Using different sources for Hadamard domain filters in video coding

Abstract

A mechanism for processing video data is disclosed. The mechanism includes determining that a Hadamard domain filter (HDF) process is applied to a sample point of a picture, wherein the HDF process applies an average sum, a weighted sum, a linear sum, a non-linear sum, a Wiener function, or a combination thereof; a conversion between the visual media data and the bitstream is performed based on the HDF.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of International Patent Application No. PCT / CN2022 / 113579, filed on August 19, 2022. The contents of the foregoing patent application are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates to the generation, storage and use of digital audio-visual 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] The first aspect relates to a method for processing video data, comprising: determining to apply a Hadamard domain filter (HDF) process to samples of a picture, wherein the HDF process applies an average sum, a weighted sum, a linear sum, a non-linear sum, a Wiener function or a combination thereof; and performing conversion between visual media data and a bitstream based on the HDF process.

[0006] A second aspect relates to a method for processing video data, comprising: determining to apply a Hadamard domain filter (HDF) process to samples of a picture, wherein the HDF process applies an average sum, a weighted sum, a linear sum, a nonlinear sum, a Wiener function, or a combination thereof to generate filtered samples; determining to apply an adaptive HDF process to combine the filtered samples with signaled parameters and / or online trained parameters; and performing conversion between visual media data and a bitstream based on the HDF and the adaptive HDF process.

[0007] A third aspect relates to an apparatus for processing video data, comprising: a processor; and a non-transitory memory having instructions thereon, wherein the instructions, when executed by the processor, cause the processor to perform any of the aforementioned aspects.

[0008] A fourth aspect relates to a non-temporary computer-readable medium, comprising a computer program product for use by a video encoding device, the computer program product comprising computer executable instructions stored on the non-temporary computer-readable medium, so that when executed by a processor, the video encoding device performs the method of any of the preceding aspects.

[0009] A fifth 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 Hadamard domain filter (HDF) process to samples of a picture, wherein the HDF process applies an average sum, a weighted sum, a linear sum, a non-linear sum, a Wiener function, or a combination thereof; and generating the bitstream based on the determination.

[0010] The sixth aspect relates to a method for storing a bitstream of a video, comprising: determining to apply a Hadamard domain filter (HDF) process to samples of a picture, wherein the HDF process applies an average sum, a weighted sum, a linear sum, a non-linear sum, a Wiener function, or a combination thereof; generating the bitstream based on the determination; and storing the bitstream in a non-temporary computer-readable recording medium.

[0011] The seventh aspect relates to a method, device or system described in this patent document.

[0012] 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.

[0013] 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

[0014] 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.

[0015] Figure 1 An example of nominal vertical and horizontal positions of 4:2:2 luma and chroma samples in a picture is shown.

[0016] Figure 2 An example encoder block diagram is shown.

[0017] Figure 3 An example picture segmented into raster scan strips is shown.

[0018] Figure 4 An example picture segmented into rectangular scan strips is shown.

[0019] Figure 5 An example picture showing partitioning into bricks.

[0020] FIG. 6 shows an example of a codec tree block (CTB) that crosses a picture boundary.

[0021] Figure 7 An example of an intra prediction mode is shown.

[0022] Figure 8 Examples of block boundaries in a picture are shown.

[0023] Fig. 9 An example of pixels involved in filter usage is shown.

[0024] Fig.10 An example of a filter shape of an adaptive loop filter (ALF) is shown.

[0025] Fig.11 An example of transform coefficients supported by a 5×5 diamond filter is shown.

[0026] Fig.12 An example of relative coordinates supported by a 5×5 diamond filter is shown.

[0027] Fig.13 An example scan pattern is shown.

[0028] Fig.14 is a block diagram illustrating an example video processing system.

[0029] Fig.15 is a block diagram of an example video processing device.

[0030] Fig.16 is a flow chart of an example method for video processing.

[0031] Fig.17 is a block diagram illustrating an example video codec system.

[0032] Fig.18 is a block diagram illustrating an example encoder.

[0033] Fig.19 is a block diagram illustrating an example decoder.

[0034] Fig. 20 is a schematic diagram of an example encoder. DETAILED DESCRIPTION

[0035] 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.

[0036] 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.

[0037] 1. Initial Discussion

[0038] This document relates to video codec technology. In particular, it relates to loop filters and other codec 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, either alone or in various combinations.

[0039] 2. Abbreviations

[0040] The present disclosure includes the following abbreviations. Advanced Video Codec (Rec. ITU-T H.264 | ISO / IEC 14496-10) (AVC), Codec Picture Buffer (CPB), Pure Random Access (CRA), Codec Tree Unit (CTU), Codec Video Sequence (CVS), Decoded 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)), International Organization for Standardization (ISO), International Electrotechnical Commission (IEC), 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, Layer and Level (PTL), Picture Unit (PU), Reference Picture Resample (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 / IEC23090-3) (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), Bilateral Filter (BF); and Hadamard Domain Filter (HDF).

[0041] 3. Video Codec Standards

[0042] Video codec standards have evolved primarily through the development of International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) and ISO / IEC standards. ITU-T produced H.261 and H.263, ISO / IEC produced Moving Picture Experts Group (MPEG-1) and MPEG-4 Vision, and the two organizations jointly produced H.262 / MPEG-2 Video and H.264 / MPEG-4 Advanced Video Codec (AVC) and H.265 / HEVC standards. Since H.262, video codec standards are based on a hybrid video codec structure, which utilizes temporal prediction plus transform codec. In order 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 took many approaches and put them into a reference software called the Joint Exploration Model (JEM). When the Versatile Video Codec (VVC) project was officially launched, JVET was renamed the Joint Video Experts Team (JVET). VVC is a coding standard that aims to reduce the bit rate by 50% compared to HEVC. The VVC Working Draft and the VVC Test Model (VTM) are continuously updated.

[0043] ITU-T VCEG and ISO / IEC MPEG Joint Technical Committee (JTC) 1 / Subcommittee (SC) 29 / Working Group (WG) 11 are studying the potential need for standardization of future video codec technologies with compression capabilities that will significantly exceed 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 JVET to evaluate compression technology designs proposed by their experts in the field. The first Exploratory Experiment (EE) was established by JVET and reference software named Enhanced Compression Model (ECM) is in use. The test model ECM is continuously updated.

[0044] 3.1 Color Space and Chroma Subsampling

[0045] A color space (also called a color model (or color system)) is a mathematical model that describes a range of colors as a tuple of numbers, for example as 3 or 4 values ​​or color components (e.g., RGB). In general, a color space is a specialization 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).

[0046] YCbCr, Y'CbCr or YPb / CbPr / Cr (also written as YCBCR or Y'CBCR) is a general term for a family of color spaces that are used in video systems and digital photography as part of the color image processing pipeline. Y' is the luminance component, and CB and CR are the blue difference chrominance components and red difference chrominance components. 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.

[0047] Chroma subsampling is the practice of encoding an image at a lower resolution for chroma information than for luminance information by exploiting the fact that the human visual system is less sensitive to color differences than to luminance. 3.1.1 4:4:4

[0049] In 4:4:4, each of the three components Y'CbCr has the same sampling rate. Therefore, there may be no chroma subsampling. This scheme is sometimes used in high-end film scanners and film post-production. 3.1.2 4:2:2

[0051] 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 An example of nominal vertical and horizontal positions of 4:2:2 color format luma and chroma samples in a picture is shown in FIG. 3.1.3 4:2:0

[0053] In 4:2:0, horizontal sampling is doubled compared to 4:1:1, but since the Cb and Cr channels are sampled only on alternate lines in this scheme, the vertical resolution is halved while the data rate remains the same. Cb and Cr are each subsampled by a factor of 2 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 horizontally. Cb and Cr are located between pixels vertically (i.e., in the gaps). In JPEG / JFIF, H.261, and MPEG-1, Cb and Cr are located in the gaps between alternate luminance samples. In 4:2:0DV, Cb and Cr are co-located horizontally. Vertically, they are co-located on alternate lines.

[0054]

[0055]

[0056] Table 1. SubWidthC and SubHeightC values ​​derived from chroma_format_idc and Separate_colour_plane_flag

[0057] 3.2 Example Encoding and Decoding Process of Video Codec

[0058] Figure 2 An example of an encoder block diagram of VVC is shown, which contains three loop filtering modules: deblocking filter (DF), sample adaptive offset (SAO) and ALF. Unlike DF, which uses a predefined filter, SAO and ALF use the original samples of the current picture to reduce the mean square error between the original samples and the reconstructed samples by adding an offset and applying a finite impulse response (FIR) filter, respectively. The side information of the codec is used 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 tries to capture and repair artifacts produced by previous stages.

[0059] 3.3 Definition of Video / Codec Unit

[0060] 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 brick consisting of a certain number of CTU rows within the slice. 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.

[0061] 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 raster scan stripe partitioning of a picture (with 18 by 12 luma CTUs) is shown, where the picture is divided into 12 slices and 3 raster scan stripes.

