Adaptive coefficient precision for adaptive loop filter in video coding

Abstract

A mechanism for processing video data is disclosed. The mechanism includes determining that an adaptive coefficient precision for an adaptive loop filter (ALF) is set to a number M, where the number M is different from a fixed number used at an encoder or decoder for the adaptive coefficient precision for the ALF. The conversion between the visual media data and the bitstream may then be performed based on the adaptive coefficient precision for ALF set to the number M.

Description

[0001] Cross-reference to related applications

[0002] This patent application claims the benefit of International Patent Application No. PCT / CN2023 / 122082, filed on September 27, 2023, which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to the generation, storage, and use of digital audio and video media information in file formats. Background Technology

[0004] Digital video accounts for the largest share of bandwidth used 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 is likely to continue to grow. Summary of the Invention

[0005] The first aspect relates to a method for processing video data, comprising: determining that the adaptive coefficient precision for an adaptive loop filter (ALF) is set to a digital M, wherein the digital M is different from a fixed digital number used at an encoder or decoder for the adaptive coefficient precision of the ALF; and performing a conversion between visual media data and a bitstream based on the adaptive coefficient precision for the ALF set to the digital M.

[0006] Alternatively, in any of the foregoing aspects, another embodiment of the aspect provides that, according to the Multifunction Video Codec (VVC) standard, the fixed number used by the encoder or the decoder for the adaptive coefficient precision of the ALF is 8, including the sign bit.

[0007] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides that the luminance ALF coefficients are derived or quantized to M-bit precision, including coefficient sign bits.

[0008] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides that the chroma ALF coefficients are derived or quantized to M-bit precision, including coefficient sign bits.

[0009] Alternatively, in any of the above aspects, another embodiment of the aspect provides that M is greater than 8.

[0010] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the adaptive coefficient precision for the luminance ALF coefficients is included in the bitstream, derived, or predefined.

[0011] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the adaptive coefficient precision for the chroma ALF coefficients is included in the bitstream, derived, or predefined.

[0012] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the luminance ALF coefficients are stored or used with an N-bit precision, the N bits including coefficient sign bits.

[0013] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the chroma ALF coefficients are stored or used with an N-bit precision, the N bits including coefficient sign bits.

[0014] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the adaptive coefficient precision is used in the storage or calculation of the luminance ALF coefficients, and is included in the bitstream, derived, or predefined.

[0015] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the adaptive coefficient precision is used in the storage or calculation of the chroma ALF coefficients, and is included in the bitstream, derived, or predefined.

[0016] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the accuracy of the adaptive coefficients used in derivation, storage, or calculation is the same for the luminance ALF coefficients and for the chrominance ALF coefficients.

[0017] Alternatively, in any of the foregoing aspects, another embodiment of the aspect provides that the accuracy of the adaptive coefficients used in derivation, storage, or calculation is different for the luminance ALF coefficients and for the chrominance ALF coefficients.

[0018] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the accuracy of the adaptive coefficients used in derivation or signaling for the luminance ALF coefficients is the same as the accuracy of the adaptive coefficients used in storage or computation.

[0019] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the accuracy of the adaptive coefficients used in derivation or signaling for the chromaticity ALF coefficients is different from the accuracy of the adaptive coefficients used in storage or computation.

[0020] Alternatively, in any of the foregoing aspects, another embodiment of the foregoing aspects provides that one or more syntax elements at the Sequence Parameter Set (SPS) level are included in, derived, or predefined in the bitstream to indicate whether the adaptive coefficient precision is applied to the luminance ALF.

[0021] Alternatively, in any of the foregoing aspects, another implementation of the foregoing aspects provides that one or more syntax elements at the Sequence Parameter Set (SPS) level are included in, derived, or predefined in the bitstream to indicate whether the adaptive coefficient precision is applied to the chroma ALF.

[0022] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides that the accuracy of the adaptive coefficients in the ALF is different for different components.

[0023] Alternatively, in any of the above aspects, another embodiment of the aspect provides that the accuracy of the adaptive coefficients in the ALF is different for the luminance component and the chrominance component.

[0024] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the accuracy of the adaptive coefficient for the luminance component is set to N, including sign bits.

[0025] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the precision of the adaptive coefficients for the chromaticity components is set to N, including sign bits.

[0026] Alternatively, in any of the above aspects, another implementation of said aspect provides that N is greater than 8.

[0027] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides that the accuracy of the adaptive coefficients in the ALF is different for different ALF methods.

[0028] Alternatively, in any of the foregoing aspects, another embodiment of the foregoing aspect provides that the accuracy of the adaptive coefficients in the ALF is different for ALF luminance (ALF-Luma) and ALF chrominance (ALF-Chroma).

[0029] Alternatively, in any of the foregoing aspects, another embodiment of the foregoing aspect provides that the adaptive coefficient accuracy of the coefficients in the ALF is different for the ALF and the cross-component ALF (CCALF).

[0030] Optionally, in any of the above aspects, another implementation of the aspect provides that the adaptive coefficient precision in the ALF is different for different stages of the ALF, ALF luminance, ALF chrominance, or cross-component ALF (CCALF).

[0031] Optionally, in any of the above aspects, another implementation of the aspect provides that the adaptive coefficient precision encoded in the bitstream or parsed from the bitstream is different from the adaptive coefficient precision used in the filtering process.

[0032] Optionally, in any of the above aspects, another implementation of the aspect provides that the coefficients are modified before being encoded in the bitstream or after being parsed from the bitstream.

[0033] Optionally, in any of the above aspects, another implementation of the aspect provides that the modification of the coefficients includes a left shift or a right shift.

[0034] Optionally, in any of the above aspects, another implementation of the aspect provides that the modification is performed according to the formula X' = (X + offset) >> S, where X and X' are the coefficients before and after the modification, respectively, and where offset and S are integers.

[0035] Optionally, in any of the above aspects, another implementation of the aspect provides that the modification is performed according to the formula X' = X << S, where X and X' are the coefficients before and after the modification, respectively, and where S is an integer.

[0036] Optionally, in any of the above aspects, another implementation of the aspect provides that the modification of the coefficients includes multiplication by a factor, and where the factor is included in the bitstream, derived, or predefined.

[0037] Optionally, in any of the above aspects, another implementation of the aspect provides that the modification of the coefficients includes addition of an offset, and where the offset is included in the bitstream, derived, or predefined.

[0038] Optionally, in any of the above aspects, another implementation of the aspect provides that the adaptive coefficient precision included in the bitstream or parsed from the bitstream is M1, the adaptive coefficient precision used in the filtering process is M2, and the modification of the adaptive coefficient precision depends on at least one of M1 and M2.

[0039] Optionally, in any of the above aspects, another implementation of the aspect provides that when M1 > M2, X' = (X + offset) >> S, where X is the parsed coefficient, X' is the coefficient used to filter the sample points, S is set to M1 - M2, and offset is an integer determined according to offset = 1 << (S - 1).

[0040] Optionally, in any of the above aspects, another implementation of the aspect provides that when M1 < M2, X' = X << S, where X is the parsed coefficient, X' is the coefficient used to filter the sample points, and S is set to M2 - M1.

[0041] Optionally, in any of the above aspects, another implementation of the aspect provides applying the adaptive coefficient precision to the ALF.

[0042] Optionally, in any of the above aspects, another implementation of the aspect provides that the adaptive coefficient precision is used for the luminance ALF filter and is included in the bitstream, derived, or predefined.

[0043] Optionally, in any of the above aspects, another implementation of the aspect provides that the adaptive coefficient precision is used for a set of luminance ALF filters including multiple filters and is included in the bitstream, derived, or predefined.

[0044] Optionally, in any of the above aspects, another implementation of the aspect provides that the adaptive coefficient precision is used for the chrominance ALF filter and is included in the bitstream, derived, or predefined.

[0045] Optionally, in any of the above aspects, another implementation of the aspect provides that the adaptive coefficient precision is used for a set of chrominance ALF filters including multiple filters and is included in the bitstream, derived, or predefined.

[0046] Optionally, in any of the above aspects, another implementation of the aspect provides that the adaptive coefficient precision for the set of luminance ALF filters used in storage or calculation is included in the bitstream, derived, or predefined.

[0047] Optionally, in any of the above aspects, another implementation of the aspect provides that the adaptive coefficient precision for the set of luminance ALF filters including multiple filters used in storage or calculation is included in the bitstream, derived, or predefined.

[0048] Alternatively, in any of the foregoing aspects, another embodiment of the foregoing aspects provides that the accuracy of the adaptive coefficients for the chroma ALF filter set used in storage or computation is included in, derived, or predefined in the bitstream.

[0049] Optionally, in any of the foregoing aspects, another embodiment of said aspect provides that the accuracy of the adaptive coefficients for a chroma ALF filter bundle containing multiple filters used in storage or computation is included in, derived, or predefined in the bitstream.

[0050] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the adaptive coefficient precision index of the luminance ALF is included in the video parameter set (VPS), sequence parameter set (SPS), picture parameter set (PPS), block or adaptive parameter set (APS).

[0051] Optionally, in any of the foregoing aspects, another embodiment of the foregoing aspects provides that the adaptive coefficient precision index of each luminance ALF filter set containing multiple filters is included in the video parameter set (VPS), sequence parameter set (SPS), picture parameter set (PPS), block or adaptive parameter set (APS).

[0052] Optionally, in any of the foregoing aspects, another embodiment of the foregoing aspects provides that the adaptive coefficient precision index for each chroma ALF is included in the video parameter set (VPS), sequence parameter set (SPS), picture parameter set (PPS), block or adaptive parameter set (APS).

[0053] Optionally, in any of the foregoing aspects, another embodiment of the foregoing aspects provides that the adaptive coefficient precision index of each chroma ALF filter bundle containing multiple filters is included in the video parameter set (VPS), sequence parameter set (SPS), picture parameter set (PPS), block or adaptive parameter set (APS).

[0054] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the adaptive coefficient precision index is encoded and decoded using fixed-length code, exponential Golomb (EGx) code, unary code, rounding binary code, context model, or bypass method, and wherein the adaptive coefficient precision index is signed or unsigned.

[0055] Alternatively, in any of the foregoing aspects, another embodiment of the aspect provides a coefficient precision index for the luminance ALF in the bitstream, depending on whether the coefficients are modified before being encoded into the bitstream or after being parsed from the bitstream.

[0056] Alternatively, in any of the foregoing aspects, another embodiment of the aspect provides a coefficient precision index that determines whether the coefficients are modified before being encoded into the bitstream or after being parsed from the bitstream, depending on the luminance ALF set comprising multiple filters.

[0057] Alternatively, in any of the foregoing aspects, another embodiment of the aspect provides that whether the coefficients are modified before being encoded into the bitstream or after being parsed from the bitstream depends on the coefficient precision index for the chroma ALF in the bitstream.

[0058] Alternatively, in any of the foregoing aspects, another embodiment of the aspect provides a coefficient precision index that determines whether the coefficients are modified before being encoded into the bitstream or after being parsed from the bitstream, depending on the chroma ALF set comprising multiple filters.

[0059] Alternatively, in any of the foregoing aspects, another embodiment of the foregoing aspects provides that one or more syntax elements at the Sequence Parameter Set (SPS) level are included in, derived, or predefined in the bitstream to indicate whether the adaptive coefficient precision is applied to the luminance ALF.

[0060] Alternatively, in any of the foregoing aspects, another implementation of the foregoing aspects provides that one or more syntax elements at the Sequence Parameter Set (SPS) level are included in, derived, or predefined in the bitstream to indicate whether the adaptive coefficient precision is applied to the chroma ALF.

[0061] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides that the coefficients in the bitstream for the ALF are encoded and decoded using exponential Golomb (EGx) codes.

[0062] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides that the coefficients in a filter are classified into N groups, where N is an integer.

[0063] Alternatively, in any of the foregoing aspects, another implementation of said aspect provides a classification rule for said filter based on the number of input coefficients.

[0064] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides a classification rule for said filter based on a symmetric design of a coefficient.

[0065] Alternatively, in any of the above aspects, another implementation of the aspect provides that coefficients applied to an input are assigned to a group.

[0066] Alternatively, in any of the above aspects, another implementation of the aspect provides that coefficients applied to the two inputs are assigned to a group.

[0067] Alternatively, in any of the above aspects, another implementation of the aspect provides that coefficients applied to M inputs are assigned to a group, where M is an integer.

[0068] Alternatively, in any of the foregoing aspects, another implementation of said aspect provides that the parameters in the exponential Golomb (EGx) code are adaptive for each filter.

[0069] Alternatively, in any of the foregoing aspects, another implementation of said aspect provides for coefficients in a filter, wherein the parameter K is included in, derived, or predefined in the bitstream.

[0070] Alternatively, in any of the foregoing aspects, another implementation of said aspect provides for coefficients in a filter, wherein the parameter K-offset is included in, derived, or predefined in the bitstream.

[0071] Alternatively, in any of the foregoing aspects, another embodiment of the aspect provides that the parameters K and K-offset are encoded and decoded using fixed-length codes, exponential Golomb codes (EGx codes), unary codes, or rounded binary codes.

[0072] Optionally, in any of the foregoing aspects, another implementation of said aspect provides that the parameters K and K-offset are encoded and decoded using at least one context model or bypass method.

