Use of chroma-related side information for adaptive loop filters in video coding

Abstract

A mechanism for processing video data is disclosed. The mechanism includes determining chroma information as side information input into an adaptive loop filter (ALF). A conversion between the visual media data and the bitstream may then be performed based on the ALF.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to and the benefit of International Patent Application No. PCT / CN2023 / 086920 filed on April 7, 2023, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to the generation, storage, and use of digital audio video media information in file formats. BACKGROUND

[0004] Digital video accounts for the largest bandwidth use on the internet and other digital communication networks. As the number of connected user devices capable of receiving and displaying video increases, the bandwidth demand for digital video use can continue to grow. SUMMARY

[0005] A first aspect relates to a method of processing video data, comprising: determining chroma information as side information input to an adaptive loop filter (ALF); and performing a conversion between a video media data and a bitstream based on the ALF.

[0006] A second aspect relates to an apparatus of 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 one of the preceding aspects.

[0007] A third aspect relates to a non-transitory computer readable medium comprising a computer program product for use by a video coding device, the computer program product including instructions stored on the non-transitory computer readable medium that when executed by a processor cause the video coding device to perform the method of any one of the preceding aspects.

[0008] A fourth aspect relates to a non-transitory computer readable recording medium storing a bitstream of a video generated by a method performed by a video processing apparatus, wherein the method comprises: determining chroma information as side information input to an adaptive loop filter (ALF); and generating the bitstream based on the determining.

[0009] A fifth aspect relates to a method of storing a bitstream of a video, comprising: determining chroma information as side information input to an adaptive loop filter (ALF); generating the bitstream based on the determining; and storing the bitstream in a non-transitory computer readable recording medium.

[0010] A sixth aspect relates to the methods, apparatuses, or systems described in the present disclosure.

[0011] For purposes of clarity, any of the preceding embodiments can be combined with one or more other preceding embodiments to create new embodiments within the scope of the present disclosure.

[0012] These and other features will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings and claims. BRIEF DESCRIPTION OF DRAWINGS

[0013] For a more complete understanding of the present disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

[0014] Figure 1 An example of nominal vertical and horizontal positions of 4:2:2 luma and chroma samples in a picture is shown.

[0015] Figure 2 An example encoder block diagram is shown.

[0016] Figure 3 An example picture partitioned into raster scan slices is shown.

[0017] Figure 4 An example picture partitioned into rectangular scan slices is shown.

[0018] Figure 5 An example picture partitioned into tiles is shown.

[0019] Figures 6A-6C An example of a coding tree block (CTB) across picture boundaries is shown.

[0020] Figure 7 An example of intra prediction modes is shown.

[0021] Figure 8 An example of block boundaries in a picture is shown.

[0022] Figure 9 An example of pixels involved in filter usage is shown.

[0023] Figure 10 An example of filter shapes for an adaptive loop filter (ALF) is shown.

[0024] Figure 11 An example of transform coefficients supported by a 5x5 diamond filter is shown.

[0025] Figure 12 An example of relative coordinates supported by a 5x5 diamond filter is shown.

[0026] Figure 13 A block diagram showing an example video processing system is shown.

[0027] Figure 14 is a block diagram of an example video processing device.

[0028] Figure 15 is a flowchart of an example method of video processing.

[0029] Figure 16 is a block diagram illustrating an example video coding system.

[0030] Figure 17 is a block diagram illustrating an example encoder.

[0031] Figure 18 is a block diagram illustrating an example decoder.

[0032] Figure 19 is a schematic diagram of an example encoder. DETAILED DESCRIPTION

[0033] It should be understood at the outset that although illustrative implementations of one or more embodiments are provided below, the disclosed systems and / or methods can be implemented using any number of techniques, whether currently known or in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and embodiments illustrated below, including exemplary design and implementation set forth herein, but can be modified in any manner within the scope of the appended claims along with their full scope of equivalents.

[0034] The use of section headings in this disclosure is for convenience only and should not be taken as limiting the applicability or broad teachings of techniques and embodiments disclosed in each section to only the particular section in which it is disclosed. Further, the embodiments described herein are applicable to other video codec protocols and designs.

[0035] 1. Preliminary Discussion

[0036] This disclosure relates to video coding techniques. In particular, it relates to loop filters and other coding tools in image / video coding. These ideas can be applied to video codecs, such as High Efficiency Video Coding (HEVC), Versatile Video Coding (VVC), or other video coding technologies, individually or in various combinations.

[0037] 2. Abbreviations

[0038] This disclosure includes the following abbreviations: Advanced Video Coding (Recommendation ITU-T H.264|ISO / IEC 14496-10) (AVC), Cocoded Picture Buffer (CPB), Pure Random Access (CRA), Codec Tree Unit (CTU), Codec Video Sequence (CVS), Decoded Picture Buffer (DPB), Decoded Parameter Set (DPS), General Constraint Information (GCI), High-Efficiency Video Coding (also known as Recommendation ITU-T H.265|ISO / IEC 23008-2), Joint Exploration Model (JEM), Motion Constraint Piece Set (MCTS), Network Abstraction Layer (NAL), Output Layer Set (OLS), Picture Header (PH), Picture Parameter Set (PPS), Level, Layer and Grade (PTL), Picture Unit (PU), Reference Picture Resampling (RPR), Raw Byte Sequence Payload (RBSP), Supplementary Enhancement Information (SEI), Strip Header (SH), Sequence Parameter Set (SPS), Video Coding Layer (VCL), Video Parameter Set (VPS), Multifunctional Video Coding (also known as Recommendation ITU-T) H.266|ISO / IEC 23090-3, (VVC), VVC Test Model (VTM), Video Availability Information (VUI), Transform Unit (TU), Codec Unit (CU), Deblocking Filter (DF), Sample Adaptive Compensation (SAO), Adaptive Loop Filter (ALF), Codec Block Flag (CBF), Quantization Parameter (QP), Rate Distortion Optimization (RDO) and Bilateral Filter (BF).

[0039] 3. Video codec standards

[0040] Video coding standards have evolved primarily through the development of standards by the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) and the International Organization for Standardization (ISO) / International Electrotechnical Commission (IEC). ITU-T developed the H.261 and H.263 standards, ISO / IEC developed the Moving Picture Experts Group (MPEG)-1 and MPEG-4 Vision, and the two organizations jointly developed the H.262 / MPEG-2 video standard and the H.264 / MPEG-4 Advanced Video Coding (AVC) standard and the H.265 / HEVC standard[1]. Starting with H.262, video coding standards are based on a hybrid video coding architecture, which utilizes temporal prediction plus transform coding. In order to explore future video coding technologies beyond HEVC, the Joint Video Exploration Team (JVET) was jointly established by the Video Coding Experts Group (VCEG) and MPEG. JVET adopted many methods and incorporated them into a reference software called the Joint Exploration Model (JEM)[2]. When the Multifunctional Video Coding (VVC) project was officially launched, JVET was renamed the Joint Video Experts Group (JVET). VVC is a codec standard that aims to reduce the bit rate by 50% compared to HEVC. The VVC working draft and VVC Test Model (VTM) are constantly being updated.

[0041] A sample version of the VVC draft, namely the Multi-Functional Video Codec (Draft 10), can be found at: https: / / jvet-experts.org / doc_end_user / documents / 19_Teleconference / wg11 / JVET-S2001-v17.zip. A sample version of the VVC reference software, named VTM, can be found at: https: / / vcgit.hhi.fraunhofer.de / jvet-u-ee2 / VVCSoftware_VTM / - / tree / VTM-11.2.

[0042] ITU-T VCEG and ISO / IEC MPEG Joint Technical Committee (JTC) 1 / Subcommittee (SC) 29 / Working Group (WG) 11 are studying the potential need to standardize future video codec technologies with compression capabilities significantly exceeding the current VVC standard. Such future standardization could take the form of extensions to (multiple) VVC extensions or entirely new standards. These groups are conducting this exploratory activity through a joint collaborative effort called JVET to evaluate compression technology designs proposed by experts in the field. JVET has established the first exploratory experiment (EE) and is using reference software called the Enhanced Compression Model (ECM). The test model ECM is continuously updated.

[0043] 3.1 Color Space and Chromaticity Downsampling

[0044] A color space, also known as a color model (or color system), is a mathematical model that describes a range of colors as tuples of numbers, such as 3 or 4 values ​​or color components (e.g., RGB). Generally, a color space is a refinement of a coordinate system and its subspaces. For video compression, the most commonly used color spaces are Luminance, Blue Difference, and Red Difference (YCbCr) and Red, Green, and Blue (RGB).

[0045] YCbCr, Y'CbCr, or Y Pb / Cb Pr / Cr, also written as YCBCR or Y'CBCR, is a family of color spaces used as part of the color image pipeline in video and digital photography systems. Y' is the luminance component, while CB and CR are the blue and red chromaticity components, respectively. Y' (with an apostrophe) is distinguished from Y, which represents luminance, meaning that the light intensity is non-linearly encoded based on gamma-corrected RGB primary colors.

[0046] Chromaticity downsampling is a practice of encoding images by applying a lower resolution to chromaticity information compared to luminance information, taking advantage of the fact that the human visual system is less sensitive to color differences than to luminance differences. 3.1.1 4:4:4

[0048] In a 4:4:4 scheme, each of the three components of Y'CbCr has the same sampling rate. Therefore, there is no chromaticity downsampling. This scheme is sometimes used in high-end film scanners and film post-production. 3.1.2 4:2:2

[0050] In a 4:2:2 format, both chroma components are sampled at half the luminance sampling rate. The horizontal chroma resolution is halved, while the vertical chroma resolution remains unchanged. This reduces the bandwidth of the uncompressed video signal by one-third, with almost no visual difference. Figure 1 An example of the nominal vertical and horizontal positions for a 4:2:2 color format is shown. 3.1.3 4:2:0

[0052] In 4:2:0, the horizontal sampling is doubled compared to 4:1:1, but the vertical resolution is halved because the Cb and Cr channels are sampled only on each alternating row in this scheme. Therefore, the data rate is the same. Cb and Cr are downsampled by a factor of 2 in both the horizontal and vertical directions. There are three variations of the 4:2:0 scheme with different horizontal and vertical positions.

[0053] In MPEG-2, Cb and Cr are co-located horizontally. Cb and Cr are located between pixels vertically (at inter-pixel positions). In JPEG / JFIF, H.261, and MPEG-1, Cb and Cr are located at inter-pixel positions, in the middle of alternating luminance samples. In 4:2:0 DV, Cb and Cr are co-located horizontally. Vertically, they are co-located on alternating 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 / Decoding Flow of Video Codec

[0058] Figure 2 An example of a VVC encoder block diagram is shown, comprising three loop filtering blocks: Deblocking Filter (DF), Sample Adaptive Compensation (SAO), and ALF. Unlike DF, which uses predefined filters, SAO and ALF utilize the original samples of the current image, reducing the mean square error between the original and reconstructed samples by adding compensation and applying a Finite Impulse Response (FIR) filter, respectively, and by utilizing encoded / decoded side information through signal transmission compensation and filter coefficients. ALF is located in the last processing stage of each image and can be viewed as a tool attempting to capture and repair artifacts caused by previous stages.

