multiplied by the same filter coefficient.

[0249] 3.8.3 Nonlinear Filter Reproduction

[0250] Linear filtering can be recast as follows without sacrificing coding efficiency:

[0251]

[0252] where w(i,j) are the same filter coefficients.

[0253] VVC introduces nonlinearity to make ALF more efficient by using a simple clipping function to reduce the impact of neighboring sample values ​​(I(x+i,y+j)) when they differ too much from the current sample value being filtered (I(x,y)). More specifically, the ALF filter is modified as follows:

[0254]

[0255] where K(d,b)=min(b,max(-b,d)) is the clipping function and k(i,j) are the clipping parameters, which depend on the (i,j) filter coefficients. The encoder performs an optimization to find the best k(i,j).

[0256] The clipping parameters k(i,j) are specified for each ALF filter, with one clipping value being signaled for each filter coefficient. This means that at most 12 clipping values ​​can be signaled in the bitstream for each luma filter, and at most 6 clipping values ​​can be signaled in the bitstream for each chroma filter. To limit the signaling cost and encoder complexity, only 4 fixed values ​​are used, which are the same for INTER and INTRA slices.

[0257] Because the variance of local differences in luma is usually higher than that of local differences in chroma, two different sets of luma filters and chroma filters are applied. A maximum sample value in each set (here 1024 for 10-bit bit depth) is also introduced so that clipping can be disabled when not needed. These 4 values ​​have been chosen by roughly evenly dividing the full range of sample values ​​for luma (encoded in 10 bits) and the range of 4 to 1024 for chroma in the logarithmic domain. More precisely, the luma table of clipping values ​​is obtained by the following formula:

[0258] Where M = 2 10 And N = 4

[0259] Similarly, the chromaticity table of the clipped value can be obtained according to the following formula:

[0260] Where M = 2 10 , N=4 and A=4

[0261] 3.9 Bilateral Loop Filter

[0262] 3.9.1 Bilateral Image Filter

[0263] Bilateral image filter is a nonlinear filter that smoothes noise while preserving edge structure. Bilateral filtering is a technique that makes the filter weight decrease not only with the distance between samples but also with the increase of intensity difference. In this way, edge oversmoothing can be improved. The weight is defined as

[0264]

[0265] where Δx and Δy are the vertical and horizontal distances, and ΔI is the intensity difference between the sample points.

[0266] The edge-preserving denoising bilateral filter uses a low-pass Gaussian filter for both the domain filter and the range filter. The domain low-pass Gaussian filter gives higher weights to pixels that are spatially close to the center pixel. The range low-pass Gaussian filter gives higher weights to pixels that are similar to the center pixel. Combining the range filter and the domain filter, the bilateral filter at the edge pixel becomes an elongated Gaussian filter that is oriented along the edge and greatly reduced in the gradient direction. This is why the bilateral filter can smooth out noise while preserving the edge structure.

[0267] 3.9.2 Bilateral Filters in Video Codecs

[0268] The bilateral filter in video codecs is a coding tool used in VVC [1]. The filter acts as a loop filter in parallel with the sample adaptive offset (SAO) filter. Both the bilateral filter and the SAO filter act on the same input samples, and each filter produces an offset, which is then added to the input samples to produce output samples, which are passed to the next stage after clipping. The spatial filter strength σ d Determined by the block size, the smaller the block, the greater the filter strength, and the intensity filter strength σ r Determined by the quantization parameter, where stronger filtering is used for higher QPs. Only the four closest samples are used, so the filtered sample strength I F can be calculated as

[0269]

[0270] Among them I C Indicates the intensity of the central sample point, ΔI A =I A -I C Indicates the intensity difference between the center sample point and the sample point above. ΔI B , ΔI L andΔI R Represents the intensity difference between the center sample and the samples below, to the left, and to the right, respectively.

[0271] 4. Technical problems solved by the disclosed technical solutions

[0272] An example design of an adaptive loop filter in a video codec system has the following problems. In the example ALF design, only spatially reconstructed samples before ALF processing are used for filter training and filtering. However, there is potentially other valuable information that can be utilized, such as samples filtered / generated by one or more predefined filters. In the example ALF design, only spatially reconstructed samples before ALF processing are used for filter training and filtering. However, other valuable information, such as samples before a deblocking filter (DBF), sample adaptive offset (SAO), or other stages, can potentially be utilized.

[0273] 5. List of solutions and implementation examples

[0274] In order to solve the above problems, a method as summarized below is disclosed. The embodiments should be regarded as examples for explaining general concepts and should not be interpreted narrowly. In addition, these embodiments can be applied individually or combined in any way. It should be noted that the disclosed method can be used as a loop filter or post-processing. In the present disclosure, a video unit can refer to a sequence, a picture, a sub-picture, a strip, a CTU, a block and / or a region. A video unit may include one color component or multiple color components. In the present disclosure, an ALF processing unit may refer to a sequence, a picture, a sub-picture, a strip, a CTU, a block, a region or a sample. An ALF processing unit may include one color component or multiple color components.

[0275] Example 1

[0276] In one example, at least one extended tap is used for the ALF filter to further enhance the efficiency of the ALF.

[0277] Example 2

[0278] In one example, at least one extended tap may be different from the spatial taps in the ALF filter. Different extended taps may utilize only the information of spatially neighboring samples of the target component. In one example, the spatially neighboring samples may come from a reconstruction before the ALF. In one example, the spatial taps may filter the central luma samples inside an ALF filter using only the spatially neighboring luma samples. In one example, the spatial taps may filter the central chroma samples inside an ALF filter using only the spatially neighboring chroma samples.

[0279] Example 3

[0280] In one example, at least one extended tap and at least one spatial domain tap may coexist within one ALF filter. In one example, the ALF filter may include both spatial domain taps and extended taps. In one example, the ALF filter may include M (e.g., M>0) spatial domain taps and N (e.g., N>0) extended taps.

[0281] Example 4

[0282] In one example, one or more extended taps of the ALF filter can use one or more input sources. In one example, one or more extended taps of the ALF filter can use one input source, such as the reconstructed sample before applying DBF or the intermediate filtering result of a predefined filter. In one example, one or more extended taps of the ALF filter can use multiple input sources, such as the reconstructed sample before applying DBF and the intermediate filtering result of a predefined filter. In one example, the input source of the extended tap can also be used by other taps in the ALF. In one example, the input source of the extended tap cannot be used by other taps in the ALF.

[0283] Example 5

[0284] In one example, whether and / or how to apply a filter with at least one extended tap may be different when processing different color components. In one example, an ALF filter with at least one extended tap may be applied only to process a luminance component. In one example, an ALF filter with at least one extended tap may be applied only to process one of the chrominance components (e.g., Cb or Cr components). In one example, an ALF filter with at least one extended tap may be applied to process all chrominance components. (e.g., both Cb and Cr components). In one example, an ALF filter with at least one extended tap may be applied to filter both luminance and chrominance components. (e.g., Y, Cb, and Cr components).

[0285] Example 6

[0286] In one example, the coefficients of the extended taps inside the ALF filter may correspond to one or more input samples. In one example, the coefficients of the extended taps inside the ALF filter may correspond to only one input sample. In one example, the coefficients of the extended taps inside the ALF filter may correspond to N input samples (e.g., N=2). In one example, the coefficients of the extended taps inside the ALF filter may be shared by multiple inputs based on geometric information. In one example, multiple input samples may be located in symmetrical positions.

[0287] Example 7

[0288] In one example, an ALF filter with and without at least one extended tap can be trained in different ways. In one example, training data collection for one or more extended taps of the ALF filter can be performed jointly with one or more spatial taps of the ALF filter. In one example, training data collection for one or more extended taps of the ALF filter can be performed independently. In one example, coefficients of one or more extended taps of the ALF filter can be jointly trained with one or more spatial taps of the ALF filter. In one example, coefficients of one or more extended taps of the ALF filter can be trained independently. In one example, parameters of one or more extended taps of the ALF filter (e.g., nonlinear clipping parameters) can be jointly derived with one or more spatial taps of the ALF filter. In one example, parameters of one or more extended taps of the ALF filter (e.g., nonlinear clipping parameters) can be derived independently.

[0289] Example 8

[0290] In one example, ALF filters with and without at least one extended tap may use different shapes or sizes. In one example, the ALF filter may include spatial domain taps and extended taps of different shapes. For example, the shape used for one or more spatial domain taps may be different from the shape used for one or more extended taps. In one example, within the ALF filter, the shape / size used for one or more spatial domain taps may be different from the shape / size used for one or more extended taps. In one example, within the ALF filter, the shape / size used for one or more spatial domain taps may be the same as the shape / size used for one or more extended taps.

[0291] Example 9

[0292] In one example, within an ALF filter with or without at least one extended tap, the filter shape for one or more spatial domain taps may be as described below. In one example, the filter shape for the spatial domain taps may be a diamond shape. In one example, the filter shape for the spatial domain taps may be a square shape. In one example, the filter shape for the spatial domain taps may be a cross shape. In one example, the filter shape for the spatial domain taps may be a symmetrical shape. In one example, the filter shape for the spatial domain taps may be an asymmetrical shape. In one example, the filter shape for the spatial domain taps may be other designed shapes. In one example, the filter shape for the spatial domain taps may be determined / signaled / derived on the fly.

[0293] Example 10

[0294] In one example, an ALF filter including at least one spatial domain tap and at least one extended tap can be designed as follows. In one example, one or more spatial domain taps can be used for filtering (e.g., the spatial domain taps can be regarded as reconstruction before ALF). In one example, the shape of at least one spatial domain tap can be different shapes. In one example, the shape of at least one spatial domain tap can be a rhombus. In one example, the shape of at least one spatial domain tap can be a cross. In one example, the shape of at least one spatial domain tap can be a square. In one example, the shape of at least one spatial domain tap can be a symmetrical shape. In one example, the shape of at least one spatial domain tap can be an asymmetrical shape. In one example, the filter size / length of the spatial domain tap can be N (e.g., N=5, 7, 9, 11, 13).

[0295] Example 11

[0296] Fig.13 An example of the shape of at least one spatial tap is shown. In one example, the Fig.13 Design the shape of the spatial taps.

[0297] Example 12

[0298] Fig.14 An example of a shape for at least one spatial tap is shown. In one example, the shape of the spatial tap may be as follows: Fig.14 design.

[0299] Example 13

[0300] In one example, one or more extended taps may be applied to filtering. In one example, the filter shape of one or more extended taps may be different shapes. In one example, the filter shape of one or more extended taps may be a rhombus. In one example, the filter shape of one or more extended taps may be a cross. In one example, the filter shape of one or more extended taps may be a square. In one example, the filter shape of one or more extended taps may be a symmetrical shape. In one example, the filter shape of one or more extended taps may be an asymmetrical shape. In one example, the filter size / length of one or more extended taps may be N (e.g., N=1, 3, 5, 7).