[0073] Alternatively, in any of the foregoing aspects, another embodiment of the foregoing aspects provides that parameter K and parameter K-offset are included in the adaptive parameter set (APS) of the bitstream.

[0074] Alternatively, in any of the foregoing aspects, another implementation of said aspect provides a filter in which the coefficients use the same K.

[0075] Alternatively, in any of the foregoing aspects, another implementation of said aspect provides that the coefficients in the filter use different K values.

[0076] Alternatively, in any of the above aspects, another embodiment of the aspect provides that the coefficients applied to the two inputs are used to decode the exponential Golomb (EGx) code using K.

[0077] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides that the coefficients applied to an input are used to decode the exponential Golomb (EGx) code using K.

[0078] Alternatively, in any of the foregoing aspects, another implementation of said aspect provides that the coefficients applied to an input are used to decode the exponential Golomb (EGx) code using K+K-offset.

[0079] Alternatively, in any of the foregoing aspects, another implementation of said aspect provides that the parameters in the Exponential Columbus (EGx) codec are adaptive for each set of coefficients in a filter.

[0080] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides that for each set of coefficients in a filter, parameter K is included in the bitstream, predefined, or included in the bitstream.

[0081] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides that for each set of coefficients in a filter, the parameter K-offset is included in the bitstream, is predefined, or is included in the bitstream.

[0082] Optionally, in any of the above aspects, another embodiment of the aspect provides that the parameter K and the parameter K-offset are encoded and decoded using fixed-length code, exponential Golomb code (EGx code), unary code, or rounded binary code, and wherein the parameter K and the parameter K-offset are signed or unsigned.

[0083] Optionally, in any of the foregoing aspects, another implementation of said aspect provides that the parameters K and K-offset are encoded and decoded using at least one context model or bypass method.

[0084] Alternatively, in any of the foregoing aspects, another embodiment of the foregoing aspects provides that parameter K and parameter K-offset are included in the adaptive parameter set (APS) of the bitstream.

[0085] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides the use of coefficients applied to two inputs. To decode the Exponential Columbus (EGx) code.

[0086] Optionally, in any of the foregoing aspects, another embodiment of said aspect provides the use of coefficients applied to an input. To decode the Exponential Columbus (EGx) code.

[0087] Optionally, in any of the foregoing aspects, another embodiment of said aspect provides the use of coefficients applied to an input. + K-offset to decode Exponential Columbus (EGx) code.

[0088] Alternatively, in any of the foregoing aspects, another implementation of said aspect provides that the parameters in the Exponential Columbus (EGx) codec are adaptive for each set of coefficients in a filter set comprising multiple filters.

[0089] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides that for each set of coefficients in a filter, parameter K is included in the bitstream, predefined, or included in the bitstream.

[0090] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides that for each set of coefficients in a filter, the parameter K-offset is included in the bitstream, is predefined, or is included in the bitstream.

[0091] Optionally, in any of the above aspects, another embodiment of the aspect provides that the parameter K and the parameter K-offset are encoded and decoded using fixed-length code, exponential Golomb code (EGx code), unary code, or rounded binary code, and wherein the parameter K and the parameter K-offset are signed or unsigned.

[0092] Optionally, in any of the foregoing aspects, another implementation of said aspect provides that the parameters K and K-offset are encoded and decoded using at least one context model or bypass method.

[0093] Alternatively, in any of the foregoing aspects, another embodiment of the foregoing aspects provides that parameter K and parameter K-offset are included in the adaptive parameter set (APS) of the bitstream.

[0094] Alternatively, in any of the above aspects, another implementation of the aspect provides that the coefficients applied to the two inputs are used to decode the exponential Golomb (EGx) code using K_g1.

[0095] Alternatively, in any of the above aspects, another implementation of said aspect provides that coefficients applied to an input are used to decode the exponential Golomb (EGx) code using K_g2.

[0096] Alternatively, in any of the above aspects, another implementation of said aspect provides that coefficients applied to an input are used to decode the exponential Golomb (EGx) code using K_g2 + K-offset.

[0097] Optionally, in any of the foregoing aspects, another embodiment of said aspect provides that any of the disclosed methods are used in one or more of the post-processing and pre-processing.

[0098] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that any of the disclosed methods are used in combination.

[0099] Alternatively, in any of the foregoing aspects, another embodiment of said aspect provides that any of the disclosed methods can be used alone.

[0100] Optionally, in any of the foregoing aspects, another embodiment of said aspect provides that any of the disclosed methods for the adaptive coefficient accuracy of ALF is applied to any loop filtering tool, preprocessing filtering method, or postprocessing filtering method in video encoding and decoding, including ALF, CCALF, or any other filtering method.

[0101] Alternatively, in any of the above aspects, another embodiment of the aspect provides that the adaptive coefficient accuracy is applied to the loop filtering method.

[0102] Alternatively, in any of the above aspects, another embodiment of the aspect provides that the adaptive coefficient accuracy is applied to ALF.

[0103] Alternatively, in any of the above aspects, another embodiment of the aspect provides that the adaptive coefficient accuracy is applied to CCALF.

[0104] Alternatively, in any of the above aspects, another embodiment of the aspect provides that the adaptive coefficient accuracy is applied to bilateral filtering (BF).

[0105] Alternatively, in any of the above aspects, another embodiment of the aspect provides that the adaptive coefficient accuracy is applied to sample adaptive compensation (SAO) filtering.

[0106] Alternatively, in any of the foregoing aspects, another embodiment of the foregoing aspects provides that the adaptive coefficient accuracy is applied to cross-component sample adaptive compensation (CCSAO) filtering.

[0107] Alternatively, in any of the above aspects, another embodiment of the aspect provides that the adaptive coefficient accuracy is applied to the preprocessing filtering method.

[0108] Alternatively, in any of the above aspects, another embodiment of the aspect provides that the adaptive coefficient accuracy is applied to the post-processing filtering method.

[0109] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that the adaptive coefficient precision is used for video units, and wherein the video unit is a sequence, picture, sub-picture, strip, slice, codec tree unit (CTU), CTU row, CTU group, codec unit (CU), prediction unit (PU), transform unit (TU), codec tree block (CTB), codec block (CB), prediction block (PB), transform block (TB), or any other region containing more than one luminance or chrominance sample or pixel.

[0110] Optionally, in any of the foregoing aspects, another embodiment of said aspect provides whether and / or how one or more of the disclosed methods are applied in the bitstream for signal transmission.

[0111] Optionally, in any of the foregoing aspects, another embodiment of said aspect provides whether and / or how one or more of the disclosed methods are applied at the sequence level, picture group level, picture level, strip level, slice group level, or are signaled or included in the sequence header, picture header, SPS, video parameter set (VPS), dependency parameter set (DPS), decoding capability information (DCI), PPS, APS, strip header, or slice group header.

[0112] Optionally, in any of the foregoing aspects, another embodiment of said aspect provides whether and / or how one or more of the disclosed methods are applied to a prediction block (PB), transform block (TB), codec block (CB), prediction unit (PU), transform unit (TU), codec unit (CU), virtual pipeline data unit (VPDU), codec tree unit (CTU), CTU row, strip, slice, sub-picture, or any other region containing more than one sample or pixel, via signal transmission.

[0113] Optionally, in any of the foregoing aspects, another embodiment of the aspect provides that whether and / or how one or more of the disclosed methods are applied depends on encoding / decoding information, and wherein the encoding / decoding information includes one or more of block size, color format, single-tree segmentation or dual-tree segmentation, color components, stripe type or picture type.

[0114] Alternatively, in any of the foregoing aspects, another embodiment of the aspect provides that the conversion includes encoding the media data into the bitstream.

[0115] Alternatively, in any of the foregoing aspects, another embodiment of the aspect provides that the conversion includes decoding the media data from the bitstream.

[0116] The second aspect relates to an apparatus for processing video data, comprising: a processor; and a non-transitory memory having instructions thereon, wherein the instructions, when executed by the processor, cause the processor to perform any of the disclosed methods.

[0117] The third aspect relates to 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, which, when executed by a processor, cause the video codec device to perform any of the disclosed methods.

[0118] The fourth aspect relates to 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 that the adaptive coefficient precision for an adaptive loop filter (ALF) is set to a digital M, wherein the digital M is different from a fixed digital number used at an encoder or decoder for the adaptive coefficient precision of the ALF; and performing a conversion between visual media data and a bitstream based on the adaptive coefficient precision for the ALF set to the digital M.

[0119] The fifth aspect relates to a method for storing a bitstream of video, comprising: determining that the adaptive coefficient precision for an adaptive loop filter (ALF) is set to a number M, wherein the number M is different from a fixed number used at an encoder or decoder for the adaptive coefficient precision of the ALF; generating the bitstream using the adaptive coefficient precision; and storing the bitstream in a non-transitory computer-readable recording medium.

[0120] The sixth aspect relates to the methods, apparatus, or systems described in this disclosure.

[0121] For clarity, any of the embodiments in the foregoing embodiments may be combined with any one or more of the other embodiments in the foregoing embodiments to create new embodiments within the scope of this disclosure.

[0122] These and other features will be more clearly understood through the following detailed description with reference to the accompanying drawings and claims. Attached Figure Description

[0123] To gain a more complete understanding of this disclosure, reference is now made to the following brief description, taken in conjunction with the accompanying drawings and detailed embodiments, wherein like reference numerals denote like parts.

[0124] Figure 1 An example of the nominal vertical and horizontal positions of 4:2:2 luminance and chrominance samples in an image is shown.

[0125] Figure 2 A sample encoder block diagram is shown.

[0126] Figure 3 An example image is shown, segmented into raster scan strips.

[0127] Figure 4 An example image is shown, segmented into rectangular scan strips.

[0128] Figure 5 An example image showing the structure divided into bricks is shown.

[0129] Figures 6A-6C An example of a codec tree block (CTB) spanning image boundaries is shown.

[0130] Figure 7 An example of an intra-frame prediction mode is shown.

[0131] Figure 8 An example of a block boundary is shown in the image.

[0132] Figure 9 An example of pixels used in a filter is shown.

[0133] Figure 10 An example of the filter shape for an adaptive loop filter (ALF) is shown.

[0134] Figure 11 An example of the transform coefficients supported by a 5×5 diamond filter is shown.

[0135] Figure 12 An example of relative coordinates supported by a 5×5 rhombus filter is shown.

[0136] Figure 13 This is a block diagram illustrating an example video processing system.

[0137] Figure 14 This is a block diagram of an example video processing device.

[0138] Figure 15 This is a flowchart of an example method for video processing.

[0139] Figure 16 This is a block diagram illustrating an example video codec system.

[0140] Figure 17 This is a block diagram showing an example encoder.

[0141] Figure 18 This is a block diagram showing an example decoder.

[0142] Figure 19 This is a schematic diagram of an example encoder. Detailed Implementation

[0143] First, it should be understood 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 yet to be developed. This disclosure should not be limited in any way to the illustrative embodiments, drawings, and techniques described below, including the exemplary designs and implementations shown and described herein, but can be modified within the scope of the appended claims and all their equivalents.

[0144] Chapter headings are used in this disclosure for ease of understanding and not to limit the applicability of the techniques and embodiments disclosed in each chapter to that chapter only. Furthermore, the techniques described herein are applicable to other video codec protocols and designs.

[0145] 1. Preliminary Discussion

[0146] This disclosure relates to video codec techniques. Specifically, it relates to loop filters and other codec tools in image / video codecs. These ideas can be applied individually or in various combinations to video codecs, such as High Efficiency Video Codec (HEVC), Multi-Functional Video Codec (VVC), or other video codec techniques.

[0147] 2. Abbreviation

[0148] This disclosure includes the following abbreviations. Advanced Video Coding (ITU-T H.264 | ISO / IEC 14496-10) (AVC), Coded Picture Buffer (CPB), Pure Random Access (CRA), Code-Decoder Tree Unit (CTU), Coded Video Sequence (CVS), Decoded Picture Buffer (DPB), Decoder Parameter Set (DPS), General Constraint Information (GCI), High-Efficiency Video Coding (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), Grade, Layer and Level (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 (ITU-T H.265) (also known as ITU-T H.265) 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).

[0149] 3. Video codec standards

[0150] Video coding standards have evolved primarily through the development of standards by 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.

[0151] 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.

[0152] The International Telecommunication Union Telecommunication Standardization Sector (ITU-T) Video Coding Experts Group (VCEG) and the International Organization for Standardization and the International Electrotechnical Commission (ISO / IEC) Moving Picture Experts Group (MPEG) Joint Technical Committee (JTC) 1 / Subcommittee (SC) 29 / Working Group (WG) 11 are studying the potential need to standardize future video coding and decoding technologies with compression capabilities significantly exceeding the current VVC standard. Such future standardization could take the form of extensions to VVC (multiple extensions) or entirely new standards. These groups are conducting this exploratory activity in a joint collaborative effort called the Joint Video Exploration Team (JVET) to evaluate compression technology designs proposed by experts in the field. The 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.

[0153] 3.1 Color Space and Chromaticity Downsampling

[0154] 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).

[0155] 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, and CB and CR are the blue and red chromaticity components, respectively. Y' (with an apostrophe) is distinguished from Y, which stands for luminance, meaning that light intensity is encoded non-linearly based on gamma-corrected RGB primary colors.