[0059] 3.3 Definition of Video / Codec Unit

[0060] An image 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 ​​the image. A slice can be divided into one or more bricks, each brick comprising multiple 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 multiple slices of an image, or contains multiple bricks of a slice.

[0061] Two stripe modes are supported: raster scan stripe mode and rectangular stripe mode. In raster scan stripe mode, the stripe contains a sequence of slices from a raster scan of the image. In rectangular stripe mode, the stripe contains multiple tiles of the image, which together form a rectangular area of ​​the image. The tiles within the rectangular stripe are arranged in the order of the raster scan of the stripe. Figure 3An example of raster scan strip segmentation of an image (with 18×12 luminance CTUs) is shown, in which the image is divided into 12 slices and 3 raster scan strips.

[0062] Figure 4 An example of rectangular strip segmentation of an image (with 18×12 luminance CTUs) is shown, where the image is divided into 24 slices (6 slice columns and 4 slice rows) and 9 rectangular strips.

[0063] Figure 5 An example of an image divided into slices, bricks, and rectangular strips is shown, where the image is divided into 4 slices (2 slice columns and 2 slice rows), 11 bricks (the top left slice contains 1 brick, the top right slice contains 5 bricks, the bottom left slice contains 2 bricks, and the bottom right slice contains 3 bricks) and 4 rectangular strips.

[0064] 3.3.1 CTU / CTB Dimensions

[0065] In VVC, the CTU size transmitted via signaling in the Sequence Parameter Set (SPS) by 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 codec block size for each CTU. `log2_min_luma_coding_block_size_minus2` plus 2 specifies the minimum luma codec 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)CtbSizeY = 1 <<CtbLog2SizeY (7-10)

[0072] MinCbLog2SizeY = log2_min_luma_coding_block_size_minus2 + 2 (7-11)

[0073] MinCbSizeY = 1 << MinCbLog2SizeY (7-12)

[0074] MinTbLog2SizeY=2 (7-13)

[0075] MaxTbLog2SizeY = 6 (7-14)

[0076] MinTbSizeY = 1 << MinTbLog2SizeY (7-15)

[0077] MaxTbSizeY = 1 << MaxTbLog2SizeY (7-16)

[0078] PicWidthInCtbsY = Ceil( pic_width_in_luma_samples ÷ CtbSizeY ) (7-17)

[0079] PicHeightInCtbsY = Ceil( pic_height_in_luma_samples ÷ CtbSizeY )(7-18)

[0080] PicSizeInCtbsY = PicWidthInCtbsY * PicHeightInCtbsY (7-19)

[0081] PicWidthInMinCbsY = pic_width_in_luma_samples / MinCbSizeY (7-20)

[0082] PicHeightInMinCbsY = pic_height_in_luma_samples / MinCbSizeY (7-21)

[0083] PicSizeInMinCbsY = PicWidthInMinCbsY * PicHeightInMinCbsY (7-22)

[0084] PicSizeInSamplesY = pic_width_in_luma_samples * pic_height_in_luma_samples (7-23)

[0085] PicWidthInSamplesC = pic_width_in_luma_samples / SubWidthC (7-24)

[0086] PicHeightInSamplesC = pic_height_in_luma_samples / SubHeightC (7-25)

[0087] 3.3.2 CTUs in a Picture

[0088] Assume that the CTB / LCU size is indicated 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 those CTBs shown as Figures 6A-6C in, the CTB size still equals M×N. However, as Figure 6A shown, the lower boundary of the CTB is outside the picture; as Figure 6B shown, the right boundary of the CTB is outside the picture; or as Figure 6C shown, the lower boundary / right boundary of the CTB is outside the picture.

[0089] 3.4 Intra Prediction

[0090] To capture any edge direction presented in natural videos, the number of directional intra modes is extended from 33 used in HEVC to 65. The extended directional modes are as Figure 7 shown, and the planar and DC modes remain the same. These denser directional intra prediction modes apply to all block sizes as well as luminance and chrominance intra prediction.

[0091] As Figure 7As shown, the angular intra-prediction direction can be defined as clockwise from 45 degrees to -135 degrees. In VTM, for non-square blocks, multiple angular intra-prediction modes are adaptively replaced with wide-angle intra-prediction modes. The replaced modes are transmitted via signaling and remapped to the wide-angle mode index after resolution. The total number of intra-prediction modes remains constant, for example, 67, and the intra-mode encoding and decoding remain unchanged.

[0092] In HEVC, each intra-coded block has a square shape, and the length of each side of the block is a power of 2. Therefore, no division operation is needed to generate intra-prediction values ​​using DC mode. In VVC, blocks can have a rectangular shape, and in general, division is required for each block. To avoid division operations in DC prediction, only the longer side is used to calculate the average of non-square blocks.

[0093] 3.5 Inter-frame prediction

[0094] For each inter-frame prediction CU, motion parameters include motion vectors, reference picture indexes, reference picture list usage indexes, and extended information for new encoding / decoding features used in the generation of the VVC from the inter-frame prediction samples. Motion parameters can be transmitted via signaling in an explicit or implicit manner. When a CU is encoded / decoded in skip mode, the CU is associated with a PU and does not have significant residual coefficients, encoded motion vector increments, and / or reference picture indexes. Merge mode is defined as the motion parameters of the current CU being obtained from neighboring CUs, including spatial and temporal candidates and extended scheduling introduced in the VVC. Merge mode can be applied to any inter-frame prediction CU, not just skip mode. An alternative to Merge mode is explicit transmission of motion parameters, where motion vectors, corresponding reference picture indexes for each reference picture list, reference picture list usage flags, and other useful information are explicitly transmitted via signaling for each CU.

[0095] 3.6 Deblocking Filter

[0096] Deblocking filtering is an example of a loop filter in a video codec. In VVC, the deblocking filtering process is applied to CU boundaries, transform subblock boundaries, and predictive subblock boundaries. Predictive subblock boundaries include prediction unit boundaries introduced by subblock-based temporal motion vector prediction (SbTMVP) and affine modes. Transform subblock boundaries include transform unit boundaries introduced by subblock transform (SBT) and intra-fractional sub-segmentation (ISP) modes, and transforms due to the implicit partitioning of large CUs. The processing order of the deblocking filter is defined as first performing horizontal filtering on the vertical edges of the entire image, and then performing vertical filtering on the horizontal edges. This specific order allows multiple horizontal or vertical filtering processes to be applied in parallel threads. The filtering process can also be implemented per CTB with only a small processing latency.

[0097] The vertical edges in the image are first filtered. Then, the horizontal edges in the image are filtered using samples modified by the vertical edge filtering process as input. Vertical and horizontal edges in the CTB of each CTU are processed separately on a codec unit basis. The vertical edges of the codec blocks in the codec unit are filtered, starting from the edge on the left-hand side of the codec block and proceeding geometrically through the edges towards the right-hand side of the codec block. The horizontal edges of the codec blocks in the codec unit are filtered, starting from the edge on the top of the codec block and proceeding geometrically through the edges towards the bottom of the codec block.

[0098] Figure 8 This is a schematic diagram 800 of sample point 802 within an 8x8 block of sample point 804. As shown, schematic diagram 800 includes horizontal and vertical block boundaries on 8×8 grids 806 and 808, respectively. Additionally, schematic diagram 800 shows non-overlapping blocks of 8×8 sample points 810, which can be de-blocked in parallel.

[0099] 3.6.1 Boundary Decision

[0100] The filter is applied to the 8x8 block boundaries. Additionally, such boundaries must be transform block boundaries or codec sub-block boundaries, such as those obtained using affine motion prediction (ATMVP). For other boundaries, deblocking filtering is disabled.

[0101] 3.6.2 Boundary Strength Calculation

[0102] For transform block boundaries / encoder / decoder sub-block boundaries, if the boundary is located in an 8x8 grid, the boundary can be filtered, and the settings of bS[xDi][yDj] (where [xDi][yDj] represents the coordinates) of the edge are defined as in Tables 2 and 3, respectively.

[0103]

[0104] Table 2. Boundary Strength (when SPS IBC is disabled)

[0105]

[0106] Table 3. Boundary Strength (when SPS IBC is enabled)

[0107] 3.6.3 Deblocking decision for the luminance component

[0108] Figure 9 These are examples of pixels involved in the filter on / off decision and strong / weak filter selection. A wider and stronger luminance filter is used only if conditions 1, 2, and 3 are all true. Condition 1 is the "bulk condition." This condition detects whether samples on the P-side and Q-side belong to a bulk, represented by the variables bSidePisLargeBlk and bSideQisLargeBlk, respectively. bSidePisLargeBlk and bSideQisLargeBlk are defined as follows.

[0109] bSidePisLargeBlk = ((Edge type is vertical and p0 belongs to CU with width >= 32) || (Edge type is horizontal and p0 belongs to CU with height >= 32)) ? True: False

[0110] bSideQisLargeBlk = ((Edge type is vertical and q0 belongs to CU with width >= 32) || (Edge type is horizontal and q0 belongs to CU with height >= 32)) ? True: False

[0111] Based on bSidePisLargeBlk and bSideQisLargeBlk, condition 1 is defined as follows:

[0112] Condition 1 = (bSidePisLargeBlk || bSidePisLargeBlk) ? True : False

[0113] Next, if condition 1 is true, condition 2 will be further examined. First, the following variables are derived:

[0114] First, derive dp0, dp3, dq0, and dq3 using the HEVC method.

[0115] if (p side is greater than or equal to 32)

[0116] dp0=(dp0+Abs(p50-2*p40+p30)+1)>>1

[0117] dp3=(dp3+Abs(p53-2*p43+p33)+1)>>1

[0118] if (q side is greater than or equal to 32)

[0119] dq0=(dq0+Abs(q50-2*q40+q30)+1)>>1

[0120] dq3=(dq3+Abs(q53-2*q43+q33)+1)>>1

[0121] Condition 2 = (d < β)? True: False

[0122] Where d = dp0 + dq0 + dp3 + dq3.

[0123] If conditions 1 and 2 are valid, then further check whether any of the blocks uses a sub-block:

[0124]

[0125] Finally, if both conditions 1 and 2 are valid, the deblocking method will check condition 3 (the strong filter condition), which is defined as follows. In condition 3 (StrongFilterCondition), the following variables are derived:

[0126] Derive dpq using the HEVC method.

[0127] Derive sp3 = Abs(p3-p0) using the HEVC method.

[0128]

[0129] Derive sq3 = Abs(q0-q3) using the HEVC method.

[0130]

[0131] According to HEVC, StrongFilterCondition = (dpq < (β >> 2), sp3 + sq3 < (3 * β >> 5), and Abs(p0 - q0) < (5 * tC + 1) >> 1)? True: False.

