Filter shape switching for adaptive loop filters in video coding

Abstract

A mechanism for processing video data is disclosed. The filter is applied to a video unit. The filter employs an extended tap for a first sample point in the video unit and a spatial tap for a second sample point in the video unit. A conversion between visual media data and a bitstream is performed based on a video unit.

Description

[0001] Cross-references

[0002] This application claims priority to and the benefit of International Patent Application No. PCT / CN2022 / 090923 filed on May 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 a filter to a video unit, wherein the filter uses an extended tap for a first sample point in the video unit and a spatial tap for a second sample point in the video unit; and performing conversion between visual media data and a bitstream based on the video unit.

[0006] A second aspect relates to a device for processing video data, comprising: one or more processors; and one or more non-temporary memories, which are coupled to the one or more processors and store instructions, which when executed by the one or more processors, configure the device to: determine to apply a filter to a video unit, wherein the filter uses an extended tap for a first sample point in the video unit and a spatial tap for a second sample point in the video unit; and perform conversion between visual media data and a bitstream based on the video unit.

[0007] A third aspect relates to a non-transitory computer-readable medium, comprising a computer program product for use in a video codec device, the computer program product comprising computer executable instructions stored on the non-transitory computer-readable medium, the computer executable instructions, when executed by one or more processors, causing the video codec device to be configured to: determine to apply a filter to a video unit, wherein the filter uses an extended tap for a first sample point in the video unit and a spatial tap for a second sample point in the video unit; and perform conversion between visual media data and a bitstream based on the video unit.

[0008] A fourth aspect relates to a non-temporary 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 a filter to a video unit, wherein the filter uses an extended tap for a first sample point in the video unit and a spatial tap for a second sample point in the video unit; and generating the bitstream based on the determination.

[0009] 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.

[0010] 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

[0011] 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.

[0012] Figure 1 An example of nominal vertical and horizontal positions of 4:2:2 luma and chroma samples in a picture is shown.

[0013] Figure 2 An example encoder block diagram is shown.

[0014] Figure 3 An example picture divided into raster scan strips is shown.

[0015] Figure 4 An example picture divided into rectangular scan strips is shown.

[0016] Figure 5 An example picture divided into bricks is shown.

[0017] Figure 6 An example of a codec tree block (CTB) crossing a picture boundary is shown.

[0018] Figure 7 An example of an intra prediction mode is shown.

[0019] Figure 8 Examples of block boundaries in a picture are shown.

[0020] Fig. 9 An example of pixels involved in filter usage is shown.

[0021] Fig.10 An example of a filter shape for an ALF is shown.

[0022] Fig.11An example of transform coefficients supported by a 5×5 diamond filter is shown.

[0023] Fig.12 An example of relative coordinates supported by a 5×5 diamond filter is shown.

[0024] Fig.13 Example filter shapes for one or more spatial taps within a filter having at least one extension tap are shown.

[0025] Fig.14 An example filter including both spatial taps and extension taps is shown.

[0026] Fig.15 An example filter including both spatial taps and extension taps is shown.

[0027] Fig.16 An example filter including both spatial taps and extension taps is shown.

[0028] Fig.17 An example filter including both spatial taps and extension taps is shown.

[0029] Fig.18 An example filter including both spatial taps and extension taps is shown.

[0030] Fig.19 An example filter including both spatial taps and extension taps is shown.

[0031] Fig. 20 An example filter including both spatial taps and extension taps is shown.

[0032] Fig.21 An example filter including both spatial taps and extension taps is shown.

[0033] Fig. 22 An example filter including both spatial taps and extension taps is shown.

[0034] Fig.23 An example filter including both spatial taps and extension taps is shown.

[0035] Fig.24 An example filter including both spatial taps and extension taps is shown.

[0036] Fig.25 An example filter including both spatial taps and extension taps is shown.

[0037] Fig.26 An example of a filter shape candidate without extended taps is shown.

[0038] Fig. 27 An example of a filter shape candidate without extended taps is shown.

[0039] Fig.28 is a block diagram illustrating an example video processing system.

[0040] Fig.29 is a block diagram of an example video processing device.

[0041] Fig.30 is a flow chart of an example method for video processing.

[0042] Fig.31 is a block diagram illustrating an example video codec system.

[0043] Fig.32 is a block diagram illustrating an example encoder.

[0044] Fig.33 is a block diagram illustrating an example decoder.

[0045] Fig.34 is a schematic diagram of an example encoder.

[0046] Fig.35 is a flow chart of another example method of video processing. DETAILED DESCRIPTION

[0047] First, it should be understood that although the following provides an illustrative implementation of one or more embodiments, 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.

[0048] 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.

[0049] 1. Preliminary Discussion

[0050] 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.

[0051] 2. Abbreviations

[0052] 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).

[0053] 3. Video Codec Standards

[0054] 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.

[0055] The Video Coding Experts Group (VCEG) of the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) and the Moving Picture Experts Group (MPEG) 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) 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 additional extensions to VVC or a completely 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.

[0056] 3.1 Color Space and Chroma Subsampling

[0057] 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 luminance, blue-difference chrominance, and red-difference chrominance (YCbCr) and red, green, blue (RGB).

[0058] 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.

[0059] Chroma subsampling is the practice of encoding an image at a lower resolution than luminance information by taking advantage of the fact that the human visual system is less sensitive to color differences than to luminance. 3.1.1 4:4:4

[0061] 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

[0063] 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

[0065] 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 because 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 by a factor of two in both the horizontal and vertical directions. There are three variants of the 4:2:0 scheme, each with different horizontal and vertical addressing. In MPEG-2, Cb and Cr are co-located in the horizontal direction. Cb and Cr are located between pixels in the vertical direction (i.e., in the gap). In the 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 brightness samples. In 4:2:0DV, Cb and Cr are co-located in the horizontal direction. In the vertical direction, they are located on alternate lines.

[0066] chroma_format_idc separate_colour_plane_flag Chroma Format SubWidthC SubHeightC 0 0 monochrome 1 1 1 0 4:2:0 2 2 2 0 4:2:2 2 1 3 0 4:4:4 1 1 3 1 4:4:4 1 1

[0067] Table 1. SubWidthC and SubHeightC values ​​derived from chroma_format_idc and Separate_colour_plane_flag

[0068] 3.2 Example encoding process of video codec

[0069] Figure 2 An example of an encoder block diagram for 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 by 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.

[0070] 3.3 Definition of Video / Codec Unit

[0071] 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.