[0062] Figure 4 An example of rectangular slice partitioning of a picture (with 18 by 12 luma CTUs) is shown, where the picture is divided into 24 slices (6 slice columns and 4 slice rows) and 9 rectangular slices.

[0063] Figure 5An example of a picture being partitioned 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.

[0064] 3.3.1 CTU / CTB size

[0065] 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.

[0066] 7.3.2.3 Sequence parameter set RBSP syntax

[0067]

[0068]

[0069]

[0070] 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:

[0071] CtbLog2SizeY = log2_ctu_size_minus2 + 2 (7-9)

[0072] CtbSizeY = 1 << CtbLog2SizeY (7-10)

[0073] MinCbLog2SizeY=log2_min_luma_coding_block_size_minus2+2 (7-11)

[0074] MinCbSizeY = 1 << MinCbLog2SizeY (7-12)

[0075] MinTbLog2SizeY = 2 (7-13)

[0076] MaxTbLog2SizeY = 6 (7-14)

[0077] MinTbSizeY = 1 << MinTbLog2SizeY (7-15)

[0078] MaxTbSizeY = 1 << MaxTbLog2SizeY (7-16)

[0079] PicWidthInCtbsY = Ceil( pic_width_in_luma_samples ÷ CtbSizeY ) (7-17)

[0080] PicHeightInCtbsY = Ceil( pic_height_in_luma_samples ÷ CtbSizeY )(7-18)

[0081] PicSizeInCtbsY = PicWidthInCtbsY * PicHeightInCtbsY (7-19)

[0082] PicWidthInMinCbsY = pic_width_in_luma_samples / MinCbSizeY (7-20)

[0083] PicHeightInMinCbsY = pic_height_in_luma_samples / MinCbSizeY (7-21)

[0084] PicSizeInMinCbsY = PicWidthInMinCbsY * PicHeightInMinCbsY (7-22)

[0085] PicSizeInSamplesY=pic_width_in_luma_samples * pic_height_in_luma_samples (7-23)

[0086] PicWidthInSamplesC = pic_width_in_luma_samples / SubWidthC (7-24)

[0087] PicHeightInSamplesC = pic_height_in_luma_samples / SubHeightC (7-25)

[0088] 3.3.2 CTUs in a picture

[0089] Assume that the CTB / LCU size is represented by M×N (usually M equals N), and for a CTB located at the picture boundary (or slice or strip or other type of boundary, taking the picture boundary as an example), K×L samples are within the picture boundary, where K < M or L < N. For FIG. 6A to FIG. 6C the CTBs shown in Fig. 6A , the CTB size is still equal to M×N. However, as Figure 6B shown, the lower boundary of the CTB is outside the picture, or as Figure 6C shown, the right boundary of the CTB is outside the picture, or as

[0090] shown, the lower boundary / right boundary of the CTB is outside the picture.

[0091] To capture any edge direction presented in natural videos, the number of directional intra prediction modes is extended from 33 used in HEVC to 65. Figure 7 Additional directional modes are shown in

[0092] , 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. Figure 7 The angular intra prediction direction can be defined as from 45 degrees to -135 degrees in the clockwise direction, as

[0093] shown. In VTM, for non-square blocks, several angular intra prediction modes are adaptively replaced with wide-angle intra prediction modes. The replaced modes are signaled and remapped to the indices of the wide-angle modes after parsing. The total number of intra prediction modes remains unchanged, e.g., 67, and the intra mode codec remains unchanged.

[0094] 3.5 Inter-frame prediction

[0095] For each inter-predicted CU, the motion parameters include motion vector, reference picture index, reference picture list usage index, and additional information required by the new coding features of VVC for sample generation for inter-prediction. Motion parameters can be signaled explicitly or implicitly. When a CU is encoded and decoded using skip mode, the CU is associated with one PU and has no significant residual coefficients, no coded motion vector increments and / or reference picture indexes. Merge mode is defined as a mode by which the motion parameters of the current CU are obtained from neighboring CUs, including spatial and temporal candidates and additional schedules 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 for each CU, the motion vector, the corresponding reference picture index for each reference picture list, the reference picture list usage flag, and other useful information are explicitly signaled.

[0096] 3.6 Deblocking Filter

[0097] 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 picture 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.

[0098] 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.

[0099] Figure 88 is a diagram 800 of samples 802 within an 8x8 block of samples 804. As shown, diagram 800 includes horizontal block boundaries and vertical block boundaries on an 8x8 grid 806, 808, respectively. In addition, diagram 800 shows non-overlapping blocks of 8x8 samples 810, which may be deblocked in parallel.

[0100] 3.6.1 Boundary Decision

[0101] The filtering is applied on 8×8 block boundaries. In addition, such boundaries must be transform block boundaries or codec subblock boundaries, for example, due to the use of affine motion prediction (ATMVP). For other boundaries, the deblocking filter is disabled.

[0102] 3.6.2 Boundary strength calculation

[0103] For transform block boundaries / codec sub-block boundaries, if the boundary is within the 8×8 grid, the boundary can be filtered and the settings of bS[xDi][yDj] for the edge (where [xDi][yDj] represents the coordinates) are defined as in Table 2 and Table 3, respectively.

[0104]

[0105] Table 2. Boundary Strength (When SPS IBC is disabled)

[0106]

[0107]

[0108] Table 3. Boundary Strength (When SPS IBC is Enabled)

[0109] 3.6.3 Deblocking Decision for Luminance Component

[0110] Fig. 9 is an example of a pixel involved in the filter on / off decision and strong / weak filter selection. A wider and stronger luma filter 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 a large block, represented by the variables bSidePisLargeBlk and bSideQisLargeBlk, respectively. bSidePisLargeBlk and bSideQisLargeBlk are defined as follows.

[0111] 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

[0112] 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

[0113] Based on bSidePisLargeBlk and bSideQisLargeBlk, condition 1 is defined as follows:

[0114] Condition 1 = (bSidePisLargeBlk || bSidePisLargeBlk)? True: False

[0115] Next, if condition 1 is true, we further check condition 2. First, we derive the following variables:

[0116] First, derive dp0, dp3, dq0, dq3 according to the HEVC method

[0117] if (side p is greater than or equal to 32)

[0118] dp0=(dp0+Abs(p50-2*p40+p30)+1)>>1

[0119] dp3=(dp3+Abs(p53-2*p43+p33)+1)>>1

[0120] if (q side is greater than or equal to 32)

[0121] dq0=(dq0+Abs(q50-2*q40+q30)+1)>>1

[0122] dq3=(dq3+Abs(q53-2*q43+q33)+1)>>1

[0123] Condition 2 = (d < β)? True: False

[0124] Where d=dp0+dq0+dp3+dq3.

[0125] If both conditions 1 and 2 are met, further check whether any block uses sub-blocks:

[0126]

[0127]

[0128] Finally, if both conditions 1 and 2 are met, the deblocking method will check condition 3 (large block strong filter condition), which is defined as follows. In condition 3 StrongFilterCondition, the following variables are derived:

[0129] Derive dpq in the same way as HEVC.

[0130] Derived according to HEVC method sp3 = Abs (p3-p0)

[0131] if (side p is greater than or equal to 32)

[0132]

[0133] According to the HEVC method, sq3 = Abs (q0-q3) is derived

[0134]

[0135] 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.

[0136] 3.6.4 Stronger Deblocking Filter for Luma

[0137] When the 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. The block boundary samples pi (i=0 to Sp-1) and qi (i=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:

[0138] p i ′=(f i *Middle s,t +(64-f i )*P s +32)>>6), clipped to p i ±tcPD i

[0139] q j ′=(g j *Middle s,t +(64-g j )*Q s +32)>>6), clipped to q j ±tcPD j

[0140] where tcPD i and tcPD jThe term is the position-dependent clipping described above, and g j 、f i 、Middle s,t , P s and Q s Given below.

[0141] 3.6.5 Chroma Deblocking Decision

[0142] A chroma strong filter is used on both sides of the block boundary. Here, the chroma filter is selected when both sides of the chroma edge are greater than or equal to 8 (chroma position), and the decision that meets the following three conditions: The first decision is the decision of boundary strength and large blocks. This filter can be applied when the block width or height orthogonal to the block edge is equal to or greater than 8 in the chroma sample domain. The second and third decisions are basically the same as the HEVC luma deblocking decisions, which are on / off decisions and strong filter decisions, respectively.

[0143] In the first decision, for chroma filtering, the boundary strength (bS) is modified 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.

[0144] 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:

[0145] Derive dpq in the same way as HEVC.

[0146] Derivation of sp3=Ab in the HEVC way s (p3-p0)

[0147] According to the HEVC method, sq3 = Abs (q0-q3) is derived

[0148] 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).

[0149] 3.6.6 Strong Deblocking Filter for Chroma

[0150] The strong deblocking filter for chroma is defined as follows:

[0151] p2′=(3*p3+2*p2+p1+p0+q0+4)>>3

[0152] p1′=(2*p3+p2+2*p1+p0+q0+q1+4)>>3

[0153] p0′=(p3+p2+p1+2*p0+q0+q1+q2+4)>>3

[0154] The example chroma filter performs deblocking on a 4x4 grid of chroma samples.