[0132] 3.6.4 A more robust deblocking filter for luminance

[0133] A bilinear filter is used when a sample on either side of the boundary belongs to a large block. A sample is defined as belonging to a large block when the width of the vertical edge is >= 32 and when the height of the horizontal edge is >= 32. The bilinear filter is listed below. Then, the block boundary samples pi (i = 0 to Sp-1) and qi (j = 0 to Sq-1) in the above HEVC deblocking (pi and qi are the i-th sample in the row used for filtering the vertical edge, or the i-th sample in the column used for filtering the horizontal edge) are replaced by the following linear interpolation:

[0134] p i ′=(f i *Middle s,t +(64-f i )*P s +32)>>6), Limit to p i ±tcPD i

[0135] q j ′=(g j *Middle s,t +(64-g j )*Q s +32)>>6), Limit to q j ±tcPD j

[0136] tcPD i and tcPD j The term is the aforementioned position-related clipping, and g j f i Middle s,t P s and Q s The following is given.

[0137] 3.6.5 Color Deblocking Decision

[0138] A strong chroma filter is used on both sides of the block boundary. Here, a chroma filter is selected when the chroma edge on both sides is greater than or equal to 8 (chroma position), and the following decision is satisfied with three conditions: The first decision is for boundary strength and the size of the block. The filter can be applied when the width or height of the block orthogonally spanning the block edge is equal to or greater than 8 in the chroma sample domain. The second and third decisions are essentially the same as the HEVC luminance deblocking decision, which are the on / off decision and the strong filter decision, respectively.

[0139] In the first decision, the boundary strength (bS) is modified for chroma filtering, and conditions are checked sequentially. If a condition is met, the remaining conditions with lower priority are skipped. Chroma deblocking is performed when bS equals 2, or when bS equals 1 when a large block boundary is detected. The second and third conditions are essentially the same as the HEVC luma strong filter decision below.

[0140] In the second condition, d is derived using the HEVC luminance deblocking method. The second condition will be true when d is less than β. In the third condition, StrongFilterCondition is derived as follows:

[0141] Derive dpq using the HEVC method;

[0142] Derive sp3 = Abs(p3-p0) using the HEVC method; and

[0143] The derivation of sq3 = Abs(q0-q3) follows the HEVC method.

[0144] According to the HEVC design, StrongFilterCondition = (dpq < (β >> 2), sp3 + sq3 < (β >> 3), and Abs(p0 - q0) < (5 * tC + 1) >> 1).

[0145] 3.6.6 Strong Deblocking Filter for Chroma

[0146] The strong deblocking filter for chroma is defined as follows:

[0147] p2′=(3*p3+2*p2+p1+p0+q0+4)>>3

[0148] p1′=(2*p3+p2+2*p1+p0+q0+q1+4)>>3

[0149] p0′=(p3+p2+p1+2*p0+q0+q1+q2+4)>>3

[0150] The example chroma filter performs deblocking on a 4x4 chroma sample grid.

[0151] 3.6.7 Location-related amplitude limiting

[0152] Position-dependent limiting (tcPD) is applied to the output samples of a brightness filtering process involving modifications to strong and long filters at the boundaries of 7, 5, and 3 samples. Assuming a quantization error distribution, the limiting value can be increased for samples expected to have higher quantization noise, thus expecting a greater deviation between the reconstructed sample values ​​and the true sample values.

[0153] For each P or Q boundary filtered by an asymmetric filter, a position-related threshold table is selected from two tables (e.g., Tc7 and Tc3 listed below) that serve as edge information for the decoder, based on the results of the decision-making process:

[0154] Tc7={6,5,4,3,2,1,1}; Tc3={6,4,2};

[0155] tcPD=(Sp==3)? Tc3:Tc7;

[0156] tcQD=(Sq==3)? Tc3:Tc7;

[0157] For P or Q boundaries filtered by a short symmetric filter, apply a lower-amplitude position correlation threshold:

[0158] Tc3 = {3, 2, 1};

[0159] After defining the threshold, the filtered p'i and q'i sample values ​​are limited according to the tcP and tcQ limiting values:

[0160] p”i=Clip3(p’i+tcPi,p’i–tcPi,p’i);

[0161] q”j=Clip3(q’j+tcQj,q’j–tcQj,q’j);

[0162] Where p'i and q'i are the filtered sample values, p”i and q”j are the output sample values ​​after clipping, and tcPi is the clipping threshold derived from the VVC tc parameters, tcPD, and tcQD. The function Clip3 is the clipping function as specified in VVC.

[0163] 3.6.8 Sub-block Removal and Adjustment

[0164] To enable parallel-friendly deblocking using both long filters and sub-block deblocking, the long filter is restricted to modifying a maximum of 5 samples on the side using sub-block deblocking (AFFINE or ATMVP or decoder-side motion vector refinement (DMVR)), as shown in the long filter's brightness control. Extending this, sub-block deblocking is adjusted such that sub-block boundaries on the 8x8 grid near the CU or implicit TU boundaries are restricted to modifying a maximum of two samples on each side.

[0165] The following applies to sub-block boundaries that are not aligned with the CU boundary.

[0166]

[0167] Where edge = 0 corresponds to the CU boundary, edge = 2 or orthogonalLength-2 corresponds to the sub-block boundary 8 samples away from the CU boundary, etc. If implicit partitioning of TU is used, then implicit TU is true.

[0168] 3.7 Sample point adaptive compensation

[0169] Sample Adaptive Compensation (SAO) is applied to the reconstructed signal after the deblocking filter using compensation specified by the encoder for each CTB. The video encoder first decides whether to apply the SAO process to the current slice. If SAO is applied to a slice, each CTB is 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 compensation to pixels in each category. SAO operations include Edge Compensation (EO) and Band Compensation (BO), where EO uses edge attributes to classify pixels in SAO types 1 through 4, and BO uses pixel intensity to classify pixels in SAO type 5. Each applicable CTB has SAO parameters including sao_merge_left_flag, sao_merge_up_flag, SAO type, and four compensations. If sao_merge_left_flag equals 1, the current CTB will reuse the SAO type and compensation of the left CTB. If sao_merge_up_flag equals 1, the current CTB will reuse the SAO type and compensation of the upper CTB.

[0170] SAO type Sample adaptive offset type to be used Number of classes 0 None 0 1 One-dimensional 0-degree pattern edge compensation 4 2 One-dimensional 90-degree pattern edge compensation 4 3 One-dimensional 135-degree pattern edge compensation 4 4 One-dimensional 45-degree pattern edge compensation 4 5 With compensation 4

[0171] Table 4. SAO Type Specifications

[0172] 3.8 Adaptive Loop Filter

[0173] Adaptive Loop Filtering (ALF) for video encoding and decoding minimizes the mean square error between the original and decoded samples using Wiener-based adaptive filters. ALF is located at the last processing stage of each picture and can be considered a tool for capturing and repairing artifacts from previous stages. Appropriate filter coefficients are determined by the encoder and explicitly transmitted to the decoder via the signal. To achieve better encoding and decoding efficiency, especially for high-resolution video, local adaptation is used for the luminance signal by applying different filters to different regions or blocks in the picture. In addition to filter adaptation, filter on / off control at the codec tree unit (CTU) level also contributes to improved encoding and decoding efficiency. Syntactically, filter coefficients are sent in a picture-level header called the adaptive parameter set, and the filter on / off flags of the CTUs are interleaved at the CTU level in the stripe data. This syntax design not only supports picture-level optimization but also achieves low encoding latency.

[0174] 3.8.1 Signaling of Parameters

[0175] According to the ALF design in VTM, filter coefficients and clipping indices are carried in the ALF Adaptive Parameter Set (APS). The ALF APS can include up to eight chroma filters and a luma filter set with up to 25 filters. An index is also included for each of the 25 luma categories. Categories with the same index share the same filters. By merging different categories, the number of bits required to represent the filter coefficients is reduced. The absolute values ​​of the filter coefficients are represented using zero-order exponent Golomb code followed by a sign bit for non-zero coefficients. When clipping is enabled, a two-bit fixed-length code is also used for each filter coefficient transmitted via signal transmission as a clipping index. The decoder can use up to eight ALF APSs simultaneously.

[0176] The filter control syntax elements for ALF in VTM include two types of information. First, the ALF on / off flag is transmitted via signaling at the sequence, picture, strip, and CTB levels. Chroma ALF can only be enabled at the picture and strip levels if Luminance ALF is enabled at the corresponding level. Second, if ALF is enabled at the picture, strip, and CTB levels, filter usage information is transmitted via signaling at that level. If all strips within a picture use the same APS, the referenced ALF APS ID is encoded / decoded at the strip or picture level. Luminance components can reference up to 7 ALF APSs, and chroma components can reference 1 ALF APS. For Luminance CTB, an index is transmitted via signaling, indicating which ALF APS or offline-trained set of luminance filters to use. For Chroma CTB, the index indicates which filter in the referenced APS to use.

[0177] The data syntax elements of the ALF associated with the luminance component in VTM are listed below:

[0178]

[0179]

[0180] `alf_luma_filter_signal_flag` equal to 1 specifies the set of luminance filters transmitted via signaling. `alf_luma_filter_signal_flag` equal to 0 specifies that no luminance filter set is transmitted via signaling. `alf_luma_clip_flag` equal to 0 specifies that linear adaptive loop filtering is applied to the luminance component. `alf_luma_clip_flag` equal to 1 specifies that nonlinear adaptive loop filtering can be applied to the luminance component. `alf_luma_num_filters_signalled_minus1` plus 1 specifies the number of adaptive loop filter classes whose luminance coefficients can be transmitted via signaling. The value of `alf_luma_num_filters_signalled_minus1` must be in the range of 0 to NumAlfFilters-1 (inclusive). `alf_luma_coeff_delta_idx[filtIdx]` specifies the index of the adaptive loop filter luminance coefficient increment of the filter class transmitted via signaling, indicated by `filtIdx` in the range of 0 to NumAlfFilters-1. When alf_luma_coeff_delta_idx[filtIdx] does not exist, it is presumed 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] must be in the range from 0 to alf_luma_num_filters_signalled_minus1 (inclusive).

[0181] `alf_luma_coeff_abs[sfIdx][j]` specifies the absolute value of the j-th coefficient of the luminance filter transmitted through the signal, indicated by `sfIdx`. When `alf_luma_coeff_abs[sfIdx][j]` does not exist, it is presumed to be equal to 0. The value of `alf_luma_coeff_abs[sfIdx][j]` must be in the range of 0 to 128 (inclusive). `alf_luma_coeff_sign[sfIdx][j]` specifies the sign of the j-th luminance coefficient of the filter indicated by `sfIdx`, as follows:

[0182] If alf_luma_coeff_sign[sfIdx][j] equals 0, the corresponding luminance filter coefficient has a positive value.

[0183] Otherwise (alf_luma_coeff_sign[sfIdx][j] equals 1), the corresponding luminance filter coefficient has a negative value.

[0184] When alf_luma_coeff_sign[sfIdx][j] does not exist, it is presumed to be equal to 0.