[0072] 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 of a raster scan striping partitioning of a picture is shown, where the picture is divided into 12 slices and 3 raster scan strips.

[0073] Figure 4 An example of rectangular strip partitioning of a picture is shown, where the picture is partitioned into 24 slices (6 slice columns and 4 slice rows) and 9 rectangular strips.

[0074] Figure 5 An example of a picture being divided into slices, bricks, and rectangular strips is shown, where the picture 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.

[0075] 3.3.1 CTU / CTB size

[0076] 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.

[0077] 7.3.2.3 Sequence parameter set RBSP syntax

[0078]

[0079]

[0080]

[0081] 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:

[0082] CtbLog2SizeY=log2_ctu_size_minus2+2(7-9)

[0083] CtbSizeY=1< <CtbLog2SizeY(7-10)

[0084] MinCbLog2SizeY=log2_min_luma_coding_block_size_minus2+2(7-11)

[0085] MinCbSizeY=1< <MinCbLog2SizeY(7-12)

[0086] MinTbLog2SizeY=2(7-13)

[0087] MaxTbLog2SizeY = 6(7 - 14)

[0088] MinTbSizeY = 1 << MinTbLog2SizeY(7 - 15)

[0089] MaxTbSizeY = 1 << MaxTbLog2SizeY(7 - 16)

[0090] PicWidthInCtbsY = Ceil(pic_width_in_luma_samples ÷ CtbSizeY)(7 - 17)

[0091] PicHeightInCtbsY = Ceil(pic_height_in_luma_samples ÷ CtbSizeY)(7 - 18)

[0092] PicSizeInCtbsY = PicWidthInCtbsY * PicHeightInCtbsY(7 - 19)

[0093] PicWidthInMinCbsY = pic_width_in_luma_samples / MinCbSizeY(7 - 20)

[0094] PicHeightInMinCbsY = pic_height_in_luma_samples / MinCbSizeY(7 - 21)

[0095] PicSizeInMinCbsY = PicWidthInMinCbsY * PicHeightInMinCbsY(7 - 22)

[0096] PicSizeInSamplesY = pic_width_in_luma_samples * pic_height_in_luma_samples(7 - 23)

[0097] PicWidthInSamplesC = pic_width_in_luma_samples / SubWidthC(7 - 24)

[0098] PicHeightInSamplesC = pic_height_in_luma_samples / SubHeightC(7 - 25)

[0099] 3.3.2 CTUs in a Picture

[0100] Assume that the CTB / largest coding unit (LCU) size is represented by MxN (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 Figure 6 those CTBs shown in

[0101] 3.4 Intra prediction

[0102] 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 Additional directional modes are shown, and the planar and DC modes remain unchanged. These denser directional intra prediction modes apply to all block sizes as well as luminance and chrominance intra prediction.

[0103] 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 the same, e.g., 67, and the intra mode coding remains unchanged.

[0104] In HEVC, each intra-coded block has a square shape, and the length of each side of the block is a power of 2. Thus, no division operation is required to generate an intra predictor using the DC mode. In VVC, a block 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 a non-square block.

[0105] 3.5 Inter prediction

[0106] For each inter-predicted CU, the motion parameters include motion vector, reference picture index, reference picture list usage index, and new coding features for VVC for additional information for sample generation for inter-prediction. Motion parameters can be signaled explicitly or implicitly. When a CU is encoded using skip mode, the CU is associated with one PU and has no significant residual coefficients, no encoded 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 additional 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.

[0107] 3.6 Deblocking Filter

[0108] 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 the application of multiple horizontal filtering or vertical filtering processes in parallel threads. The filtering process can also be implemented CTB by CTB, and the processing delay is very small.

[0109] 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.

[0110] 3.6.1 Boundary Decision

[0111] The filtering is applied at 8×8 block boundaries. Figure 8 The picture samples and horizontal and vertical block boundaries are shown on an 8×8 grid. Figure 8 In FIG. 1 , non-overlapping blocks of 8×8 samples are also shown, which can be deblocked in parallel. In addition, such boundaries must be transform block boundaries or coding subblock boundaries, for example due to the use of affine motion prediction (ATMVP). For other boundaries, deblocking filtering is disabled.

[0112] 3.6.2 Boundary strength calculation

[0113] 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.

[0114]

[0115] Table 2 Boundary Strength (When SPS IBC is disabled)

[0116]

[0117] Table 3 Boundary Strength (When SPS IBC is Enabled)

[0118] 3.6.3 Deblocking Decision for Luminance Component

[0119] The wider-stronger luminance filter is a filter that is 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 the variables bSidePisLargeBlk and bSideQisLargeBlk, respectively. bSidePisLargeBlk and bSideQisLargeBlk are defined as follows.

[0120] 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

[0121] 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

[0122] Based on bSidePisLargeBlk and bSideQisLargeBlk, condition 1 is defined as follows:

[0123] Condition 1 = (bSidePisLargeBlk || bSidePisLargeBlk)? True: False

[0124] Next, if condition 1 is true, we further check condition 2. First, we derive the following variables:

[0125] First, derive dp0, dp3, dq0, dq3 according to the HEVC method

[0126] if (side p is greater than or equal to 32)

[0127] dp0=(dp0+Abs(p50-2*p40+p30)+1)>>1

[0128] dp3=(dp3+Abs(p53-2*p43+p33)+1)>>1

[0129] if (q side is greater than or equal to 32)

[0130] dq0=(dq0+Abs(q50-2*q40+q30)+1)>>1

[0131] dq3=(dq3+Abs(q53-2*q43+q33)+1)>>1

[0132] Condition 2 = (d < β)? True: False

[0133] Where d=dp0+dq0+dp3+dq3.

[0134] If conditions 1 and 2 are valid, then further check if any of the blocks use sub-blocks:

[0135]

[0136] Finally, if both conditions 1 and 2 are valid, the proposed 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:

[0137] Derive dpq in the same way as HEVC.