[0301] Example 14

[0302] Fig.15 An example of the shape of at least one extended tap is shown. In one example, the Fig.15 Design a filter shape with one or more extension taps. Fig.16 An example of the shape of at least one extended tap is shown. In one example, the Fig.16Design a filter shape with one or more extension taps. Fig.17 An example of the shape of at least one extended tap is shown. In one example, the Fig.17 Design a filter shape with one or more extension taps. Fig.18 An example of the shape of at least one extended tap is shown. In one example, the Fig.18 Design a filter shape with one or more extension taps.

[0303] In one example, the filter shapes mentioned above may be applied jointly. Fig.19 An example of the shape of at least one extended tap is shown. In one example, the Fig.19 Design a filter shape with one or more extension taps.

[0304] Fig. 20 An example of the shape of one or more extension taps is shown. In one example, the Fig. 20 Design a filter shape with one or more extension taps. Fig.21 An example of the shape of one or more extension taps is shown. In one example, the Fig.21 Design a filter shape with one or more extension taps. Fig. 22 An example of the shape of one or more extension taps is shown. In one example, the Fig. 22 Design a filter shape with one or more extension taps. Fig.23 An example of the shape of one or more extension taps is shown. In one example, the Fig.23 Design a filter shape with one or more extension taps. Fig.24 An example of the shape of one or more extension taps is shown. In one example, the Fig.24 Design a filter shape with one or more extension taps. Fig.25 An example of the shape of one or more extension taps is shown. In one example, the Fig.25 Design a filter shape with one or more extension taps. Fig.26 An example of the shape of one or more extension taps is shown. In one example, the Fig.26 Design a filter shape with one or more extension taps. Fig. 27 An example of the shape of one or more extension taps is shown. In one example, the Fig. 27 Design a filter shape with one or more extension taps. Fig.28 An example of the shape of one or more extension taps is shown. In one example, the Fig.28 Design a filter shape with one or more extension taps. Fig.29An example of the shape of one or more extension taps is shown. In one example, the Fig.29 Design a filter shape with one or more extension taps.

[0305] Fig.30 An example of the shape of one or more extension taps is shown. In one example, the Fig.30 Design a filter shape with one or more extension taps. Fig.31 An example of the shape of one or more extension taps is shown. In one example, the Fig.31 Design a filter shape with one or more extension taps. Fig.32 An example of the shape of one or more extension taps is shown. In one example, the Fig.32 Design a filter shape with one or more extension taps. Fig.33 An example of the shape of one or more extension taps is shown. In one example, the Fig.33 Design a filter shape with one or more extension taps. Fig.34 An example of the shape of one or more extension taps is shown. In one example, the Fig.34 Design a filter shape with one or more extension taps. Fig.35 An example of the shape of one or more extension taps is shown. In one example, the Fig.35 Design a filter shape with one or more extension taps. Fig.36 An example of the shape of one or more extension taps is shown. In one example, the Fig.36 Design a filter shape with one or more extension taps. Fig.37 An example of the shape of one or more extension taps is shown. In one example, the Fig.37 Design a filter shape with one or more extension taps. Fig.38 An example of the shape of one or more extension taps is shown. In one example, the Fig.38 Design a filter shape with one or more extension taps. Fig.39 An example of the shape of one or more extension taps is shown. In one example, the Fig.39 Design a filter shape with one or more extension taps.

[0306] Fig.40 An example of the shape of one or more extension taps is shown. In one example, the Fig.40 Design a filter shape with one or more extension taps. Fig.41 An example of the shape of one or more extension taps is shown. In one example, the Fig.41 Design a filter shape with one or more extension taps. Fig.42An example of the shape of one or more extension taps is shown. In one example, the Fig.42 Design a filter shape with one or more extension taps. Fig.43 An example of the shape of one or more extension taps is shown. In one example, the Fig.43 Design a filter shape with one or more extension taps. Fig.44 An example of the shape of one or more extension taps is shown. In one example, the Fig.44 Design a filter shape with one or more extension taps. Fig.45 An example of the shape of one or more extension taps is shown. In one example, the Fig.45 Design a filter shape with one or more extension taps. Fig.46 An example of the shape of one or more extension taps is shown. In one example, the Fig.46 Design a filter shape with one or more extension taps.

[0307] Example 15

[0308] In one example, a transposition based on geometric information may be applied. In one example, a transposition based on geometric information may be applied independently to one or more spatial domain taps. In one example, a transposition based on geometric information may be applied independently to one or more extended taps. In one example, a transposition based on geometric information may be applied jointly to one or more spatial domain taps and one or more extended taps.

[0309] Example 16

[0310] In one example, for at least one extended tap, there may be one or more inputs. In one example, one possible input source of one or more extended taps may be the reconstruction before the ALF of the current frame. In one example, one possible input source of one or more extended taps may be the intermediate filtering result generated by the reconstruction before the ALF of the current frame and the filter (fixed filter) trained offline of the ALF. In one example, one possible input source of one or more extended taps may be the reconstruction before the DBF of the current frame. In one example, one possible input source of one or more extended taps may be the intermediate filtering result generated by the reconstruction before the DBF of the current frame and the filter (fixed filter) trained offline. In one example, one possible input source of one or more extended taps may be the intermediate filtering result generated by the reconstruction before the ALF of the current frame and the predefined filter. In one example, one possible input source of one or more extended taps may be the intermediate filtering result generated by the reconstruction before the DBF of the current frame and the predefined filter. In one example, one possible input source of one or more extended taps may be the intermediate filtering result generated by the reconstruction before the DBF of the current frame and the predefined filter. In one example, the total number of extended taps inside the ALF filter can be derived jointly based on shape, filter length, and symmetry constraints.

[0311] Example 17

[0312] In one example, classification may be performed on an ALF filter having at least one extended tap. In one example, classification may be performed on an ALF filter having at least one extended tap based on texture information. In one example, texture information may be generated by gradient. In one example, texture information may be generated by variance. In one example, classification may be performed on an ALF filter having at least one extended tap based on frequency band information. In one example, frequency band information may be generated by the intensity of one or more input samples. In one example, classification results may be generated independently based on inputs of spatial domain taps of the filter. In one example, classification results may be generated independently based on inputs of extended taps of the filter. In one example, classification results may be jointly generated based on inputs of spatial domain taps and extended taps of the filter.

[0313] Example 18

[0314] In one example, whether and / or how to apply at least one extended tap in the ALF may depend on the classification in the ALF. In one example, the classification may be based on the gradient information of the input source. In one example, the input source may be a reconstruction before the ALF. In one example, the input source may be a reconstruction before the DBF. In one example, the input source may be an intermediate filtering result. In one example, the classification may be based on the frequency band information of the input source. In one example, the input source may be a reconstruction before the ALF. In one example, the input source may be a reconstruction before the DBF. In one example, the input source may be an intermediate filtering result.

[0315] Example 19

[0316] In one example, the input samples of the extended tap may be padded samples between picture, slice, slice and / or CTU boundaries. In one example, padding may be applied to any boundary during encoding and / or decoding. In one example, padding may be applied to picture and / or sub-picture boundaries. In one example, padding may be applied to slice and / or slice boundaries. In one example, padding may be applied to CTU and / or CTB boundaries. In one example, padding may be applied to CU, TU and / or PU boundaries. In one example, padding may be applied to block boundaries. In one example, padding may be applied to unit boundaries. In one example, padding may be applied to virtual boundaries. In one example, padding may be applied to any other type of boundary. In one example, different padding methods may be applied to boundaries. In one example, extended padding may be applied. In one example, mirror padding may be applied. In one example, repeated padding may be applied. In one example, other padding methods may be applied.

[0317] Example 20

[0318] In one example, a first syntax element may be signaled, the first syntax element indicating whether a filter having at least one extended tap is enabled. In one example, the first syntax element may be encoded and decoded by arithmetic coding and decoding. In one example, the first syntax element may be encoded and decoded with at least one context. The context may depend on the coding and decoding information of the current block or the adjacent block. The context may depend on the filter shape of at least one adjacent block. In one example, the first syntax element may be encoded and decoded with bypass coding and decoding. In one example, the first syntax element may be binarized by a unary code, a truncated unary code, a fixed length code, an exponential Golomb code, a truncated exponential Golomb code, etc. In one example, the first syntax element may be conditionally signaled. For example, the first syntax element may be signaled only when the extended tap is available. The first syntax element may be encoded and decoded in a predictive manner. The first syntax element may be predicted by an on and / or off decision of an extended tap of at least one adjacent block. The first syntax element may be signaled independently for different color components. In an example, the first syntax element may be signaled and shared for different color components. In an example, a first syntax element may be signaled for a first color component, but not for a second color component. Syntax elements may be signaled in a sequence parameter set (SPS), a picture parameter set (PPS), a picture header, a slice header, an adaptation parameter set (APS), a codec tree unit (CTU), a codec unit (CU), etc.

[0319] Example 21

[0320] In one example, at least one coefficient of one or more filters having at least one extended tap may be signaled in a syntax element structure such as an APS. In one example, the coefficients of the extended taps may be included in the APS. In one example, the clipping parameters of the extended taps may be included in the APS. In one example, the class merging results of the extended taps may be included in the APS. In one example, the coefficients of the extended taps may be encoded and decoded in a predictive manner. In one example, the coefficients of the extended taps may be encoded and decoded using arithmetic coding and decoding using at least one context. In one example, the coefficients of the extended taps may be encoded and decoded using bypass coding and decoding. In one example, the coefficients of the extended taps may be jointly encoded and decoded with the coefficients of the spatial domain taps. In one example, other parameters of the extended taps may be included in the APS. In one example, the coefficients of the extended taps may be predefined fixed values.

[0321] Example 22

[0322] In one example, the intermediate filtering result of the filter is used as the input of one or more extension taps. In one example, the intermediate filtering result of the ALF filter trained offline can be used as the input of one or more extension taps. In one example, the intermediate filtering result of the ALF filter trained online can be used as the input of one or more extension taps. In one example, the intermediate filtering result of other predefined filters can be used as the input of one or more extension taps. In one example, a Gaussian filter can be applied. In one example, a bilateral filter can be applied. In one example, a guided filter can be applied. In one example, a median filter can be applied. In one example, a filter with a low-pass property can be applied. In one example, a filter with a high-pass property can be applied. In one example, the intermediate filtering results of other filters trained online can be used as the input of one or more extension taps. In one example, the input of the intermediate filtering can be a reconstructed sample at different encoding and decoding stages. In one example, the reconstruction before and / or after the ALF of the current / reference frame can be used to generate the intermediate filtering result. In one example, the reconstruction before and / or after the SAO and / or cross-component SAO (CCSAO) of the current and / or reference frame can be used to generate the intermediate filtering result. In one example, reconstruction before and / or after a bilateral filter (BIF) of a current and / or reference frame can be used to generate an intermediate filtering result. In one example, reconstruction before and / or after a DBF of a current / reference frame can be used to generate an intermediate filtering result. In one example, reconstruction before and / or after any other stage of a current and / or reference frame can be used to generate an intermediate filtering result.