[0185] `alf_luma_clip_idx[sfIdx][j]` specifies the limiting index to be used before multiplying the limiting value by the j-th coefficient of the luminance filter transmitted through the signal, indicated by `sfIdx`. When `alf_luma_clip_idx[sfIdx][j]` does not exist, it is presumed to be equal to 0. The codec tree unit syntax elements of the ALF associated with the luminance component in the VTM are listed below:

[0186]

[0187] `alf_ctb_flag[cIdx][xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY]` equal to 1 indicates that the adaptive loop filter is applied to the codec tree block of the codec tree unit at the luma position (xCtb, yCtb) for the color component indicated by cIdx. `alf_ctb_flag[cIdx][xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY]` equal to 0 indicates that the adaptive loop filter is not applied to the codec tree block of the codec tree unit at the luma position (xCtb, yCtb) for the color component indicated by cIdx.

[0188] When `alf_ctb_flag[cIdx][xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY]` does not exist, it is presumed to be equal to 0. `alf_use_aps_flag` equal to 0 specifies that a fixed set of filters from a fixed filter set is applied to the luma CTB. `alf_use_aps_flag` equal to 1 specifies that a set of filters from the APS is applied to the luma CTB. When `alf_use_aps_flag` does not exist, it is presumed 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` must be in the range of 0 to `sh_num_alf_aps_ids_luma-1` (inclusive). When `alf_luma_prev_filter_idx` does not exist, it is presumed to be equal to 0.

[0189] The variable AlfCtbFiltSetIdxY[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY], which represents the filter set index of the luminance CTB at a specified location (xCtb, yCtb), is derived as follows:

[0190] If alf_use_aps_flag equals 0, then AlfCtbFiltSetIdxY[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is set to equal alf_luma_fixed_filter_idx.

[0191] Otherwise, AlfCtbFiltSetIdxY[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY] is set to equal 16 + alf_luma_prev_filter_idx.

[0192] alf_luma_fixed_filter_idx specifies the fixed filter applied to the lumen CTB. The value of alf_luma_fixed_filter_idx must be in the range of 0 to 15 (inclusive).

[0193] Based on the VTM-based ALF design, the ECM-based ALF design further introduces the concept of alternative filter sets into the luminance filter. The luminance filter is trained for multiple alternatives / rounds based on the updated luminance CTU ALF on / off decisions for each alternative / round. In this way, multiple filter sets will be associated with each trained alternative, and the class merging results of each filter set can be different. Each CTU can select the optimal filter set via RDO, and the relevant alternative information will be transmitted via signal transmission. The data syntax elements of the ALF associated with the luminance component in the ECM are listed below:

[0194]

[0195]

[0196] `alf_luma_num_alts_minus1` incremented by 1 specifies the number of alternative filter sets for the luminance component. The value of `alf_luma_num_alts_minus1` must 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 luminance component of the alternative luminance filter set with index `altIdx`. `alf_luma_clip_flag[altIdx]` equal to 1 specifies that nonlinear adaptive loop filtering can be applied to the luminance component of the alternative luminance filter set with index `altIdx`. `alf_luma_num_filters_signalled_minus1[altIdx]` incremented by 1 specifies the number of adaptive loop filter classes through which the luminance coefficients can be transmitted in the alternative luminance filter set with index `altIdx`. The value of alf_luma_num_filters_signalled_minus1[altIdx] must be in the range of 0 to NumAlfFilters-1 (inclusive).

[0197] `alf_luma_coeff_delta_idx[altIdx][filtIdx]` specifies the index of the adaptive loop filter luminance coefficient increment for the filter class indicated by `filtIdx`, ranging from 0 to `NumAlfFilters-1`, for use with an alternative luminance filter set having the index `altIdx`. `alf_luma_coeff_delta_idx[filtIdx][altIdx]` is presumed to be 0 if it does not exist. 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]` must 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 luminance filter transmitted through the signal, indicated by the `sfIdx` of the alternative luminance filter set with index `altIdx`. When `alf_luma_coeff_abs[altIdx][sfIdx][j]` does not exist, it is presumed to be equal to 0. The value of `alf_luma_coeff_abs[altIdx][sfIdx][j]` must be in the range of 0 to 128 (inclusive).

[0198] alf_luma_coeff_sign[altIdx][sfIdx][j] specifies the sign of the j-th luminance coefficient of the filter indicated by sfIdx of the alternative luminance filter set with index altIdx, as follows:

[0199] If alf_luma_coeff_sign[altIdx][sfIdx][j] equals 0, then the corresponding luminance filter coefficient has a positive value.

[0200] Otherwise (alf_luma_coeff_sign[altIdx][sfIdx][j] equals 1), the corresponding luminance filter coefficient has a negative value.

[0201] When alf_luma_coeff_sign[altIdx][sfIdx][j] does not exist, it is presumed to be equal to 0.

[0202] `alf_luma_clip_idx[altIdx][sfIdx][j]` specifies the limiting index to be used before multiplying the j-th coefficient of the luminance filter transmitted through the signal, indicated by `sfIdx` of the alternative luminance filter set with index `altIdx`. When `alf_luma_clip_idx[altIdx][sfIdx][j]` does not exist, it is presumed to be equal to 0. The codec tree unit syntax elements of the ALF associated with the luminance component in the ECM are listed below:

[0203]

[0204] `alf_ctb_luma_filter_alt_idx[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY]` specifies the index of the alternative luma filter for the codec tree block applied to the luma component of the codec tree unit at luma location (xCtb, yCtb). When `alf_ctb_luma_filter_alt_idx[xCtb>>CtbLog2SizeY][yCtb>>CtbLog2SizeY]` does not exist, it is presumed to be equal to 0.

[0205] 3.8.2 Filter Shape

[0206] In JEM, there are a maximum of three diamond filter shapes (e.g., Figure 10 The square (shown) can be selected for the luma component. At the image level, the filter shape used for the luma component is indicated by a signal transmission index. Each square represents a sample, and Ci (i = 0–6 (left), 0–12 (middle), 0–20 (right)) represents the coefficient to be applied to the sample. For the chroma component in the image, a 5×5 rhombus shape is always used. In VVC, a 7×7 rhombus shape is always used for luma, while a 5×5 rhombus shape is always used for chroma.

[0207] 3.8.3 Classification of ALF

[0208] Each 2×2 (or 4×4) block is classified into one of 25 categories. The classification index C is based on its directionality D and activity. The quantization value is derived as follows:

[0209]

[0210] To calculate D and First, the gradients in the horizontal, vertical, and two diagonal directions are calculated using a one-dimensional Laplacian:

[0211]

[0212] 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 coordinates (i,j). Then, the maximum and minimum values ​​of the gradients D in the horizontal and vertical directions are set as follows:

[0213]

[0214] Furthermore, the maximum and minimum values ​​of the gradients in the two diagonal directions are set as follows:

[0215]

[0216] To derive the values ​​of directionality D, these values ​​are compared with each other and with two thresholds t1 and t2:

[0217] Step 1. If and If both are true, then D is set to 0.

[0218] Step 2. If If so, continue from step 3; otherwise, continue from step 4.

[0219] Step 3. If Then D is set to 2; otherwise, D is set to 1.

[0220] Step 4. If Then D is set to 4; otherwise, D is set to 3.

[0221] The activity value A is calculated as:

[0222]

[0223] A is further quantized to the range of 0 to 4 (inclusive), and the quantized value is represented as For the two chromaticity components in the image, no classification method is applied; that is, a single set of ALF coefficients is applied to each chromaticity component.

[0224] 3.8.4 Geometric Transformation of Filter Coefficients

[0225] Before filtering each 2×2 block, geometric transformations (such as rotation or diagonal and vertical flips) are applied to the filter coefficients f(k,l) associated with the coordinates (k,l), based on the gradient values ​​calculated for that block. This is equivalent to applying these transformations to samples in the filter's support region. The idea is to make different blocks to which ALF is applied more similar by aligning the orientations of the different blocks.

[0226] Three geometric transformations are introduced: diagonal, vertical flip, and rotation.

[0227] Diagonal: f D (k,l)=f(l,k),

[0228] Vertical flip: f V (k,l)=f(k,Kl-1),

[0229] Rotation: f R (k,l)=f(Kl-1,k).

[0230] Where K is the size of the filter, and 0 ≤ k, l ≤ K⁻¹ are the coefficient coordinates, such that position (0, 0) is in the upper left corner and position (K⁻¹, K⁻¹) is in the lower right corner. Based on the gradient values ​​calculated for this block, the transform is applied to the filter coefficients f(k, l). The relationship between the transform and the four gradients in the four directions is summarized in Table 5. Figure 11 The transformation coefficients for each position based on a 5x5 rhombus are shown.

[0231] Gradient value Transform g d2 g d1 and g h g v ]]> No transform g d2 g d1 and g v g h ]]> Diagonal g d1 g d2 and g h g v ]]> Vertical flip g d1 g d2 g v g h ]]> Rotation

[0232] Table 5. Mapping of gradients and transformations for a block

[0233] 3.8.5 Filtering Process

[0234] On the decoder side, when ALF is enabled for a block, each sample R(i,j) within the block is filtered, producing sample values ​​R′(i,j) as shown below, where L represents the filter length, f m,n Let f(k,l) represent the filter coefficients, and let f(k,l) represent the decoded filter coefficients.

[0235]

[0236] Figure 12 An example of relative coordinates used for a 5x5 diamond filter is shown, assuming the current sample point's coordinates (i, j) are (0, 0). Sample points at different coordinates, filled with the same color, are multiplied by the same filter coefficients.

[0237] 3.8.6 Nonlinear Filtering Reconstruction

[0238] Linear filtering can be reconstructed into the following expression without affecting encoding / decoding efficiency:

[0239]

[0240] Where w(i,j) are the same filter coefficients.

[0241] VVC introduces nonlinearity by using a simple limiting function to reduce the influence of neighboring sample values ​​when the difference between the neighboring sample value (I(x+i,y+j)) and the current sample value being filtered (I(x,y)) is too large, thus making ALF more efficient. More specifically, the ALF filter is modified as follows:

[0242]

[0243] Where K(d,b) = min(b,max(-b,d)) is the limiting function, and k(i,j) is the limiting parameter, which depends on the (i,j) filter coefficients. The encoder performs optimization to find the optimal k(i,j).

[0244] A limiting parameter k(i,j) is specified for each ALF filter, and each filter coefficient transmits a limiting value via signal transmission. This means that a maximum of 12 limiting values ​​can be transmitted via signal transmission in the bitstream for each luminance filter, and a maximum of 6 limiting values ​​can be transmitted via signal transmission in the bitstream for each chrominance filter. To limit signaling costs and encoder complexity, only 4 fixed values ​​are used, which are the same for both inter-frame and intra-frame stripes.

[0245] Because the variance of local differences in luminance is typically higher than that in chrominance, two different sets of filters are applied for luminance and chrominance. The maximum sample value in each set (here, 1024 for a 10-bit bit depth) is also introduced so that clipping can be disabled when unnecessary. The four values ​​are selected by roughly uniformly dividing the full range of luminance sample values ​​(encoded and decoded on 10 bits) and the chrominance range from 4 to 1024 in the logarithmic domain. More precisely, the luminance clipping value table is obtained using the following formula:

[0246] Where M = 2 10 And N = 4

[0247] Similarly, the chromaticity limit table is obtained from the following formula:

[0248] Where M = 2 10 N=4, A=4

[0249] 3.9 Bilateral Loop Filter

[0250] 3.9.1 Bilateral Image Filter

[0251] Bilateral image filters are nonlinear filters that smooth noise while preserving edge structure. Bilateral filtering is a technique where the filter weights decrease not only with the distance between samples but also with the increase in intensity difference. This improves the smoothing of overly smoothed edges. The weights are defined as follows:

[0252]

[0253] Where Δx and Δy are the distances in the horizontal and vertical directions, respectively, and ΔI is the intensity difference between the sample points.