[0138] Derived according to HEVC method sp3 = Abs (p3-p0)

[0139] if (side p is greater than or equal to 32)

[0140] if(Sp==5)

[0141] sp3=(sp3+Abs(p5-p3)+1)>>1

[0142] else

[0143] sp3=(sp3+Abs(p7-p3)+1)>>1

[0144] According to the HEVC method, sq3 = Abs (q0-q3) is derived

[0145] if (q side is greater than or equal to 32)

[0146] If(Sq==5)

[0147] sq3=(sq3+Abs(q5-q3)+1)>>1

[0148] else

[0149] sq3=(sq3+Abs(q7-q3)+1)>>1

[0150] 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

[0151] 3.6.4 Stronger Luminance Deblocking Filter

[0152] 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:

[0153] p i ′=(f i *Middle s,t +(64-f i )*P s +32)>>6),clippedtop i ±tcPD i

[0154] q j ′=(g j *Middle s,t +(64-g j )*Q s +32)>>6),clippedtoq j ±tcPD j

[0155] where tcPD i and tcPD j The term is the position-dependent clipping described above, and g j 、fi i 、Middle s,t , P s and Q s Given below.

[0156] 3.6.5 Chroma Deblocking Decision

[0157] 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 satisfies the following three conditions: The first decision is the decision of boundary strength and large blocks. The proposed 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.

[0158] 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.

[0159] Under the second condition, d is derived according to HEVC luminance deblocking. When d is less than β, the second condition will be true. Under the third condition, StrongFilterCondition is derived as follows:

[0160] Derive dpq in the same way as HEVC.

[0161] Derived according to HEVC method sp3 = Abs (p3-p0)

[0162] According to the HEVC method, sq3 = Abs (q0-q3) is derived

[0163] 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)

[0164] 3.6.6 Strong Deblocking Filter for Chroma

[0165] Define the following strong deblocking filter for chroma:

[0166] p2′=(3*p3+2*p2+p1+p0+q0+4)>>3

[0167] p1′=(2*p3+p2+2*p1+p0+q0+q1+4)>>3

[0168] p0′=(p3+p2+p1+2*p0+q0+q1+q2+4)>>3

[0169] The example chroma filter performs deblocking on a 4x4 grid of chroma samples.

[0170] 3.6.7 Position-dependent limiting

[0171] Position dependent clipping tcPD is applied to the output samples of the luminance filtering process, involving strong and long filters that modify 7, 5 and 3 samples at the boundaries. Assuming a quantization error distribution, it is proposed to increase the clipping value for samples that are expected to have higher quantization noise and therefore the reconstructed sample values ​​are expected to deviate more from the true sample values.

[0172] 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:

[0173] Tc7={6,5,4,3,2,1,1}; Tc3={6,4,2};

[0174] tcPD=(Sp==3)? Tc3:Tc7;

[0175] tcQD=(Sq==3)? Tc3:Tc7;

[0176] For P or Q boundaries filtered with a short symmetric filter, a lower magnitude position-dependent threshold is applied:

[0177] Tc3 = {3, 2, 1};

[0178] After defining the thresholds, the filtered p'i and q'i sample values ​​are clipped according to the tcP and tcQ clipping values:

[0179] p”i=Clip3(p’i+tcPi,p’i–tcPi,p’i);

[0180] q”j=Clip3(q’j+tcQj,q’j–tcQj,q’j);

[0181] 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.

[0182] 3.6.7 Sub-block deblocking adjustment

[0183] In order 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.

[0184] The following applies to sub-block boundaries that are not aligned with CU boundaries.

[0185]

[0186]

[0187] 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.

[0188] 3.7 Sample Adaptive Offset

[0189] 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.

[0190] 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

[0191] Table 4 SAO type regulations

[0192] 3.7 Adaptive Loop Filter

[0193] 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.

[0194] 3.8.1 Signaling of parameters

[0195] 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.

[0196] 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 APSID 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.

[0197] The ALF data syntax elements associated with the LUMA component in the VTM are listed below:

[0198]

[0199]

[0200] 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.

[0201] 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:

[0202] If alf_luma_coeff_sign[sfIdx][j] is equal to 0, the corresponding luma filter coefficient has a positive value.

[0203] Otherwise (alf_luma_coeff_sign[sfIdx][j] is equal to 1), the corresponding luma filter coefficient has a negative value.

[0204] When alf_luma_coeff_sign[sfIdx][j] is not present, it is inferred to be equal to 0.

[0205] 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:

[0206]

[0207]

[0208] 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).

[0209] 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.

[0210] The variable AlfCtbFiltSetIdxY[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] specifies the filter set index of the luma CTB at position (xCtb, yCtb) derived as follows:

[0211] If alf_use_aps_flag is equal to 0, AlfCtbFiltSetIdxY[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is set equal to alf_luma_fixed_filter_idx.

[0212] Otherwise, AlfCtbFiltSetIdxY[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is set equal to 16+alf_luma_prev_filter_idx.

[0213] 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).

[0214] 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:

[0215]

[0216] 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.

[0217] 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.

[0218] 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:

[0219] If alf_luma_coeff_sign[altIdx][sfIdx][j] is equal to 0, the corresponding luma filter coefficient has a positive value.

[0220] Otherwise (alf_luma_coeff_sign[altIdx][sfIdx][j] is equal to 1), the corresponding luma filter coefficient has a negative value.

[0221] When alf_luma_coeff_sign[altIdx][sfIdx][j] is not present, it is inferred to be equal to 0.

[0222] 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:

[0223]

[0224]

[0225] 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.

[0226] 3.8.2 Filter Shape

[0227] 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.

[0228] 3.8.3 Classification of ALF

[0229] 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:

[0230]

[0231] To calculate D and First, use the 1-dimensional Laplacian operator to calculate the gradient in the horizontal, vertical and two diagonal directions:

[0232]

[0233] 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:

[0234]

[0235] And the maximum and minimum values ​​of the gradients in the two diagonal directions are set to:

[0236]

[0237] To derive the value of the directionality D, these values ​​are compared with each other and with two thresholds t1 and t2:

[0238] Step 1. If and If both are true, D is set to 0.

[0239] Step 2. If Then continue from step 3; otherwise continue from step 4;

[0240] Step 3. If If yes, set D to 2; otherwise, set D to 1.

[0241] Step 4. If Then set D to 4; otherwise, set D to 3.

[0242] The activity value A is calculated as:

[0243]

[0244] 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.

[0245] 3.8.3 Geometric Transformation of Filter Coefficients

[0246] 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.

[0247] Introduce three geometric transformations, including diagonal transformation, vertical flip and rotation:

[0248] Diagonal: f D (k,l)=f(l,k),

[0249] Flip vertically: f V (k,l)=f(k,Kl-1),

[0250] Rotation: f R (k,l)=f(Kl-1,k).

[0251] 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 The transform coefficients for each position based on a 5x5 diamond are shown.

[0252]

[0253]

[0254] Table 5. Gradient maps and transformations computed for a block.