[0156] 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

[0158] 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

[0160] In a 4:3:2 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 The image depicts an example of the nominal vertical and horizontal positions of the 4:2:2 color format. 3.1.3 4:2:0

[0162] In 4:2:0, the horizontal sampling is doubled compared to 4:1:1, but the vertical resolution is halved because the blue chromatic aberration (Cb) and red chromatic aberration (Cr) channels are sampled only on each alternating row. 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.

[0163] In MPEG-2, Cb and Cr are co-located horizontally. Cb and Cr are located between pixels vertically (at inter-pixel positions). In Joint Picture Experts Group (JPEG) / JPEG File Exchange Format (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.

[0164] chroma_format_idc separate_colour_plane_flag Color format SubWidthC SubHeightC 0 0 monochrome 1 1 1 0 4:2:0 2 2 2 0 4:2:2 2 1 3 0 4:4:4 1 1 3 1 4:4:4 1 1

[0165] Table 1. SubWidthC and SubHeightC values ​​derived from chroma_format_idc and separate_colour_plane_flag

[0166] 3.2 Example Encoding / Decoding Flow of Video Codec

[0167] Figure 2 An example of a VVC encoder block diagram is shown, containing 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 by applying a Finite Impulse Response (FIR) filter, respectively, and by utilizing the 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.

[0168] 3.3 Definition of Video / Encoding / Decoding Unit

[0169] 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 multiple bricks of a slice.

[0170] 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 3 An example of raster scan strip segmentation of an image is shown, where the image is divided into 12 slices and 3 raster scan strips.

[0171] Figure 4 An example of rectangular strip segmentation of an image is shown, where the image is divided into 24 slices (6 slice columns and 4 slice rows) and 9 rectangular strips.

[0172] 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.

[0173] 3.3.1 CTU / CTB Dimensions

[0174] 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 4x4.

[0175] 7.3.2.3 Sequence Parameter Set (RBSP) Syntax

[0176] seq_parameter_set_rbsp() { descriptor sps_decoding_parameter_set_id u(4) sps_video_parameter_set_id u(4) sps_max_sub_layers_minus1 u(3) sps_reserved_zero_5bits u(5) profile_tier_level( sps_max_sub_layers_minus1 ) gra_enabled_flag u(1) sps_seq_parameter_set_id ue(v) chroma_format_idc ue(v) if (chroma_format_idc == 3) separate_colour_plane_flag u(1) pic_width_in_luma_samples ue(v) pic_height_in_luma_samples ue(v) conformance_window_flag u(1) if( conformance_window_flag ) { conf_win_left_offset ue(v) conf_win_right_offset ue(v) conf_win_top_offset ue(v) conf_win_bottom_offset ue(v) } bit_depth_luma_minus8 ue(v) bit_depth_chroma_minus8 ue(v) log2_max_pic_order_cnt_lsb_minus4 ue(v) sps_sub_layer_ordering_info_present_flag u(1) for( i = ( sps_sub_layer_ordering_info_present_flag ? 0 : sps_max_sub_layers_minus1 ); i <= sps_max_sub_layers_minus1; i++ ) { sps_max_dec_pic_buffering_minus1[ i ] ue(v) sps_max_num_reorder_pics[i] ue(v) sps_max_latency_increase_plus1[i] ue(v) } long_term_ref_pics_flag u(1) sps_idr_rpl_present_flag u(1) rpl1_same_as_rpl0_flag u(1) for( i = 0; i < !rpl1_same_as_rpl0_flag ? 2 : 1; i++ ) { num_ref_pic_lists_in_sps[i] ue(v) for( j = 0; j < num_ref_pic_lists_in_sps[ i ]; j++) ref_pic_list_struct( i, j ) } qtbtt_dual_tree_intra_flag u(1) log2_ctu_size_minus2 ue(v) log2_min_luma_coding_block_size_minus2 ue(v) partition_constraints_override_enabled_flag u(1) sps_log2_diff_min_qt_min_cb_intra_slice_luma ue(v) sps_log2_diff_min_qt_min_cb_inter_slice ue(v) sps_max_mtt_hierarchy_depth_inter_slice ue(v) sps_max_mtt_hierarchy_depth_intra_slice_luma ue(v) if( sps_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) { sps_log2_diff_max_bt_min_qt_intra_slice_luma ue(v) sps_log2_diff_max_tt_min_qt_intra_slice_luma ue(v) } if( sps_max_mtt_hierarchy_depth_inter_slices != 0 ) { sps_log2_diff_max_bt_min_qt_inter_slice ue(v) sps_log2_diff_max_tt_min_qt_inter_slice ue(v) } if( qtbtt_dual_tree_intra_flag ) { sps_log2_diff_min_qt_min_cb_intra_slice_chroma ue(v) sps_max_mtt_hierarchy_depth_intra_slice_chroma ue(v) if ( sps_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) { sps_log2_diff_max_bt_min_qt_intra_slice_chroma ue(v) sps_log2_diff_max_tt_min_qt_intra_slice_chroma ue(v) } } … rbsp_trailing_bits( ) }

[0177] `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:

[0178] CtbLog2SizeY = log2_ctu_size_minus2 + 2 (7-9)

[0179] CtbSizeY = 1 << CtbLog2SizeY (7-10)

[0180] MinCbLog2SizeY = log2_min_luma_coding_block_size_minus2 + 2 (7-11)

[0181] MinCbSizeY = 1 << MinCbLog2SizeY (7-12)

[0182] MinTbLog2SizeY = 2 (7-13)

[0183] MaxTbLog2SizeY = 6 (7-14)

[0184] MinTbSizeY = 1 << MinTbLog2SizeY (7-15)

[0185] MaxTbSizeY = 1 << MaxTbLog2SizeY (7-16)

[0186] PicWidthInCtbsY = Ceil( pic_width_in_luma_samples ÷ CtbSizeY ) (7-17)

[0187] PicHeightInCtbsY = Ceil( pic_height_in_luma_samples ÷ CtbSizeY ) (7-18)

[0188] PicSizeInCtbsY = PicWidthInCtbsY PicHeightInCtbsY (7-19)

[0189] PicWidthInMinCbsY = pic_width_in_luma_samples / MinCbSizeY (7-20)

[0190] PicHeightInMinCbsY = pic_height_in_luma_samples / MinCbSizeY (7-21)

[0191] PicSizeInMinCbsY = PicWidthInMinCbsY PicHeightInMinCbsY (7-22)

[0192] PicSizeInSamplesY = pic_width_in_luma_samples pic_height_in_luma_samples (7-23)

[0193] PicWidthInSamplesC = pic_width_in_luma_samples / SubWidthC (7-24)

[0194] PicHeightInSamplesC = pic_height_in_luma_samples / SubHeightC (7-25)

[0195] 3.3.2 CTUs in a Picture

[0196] Assume a CTB / largest coding unit (LCU) size indicated by M×N (usually M equals N), and for a CTB located at the boundary of the picture (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 depicted as in Figures 6A - 6C the CTB size still equals M×N. However, the lower / right boundary of the CTB is outside the picture.

[0197] 3.4 Intra-frame prediction

[0198] To capture arbitrary edge directions presented in natural video, the number of intra-frame directional modes was expanded from the 33 used in HEVC to 65. The expanded directional modes are as follows: Figure 7 As shown, both planar and DC modes remain unchanged. These denser directional intra-prediction modes are applicable to all block sizes as well as luma and chroma intra-prediction.

[0199] like Figure 7 As 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 unchanged, for example, 67, and the intra-mode encoding and decoding remain unchanged.

[0200] 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 is needed to generate intra-prediction values ​​using DC mode. In VVC, blocks can have rectangular shapes, which generally requires division for each block. To avoid division for DC prediction, only the longer side is used to calculate the average of non-square blocks.

[0201] 3.5 Inter-frame prediction

[0202] 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 to be 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 for 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 the motion vectors, the corresponding reference picture indexes for each reference picture list, the reference picture list usage flags, and other useful information are explicitly transmitted via signaling for each CU.

[0203] 3.6 Deblocking Filter

[0204] 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.

[0205] 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.

[0206] 3.6.1 Boundary Decision

[0207] 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.

[0208] 3.6.2 Boundary Strength Calculation

[0209] 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.

[0210] Priority Condition Y U V 5 At least one of the neighboring blocks is intra 2 2 2 4 The TU boundary and at least one adjacent block have non-zero transformation coefficients. 1 1 1 3 The number of reference images or MVs for adjacent blocks differs (1 for one-way prediction and 2 for two-way prediction). 1 N / A N / A 2 The absolute difference between motion vectors belonging to adjacent blocks in the same reference image is greater than or equal to an integer brightness sample. 1 N / A N / A 1 other 0 0 0

[0211] Table 2. Boundary Strength (when SPS Intra-Block Copy (IBC) is disabled)

[0212] Priority condition Y U V 8 At least one of the adjacent blocks is intra-frame 2 2 2 7 The TU boundary and at least one adjacent block have non-zero transformation coefficients. 1 1 1 6 Neighboring blocks have different prediction modes (e.g., one is IBC, and the other is inter-frame). 1 5 The absolute difference between the IBC and the motion vector belonging to the adjacent block is greater than or equal to an integer brightness sample. 1 N / A N / A 4 The number of reference images or MVs for adjacent blocks differs (1 for one-way prediction and 2 for two-way prediction). 1 N / A N / A 3 The absolute difference between motion vectors belonging to adjacent blocks in the same reference image is greater than or equal to an integer brightness sample. 1 N / A N / A 1 other 0 0 0

[0213] Table 3. Boundary Strength (when SPS IBC is enabled)

[0214] 3.6.3 Deblocking decision for the luminance component

[0215] A wider and stronger brightness filter is used only when 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, and is represented by the variables bSidePisLargeBlk and bSideQisLargeBlk, respectively. bSidePisLargeBlk and bSideQisLargeBlk are defined as follows.

[0216] 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

[0217] 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

[0218] Based on bSidePisLargeBlk and bSideQisLargeBlk, condition 1 is defined as follows:

[0219] Condition 1 = (bSidePisLargeBlk || bSidePisLargeBlk) ? True : False

[0220] Next, if condition 1 is true, condition 2 will be further examined. First, the following variables are derived:

[0221] First, derive dp0, dp3, dq0, and dq3 using the HEVC method.

[0222] if (p side is greater than or equal to 32)

[0223] dp0 = (dp0 + Abs(p50 - 2)) p40 + p30 + 1) >> 1

[0224] dp3 = (dp3 + Abs(p53 - 2)) p43 + p33 + 1) >> 1

[0225] if (q side is greater than or equal to 32)

[0226] dq0 = (dq0 + Abs(q50 - 2)) q40 + q30 + 1) >> 1

[0227] dq3 = (dq3 + Abs(q53 - 2)) q43 + q33 + 1) >> 1

[0228] Condition 2 = (d < β) ? True : False

[0229] Where d = dp0 + dq0 + dp3 + dq3.

[0230] If conditions 1 and 2 are valid, then further check whether any of the blocks uses a sub-block:

[0231] If (bSidePisLargeBlk)

[0232] {

[0233] If (block P's mode == SUBBLOCKMODE)

[0234] Sp = 5

[0235] else

[0236] Sp = 7

[0237] }

[0238] else

[0239] Sp = 3

[0240] If (bSideQisLargeBlk)

[0241] {

[0242] If (block Q's mode == SUBBLOCKMODE)

[0243] Sq = 5

[0244] else

[0245] Sq = 7

[0246] }

[0247] else

[0248] Sq = 3

[0249] 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:

[0250] Derive dpq using the HEVC method.

[0251] Derive sp3 = Abs( p3 - p0 ) using the HEVC method

[0252] if (p side is greater than or equal to 32)

[0253] if (Sp == 5)

[0254] sp3 = ( sp3 + Abs( p5 - p3 ) + 1) >> 1

[0255] else

[0256] sp3 = ( sp3 + Abs( p7 - p3 ) + 1) >> 1

[0257] Derive sq3 = Abs( q0 - q3 ) using the HEVC method.

[0258] if (q side is greater than or equal to 32)

[0259] If (Sq == 5)

[0260] sq3 = ( sq3 + Abs( q5 - q3 ) + 1) >> 1

[0261] else

[0262] sq3 = ( sq3 + Abs( q7 - q3 ) + 1) >> 1

[0263] According to HEVC, StrongFilterCondition = (dpq < (β >> 2), sp3 + sq3 < (3)). β >> 5), and Abs(p0 - q0) is less than (5). tC + 1 ) >> 1) ? True: False.

[0264] 3.6.4 A more robust deblocking filter for luminance

[0265] When samples on either side of the boundary belong to a large block, a bilinear filter is used. Samples belonging to a large block are defined as those with a vertical edge width >= 32 and a horizontal edge height >= 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:

[0266]

[0267]

[0268] in and The item is the amplitude limit related to the above-mentioned location, and , , , and The following is given.

[0269] 3.6.5 Color Deblocking Decision

[0270] 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 decision of the block size. The filter can be applied when the block width or height orthogonally across 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.

[0271] In the first decision, the boundary strength (bS) is modified for chroma filtering, and the 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.