[0155] 3.6.7 Position-dependent limiting

[0156] 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, the clipping value can be increased 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.

[0157] 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:

[0158] Tc7={6,5,4,3,2,1,1}; Tc3={6,4,2};

[0159] tcPD=(Sp==3)? Tc3:Tc7;

[0160] tcQD=(Sq==3)? Tc3:Tc7;

[0161] For P or Q boundaries filtered with a short symmetric filter, a lower magnitude position-dependent threshold is applied:

[0162] Tc3 = {3, 2, 1};

[0163] After defining the thresholds, the filtered p'i and q'i sample values ​​are clipped according to the tcP and tcQ clipping values:

[0164] p”i=Clip3(p’i+tcPi,p’i–tcPi,p’i);

[0165] q”j=Clip3(q’j+tcQj,q’j–tcQj,q’j);

[0166] Where p'i and q'i are the filtered sample values, p"i and q"j are the clipped output sample values, and tcPi is the clipping threshold derived from the VVC tc parameters and tcPD and tcQD. Function Clip3 is the clipping function as specified in VVC.

[0167] 3.6.8. Sub-block deblocking adjustment

[0168] 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.

[0169] The following applies to sub-block boundaries that are not aligned with CU boundaries.

[0170]

[0171] 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.

[0172] 3.7. Sample Adaptive Offset

[0173] 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 slice. If SAO is applied to the slice, 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.

[0174] SAO Type The type of sample adaptive offset to use Number of categories 0 none 0 1 1-D 0 degree mode 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

[0175] Table 4. SAO type regulations

[0176] 3.8. Adaptive Loop Filter

[0177] 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 codec 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 codec efficiency. Syntactically, the filter coefficients are sent in the header information at the picture level called the adaptive parameter set, and the filter on / off flag of the CTU is interleaved at the CTU level in the strip data. This syntax design not only supports picture-level optimization, but also achieves lower encoding latency.

[0178] 3.8.1. Parameter signaling

[0179] According to the ALF design in VTM, filter coefficients and clipping indices are carried in the ALF Adaptive Parameter Set (APS). The ALF APS may include up to 8 chroma filters and one luma filter set, for a total of up to 25 filters. Each of the 25 luma classes also includes an index. 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 exponential Golomb code followed by a sign bit for non-zero coefficients. 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.

[0180] The filter control syntax elements of ALF in VTM include two types of information. First, the ALF on / off flag 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 level, the filter usage information is signaled at that level. If all slices within a picture use the same APS, the referenced ALF APS ID is encoded and decoded 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.

[0181] The ALF data syntax elements associated with the LUMA component in the VTM are listed below:

[0182]

[0183] 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 for which luma coefficients may be signaled. 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] indicates the index of the signaled adaptive loop filter luma coefficient delta for the filter class indicated by filtIdx, where filtIdx ranges from 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.

[0184] 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:

[0185] If alf_luma_coeff_sign[sfIdx][j] is equal to 0, the corresponding luma filter coefficient has a positive value.

[0186] Otherwise (alf_luma_coeff_sign[sfIdx][j] is equal to 1), the corresponding luma filter coefficient has a negative value.

[0187] When alf_luma_coeff_sign[sfIdx][j] is not present, it is inferred to be equal to 0.

[0188] 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:

[0189]

[0190] 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).

[0191] 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.

[0192] The variable AlfCtbFiltSetIdxY[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] specifies the filter set index for the luma CTB at position (xCtb, yCtb) derived as follows:

[0193] If alf_use_aps_flag is equal to 0, AlfCtbFiltSetIdxY[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is set equal to alf_luma_fixed_filter_idx.

[0194] Otherwise, AlfCtbFiltSetIdxY[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is set equal to 16+alf_luma_prev_filter_idx.

[0195] alf_luma_fixed_filter_idx specifies the fixed filter applied to the luma CTB. The value of alf_luma_fixed_filter_idx shall be in the range of 0 to 15 (inclusive).

[0196] Based on the ALF design of VTM, the ALF design of ECM further introduces the concept of alternative filter sets into the luma filter. Based on the updated luma CTU ALF on / off decision of each alternative / round, the luma 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 data syntax elements of the ALF associated with the luma component in ECM are listed as follows:

[0197]

[0198]

[0199] 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 shall 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 for the luma component with index altIdx. alf_luma_clip_flag[altIdx] equal to 1 specifies that nonlinear adaptive loop filtering may be applied to the alternative luma filter set for the luma component with index altIdx. 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] shall be in the range of 0 to NumAlfFilters-1, inclusive.

[0200] alf_luma_coeff_delta_idx[altIdx][filtIdx] specifies the index of the signaled adaptive loop filter luma coefficient delta for the filter class represented by filtIdx for the alternative luma filter set with index altIdx, where filtIdx ranges from 0 to NumAlfFilters–1. 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.

[0201] 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:

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

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

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

[0205] 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:

[0206]

[0207] 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.

[0208] Filter shape

[0209] 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.

[0210] 3.8.3 Classification of ALF

[0211] 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:

[0212]

[0213] In order to calculate D and First, use the 1-dimensional Laplacian operator to calculate the gradient in the horizontal, vertical and two diagonal directions:

[0214]

[0215] The indices i and j refer to the coordinates of the top left sample point in the 2×2 block, and R(i,j) indicates the reconstructed sample point at coordinate (i,j). The maximum and minimum values ​​of the gradient D in the horizontal and vertical directions are set to:

[0216]

[0217] And the maximum and minimum values ​​of the gradients in the two diagonal directions are set to:

[0218]

[0219] To derive the value of the directionality D, these values ​​are compared with each other and with two thresholds t1 and t2:

[0220] Step 1. If If both are true, D is set to 0.

[0221] Step 2. If Then continue from step 3; otherwise continue from step 4;

[0222] Step 3. If If yes, set D to 2; otherwise, set D to 1.

[0223] Step 4. If Then set D to 4; otherwise, set D to 3.

[0224] The activity value A is calculated as:

[0225]

[0226] 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.

[0227] 3.8.4. Geometric transformation of filter coefficients

[0228] 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.

[0229] Introduce three geometric transformations, including diagonal transformation, vertical flip and rotation:

[0230] Diagonal: f D (k,l)=f(l,k),

[0231] Flip vertically: f V (k,l)=f(k,Kl-1),

[0232] Rotation: f R (k,l)=f(Kl-1,k).

[0233] 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 5×5 diamond are shown.

[0234] Gradient Value Transform <![CDATA[g d2 <g d1 And g h <g v ]]> No transformation <![CDATA[g d2 <g d1 And g v <g h ]]> diagonal <![CDATA[g d1 <g d2 And g h <g v ]]> Flip vertically <![CDATA[g d1 <g d2 And g v <g h ]]> Rotation

[0235] Table 5. Mapping of gradients and transformations computed for a block.

[0236] 3.8.5. Filtering process

[0237] 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.

[0238]

[0239] 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.

[0240] 3.8.6. Nonlinear Filter Reconstruction (reformulation)

[0241] Linear filtering can be reconstructed as the following expression without affecting the encoding and decoding efficiency:

[0242]

[0243] where w(i,j) are the same filter coefficients.

[0244] 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:

[0245]

[0246] 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).

[0247] 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 signaling cost and encoder complexity, only 4 fixed values ​​are used, which are the same for inter and intra slices.

[0248] 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 a bit depth of 10 bits) 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 (in 10-bit encoding) 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:

[0249] Where M = 2 10 And N = 4

[0250] Similarly, the chromaticity table of the clipped value can be obtained according to the following formula:

[0251] Where M = 2 10 , N=4 and A=4

[0252] 3.9 Hadamard Transform Domain Filters in Video Codecs

[0253] The Hadamard transform domain filter (HDF) is a codec tool that can be used in VVC. The HDF is applied to the luminance block after inverse transformation and reconstruction. The filter result is used both for output and for spatial and temporal prediction.

[0254] The Hadamard domain loop filter is always applied to luma reconstructed blocks with non-zero transform coefficients (excluding 4×4 blocks), and is also applied if the slice quantization parameter (QP) is greater than 17. The filter parameters are explicitly derived from codec information. If applied, the HDF is performed on the decoded samples immediately after the inverse transform.