[0255] 3.8.3 Filtering process

[0256] 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.

[0257]

[0258] 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.

[0259] 3.8.3 Nonlinear Filter Reproduction

[0260] Linear filtering can be recast as follows without sacrificing coding efficiency:

[0261]

[0262] where w(i,j) are the same filter coefficients.

[0263] 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:

[0264]

[0265] 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).

[0266] 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.

[0267] 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:

[0268] Where M = 2 10 And N = 4

[0269] Similarly, the chromaticity table of the clipped value can be obtained according to the following formula:

[0270] Where M = 2 10 , N=4 and A=4

[0271] 3.9 Bilateral Loop Filter

[0272] 3.9.1 Bilateral Image Filter

[0273] 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

[0274]

[0275] where Δx and Δy are the vertical and horizontal distances, and ΔI is the intensity difference between the sample points.

[0276] 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.

[0277] 3.9.2 Bilateral Filters in Video Codecs

[0278] 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

[0279]

[0280] 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.

[0281] 4. Technical problems solved by the disclosed technical solutions

[0282] The example designs of adaptive loop filters in video codec systems have the following problems. First, in some example ALF designs, only spatially reconstructed samples before ALF processing are used for filter training and filtering. However, other valuable information, such as samples before DBF, SAO or other stages, can be used. Second, in some example ALF designs, filters trained online or filters trained offline use a single filter shape. The performance of ALF can be further improved by using filter shape switching and / or by adopting extended taps and spatial taps.

[0283] 5. List of solutions and implementation examples

[0284] 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.

[0285] Example 1

[0286] In one example, at least one extended tap may be used for the ALF to further enhance the efficiency of the ALF.

[0287] Example 2

[0288] In one example, at least one extended tap may be different from the spatial taps in the ALF, which utilizes only the information of spatially adjacent samples of the filtered component (e.g., only spatially adjacent luminance samples are used to filter the central luminance samples inside a filter). In one example, at least one extended tap and at least one spatial tap may coexist inside an ALF filter. In one example, the ALF filter may include both spatial taps and extended taps. In one example, the ALF filter may include M (e.g., M>0) spatial taps and N (e.g., N>0) extended taps. Alternatively, the ALF filter may include only one or more spatial taps. Alternatively, the ALF filter may include only one or more extended taps.

[0289] Example 3

[0290] In one example, a filter with at least one extended tap may be applied to filter different color components. In one example, a filter with at least one extended tap may be applied only to filter the luma component. Alternatively, a filter with at least one extended tap may be applied only to filter one of the chroma components (e.g., Cb or Cr components). Alternatively, a filter with at least one extended tap may be applied to filter two chroma components (e.g., Cb and Cr components). Alternatively, a filter with at least one extended tap may be applied to filter all luma components and chroma components.

[0291] Example 4

[0292] In one example, the coefficients of the extended taps may correspond to one or more inputs. In one example, the coefficients of the extended taps may correspond to only one input. Alternatively, the coefficients of the extended taps may correspond to N inputs (eg, N=2).

[0293] Example 5

[0294] In one example, a filter having at least one extended tap can be trained in different ways. In one example, the training data collection of one or more extended taps of the filter can be performed jointly with one or more spatial taps of the filter. Alternatively, the training data collection of one or more extended taps of the filter can be performed independently. In one example, the coefficients of one or more extended taps of the filter can be jointly trained with one or more spatial taps of the filter. Alternatively, the coefficients of one or more extended taps of the filter can be trained independently. In one example, the parameters of one or more extended taps of the filter (e.g., nonlinear clipping parameters) can be jointly derived with one or more spatial taps of the filter. Alternatively, the parameters of one or more extended taps of the filter (e.g., nonlinear clipping parameters) can be derived independently.

[0295] Example 6

[0296] In one example, a filter having at least one extended tap may use different shapes or sizes. In one example, the filter may include one or more shapes corresponding to different types of taps (e.g., a shape for one or more spatial taps and a shape for one or more extended taps). In one example, inside the filter, the shape for one or more spatial taps may be different from the shape for one or more extended taps. Alternatively, inside the filter, the shape for one or more spatial taps may be the same as the shape for one or more extended taps. In one example, inside the filter, the filter shapes for one or more spatial taps may use different shapes. In one example, the filter shape for one or more spatial taps may use a diamond shape. In one example, the filter shape for one or more spatial taps may use a square shape. In one example, the filter shape for one or more spatial taps may use a cross shape. Alternatively, the filter shape for one or more spatial taps may use a symmetrical shape. Alternatively, the filter shape for one or more spatial taps may use an asymmetrical shape. Alternatively, the filter shape for one or more spatial taps may use any other shape. In one example, it may be as Fig.13 Designing a filter shape for one or more spatial taps In one example, the filter shape for one or more spatial taps can be determined, signaled, or derived on the fly.

[0297] Example 7

[0298] In one example, inside the filter, the filter shape for one or more extended taps can use different shapes. In one example, the filter shape for one or more extended taps can use a diamond shape. In one example, the filter shape for one or more extended taps can use a square shape. In one example, the filter shape for one or more extended taps can use a cross shape. Alternatively, the filter shape for one or more extended taps can use a symmetrical shape. Alternatively, the filter shape for one or more extended taps can use an asymmetrical shape. Alternatively, the filter shape for one or more extended taps can use any other shape. In one example, the filter shape for one or more extended taps can be determined, signaled, or derived in real time.

[0299] Example 8

[0300] In one example, the filter may include one or more filter lengths corresponding to different types of taps (e.g., a filter length for one or more spatial taps and a filter length for one or more extended taps). In one example, inside the filter, the filter length for one or more spatial taps may be different from the filter length for one or more extended taps. Alternatively, inside the filter, the filter length for one or more spatial taps may be the same as the filter length for one or more extended taps. In one example, inside the filter, the filter lengths for one or more spatial taps may use different sizes. In one example, the filter length for one or more spatial taps may be equal to N (e.g., N=9 or 11 or 13). In one example, the filter length for one or more spatial taps may be determined / signaled / derived in real time. In one example, inside the filter, the filter length for one or more extended taps may use different sizes. In one example, the filter length for one or more extended taps may be equal to N (e.g., N=3). In one example, the filter length for one or more extended taps may be determined / signaled / derived in real time. In one example, a filter including one or more spatial taps and one or more extended taps may be designed as follows.

[0301] Example 9

[0302] In one example, Fig.14 A filter containing 20 spatial taps having a diamond shape and 5 extension taps having a diamond shape is designed.