[0323] Example 23

[0324] In one example, the reconstruction samples before or after different encoding and decoding stages of the current frame can be used as input to one or more extension taps. In one example, the reconstruction before and / or after the DBF of the current frame can be used as input to one or more extension taps. In one example, the reconstruction before and / or after the SAO and / or CCSAO of the current frame can be used as input to one or more extension taps. In one example, the reconstruction before and / or after the BIF of the current frame can be used as input to one or more extension taps. In one example, the reconstruction before and / or after other stages of the current frame can be used as input to one or more extension taps.

[0325] Example 24

[0326] In one example, whether and / or how to use the reconstructed samples before or after different encoding stages of the reference frame can be used as the input of the extension tap. In one example, the reconstruction before and / or after the DBF of the reference frame can be used as the input of the extension tap. In one example, the reconstruction before and / or after the DBF of a reference frame can be used as the input of the extension tap. In one example, the reconstruction before and / or after the DBF of multiple reference frames can be used as the input of the extension tap. In one example, the reconstruction before and / or after the SAO and / or CCSAO of the reference frame can be used as the input of the extension tap. In one example, the reconstruction before and / or after the SAO / CCSAO of a reference frame can be used as the input of the extension tap.

[0327] In one example, reconstructions before and / or after SAO and / or CCSAO of multiple reference frames may be used as inputs to the extension taps. In one example, reconstructions before and / or after BIF of a reference frame may be used as inputs to the extension taps. In one example, reconstructions before and / or after BIF of a reference frame may be used as inputs to the extension taps. In one example, reconstructions before and / or after BIF of multiple reference frames may be used as inputs to the extension taps. In one example, reconstructions before and / or after other stages of the reference frame may be used as inputs to the extension taps. In one example, reconstructions before and / or after other stages of a reference frame may be used as inputs to the extension taps. In one example, reconstructions before and / or after other stages of the reference frame may be used as inputs to the extension taps.

[0328] Example 27

[0329] In one example, the above mentioned methods can be used in combination.

[0330] Example 28

[0331] In one example, the above-mentioned methods can be used alone.

[0332] Example 28

[0333] In one example, the proposed / described method of extending taps for ALF may be applied to any loop filtering tool, pre-processing or post-processing filtering method in video codec (including but not limited to ALF / CCALF or any other filtering method). In one example, the proposed extended tap method may be applied to loop filtering methods. In one example, the proposed extended tap method may be applied to ALF. In one example, the proposed extended tap method may be applied to cross-component ALF (CCALF). In one example, the proposed extended tap method may be applied to other loop filtering methods. In one example, the proposed extended tap method may be applied to pre-processing filtering methods. In one example, the proposed extended tap method may be applied to post-processing filtering methods.

[0334] Example 29

[0335] In the above examples, a video unit may refer to a sequence / picture / sub-picture / slice / slice / codec tree unit (CTU) / CTU row / CTU group / codec unit (CU) / prediction unit (PU) / transform unit (TU) / codec tree block (CTB) / codec block (CB) / prediction block (PB) / transform block (TB) / any other region containing more than one luma or chroma sample / pixel.

[0336] Example 30

[0337] Whether and / or how to apply the methods disclosed above can be signaled in the bitstream. In one example, they can be signaled at the sequence level / picture group level / picture level / slice level / slice group level, such as in the sequence header, picture header, SPS, VPS, DPS, decoder capability information (DCI), PPS, APS, slice header, and slice group header. In one example, they can be signaled at the level of PB, TB, CB, PU, ​​TU, CU, virtual pipe data unit (VPDU), CTU, CTU row, slice, slice, sub-picture, other types of regions containing more than one sample or pixel.

[0338] Example 31

[0339] Whether and / or how to apply the above disclosed method may depend on codec information such as block size, color format, single / dual tree partitioning, color component, slice / picture type.

[0340] 6. References

[0341] J. Strom, P. Wennersten, J. Enhorn, D. Liu, K. Andersson and R. Sjoberg, "Bilateral Loop Filter in Combination with SAO," in proceeding of IEEE PictureCoding Symposium (PCS), Nov. 2019.

[0342] Fig.47 4000 is a block diagram illustrating an example video processing system 4000 in which various techniques disclosed herein may be implemented. Various implementations may include some or all of the components of system 4000. System 4000 may include an input 4002 for receiving video content. The video content may be received in a raw or uncompressed format (e.g., 8-bit or 10-bit multi-component pixel values), or may be received in a compressed or encoded format. Input 4002 may represent a network interface, a peripheral bus interface, or a storage interface. Examples of network interfaces include wired interfaces such as Ethernet, a passive optical network (PON), etc., and wireless interfaces such as Wi-Fi or a cellular interface.

[0343] System 4000 may include coding component 4004, which may implement various coding or coding methods described in this document. Coding component 4004 may reduce the average bit rate of the video from input 4002 to output of coding component 4004 to generate a coded representation of the video. Therefore, coding techniques are sometimes referred to as video compression or video transcoding techniques. The output of coding component 4004 may be stored or sent via connected communications, as shown in component 4006. The stored or transmitted bitstream representation (or codec representation) of the video received at input 4002 may be used by component 4008 to generate pixel values ​​or displayable video, which is sent to display interface 4010. The process of generating user-visible video from bitstream representation is sometimes referred to as video decompression. In addition, although some video processing operations are referred to as "coding" operations or tools, it should be understood that codec tools or operations are used in encoders, and decoders will perform corresponding decoding tools or operations of the reverse process of encoding.

[0344] Examples of peripheral bus interfaces or display interfaces may include Universal Serial Bus (USB) or High Definition Multimedia Interface (HDMI) or Display Port, etc. Examples of storage interfaces include Serial Advanced Technology Attachment (SATA), Peripheral Component Interconnect (PCI), Integrated Drive Electronics (IDE) interface, etc. The techniques described in this document may be embodied in various electronic devices such as mobile phones, laptop computers, smart phones, or other devices capable of performing digital data processing and / or video display.

[0345] Fig.48 4100. The device 4100 may be used to implement one or more methods described herein. The device 4100 may be implemented as a smart phone, a tablet computer, a computer, an Internet of Things (IoT) receiver, etc. The device 4100 may include one or more processors 4102, one or more memories 4104, and a video processing circuit 4106. The processor 4102 may be configured to implement one or more methods described in this document. The memory (memory) 4104 may be used to store data and code for implementing the methods and techniques described herein. The video processing circuit 4106 may be used to implement some of the techniques described in this document in a hardware circuit. In some embodiments, the video processing circuit 4106 may be at least partially included in the processor 4102 (e.g., a graphics coprocessor).

[0346] Fig.49 4200 is a flow chart of an example method 4200 for video processing. The method 4200 includes determining, at step 4202, to apply an adaptive loop filter (ALF) to a video unit. The ALF includes at least one extension tap. At step 4204, performing conversion between visual media data and a bitstream based on the ALF. According to an example, the conversion of step 4204 may include encoding at an encoder or decoding at a decoder.

[0347] It should be noted that method 4200 may be implemented in a device for processing video data, the device comprising a processor and a non-transitory memory having instructions thereon, such as video encoder 4400, video decoder 4500, and / or encoder 4600. In this case, the instructions, when executed by the processor, cause the processor to perform method 4200. In addition, method 4200 may be performed by a non-transitory computer-readable medium including a computer program product for use by a video codec device. The computer program product includes computer executable instructions stored on a non-transitory computer-readable medium, such that when executed by a processor, the video codec device performs method 4200.

[0348] Fig.50 43 is a block diagram illustrating an example video codec system 4300 that can utilize the techniques of the present disclosure. The video codec system 4300 may include a source device 4310 and a target device 4320. The source device 4310 generates encoded video data, which may be referred to as a video codec device. The target device 4320 may decode the encoded video data generated by the source device 4310, which may be referred to as a video decoding device.

[0349] Source device 4310 may include video source 4312, video encoder 4314 and input / output (I / O) interface 4316. Video source 4312 may include a source such as a video capture device, an interface for receiving video data from a video content provider and / or a computer graphics system for generating video data, or a combination of such sources. Video data may include one or more pictures. Video encoder 4314 encodes video data from video source 4312 to generate a bitstream. The bitstream may include a series of bits that form a codec representation of video data. The bitstream may include codec pictures and associated data. Codec pictures are codec representations of pictures. Associated data may include sequence parameter sets, picture parameter sets and other syntax structures. I / O interface 4316 may include a modulator / demodulator (modem) and / or a transmitter. The encoded video data may be directly sent to target device 4320 via network 4330 via I / O interface 4316. The encoded video data may also be stored on storage medium / server 4340 for access by target device 4320.

[0350] Target device 4320 may include an I / O interface 4326, a video decoder 4324, and a display device 4322. The I / O interface 4326 may include a receiver and / or a modem. The I / O interface 4326 may obtain encoded video data from source device 4310 or storage medium / server 4340. The video decoder 4324 may decode the encoded video data. The display device 4322 may display the decoded video data to a user. The display device 4322 may be integrated with the target device 4320, or may be external to the target device 4320, which may be configured to interface with an external display device.

[0351] The video encoder 4314 and the video decoder 4324 may operate according to a video compression standard, such as the High Efficiency Video Codec (HEVC) standard, the Versatile Video Codec (VVM) standard, and other current and / or additional standards.

[0352] Fig.51 is a block diagram showing an example of a video encoder 4400, which may be Fig.50 Video encoder 4314 in system 4300 shown. Video encoder 4400 can be configured to perform any or all of the techniques of the present disclosure. Video encoder 4400 includes multiple functional components. The techniques described in the present disclosure can be shared between the various components of video encoder 4400. In some examples, the processor can be configured to perform any or all of the techniques described in the present disclosure.

[0353] The functional components of the video encoder 4400 may include a segmentation unit 4401, a prediction unit 4402, a residual generation unit 4407, a transform processing unit 4408, a quantization unit 4409, an inverse quantization unit 4410, an inverse transform unit 4411, a reconstruction unit 4412, a buffer 4413, and an entropy coding unit 4414. The prediction unit 4402 may include a mode selection unit 4403, a motion estimation unit 4404, a motion compensation unit 4405, and an intra-frame prediction unit 4406.

[0354] In other examples, the video encoder 4400 may include more, fewer, or different functional components. In an example, the prediction unit 4402 may include an intra-block copy (IBC) unit. The IBC unit may perform prediction in an IBC mode, where at least one reference picture is a picture where the current video block is located.