[0255] For each pixel generated by the reconstructed block pixel, the associated processing includes the following steps: First, the 4 neighboring pixels around the processing pixel including the current processing pixel are scanned according to the scanning mode. Second, a 4-point Hadamard transform is performed on the read pixels. Third, spectral filtering is performed based on the following formula:

[0256]

[0257] where (i) is the index of the spectral component in the Hadamard spectrum, R(i) is the spectral component of the reconstructed pixel corresponding to the index, and σ is the filtering parameter derived from the codec quantization parameter QP using the following formula:

[0258] σ=2 (1+0.126*(QP-27))

[0259] It can be noted that filtering implies multiplying the spectral components R(i) by a scaling factor, which is always less than 1. It can also be observed that at high values ​​of R(i), the scaling factor is close to 1. Based on these observations, spectral filtering is implemented using a lookup table, which allows to exclude multiplications and divisions from the filtering operation:

[0260]

[0261] The THR is set to 128, which requires 128 int32 entries to be stored in the ROM per QP. A 4-point inverse Hadamard transform is also applied to the filtered spectrum. After the filtering step, the filtered pixels will be placed to their original positions in the accumulation buffer. After filtering of all pixels in the CU is completed, the accumulated values ​​will be normalized by the number of processing groups used for filtering each pixel. Normalization is implemented as an addition and shift method instead of using division and multiplication. Fig.13 An example of a scan pattern is shown, where A is the current pixel and B, C, and D are surrounding pixels.

[0262] For pixels located on a CU boundary, the scanning pattern is adjusted to ensure that all required pixels are within the current CU.

[0263] 3.10. Bilateral Loop Filter

[0264] 3.10.1. Bilateral Image Filter

[0265] 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

[0266]

[0267] where Δx and Δy are the distances in the vertical and horizontal directions, respectively, and ΔI is the intensity difference between the sample points.

[0268] The edge-preserving denoising bilateral filter uses low-pass Gaussian filters 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 oriented along the edge and greatly reduced in the gradient direction. This is why the bilateral filter can smooth out the noise while preserving the edge structure.

[0269] 3.10.2. Bilateral Filters in Video Codecs

[0270] The bilateral filter in video codec is a codec tool for VVC. The filter acts as a loop filter in parallel with the sample adaptive offset (SAO) filter. Both the bilateral filter and SAO 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 enter 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

[0271]

[0272] 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 and ΔI R Represents the intensity difference between the center sample point and the samples below, to the left, and to the right, respectively.

[0273] 4. Technical problems solved by the disclosed technical solutions

[0274] The example design of the Hadamard domain filter in the video codec system has the following problems. In the example HDF design, only the reconstructed samples of the current frame are used for filtering. However, other valuable information, such as samples inside the reconstructed reference frame or the corresponding predicted frame, can potentially be utilized. In the example HDF design, only the reconstructed samples before the HDF process are used for filtering. However, other valuable information, such as samples before the deblocking filter (DBF) or other stages, can potentially be utilized.

[0275] 5. List of solutions and implementation examples

[0276] 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 may 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 HDF processing unit may refer to a sequence, a picture, a sub-picture, a strip, a CTU, a block, a region or a sample. An HDF processing unit may include one color component or multiple color components.

[0277] In the following disclosure, the filtered sample values ​​are represented as the output of HDF. For example, in the process described below:

[0278]

[0279] where F(i,σ) represents the output of HDF.

[0280] In the following disclosure, HDF represents an example of Hadamard transform domain filtering in video codecs, which typically uses predefined filtering parameters to produce the output of HDF. For example, there is no online training or signaling for filtering parameters in HDF.

[0281] In the following disclosure, adaptive HDF refers to an improved version of HDF on top of HDF in video codecs. Adaptive HDF involves online parameter training and parameter signaling. For example, multiple filtered samples generated based on HDF are further combined with parameters that are signaled and trained online.

[0282] Example 1

[0283] In one example, an adaptive HDF is used to further enhance the efficiency of the HDF. In one example, the final output of the HDF may be generated by a combination of multiple elements. In one example, different combination methods may be applied to generate the final output of the HDF. In one example, an average sum method may be applied. In one example, a weighted sum method may be applied. In one example, a linear sum method may be applied. In one example, a nonlinear sum method may be applied.

[0284] Example 2

[0285] In one example, the combination method can be performed by employing the Wiener function. In one example, the final output of the HDF can be described as follows:

[0286]

[0287] where c i represents the i-th coefficient, f i represents the i-th intermediate output, used as an input element of the final output, N represents the total number of input elements (e.g., N=2), and G represents the final output of the HDF. In an example, the i-th intermediate output can be the output of one HDF. In an example, the intermediate outputs can be generated by different HDFs. In an example, the HDF can use different filter windows. In an example, the HDF can use different filter parameters. In an example, the HDF can use different filter strengths.

[0288] In one example, the i-th intermediate output may be a filtered sample that has not been HDF filtered. For example, the non-HDF filter may be a deblocking filter (DBF), a BF, an adaptive loop filter (ALF), a sample adaptive offset (SAO), a cross-component ALF (CC-ALF), a cross-component SAO (CC-SAO), etc.

[0289] Example 3

[0290] In one example, different settings may be applied to the Wiener function. A clipping method may or may not be applied to the difference between the input element and the current reconstructed sample. A geometric transformation may or may not be applied to the coefficients. In one example, the coefficients may be designed in a symmetrical manner. In one example, the coefficients may be designed in an asymmetrical manner.

[0291] Example 4

[0292] In one example, coefficients can be generated in different ways. In one example, coefficients can be predefined. In one example, coefficients can be determined on-the-fly. In one example, coefficients can be derived on the encoder side and signaled to the decoder side. In one example, clipping and other parameters can be generated in different ways. In one example, clipping and other parameters can be predefined. In one example, clipping and other parameters can be determined on-the-fly. In one example, clipping and other parameters can be derived on the encoder side and signaled to the decoder side.

[0293] Example 5

[0294] In one example, one or more classification methods may be applied to the input elements. In one example, a classification method based on gradient information may be used. In one example, a classification method based on frequency band information may be used. In one example, a classification method based on a linear function may be used. In one example, a classification method based on a nonlinear function may be used. In one example, a class merging method may be performed. In some examples, each class may have an independent set of parameters for an adaptive HDF.

[0295] Example 6

[0296] In one example, the first syntax element may be signaled to indicate whether adaptive combination of HDF is enabled. In one example, the first syntax element may be encoded and decoded by arithmetic coding and decoding. In one example, the first syntax element may be encoded and decoded with at least one context. The context may depend on the coding and decoding information of the current block or the neighboring block. The context may depend on the filter shape of at least one neighboring block.

[0297] In one example, the first syntax element may be encoded and decoded using bypass coding. In one example, the first syntax element may be binarized using a unary code, a truncated unary code, a fixed length code, an exponential Golomb code, or a truncated exponential Golomb code.

[0298] In one example, the first syntax element may be conditionally signaled. For example, the first syntax element may be signaled only when an adaptive HDF is available. The first syntax element may be encoded and decoded in a predictive manner. The first syntax element may be predicted by an on / off decision of an adaptive HDF of at least one neighboring 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, the first syntax element may be signaled for a first color component, but not for a second color component.

[0299] Example 7

[0300] In one example, a syntax element structure, such as an adaptive parameter set (APS), may contain parameters for adaptive combination of HDFs. In one example, coefficients may be contained in the APS. In one example, clipping parameters may be contained in the APS. In one example, class merging results may be contained in the APS. In one example, other parameters may be contained in the APS.

[0301] Example 8

[0302] In one example, different resources may be utilized in a HDF or adaptive HDF process.

[0303] In one example, the intermediate results can be used in the HDF or Adaptive HDF process by feeding the pre-HDF reconstruction into the HDF. In one example, the pre-DBF reconstruction can be used in the HDF or Adaptive HDF process. In one example, the intermediate results can be used in the HDF or Adaptive HDF process by feeding the pre-DBF reconstruction into the HDF.

[0304] In one example, reconstruction of reference pictures may be used for HDF or adaptive HDF processes. In one example, one or more forward reference pictures may be used. In one example, one or more backward reference pictures may be used. In one example, one or more forward and backward reference pictures may be used jointly.

[0305] In one example, the intermediate results may be used by feeding reference pictures into the HDF. In one example, one or more forward reference pictures may be used. In one example, one or more backward reference pictures may be used. In one example, one or more forward and backward reference pictures may be used jointly.

[0306] In one example, reconstructions before and / or after other codec stages may be used. In one example, intermediate results may be used by feeding reconstructions before and / or after other codec stages. In one example, resources at the current location may be used for the spatial location. In one example, resources at an adjacent location may be used for the spatial location.

[0307] Example 9

[0308] In one example, the HDF or adaptive HDF may be based on one / more previously coded frames and motion information. In one example, the previously coded frame may be a reference frame in a reference picture list (RPL) or a reference picture set (RPS) associated with the block / current slice / frame. In one example, the previously coded frame may be a short-term reference picture of the block / current slice and / or frame. In one example, the previously coded frame may be a long-term reference picture of the block / current slice and / or frame. In one example, the previously coded frame may not be a reference frame, but is still stored in a decoded picture buffer (DPB).

[0309] Example 10

[0310] In one example, at least one indicator is signaled to indicate which previously coded frame(s) to use. In one example, an indicator is signaled to indicate which reference picture list to use. In one example, the indicator may be signaled conditionally, for example, depending on how many reference pictures are included in the RPL and / or RPS. In one example, the indicator may be signaled conditionally, for example, depending on how many previously decoded pictures are included in the DPB.