[0254] The edge-preserving denoising bilateral filter employs low-pass Gaussian filters for both the domain and range filters. The domain low-pass Gaussian filter assigns higher weights to pixels spatially closer to the center pixel. The range low-pass Gaussian filter assigns higher weights to pixels similar to the center pixel. Combining the range and domain filters, the bilateral filter at edge pixels becomes a slender Gaussian filter oriented along the edge and significantly reduced in the gradient direction. This is why the bilateral filter can smooth noise while preserving edge structure.

[0255] 3.9.2 Bilateral Filters in Video Encoding and Decoding

[0256] Bilateral filters in video encoding and decoding are encoding and decoding tools used for VVC [2]. The filter acts as a loop filter in parallel with the Sample Adaptive Compensation (SAO) filter. Both the bilateral filter and the SAO act on the same input samples, each filter produces compensation, and these compensations are then added to the input samples to produce output samples, which are then clipped before proceeding to the next stage. Spatial filtering intensity σ d Determined by the block size, smaller blocks are filtered more strongly, and the intensity of the filter σ is... r The strength of the filter is determined by the quantization parameter, where a higher QP results in a stronger filter. Only the four nearest samples are used, therefore the filtered sample strength I... F It can be calculated as

[0257]

[0258] Among them I C The intensity of the central sample point, ΔI A =I A -I C This represents the intensity difference between the central sample point and the sample point above it. ΔI B ΔI L and ΔI R These represent the intensity differences between the central sample point and the sample points below, to the left, and to the right, respectively.

[0259] 4. Technical problems solved by the disclosed embodiments

[0260] The example design of the Adaptive Loop Filter (ALF) in video encoding and decoding has the following problems.

[0261] In the example ALF design, only the chroma reconstruction prior to the current stage is used to filter the chroma samples. However, other valuable chroma-related edge information can potentially be utilized, such as samples prior to the deblocking filter (DBF), sample adaptive compensation (SAO), cross-component SAO (CCSAO), bilateral filter (BF), predicted samples, residual information, segmentation information, quantization parameter (QP) information, and boundary strength used by the DBF (DBF-BS), etc.

[0262] 5. List of solutions and implementation examples

[0263] To address the aforementioned problems, methods outlined below are disclosed. These embodiments should be considered as examples for explaining general concepts and should not be interpreted in a narrow sense. Furthermore, these embodiments can be applied individually or in any combination.

[0264] It should be noted that the disclosed method can be used as a loop filter or post-processing.

[0265] In this disclosure, a video unit can refer to a sequence, picture, subpicture, strip, CTU, block, and / or region. A video unit may include one color component or multiple color components.

[0266] In this disclosure, a processing unit may refer to a sequence, image, sub-image, strip, CTU, block, region, or sample. A processing unit may include one or more color components.

[0267] 1) The method of using chromaticity-related edge information in ALF is proposed. For example, chromaticity information is the edge information input into ALF.

[0268] a. It is proposed to use the chromaticity reconstruction prior to DBF / SAO / CCSAO / BF as the edge information of ALF.

[0269] a) In one example, isochromatic reconstruction prior to DBF / SAO / CCSAO / BF can be used.

[0270] b) In one example, neighboring chromaticity reconstruction can be used before DBF / SAO / CCSAO / BF.

[0271] c) In one example, the chromaticity reconstruction prior to DBF / SAO / CCSAO / BF can be used as the input source for at least one extended tap of the chromaticity online training filter.

[0272] d) In one example, the chromaticity reconstruction prior to DBF / SAO / CCSAO / BF can be used as the input source for at least one spatial tap of the chromaticity online training filter.

[0273] e) In one example, the chromaticity reconstruction prior to DBF / SAO / CCSAO / BF can be used as an input source for classification.

[0274] 1. In one example, the chromaticity reconstruction prior to DBF / SAO / CCSAO / BF can be used as the input source for classification of the chromaticity online training filter.

[0275] b. A proposal was made to use chromaticity prediction samples as edge information for ALF.

[0276] a) In one example, isochromaticity can be used to predict sample points.

[0277] b) In one example, neighboring chromaticity prediction samples can be used.

[0278] c) In one example, chromaticity prediction samples can be used as the input source for at least one extended tap of the chromaticity online training filter.

[0279] d) In one example, chromaticity prediction samples can be used as the input source for at least one spatial tap of the chromaticity online training filter.

[0280] e) In one example, chromaticity prediction samples can be used as an input source for classification.

[0281] 1. In one example, chromaticity prediction samples can be used as the input source for classification of the chromaticity online training filter.

[0282] f) Chromaticity prediction samples can be modified before being provided to ALF.

[0283] 1. Modification can be filtering.

[0284] 2. Modifications can be made by downsampling or upsampling.

[0285] 3. Modifications can include limiting / shifting.

[0286] c. It proposes using chromaticity residuals as edge information in ALF.

[0287] a) In one example, the isotopic chromaticity residual value can be used.

[0288] b) In one example, neighboring chromaticity residuals can be used.

[0289] c) In one example, the chromaticity residual value can be used as the input source for at least one extended tap of the chromaticity online training filter.

[0290] d) In one example, the chromaticity residual value can be used as the input source for at least one spatial tap of the chromaticity online training filter.

[0291] e) In one example, the chromaticity residual value can be used as an input source for classification.

[0292] 1. In one example, the chroma residual value can be used as the input source for classification of the chroma online training filter.

[0293] f) The chromaticity residual value can be modified before being provided to ALF.

[0294] 1. Modification can be filtering.

[0295] 2. Modifications can be made by downsampling or upsampling.

[0296] 3. Modifications can include limiting / shifting.

[0297] d. It is proposed to use chromaticity segmentation information as the edge information of ALF.

[0298] a) In one example, chromaticity segmentation information can represent block size / shape / location, block average / maximum / minimum / variance, or other information.

[0299] b) In one example, chroma segmentation information can be used as the input source for at least one extended tap of the chroma online training filter.

[0300] c) In one example, chroma segmentation information can be used as the input source for at least one spatial tap of the chroma online training filter.

[0301] d) In one example, chromaticity segmentation information can be used for classification.

[0302] 1. In one example, chroma segmentation information can be used for classification of chroma online training filters.

[0303] e) In one example, chroma segmentation information can be used for filter training.

[0304] 1. In one example, chromaticity segmentation information can be used to train an online luminance training filter.

[0305] 2. In one example, chroma segmentation information can be used to train an online chroma training filter.

[0306] f) In one example, chroma segmentation information may involve a filtering process.

[0307] e. Proposed using chromatic QP information as edge information in ALF.

[0308] a) In one example, QP information can represent QP information at the level of picture / strip / piece / block or other levels.

[0309] b) In one example, chromaticity QP information can be used for classification.

[0310] 1. In one example, chroma QP information can be used for classification of chroma online training filters.

[0311] c) In one example, chromaticity QP information can be used for filter training.

[0312] 1. In one example, chroma QP information can be used to train an online chroma training filter.

[0313] 2. In one example, chromaticity QP information can be used to train an online luminance training filter.

[0314] d) In one example, the luminance / chrominance QP information may involve a filtering process.

[0315] f. It is proposed to use chromatic boundary strength (DBF-BS) information as the edge information of ALF.

[0316] a) In one example, boundary strength information can be generated by DBF or other methods.

[0317] b) In one example, the same DBF-BS can be used.

[0318] c) In one example, a neighboring DBF-BS can be used.

[0319] d) In one example, chromaticity boundary intensity information can be used for classification.

[0320] 1. In one example, chromaticity boundary intensity information can be used for classification of chromaticity online training filters.

[0321] e) In one example, chromaticity boundary intensity information can be used for filter training.

[0322] 1. In one example, chromaticity boundary intensity information can be used to train an online luminance training filter.

[0323] 2. In one example, chromaticity boundary intensity information can be used to train an online chromaticity training filter.

[0324] f) In one example, the luminance / chrominance boundary intensity information can be involved in the filtering process of the ALF's online chrominance training filter.

[0325] 2) In this disclosure, “chromaticity” can refer to a chromaticity component (such as Cb or Cr).

[0326] 3) In this disclosure, “chromaticity” can represent at least two chromaticity components (such as Cb and Cr).

[0327] a. For example, "chromaticity" information can be derived from Cb and Cr.

[0328] 4) In one example, the disclosed method can be used for post-processing and / or pre-processing.

[0329] 5) In one example, the above methods can be used in combination.

[0330] 6) Optionally, the above methods can be used alone.

[0331] 7) In one example, the proposed / described side information utilization method can be applied to any loop filtering tool, preprocessing or postprocessing filtering method in video encoding and decoding (including but not limited to ALF / Cross-Component ALF (CCALF) or any other filtering method).

[0332] a. In one example, the proposed side information utilization method can be applied to a loop filtering method.

[0333] a) In one example, the proposed edge information utilization method can be applied to ALF.

[0334] b) In one example, the proposed edge information utilization method can be applied to CCALF.

[0335] c) In one example, the proposed edge information utilization method can be applied to SAO.

[0336] d) In one example, the proposed edge information utilization method can be applied to CCSAO.

[0337] e) In one example, the proposed side information utilization method can be applied to a bilateral filter (BF).

[0338] f) In one example, the proposed side information utilization method can be applied to a Hadamard transform domain filter (HTDF).

[0339] g) Alternatively, the proposed side information utilization method can be applied to other loop filtering methods.

[0340] b. In one example, the proposed side information utilization method can be applied to a preprocessing filtering method.

[0341] c. In one example, the proposed side information utilization method can be applied to a post-processing filtering method.

[0342] 8) In the above examples, a video unit can refer to a sequence / picture / subpicture / strip / piece / code-decode tree unit (CTU) / CTU line / CTU group / code-decode unit (CU) / prediction unit (PU) / transform unit (TU) / code-decode tree block (CTB) / code-decode block (CB) / prediction block (PB) / transform block (TB) / any other region containing more than one luminance or chrominance sample / pixel.

[0343] 9) Whether and / or how the methods disclosed above can be applied to transmit signals in a bitstream.

[0344] a. In one example, whether and / or how the methods disclosed above can be applied can be transmitted via signaling at the sequence level / picture group level / picture level / strip level / piece group level, such as in the sequence header / picture header / SPS / VPS / DPS / decoder capability information (DCI) / PPS / APS / strip header / piece group header.

[0345] b. In one example, whether and / or how the methods disclosed above can be applied to signal transmission at PB / TB / CB / PU / TU / CU / Virtual Pipeline Data Unit (VPDU) / CTU / CTU line / strip / piece / sub-image / other types of areas containing more than one sample point or pixel.