[0355] Furthermore, some components, such as the motion estimation unit 4404 and the motion compensation unit 4405 , may be highly integrated but are represented separately in the example of the video encoder 4400 for explanation purposes.

[0356] The partitioning unit 4401 can partition the picture into one or more video blocks. The video encoder 4400 and the video decoder 4500 can support various video block sizes.

[0357] The mode selection unit 4403 may select one of the coding modes, for example, based on the error result, and provide the resulting intra-frame or inter-frame codec block to the residual generation unit 4407 to generate residual block data and provide it to the reconstruction unit 4412 to reconstruct the codec block for use as a reference picture. In some examples, the mode selection unit 4403 may select a combined intra and inter prediction (CIIP) mode, where the prediction is based on an inter prediction signal and an intra prediction signal. The mode selection unit 4403 may also select a resolution of motion vectors for the block in the case of inter prediction (e.g., sub-pixel or integer pixel precision).

[0358] To perform inter-frame prediction on the current video block, the motion estimation unit 4404 may generate motion information for the current video block by comparing one or more reference frames from the buffer 4413 with the current video block. The motion compensation unit 4405 may determine a predicted video block for the current video block based on the motion information and decoded samples of a picture from the buffer 4413 instead of the picture associated with the current video block.

[0359] The motion estimation unit 4404 and the motion compensation unit 4405 may perform different operations on the current video block, for example, depending on whether the current video block is in an I slice, a P slice, or a B slice.

[0360] In some examples, the motion estimation unit 4404 may perform unidirectional prediction on the current video block, and the motion estimation unit 4404 may search for a reference video block for the current video block in the reference pictures of list 0 or list 1. The motion estimation unit 4404 may then generate a reference index indicating a reference picture in list 0 or list 1, the reference picture containing the reference video block and a motion vector indicating a spatial displacement between the current video block and the reference video block. The motion estimation unit 4404 may output the reference index, the prediction direction indicator, and the motion vector as motion information of the current video block. The motion compensation unit 4405 may generate a predicted video block of the current block based on the reference video block indicated by the motion information of the current video block.

[0361] In other examples, the motion estimation unit 4404 may perform bidirectional prediction on the current video block, and the motion estimation unit 4404 may search for a reference video block of the current video block in the reference pictures in list 0, and may also search for another reference video block of the current video block in the reference pictures in list 1. The motion estimation unit 4404 may then generate a reference index indicating a reference picture in list 0 and list 1, the reference picture containing a reference video block and a motion vector indicating a spatial displacement between the reference video block and the current video block. The motion estimation unit 4404 may output the reference index and the motion vector of the current video block as motion information of the current video block. The motion compensation unit 4405 may generate a predicted video block of the current video block based on the reference video block indicated by the motion information of the current video block.

[0362] In some examples, motion estimation unit 4404 may output a complete set of motion information for use in a decoding process of a decoder. In some examples, motion estimation unit 4404 may not output a complete set of motion information for the current video. Rather, motion estimation unit 4404 may reference motion information of another video block to signal motion information of the current video block. For example, motion estimation unit 4404 may determine that motion information of the current video block is sufficiently similar to motion information of an adjacent video block.

[0363] In one example, the motion estimation unit 4404 may indicate a value in a syntax structure associated with the current video block that indicates to the video decoder 4500 that the current video block has the same motion information as another video block.

[0364] In another example, the motion estimation unit 4404 can identify another video block and a motion vector difference (MVD) in a syntax structure associated with the current video block. The motion vector difference indicates the difference between the motion vector of the current video block and the motion vector of the indicated video block. The video decoder 4500 can use the motion vector of the indicated video block and the motion vector difference to determine the motion vector of the current video block.

[0365] As discussed above, the video encoder 4400 may predictively signal motion vectors.Two examples of predictive signaling techniques that may be implemented by the video encoder 4400 include Advanced Motion Vector Prediction (AMVP) and Merge mode signaling.

[0366] The intra prediction unit 4406 may perform intra prediction on the current video block. When the intra prediction unit 4406 performs intra prediction on the current video block, the intra prediction unit 4406 may generate prediction data for the current video block based on decoded samples of other video blocks in the same picture. The prediction data for the current video block may include the predicted video block and various syntax elements.

[0367] The residual generating unit 4407 may generate residual data for the current video block by subtracting the predicted video block of the current video block from the current video block. The residual data of the current video block may include residual video blocks corresponding to different sample components of the samples in the current video block.

[0368] In other examples, such as in skip mode, there may be no residual data for the current video block of the current video block, and the residual generation unit 4407 may not perform a subtraction operation.

[0369] The transform processing unit 4408 may generate a transform coefficient video block for a current video block by applying one or more transforms to the residual video block associated with the current video block.

[0370] After the transform processing unit 4408 generates a transform coefficient video block associated with the current video block, the quantization unit 4409 may quantize the transform coefficient video block associated with the current video block based on one or more quantization parameter (QP) values ​​associated with the current video block.

[0371] The inverse quantization unit 4410 and the inverse transform unit 4411 may apply inverse quantization and inverse transform to the transform coefficient video block, respectively, to reconstruct a residual video block from the transform coefficient video block. The reconstruction unit 4412 may add the reconstructed residual video block to corresponding samples from one or more predicted video blocks generated by the prediction unit 4402 to generate a reconstructed video block associated with the current block for storage in the buffer 4413.

[0372] After the reconstruction unit 4412 reconstructs the video block, a loop filtering operation may be performed to reduce video blocking effects in the video block.

[0373] The entropy coding unit 4414 may receive data from other functional components of the video encoder 4400. When the entropy coding unit 4414 receives data, the entropy coding unit 4414 may perform one or more entropy coding operations to generate entropy coded data and output a bitstream including the entropy coded data.

[0374] Fig.52 is a block diagram showing an example of a video decoder 4500, which may be Fig.50 Video decoder 4324 in the system 4300 shown. Video decoder 4500 can be configured to perform any or all of the techniques of the present disclosure. In the example shown, video decoder 4500 includes multiple functional components. The techniques described in the present disclosure can be shared between the various components of video decoder 4500. In some examples, the processor can be configured to perform any or all of the techniques described in the present disclosure.

[0375] In the example shown, the video decoder 4500 includes an entropy decoding unit 4501, a motion compensation unit 4502, an intra-frame prediction unit 4503, an inverse quantization unit 4504, an inverse transform unit 4505, and a reconstruction unit 4506, a buffer area 4507. In some examples, the video decoder 4500 can perform a decoding process that is substantially the inverse of the encoding process described with respect to the video encoder 4400.

[0376] The entropy decoding unit 4501 may retrieve an encoded bitstream. The encoded bitstream may include entropy encoded video data (e.g., encoded video data blocks). The entropy decoding unit 4501 may decode the entropy encoded video data, and the motion compensation unit 4502 may determine motion information based on the entropy decoded video data, the motion information including motion vectors, motion vector precision, reference picture list index, and other motion information. The motion compensation unit 4502 may determine such information, for example, by performing AMVP and Merge modes.

[0377] The motion compensation unit 4502 may generate a motion compensated block, possibly performing interpolation based on an interpolation filter. The identification of the interpolation filter used with sub-pixel precision may be included in a syntax element.

[0378] The motion compensation unit 4502 may calculate interpolation of sub-integer pixels of a reference block using an interpolation filter used by the video encoder 4400 during encoding of the video block. The motion compensation unit 4502 may determine the interpolation filter used by the video encoder 4400 according to received syntax information and use the interpolation filter to generate a prediction block.

[0379] The motion compensation unit 4502 can use some syntax information to determine the size of blocks used to encode frames and / or slices of the encoded video sequence, partitioning information describing how each macroblock of the pictures of the encoded video sequence is partitioned, a mode indicating how each partition is encoded, one or more reference frames (and reference frame lists) for each inter-frame codec block, and other information used to decode the encoded video sequence.

[0380] The intra prediction unit 4503 may form a prediction block from spatially adjacent blocks using, for example, an intra prediction mode received in the bitstream. The inverse quantization unit 4504 inversely quantizes, i.e., dequantizes, the video block coefficients provided in the bitstream and decoded and quantized by the entropy decoding unit 4501. The inverse transform unit 4505 applies an inverse transform.

[0381] The reconstruction unit 4506 may add the residual block to the corresponding prediction block generated by the motion compensation unit 4502 or the intra prediction unit 4503 to form a decoded block. If necessary, a deblocking filter may also be applied to filter the decoded block to eliminate block artifacts. The decoded video block is then stored in a buffer 4507, which provides reference blocks for subsequent motion compensation / intra prediction and also generates decoded video for presentation on a display device.

[0382] Figure 2 4600 is a schematic diagram of an example encoder 4600. The encoder 4600 is suitable for implementing VVC technology. The encoder 4600 includes three loop filters, namely, a deblocking filter (DF) 4602, a sample adaptive offset (SAO) 4604, and an adaptive loop filter (ALF) 4606. Unlike the DF 4602 that uses a predefined filter, the SAO 4604 and the ALF 4606 utilize the original samples of the current picture to reduce the mean square error between the original samples and the reconstructed samples by adding an offset and applying a finite impulse response (FIR) filter, respectively, and using the codec's side information to signal the offset and filter coefficients. The ALF 4606 is located at the last processing stage of each picture and can be seen as a tool that attempts to capture and repair artifacts created by previous stages.

[0383] The encoder 4600 also includes an intra prediction component 4608 and a motion estimation / compensation (ME / MC) component 4610 configured to receive an input video. The intra prediction component 4608 is configured to perform intra prediction, while the ME / MC component 4610 is configured to perform inter prediction using a reference picture obtained from a reference picture buffer 4612. The residual block from the inter prediction or intra prediction is fed into a transform (T) component 4614 and a quantization (Q) component 4616 to generate quantized residual transform coefficients, which are fed into an entropy coding component 4618. The entropy coding component 4618 entropy codes the prediction result and the quantized transform coefficients and sends them to a video decoder (not shown). The quantized component output from the quantization component 4616 can be fed into an inverse quantization (IQ) component 4620, an inverse transform component 4622, and a reconstruction (REC) component 4624. The REC component 4624 is capable of outputting images to the DF 4602 , SAO 4604 , and ALF 4606 for filtering before these pictures are stored in the reference picture buffer 4612 .

[0384] Fig.53 4700 is a flow chart of an example method 4700 for video processing. The method 4700 includes applying an adaptive loop filter (ALF) to a first component of a video unit at step 4702. The ALF includes one or more extension taps. The one or more extension taps utilize input sources other than spatially adjacent samples of the first component. At step 4704, conversion between visual media data and a bitstream is performed based on the ALF. According to an example, the conversion of step 4704 can include encoding at an encoder or decoding at a decoder.