[0272] 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:

[0273] Derive dpq using HEVC method

[0274] Derive sp3 = Abs( p3 - p0 ) using the HEVC method

[0275] Derive sq3 = Abs( q0 - q3 ) using the HEVC method.

[0276] According to the HEVC design, StrongFilterCondition = (dpq < (β >> 2), sp3 + sq3 < (β >> 3), and Abs(p0 - q0) < (5). tC + 1 ) >> 1).

[0277] 3.6.6 Strong Deblocking Filter for Chroma

[0278] The following strong deblocking filter is defined for chroma:

[0279] p2′= (3 p3+2 p2+p1+p0+q0+4) >> 3

[0280] p1′= (2 p3+p2+2 p1+p0+q0+q1+4) >> 3

[0281] p0′= (p3+p2+p1+2 p0+q0+q1+q2+4) >> 3

[0282] The example chroma filter performs deblocking on a 4x4 chroma sample grid.

[0283] 3.6.7 Location-related amplitude limiting

[0284] Position-dependent limiting (tcPD) is applied to the output samples of a luminance 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 anticipating a higher deviation between the reconstructed sample values ​​and the true sample values.

[0285] 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, based on the results of the decision-making process:

[0286] Tc7 = {6, 5, 4, 3, 2, 1, 1}; Tc3 = {6, 4, 2};

[0287] tcPD = (Sp == 3) ? Tc3 : Tc7;

[0288] tcQD = (Sq == 3) ? Tc3 : Tc7;

[0289] For P or Q boundaries filtered by a short symmetric filter, apply a lower-amplitude position correlation threshold:

[0290] Tc3 = { 3, 2, 1};

[0291] After defining the threshold, the filtered p'i and q'i sample values ​​are limited according to the tcP and tcQ limiting values:

[0292] p''i = Clip3(p'i + tcPi, p'i – tcPi, p'i );

[0293] q''j = Clip3(q'j + tcQj, q'j – tcQ j, q'j );

[0294] Where p'i and q'i are the filtered sample values, p''i and q''j are the output sample values ​​after clipping, and tcPitcPi is the clipping threshold derived from the VVC tc parameters, tcPD, and tcQD. The function Clip3 is the clipping function as specified in VVC.

[0295] 3.6.8 Sub-block Removal and Adjustment

[0296] 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, ATMVP, or DMVR), as shown in the brightness control of the long filter. 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.

[0297] The following applies to sub-block boundaries that are not aligned with the CU boundary.

[0298] If (block Q's mode == SUBBLOCKMODE && edge != 0) {

[0299] if (!(implicitTU && (edge ​​== (64 / 4))))

[0300] if (edge ​​== 2 || edge == (orthogonalLength - 2) || edge== (56 / 4) || edge == (72 / 4))

[0301] Sp = Sq = 2;

[0302] else

[0303] Sp = Sq = 3;

[0304] else

[0305] Sp = Sq = bSideQisLargeBlk ? 5:3

[0306] }

[0307] 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.

[0308] 3.7 Sample point adaptive compensation

[0309] Sample Adaptive Compensation (SAO) is applied to the reconstructed signal after the deblocking filter using an offset 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 an offset to the pixels in each category. SAO operations include Edge Offset (EO) and Band Offset (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 offsets. If sao_merge_left_flag is equal to 1, the current CTB will reuse the SAO type and offset of the left CTB. If sao_merge_up_flag equals 1, the current CTB will reuse the SAO type and offset of the CTB above.

[0310] SAO type The type of sample adaptive compensation to be used Number of categories 0 none 0 1 1-D 0-degree pattern edge offset 4 2 1-D 90-degree pattern edge offset 4 3 1-D 135-degree pattern edge offset 4 4 1-D 45-degree pattern edge offset 4 5 With offset 4

[0311] Table 4. Specifications for SAO Types

[0312] 3.8 Adaptive Loop Filter

[0313] 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 striped data. This syntax design not only supports picture-level optimization but also achieves low encoding latency.

[0314] 3.8.1 Signaling of Parameters

[0315] According to the ALF design in VTM, filter coefficients and clipping indices are carried in the ALF APS. An 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. Exp-Golomb code (0th order) is used to represent the absolute values ​​of the filter coefficients and the sign bits for subsequent non-zero coefficients. When clipping is enabled, a two-bit fixed-length code is also used for each filter coefficient transmitted via the signal to establish the clipping index. The decoder can use up to eight ALF APSs simultaneously.

[0316] The ALF filter control syntax elements 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 Luminance filter set is used. For Chroma CTB, an index indicates which filter in the referenced APS is used.

[0317] The data syntax elements of the ALF associated with the luminance component in VTM are listed below:

[0318] alf_data() { descriptor alf_luma_filter_signal_flag u(1) if( alf_luma_filter_signal_flag ) { alf_luma_clip_flag u(1) alf_luma_num_filters_signalled_minus1 ue(v) if( alf_luma_num_filters_signalled_minus1 > 0 ) for( filtIdx = 0; filtIdx < NumAlfFilters; filtIdx++ ) alf_luma_coeff_delta_idx[filtIdx] u(v) for( sfIdx = 0; sfIdx <= alf_luma_num_filters_signalled_minus1; sfIdx++ ) for( j = 0; j < 12; j++ ) { alf_luma_coeff_abs[ sfIdx ][ j ] ue(v) if( alf_luma_coeff_abs[ sfIdx ][ j ] ) alf_luma_coeff_sign[ sfIdx ][ j ] u(1) } if( alf_luma_clip_flag ) for( sfIdx = 0; sfIdx <= alf_luma_num_filters_signalled_minus1; sfIdx++ ) for( j = 0; j < 12; j++ ) alf_luma_clip_idx[ sfIdx ][ j ] u(2) }

[0319] `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 for which 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 for the filter class 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).

[0320] `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`. If `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:

[0321] If alf_luma_coeff_sign[ sfIdx ][ j ] equals 0, then the corresponding luminance filter coefficient has a positive value.

[0322] Otherwise (alf_luma_coeff_sign[ sfIdx ][ j ] equals 1), the corresponding luminance filter coefficient has a negative value.

[0323] When alf_luma_coeff_sign[ sfIdx ][ j ] does not exist, it is presumed to be equal to 0.

[0324] `alf_luma_clip_idx[ sfIdx ][ j ]` specifies the limiting index to be used before multiplying 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:

[0325] coding_tree_unit() { descriptor xCtb = CtbAddrX << CtbLog2SizeY yCtb = CtbAddrY << CtbLog2SizeY if ( sh_alf_enabled_flag ){ alf_ctb_flag[ 0 ][ CtbAddrX ][ CtbAddrY ] ae(v) if( alf_ctb_flag[ 0 ][ CtbAddrX ][ CtbAddrY ] ) { if( sh_num_alf_aps_ids_luma > 0 ) alf_use_aps_flag ae(v) if(alf_use_aps_flag) { if( sh_num_alf_aps_ids_luma > 1 ) alf_luma_prev_filter_idx ae(v) } else alf_luma_fixed_filter_idx ae(v) } }

[0326] `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 location (xCtb, yCtb), for the color components 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 location (xCtb, yCtb), for the color components indicated by `cIdx`.

[0327] 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 the 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.

[0328] 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:

[0329] If alf_use_aps_flag equals 0, then AlfCtbFiltSetIdxY[ xCtb >> CtbLog2SizeY][ yCtb >> CtbLog2SizeY ] is set to equal alf_luma_fixed_filter_idx.

[0330] Otherwise, AlfCtbFiltSetIdxY[ xCtb >> CtbLog2SizeY ][ yCtb >> CtbLog2SizeY] is set to equal to 16 + alf_luma_prev_filter_idx.

[0331] alf_luma_fixed_filter_idx specifies the fixed filter applied to the luminance CTB. The value of alf_luma_fixed_filter_idx must be in the range of 0 to 15 (inclusive).

[0332] 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:

[0333] alf_data( ) { Descriptor alf_luma_filter_signal_flag u(1) if( alf_luma_filter_signal_flag ) { alf_luma_num_alts_minus1 ue(v) for(altIdx = 0; altIdx < alf_luma_num_alts_minus1 +1; altIdx++){ alf_luma_clip_flag[altIdx] u(1) alf_luma_num_filters_signalled_minus1[altIdx] ue(v) if(alf_luma_num_filters_signalled_minus1[altIdx] > 0){ for( filtIdx = 0; filtIdx < NumAlfFilters; filtIdx++ ) alf_luma_coeff_delta_idx[altIdx][filtIdx] u(v) } for(sfIdx = 0; sfIdx <= alf_luma_num_filters_signalled_minus1[altIdx]; sfIdx++){ for(j = 0; j < 19; j++){ alf_luma_coeff_abs[altIdx][ sfIdx ][ j ] ue(v) if( alf_luma_coeff_abs[altIdx][ sfIdx ][ j ] ) alf_luma_coeff_sign[altIdx][ sfIdx ][ j ] u(1) } } if( alf_luma_clip_flag [altIdx]) for( sfIdx = 0; sfIdx <= alf_luma_num_filters_signalled_minus1[altIdx]; sfIdx++ ) for( j = 0; j <19; j++ ) alf_luma_clip_idx[altIdx][ sfIdx ][ j ] u(2) } }

[0334] `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 for which the luminance coefficients can be transmitted via signal transmission within 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).

[0335] `alf_luma_coeff_delta_idx[altIdx][filtIdx]` specifies the index of the adaptive loop filter luminance coefficient increments transmitted through the signal, indicated by `filtIdx` ranging from 0 to `NumAlfFilters-1`, for an alternative set of luminance filters with 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).

[0336] 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:

[0337] If alf_luma_coeff_sign[altIdx][sfIdx][j] equals 0, then the corresponding luminance filter coefficient has a positive value.

[0338] Otherwise (alf_luma_coeff_sign[altIdx][sfIdx][j] equals 1), the corresponding luminance filter coefficient has a negative value.

[0339] When alf_luma_coeff_sign[altIdx][sfIdx][j] does not exist, it is presumed to be equal to 0.

[0340] `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:

[0341] coding_tree_unit( ) { Descriptor xCtb = CtbAddrX << CtbLog2SizeY yCtb = CtbAddrY << CtbLog2SizeY if( sh_alf_enabled_flag ){ alf_ctb_flag[ 0 ][ CtbAddrX ][ CtbAddrY ] ae(v) if( alf_ctb_flag[ 0 ][ CtbAddrX ][ CtbAddrY ] ) { if( sh_num_alf_aps_ids_luma > 0 ) alf_use_aps_flag ae(v) if( alf_use_aps_flag ) { if( sh_num_alf_aps_ids_luma > 1 ) alt_ctb_luma_filter_alt_idx[CtbAddrX][CtbAddrY] ae(v) alf_luma_prev_filter_idx ae(v) } else alf_luma_fixed_filter_idx ae(v) } }

[0342] `alf_ctb_luma_filter_alt_idx[ xCtb >> CtbLog2SizeY ][ yCtb >> CtbLog2SizeY ]` specifies the index of the alternative luma filter for the codec tree block of the luma component applied to the luma location (xCtb, yCtb ). If `alf_ctb_luma_filter_alt_idx[ xCtb >> CtbLog2SizeY ][ yCtb >> CtbLog2SizeY ]` does not exist, it is presumed to be equal to 0.

[0343] 3.8.2 Filter Shape

[0344] In JEM, up to three diamond filter shapes can be selected for the luminance component (e.g., Figure 10 (As shown). At the image level, the filter shape used for the luma component is indicated by a signal transmission index. Each square represents a sample point, and Ci (i = 0~6 (left), 0~12 (middle), 0~20 (right)) represents the coefficient to be applied to the sample point. 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.

[0345] 3.8.3 Classification of ALF

[0346] Each 2×2 (or 4×4) block is classified into one of 25 categories. The classification index C is based on its directionality. and activity The quantization value is derived as follows:

[0347] .

[0348] In order to calculate and First, we use 1-D Laplace to calculate the gradients in the horizontal, vertical, and two diagonal directions:

[0349]

[0350]

[0351]

[0352]

[0353] index and These are the coordinates of the top left sample point in the 2×2 block, and Indicator coordinates The reconstructed sample points are then used. Then, the gradients in the horizontal and vertical directions are... The maximum and minimum values ​​are set as follows:

[0354] , ,

[0355] Furthermore, the maximum and minimum values ​​of the gradients in the two diagonal directions are set as follows:

[0356] , ,

[0357] In order to derive directionality The values ​​are compared with each other and then compared with two thresholds. and Compare:

[0358] Step 1. If and If both are true, then Set as .

[0359] Step 2. If If yes, continue from step 3; otherwise, continue from step 4.

[0360] Step 3. If ,but Set as ;otherwise Set as .

[0361] Step 4. If ,but Set as ;otherwise Set as .

[0362] Activity value Calculated as:

[0363]

[0364] It 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; instead, a single ALF coefficient set is applied to each chromaticity component.

[0365] 3.8.4 Geometric Transformation of Filter Coefficients

[0366] Before filtering each 2×2 block, geometric transformations such as rotation or diagonal and vertical flipping are applied to the filter coefficients 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 them more similar by aligning the directions of different blocks to which ALF is applied.