[0311] Example 11

[0312] In one example, the frame to be utilized may be determined on the fly. In one example, the HDF or Adaptive HDF may obtain information from one or more previously encoded frames in the DPB. In one example, the HDF or Adaptive HDF may obtain information from one or more reference frames in List 0. In one example, the HDF or Adaptive HDF may obtain information from one or more reference frames in List 1. In one example, the HDF or Adaptive HDF may obtain information from reference frames in both List 0 and List 1.

[0313] In one example, the HDF or adaptive HDF may obtain information from a reference frame closest to the current frame, where the closest reference frame is a reference frame with a minimum picture order count (POC) distance to the current slice and / or frame. In one example, the HDF or adaptive HDF may obtain information from a reference frame with a reference index equal to K (e.g., K=0) in a reference list. In one example, K may be predefined. In one example, K may be derived on the fly based on reference picture information. In one example, K may be signaled.

[0314] In one example, the HDF or adaptive HDF may obtain information from a co-located frame. In one example, the frame to be utilized may be determined by decoding information. In one example, the frame to be utilized may be defined as the first N (e.g., N=1) most frequently used reference pictures for samples within the current slice / frame. In one example, the frame to be utilized may be defined as the first N (e.g., N=1) most frequently used reference pictures for each reference picture list (if available) for samples within the current slice / frame. In one example, the frame to be utilized may be defined as the picture with the first N (e.g., N=1) smallest POC distances / absolute POC distances relative to the current picture.

[0315] Example 12

[0316] In one example, whether to obtain information from a previously coded frame may depend on decoded information of at least one region of the block to be filtered (e.g., codec mode / statistics / characteristics). In one example, whether to obtain information from a previously coded frame may depend on the slice and / or picture type. In one example, such information may only apply to inter-coded slices and / or pictures (e.g., unidirectional inter-prediction (P) or bidirectional inter-prediction (B) slices and / or pictures). In one example, whether to obtain information from a previously coded frame may depend on the availability of a reference picture. In one example, whether to obtain information from a previously coded frame may depend on reference picture information or picture information in the DPB.

[0317] In one example, if the minimum POC distance (e.g., the minimum POC distance between a reference picture / picture in the DPB and the current picture) is greater than a threshold, obtaining information from a previously coded frame may be prohibited. In one example, whether to obtain information from a previously coded frame may depend on the temporal layer index. In one example, the information obtained from the previously coded frame may be applicable to a block with a given temporal layer index (e.g., the highest temporal layer).

[0318] In one example, if the block to be filtered contains a portion of samples that are coded in non-inter mode, HDF or adaptive HDF cannot use information from previously coded frames to filter the block. In one example, non-inter mode can be defined as intra mode. In one example, non-inter mode can be defined as a set of codec modes including but not limited to intra, intra block copy (IBC), and palette mode.

[0319] In one example, the distortion between the current block and the matching block is calculated and used to decide whether to obtain information from a previously coded frame to filter the current block. In one example, the distortion between the co-located block in the previously coded frame and the current block can be used to decide whether to obtain information from the previously coded frame to filter the current block. In one example, motion estimation can be first used to find a matching block from at least one previously coded frame. In one example, when the distortion is greater than a predefined threshold, information from the previously coded frame cannot be used.

[0320] Example 13

[0321] In one example, how and / or whether to use HDF or adaptive HDF to obtain motion information of the current block and reconstructed samples in previously coded frames and / or strips to construct / generate a reference block. In one example, a reference block can be defined as one / more reference blocks and / or those blocks in a co-located block of the current block. In one example, a reference block can be defined as those blocks in an area pointed to by a motion vector. In one example, the motion vector may be different from the decoded motion vector associated with the current block. In one example, a reference block may refer to a block whose center is located at the same horizontal and vertical position in a previously coded frame as the center of the current block in the current frame. In one example, the reference block is derived by motion estimation (e.g., by searching from previously coded frames to find a block with a specific metric that is closest to the current block). In one example, motion estimation can be performed with integer precision to avoid fractional pixel interpolation. In one example, motion estimation can be performed with fractional precision to improve the quality of the reference block.

[0322] In one example, the reference block may be derived by reusing at least one motion vector contained in the current block. In one example, the motion vector may first be rounded to integer precision to avoid fractional pixel interpolation. In one example, the reference block may be located by adding an offset determined by the motion vector to the position of the current block. In one example, the motion vector may refer to a previously coded picture containing the reference block. In one example, the motion vector may be scaled to a previously coded picture containing the reference block. In one example, the reference block and / or the co-located block may have the same size as the current block.

[0323] In one example, the reference block and / or co-located block may be larger than the current block. In one example, a reference block and / or co-located block having the same size as the current block may be first found, and then the reference block and / or co-located block may be extended at each boundary to include more samples from previously encoded samples. In one example, the size of the extended area may be signaled to the decoder or derived on the fly. In one example, the information includes two reference blocks and / or co-located blocks for the current block, one of which is from the first reference frame in list 0, and the other is from the first reference frame in list 1.

[0324] Example 14

[0325] In one example, the reconstructed samples before or after different encoding and decoding stages of the current frame are used as input to the HDF or adaptive HDF. In one example, the reconstruction before and / or after the DBF of the current frame can be used as input to the HDF or adaptive HDF. In one example, the reconstruction before and / or after the SAO and / or CCSAO of the current frame can be used as input to the HDF or adaptive HDF. In one example, the reconstruction before and / or after the HDF of the current frame can be used as input to the HDF or adaptive HDF. In one example, the reconstruction before and / or after the HDF of the current frame can be used as input to the HDF or adaptive HDF. In one example, the reconstruction before and / or after the HDF of the current frame can be used as input to the HDF or adaptive HDF. In one example, the reconstruction before and / or after other stages of the current frame can be used as input to the HDF or adaptive HDF.

[0326] Example 15

[0327] In one example, different methods can be used to determine whether and / or how to use the mapping or transformation results as input to the HDF or adaptive HDF. In one example, a specific transformation can be used to generate the input to the HDF or adaptive HDF. In one example, a discrete cosine transform (DCT) can be applied. In one example, a fast Fourier transform (FFT) can be applied. In one example, a discrete wavelet transform (DWT) can be applied. For example, other transform functions can be applied.

[0328] In one example, a specific mapping function may be used to generate the input of the HDF or adaptive HDF. In one example, a square function may be applied. In one example, a variance function may be applied. In one example, a sine function may be applied. In one example, a cosine function may be applied. In one example, other linear or nonlinear mapping functions may be applied.

[0329] Example 16

[0330] In one example, the above mentioned methods can be used in combination.

[0331] Example 17

[0332] In one example, the above-mentioned methods can be used alone.

[0333] Example 18

[0334] In one example, the above-mentioned method may be applied to different color components. In one example, the above-mentioned method may be applied only to the brightness component. In one example, the above-mentioned method may be applied only to the chrominance component. In one example, the above-mentioned method may be applied jointly to the brightness and chrominance components.

[0335] Example 19

[0336] In one example, the adaptive HDF method can be applied to any loop filtering tool, pre-processing and / or post-processing filtering method in video codec, including but not limited to DBF, BF, SAO, CCSAO, ALF, CCALF, Hadamard domain filter or any other filtering method. In one example, the adaptive HDF method can be applied to the loop filtering method. In one example, the adaptive HDF method can be applied to the loop filtering method with predefined parameters. In one example, the adaptive HDF method can be applied to the loop filtering method with online trained parameters. In one example, the adaptive HDF method can be applied to the pre-processing filtering method. In one example, the proposed adaptive HDF method can be applied to the post-processing filtering method.

[0337] Example 20

[0338] 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.

[0339] Example 21

[0340] Whether and / or how to apply the methods disclosed above can be signaled in the bitstream. In one example, they can be signaled at the sequence level / picture group level / picture level / slice level / slice group level, such as in the sequence header, picture header, SPS, VPS, DPS, decoder capability information (DCI), PPS, APS, slice header, and slice group header. In one example, they can be signaled in PB / TB / CB / PU / TU / CU / virtual pipe data unit (VPDU) / CTU / CTU row / slice / slice / sub-picture / other types of regions containing more than one sample or pixel.

[0341] Example 22

[0342] 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.

[0343] Fig.14 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 format or an 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.

[0344] System 4000 may include a codec component 4004 that may implement various codecs or coding methods described in this document. Codec component 4004 may reduce the average bit rate of the video from the input 4002 to the codec component 4004 to the output to generate the codec representation of the video. Therefore, codec technology is sometimes referred to as video compression or video transcoding technology. The output of codec component 4004 may be stored or sent via the connected communication, as shown in component 4006. The stored or transmitted bitstream representation (or codec representation) of the video received at input 4002 may be used by component 4008 to generate pixel values ​​or displayable video, which is sent to display interface 4010. The process of generating user-visible video from bitstream representation is sometimes referred to as video decompression. In addition, although some video processing operations are referred to as "coding" operations or tools, it should be understood that coding tools or operations are used in encoders, and decoders will perform corresponding decoding tools or operations of the reverse process of coding.