[0385] It should be noted that method 4700 may be implemented in an apparatus for processing video data, the apparatus comprising a processor and a non-transitory memory having instructions thereon, such as video encoder 4400, video decoder 4500, and / or encoder 4600. In this case, the instructions, when executed by the processor, cause the processor to perform method 4700. In addition, method 4700 may be performed by a non-transitory computer-readable medium including a computer program product for use by a video codec device. The computer program product includes computer executable instructions stored on a non-transitory computer-readable medium, such that when executed by a processor, the video codec device performs method 4700.

[0386] A list of solutions preferred by some examples is provided next.

[0387] The following solutions illustrate examples of the techniques discussed herein.

[0388] 1. A method for processing video data (e.g., Fig.49The method 4200 shown in FIG. 4 comprises: determining (4202) to apply an adaptive loop filter (ALF) to a video unit, the ALF comprising at least one extended tap; and performing (4204) conversion between visual media data and a bitstream based on the ALF.

[0389] 2. The method as described in solution 1, wherein the ALF further includes a spatial tap, and wherein the spatial tap uses information from spatially adjacent samples in adjacent video units.

[0390] 3. The method as described in any one of solutions 1 to 2, wherein the spatial domain neighboring samples are reconstructed samples obtained before the ALF is applied to the spatial domain neighboring samples.

[0391] 4. A method as described in any one of solutions 1 to 3, wherein the ALF includes M spatial domain taps and N extension taps, where N and M are greater than zero.

[0392] 5. A method as described in any one of solutions 1 to 4, wherein the expansion tap uses multiple input sources.

[0393] 6. A method as described in any of solutions 1 to 5, wherein the extended tap is only applied to the luma component.

[0394] 7. A method as in any one of solutions 1 to 6, wherein the extended tap is applied only to chroma components.

[0395] 8. A method as described in any one of solutions 1 to 7, wherein the extended tap corresponds to one or more input sample points, or wherein coefficients of the extended tap are shared by multiple inputs based on geometric information.

[0396] 9. A method as described in any one of solutions 1 to 8, wherein the ALF filter is trained by training data, and wherein the training data collection for the extension tap, the spatial domain tap or their parameters is performed jointly or independently.

[0397] 10. A method as described in any one of solutions 1 to 9, wherein the shape adopted by the ALF for the extension tap is different from the shape adopted for the spatial domain tap.

[0398] 11. The method of any one of solutions 1 to 10, wherein the ALF adopts a certain shape, and wherein the shape is a diamond, a square, a cross, a symmetrical shape, an asymmetrical shape or a combination thereof.

[0399] 12. A method as described in any of solutions 1 to 11, wherein the spatial taps have a filter size N, where N is 5, 7, 9, 11 or 13, and wherein the extended taps have a filter size M, where M is 1, 2, 5 or 7.

[0400] 13. A method as described in any of solutions 1 to 12, wherein a transposition based on geometric information is applied to the spatial domain tap or the extended tap.

[0401] 14. A method as described in any one of solutions 1 to 13, wherein the extended tap receives an input, and the input includes a reconstructed sample of the current frame before applying the ALF, an intermediate filtering result before applying the ALF, or a reconstructed sample before applying a deblocking filter.

[0402] 15. The method as described in any one of solutions 1 to 14, wherein the ALF is classified based on texture information, frequency band information, input of the spatial tap, input of the extension tap, gradient information, or a combination thereof.

[0403] 16. The method as described in any of solutions 1 to 15, wherein the application of the ALF is based on the classification of the ALF.

[0404] 17. The method as described in any one of solutions 1 to 16, wherein the input samples of the extended tap are padded at the video unit boundary.

[0405] 18. The method as described in any of solutions 1 to 17, wherein the bitstream includes a syntax element indicating the use of the ALF.

[0406] 19. The method as described in any of solutions 1 to 18, wherein one or more coefficients associated with the ALF are signaled in an adaptive parameter set (APS).

[0407] 20. A method as described in any of solutions 1 to 19, wherein the expansion tap receives the intermediate filtering result as input.

[0408] 21. A method as described in any one of solutions 1 to 20, wherein the expansion tap receives as input an output from a deblocking filter, a sample adaptive offset filter or a bidirectional filter.

[0409] 22. The method as described in any of solutions 1 to 21, wherein the expansion tap receives input samples from a reference frame.

[0410] 23. A method as described in any one of solutions 1 to 22, wherein the ALF is applied in a pre-processing stage, a post-processing stage, a loop filtering stage, or a combination thereof.

[0411] 24. An apparatus for processing video data, comprising: a processor; and a non-transitory memory having instructions thereon, wherein the instructions, when executed by the processor, cause the processor to perform a method as in any one of solutions 1 to 23.

[0412] 25. A non-transitory computer-readable medium, comprising a computer program product for use by a video codec device, the computer program product comprising computer executable instructions stored on the non-transitory computer-readable medium, so that when executed by a processor, the video codec device performs a method as described in any one of solutions 1 to 23.

[0413] 26. A non-transitory computer-readable recording medium storing a bitstream of a video generated by a method performed by a video processing device, wherein the method comprises: determining to apply an adaptive loop filter (ALF) to a video unit, the ALF comprising at least one extended tap; and generating the bitstream based on the determination.

[0414] 27. A method for storing a bitstream of a video, comprising: determining to apply an adaptive loop filter (ALF) to a video unit, the ALF comprising at least one extended tap; generating the bitstream based on the determination; and storing the bitstream in a non-transitory computer-readable recording medium.

[0415] 28. A method, apparatus or system as described in this patent document.

[0416] The following solutions illustrate examples of the techniques discussed herein.

[0417] 1. A method for processing video data, comprising: determining to apply an adaptive loop filter (ALF) to a first component of a video unit, the ALF comprising one or more extension taps, wherein the one or more extension taps use an input source other than spatially adjacent samples of the first component; and performing conversion between visual media data and a bitstream based on the ALF.

[0418] 2. The method as described in solution 1, wherein the ALF further includes spatial taps, which use spatially adjacent samples of components from the video unit reconstructed before applying the ALF.

[0419] 3. A method as described in any of solutions 1 to 2, wherein the one or more expansion taps receive input from components reconstructed by the video unit before applying a deblocking filter (DBF).

[0420] 4. A method as described in any of solutions 1 to 3, wherein the one or more expansion taps receive input from an intermediate result of the filter.

[0421] 5. A method as described in any one of solutions 1 to 4, wherein the first component is a luminance component, and the ALF including the one or more extended taps is only applied to filter the luminance component.

[0422] 6. A method as described in any of solutions 1 to 5, wherein each expansion tap employs one or more coefficients, and wherein each coefficient corresponds to N input samples, where N is 1 or 2.

[0423] 7. A method as described in any one of solutions 1 to 6, wherein the one or more extension taps and the spatial domain tap respectively adopt a certain shape, and wherein the shape of the extension tap is different from the shape of the spatial domain tap.

[0424] 8. A method as described in any one of solutions 1 to 7, wherein the shape of the spatial tap is a diamond, a cross or a symmetrical shape.

[0425] 9. A method as described in any one of solutions 1 to 8, wherein the shape of the spatial tap is a diamond with a height of nine samples and a width of nine samples.

[0426] 10. A method as described in any one of solutions 1 to 9, wherein the shape of the spatial tap is a combination of a cross with a height of thirteen samples and a width of thirteen samples and a square with a width of five samples and a height of five samples.

[0427] 11. The method as described in any one of solutions 1 to 10, wherein the shape of the extended tap is a diamond shape, a cross shape or a symmetrical shape.

[0428] 12. A method as described in any one of solutions 1 to 11, wherein the shape of the extended tap includes a single sample point, a cross with a height of three samples and a width of three samples, a cross with a height of five samples and a width of five samples, a diamond with a height of five samples and a width of five samples, or a combination thereof.

[0429] 13. A method as described in any of solutions 1 to 12, wherein a transposition based on geometric information is independently applied to one or more spatial domain taps and is independently applied to the one or more extension taps.

[0430] 14. A method as described in any of solutions 1 to 13, wherein the input source of the one or more extended taps includes an intermediate filtering result generated by reconstruction before the ALF is applied to the current frame and before the fixed filter ALF is applied.

[0431] 15. A method as described in any of solutions 1 to 14, wherein the input source of the one or more extended taps includes a reconstructed component before applying a deblocking filter (DBF), before applying a fixed filter ALF, before applying a predefined filter, or a combination thereof.

[0432] 16. A method as described in any of solutions 1 to 15, wherein padding is applied to input samples that are input to the one or more extension taps, and wherein the padding is applied to picture boundaries, sub-picture boundaries, slice boundaries, slice boundaries, codec tree unit (CTU) boundaries, codec tree block (CTB) boundaries, virtual boundaries, or a combination thereof, and wherein the padding includes mirror padding.

[0433] 17. A method as described in any one of solutions 1 to 16, wherein the bitstream includes a syntax element indicating whether at least one extended tap is enabled, wherein the syntax element is binarized according to a unary code, a truncated unary code, a fixed-length code, an exponential Golomb code, a truncated exponential Golomb code, or a combination thereof for encoding and decoding, and wherein the syntax element is included in a sequence parameter set (SPS), a picture parameter set (PPS), a picture header, a slice header, an adaptive parameter set (APS), a codec tree unit (CTU), a codec unit (CU), or a combination thereof.

[0434] 18. A method as described in any one of solutions 1 to 17, wherein the coefficients, limiting parameters and merging results of the one or more extended taps are included in an APS.

[0435] 19. A method as described in any one of solutions 1 to 18, wherein the input source of the one or more extended taps includes an intermediate filtering result of an offline trained ALF, an intermediate filtering result of a Gaussian filter, a reconstruction before applying DBF, a reconstruction after applying DBF, a reconstruction before applying ALF, a reconstruction after applying ALF, or a combination thereof.

[0436] 20. The method as described in any of solutions 1 to 19, wherein the ALF is a cross-component ALF (CCALF).

[0437] 21. A method as described in any one of solutions 1 to 20, wherein the spatial tap can use only spatially adjacent luminance samples to filter a central luminance sample inside an ALF filter, or wherein the spatial tap can use only spatially adjacent chrominance samples to filter a central chrominance sample inside an ALF filter, or wherein the ALF filter includes M spatial taps and N extended taps.

[0438] 22. A method as described in any one of solutions 1 to 21, wherein one or more extended taps of the ALF filter can use one or more input sources, or wherein one or more extended taps of the ALF filter can use multiple input sources, or wherein the input source of the extended tap can also be used by other taps in the ALF, or wherein the input source of the extended tap cannot be used by other taps in the ALF.

[0439] 23. A method as described in any one of solutions 1 to 22, wherein whether and / or how to apply a filter with at least one extended tap can be used differently when processing different color components, or wherein an ALF filter with at least one extended tap can be used to process only one of the chrominance components, or wherein an ALF filter with at least one extended tap can be used to process all chrominance components, or wherein an ALF filter with at least one extended tap can be applied to filter both luminance and chrominance components.