[0367] Three geometric transformations are introduced, including diagonal flip, vertical flip, and rotation:

[0368] diagonal:

[0369] Vertical Flip: ,

[0370] Rotation:

[0371] in It is the size of the filter, and These are coefficient coordinates, which make the position... In the top left corner, and in position In the bottom 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.

[0372] Gradient value Transformation <![CDATA[g d2 <g d1 And g h <g v ]]> No transformation <![CDATA[g d2 <g d1 And g v <g h ]]> Diagonal <![CDATA[g d1 <g d2 And g h <g v ]]> Vertical flip <![CDATA[g d1 <g d2 And g v <g h ]]> Rotation

[0373] Table 5. Mapping of gradients to transformations computed for a block

[0374] 3.8.5 Filtering Process

[0375] On the decoder side, when ALF is enabled for a block, each sample within the block... The filtered values ​​produce the sample values ​​shown below. Where L represents the filter length, Represents the filter coefficients, and This represents the decoded filter coefficients.

[0376]

[0377] Figure 12 This example illustrates relative coordinates used for a 5x5 diamond filter, 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.

[0378] 3.8.6 Nonlinear Filtering Reconstruction

[0379] Linear filtering can be reconstructed into the following expression without affecting encoding / decoding efficiency:

[0380]

[0381] in They are the same filter coefficients.

[0382] VVC introduces nonlinearity by using a simple limiting function to measure the value at neighboring sample points ( ) and the current sample value being filtered ( When the difference is too large, the influence of neighboring sample values ​​is reduced, thus making ALF more efficient. More specifically, the ALF filter is modified as follows:

[0383]

[0384] in It is a limiting function, and It is the limiting parameter, which depends on Filter coefficients. The encoder performs optimization to find the optimal values. .

[0385] Specify limiting parameters for each ALF filter Each filter coefficient transmits a limiting value via signal transmission. This means that up to 12 limiting values ​​can be transmitted via signal transmission in the bitstream for each luminance filter, and up to 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.

[0386] Because the variance of local differences in luminance is typically higher than that in chrominance, two distinct sets of filters are applied for luminance and chrominance. The maximum sample value in each set (here, a bit depth of 1024 for 10 bits) is also introduced so that clipping can be disabled if 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 has been obtained using the following formula:

[0387] AlfClip L Where M=2 10 And N=4

[0388] Similarly, the chromaticity limit table is obtained according to the following formula:

[0389] AlfClip C Where M=2 10 N=4, A=4

[0390] 3.9 Bilateral Loop Filter

[0391] 3.9.1 Bilateral Image Filter

[0392] 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 as the distance between samples decreases but also as the intensity difference increases. This improves the smoothing of overly smoothed edges. The weights are defined as follows:

[0393]

[0394] in and It is the distance in the vertical and horizontal directions, and It is the intensity difference between sample points.

[0395] 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. By 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.

[0396] 3.9.2 Bilateral Filters in Video Encoding and Decoding

[0397] 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 operate on the same input samples, each filter produces an offset, and these offsets are then added to the input samples to produce output samples, which are then clipped before proceeding to the next stage. Spatial filtering intensity Determined by the block size, smaller blocks are filtered more strongly, and the intensity of the filter is... Determined by the quantization parameters, with stronger filtering used for higher QP values. Only the four nearest samples are used, therefore the filtered sample intensity... It can be calculated as

[0398]

[0399] in Indicates the intensity of the central sample point. This indicates the intensity difference between the center sample point and the sample point above it. These represent the intensity differences between the central sample point and the sample points below, to the left, and to the right, respectively.

[0400] 4. The technical problem solved by the disclosed technical solution

[0401] The example design of the Adaptive Loop Filter (ALF) in video encoding and decoding has the following problems:

[0402] First, in the example ALF design, the precision of the coefficients used for calculation is fixed at both the encoder and decoder. Generally, increasing the coefficient precision can improve the recovery quality of the ALF.

[0403] Second, in the example ALF design, the precision of the coefficients used for computation is fixed at both the encoder and decoder. Adaptive coefficient precision can achieve a better balance between reconstruction quality and bit cost.

[0404] 5. List of solutions and implementation examples

[0405] To address the problems described above, the following summarized methods are disclosed. The 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.

[0406] It should be noted that the described method can be used as a loop filter or post-processing.

[0407] 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.

[0408] In this disclosure, an ALF processing unit can refer to a sequence, image, sub-image, strip, CTU, block, region, or sample. An ALF processing unit may include one color component or may include multiple color components.

[0409] 1) The coefficient precision of ALF can be set to the number M, which is different from the fixed number 8 used by ALF in VVC, including the sign bit.

[0410] a. In one example, the luminance ALF coefficients can be derived / quantized to M (e.g., M=9) bits of precision, including the sign of the coefficients.

[0411] b. In one example, chroma ALF coefficients can be derived / quantized to M (e.g., M=9) bits of precision, including the sign of the coefficients.

[0412] c. In one example, the precision used for the luminance ALF (Luma-ALF) coefficients in the derivation / signaling can be transmitted / predefined / derived on the decoder side.

[0413] d. In one example, the precision used for the chroma ALF (Chroma-ALF) coefficients in the derivation / signaling can be transmitted / predefined / derived on the decoder side.

[0414] e. In one example, the luminance ALF coefficients can be stored / used with N (e.g., N=9) bits of precision, including the sign of the coefficients.

[0415] f. In one example, chroma ALF coefficients can be stored / used with N (e.g., N=9) bits of precision, including the sign of the coefficients.

[0416] g. In one example, the precision used for the luminance ALF coefficients in storage / computation can be transmitted / predefined / derived on the decoder side.

[0417] h. In one example, the precision used for chroma ALF coefficients in storage / computation can be transmitted / predefined / derived on the decoder side.

[0418] i. In one example, the precision used in the derivation / storage / calculation can be the same for both the luminance ALF coefficient and the chrominance ALF coefficient.

[0419] j. In one example, the precision used in the derivation / storage / computation can be different for the luminance ALF coefficient and the chrominance ALF coefficient.

[0420] k. In one example, for the luminance ALF coefficient, the precision used in derivation / signaling and the precision used in storage / computation can be the same.

[0421] l. In one example, the precision used in derivation / signaling and the precision used in storage / computation may be different for chromatic ALF coefficients.

[0422] m. In one example, one or more syntax elements at the SPS level can be signaled / derived / predefined to indicate which coefficient precision is applied to the luminance ALF.

[0423] n. In one example, one or more syntax elements at the SPS level can be signaled / derived / predefined to indicate which coefficient precision is applied to the chroma ALF.

[0424] 2) The precision of the coefficients in ALF can vary for different components.

[0425] a. In one example, the precision of the coefficients in ALF can differ for the luminance and chrominance components.

[0426] b. In one example, for the luminance component, the precision of the coefficients in the ALF can be set to N (e.g., N=9) bits, including the sign bits.

[0427] c. In one example, for the chromaticity component, the precision of the coefficients in ALF can be set to N (e.g., N=9) bits, including the sign bit.

[0428] 3) The precision of the coefficients in ALF can vary depending on the ALF method.

[0429] a. In one example, the precision of the coefficients in ALF can differ for ALF luminance and ALF chrominance.

[0430] b. In one example, the precision of the coefficients in the ALF can differ for the ALF and for the cross-component ALF (CCALF).

[0431] 4) The precision of the coefficients in ALF can vary at different stages of ALF / ALF luminance / ALF chrominance / CCALF.

[0432] a. In one example, the precision of the coefficients in signaling / parsing can differ from the precision of the coefficients in the filtering process.

[0433] b. In one example, the coefficients may be modified before being transmitted via signaling or after being parsed.

[0434] a) In one example, the modification can be a left / right shift.

[0435] 1. For example, X’ = (X+offset)>>S, where X and X’ are the coefficients before and after the modification respectively. offset and S are integers.

[0436] 2. For example, X’ = X<<S, where X and X’ are the coefficients before and after the modification respectively. S is an integer.

[0437] b) In one example, the modification can be multiplication by a factor. The factor can be signaled / predefined / derived.

[0438] c) In one example, the modification can be addition of an offset. The offset can be signaled / predefined / derived.

[0439] d) In one example, the modification can be any other method.

[0440] c. In one example, assume the precision of the coefficients in signaling / parsing is M1, and the precision of the coefficients in the filtering process is M2. How to apply the modification can depend on M1 and / or M2.

[0441] a) For example, if M1>M2, then X’ = (X+offset)>>S, where X is the parsed coefficient, X’ is the coefficient used to filter the samples, and S is set to M1-M2. offset is an integer, for example offset = 1<<(S-1).

[0442] b) For example, if M1<M2, then X’ = X<<S, where X is the parsed coefficient, X’ is the coefficient used to filter the samples, and S is set to M2-M1.

[0443] 5) Adaptive coefficient precision can be applied to ALF.

[0444] a. In one example, the precision of the coefficients used in signaling for the luminance ALF filter can be signaled / predefined / derived.

[0445] b. In one example, the precision of the coefficients used in signaling for a luminance ALF filter set containing more than one filter can be signaled / predefined / derived.

[0446] c. In one example, the precision of the coefficients used in signaling for the chrominance ALF filter can be signaled / predefined / derived.

[0447] d. In one example, the coefficient precision used in signaling for a chroma ALF filter set containing more than one filter can be achieved through signal transmission / predefined / derived.

[0448] e. In one example, the precision of the coefficients used in storage / computation for a luminance ALF filter can be achieved through signal transmission / predefined / derived.

[0449] f. In one example, the precision of the coefficients used in storage / computation for a luminance ALF filter set containing more than one filter can be achieved through signal transmission / predefined / derived.

[0450] g. In one example, the precision of the coefficients used in storage / computation for a chroma ALF filter can be achieved through signal transmission / predefined / derived.

[0451] h. In one example, the precision of the coefficients used in storage / computation for a chroma ALF filter set containing more than one filter can be achieved through signal transmission / predefined / derived.

[0452] i. In one example, the coefficient precision index for the luminance ALF filter can be transmitted via signaling in VPS / SPS / PPS / block / APS.

[0453] a) In one example, the coefficient precision index can be encoded or decoded using fixed-length codes / EG(x) codes / unary codes / rounded binary codes, etc. These can be signed or unsigned.

[0454] b) In one example, the coefficient precision index can be encoded or decoded using at least one context model or bypass method.

[0455] j. In one example, the coefficient precision index for each luminance ALF filter set containing more than one filter can be transmitted via signaling in VPS / SPS / PPS / block / APS.

[0456] a) In one example, the coefficient precision index can be encoded or decoded using fixed-length codes / EG(x) codes / unary codes / rounded binary codes, etc. These can be signed or unsigned.

[0457] b) In one example, the coefficient precision index can be encoded or decoded using at least one context model or bypass method.

[0458] k. In one example, the coefficient precision index for each chroma ALF filter can be transmitted via signaling in VPS / SPS / PPS / block / APS.

[0459] a) In one example, the coefficient precision index can be encoded or decoded using fixed-length codes / EG(x) codes / unary codes / rounded binary codes, etc. These can be signed or unsigned.

[0460] b) In one example, the coefficient precision index can be encoded or decoded using at least one context model or bypass method.

[0461] l. In one example, the coefficient precision index for each chroma ALF filter set containing more than one filter can be transmitted via signaling in VPS / SPS / PPS / block / APS.

[0462] a) In one example, the coefficient precision index can be encoded or decoded using fixed-length codes / EG(x) codes / unary codes / rounded binary codes, etc. These can be signed or unsigned.

[0463] b) In one example, the coefficient precision index can be encoded or decoded using at least one context model or bypass method.

[0464] m. In one example, the coefficients may be modified before or after being transmitted through the signal, depending on the precision index of the transmitted coefficients for the luminance ALF filter.

[0465] n. In one example, the coefficients may be modified before or after signal transmission, depending on the precision index of the coefficients transmitted for a luminance ALF filter set containing more than one filter.

[0466] o. In one example, the coefficients may be modified before or after being transmitted through the signal, depending on the precision index of the transmitted coefficients for the chroma ALF filter.

[0467] p. In one example, the coefficients may be modified before or after being transmitted through the signal, depending on the precision index of the coefficients transmitted through the signal for a chroma ALF filter set containing more than one filter.

[0468] q. In one example, one or more syntax elements at the SPS level can be signaled / derived / predefined to indicate whether the adaptive coefficient precision is applied to the luminance ALF.

[0469] r. In one example, one or more syntax elements at the SPS level can be signaled / derived / predefined to indicate whether the adaptive coefficient precision is applied to the chroma ALF.

[0470] 6) ALF coefficients can be transmitted / encoded using the exponential Columbus encoding / decoding method.

[0471] a. In one example, the coefficients in a filter can be classified into N (e.g., N=2) groups.

[0472] a) In one example, the classification rule can be based on the number of inputs with a single coefficient.

[0473] b) In one example, the classification rule can be based on a symmetric design of a coefficient.

[0474] c) In one example, the coefficients applied to an input can be assigned to a group.

[0475] d) In one example, the coefficients applied to the two inputs can be assigned to a group.

[0476] e) In one example, coefficients applied to M (e.g., M=4) inputs can be assigned to a group.

[0477] b. In one example, the parameters in the Exponential Columbus codec can be adaptive for each filter.