[0345] 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.

[0346] Fig.154106 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).

[0347] Fig.16 4200. The method 4200 includes determining to apply an HDF to samples of a picture at step 4202. The HDF process applies an average sum, a weighted sum, a linear sum, a nonlinear sum, a Wiener function, or a combination thereof. At step 4204, a conversion between visual media data and a bitstream is performed based on the HDF. According to an example, the conversion of step 4204 may include encoding at an encoder or decoding at a decoder.

[0348] 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.

[0349] Fig.17 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.

[0350] 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.

[0351] 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 outside the target device 4320, and the target device may be configured to be connected to an external display device through an interface.

[0352] The video encoder 4314 and the video decoder 4324 may operate according to a video compression standard, such as the HEVC standard, the VVC standard, and other current and / or further standards.

[0353] Fig.18 is a block diagram showing an example of a video encoder 4400, which may be Fig.17 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.

[0354] The functional components of the video encoder 4400 may include a segmentation unit 4401; a prediction unit 4402, which may include a mode selection unit 4403, a motion estimation unit 4404, a motion compensation unit 4405 and an intra-frame prediction unit 4406; 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 area 4413 and an entropy coding unit 4414.

[0355] In other examples, the video encoder 4400 may include more, fewer, or different functional components. In one 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.

[0356] Furthermore, some components, such as the motion estimation unit 4404 and the motion compensation unit 4405 , may be highly integrated but are shown separately in the example of the video encoder 4400 for explanation purposes.

[0357] The segmentation unit 4401 may segment the picture into one or more video blocks. The video encoder 4400 and the video decoder 4500 may support various video block sizes.

[0358] The mode selection unit 4403 may select one of the codec modes, for example, based on the error result, and provide the resulting intra or inter codec block to the residual generation unit 4407 to generate residual block data and 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 (e.g., sub-pixel or integer pixel precision) for the block in the case of inter prediction.

[0359] 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 (not the picture associated with the current video block).

[0360] 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.

[0361] 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.

[0362] 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. Then, the motion estimation unit 4404 may 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 the 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.

[0363] 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 a neighboring video block.

[0364] 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.

[0365] 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.

[0366] 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.

[0367] 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.

[0368] 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.

[0369] 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.

[0370] 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.

[0371] 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.

[0372] 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.

[0373] After the reconstruction unit 4412 reconstructs the video block, a loop filtering operation may be performed to reduce video block artifacts in the video block.

[0374] 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.

[0375] Fig.19 is a block diagram showing an example of a video decoder 4500, which may be Fig.17 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.

[0376] 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.

[0377] The entropy decoding unit 4501 may take out the 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 indexes, and other motion information. The motion compensation unit 4502 may determine such information, for example, by performing AMVP and Merge modes.

[0378] 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.

[0379] 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.

[0380] The motion compensation unit 4502 can use some syntax information to determine the size of blocks used to encode frames and / or slices of the encoded video sequence, partitioning information describing how each macroblock of the pictures of the encoded video sequence is partitioned, a mode indicating how each partition is encoded, one or more reference frames (and reference frame lists) for each inter-frame codec block, and other information used to decode the encoded video sequence.

[0381] 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.

[0382] 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 a decoded video for presentation on a display device.

[0383] Fig. 20 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 use the original samples of the current picture to reduce the mean square error between the original samples and the reconstructed samples by adding an offset and applying a finite impulse response (FIR) filter, respectively, 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.

[0384] 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 to the transform (T) component 4614 and the quantization (Q) component 4616 to generate quantized residual transform coefficients, which are fed to the entropy coding component 4618. The entropy coding component 4618 entropy codes and decodes 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 to the inverse quantization (IQ) component 4620, the inverse transform component 4622, and the 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 .

[0385] A list of solutions preferred by some examples is provided next.

[0386] The following solutions illustrate examples of the techniques discussed herein.

[0387] 1. A method for processing video data, comprising: determining to apply a Hadamard domain filter (HDF) process to sample points of a picture, wherein the HDF process applies an average sum, a weighted sum, a linear sum, a nonlinear sum, a Wiener function or a combination thereof; and performing conversion between visual media data and a bitstream based on the HDF process.

[0388] 2. The method of solution 1, wherein the output of the HDF is described as follows:

[0389]

[0390] where c i represents the i-th coefficient, f i represents the ith intermediate output used as an input element of the final output, N represents the total number of input elements, and G represents the final output of the HDF process.

[0391] 3. The method as described in solution 2, wherein N is greater than or equal to 2, and all of the intermediate outputs are outputs of the same first HDF process.

[0392] 4. A method as described in solution 2, wherein N is greater than or equal to 2, and one of the intermediate outputs is generated by a first HDF process, wherein another of the intermediate outputs is generated by a second HDF process, and wherein the second HDF process uses a different filtering window, different filtering parameters, or different filtering strength than the first HDF process.

[0393] 5. The method as described in any one of solutions 1 to 4, wherein the i-th intermediate output is a filtered sample point that has not been filtered by the HDF process.

[0394] 6. A method as described in any of solutions 1 to 5, wherein a clipping step is applied to the input elements, or a clipping step is applied to the final output of the HDF process.

[0395] 7. A method as described in any of solutions 1 to 6, wherein a clipping step is applied to the difference between an input element and a current reconstructed sample, or a clipping step is applied to the difference between the final output of the HDF process and the current reconstructed sample.

[0396] 8. The method according to any one of solutions 1 to 7, wherein a geometric transformation is applied to coefficients of the Wiener function, and wherein the coefficients of the Wiener function are designed to be symmetric or asymmetric.

[0397] 9. A method as described in any of solutions 1 to 8, wherein the coefficients are predefined, derived, signaled in the bitstream, or a combination thereof, and wherein the limiting parameters are predefined, derived, signaled in the bitstream, or a combination thereof.

[0398] 10. A method as described in any one of solutions 1 to 9, wherein the input elements are classified based on gradient information, frequency band information, a linear function, a nonlinear function, a class merging function or a combination thereof.

[0399] 11. A method as described in any one of solutions 1 to 10, wherein the bitstream includes a syntax element indicating whether the HDF process adopts adaptive combination, wherein the syntax element is encoded using bypass encoding or using at least one context based on encoding and decoding information of the current block or a neighboring block, and wherein when the context is based on the encoding and decoding information of the neighboring block, the context is based on the filter shape of the neighboring block.

[0400] 12. A method as described in any one of solutions 1 to 11, wherein the bitstream includes a syntax element indicating whether an adaptive combination of bilateral filtering (BF) processes is adopted, wherein the syntax element adopts bypass coding or is coded using at least one context based on coding information of the current block or a neighboring block, and wherein when the context is based on the coding information of the neighboring block, the context is based on the filter shape of the neighboring block.

[0401] 132. A method as described in any one of solutions 1 to 12, wherein the syntax elements are binarized by a unary code, a truncated unary code, a fixed-length code, an exponential Golomb code, or a truncated exponential Golomb code.

[0402] 14. A method as described in any of Solutions 1 to 13, wherein the syntax element is signaled based on whether the adaptive combination adopted by the HDF process is available, and / or wherein the syntax element is predicted based on an on / off decision of the adaptive combination adopted by the HDF process for at least one neighboring block, and / or wherein the syntax element is signaled independently for different color components, signaled and shared for different color components, or signaled for a first color component but not for a second color component.

[0403] 15. A method as described in any one of solutions 1 to 14, wherein the adaptive parameter set includes coefficients, limiting parameters, class merging results or a combination thereof.

[0404] 16. A method for processing video data, comprising: determining to apply a Hadamard domain filter (HDF) process to samples of a picture, wherein the HDF process applies an average sum, a weighted sum, a linear sum, a nonlinear sum, a Wiener function or a combination thereof to generate filtered samples; determining to apply an adaptive HDF process to combine the filtered samples with signaled parameters and / or online trained parameters; and performing conversion between visual media data and a bitstream based on the HDF and the adaptive HDF process.

[0405] 17. A method as described in any of solutions 1 to 16, wherein reconstructed samples filtered by another filter before the HDF process provide intermediate results that are input into the HDF process and / or the adaptive HDF process.

[0406] 18. The method of any one of solutions 1 to 17, wherein reconstructed samples before a deblocking filter provide the intermediate result input to the HDF process and / or the adaptive HDF process.

[0407] 19. A method as described in any one of solutions 1 to 18, wherein the reconstructed samples before the deblocking filter are filtered by the HDF process to provide the intermediate result input to the HDF process and / or the adaptive HDF process.

[0408] 20. A method as described in any one of solutions 1 to 19, wherein a reconstructed reference picture is input into the HDF process and / or the adaptive HDF process, and wherein the reconstructed reference picture includes a forward reference picture, a backward reference picture or a combination thereof.

[0409] 21. A method as described in any of solutions 1 to 20, wherein a reconstructed reference picture filtered by another filter before the HDF process provides an intermediate result input into the HDF process and / or the adaptive HDF process, and wherein the reconstructed reference picture includes a forward reference picture, a backward reference picture or a combination thereof.