[0440] 24. A method as described in any one of solutions 1 to 23, wherein the coefficients of the extended taps inside the ALF filter can correspond to one or more input sample points, or wherein the coefficients of the extended taps inside the ALF filter can be shared by multiple inputs based on geometric information, or wherein the multiple input sample points are located at symmetrical positions.

[0441] 25. A method as described in any of solutions 1 to 24, wherein ALF filters with and without at least one extended tap are trained in different ways, or wherein training data collection for one or more extended taps of the ALF filter can be performed jointly with one or more spatial taps of the ALF filter, or wherein training data collection for one or more extended taps of the ALF filter can be performed independently, or wherein coefficients of one or more extended taps of the ALF filter can be jointly trained with one or more spatial taps of the ALF filter, or wherein coefficients of one or more extended taps of the ALF filter can be trained independently, or wherein parameters of one or more extended taps of the ALF filter can be derived jointly with one or more spatial taps of the ALF filter, or wherein parameters of one or more extended taps of the ALF filter can be derived independently.

[0442] 26. A method as described in any of Solutions 1 to 25, wherein ALF filters with and without at least one extended tap may use different shapes or sizes, or wherein within the ALF filter, the shape / size used for one or more spatial domain taps may be the same as the shape / size used for one or more extended taps, or wherein within the ALF filter with or without at least one extended tap, the filter shape used for one or more spatial domain taps may be a cross shape, an asymmetric shape, other designed shapes, or be determined / signaled / derived in real time.

[0443] 27. A method as described in any one of solutions 1 to 26, wherein the ALF filter comprising at least one spatial tap and at least one extension tap can be designed as follows, or wherein one or more spatial taps can be used for filtering, or wherein the shape of at least one spatial tap can be different shapes, or wherein the shape of at least one spatial tap can be a diamond, a cross, a square, a symmetrical shape or an asymmetrical shape, or wherein the filter size / length of the spatial tap can be N, where N=5, 7, 9, 11 or 13.

[0444] 28. A method as described in any of Solutions 1 to 27, wherein one or more extended taps can be applied to filtering, or wherein the filter shape of one or more extended taps can be a square or asymmetric shape, or wherein the filter size / length of the spatial domain tap can be N, where N = 1, 3, 5 or 7.

[0445] 29. A method as described in any one of solutions 1 to 28, wherein a transpose based on geometric information can be applied, or wherein the transpose based on geometric information can be jointly applied to one or more spatial taps and one or more extension taps, or wherein at least one extension tap can have one or more inputs, or wherein a possible input source of one or more extension taps can be the reconstruction before ALF is applied to the current frame, or wherein a possible input source of one or more extension taps can be the reconstruction before ALF is applied to the current frame and an intermediate filtering result generated by a predefined filter, or wherein the total number of extension taps inside the ALF filter can be jointly derived based on the shape, filter length, and symmetry constraints.

[0446] 30. A method as described in any one of solutions 1 to 29, wherein classification can be performed on an ALF filter having at least one extended tap, or classification can be performed on an ALF filter having at least one extended tap based on texture information, or the texture information can be generated by a gradient or a variance, or wherein classification can be performed on an ALF filter having at least one extended tap based on frequency band information, or the frequency band information can be generated by the intensity of one or more input samples, or the classification result can be independently generated based on the input of the spatial domain taps of the filter, or wherein the classification result can be independently generated based on the input of the extended taps of the filter, or wherein the classification result can be jointly generated based on the input of the spatial domain taps and the extended taps of the filter.

[0447] 31. A method as described in any of solutions 1 to 30, wherein whether and / or how to apply at least one extended tap in the ALF may depend on the classification in the ALF, or wherein the classification may be based on the gradient information of the input source, or wherein the input source may be a reconstruction before the ALF, or wherein the input source may be a reconstruction before the DBF, or wherein the input source may be the intermediate filtering result, or wherein the classification may be based on the frequency band information of the input source, or wherein the input source may be a reconstruction before the ALF, or wherein the input source may be a reconstruction before the DBF, or wherein the input source may be an intermediate filtering result.

[0448] 32. A method as described in any of solutions 1 to 31, wherein the input samples of the extended taps can be padded between picture / slice / slice / CTU boundaries, or wherein the padding can be applied to any boundary during the encoding / decoding process, or wherein the padding can be applied to CU / TU / PU boundaries, or wherein the padding can be applied to block boundaries, or wherein the padding can be applied to unit boundaries, or wherein the padding can be applied to any other type of boundary, or wherein different padding methods can be applied to boundaries, or wherein extended padding can be applied, or wherein repeated padding can be applied, or wherein other padding methods can be applied.

[0449] 33. A method as described in any one of solutions 1 to 32, wherein the first syntax element can be encoded and decoded by arithmetic coding, or wherein the first syntax element can be encoded and decoded using at least one context, or wherein the context can depend on coding information of the current block or a neighboring block, or wherein the context can depend on the filter shape of at least one neighboring block, or wherein the first syntax element can be encoded and decoded using bypass coding, or wherein the first syntax element can be conditionally signaled, or wherein the first syntax element is signaled only when the extension tap is available, or wherein the first syntax element can be encoded and decoded in a predictive manner, or wherein the first syntax element can be predicted by an on / off decision of an extension tap of at least one neighboring block, or wherein the first syntax element can be signaled independently for different color components, or wherein the first syntax element can be signaled and shared for different color components, or wherein the first syntax element can be signaled for the first color component but not for the second color component.

[0450] 34. A method as described in any of solutions 1 to 33, wherein at least one coefficient of one or more filters having at least one extended tap can be signaled in a syntax element structure, or wherein the coefficients of the extended taps can be encoded and decoded in a predictive manner, or wherein the coefficients of the extended taps can be encoded and decoded by arithmetic coding using at least one context, or wherein the coefficients of the extended taps can be encoded and decoded using bypass coding, or wherein the coefficients of the extended taps can be jointly encoded and decoded with coefficients of spatial domain taps, or wherein other parameters of the extended taps can be included in an APS, or wherein the coefficients of the extended taps can be predefined fixed values.

[0451] 35. A method as described in any one of solutions 1 to 34, wherein the intermediate filtering result of the filter is used as the input of one or more extension taps, or wherein the intermediate filtering result of the ALF filter trained online can be used as the input of one or more extension taps, or wherein the bilateral filter can be applied, or wherein the guided filter can be applied, or wherein the median filter can be applied, or wherein a filter with a low-pass property can be applied, or wherein a filter with a high-pass property can be applied, or wherein the intermediate filtering results of other filters trained online can be used as the input of one or more extension taps, or wherein the input of the intermediate filtering can be reconstructed samples at different encoding and decoding stages, or wherein the reconstruction before / after SAO / CCSAO of the current frame / reference frame can be used to generate the intermediate filtering result, or wherein the reconstruction before / after BIF of the current frame / reference frame can be used to generate the intermediate filtering result, or wherein the reconstruction before / after any other stage of the current / reference frame can be used to generate the intermediate filtering result.

[0452] 36. A method as described in any one of solutions 1 to 35, wherein the reconstructed sample point is used as an input to one or more extension taps before or after different encoding and decoding stages of the current frame, or wherein the reconstruction before / after SAO / CCSAO of the current frame can be used as an input to one or more extension taps, or wherein the reconstruction before / after BIF of the current frame can be used as an input to one or more extension taps, or wherein the reconstruction before / after other stages of the current frame can be used as an input to one or more extension taps.

[0453] 37. A method as described in any one of solutions 1 to 36, wherein whether and / or how to use the reconstructed samples before or after different encoding and decoding stages of the reference frame are used as the input of the extension tap, wherein the reconstruction before / after DBF of the reference frame can be used as the input of the extension tap, the reconstruction before / after DBF of one reference frame can be used as the input of the extension tap, or wherein the reconstruction before / after DBF of multiple reference frames can be used as the input of the extension tap, or wherein the reconstruction before / after SAO / CCSAO of the reference frame can be used as the input of the extension tap, or the reconstruction before / after SAO / CCSAO of one reference frame can be used as the input of the extension tap, Or the reconstruction before / after SAO / CCSAO of multiple reference frames can be used as input to the extension tap, or the reconstruction before / after BIF of the reference frame can be used as input to the extension tap, or the reconstruction before / after BIF of one of the reference frames can be used as input to the extension tap, or the reconstruction before / after BIF of multiple reference frames can be used as input to the extension tap, or the reconstruction before / after other stages of the reference frame can be used as input to the extension tap, or the reconstruction before / after other stages of one of the reference frames can be used as input to the extension tap, or the reconstruction before / after other stages of multiple reference frames can be used as input to the extension tap.

[0454] 38. The method according to any one of solutions 1 to 37, wherein one or more steps are used in combination or individually.

[0455] 39. A method as described in any one of Solutions 1 to 38, wherein the extended tap for the ALF method can be applied to any loop filtering tool, preprocessing or post-processing filtering method in the video codec, or wherein the proposed extended tap can be applied to the loop filtering method, or wherein the proposed extended tap method can be applied to ALF, CCALF or other loop filtering methods, or wherein the proposed extended tap method can be applied to a preprocessing filtering method, or wherein the proposed extended tap method can be applied to a post-processing filtering method.

[0456] 40. A method as described in any one of solutions 1 to 39, wherein the video unit may refer to a sequence / picture / sub-picture / slice / slice / codec tree unit (CTU) / CTU row / CTU group / codec unit (CU) / prediction unit (PU) / transform unit (TU) / codec tree block (CTB) / codec block (CB) / prediction block (PB) / transform block (TB) / any other area containing more than one luma or chroma sample / pixel.

[0457] 41. A method as described in any of solutions 1 to 40, wherein whether and / or how to apply the method disclosed above can be signaled in the bitstream, or wherein the signaling can be performed at the sequence level / picture group level / picture level / slice level / slice group level, such as signaling in the sequence header / picture header / SPS / VPS / DPS / DCI / PPS / APS / slice header / slice group header, or wherein the signaling can be performed in the PB / TB / CB / PU / TU / CU / VPDU / CTU / CTU row / slice / slice / sub-picture / other types of areas containing more than one sample or pixel.

[0458] 42. A method as described in any one of solutions 1 to 41, wherein whether and / or how to apply the method disclosed above may depend on codec information such as block size, color format, single / dual tree partitioning, color component, slice / picture type.

[0459] 43. A device for processing video data, comprising: a processor; and a non-volatile memory having instructions thereon, wherein the instructions, when executed by the processor, cause the processor to perform a method as in any one of solutions 1 to 42.

[0460] 44. A non-transitory computer-readable medium, comprising a computer program product for use by a video codec device, the computer program product comprising computer executable instructions stored on the non-transitory computer-readable medium, so that when executed by a processor, the video codec device performs a method as described in any one of solutions 1 to 42.