[0478] a) In one example, for the coefficients in a filter, the parameter K can be transmitted via signaling / predefined / derived.

[0479] b) In one example, for the coefficients in a filter, the parameter K-offset can be transmitted / predefined / derived via signal transmission.

[0480] c) In one example, the parameters K and K-offset can be encoded or decoded using fixed-length codes / EG(x) codes / unary codes / rounded binary codes, etc. These can be signed or unsigned.

[0481] d) In one example, the parameters of K and K-offset can be encoded or decoded using at least one context model or bypass method.

[0482] e) In one example, the parameters K and K-offset can be transmitted via signaling in the APS.

[0483] f) In one example, the coefficients in a filter can use the same K.

[0484] g) In one example, the coefficients in a filter can use different K values.

[0485] 1. In one example, the coefficients applied to the two inputs can be used to decode the exponential Golomb code using K.

[0486] 2. In one example, the coefficients applied to an input can be used with K to decode the exponential Golomb code.

[0487] 3. In one example, the coefficients applied to an input can be used to decode the exponential Golomb code using K+K-offset.

[0488] c. In one example, the parameters in the Exponential Columbus codec can be adaptive for each set of coefficients in a filter.

[0489] a) In one example, for each set of coefficients in a filter, parameter K can be transmitted / predefined / transmitted via signaling.

[0490] b) In one example, for each set of coefficients in a filter, the parameter K-offset can be transmitted / predefined / transmitted via signaling.

[0491] c) In one example, parameters K and K-offset can be encoded and decoded using fixed-length codes / EG(x) codes / unary codes / rounded binary codes, etc. These can be signed or unsigned.

[0492] d) In one example, parameters K and K-offset can be encoded and decoded using at least one context model or bypass method.

[0493] e) In one example, parameters K and K-offset can be transmitted via signals in the APS.

[0494] f) In one example, the coefficients applied to the two inputs can be used To decode the exponential Golomb code.

[0495] g) In one example, the coefficients applied to an input can be used To decode the exponential Golomb code.

[0496] h) In one example, the coefficients applied to an input can be used + K-offset to decode the exponential Golomb code.

[0497] d. In one example, the parameters in the exponential Columbus codec can be adaptive for each set of coefficients in a filter set containing more than one filter.

[0498] a) In one example, for each set of coefficients in a filter set, parameter K can be transmitted / predefined / transmitted via signaling.

[0499] b) In one example, for each set of coefficients in a filter set, the parameter K-offset can be transmitted / predefined / transmitted via signaling.

[0500] c) In one example, the parameters K and K-offset can be encoded or decoded using fixed-length codes / EG(x) codes / unary codes / rounded binary codes, etc. These can be signed or unsigned.

[0501] d) In one example, parameters K and K-offset can be encoded and decoded using at least one context model or bypass method.

[0502] e) In one example, parameters K and K-offset can be transmitted via signals in the APS.

[0503] f) In one example, the coefficients applied to the two inputs can be used To decode the exponential Golomb code.

[0504] g) In one example, the coefficients applied to an input can be used To decode the exponential Golomb code.

[0505] h) In one example, the coefficients applied to an input can be used + K-offset to decode the exponential Golomb code.

[0506] 7) In one example, the disclosed methods may be used in post-processing and / or pre-processing.

[0507] 8) In one example, the above methods can be used in combination.

[0508] 9) Alternatively, the above methods can be used alone.

[0509] 10) In one example, the adaptive coefficient precision described for the ALF method can be applied to any loop filtering tool, preprocessing or postprocessing filtering method (including but not limited to ALF / CCALF or any other filtering method) in video encoding and decoding.

[0510] a. In one example, adaptive coefficient precision can be applied to loop filtering methods.

[0511] a) In one example, adaptive coefficient precision can be applied to ALF.

[0512] b) In one example, adaptive coefficient precision can be applied to CCALF.

[0513] c) In one example, the accuracy of the adaptive coefficients can be applied to BF.

[0514] d) In one example, adaptive coefficient precision can be applied to SAO.

[0515] e) In one example, adaptive coefficient precision can be applied to CCSAO.

[0516] f) Alternatively, adaptive coefficient accuracy can be applied to other loop filtering methods.

[0517] b. In one example, adaptive coefficient precision can be applied to preprocessing filtering methods.

[0518] c. In one example, adaptive coefficient precision can be applied to post-processing filtering methods.

[0519] 11) 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.

[0520] 12) Whether and / or how the methods disclosed above can be used to transmit signals in a bitstream.

[0521] 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 / DCI / PPS / APS / strip header / piece group header.

[0522] b. In one example, whether and / or how the methods disclosed above can be applied can be transmitted via signal at PB / TB / CB / PU / TU / CU / VPDU / CTU / CTU lines / strips / pieces / sub-pictures / other types of areas containing more than one sample point or pixel.

[0523] 13) Whether and / or how to apply the methods disclosed above may depend on encoding and decoding information such as block size, color format, single / dual tree segmentation, color components, and stripe / picture type.

[0524] 6. References

[0525] J. Strom, P. Wennersten, J. Enhorn, D. Liu, K. Andersson, and R. Sjoberg, “Bilateral Loop Filter in Combination with SAO,” in proceeding of IEEE PictureCoding Symposium (PCS), Nov. 2019.

[0526] Figure 13 This is a block diagram illustrating an example video processing system 4000 in which various techniques disclosed herein may be implemented. Various implementations may include some or all of the components of system 4000. System 4000 may include an input 4002 for receiving video content. The video content may be received in a raw or uncompressed format, such as 8 or 10-bit multi-component pixel values, or 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).

[0527] 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 stored or communicatively transmitted bitstream (or encoded / decoded) representation of the video received at input 4002 may be used by component 4008 to generate pixel values ​​or displayable video that is sent 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.

[0528] 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 Electronic Devices (IDE), etc. The technologies 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.

[0529] Figure 14 This 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) 4102 can be configured to implement one or more methods described herein. The memories(multiple) 4104 can be used to store data and code for implementing the methods and techniques described herein. The video processing circuitry 4106 can be used to implement some of the techniques described herein in hardware circuitry. In some embodiments, the video processing circuitry 4106 may be at least partially included in the processor 4102, such as a graphics coprocessor.

[0530] Figure 15 This is a flowchart of an example method 4200 for video processing. At step 4202, method 4200 includes determining that the adaptive coefficient precision for the adaptive loop filter (ALF) is set to a number M, where the number M differs from the fixed number used at the encoder or decoder for the adaptive coefficient precision of the ALF. At step 4204, a conversion between visual media data and a bitstream is performed based on the adaptive coefficient precision for the ALF set to the number M. According to the example, the conversion in step 4204 may include encoding at the encoder or decoding at the decoder.

[0531] 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.

[0532] Figure 16This is a block diagram illustrating an example video encoding / decoding system 4300 from which the techniques of this disclosure can be utilized. 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.

[0533] 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 a 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.

[0534] 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.

[0535] The video encoder 4314 and the video decoder 4324 can operate according to video compression standards, such as the High Efficiency Video Codec (HEVC) standard, the Multi-Functional Video Codec (VVC) standard, and other existing and / or further standards.

[0536] 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 of the techniques disclosed herein. The video encoder 4400 includes multiple functional components. The techniques 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 of the techniques described in this disclosure.

[0537] 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.

[0538] 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 containing the current video block.

[0539] 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.

[0540] 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.

[0541] 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).

[0542] 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.

[0543] 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.

[0544] 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.

[0545] 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.

[0546] 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.

[0547] 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.

[0548] 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.

[0549] 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.

[0550] 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 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.

[0551] 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.

[0552] 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.

[0553] 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.

[0554] 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.

[0555] 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 generate a reconstructed video block associated with the current block and store it in the buffer 4413.

[0556] 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.

[0557] The entropy coding unit 4414 can receive data from other functional components of the video encoder 4400. When the entropy coding unit 4414 receives data, it can perform one or more entropy coding operations to generate entropy-coded data and output a bitstream including the entropy-coded data.

[0558] 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 of the techniques disclosed herein. In the example shown, the video decoder 4500 includes multiple functional components. The techniques 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 of the techniques described in this disclosure.

[0559] 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.

[0560] 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.

[0561] 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.

[0562] The motion compensation unit 4502 can use the interpolation filter used by the video encoder 4400 during the encoding of the video block to calculate the interpolation for sub-integer pixels of the 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 the prediction block.

[0563] 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.

[0564] Intra-prediction unit 4503 can use, for example, an intra-prediction mode received in the bitstream to form prediction blocks from spatially adjacent blocks. Dequantization unit 4504 dequantizes the quantized video block coefficients provided in the bitstream and decoded by entropy decoding unit 4501. Inverse transform unit 4505 applies an inverse transform.

[0565] The reconstruction unit 4506 can add the residual block to the corresponding predicted 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.

[0566] Figure 19This is a schematic diagram of the 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 an offset and by applying a finite impulse response (FIR) filter, and by utilizing the encoded / decoded side information through signal transmission offset 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.

[0567] The encoder 4600 also includes a motion estimation / compensation (ME / MC) component 4610 and an intra-frame prediction component 4608 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 for filtering before these images are stored in reference image buffer 4612.

[0568] The following provides a list of preferred solutions as examples.

[0569] The following solutions illustrate examples of the techniques discussed in this article.

[0570] 1. A method for processing video data, comprising: determining an adaptive coefficient precision for an adaptive loop filter (ALF) set to a digital M; and performing a conversion between visual media data and a bitstream based on the adaptive coefficient precision.

[0571] 2. The method according to Solution 1, wherein the precision of the adaptive coefficient is different from the fixed number 8 including the sign bit.

[0572] 3. The method according to any one of solutions 1-2, wherein the luminance ALF coefficient or chrominance ALF coefficient is quantized to an M-bit precision including the coefficient sign.

[0573] 4. The method according to any one of solutions 1-3, wherein the accuracy of the adaptive coefficients used in the derivation or signaling for the luminance ALF coefficients or chrominance ALF coefficients is determined, predefined, or derived at the decoder via signal transmission.

[0574] 5. The method according to any one of solutions 1-4, wherein the luminance ALF coefficient or chrominance ALF coefficient is stored or used with N-bit precision including coefficient signs.

[0575] 6. The method according to any one of solutions 1-5, wherein the accuracy of the adaptive coefficients used in storage or computation for the luminance ALF coefficients or chrominance ALF coefficients is determined at the decoder by signal transmission, predefined or derived.

[0576] 7. The method according to any one of solutions 1-6, wherein the adaptive coefficients used in the derivation, storage or calculation of the luminance ALF coefficient and the chrominance ALF coefficient are of the same or different precision.

[0577] 8. The method according to any one of solutions 1-7, wherein the accuracy of the adaptive coefficients used in the derivation or signaling and in storage or computation for the luminance ALF coefficients or chrominance ALF coefficients is the same or different.

[0578] 9. The method according to any one of solutions 1-8, wherein one or more syntax elements at the Sequence Parameter Set (SPS) level are signaled, derived, or predefined to indicate which coefficient precision is applied to the luminance ALF or chrominance ALF.

[0579] 10. The method according to any one of solutions 1-9, wherein the precision of the coefficients in ALF is different for different components.

[0580] 11. The method according to any one of solutions 1-10, wherein the precision of the coefficients in ALF is different for the luminance component and the chrominance component.

[0581] 12. The method according to any one of solutions 1-11, wherein the precision of the coefficients in the ALF is set to N bits, including sign bits, for the luminance component or the chrominance component.

[0582] 13. The method according to any one of solutions 1-12, wherein the precision of the coefficients in the ALF is different for different ALF methods.

[0583] 14. The method according to any one of Solutions 1-13, wherein the precision of the coefficients in the ALF is different for ALF luminance and ALF chrominance, or the precision of the coefficients in the ALF is different for ALF and cross-component ALF (CCALF).

[0584] 15. The method according to any one of Solutions 1-14, wherein the precision of the coefficients in the ALF is different at different stages of ALF, ALF luminance, ALF chrominance or CCALF.

[0585] 16. The method according to any one of Solutions 1-15, wherein the precision of the coefficients in signaling or parsing is different from the precision of the coefficients in the filtering process.

[0586] 17. The method according to any one of Solutions 1-16, wherein the coefficients are modified before being signaled or after being parsed, or the modification includes a left shift or a right shift, or X' = (X+offset)>>S, where X and X' are the coefficients before and after modification respectively, and offset and S are integers, or X' = X<<S, where X and X' are the coefficients before and after modification respectively, and S is an integer, or the modification includes multiplication by a factor, where the factor is signaled, predefined or derived, or the modification includes addition of an offset, where the offset is signaled, predefined or derived, or the modification includes other methods.

[0587] 18. The method according to any one of Solutions 1-17, wherein when the precision of the coefficients in signaling or parsing is M1 and the precision of the coefficients in the filtering process is M2, the application of the modification depends on M1 or M2, or M1>M2, X' =(X+offset)>>S, where X is the parsed coefficient, X' is the coefficient used to filter the samples, S is set to M1-M2, and offset is an integer, for example offset = 1<<(S-1), or M1<M2, X' = X<<S, where X is the parsed coefficient, X' is the coefficient used to filter the samples, and S is set to M2-M1.