[0410] 22. A method as described in any one of solutions 1 to 21, wherein the reconstructed samples and / or reconstructed pictures come from before or after the encoding and decoding stage other than the HDF process and / or the adaptive HDF process.

[0411] 23. A method as described in any one of solutions 1 to 22, wherein the intermediate result is obtained by feeding reconstructed samples and / or reconstructed pictures from before or after a coding and decoding stage other than the HDF process and / or the adaptive HDF process to another filter different from the HDF process and / or the adaptive HDF process.

[0412] 24. A method as in any one of solutions 1 to 23, wherein the airspace location is based on resources at a current location.

[0413] 25. A method as in any one of solutions 1 to 24, wherein the spatial location is based on resources at neighboring locations.

[0414] 26. A method as described in any of solutions 1 to 25, wherein the HDF process and / or the adaptive HDF process receives previously encoded and decoded frames as input.

[0415] 27. The method of any one of solutions 1 to 26, wherein the previously encoded frame comprises a reference frame in a reference picture list (RPL) or a reference picture set (RPS).

[0416] 28. The method of any one of solutions 1 to 27, wherein the previously encoded and decoded frame is not a reference frame and is stored in a decoded picture buffer.

[0417] 29. A method as described in any of solutions 1 to 28, wherein the bitstream includes an indicator indicating which previously encoded and decoded frames are used as input when filtering the current frame.

[0418] 30. A method as described in any of solutions 1 to 29, wherein the previously encoded and decoded frame used as input to the HDF process and / or the adaptive HDF process is determined based on the following information: information from frames in the decoded picture buffer, information from one or more reference picture lists, determination of the most recent reference frame, a reference frame index, determination of a co-located frame, decoding information, or a combination thereof.

[0419] 31. A method as described in any one of solutions 1 to 30, wherein whether to take information in a previously encoded and decoded frame as input to the HDF process and / or the adaptive HDF process is determined based on slice type, reference picture information, temporal layer index, whether the current picture contains samples encoded and decoded by a non-inter-frame prediction mode, distortion between the current block and the matching block, or a combination thereof.

[0420] 32. The method as described in any one of solutions 1 to 31, wherein the HDF process receives motion information of the current block and reconstructed samples of a previously encoded and decoded frame to generate a reference block.

[0421] 33. A method as described in any one of solutions 1 to 32, wherein the reference block includes samples in the area pointed to by the motion vector, samples in a block centered at the same horizontal and vertical position as the current block in the previous frame, samples in a block derived by motion estimation, samples in a block derived by using the motion vector associated with the current block, or a combination thereof.

[0422] 34. A method as described in any one of solutions 1 to 33, wherein the reference block is larger than the current block.

[0423] 35. A method as in any of solutions 1 to 34, wherein the reference block is from a first reference frame in a first list and another reference block is from the first reference frame in a second list.

[0424] 36. A method as described in any one of solutions 1 to 35, wherein the HDF process and / or the adaptive HDF process receives reconstructed samples as input, and wherein the reconstructed samples are obtained before applying a deblocking filter (DB), before applying a sample adaptive offset (SAO) filter, before applying a bilateral filter (BF), or before applying a combination thereof.

[0425] 37. A method as described in any of solutions 1 to 36, wherein discrete cosine transform (DCT), fast Fourier transform (FFT), discrete wavelet transform (DWT) or a combination thereof is used to generate inputs to the HDF process and / or the adaptive HDF process.

[0426] 38. A method as described in any one of solutions 1 to 37, wherein a square function, a variance function, a sine function, a cosine function, a linear mapping function, a nonlinear mapping function or a combination thereof is applied to generate input for the HDF process and / or the adaptive HDF process.

[0427] 39. A method as described in any one of Solutions 1 to 38, wherein the HDF process and / or the adaptive HDF process is applied only to the luminance component of the picture, or wherein the HDF process and / or the adaptive HDF process is applied only to the chrominance component of the picture, or wherein the HDF process and / or the adaptive HDF process is applied to both the luminance component and the chrominance component of the picture.

[0428] 40. A method as described in any of solutions 1 to 39, wherein the adaptive HDF process is applied to a loop filter and / or a pre-processing filter and / or a post-processing filter.

[0429] 41. A method as described in any of solutions 1 to 40, wherein the adaptive HDF process is applied to a loop filter with predefined parameters or parameters trained online.

[0430] 42. A method as described in any of solutions 1 to 41, wherein the HDF process and / or the adaptive HDF process is applied based on parameters signaled in the bitstream.

[0431] 43. A method as described in any of solutions 1 to 42, wherein the HDF process and / or the adaptive HDF process is applied based on block size, color format, single tree or dual tree partitioning, color component, stripe or picture type or a combination thereof.

[0432] 44. A method as described in any of solutions 1 to 43, wherein the converting includes encoding the visual media data into the bitstream.

[0433] 45. The method of any one of solutions 1 to 43, wherein the converting comprises decoding the visual media data from the bitstream.

[0434] 46. ​​A device for processing video data, comprising: a processor; and a non-volatile memory having instructions thereon, wherein the instructions, when executed by the processor, cause the processor to perform a method as described in any one of Solutions 1 to 45.

[0435] 47. A non-temporary 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-temporary 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 45.

[0436] 48. 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 comprises: determining to apply a Hadamard domain filter (HDF) process to samples of a picture, wherein the HDF process applies an average sum, a weighted sum, a linear sum, a non-linear sum, a Wiener function or a combination thereof; and generating the bitstream based on the determination.

[0437] 49. A method for storing a bitstream of a video, comprising: determining to apply a Hadamard domain filter (HDF) process to samples of a picture, wherein the HDF process applies an average sum, a weighted sum, a linear sum, a non-linear sum, a Wiener function, or a combination thereof; generating the bitstream based on the determination; and storing the bitstream in a non-temporary computer-readable recording medium.

[0438] 50. A method, apparatus or system as described in this patent document.

[0439] 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.

[0440] 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 from a transform and encoding, 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 knowing that certain fields may or may not be present, as described in the above solution. Similarly, the encoder may determine whether to include certain syntax fields and generate the encoded representation accordingly by including or excluding the syntax fields in the encoded representation.

[0441] The disclosed and other solutions, examples, embodiments, modules and functional operations described in this document 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 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 to be executed by a data processing device or to control 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.

[0442] 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 that store portions of one or more modules, subroutines, or code). A computer program may be deployed to execute on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

[0443] The processes or logic flows described in this document may be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows may also be performed by, and devices may also be implemented as, special purpose logic circuits, such as field programmable gate arrays (FPGAs) or application specific integrated circuits (ASICs).

[0444] Processors suitable for executing computer programs include, for example, both general 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 basic 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 (e.g., magnetic disks, magneto-optical disks, or optical disks) for storing data, or be operatively 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 need not 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 disk read-only memory (CD ROM) and digital versatile disk read-only memory (DVD-ROM) disks. The processor and memory may be supplemented by or incorporated in dedicated logic circuits.

[0445] Although the present disclosure contains many details, these details should not be interpreted as limitations on the scope of 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 the context of separate embodiments in the present disclosure may also be implemented in combination in a single embodiment. Conversely, the individual features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any appropriate sub-combination. In addition, although the above may describe features as acting in certain combinations and even initially claiming protection, in some cases, one or more features from the claimed combination may be removed from the combination, and the claimed combination may involve a sub-combination or a deformation of a sub-combination.

[0446] 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 in this disclosure should not be understood as requiring such separation in all embodiments.

[0447] Only a few implementations and examples are described, and other implementations, enhancements, and modifications may be made based on what is described and illustrated in this disclosure.

[0448] 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.

[0449] Although several embodiments are provided in the present disclosure, it should be understood that the disclosed systems and methods may be embodied 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 are not intended to 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.

[0450] 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 Hadamard domain filter (HDF) process to samples of the picture, wherein the HDF process applies an average sum, a weighted sum, a linear sum, a nonlinear sum, a Wiener function, or a combination thereof; as well as Conversion between visual media data and bitstream is performed based on the HDF process.

2. The method of claim 1, wherein the final output of the HDF process is described as follows: where c i represents the i-th coefficient, f i represents the ith intermediate output used as an input element of the final output, N represents the total number of input elements, and G represents the final output of the HDF process.

3. The method of claim 2, wherein N is greater than or equal to 2, and all of the intermediate outputs are outputs of the same first HDF process.

4. The method of claim 2, wherein N is greater than or equal to 2, and one of the intermediate outputs is generated by a first HDF process, wherein another of the intermediate outputs is generated by a second HDF process, and wherein the second HDF process uses a different filtering window, different filtering parameters, or different filtering strength than the first HDF process.

5. The method according to any one of claims 1 to 4, wherein the i-th intermediate output is a filtered sample point that has not been filtered by the HDF process.

6. A method as claimed in any one of claims 1 to 5, wherein a clipping step is applied to the input elements, or a clipping step is applied to the final output of the HDF process.