[0346] 10) Whether and / or how to apply the methods disclosed above may depend on the encoded / decoded information, such as block size, color format, single / dual tree segmentation, color components, and stripe / image type.

[0347] 6. References

[0348] [1] J.Strom, P.Wennersten, J.Enhorn, D.Liu, K.Andersson and R.Sjoberg, "Bilateral Loop Filterin Combination with SAO," in proceeding of IEEE PictureCoding Symposium (PCS), Nov. 2019. Figure 13This is a block diagram illustrating an example video processing system 4000 in which various embodiments 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, such as 8 or 10-bit multi-component pixel values, or it may be received in a compressed or encoded format. Input 4002 may represent a network interface, a peripheral bus interface, or a storage interface. Examples of network interfaces include wired interfaces (such as Ethernet, Passive Optical Networking (PON), etc.) and wireless interfaces (such as Wi-Fi or cellular interfaces).

[0349] System 4000 may include an encoding / decoding component 4004 capable of implementing the various encoding / decoding or coding methods described in this disclosure. Encoding / decoding component 4004 can reduce the average bit rate from the video input 4002 to the output of encoding / decoding component 4004 to produce an encoded / decoded representation of the video. Encoding / decoding techniques are therefore sometimes referred to as video compression or video transcoding techniques. The output of encoding / decoding component 4004 may be stored or transmitted via a communication connection such as that represented by component 4006. The bitstream (or encoded / decoded) representation of the video received at input 4002, whether stored or communicated, may be used by component 4008 to generate pixel values ​​or displayable video to be transmitted to display interface 4010. The process of generating a user-viewable video from the bitstream representation is sometimes referred to as video decompression. Furthermore, although some video processing operations are referred to as “encoding / decoding” operations or tools, it is understood that encoding / decoding tools or operations are used by the encoder, and the corresponding decoding tools or operations that inversely convert the encoding / decoding results will be performed by the decoder.

[0350] Examples of peripheral bus interfaces or display interfaces may include Universal Serial Bus (USB), High Definition Multimedia Interface (HDMI), or DisplayPort, etc. Examples of storage interfaces include Serial Advanced Technology Attachment (SATA), Peripheral Component Interconnect (PCI), Integrated Drive Electronics (IDE), etc. The embodiments described in this disclosure can be embodied in a variety of electronic devices, such as mobile phones, laptops, smartphones, or other devices capable of performing digital data processing and / or video display.

[0351] Figure 14This is a block diagram of an example video processing apparatus 4100. Apparatus 4100 can be used to implement one or more methods described herein. Apparatus 4100 can be embodied in a smartphone, tablet, computer, Internet of Things (IoT) receiver, etc. Apparatus 4100 may include one or more processors 4102, one or more memories 4104, and video processing circuitry 4106. The processors(multiple) processors 4102 may be configured to implement one or more methods described herein. The memories(multiple) memories 4104 may be used to store data and code for implementing the methods and embodiments described herein. The video processing circuitry 4106 may be used to implement some embodiments described herein in hardware circuitry. In some embodiments, the video processing circuitry 4106 may be at least partially included in the processor 4102, for example, a graphics coprocessor.

[0352] Figure 15 This is a flowchart of an example method 4200 for video processing. Method 4200 includes: in step 4202, determining chroma information as side information input to an adaptive loop filter (ALF). In step 4204, performing a conversion between visual media data and a bitstream based on the ALF. According to the example, the conversion in step 4204 may include encoding at an encoder or decoding at a decoder.

[0353] It should be noted that method 4200 can be implemented in an apparatus for processing video data, including a processor and a non-transitory memory having instructions thereon, such as a video encoder 4400, a video decoder 4500, and / or an encoder 4600. In this case, the instructions, when executed by the processor, cause the processor to perform method 4200. Furthermore, method 4200 can be executed by a non-transitory computer-readable medium, which includes a computer program product for use by a video encoding / decoding device. The computer program product includes computer-executable instructions stored on the non-transitory computer-readable medium, such that when the computer-executable instructions are executed by a processor, the video encoding / decoding device performs method 4200.

[0354] Figure 16 This is a block diagram illustrating an example video encoding / decoding system 4300 that can utilize embodiments of the present disclosure. The video encoding / decoding system 4300 may include a source device 4310 and a target device 4320. The source device 4310 generates encoded video data, and this source device 4310 may be referred to as a video encoding device. The target device 4320 can decode the encoded video data generated by the source device 4310, and this target device 4320 may be referred to as a video decoding device.

[0355] Source device 4310 may include video source 4312, video encoder 4314, and input / output (I / O) interface 4316. Video source 4312 may include sources such as video capture devices, interfaces for receiving video data from video content providers, and / or computer graphics systems for generating video data, or combinations thereof. Video data may include one or more pictures. Video encoder 4314 encodes the video data from video source 4312 to generate a bitstream. The bitstream may include a sequence of bits forming a codec representation of the 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 transmitter. Encoded video data may be transmitted directly to target device 4320 via network 4330 through I / O interface 4316. Encoded video data may also be stored on storage medium / server 4340 for access by target device 4320.

[0356] Target device 4320 may include I / O interface 4326, video decoder 4324, and display device 4322. I / O interface 4326 may include a receiver and / or a modem. I / O interface 4326 may acquire encoded video data from source device 4310 or storage medium / server 4340. Video decoder 4324 may decode the encoded video data. Display device 4322 may display the decoded video data to a user. Display device 4322 may be integrated with target device 4320 or may be external to target device 4320, wherein target device 4320 may be configured to interface with an external display device.

[0357] The video encoder 4314 and the video decoder 4324 can operate according to video compression standards, such as HEVC, VVC and other existing and / or further standards.

[0358] Figure 17 This is a block diagram illustrating an example of a video encoder 4400, which can be... Figure 16 The system 4300 shown includes a video encoder 4314. The video encoder 4400 can be configured to perform any or all embodiments of this disclosure. The video encoder 4400 includes multiple functional components. The embodiments described in this disclosure can be shared among the various components of the video encoder 4400. In some examples, a processor can be configured to perform any or all embodiments described in this disclosure.

[0359] 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 4413; and an entropy coding unit 4414.

[0360] 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 can perform prediction in an IBC mode, where at least one reference picture is the picture in which the current video block is located.

[0361] Furthermore, some components such as the motion estimation unit 4404 and the motion compensation unit 4405 can be highly integrated, but for illustrative purposes, they are shown separately in the example of the video encoder 4400.

[0362] The segmentation unit 4401 can segment an image into one or more video blocks. The video encoder 4400 and the video decoder 4500 can support various video block sizes.

[0363] The mode selection unit 4403 can select one of several encoding / decoding modes (intra-frame encoding / decoding or inter-frame encoding / decoding) based, for example, on the error result, and provide the resulting intra-frame or inter-frame encoded block to the residual generation unit 4407 to generate residual block data, and to the reconstruction unit 4412 to reconstruct the coded block for use as a reference image. In some examples, the mode selection unit 4403 can select an intra-frame / inter-frame joint prediction (CIIP) mode, where prediction is based on inter-frame prediction signals and intra-frame prediction signals. In the case of inter-frame prediction, the mode selection unit 4403 can also select the resolution of the motion vector for the block (e.g., sub-pixel precision or integer pixel precision).

[0364] To perform inter-frame prediction on the current video block, motion estimation unit 4404 can generate motion information for the current video block by comparing one or more reference frames from buffer 4413 with the current video block. Motion compensation unit 4405 can determine the predicted video block for the current video block based on the motion information and decoded samples of images from buffer 4413 other than the image associated with the current video block.

[0365] The motion estimation unit 4404 and the motion compensation unit 4405 can perform different operations on the current video block, for example, depending on whether the current video block is in an I-band, P-band, or B-band.

[0366] In some examples, motion estimation unit 4404 can perform unidirectional prediction on the current video block, and can search for reference images in list 0 or list 1 to find a reference video block for the current video block. Motion estimation unit 4404 can then generate a reference index indicating the reference image containing the reference video block in list 0 or list 1, and a motion vector indicating the spatial displacement between the current video block and the reference video block. Motion estimation unit 4404 can output the reference index, prediction direction indicator, and motion vector as motion information for the current video block. Motion compensation unit 4405 can generate a predicted video block for the current block based on the reference video block indicated by the motion information of the current video block.

[0367] In other examples, motion estimation unit 4404 can perform bidirectional prediction on the current video block. Motion estimation unit 4404 can search for reference images in list 0 to find a reference video block for the current video block, and can also search for reference images in list 1 to find another reference video block for the current video block. Motion estimation unit 4404 can then generate reference indices indicating the reference images containing the reference video blocks in lists 0 and 1, and motion vectors indicating the spatial displacement between the reference video blocks and the current video block. Motion estimation unit 4404 can output the reference index and motion vector of the current video block as motion information for the current video block. Motion compensation unit 4405 can generate a predicted video block for the current video block based on the reference video blocks indicated by the motion information of the current video block.

[0368] In some examples, the motion estimation unit 4404 can output a complete set of motion information for use in the decoder's decoding process. In some examples, the motion estimation unit 4404 may not output a complete set of motion information for the current video. Instead, the motion estimation unit 4404 can reference the motion information of another video block to transmit the motion information of the current video block via a signal. For example, the motion estimation unit 4404 may determine that the motion information of the current video block is sufficiently similar to the motion information of neighboring video blocks.

[0369] In one example, the motion estimation unit 4404 may indicate a value to the video decoder 4500 in the syntax structure associated with the current video block, which indicates that the current video block has the same motion information as another video block.

[0370] In another example, motion estimation unit 4404 may identify another video block and motion vector difference (MVD) in the 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. 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.

[0371] As discussed above, the video encoder 4400 can transmit motion vectors via signaling in a predictive manner. Two examples of predictive signaling techniques that can be implemented by the video encoder 4400 include Advanced Motion Vector Prediction (AMVP) and Merge Pattern Signaling.

[0372] Intra-prediction unit 4406 can perform intra-prediction on the current video block. When intra-prediction unit 4406 performs intra-prediction on the current video block, it can generate prediction data for the current video block based on the decoded samples of other video blocks in the same frame. The prediction data for the current video block can include the predicted video block and various syntax elements.

[0373] The residual generation unit 4407 can generate residual data for the current video block by subtracting (or more) predicted video blocks from the current video block. The residual data for the current video block may include residual video blocks corresponding to different sample components of the samples in the current video block.

[0374] In other examples, such as in skip mode, the current video block may have no residual data, and the residual generation unit 4407 may not perform subtraction operations.

[0375] The transform processing unit 4408 can generate one or more transform coefficient video blocks for the current video block by applying one or more transforms to the residual video blocks associated with the current video block.

[0376] After the transform processing unit 4408 generates a transform coefficient video block associated with the current video block, the quantization unit 4409 can 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.

[0377] The inverse quantization unit 4410 and the inverse transform unit 4411 can apply inverse quantization and inverse transform to the transform coefficient video block respectively to reconstruct the residual video block from the transform coefficient video block. The reconstruction unit 4412 can add the reconstructed residual video block to the corresponding samples of one or more predicted video blocks generated by the prediction unit 4402 to produce a reconstructed video block associated with the current block for storage in the buffer 4413.