[0588] 19. The method according to any one of Solutions 1-18, wherein adaptive coefficient precision is applied to the ALF.

[0589] 20. The method according to any one of solutions 1-19, wherein the precision of the coefficients used in signaling for a luminance ALF filter, a luminance ALF filter set containing more than one filter, a chrominance ALF filter, or a chrominance ALF filter set containing more than one filter is transmitted via signal transmission, predefined, or derived.

[0590] 21. The method according to any one of solutions 1-20, wherein the precision of the coefficients used in storage or computation for a luminance ALF filter, a luminance ALF filter set containing more than one filter, a chrominance ALF filter, or a chrominance ALF filter set containing more than one filter is transmitted via signal transmission, predefined, or derived.

[0591] 22. The method according to any one of solutions 1-21, wherein, for a luma ALF filter, for each luma ALF filter set containing more than one filter, for a chroma ALF filter, or for each luma ALF filter set containing more than one filter, the coefficient precision index is transmitted via signal in a video parameter set (VPS), sequence parameter set (SPS), picture parameter set (PPS), block or adaptive parameter set (APS), wherein the coefficient precision index is encoded or decoded using a signed or unsigned fixed-length code, an exponential Golomb (EG(x)) code, a unary code, or a rounded binary code, or the coefficient precision index is encoded or decoded using at least one context model or bypass method.

[0592] 23. The method according to any one of solutions 1-22, wherein the coefficients are modified, before being transmitted through the signal or after being parsed, depending on the precision index of the coefficients transmitted through the signal for the luminance ALF filter, a set of luminance ALF filters containing more than one filter, a chrominance ALF filter, or a set of luminance ALF filters containing more than one filter.

[0593] 24. The method according to any one of solutions 1-23, wherein one or more syntax elements at the SPS level are signaled, derived, or predefined to indicate whether the adaptive coefficient precision is applied to the luma ALF or the chroma ALF.

[0594] 25. The method according to any one of solutions 1-24, wherein the ALF coefficients are transmitted or encoded / decoded using exponential Golomb codes.

[0595] 26. The method according to any one of solutions 1-25, wherein the coefficients in a filter are classified into N groups, wherein the classification rule is based on the number of inputs to a coefficient, or the classification rule is based on a symmetric design of a coefficient, or coefficients applied to one input are assigned to one group, or coefficients applied to two inputs are assigned to one group, or coefficients applied to M inputs are assigned to one group.

[0596] 27. The method according to any one of solutions 1-26, wherein the parameters in the exponential Golomb codec are adaptive for each filter, or for the coefficients in a filter, the parameter K is transmitted by signaling, predefined, or derived, or for the coefficients in a filter, the parameter K-offset is transmitted by signaling, predefined, or derived, or the parameters K and K-offset are encoded or decoded using signed or unsigned fixed-length codes, EG(x) codes, unary codes, or rounded binary codes, or the parameters K and K-offset are encoded or decoded using at least one context model or bypass method, or the parameters K and K-offset are transmitted by signaling in the APS, or the coefficients in a filter use the same or different K, or the coefficients applied to one or two inputs use K to decode the exponential Golomb code, or the coefficients applied to one input use K+K-offset to decode the exponential Golomb code.

[0597] 28. The method according to any one of solutions 1-27, wherein the parameters in the exponential Columbus encoding / decoding are adaptive for each set of coefficients in a filter, or for each set of coefficients in a filter, the parameters K or K-offset are transmitted via signaling, predefined, or transmitted via signaling, or the parameters K and K-offset are encoded / decoded using signed or unsigned fixed-length codes, EG(x) codes, unary codes, or rounded binary codes, or at least one context model or bypass method is used to encode / decode the parameters K and K-offset, or the parameters K and K-offset are transmitted via signaling in the APS, or applied to coefficients of one or two inputs using... , or + K-offset to decode the exponential Golomb code.

[0598] 29. The method according to any one of solutions 1-28, wherein the parameters in the exponential Columbus encoding / decoding are adaptive for each set of coefficients in a filter set containing more than one filter, or for each set of coefficients in a filter set, the parameters K or K-offset are transmitted via signaling, predefined, or transmitted via signaling, or the parameters K and K-offset are encoded / decoded using signed or unsigned fixed-length codes, EG(x) codes, unary codes, or rounded binary codes, or at least one context model or bypass method is used to encode / decode the parameters K and K-offset, or the parameters K and K-offset are transmitted via signaling in the APS, or applied to coefficients of one or two inputs using... , or + K-offset to decode the exponential Golomb code.

[0599] 30. The method according to any one of solutions 1-29, wherein the accuracy of the adaptive coefficients is used in post-processing and / or pre-processing.

[0600] 31. The method according to any one of solutions 1-30, wherein the methods are applied in combination or individually.

[0601] 32. The method according to any one of solutions 1-31, wherein the adaptive coefficient precision of the ALF is applied to any loop filtering tool, preprocessing or postprocessing filter in video encoding and decoding, including but not limited to ALF / CCALF or any other filter, or wherein the adaptive coefficient precision is applied to a loop filter, ALF, CCALF, BF, SAO, CCSAO, another loop filter, preprocessing filter or postprocessing filter.

[0602] 33. The method according to any one of solutions 1-32, wherein the video unit is 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.

[0603] 34. The method according to any one of solutions 1-33, wherein the use of the method is transmitted by signaling in a bitstream, or wherein the use is transmitted by signaling at the sequence level / picture group level / picture level / strip level / piece group level, or is included in the sequence header / picture header / SPS / VPS / DPS / DCI / PPS / APS / strip header / piece group header, or wherein the use is transmitted by signaling at PB / TB / CB / PU / TU / CU / VPDU / CTU / CTU line / strip / piece / subpicture / other types of areas containing more than one sample or pixel.

[0604] 35. The method according to any one of solutions 1-34, wherein the use of the method depends on encoding / decoding information including block size, color format, single / dual tree segmentation, color components, or stripe / picture type.

[0605] 36. 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 according to any one of solutions 1-35.

[0606] 37. 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 according to any one of solutions 1-35.

[0607] 38. 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 an adaptive coefficient precision for an adaptive loop filter (ALF) set to a digital M; and generating the bitstream based on the determination.

[0608] 39. A method for storing a bitstream of video, comprising: determining an adaptive coefficient precision for an adaptive loop filter (ALF) set to a digital M; generating the bitstream based on the determination; and storing the bitstream in a non-transitory computer-readable recording medium.

[0609] 40. A method, apparatus or system described in this disclosure.

[0610] 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.

[0611] 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.

[0612] 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 one or more 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 or control of the operation of a 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, such as 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, optical, or electromagnetic signals, which are generated to encode information to be transmitted to a suitable receiver device.

[0613] 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 in question, or in multiple co-located files (e.g., a file 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.

[0614] 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).

[0615] Processors suitable for executing computer programs include, for example, general-purpose and special-purpose microprocessors, and any one or more processors of any type of digital computer. Typically, a 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, or receive data from or transfer data to one or more mass storage devices via operative coupling, or both. However, a computer does not necessarily have such devices. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and 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. Processors and memory may be supplemented by or incorporated into special-purpose logic circuitry.

[0616] 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 a particular art. 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 the claimed combination may be removed from that combination, and the claimed combination may be for sub-combinations or variations thereof.

[0617] 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.

[0618] 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.

[0619] When there are no intermediate components other than the 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 the 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 direct coupling and indirect coupling. The use of the term "about" means including a range of ±10% of the following figures, unless otherwise specified.

[0620] 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 present examples are to be considered illustrative rather than restrictive and are not intended to be limited to the details set forth herein. For example, various elements or components may be combined or integrated into another system, or certain features may be omitted or not implemented.

[0621] 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 electrically, mechanically, or otherwise. Other examples of changes, substitutions, and modifications that can be determined by those skilled in the art can be made without departing from the spirit and scope of this disclosure.

Claims

1. A method for processing video data, comprising: The adaptive coefficient precision for the adaptive loop filter (ALF) is determined to be set to a digital M, wherein the digital M is different from the fixed digital value used at the encoder or decoder for the adaptive coefficient precision of the ALF; and The conversion between visual media data and bitstream is performed based on the accuracy of the adaptive coefficients for the ALF, which are set to the number M.

2. The method according to claim 1, wherein, According to the Multifunction Video Codec (VVC) standard, the fixed number used by the encoder or the decoder for the adaptive coefficient precision of the ALF is 8, including the sign bit.

3. The method according to any one of claims 1-2, wherein, The luminance ALF coefficients are derived or quantized to M-bit precision, including the coefficient sign bits.

4. The method according to any one of claims 1-2, wherein, The chromatic ALF coefficients are derived or quantized to M-bit precision, including the coefficient sign bits.

5. The method according to any one of claims 1-4, wherein, M is greater than 8.

6. The method according to any one of claims 1-5, wherein, The accuracy of the adaptive coefficients for the luminance ALF coefficients is included in the bitstream, derived, or predefined.

7. The method according to any one of claims 1-5, wherein, The accuracy of the adaptive coefficients for the chroma ALF coefficients is included in the bitstream, derived, or predefined.

8. The method according to any one of claims 1-7, wherein, The luminance ALF coefficients are stored or used with an N-bit precision, the N bits including the coefficient sign bit.

9. The method according to any one of claims 1-7, wherein, The chroma ALF coefficients are stored or used with an N-bit precision, the N bits including the coefficient sign bit.

10. The method according to any one of claims 1-9, wherein, The precision of the adaptive coefficients used in storage or computation for the luminance ALF coefficients is included in the bitstream, derived, or predefined.

11. The method according to any one of claims 1-9, wherein, The precision of the adaptive coefficients used in storage or computation for the chroma ALF coefficients is included in the bitstream, derived, or predefined.

12. The method according to any one of claims 1-11, wherein, The accuracy of the adaptive coefficients used in derivation, storage, or calculation is the same for both the luminance ALF coefficients and the chrominance ALF coefficients.

13. The method according to any one of claims 1-11, wherein, The precision of the adaptive coefficients used in derivation, storage, or calculation differs for the luminance ALF coefficients and the chrominance ALF coefficients.

14. The method according to any one of claims 1-11, wherein, For the luminance ALF coefficients, the accuracy of the adaptive coefficients used in derivation or signaling is the same as the accuracy of the adaptive coefficients used in storage or computation.

15. The method according to any one of claims 1-11, wherein, The accuracy of the adaptive coefficients used in the derivation or signaling of the chromaticity ALF coefficients is different from the accuracy of the adaptive coefficients used in storage or computation.

16. The method according to any one of claims 1-15, wherein, One or more syntax elements at the Sequence Parameter Set (SPS) level are included in, derived, or predefined in the bitstream to indicate whether the adaptive coefficient precision is applied to the luminance ALF.

17. The method according to any one of claims 1-15, wherein, One or more syntax elements at the Sequence Parameter Set (SPS) level are included in, derived, or predefined in the bitstream to indicate whether the adaptive coefficient precision is applied to the chroma ALF.

18. The method according to any one of claims 1-17, wherein, The accuracy of the adaptive coefficients in the ALF is different for different components.

19. The method according to claim 18, wherein, The accuracy of the adaptive coefficients in the ALF is different for the luminance component and the chrominance component.

20. The method according to claim 18, wherein, The precision of the adaptive coefficient for the luminance component is set to N, including the sign bits.

21. The method according to claim 18, wherein, The adaptive coefficient precision for the chrominance component is set to N, including a sign bit.

22. The method according to any one of claims 20-21, wherein, N is greater than 8.

23. The method according to any one of claims 1-17, wherein, The adaptive coefficient precision in the ALF is different for different ALF methods.

24. The method according to claim 23, wherein, The adaptive coefficient precision of the coefficients in the ALF is different for ALF luminance and ALF chrominance.

25. The method according to claim 23, wherein, The adaptive coefficient precision of the coefficients in the ALF is different for the ALF and cross-component ALF (CCALF).

26. The method according to any one of claims 1-17, wherein, The adaptive coefficient precision in the ALF is different for different stages of the ALF, ALF luminance, ALF chrominance, or cross-component ALF (CCALF).

27. The method according to claim 26, wherein, The adaptive coefficient precision encoded in the bitstream or parsed from the bitstream is different from the adaptive coefficient precision used in the filtering process.

28. The method according to claim 26, wherein, The coefficients are modified before being encoded in the bitstream or after being parsed from the bitstream.

29. The method according to claim 28, wherein, The modification of the coefficients includes a left shift or a right shift.

30. The method according to claim 29, wherein, The modification is performed according to the formula X' = (X + offset) >> S, where X and X' are the coefficients before and after the modification respectively, and where offset and S are integers.

31. The method according to claim 29, wherein, The modification is performed according to the formula X' = X << S, where X and X' are the coefficients before and after the modification respectively, and where S is an integer.

32. The method according to claim 28, wherein, The modification of the coefficients includes multiplication by a factor, and where the factor is included in the bitstream, derived, or predefined.

33. The method according to claim 28, wherein, The modification of the coefficients includes addition of an offset, and where the offset is included in the bitstream, derived, or predefined.

34. The method according to claim 26, wherein, The adaptive coefficient precision included in the bitstream or parsed from the bitstream is M1, the adaptive coefficient precision used in the filtering process is M2, and the modification of the adaptive coefficient precision depends on at least one of M1 and M2.