[0303] Example 10

[0304] In one example, Fig.15 A filter containing 20 spatial taps having a diamond shape and 13 extension taps having a diamond shape is designed.

[0305] Example 11

[0306] In one example, Fig.16 A filter containing 20 spatial taps having a cross shape and 5 extension taps having a diamond shape was designed.

[0307] Example 12

[0308] In one example, Fig.17 A filter containing 20 spatial taps having a cross shape and 13 extension taps having a diamond shape was designed.

[0309] Example 13

[0310] In one example, a symmetry constraint may be applied to a filter including at least one extended tap. In one example, a geometric symmetry constraint may be applied to one or more spatial taps. In one example, a geometric symmetry constraint may be applied to one or more extended taps. In one example, Fig.18 Design a filter with 20 spatial taps and 7 expansion taps.

[0311] Example 14

[0312] In one example, Fig.19 Design a filter with 20 spatial taps and 3 expansion taps.

[0313] Example 15

[0314] In one example, Fig. 20 Design a filter with 20 spatial taps and 7 expansion taps.

[0315] Example 16

[0316] In one example, a symmetric constraint based on multiple inputs may be performed on one or more extended taps. Fig.21 A filter comprising 20 spatial taps and 13 extended taps and having 2 inputs (eg, samples inside 2 reference pictures) is designed.

[0317] Example 17

[0318] In one example, the geometry-based and multiple-input-based symmetry constraints can be performed separately. Alternatively, the geometry-based and multiple-input-based symmetry constraints can be performed jointly. In one example, the Fig. 22 A filter comprising 20 spatial taps and 7 extension taps and having 2 inputs (eg, samples inside 2 reference pictures) is designed.

[0319] Example 18

[0320] In one example, a filter having at least one extension tap may have multiple inputs (e.g., input A, input B, and input C) for one or more extension taps. Fig.23 Design a filter with 20 spatial taps and 5 expansion taps.

[0321] Example 19

[0322] In one example, Fig.24 Design a filter with 20 spatial taps and 9 expansion taps.

[0323] Example 20

[0324] In one example, Fig.25 Design a filter with 20 spatial taps and 2 expansion taps.

[0325] In one example, the total number of extension taps inside the filter may be jointly derived based on the shape, filter length, and / or symmetry constraints.

[0326] Example 21

[0327] In one example, a first syntax element may be signaled to indicate 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. In one example, the first syntax element may be encoded and decoded with at least one context. The context may depend on the encoding 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. In one example, the first syntax element may be binarized by a unary code, or a truncated unary code, or a fixed length code, or an exponential Golomb code, a truncated exponential Golomb code, or the like. 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 in a predictive manner. The first syntax element may be predicted by an on / off decision of the extended tap of at least one adjacent block. The first syntax element may be signaled independently for different color components. Alternatively, the first syntax element may be signaled and shared for different color components. Alternatively, the first syntax element may be signaled for the first color component but not signaled for the second color component.

[0328] Example 22

[0329] A syntax element structure, such as an APS, may include one or more filters having at least one extended tap. In one example, coefficients of the extended tap may be included in the APS. In one example, clipping parameters of the extended tap may be included in the APS. In one example, class merging results of the extended tap may be included in the APS. Alternatively, other parameters of the extended tap may be included in the APS.

[0330] Example 23

[0331] In one example, the intermediate filtering results of the filter are used as the input of the extension tap. In one example, the intermediate filtering results of the ALF filter trained offline can be used as the input of the extension tap. In one example, the intermediate filtering results of the ALF filter trained online can be used as the input of the extension tap. In one example, the intermediate filtering results of other predefined filters can be used as the input of the extension tap. In one example, other intermediate filtering results of online training filters can be used as the input of the extension tap.

[0332] Example 24

[0333] In one example, the reconstruction samples before or after different coding and decoding stages of the current frame are used as the input of the extension tap. In one example, the reconstruction before / after the DBF of the current frame can be used as the input of the extension tap. In one example, the reconstruction before / after the SAO / CCSAO of the current frame can be used as the input of the extension tap. In one example, the reconstruction before / after the BIF of the current frame can be used as the input of the extension tap. Alternatively, the reconstruction before / after other stages of the current frame can be used as the input of the extension tap.

[0334] Example 25

[0335] In one example, multiple filter shapes can be applied within a video unit. This is described herein as a filter shape switching method. In one example, the filter shapes to be applied may be different for two samples within a video unit. In one example, the filter shapes to be applied may be different for two CTUs / CTBs. In one example, the filter shapes to be applied may be different for two regions (e.g., strips / slices / sub-pictures / pictures) within a video unit. In one example, the filter shape to be selected from multiple filter shapes can be signaled, inherited, or derived on the fly. In one example, the filter shape can indicate which adjacent samples (adjacent or non-adjacent) are involved in the filtering process of the current sample. In one example, the filter shape can indicate how many adjacent samples are involved. Two filtering methods with different filter taps can also be regarded as two different filter shapes (even the filter coefficients at certain positions can be regarded as equal to 0). For example, a diamond 5*5 and a diamond 7*7 are regarded as different filter shapes. For example, even if the filter taps are the same, a diamond 5*5 and a finite square 5*5 are regarded as different filter shapes. In one example, a filter with at least one extended tap and a filter without an extended tap are regarded as different filter shapes. In one example, a filter having N (e.g., N>0) extension taps is considered to have different filter shapes (N may be equal to or not equal to M) than a filter having M (e.g., M>0) extension taps. In one example, if the shape or length used for one or more spatial taps is different, the filter having at least one extension tap is considered to use a different shape. In one example, if the shape or length used for one or more extension taps is different, the filter having at least one extension tap is considered to use a different shape. In one example, if the shape or length used for one or more spatial taps is different from the shape or length used for one or more extension taps, the filter having at least one extension tap is considered to use a different shape. In one example, if the input of one or more extension taps is different, the filter having at least one extension tap is considered to use a different shape. In one example, an indication of the filter shape may be signaled in a bitstream, for example, in an ALFAPS. In one example, for a video unit to be filtered, when the filter coefficients are inherited / predicted from a given ALF APS, the filter shape associated with the ALFAPS may also be inherited.