[0461] 45. A non-transitory computer-readable recording medium storing a bitstream of a video generated by a method performed by a video processing device, wherein the method comprises: determining to apply an adaptive loop filter (ALF) to a first component of a video unit, the ALF comprising one or more extension taps, wherein the one or more extension taps utilize an input source other than spatially adjacent samples of the first component; and generating the bitstream based on the determination.

[0462] 46. ​​A method for storing a bitstream of a video, comprising: determining to apply an adaptive loop filter (ALF) to a first component of a video unit, the ALF comprising one or more extension taps, wherein the one or more extension taps utilize an input source other than spatially adjacent samples of the first component; generating the bitstream based on the determination; and storing the bitstream in a non-transitory computer-readable recording medium.

[0463] In this document, the term "video processing" may refer to video encoding, video decoding, video compression, or video decompression. For example, a video compression algorithm may be applied during conversion from a pixel representation of a video to a corresponding bitstream representation (or vice versa). For example, the bitstream representation of a current video block may correspond to bits that are co-located or distributed at different locations in the bitstream, as defined by the syntax. For example, a macroblock may be encoded based on an error residual value of a transform and codec, and also encoded using bits in a header and other fields in the bitstream. In addition, during conversion, the decoder may parse the bitstream based on a determination, and it is known that certain fields may or may not exist, as described in the above solution. Similarly, the encoder may determine whether to include certain syntax fields, and generate the codec representation accordingly by including or excluding syntax fields in the codec representation.

[0464] The solutions, examples, embodiments, modules and functional operations described and disclosed herein and others can be implemented in digital electronic circuits or computer software, firmware or hardware or a combination of one or more thereof, which includes the structures disclosed in this document and their equivalents. The disclosed embodiments and other embodiments can be implemented as one or more computer program products encoded on a computer-readable medium that are executed by a data processing device or control the operation of the data processing device, that is, one or more modules of computer program instructions. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a material composition that affects a machine-readable propagation signal, or a combination of one or more thereof. The term "data processing device" covers all devices, devices and machines for processing data, including, for example, a programmable processor, a computer or multiple processors or computers. In addition to hardware, the device may also include code that creates an execution environment for the computer program in question, for example, code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more thereof. A propagation signal is an artificially generated signal, for example, a machine-generated electrical, optical or electromagnetic signal, which is generated to encode information for transmission to a suitable receiver device.

[0465] A computer program (also referred to as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or any other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program may be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files storing one or more modules, subroutines, or portions of code). A computer program may be deployed to execute on one computer or on multiple computers, which are located at one site or distributed across multiple sites and interconnected by a communication network.

[0466] The processes or logic flows described herein may be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows may also be performed by, and devices may also be implemented as, special purpose logic circuits, such as FPGAs (field programmable gate arrays) or ASICs (application specific integrated circuits).

[0467] Processors suitable for executing computer programs include, for example, both general-purpose microprocessors and special-purpose microprocessors and any one or more processors of any kind of digital computer. Typically, the processor will receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Typically, a computer will also include one or more mass storage devices for storing data, such as magnetic disks, magneto-optical disks, or optical disks, or be operably coupled to receive data from one or more mass storage devices or transfer data to one or more mass storage devices or both. However, a computer does not necessarily have such devices. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including, for example, semiconductor memory devices, such as erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and compact disc read-only memory (CD ROM) and digital versatile disc read-only memory (DVD-ROM) disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0468] Although this article includes many details, these details should not be interpreted as limitations on any subject matter or content that may be claimed, but should be interpreted as descriptions of features of specific embodiments that may be specific to a particular technology. Certain features described in this article in the context of separate embodiments may also be implemented in combination in a single embodiment. On the contrary, the individual features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any appropriate sub-combination. In addition, although the above may describe features as acting in certain combinations and even initially claiming protection, in some cases, one or more features from the claimed combination may be removed from the combination, and the claimed combination may involve a sub-combination or a deformation of a sub-combination.

[0469] Similarly, although operations are shown in a particular order in the figures, this should not be understood as requiring such operations to be performed in the particular order shown or in a sequential order or to perform all of the operations shown to achieve the desired results. In addition, the separation of various system components described herein should not be understood as requiring such separation in all embodiments.

[0470] Only a few implementations and examples are described herein, and other implementations, enhancements, and variations may be made based on what is described and illustrated herein.

[0471] A first component is directly coupled to a second component when there are no intermediate components other than a line, trace, or another medium between the first and second components. A first component is indirectly coupled to a second component when there are intermediate components other than a line, trace, or another medium between the first and second components. The term "coupled" and variations thereof include direct coupling and indirect coupling. Unless otherwise specified, the use of the term "about" is meant to include a range of ±10% of the subsequent value.

[0472] Although several embodiments are provided in the present disclosure, it should be understood that the disclosed systems and methods may be implemented in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are considered to be illustrative rather than restrictive and should not be limited to the details given herein. For example, various elements or components may be combined or integrated in another system, or certain features may be omitted or not implemented.

[0473] In addition, without departing from the scope of the present disclosure, the techniques, systems, subsystems and methods described and shown as discrete or separate in various embodiments may be combined or integrated with other systems, modules, techniques or methods. Other items shown or discussed as coupled may be directly connected, or may be indirectly coupled or communicated through some interface, device or intermediate component, whether electrically, mechanically or otherwise coupled or communicated. Other examples of changes, substitutions and alterations may be identified by those skilled in the art, and these changes, substitutions and alterations may be made without departing from the spirit and scope disclosed herein.

Claims

1. A method for processing video data, comprising: determining to apply an adaptive loop filter (ALF) to a first component of a video unit, the ALF comprising one or more extension taps, wherein the one or more extension taps use input sources other than spatially neighboring samples of the first component; as well as Conversion between visual media data and a bit stream is performed based on the ALF.

2. The method of claim 1, wherein the ALF further comprises spatial taps that use spatially neighboring samples from components of the video unit that were reconstructed prior to applying the ALF.

3. The method of any one of claims 1 to 2, wherein the one or more expansion taps receive input from components reconstructed by the video unit prior to application of a deblocking filter (DBF).

4. The method of any one of claims 1 to 3, wherein the one or more extension taps receive input from an intermediate result of a filter.

5. The method of any one of claims 1 to 4, wherein the first component is a luminance component, and the ALF in which the one or more extended taps are included is applied only to filter the luminance component.

6. The method of any one of claims 1 to 5, wherein each expansion tap employs one or more coefficients, and wherein each coefficient corresponds to N input samples, where N is 1 or 2.

7. The method according to any one of claims 1 to 6, wherein the one or more extension taps and the spatial domain tap each adopt a certain shape, and wherein the shape of the extension tap is different from the shape of the spatial domain tap.

8. The method according to any one of claims 1 to 7, wherein the shape of the spatial tap is a diamond shape, a cross shape or a symmetrical shape.

9. The method of any one of claims 1 to 8, wherein the shape of the spatial domain tap is a diamond with a height of nine samples and a width of nine samples.

10. The method of any one of claims 1 to 9, wherein the shape of the spatial domain tap is a combination of a cross having a height of thirteen samples and a width of thirteen samples and a square having a width of five samples and a height of five samples.

11. The method according to any one of claims 1 to 10, wherein the shape of the extended tap is a diamond shape, a cross shape or a symmetrical shape.

12. The method of any one of claims 1 to 11, wherein the shape of the extended tap comprises a single sample point, a cross with a height of three samples and a width of three samples, a cross with a height of five samples and a width of five samples, a diamond with a height of five samples and a width of five samples, or a combination thereof, and wherein the extended tap receives data from one or more input sources.

13. The method of any one of claims 1 to 12, wherein a transposition based on geometric information is independently applied to one or more spatial domain taps and is independently applied to the one or more extension taps.

14. The method of any one of claims 1 to 13, wherein the input source of the one or more extended taps comprises an intermediate filtering result reconstructed and generated before the ALF is applied to a current frame and before a fixed filter ALF is applied.

15. The method of any one of claims 1 to 14, wherein the input source of the one or more extended taps includes a reconstructed component before applying a deblocking filter (DBF), before applying a fixed filter ALF, before applying a predefined filter, or before a combination of the above conditions.

16. The method of any one of claims 1 to 15, wherein padding is applied to input samples as input to the one or more extension taps, and wherein the padding is applied to a picture boundary, a sub-picture boundary, a slice boundary, a slice boundary, a codec tree unit (CTU) boundary, a codec tree block (CTB) boundary, a virtual boundary, or a combination thereof, and wherein the padding comprises mirror padding.

17. The method according to any one of claims 1 to 16, wherein the bitstream includes a syntax element indicating whether at least one extended tap is enabled, wherein the syntax element is binarized according to a unary code, a truncated unary code, a fixed-length code, an exponential Golomb code, a truncated exponential Golomb code, or a combination thereof for encoding and decoding, and wherein the syntax element is included in a sequence parameter set (SPS), a picture parameter set (PPS), a picture header, a slice header, an adaptive parameter set (APS), a codec tree unit (CTU), a codec unit (CU), or a combination thereof.

18. The method of any one of claims 1 to 17, wherein coefficients of the one or more extended taps, limiting parameters and combining results are included in an APS.

19. The method of any one of claims 1 to 18, wherein the input source of the one or more extended taps comprises an intermediate filtering result of an offline trained ALF, an intermediate filtering result of a Gaussian filter, a reconstruction before applying DBF, a reconstruction after applying DBF, a reconstruction before applying ALF, a reconstruction after applying ALF, or a combination thereof.

20. The method of any one of claims 1 to 19, wherein the ALF is a cross-component ALF (CCALF).

21. The method of any one of claims 1 to 20, wherein the spatial taps use only spatially adjacent luminance samples to filter a central luminance sample within an ALF filter, or wherein the spatial taps use only spatially adjacent chrominance samples to filter a central chrominance sample within an ALF filter, or wherein the ALF filter comprises M spatial taps and N extended taps.

22. The method of any one of claims 1 to 21, wherein one or more extended taps of the ALF filter use one or more input sources, or wherein one or more extended taps of the ALF filter use multiple input sources, or wherein the input source of the extended tap can also be used by other taps in the ALF, or wherein the input source of the extended tap cannot be used by other taps in the ALF.

23. A method as described in any one of claims 1 to 22, wherein whether and / or how to apply a filter with at least one extended tap is used in different ways when processing different color components, or wherein the ALF filter with at least one extended tap is used only to process one of the chrominance components, or wherein the ALF filter with at least one extended tap is used to process all chrominance components, or wherein the ALF filter with at least one extended tap is applied to filter both luminance and chrominance components.