[0378] After the video block is reconstructed by reconstruction unit 4412, a loop filtering operation can be performed to reduce video block artifacts in the video block.

[0379] Entropy encoding unit 4414 can receive data from other functional components of video encoder 4400. When entropy encoding unit 4414 receives data, it can perform one or more entropy encoding operations to generate entropy-encoded data and output a bitstream including the entropy-encoded data.

[0380] Figure 18 This is a block diagram illustrating an example of a video decoder 4500, which can be... Figure 16 The system 4300 shown includes a video decoder 4324. The video decoder 4500 can be configured to perform any or all embodiments of this disclosure. In the example shown, the video decoder 4500 includes multiple functional components. The embodiments described in this disclosure can be shared among the various components of the video decoder 4500. In some examples, a processor can be configured to perform any or all embodiments described in this disclosure.

[0381] 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, a reconstruction unit 4506, and a buffer 4507. In some examples, the video decoder 4500 can perform a decoding process that is generally contrasted with the encoding process described with respect to the video encoder 4400.

[0382] The entropy decoding unit 4501 can retrieve the encoded bitstream. The encoded bitstream may include entropy-encoded video data (e.g., encoded video data blocks). The entropy decoding unit 4501 can decode the entropy-encoded video data, and based on the entropy-decoded video data, the motion compensation unit 4502 can determine motion information, including motion vectors, motion vector precision, reference image list index, and other motion information. The motion compensation unit 4502 can determine this information, for example, by executing AMVP and Merge modes.

[0383] The motion compensation unit 4502 can generate motion compensation blocks, possibly performing interpolation based on an interpolation filter. The identifier of the interpolation filter to be used, with sub-pixel accuracy, can be included in the syntax element.

[0384] The motion compensation unit 4502 can use interpolation filters, such as those used by the video encoder 4400 during the encoding of a video block, to calculate interpolations for sub-integer pixels of a reference block. The motion compensation unit 4502 can determine the interpolation filter used by the video encoder 4400 based on the received syntax information, and the motion compensation unit 4502 can use the interpolation filter to generate a prediction block.

[0385] The motion compensation unit 4502 may use some syntax information to determine the size of the blocks used to encode (multiple) frames and / or (multiple) stripes of the encoded video sequence, segmentation information describing how each macroblock of the image of the encoded video sequence is segmented, a mode indicating how each segment is encoded, one or more reference frames (and a list of reference frames) for each inter-frame codec block, and other information for decoding the encoded video sequence.

[0386] Intra-prediction unit 4503 can use, for example, an intra-prediction mode received in the bitstream to form prediction blocks from spatially adjacent blocks. Inverse quantization unit 4504 inverse quantizes (i.e., dequantizes) the quantized video block coefficients provided in the bitstream and decoded by entropy decoding unit 4501. Inverse transform unit 4505 applies the inverse transform.

[0387] The reconstruction unit 4506 can add the residual block to the corresponding prediction block generated by the motion compensation unit 4502 or the intra-frame prediction unit 4503 to form a decoded block. If necessary, a deblocking filter can also be used to filter the decoded block to remove block artifacts. The decoded video block is then stored in a buffer 4507, which provides a reference block for subsequent motion compensation / intra-frame prediction and also generates decoded video for presentation on a display device.

[0388] Figure 19 This is a schematic diagram of an example encoder 4600. Encoder 4600 is suitable for implementing VVC techniques. Encoder 4600 includes three loop filters: a deblocking filter (DF) 4602, a sample adaptive compensation (SAO) 4604, and an adaptive loop filter (ALF) 4606. Unlike DF 4602, which uses predefined filters, SAO 4604 and ALF 4606 utilize the original samples of the current image, respectively, by adding compensation and by applying a finite impulse response (FIR) filter, and by utilizing the encoded / decoded side information through signal transmission compensation and filter coefficients to reduce the mean square error between the original and reconstructed samples. ALF 4606 is located in the last processing stage of each image and can be thought of as a tool to attempt to capture and repair artifacts caused by previous stages.

[0389] The encoder 4600 also includes an intra-frame prediction component 4608 and a motion estimation / compensation (ME / MC) component 4610 configured to receive input video. The intra-frame prediction component 4608 is configured to perform intra-frame prediction, while the ME / MC component 4610 is configured to perform inter-frame prediction using a reference image obtained from a reference image buffer 4612. Residual blocks from inter-frame or intra-frame prediction are fed into a transform (T) component 4614 and a quantization (Q) component 4616 to generate quantized residual transform coefficients, which are then fed into an entropy encoding / decoding component 4618. The entropy encoding / decoding component 4618 entropy-encodes and decodes the prediction results and quantized transform coefficients and transmits them toward a video decoder (not shown). The quantization component output from the quantization component 4616 can be fed into an inverse quantization (IQ) component 4620, an inverse transform component 4622, and a reconstruction (REC) component 4624. REC component 4624 can output images to DF 4602, SAO 4604 and ALF 4606 to filter them before they are stored in reference image buffer 4612.

[0390] The following provides a list of preferred solutions as examples.

[0391] The following solutions illustrate examples of the embodiments discussed herein.

[0392] 1. A method for processing video data, comprising: determining chroma information as side information input to an adaptive loop filter (ALF); and performing a conversion between visual media data and a bitstream based on said ALF.

[0393] 2. The method according to Solution 1, wherein the chromaticity information includes chromaticity reconstruction prior to applying a deblocking filter (DBF), sample adaptive compensation (SAO), cross-component SAO (CCSAO), bilateral filter (BF), or a combination thereof.

[0394] 3. The method according to any one of solutions 1-2, wherein the chromaticity reconstruction includes isotopic chromaticity reconstruction or neighboring chromaticity reconstruction.

[0395] 4. The method according to any one of solutions 1-3, wherein the chroma reconstruction is used as an input source for at least one extended tap of the chroma online training filter, at least one spatial tap of the chroma online training filter, or a combination thereof.

[0396] 5. The method according to any one of solutions 1-4, wherein the chromaticity reconstruction is used as an input source for classification of the chromaticity online training filter.

[0397] 6. The method according to any one of solutions 1-5, wherein the chromaticity information includes chromaticity prediction samples prior to the application of DBF, SAO, CCSAO, BF, or a combination thereof.

[0398] 7. The method according to any one of solutions 1-6, wherein the chromaticity prediction sample points include co-location chromaticity prediction sample points, neighboring chromaticity prediction sample points, or a combination thereof.

[0399] 8. The method according to any one of solutions 1-7, wherein the chromaticity prediction samples are used as input sources for at least one extended tap of the chromaticity online training filter, at least one spatial tap of the chromaticity online training filter, or a combination thereof.

[0400] 9. The method according to any one of solutions 1-8, wherein the chromaticity prediction samples are used as input sources for classification of the chromaticity online training filter.

[0401] 10. The method according to any one of solutions 1-9, wherein the chromaticity prediction samples are modified by filtering, downsampling, upsampling, limiting, shifting, or a combination thereof before being input into the ALF.

[0402] 11. The method according to any one of solutions 1-10, wherein the chromaticity information includes chromaticity residual values.

[0403] 12. The method according to any one of solutions 1-11, wherein the chromaticity residual value includes co-position chromaticity residual value, adjacent chromaticity residual value, or a combination thereof.

[0404] 13. The method according to any one of solutions 1-12, wherein the chromaticity residual value is used as an input source for at least one extended tap of the chromaticity online training filter, at least one spatial tap of the chromaticity online training filter, or a combination thereof.

[0405] 14. The method according to any one of solutions 1-13, wherein the chromaticity residual value is used as an input source for classification of the chromaticity online training filter.

[0406] 15. The method according to any one of solutions 1-14, wherein the chromaticity residual value is modified by filtering, downsampling, upsampling, limiting, shifting, or a combination thereof before being input into the ALF.

[0407] 16. The method according to any one of solutions 1-15, wherein the chromaticity information includes chromaticity segmentation information.

[0408] 17. The method according to any one of solutions 1-16, wherein the chromaticity segmentation information includes block size, block shape, block position, block average, block maximum, block minimum, block variance, block value, or a combination thereof.

[0409] 18. The method according to any one of solutions 1-17, wherein the chroma segmentation information is used as an input source for at least one extended tap of the chroma online training filter, at least one spatial tap of the chroma online training filter, or a combination thereof.

[0410] 19. The method according to any one of solutions 1-18, wherein the chroma segmentation information is used as an input source for classification of the chroma online training filter.

[0411] 20. The method according to any one of solutions 1-19, wherein the chroma segmentation information is used to train an online luminance training filter, to train an online chroma training filter, and involves a filtering process or a combination thereof.

[0412] 21. The method according to any one of solutions 1-20, wherein the chromaticity information includes chromaticity quantification parameter (QP) information.

[0413] 22. The method according to any one of solutions 1-21, wherein the chroma QP information is obtained from a picture, strip, slice, block or a combination thereof.

[0414] 23. The method according to any one of solutions 1-22, wherein the chroma QP information is used as an input source for classification of the chroma online training filter.

[0415] 24. The method according to any one of solutions 1-23, wherein the chromaticity QP information is used to train an online luminance training filter, to train an online chromaticity training filter, and involves a filtering process or a combination thereof.

[0416] 25. The method according to any one of solutions 1-24, wherein the chromaticity information includes chromaticity deblocking filter boundary strength (DBF-BS) information.

[0417] 26. The method according to any one of solutions 1-24, wherein the chromaticity DBF-BS information includes co-located DBF-BS, neighboring DBF-BS, or a combination thereof.

[0418] 27. The method according to any one of solutions 1-26, wherein the chroma DBF-BS information is used as an input source for classification of the chroma online training filter.

[0419] 28. The method according to any one of solutions 1-27, wherein the chromaticity DBF-BS information is used to train an online luminance training filter, to train an online chromaticity training filter, and relates to a filtering process or a combination thereof.

[0420] 29. 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 the method described in any one of solutions 1-28.

[0421] 30. A non-transitory computer-readable medium comprising a computer program product for use by a video codec device, the computer program product including computer-executable instructions stored on the non-transitory computer-readable medium such that when the computer-executable instructions are executed by a processor, the video codec device performs the method described in any one of solutions 1-28.

[0422] 31. A non-transitory computer-readable recording medium storing a bitstream of video generated by a method performed by a video processing apparatus, wherein the method includes: determining chroma information as side information input to an adaptive loop filter (ALF); and generating the bitstream based on the determination.

[0423] 32. A method for storing a bitstream of video, comprising: determining chroma information as side information input to an adaptive loop filter (ALF); generating the bitstream based on the determination; and storing the bitstream in a non-transitory computer-readable recording medium.

[0424] 33. A method, apparatus or system described in this disclosure.

[0425] In the described solution, the encoder conforms to the format rules by generating a codec representation based on those rules. In the described solution, the decoder parses the syntax elements in the codec representation using known information about their presence or absence, based on the format rules, to produce the decoded video.