[0336] Example 26

[0337] In one example, the disclosed filter shape switching method can be applied to any loop filtering tool, pre-processing or post-processing filtering method (including but not limited to ALF / CCALF or any other filtering method) in video coding. In one example, the disclosed filter shape switching method can be applied to loop filtering method. In one example, the disclosed filter shape switching method can be applied to ALF. In one example, the disclosed filter shape switching method can be applied to CCALF. In one example, the disclosed filter shape switching method can be applied to other loop filtering methods. In one example, the disclosed filter shape switching method can be applied to pre-processing filtering method. In one example, the disclosed filter shape switching method can be applied to post-processing filtering method.

[0338] Example 27

[0339] An exemplary first syntax element may be signaled to indicate a filter shape. In one example, the first syntax element may be encoded and decoded by arithmetic coding. In one example, the first syntax element may be encoded and decoded with at least one context. The context may depend on the encoding 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. In one example, the first syntax element may be binarized by a unary code, or a truncated unary code, or a fixed length code, or an exponential Golomb code, a truncated exponential Golomb code, or the like. In one example, the first syntax element may be conditionally signaled. For example, the first syntax element may be signaled only when the number of available filter shapes is at least 2. The first syntax element may be encoded and decoded in a predictive manner. The first syntax element may be predicted by the filter shape of at least one adjacent block. The first syntax element may be signaled independently for different color components. In one example, the first syntax element may be signaled and shared for different color components. In one example, a first syntax element may be signaled for a first color component, but not signaled for a second color component.

[0340] Example 28

[0341] In an example, a syntax element structure (such as an APS) may include filters having one or more filter shapes for different color components. In the following discussion, an APS may be used to represent a syntax element structure. In an example, a syntax element structure may include filters having the same filter shape. In an example, a shape candidate index may be signaled in the syntax element structure. In an example, the number of enabled filters having a selected filter shape candidate may be signaled in the syntax element structure. In an example, a class merging result of a filter having a selected filter shape candidate may be signaled in the syntax element structure. In an example, coefficients of a filter having a selected filter shape candidate may be signaled in the syntax element structure. In an example, a syntax element structure (such as an APS) may include filters having different filter shapes. In an example, a filter shape index for each filter may be signaled. In an example, a filter shape index for each filter set having different filter shapes may be signaled in the syntax element structure. In an example, the number of enabled filters associated with the filter shape index may be signaled in the syntax element structure. In an example, the number of enabled filters for each filter set associated with the filter shape index may be signaled in the syntax element structure. In one example, the class merging results may be signaled in a syntax element structure. In one example, the class merging results for each filter set associated with a filter shape index may be signaled in a syntax element structure. In one example, the coefficients for each enabled filter may be signaled in a syntax element structure. In one example, the coefficients for each filter set associated with a filter shape index may be signaled in a syntax element structure.

[0342] Example 29

[0343] In one example, filter shape switching is implemented between multiple shape candidates. In one example, the shape candidate may not have an extended tap. In one example, the candidate shape may use a diamond shape. In one example, the candidate shape may use a cross shape. In one example, the candidate shape may use a square shape. In one example, the candidate shape may use a symmetrical shape. In one example, the candidate shape may use an asymmetrical shape. In one example, the candidate shape may use a square shape. Fig.26 Design candidate shapes without extended taps.

[0344] Example 30

[0345] In one example, Fig. 27 Design candidate shapes without extended taps.

[0346] Example 31

[0347] In one example, the shape candidate may have an extended tap. In one example, the candidate shape with at least one extended tap may be designed using the method mentioned above. In one example, the candidate shape with at least one extended tap may be designed without using the method mentioned above. In one example, the filter shape switching may be implemented by switching between shape candidates without extended taps. In one example, the filter shape switching may be implemented by switching between shape candidates without extended taps. Fig.26 The shape candidates shown are Fig. 27 In one example, the filter shape switching can be achieved by switching between one or more shape candidates without an extended tap and one or more shape candidates with at least one extended tap. Fig. 27 The shape candidates shown are Fig.18 The filter shape switching can be achieved by switching between the shape candidates shown in FIG. Fig. 27 The shape candidates shown are Fig.19 The filter shape switching can be achieved by switching between the shape candidates shown in FIG. Fig. 27 The shape candidates shown are Fig. 20 The filter shape switching can be achieved by switching between the shape candidates shown in FIG. Fig. 27 The shape candidates shown are Fig.23 The filter shape switching can be achieved by switching between the shape candidates shown in FIG. Fig. 27 The shape candidates shown are Fig.24 The filter shape switching can be achieved by switching between the shape candidates shown in FIG. Fig. 27 The shape candidates shown are Fig.25 The filter shape switching can be achieved by switching between the shape candidates shown in FIG. 1 and FIG. 2 . In one example, the filter shape switching can be achieved by switching between the shape candidates having at least one extended tap. Fig.25 The shape candidates shown are Fig.21 The filter shape switching can be achieved by switching between the shape candidates shown in FIG. Fig.25 The shape candidates shown are Fig. 22 The filter shape switching can be achieved by switching between the shape candidates shown in FIG. Fig.25 The shape candidates shown are Fig.23 The filter shape switching can be achieved by switching between the shape candidates shown in FIG. Fig.25 The shape candidates shown are Fig.24 Switching between the shape candidates shown implements filter shape switching.

[0348] Example 32

[0349] In one example, the above mentioned methods can be used in combination.

[0350] Example 33

[0351] Alternatively, the above-mentioned methods may be used individually.

[0352] Example 34

[0353] In one example, the disclosed extended tap method can 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 can be applied to loop filtering methods. In one example, the proposed extended tap method can be applied to ALF. In one example, the proposed extended tap method can be applied to CCALF. Alternatively, the proposed extended tap method can be applied to other loop filtering methods. In one example, the proposed extended tap method can be applied to pre-processing filtering methods. In one example, the proposed extended tap method can be applied to post-processing filtering methods.

[0354] Example 35

[0355] 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.

[0356] Example 36

[0357] Whether and / or how the methods disclosed above are applied may be signaled in the bitstream. In one example, they may 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 / DCI / PPS / APS / slice header / slice group header. In one example, they may be signaled in a PB / TB / CB / PU / TU / CU / VPDU / CTU / CTU row / slice / slice / sub-picture / other type of region containing more than one sample or pixel.

[0358] Example 37

[0359] 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.

[0360] Fig.28 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.

[0361] 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 "codec" 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.

[0362] 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.