24. The method of any one of claims 1 to 23, wherein the coefficients of the extended taps inside the ALF filter can correspond to one or more input sample points, or wherein the coefficients of the extended taps inside the ALF filter are shared by multiple inputs based on geometric information, or wherein the multiple input sample points are located at symmetrical positions.

25. The method of any one of claims 1 to 24, wherein the ALF filter with and without at least one extended tap is trained in different ways, or wherein the training data collection of one or more extended taps of the ALF filter is performed jointly with one or more spatial taps of the ALF filter, or wherein the training data collection of one or more extended taps of the ALF filter is performed independently, or wherein the coefficients of one or more extended taps of the ALF filter are jointly trained with one or more spatial taps of the ALF filter, or wherein the coefficients of one or more extended taps of the ALF filter are trained independently, or wherein the parameters of one or more extended taps of the ALF filter are derived jointly with one or more spatial taps of the ALF filter, or wherein the parameters of one or more extended taps of the ALF filter are derived independently.

26. A method as described in any one of claims 1 to 25, wherein ALF filters with and without at least one extended tap use different shapes or sizes, or wherein within the ALF filter, the shape and / or size used for one or more spatial domain taps is the same as the shape and / or size used for one or more extended taps, or wherein within the ALF filter with or without at least one extended tap, the filter shape used for one or more spatial domain taps is a cross shape, an asymmetric shape, other designed shape, or is determined, signaled, or derived in real time.

27. The method of any one of claims 1 to 26, wherein: An ALF filter comprising at least one spatial tap and at least one extension tap is designed as follows, wherein one or more spatial taps are used for filtering, or wherein the shape of at least one spatial tap is a different shape, or wherein the shape of at least one spatial tap is a diamond, a cross, a square, a symmetrical shape or an asymmetrical shape, or wherein the filter size / length of the spatial tap is N, where N=5, 7, 9, 11 or 13.

28. A method as described in any one of claims 1 to 27, wherein one or more extended taps are used for filtering, or wherein the filter shape of one or more extended taps is a square or asymmetric shape, or wherein the filter size / length of the spatial domain taps is N, where N=1, 3, 5 or 7.

29. A method as described in any one of claims 1 to 28, wherein a transposition based on geometric information is applied, or wherein the transposition based on geometric information is jointly applied to one or more spatial domain taps and one or more extension taps, or wherein at least one extension tap has one or more inputs, or wherein a possible input source of one or more extension taps is a reconstruction before ALF is applied to the current frame, or wherein a possible input source of one or more extension taps is a reconstruction before ALF is applied to the current frame and an intermediate filtering result generated before a predefined filter is applied, or wherein the total number of extension taps inside the ALF filter is jointly derived based on the shape, filter length, and symmetry constraints.

30. A method as described in any one of claims 1 to 29, wherein an ALF filter having at least one extended tap is classified, or the ALF filter having at least one extended tap is classified based on texture information, or the texture information is generated by gradient or variance, or wherein the ALF filter having at least one extended tap is classified based on frequency band information, or the frequency band information is generated by the intensity of one or more input samples, or the classification result is independently generated based on the input of the spatial domain taps of the filter, or wherein the classification result is independently generated based on the input of the extended taps of the filter, or wherein the classification result is jointly generated based on the input of the spatial domain taps and the extended taps of the filter.

31. The method of any one of claims 1 to 30, wherein whether and / or how to apply at least one extended tap in the ALF depends on the classification of the ALF, or wherein the classification is based on gradient information of an input source, or wherein the input source is a reconstruction before the ALF, or wherein the input source is a reconstruction before the DBF, or wherein the input source is the intermediate filtering result, or wherein the classification is based on frequency band information of the input source, or wherein the input source is a reconstruction before the ALF, or wherein the input source is a reconstruction before the DBF, or wherein the input source is an intermediate filtering result.

32. The method of any one of claims 1 to 31, wherein the input samples of the extended taps are padded between picture / slice / slice / CTU boundaries, or wherein the padding is applied to any boundary during encoding and / or decoding, or wherein the padding is applied to CU / TU / PU boundaries, or wherein the padding is applied to block boundaries, or wherein the padding is applied to unit boundaries, or wherein the padding is applied to any other type of boundaries, or boundaries use different padding methods, or wherein extended padding is applied, or wherein repeated padding is applied, or wherein other padding methods are applied.

33. The method of any one of claims 1 to 32, wherein the first syntax element is encoded and decoded by arithmetic coding, or wherein the first syntax element is encoded and decoded using at least one context, or wherein the context depends on coding information of a current block or a neighboring block, or wherein the context depends on a filter shape of at least one neighboring block, or wherein the first syntax element is encoded and decoded using bypass coding, or wherein the first syntax element is conditionally signaled, or wherein the first syntax element is signaled only when the extension tap is available, or wherein the first syntax element is encoded and decoded in a predictive manner, or wherein the first syntax element is predicted by an on / off decision of an extension tap of at least one neighboring block, or wherein the first syntax element is signaled independently for different color components, or wherein the first syntax element is signaled and shared for different color components, or wherein the first syntax element is signaled for a first color component but not for a second color component.

34. The method of any one of claims 1 to 33, wherein: At least one coefficient of one or more filters having at least one extended tap is signaled in a syntax element structure, or wherein the coefficient of the extended tap is encoded and decoded in a predictive manner, or wherein the coefficient of the extended tap is encoded and decoded using at least one context by arithmetic coding and decoding, or wherein the coefficient of the extended tap is encoded and decoded using bypass coding and decoding, or wherein the coefficient of the extended tap is jointly encoded and decoded with the coefficient of the spatial domain tap, or wherein other parameters of the extended tap are included in the APS, or wherein the coefficient of the extended tap is a predefined fixed value.

35. A method as described in any one of claims 1 to 34, wherein the intermediate filtering result of the filter is used as an input to one or more extension taps, or wherein the intermediate filtering result of the ALF filter trained online is used as an input to one or more extension taps, or wherein a bilateral filter is applied, or wherein a guided filter is applied, or wherein a median filter is applied, or wherein a filter with a low-pass property is applied, or wherein a filter with a high-pass property is applied, or wherein the intermediate filtering results of other filters trained online are used as input to one or more extension taps, or wherein the input of the intermediate filtering is a reconstructed sample at a different encoding and decoding stage, or wherein the reconstruction before / after SAO / CCSAO of the current frame / reference frame is used to generate the intermediate filtering result, or wherein the reconstruction before / after BIF of the current frame / reference frame is used to generate the intermediate filtering result, or wherein the reconstruction before / after any other stage of the current frame / reference frame is used to generate the intermediate filtering result.

36. A method as described in any one of claims 1 to 35, wherein the reconstructed samples before or after different encoding and decoding stages of the current frame are used as input to one or more extension taps, or wherein the reconstruction before / after SAO / CCSAO of the current frame is used as input to one or more extension taps, or wherein the reconstruction before / after BIF of the current frame is used as input to one or more extension taps, or wherein the reconstruction before / after other stages of the current frame is used as input to one or more extension taps.

37. A method as claimed in any one of claims 1 to 36, wherein whether and / or how the reconstructed samples before or after different coding stages of a reference frame are used as input to an extension tap, wherein the reconstruction before / after a DBF of a reference frame is used as input to an extension tap, or wherein, The reconstruction before / after the DBF of one reference frame is used as the input of the extension tap, or wherein the reconstruction before / after the DBF of multiple reference frames is used as the input of the extension tap, or wherein the reconstruction before / after the SAO / CCSAO of a reference frame is used as the input of the extension tap, or wherein the reconstruction before / after the SAO / CCSAO of one reference frame is used as the input of the extension tap, or wherein the reconstruction before / after the SAO / CCSAO of multiple reference frames is used as the input of the extension tap, or wherein the BIF of the reference frame The reconstruction before / after is used as the input of the expansion tap, or wherein the reconstruction before / after the BIF of a reference frame is used as the input of the expansion tap, or wherein the reconstruction before / after the BIF of multiple reference frames is used as the input of the expansion tap, or wherein the reconstruction before / after other stages of the reference frame is used as the input of the expansion tap, or wherein the reconstruction before / after other stages of a reference frame is used as the input of the expansion tap, or wherein the reconstruction before / after other stages of multiple reference frames is used as the input of the expansion tap.

38. The method of any one of claims 1 to 37, wherein one or more steps are used in combination or alone.

39. A method as described in any one of claims 1 to 38, wherein the extended tap for the ALF method is applied to any loop filtering tool, preprocessing or post-processing filtering method in the video codec, or wherein the extended tap is applied to the loop filtering method, or wherein the extended tap method is applied to ALF, CCALF or other loop filtering methods, or wherein the extended tap method is applied to the preprocessing filtering method, or wherein the extended tap method is applied to the post-processing filtering method.

40. The method of any one of claims 1 to 39, wherein the video unit refers to a sequence / picture / sub-picture / slice / slice / codec tree unit (CTU) / CTU row / CTU group / codec unit (CU) / prediction unit (PU) / transform unit (TU) / codec tree block (CTB) / codec block (CB) / prediction block (PB) / transform block (TB) / any other area including more than one luma or chroma sample / pixel.

41. The method of any one of claims 1 to 40, wherein whether and / or how to apply the method is signaled in the bitstream, or wherein the signaling is performed at the sequence level / picture group level / picture level / slice level / slice group level, such as signaled in a sequence header / picture header / SPS / VPS / DPS / DCI / PPS / APS / slice header / slice group header, or wherein the signaling is performed in a PB / TB / CB / PU / TU / CU / VPDU / CTU / CTU row / slice / slice / sub-picture / other type of region including more than one sample or pixel.

42. The method of any one of claims 1 to 41, wherein whether and / or how the method is applied depends on codec information, such as block size, color format, single / dual tree partitioning, color component, slice / picture type.

43. An apparatus for processing video data, comprising: processor; and a non-transitory memory storing instructions, wherein the instructions, when executed by the processor, cause the processor to perform the method of any one of claims 1 to 42.

44. A non-transitory computer-readable medium, comprising a computer program product for use by a video codec device, the computer program product comprising computer executable instructions stored on the non-transitory computer-readable medium, so that when executed by a processor, the video codec device performs the method as described in any one of claims 1 to 42.

45. A non-transitory computer-readable recording medium storing a bit stream of a video generated by a method performed by a video processing device, wherein the method comprises: determining to apply an adaptive loop filter (ALF) to a first component of a video unit, the ALF comprising one or more extension taps, wherein the one or more extension taps use input sources other than spatially neighboring samples of the first component; as well as The bitstream is generated based on the determination.

46. ​​A method for storing a bitstream of a video, comprising: determining to apply an adaptive loop filter (ALF) to a first component of a video unit, the ALF comprising one or more extension taps, wherein the one or more extension taps use input sources other than spatially neighboring samples of the first component; generating the bitstream based on the determination; as well as The bit stream is stored in a non-transitory computer-readable recording medium.

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