35. The method according to claim 34, wherein, When M1 > M2, X' = (X + offset) >> S, X is the parsed coefficient, X' is the coefficient used to filter the sample, S is set to M1 - M2, and offset is an integer determined according to offset = 1 << (S - 1).

36. The method according to claim 34, wherein, When M1 < M2, X' = X << S, X is the parsed coefficient, X' is the coefficient used to filter the sample, and S is set to M2 - M1.

37. The method according to any one of claims 1-36, further comprising applying the adaptive coefficient precision to the ALF.

38. The method according to claim 37, wherein, The adaptive coefficient precision is used for a luminance ALF filter and is included in the bitstream, derived, or predefined.

39. The method according to claim 37, wherein, The adaptive coefficient precision is used for a set of luminance ALF filters including multiple filters and is included in the bitstream, derived, or predefined.

40. The method of claim 37, wherein, The adaptive coefficient precision is used for a chrominance ALF filter and is included in the bitstream, derived, or predefined.

41. The method according to claim 37, wherein, The adaptive coefficient precision is used for a set of chrominance ALF filters including multiple filters and is included in the bitstream, derived, or predefined.

42. The method according to claim 37, wherein, The accuracy of the adaptive coefficients for the luminance ALF filter used in storage or computation is included in the bitstream, derived, or predefined.

43. The method according to claim 37, wherein, The accuracy of the adaptive coefficients used in storage or computation for a set of luminance ALF filters containing multiple filters is included in the bitstream, derived, or predefined.

44. The method of claim 37, wherein, The accuracy of the adaptive coefficients for the chroma ALF filter used in storage or computation is included in the bitstream, derived, or predefined.

45. The method of claim 37, wherein, The accuracy of the adaptive coefficients used in storage or computation for a chroma ALF filter set containing multiple filters is included in the bitstream, derived, or predefined.

46. ​​The method according to claim 37, wherein, The adaptive coefficient precision index of the luminance ALF is included in the Video Parameter Set (VPS), Sequence Parameter Set (SPS), Picture Parameter Set (PPS), and Block or Adaptive Parameter Set (APS).

47. The method of claim 37, wherein, The adaptive coefficient precision index for each luminance ALF filter set containing multiple filters is included in the Video Parameter Set (VPS), Sequence Parameter Set (SPS), Picture Parameter Set (PPS), Block or Adaptive Parameter Set (APS).

48. The method of claim 37, wherein, The adaptive coefficient precision index for each chroma ALF is included in the Video Parameter Set (VPS), Sequence Parameter Set (SPS), Picture Parameter Set (PPS), Block or Adaptive Parameter Set (APS).

49. The method of claim 37, wherein, The adaptive coefficient precision index for each chroma ALF filter set containing multiple filters is included in the Video Parameter Set (VPS), Sequence Parameter Set (SPS), Picture Parameter Set (PPS), Block or Adaptive Parameter Set (APS).

50. The method according to any one of claims 46-49, wherein, The adaptive coefficient precision index is encoded and decoded using fixed-length codes, exponential Golomb (EGx) codes, unary codes, rounding binary codes, context models, or bypass methods, and wherein the adaptive coefficient precision index is signed or unsigned.

51. The method according to claim 37, wherein, Whether the coefficients are modified before being encoded into the bitstream or after being parsed from the bitstream depends on the coefficient precision index for the luminance ALF in the bitstream.

52. The method according to claim 37, wherein, Whether the coefficients are modified before being encoded into the bitstream or after being parsed from the bitstream depends on the coefficient precision index of the luminance ALF set, which includes multiple filters.

53. The method according to claim 37, wherein, Whether the coefficients are modified before being encoded into the bitstream or after being parsed from the bitstream depends on the coefficient precision index for the chroma ALF in the bitstream.

54. The method according to claim 37, wherein, Whether the coefficients are modified before being encoded into the bitstream or after being parsed from the bitstream depends on the coefficient precision index of the chroma ALF set, which includes multiple filters.

55. The method of claim 37, wherein, One or more syntax elements at the Sequence Parameter Set (SPS) level are included in, derived, or predefined in the bitstream to indicate whether the adaptive coefficient precision is applied to the luminance ALF.

56. The method according to claim 37, wherein, One or more syntax elements at the Sequence Parameter Set (SPS) level are included in, derived, or predefined in the bitstream to indicate whether the adaptive coefficient precision is applied to the chroma ALF.

57. The method according to any one of claims 1-56, wherein, The coefficients for the ALF in the bitstream are encoded and decoded using Exponential Golomb (EGx) codes.

58. The method according to claim 57, wherein, The coefficients in a filter are classified into N groups, where N is an integer.

59. The method according to claim 57, wherein, The classification rule for the filter is based on the number of input coefficients.

60. The method of claim 57, wherein, The classification rule for the filter is based on a symmetric design of a coefficient.

61. The method according to claim 57, wherein, The coefficients applied to an input are assigned to a group.

62. The method according to claim 57, wherein, The coefficients applied to the two inputs are assigned to a group.

63. The method according to claim 57, wherein, The coefficients applied to the M inputs are assigned to a group, where M is an integer.

64. The method according to any one of claims 1-63, wherein, The parameters in the Exponential Golomb (EGx) code are adaptive for each filter.

65. The method according to claim 64, wherein, For the coefficients in a filter, the parameter K is included in the bitstream, derived, or predefined.

66. The method according to claim 64, wherein, For the coefficients in a filter, the parameter K-offset is included in the bitstream, derived, or predefined.

67. The method according to claim 64, wherein, The parameters K and K-offset are encoded and decoded using fixed-length codes, exponential Golomb codes (EGx codes), unary codes, or rounded binary codes.

68. The method according to claim 64, wherein, The parameters K and K-offset are encoded and decoded using at least one context model or bypass method.

69. The method according to claim 64, wherein, The parameters K and K-offset are included in the adaptive parameter set (APS) of the bitstream.

70. The method of claim 64, wherein, The coefficients in a filter use the same K.

71. The method according to claim 64, wherein, The coefficients in a filter use different K values.

72. The method according to claim 71, wherein, The coefficients applied to the two inputs are used with K to decode the exponential Golomb (EGx) code.

73. The method according to claim 71, wherein, The coefficients applied to an input are decoded using K to obtain the exponential Golomb (EGx) code.

74. The method according to claim 71, wherein, The coefficients applied to an input are decoded using the K+K-offset to obtain the exponential Golomb (EGx) code.

75. The method according to any one of claims 1-74, wherein, In Exponential Columbus (EGx) encoding and decoding, the parameters are adaptive for each set of coefficients in a filter.

76. The method according to claim 75, wherein, For each set of coefficients in a filter, parameter K is included in the bitstream, predefined, or included in the bitstream.

77. The method according to claim 75, wherein, For each set of coefficients in a filter, the parameter K-offset is included in the bitstream, is predefined, or is included in the bitstream.

78. The method according to claim 75, wherein, The parameters K and K-offset are encoded and decoded using fixed-length codes, exponential Golomb codes (EGx codes), unary codes, or rounded binary codes, and wherein the parameters K and K-offset are signed or unsigned.

79. The method according to claim 75, wherein, The parameters K and K-offset are encoded and decoded using at least one context model or bypass method.

80. The method according to claim 75, wherein, The parameters K and K-offset are included in the adaptive parameter set (APS) of the bitstream.

81. The method according to claim 75, wherein, Coefficients applied to two inputs To decode the Exponential Columbus (EGx) code.

82. The method according to claim 75, wherein, The coefficients applied to an input are used To decode the Exponential Columbus (EGx) code.

83. The method according to claim 75, wherein, The coefficients applied to an input are used + K-offset to decode Exponential Columbus (EGx) code.

84. The method according to any one of claims 1-83, wherein, The parameters in the Exponential Columbus (EGx) codec are adaptive for each set of coefficients in a filter set containing multiple filters.

85. The method according to claim 84, wherein, For each set of coefficients in a filter, parameter K is included in the bitstream, predefined, or included in the bitstream.

86. The method according to claim 84, wherein, For each set of coefficients in a filter, the parameter K-offset is included in the bitstream, is predefined, or is included in the bitstream.

87. The method according to claim 84, wherein, The parameters K and K-offset are encoded and decoded using fixed-length codes, exponential Golomb codes (EGx codes), unary codes, or rounded binary codes, and wherein the parameters K and K-offset are signed or unsigned.

88. The method according to claim 84, wherein, The parameters K and K-offset are encoded and decoded using at least one context model or bypass method.

89. The method according to claim 84, wherein, The parameters K and K-offset are included in the adaptive parameter set (APS) of the bitstream.

90. The method according to claim 84, wherein, Coefficients applied to two inputs To decode the Exponential Columbus (EGx) code.

91. The method according to claim 84, wherein, The coefficients applied to an input are used To decode the Exponential Columbus (EGx) code.

92. The method according to claim 84, wherein, The coefficients applied to an input are used + K-offset to decode Exponential Columbus (EGx) code.

93. The method according to any one of claims 1-92, wherein, Any of the disclosed methods may be used in one or more of the post-processing and pre-processing processes.

94. The method according to any one of claims 1-93, wherein, Any of the disclosed methods may be used in combination.

95. The method according to any one of claims 1-93, wherein, Any one of the disclosed methods may be used alone.

96. The method according to any one of claims 1-95, wherein, Any of the disclosed methods for the adaptive coefficient accuracy of ALF is applied to any loop filtering tool, preprocessing filtering method, or postprocessing filtering method in video encoding and decoding, including ALF, CCALF, or any other filtering method.

97. The method according to claim 96, wherein, The accuracy of the adaptive coefficients is applied to the loop filtering method.

98. The method according to claim 97, wherein, The accuracy of the adaptive coefficients is applied to ALF.

99. The method according to claim 97, wherein, The accuracy of the adaptive coefficients is applied to CCALF.

100. The method according to claim 97, wherein, The adaptive coefficient accuracy is applied to bilateral filtering (BF).

101. The method according to claim 97, wherein, The accuracy of the adaptive coefficients is applied to sample adaptive compensation (SAO) filtering.

102. The method according to claim 97, wherein, The accuracy of the adaptive coefficients is applied to cross-component sample adaptive compensation (CCSAO) filtering.

103. The method according to claim 96, wherein, The accuracy of the adaptive coefficients is applied to the preprocessing filtering method.

104. The method according to claim 96, wherein, The accuracy of the adaptive coefficients is applied to the post-processing filtering method.

105. The method according to any one of claims 1-104, wherein, The adaptive coefficient precision is used for video units, wherein the video unit is a sequence, picture, sub-picture, strip, slice, codec tree unit (CTU), CTU row, CTU group, codec unit (CU), prediction unit (PU), transform unit (TU), codec tree block (CTB), codec block (CB), prediction block (PB), transform block (TB), or any other region containing more than one luminance or chrominance sample or pixel.

106. The method according to any one of claims 1-105, wherein, Whether and / or how one or more of the disclosed methods are applied in the bitstream is transmitted via signal.

107. The method according to any one of claims 1-106, wherein, Whether and / or how one or more of the disclosed methods are applied at the sequence level, picture group level, picture level, strip level, slice group level, or are transmitted via signaling, or are included in the sequence header, picture header, SPS, video parameter set (VPS), dependency parameter set (DPS), decoding capability information (DCI), PPS, APS, strip header, or slice group header.

108. The method according to any one of claims 1-106, wherein, Whether and / or how one or more of the disclosed methods are applied in the prediction block (PB), transform block (TB), codec block (CB), prediction unit (PU), transform unit (TU), codec unit (CU), virtual pipeline data unit (VPDU), codec tree unit (CTU), CTU row, strip, slice, sub-picture, or any other region containing more than one sample or pixel is transmitted via signal.

109. The method according to any one of claims 1-108, wherein, Whether and / or how one or more of the disclosed methods are applied depends on the encoding / decoding information, wherein the encoding / decoding information includes one or more of block size, color format, single-tree segmentation or dual-tree segmentation, color components, stripe type or picture type.

110. The method according to any one of claims 1-109, wherein, The conversion includes encoding the media data into the bitstream.

111. The method according to any one of claims 1-109, wherein, The conversion includes decoding the media data from the bitstream.

112. 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 according to any one of claims 1-111.

113. A non-transitory computer-readable medium comprising a computer program product for use by a video codec apparatus, the computer program product comprising computer-executable instructions stored on the non-transitory computer-readable medium, which, when executed by a processor, cause the video codec apparatus to perform the method according to any one of claims 1-111.

114. 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 adaptive coefficient precision for the adaptive loop filter (ALF) is determined to be set to a digital M, wherein the digital M is different from the fixed digital value used at the encoder or decoder for the adaptive coefficient precision of the ALF; and The conversion between visual media data and bitstream is performed based on the accuracy of the adaptive coefficients for the ALF, which are set to the number M.

115. A method for storing a video bitstream, comprising: The adaptive coefficient precision for the adaptive loop filter (ALF) is determined to be set to a digital M, wherein the digital M is different from the fixed digital value used at the encoder or decoder for the adaptive coefficient precision of the ALF. The bitstream is generated using the adaptive coefficient precision; and The bit stream is stored in a non-transitory computer-readable recording medium.

116. A method, apparatus or system described in this disclosure.

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