[0363] Fig.294106 is a block diagram of an example video processing device 4100. Device 4100 may be used to implement one or more methods described herein. Device 4100 may be implemented as a smart phone, a tablet computer, a computer, an Internet of Things (IoT) receiver, etc. Device 4100 may include one or more processors 4102, one or more memories 4104, and video processing circuitry 4106. Processor 4102 may be configured to implement one or more methods described in this document. Memory (memory) 4104 may be used to store data and code for implementing the methods and techniques described herein. Video processing circuitry 4106 may be used to implement some of the techniques described in this document in hardware circuits. In some embodiments, video processing circuitry 4106 may be at least partially included in processor 4102 (e.g., a graphics coprocessor).

[0364] Fig.30 4200. The method 4200 includes determining to apply a filter to a video unit at step 4202. The filter uses a first filter shape for a first sample in the video unit and a second filter shape for a second sample in the video unit, and the first filter shape is different from the second filter shape. At step 4204, conversion between visual media data and a bitstream is performed based on the video unit. According to an example, the conversion of step 4204 can include encoding at an encoder or decoding at a decoder.

[0365] It should be noted that the 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 the video encoder 4400, the video decoder 4500, and / or the encoder 4600. In this case, the instructions, when executed by the processor, cause the processor to perform the method 4200. In addition, the 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 the processor, the video codec device performs the method 4200.

[0366] Fig.31 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 encoding 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.

[0367] 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.

[0368] 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.

[0369] 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.

[0370] Fig.32 is a block diagram showing an example of a video encoder 4400, which may be Fig.31 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.

[0371] The functional components of the video encoder 4400 may include a partition 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.

[0372] 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.

[0373] 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.

[0374] The partitioning unit 4401 may partition a picture into one or more video blocks. The video encoder 4400 and the video decoder 4500 may support various video block sizes.

[0375] 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).

[0376] 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.

[0377] 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.

[0378] 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.

[0379] 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.

[0380] 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.

[0381] 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.

[0382] 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.

[0383] As discussed above, the video encoder 4400 can predictively signal motion vectors.Two examples of predictive signaling techniques that can be implemented by the video encoder 4400 include Advanced Motion Vector Prediction (AMVP) and Merge mode signaling.

[0384] 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.

[0385] 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.

[0386] 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.

[0387] 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.

[0388] 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.

[0389] 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.

[0390] 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.

[0391] 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.

[0392] Fig.33 is a block diagram showing an example of a video decoder 4500, which may be Fig.31 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.

[0393] 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.

[0394] 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.

[0395] 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.

[0396] 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.

[0397] 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, partition 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.

[0398] 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.

[0399] 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.

[0400] Fig.34 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.

[0401] 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 .

[0402] Fig.35 4700. The method 4700 includes determining to apply a filter to a video unit at step 4702. The filter uses an extended tap for a first sample point in the video unit and a spatial tap for a second sample point in the video unit. At step 4204, conversion between visual media data and a bitstream is performed based on the video unit. According to an example, the conversion of step 4704 can include encoding at an encoder or decoding at a decoder.

[0403] It should be noted that method 4700 may be implemented on an apparatus for processing video data, the apparatus comprising one or more processors and one or more non-transitory memories having instructions thereon, such as video encoder 4400, video decoder 4500, and / or encoder 4600. In this case, the instructions, when executed by one or more processors, cause the one or more processors 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 encoding device. The computer program product includes computer-executable instructions stored on a non-transitory computer-readable medium, such that when executed by one or more processors, the video encoding device performs method 4700.

[0404] A list of solutions preferred by some examples is provided next.

[0405] The following solutions illustrate examples of the techniques discussed herein.

[0406] 1. A method for processing video data (e.g., Fig.304200) comprising: determining (4202) to apply a filter to a video unit, wherein the filter uses a first filter shape for a first sample point in the video unit and a second filter shape for a second sample point in the video unit, and wherein the first filter shape is different from the second filter shape; and performing (4204) conversion between visual media data and a bitstream based on the video unit.

[0407] 2. A method as in solution 1, wherein the first sample point is located in a first region of the video unit, the second sample point is located in a second region of the video unit, and wherein the first region and the second region are different codec tree units (CTUs), different slices, different slices, different sub-pictures, or a combination thereof.

[0408] 3. The method of any one of solutions 1 to 2, wherein the first filter shape specifies a first set of neighboring sample points involved in filtering the first sample point, and wherein the second filter shape specifies a second set of neighboring sample points involved in filtering the second sample point.

[0409] 4. The method of any one of solutions 1 to 3, wherein the first filter shape and the second filter shape have different numbers of filter taps.

[0410] 5. The method of any one of solutions 1 to 4, wherein the first filter shape and the second filter shape have different lengths.

[0411] 6. A method as in any one of solutions 1 to 5, wherein the first filter shape has a first extension tap, wherein the second filter shape has a second extension tap, and wherein the first extension tap and the second extension tap receive different inputs.

[0412] 7. The method of any one of solutions 1 to 6, wherein the indication of the first filter shape and the second filter shape is included in an adaptive parameter set (APS) in the bitstream.

[0413] 8. A method as described in any one of solutions 1 to 7, wherein the indication of the first filter shape is encoded or decoded according to arithmetic coding, context coding, bypass coding, conditional coding, predictive coding, unary code, truncated unary code, fixed length code, exponential Golomb code, truncated exponential Golomb code or a combination thereof.

[0414] 9. A method as described in any one of solutions 1 to 8, wherein the indication of the first filter shape is independently encoded and decoded for multiple color components.

[0415] 10. The method of any one of solutions 1 to 9, wherein the filter is applied as a loop filter, a pre-processing filter, a post-processing filter, or a combination thereof.

[0416] 11. The method of any one of solutions 1 to 10, wherein the filter is an adaptive loop filter (ALF).

[0417] 12. A method as in any of solutions 1 to 11, wherein an indication of a filter shape candidate index, a number of enabled filters, a class merging result, a filter coefficient, or a combination thereof is included in a parameter set in the bitstream.

[0418] 13. A method as described in any one of solutions 1 to 12, wherein at least one of the first filter shape and the second filter shape is indicated as a candidate shape in the bitstream, and wherein the candidate shape includes a diamond, a cross, a square, a symmetrical shape, an asymmetrical shape, a shape with extended taps, a shape without extended taps, or a combination thereof.

[0419] 14. A method as in any one of solutions 1 to 13, wherein the filter comprises a plurality of filter lengths.

[0420] 15. The method of any one of solutions 1 to 14, wherein the filter comprises at least one of an extension tap and a spatial tap.

[0421] 16. A method as in any one of solutions 1 to 15, wherein the coefficients resulting from applying the expansion taps correspond to one or more inputs.