[0426] In this disclosure, the term "video processing" can refer to video encoding, video decoding, video compression, or video decompression. For example, a video compression algorithm can be applied during the conversion from a pixel representation of a video to a corresponding bitstream representation, and vice versa. For example, the bitstream representation of the current video block can correspond to bits at co-positions or propagated at different positions in the bitstream defined by the syntax. For example, a macroblock can be encoded based on the error residual value after transformation and encoding / decoding, and can also use bits from the header and other fields in the bitstream. Furthermore, during the conversion, the decoder can parse the bitstream based on this determination, knowing that some fields may or may not be present, as described in the solutions above. Similarly, the encoder can determine whether to include or exclude specific syntax fields, and generate the codec representation accordingly by including or excluding syntax fields from the codec representation.

[0427] The disclosed and other solutions, examples, embodiments, modules, and functional operations described herein can be implemented in digital electronic circuits, or in computer software, firmware, or hardware, including the structures disclosed herein and their structural equivalents, or in combinations thereof. The disclosed and other embodiments can be implemented as one or more computer program products, i.e., one or more computer program instruction modules encoded on a computer-readable medium for execution by a data processing apparatus or for controlling the operation of the data processing apparatus. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a storage device, a material composition affecting machine-readable propagation signals, or a combination thereof. The term "data processing apparatus" includes all means, devices, and machines for processing data, including, for example, a programmable processor, a computer, or multiple processors or computers. In addition to hardware, the apparatus may also include code that creates an execution environment for the computer program in question, for example, code constituting processor firmware, a protocol stack, a database management system, an operating system, or a combination thereof. Propagation signals are artificially generated signals, such as machine-generated electrical signals, optical signals, or electromagnetic signals, which are generated to encode information for transmission to a suitable receiver device.

[0428] Computer programs (also known as programs, software, software applications, scripts, or code) can be written in any programming language, including compiled or interpreted languages, and can be deployed in any form, including standalone programs or modules, components, subroutines, or other units suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can 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, or in multiple co-located files (e.g., files storing one or more modules, subroutines, or code portions). A computer program can be deployed to execute on one computer or on multiple computers located at a single site or distributed across multiple sites and interconnected by a communications network.

[0429] The processing and logic flows described in this disclosure can be executed by one or more programmable processors that execute one or more computer programs to perform functions by manipulating input data and generating outputs. The processing and logic flows can also be executed by dedicated logic circuitry, and the apparatus can be implemented as dedicated logic circuitry, such as a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC).

[0430] Processors suitable for executing computer programs include, for example, general-purpose and special-purpose microprocessors, and any one or more processors in any type of digital computer. Typically, the processor receives instructions and data from read-only memory or random access memory, or both. The basic components of a computer are a processor that executes instructions and one or more storage devices that store the instructions and data. Typically, a computer will also include one or more mass storage devices for storing data, such as magnetic disks, magneto-optical disks, or optical disks. However, a computer does not necessarily have such devices. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and storage devices, including, for example, semiconductor storage devices such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable hard disks; magneto-optical disks; and CD-ROMs and DVD-ROMs. The processor and memory may be supplemented by or incorporated into special-purpose logic circuitry.

[0431] While this disclosure contains numerous details, these details should not be construed as limiting any subject matter or the scope of the claims, but rather as descriptions of features specific to particular embodiments of this disclosure. Certain features described in the context of individual embodiments in this disclosure may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented separately in multiple embodiments, or in any suitable sub-combination. Furthermore, although features may function in certain combinations as described above, and even were originally claimed in this manner, in some cases one or more features in a claimed combination may be removed from that combination, and the claimed combination may be for sub-combinations or variations thereof.

[0432] Similarly, although operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring such operations to be performed sequentially in the particular order or sequence shown, or requiring all shown operations to be performed in order to achieve the desired result. Furthermore, the partitioning of various system components in the embodiments described in this disclosure should not be construed as requiring such partitioning in all embodiments.

[0433] Only a few implementations and examples are described, and other implementations, improvements and variations may be made based on what is described and shown in this disclosure.

[0434] When there are no intermediate components other than a line, trace, or other medium between the first and second components, the first component is directly coupled to the second component. When there are intermediate components other than a line, trace, or other medium between the first and second components, the first component is indirectly coupled to the second component. The term "coupled" and its variations include both direct and indirect coupling. The use of the term "approximately" means including a range of ±10% of the following figures, unless otherwise specified.

[0435] While several embodiments have been provided in this 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 this disclosure. The examples presented herein are to be considered 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 into another system, or certain features may be omitted or not implemented.

[0436] Furthermore, the technologies, systems, subsystems, and methods described and illustrated as discrete or separate in the various embodiments can be combined or integrated with other systems, modules, technologies, or methods without departing from the scope of this disclosure. Other items shown or discussed as couplings can be directly connected or indirectly coupled or communicated through some interface, device, or intermediate component, whether electrical, mechanical, or otherwise. Those skilled in the art can identify examples of other changes, substitutions, and modifications, which can be made without departing from the spirit and scope of this disclosure.

Claims

1. A method for processing video data, comprising: The chromaticity information is determined as the side information input into the adaptive loop filter ALF; as well as The conversion between visual media data and bitstream is performed based on the ALF.

2. The method according to claim 1, wherein, The chromaticity information includes chromaticity reconstruction prior to the application of a deblocking filter (DBF), sample adaptive compensation (SAO), cross-component SAO, cross-component SAO, bilateral filter (BF), or a combination thereof.

3. The method according to claim 1 or 2, wherein, The chromaticity reconstruction includes isotopic chromaticity reconstruction.

4. The method according to any one of claims 1-3, wherein, The chromaticity reconstruction includes neighboring chromaticity reconstruction.

5. The method according to any one of claims 1-4, wherein, The chromaticity reconstruction is used as the input source for at least one extended tap of the chromaticity online training filter.

6. The method according to any one of claims 1-5, wherein, The chromaticity reconstruction serves as the input source for at least one spatial tap of the chromaticity online training filter.

7. The method according to any one of claims 1-6, wherein, The chromaticity reconstruction is used as the input source for classification of the chromaticity online training filter.

8. The method according to any one of claims 1-7, wherein, The chromaticity information includes chromaticity prediction samples before applying a deblocking filter (DBF), sample adaptive compensation (SAO), cross-component SAO, cross-component SAO, bilateral filter (BF), or a combination thereof.

9. The method according to any one of claims 1-8, wherein, The chromaticity prediction samples include isotopic chromaticity prediction samples.

10. The method according to any one of claims 1-9, wherein, The chromaticity prediction sample points include neighboring chromaticity prediction sample points.

11. The method according to any one of claims 1-10, wherein, The chromaticity prediction samples are used as the input source for at least one extended tap of the chromaticity online training filter.

12. The method according to any one of claims 1-11, wherein, The chromaticity prediction samples are used as the input source for at least one spatial tap of the chromaticity online training filter.

13. The method according to any one of claims 1-12, wherein, The chromaticity prediction samples are used as the input source for classification of the online chromaticity training filter.

14. The method according to any one of claims 1-13, wherein, The chromaticity prediction samples are modified by filtering, downsampling, upsampling, limiting, shifting, or a combination thereof before being input into the ALF.

15. The method according to any one of claims 1-14, wherein, The chromaticity information includes chromaticity residual values.

16. The method according to any one of claims 1-15, wherein, The chromaticity residual values ​​include isotopic chromaticity residual values.

17. The method according to any one of claims 1-16, wherein, The chromaticity residual values ​​include neighboring chromaticity residual values.

18. The method according to any one of claims 1-17, wherein, The chromaticity residual value is used as the input source for at least one extended tap of the chromaticity online training filter.

19. The method according to any one of claims 1-18, wherein, The chromaticity residual value is used as the input source for at least one spatial tap of the chromaticity online training filter.

20. The method according to any one of claims 1-19, wherein, The chromaticity residual values ​​are used as the input source for classification of the chromaticity online training filter.

21. The method according to any one of claims 1-20, wherein, The chromaticity residual values ​​are modified by filtering, downsampling, upsampling, limiting, shifting, or a combination thereof before being input into the ALF.

22. The method according to any one of claims 1-21, wherein, The chromaticity information includes chromaticity segmentation information.

23. The method according to any one of claims 1-22, wherein, Chromaticity segmentation information includes block size, block shape, block position, block average, block maximum, block minimum, block variance, block value, or a combination thereof.

24. The method according to any one of claims 1-23, wherein, The chromaticity segmentation information is used as the input source for at least one extended tap of the chromaticity online training filter.

25. The method according to any one of claims 1-24, wherein, The chromaticity segmentation information is used as the input source for at least one spatial tap of the chromaticity online training filter.

26. The method according to any one of claims 1-25, wherein, The chromaticity segmentation information is used as the input source for classification of the online chromaticity training filter.

27. The method according to any one of claims 1-26, wherein, The chromaticity segmentation information is used to train an online luminance training filter, to train an online chromaticity training filter, involves a filtering process, or a combination thereof.

28. The method according to any one of claims 1-27, wherein, The chromaticity information includes the chromaticity quantification parameter QP information.

29. The method according to any one of claims 1-28, wherein, The chromaticity QP information is obtained from images, strips, slices, blocks, or combinations thereof.

30. The method according to any one of claims 1-29, wherein, The chromaticity QP information is used as the input source for classification of the chromaticity online training filter.

31. The method according to any one of claims 1-30, wherein, The chromaticity QP information is used to train the luminance online training filter and / or to train the chromaticity online training filter.

32. The method according to any one of claims 1-31, wherein, The chromaticity QP information involves a filtering process.

33. The method according to any one of claims 1-32, wherein, The chromaticity information includes the chromaticity deblocking filter boundary strength (DBF-BS) information.

34. The method according to any one of claims 1-33, wherein, The chromaticity DBF-BS information includes isotopic DBF-BS.

35. The method according to any one of claims 1-34, wherein, The chromaticity DBF-BS information includes neighboring DBF-BS.

36. The method according to any one of claims 1-35, wherein, The chromaticity DBF-BS information is used as the input source for classification of the chromaticity online training filter.

37. The method according to any one of claims 1-36, wherein, The chromaticity DBF-BS information is used to train the luminance online training filter and / or to train the chromaticity online training filter.

38. The method according to any one of claims 1-37, wherein, The chromaticity DBF-BS information involves a filtering process.

39. An apparatus for processing video data, comprising: processor; and a non-transitory memory thereon having instructions, wherein the instructions, when executed by the processor, cause the processor to perform the method of any one of claims 1-38.

40. A non-transitory computer-readable medium comprising a computer program product for use by a video codec apparatus, the computer program product including computer-executable instructions stored on the non-transitory computer-readable medium such that when the computer-executable instructions are executed by a processor, the video codec apparatus performs the method of any one of claims 1-38.

41. A non-transitory computer-readable recording medium storing a bitstream of video generated by a method performed by a video processing apparatus, wherein, The method includes: The chromaticity information is determined as the side information input to the adaptive loop filter (ALF); and The bit stream is generated based on the ALF.

42. A method for storing a video bitstream, comprising: The chromaticity information is determined as the side information input into the adaptive loop filter ALF; The bit stream is generated based on the ALF; as well as The bit stream is stored in a non-transitory computer-readable recording medium.

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