7. The method of any one of claims 1 to 6, wherein a clipping step is applied to the difference between an input element and a current reconstructed sample, or a clipping step is applied to the difference between the final output of the HDF process and the current reconstructed sample.

8. The method according to any one of claims 1 to 7, wherein a geometric transformation is applied to coefficients of the Wiener function, and wherein the coefficients of the Wiener function are designed to be symmetric or asymmetric.

9. The method of any one of claims 1 to 8, wherein coefficients are predefined, derived, signaled in the bitstream, or a combination thereof, and wherein clipping parameters are predefined, derived, signaled in the bitstream, or a combination thereof.

10. The method of any one of claims 1 to 9, wherein the input elements are classified based on gradient information, frequency band information, a linear function, a nonlinear function, a class merging function, or a combination thereof.

11. The method of any one of claims 1 to 10, wherein the bitstream includes a syntax element indicating whether the HDF process adopts adaptive combining, wherein the syntax element is encoded using bypass encoding or using at least one context based on encoding and decoding information of a current block or a neighboring block, and wherein when the context is based on the encoding and decoding information of the neighboring block, the context is based on a filter shape of the neighboring block.

12. The method of any one of claims 1 to 11, wherein the bitstream includes a syntax element indicating whether an adaptive combination of bilateral filtering is adopted, wherein the syntax element adopts bypass coding or is coded using at least one context based on coding information of a current block or a neighboring block, and wherein when the context is based on the coding information of the neighboring block, the context is based on a filter shape of the neighboring block.

13. The method of any one of claims 1 to 12, wherein the syntax elements are binarized by a unary code, a truncated unary code, a fixed length code, an exponential Golomb code, or a truncated exponential Golomb code.

14. The method of any one of claims 1 to 13, wherein the syntax element is signaled based on whether the adaptive combination adopted by the HDF process is available, and / or wherein the syntax element is predicted based on an on / off decision of the adaptive combination adopted by the HDF process for at least one neighboring block, and / or wherein the syntax element is signaled independently for different color components, signaled and shared for different color components, or signaled for a first color component but not for a second color component.

15. The method of any one of claims 1 to 14, wherein the adaptive parameter set comprises coefficients, clipping parameters, class merging results or a combination thereof.

16. A method for processing video data, comprising: Determining to apply a Hadamard domain filter (HDF) process to samples of the picture, wherein the HDF process applies an average sum, a weighted sum, a linear sum, a nonlinear sum, a Wiener function, or a combination thereof to generate filtered samples; determining to apply an adaptive HDF process to combine the filtered samples with signaled parameters and / or online trained parameters; as well as Conversion between visual media data and bitstream is performed based on the HDF and adaptive HDF processes.

17. A method as claimed in any one of claims 1 to 16, wherein reconstructed samples filtered by another filter prior to the HDF process provide intermediate results which are input into the HDF process and / or the adaptive HDF process.

18. The method of any one of claims 1 to 17, wherein reconstructed samples before a deblocking filter provide the intermediate results input to the HDF process and / or the adaptive HDF process.

19. The method of any one of claims 1 to 18, wherein the reconstructed samples before the deblocking filter are filtered by the HDF process to provide the intermediate result input to the HDF process and / or the adaptive HDF process.

20. The method of any one of claims 1 to 19, wherein a reconstructed reference picture is input into the HDF process and / or the adaptive HDF process, and wherein the reconstructed reference picture comprises a forward reference picture, a backward reference picture, or a combination thereof.

21. A method as described in any one of claims 1 to 20, wherein a reconstructed reference picture filtered by another filter before the HDF process provides an intermediate result input into the HDF process and / or the adaptive HDF process, and wherein the reconstructed reference picture includes a forward reference picture, a backward reference picture or a combination thereof.

22. The method according to any one of claims 1 to 21, wherein the reconstructed samples and / or reconstructed pictures come from before or after a coding / decoding stage other than the HDF process and / or the adaptive HDF process.

23. The method of any one of claims 1 to 22, wherein the intermediate result is obtained by feeding reconstructed samples and / or reconstructed pictures from before or after a coding stage other than the HDF process and / or the adaptive HDF process to another filter different from the HDF process and / or the adaptive HDF process.

24. The method of any one of claims 1 to 23, wherein the spatial location is based on resources at a current location.

25. The method of any one of claims 1 to 24, wherein the spatial location is based on resources at neighboring locations.

26. The method of any one of claims 1 to 25, wherein the HDF process and / or the adaptive HDF process receives as input a previously encoded or decoded frame.

27. The method of any one of claims 1 to 26, wherein the previously coded frame comprises a reference frame in a reference picture list (RPL) or a reference picture set (RPS).

28. The method of any one of claims 1 to 27, wherein the previously encoded frame is not a reference frame and is stored in a decoded picture buffer.

29. The method of any one of claims 1 to 28, wherein the bitstream includes indicators indicating which previously coded frames to use as input when filtering a current frame.

30. The method of any one of claims 1 to 28, wherein the previously encoded and decoded frame used as input to the HDF process and / or the adaptive HDF process is determined based on information from frames in the decoded picture buffer, information from one or more reference picture lists, determination of a nearest reference frame, a reference frame index, determination of a co-located frame, decoded information, or a combination thereof.

31. The method of any one of claims 1 to 30, wherein whether to take information in a previously coded frame as input to the HDF process and / or the adaptive HDF process is determined based on slice type, reference picture information, temporal layer index, whether the current picture contains samples coded by a non-inter prediction mode, distortion between a current block and a matching block, or a combination thereof.

32. The method of any one of claims 1 to 31, wherein the HDF process receives motion information of a current block and reconstructed samples of a previously coded frame to generate a reference block.

33. The method of any one of claims 1 to 32, wherein the reference block comprises samples in an area pointed to by a motion vector, samples in a block centered at the same horizontal and vertical positions as the current block in a previous frame, samples in a block derived by motion estimation, samples in a block derived by using a motion vector associated with the current block, or a combination thereof.

34. The method of any one of claims 1 to 33, wherein the reference block is larger than the current block.

35. A method as claimed in any one of claims 1 to 34, wherein the reference block is from a first reference frame in a first list and another reference block is from the first reference frame in a second list.

36. The method of any one of claims 1 to 35, wherein the HDF process and / or the adaptive HDF process receives as input reconstructed samples, and wherein the reconstructed samples are obtained before applying a deblocking filter (DB), before applying a sample adaptive offset (SAO) filter, before applying a bilateral filter (BF), or a combination thereof.

37. The method of any one of claims 1 to 36, wherein a discrete cosine transform (DCT), a fast Fourier transform (FFT), a discrete wavelet transform (DWT), or a combination thereof is used to generate inputs to the HDF process and / or the adaptive HDF process.

38. The method of any one of claims 1 to 37, wherein a square function, a variance function, a sine function, a cosine function, a linear mapping function, a nonlinear mapping function or a combination thereof is applied to generate input for the HDF process and / or the adaptive HDF process.

39. The method of any one of claims 1 to 38, wherein the HDF process and / or the adaptive HDF process is applied only to the luminance component of the picture, or wherein the HDF process and / or the adaptive HDF process is applied only to the chrominance component of the picture, or wherein the HDF process and / or the adaptive HDF process is applied to both the luminance component and the chrominance component of the picture.

40. The method of any one of claims 1 to 39, wherein the adaptive HDF process is applied to a loop filter and / or a pre-processing filter and / or a post-processing filter.

41. The method of any one of claims 1 to 40, wherein the adaptive HDF process is applied to a loop filter having predefined parameters or parameters trained online.

42. The method of any one of claims 1 to 41, wherein the HDF procedure and / or the adaptive HDF procedure is applied based on parameters signaled in a bitstream.

43. The method of any one of claims 1 to 42, wherein the HDF process and / or the adaptive HDF process is applied based on block size, color format, single tree or dual tree partitioning, color component, slice or picture type or a combination thereof.

44. The method of any one of claims 1 to 43, wherein the converting comprises encoding the visual media data into the bitstream.

45. The method of any one of claims 1 to 43, wherein the converting comprises decoding the visual media data from the bitstream.

46. ​​An apparatus for processing video data, comprising: processor; and a non-transitory memory having instructions thereon, wherein the instructions, when executed by the processor, cause the processor to perform the method of any one of claims 1 to 45.

47. A non-transitory computer-readable medium, comprising a computer program product for use by a video codec device, the computer program product comprising computer executable instructions stored on the non-transitory computer-readable medium, so that when executed by a processor, the video codec device performs the method as described in any one of claims 1 to 45.

48. 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 Hadamard domain filter (HDF) process to samples of the picture, wherein the HDF process applies an average sum, a weighted sum, a linear sum, a nonlinear sum, a Wiener function, or a combination thereof; as well as The bitstream is generated based on the determination.

49. A method for storing a bitstream of a video, comprising: Determining to apply a Hadamard domain filter (HDF) process to samples of the picture, wherein the HDF process applies an average sum, a weighted sum, a linear sum, a nonlinear sum, a Wiener function, or a combination thereof; 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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