[0422] 17. A method as in any one of solutions 1 to 16, wherein the filter is trained by training data collected jointly between the extension tap and the spatial tap.

[0423] 18. A method as in any one of solutions 1 to 17, wherein the extension tap and the spatial tap are jointly trained.

[0424] 19. A method as in any one of solutions 1 to 18, wherein the parameters of the extension taps and the parameters of the spatial taps are derived jointly.

[0425] 20. A method as in any one of solutions 1 to 19, wherein the conversion comprises encoding the visual media data into the bitstream.

[0426] 21. A method as in any of solutions 1 to 19, wherein the conversion comprises decoding the visual media data from the bitstream.

[0427] 22. A device 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 21.

[0428] 23. 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 21.

[0429] 24. 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 filter a video unit, wherein the filter adopts a first filter shape for a first sample point in the video unit and adopts a second filter shape for a second sample point in the video unit, and wherein the first filter shape is different from the second filter shape; and generating a bitstream based on the determination.

[0430] 25. A method for storing a bitstream of a video, comprising: determining to filter a video unit, wherein the filter uses a first filter shape for a first sample point in the video unit and a second filter shape for a second sample point in the video unit, and wherein the first filter shape is different from the second filter shape; generating a bitstream based on the determination; and storing the bitstream in a non-transitory computer-readable recording medium.

[0431] 26. A method for storing a bitstream of a video, comprising: determining to apply a filter to a video unit, wherein the filter uses an extended tap for a first sample point in the video unit and a spatial tap for a second sample point in the video unit; generating the bitstream based on the determination; and storing the bitstream in a non-temporary computer-readable recording medium.

[0432] 27. A method, apparatus or system as herein described.

[0433] In the solution described herein, an encoder can comply with the format rules by generating a codec representation according to the format rules. In the solution described herein, a decoder can parse syntax elements in the codec representation using the format rules and generate decoded video based on the presence and absence of syntax elements known according to the format rules.

[0434] 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.

[0435] 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, i.e., one or more modules of computer program instructions, encoded on a computer-readable medium for execution by a data processing device or for controlling the operation of the data processing device. 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, equipment 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.

[0436] 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.

[0437] 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 the apparatus may also be implemented as, a special purpose logic circuit, such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0438] 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.

[0439] Although many details are included herein, 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 features may be described above as acting in certain combinations and even initially claimed, 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.

[0440] 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.

[0441] 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.

[0442] 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.

[0443] 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.

[0444] 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 a filter to a video unit, wherein the filter employs extended taps for a first sample in the video unit and spatial taps for a second sample in the video unit; and Conversion between visual media data and a bitstream is performed based on the video unit.

2. The method of claim 1, wherein the extended tap is applied only to a luma component of the first sample. The method of claim 1 , wherein the shape of the spatial tap comprises a cross. The method of claim 1 , wherein a shape of the extended tap comprises a diamond shape. The method of claim 1 , wherein a shape of the extended tap comprises a cross.

6. The method of claim 1, wherein the extension tap is a first extension tap, wherein the filter employs a second extension tap, and wherein the first extension tap and the second extension tap receive different inputs.

7. The method of claim 1, wherein the filter comprises 20 spatial taps and 5 extension taps.

8. The method of claim 1, wherein the filter comprises 20 spatial taps and 9 extension taps.

9. The method of claim 1, wherein the filter comprises 20 spatial taps and 2 extension taps.

10. The method of claim 1, wherein a first syntax element is signaled to indicate whether at least one extension tap inside the filter is enabled.

11. The method of claim 10, wherein the first syntax element is binarized by a unary code, a truncated unary code, a fixed length code, an exponential Golomb code, or a truncated exponential Golomb code.

12. The method of claim 1, further comprising using an intermediate filtering result as an input to the expansion tap, wherein the intermediate filtering result comprises a result of an offline trained filter of an adaptive loop filter.

13. The method of claim 1, wherein a filter shape applied to a first codec tree unit (CTU) or codec tree block (CTB) is different from a filter shape applied to a second CTU or CTB.

14. The method of claim 1, wherein a syntax element structure comprises an indication of a shape of the extension taps and / or the spatial taps.

15. The method of claim 14, wherein the syntax element structure signals: the number of enabled filters having the selected filter shape candidate; a class merging result of said filter with said selected filter shape candidate; or Coefficients and parameters of a filter having the selected filter shape candidate.

16. The method of claim 1, wherein the converting comprises encoding the visual media data into the bitstream.

17. The method of claim 1, wherein the converting comprises decoding the visual media data from the bitstream.

18. A device for processing video data, comprising: one or more processors; as well as one or more non-transitory memories coupled to the one or more processors and storing instructions that, when executed by the one or more processors, cause the device to be configured to: determining to apply a filter to a video unit, wherein the filter employs extended taps for a first sample in the video unit and spatial taps for a second sample in the video unit; and Conversion between visual media data and a bitstream is performed based on the video unit.

19. The apparatus of claim 18, wherein the extended tap is applied only to a luma component of the first sample point, The shape of the spatial tap includes a cross shape, The shape of the extended tap includes a rhombus or a cross, wherein the extended tap is a first extended tap, the filter adopts a second extended tap, and the first extended tap and the second extended tap receive different inputs, and The filter includes 20 spatial taps and 5 extension taps, 9 extension taps or 2 extension taps.

20. The apparatus of claim 18, wherein a syntax element structure comprises an indication of a shape of the extension tap and / or the spatial tap, and wherein the syntax element structure signals: the number of enabled filters having the selected filter shape candidate; a class merging result of said filter with said selected filter shape candidate; or Coefficients and parameters of a filter having the selected filter shape candidate.

21. A non-transitory computer-readable medium, comprising a computer program product for use with a video codec device, the computer program product comprising computer-executable instructions stored on the non-transitory computer-readable medium, the computer-executable instructions, when executed by one or more processors, causing the video codec device to be configured to: Determining to apply a filter to a video unit, wherein the filter employs extended taps for a first sample in the video unit and spatial taps for a second sample in the video unit; and Conversion between visual media data and a bitstream is performed based on the video unit.

22. 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 a filter to a video unit, wherein the filter employs extended taps for a first sample in the video unit and spatial taps for a second sample in the video unit; and The bitstream is generated based on the determination.

23. A method for storing a bitstream of a video, comprising: determining to apply a filter to a video unit, wherein the filter uses extended taps for a first sample in the video unit and spatial taps for a second sample in the video unit; 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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