# US 11,451,834 B2 · Method and apparatus for cross-component filtering > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,451,834 B2 - Document ID: US11451834B2 - Status: Granted - Kind: B2 - Application number: 17/010,403 - Filed: 2020-09-02 - Published: 2021-03-18 - Granted: 2022-09-20 - Earliest claimed: 2019-09-16 - Assignees: Tencent America LLC - Applicants: Tencent America LLC - Inventors: Xiang Li; Xin Zhao; Yixin Du; Liang Zhao; Shan Liu - Web page: https://patentgrep.com/patent/US11451834B2 ## CPC - H04N 19/82: involving filtering within a prediction loop - H04N 19/117: Filters, e.g. for pre-processing or post-processing (sub-band filter banks H04N19/635) - H04N 19/132: Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking - H04N 19/176: the region being a block, e.g. a macroblock - H04N 19/186: the unit being a colour or a chrominance component - H04N 19/44: Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder - H04N 19/46: Embedding additional information in the video signal during the compression process (H04N19/517, H04N19/68, H04N19/70 take precedence) - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract Aspects of the disclosure provide a method and an apparatus including processing circuitry for video decoding. The processing circuitry decodes coded information of a chroma coding block (CB) from a coded video bitstream. The coded information indicates that a cross-component filter is applied to the chroma CB and indicates a chroma subsampling format and a chroma sample type. The processing circuitry determines a filter shape of the cross-component filter based on at least one of the chroma subsampling format and the chroma sample type. The processing circuitry generates a first intermediate CB by applying a loop filter to the chroma CB and generates a second intermediate CB by applying the cross-component filter having the determined filter shape to the corresponding luma CB. The processing circuitry determines a filtered chroma CB based on the first intermediate CB and the second intermediate CB. ## Claims ### Claim 1 A method for video decoding in a decoder, comprising: decoding coded information of a chroma coding block (CB) from a coded video bitstream, the coded information indicating that a cross-component filter is applied to the chroma CB, the coded information further indicating a chroma subsampling format and a chroma sample type that indicates a relative position of a chroma sample with respect to at least one luma sample in a corresponding luma CB; determining a filter shape of the cross-component filter applied to the chroma CB based on at least one of the chroma subsampling format or the chroma sample type; generating a first intermediate CB by applying a loop filter to the chroma CB; generating a second intermediate CB by applying, to the corresponding luma CB, the cross-component filter applied to the chroma CB and having the determined filter shape; and determining a filtered chroma CB based on the first intermediate CB and the second intermediate CB by combining the loop filtered chroma CB with the cross-component filtered luma CB, wherein a number of filter coefficients of the cross-component filter is signaled in the coded video bitstream; and the determining the filter shape includes determining the filter shape of the cross-component filter based on the number of filter coefficients and the at least one of the chroma subsampling format or the chroma sample type. ### Claim 2 (depends on 1) The method of claim 1, wherein the chroma sample type is signaled in the coded video bitstream. ### Claim 3 (depends on 1) The method of claim 1, wherein the chroma subsampling format is 4:2:0; the at least one luma sample includes four luma samples that are a top-left sample, a top-right sample, a bottom-left sample, and a bottom-right sample; the chroma sample type is one of six chroma sample types 0-5 indicating six relative positions 0-5, respectively, and the six relative positions 0-5 of the chroma sample correspond to a left-center position between the top-left and the bottom-left samples, a center position of the four luma samples, a top left position co-located with the top-left sample, a top-center position between the top-left and the top-right samples, a bottom left position co-located with the bottom-left sample, and a bottom-center position between the bottom-left and the bottom-right samples, respectively; and the determining the filter shape includes determining the filter shape of the cross-component filter based on the chroma sample type. ### Claim 4 (depends on 3) The method of claim 3, wherein the coded video bitstream includes a cross-component linear model (CCLM) flag indicating that the chroma sample type is 0 or 2. ### Claim 5 (depends on 1) The method of claim 1, wherein the cross-component filter is a cross-component adaptive loop filter (CC-ALF) and the loop filter is an adaptive loop filter (ALF). ### Claim 6 (depends on 1) The method of claim 1, wherein a range of filter coefficients of the cross-component filter is less than or equal to K bits and K is a positive integer. ### Claim 7 (depends on 6) The method of claim 6, wherein the filter coefficients of the cross-component filter are coded using fixed-length coding. ### Claim 8 (depends on 6) The method of claim 6, further comprising: shifting luma sample values of the corresponding luma CB to have a dynamic range of 8 bits based on the dynamic range of the luma sample values being larger than 8 bits, K being 8 bits, wherein the generating the second intermediate CB includes applying the cross-component filter having the determined filter shape to the shifted luma sample values. ### Claim 9 A method for video decoding in a decoder, comprising: decoding coded information of a chroma coding block (CB) from a coded video bitstream, the coded information indicating that a cross-component filter is applied to the chroma CB based on a corresponding luma CB; generating a down-sampled luma CB by applying a down-sampling filter to the corresponding luma CB, a chroma horizontal subsampling factor, and a chroma vertical subsampling factor between the chroma CB and the down-sampled luma CB being one; generating a first intermediate CB by applying a loop filter to the chroma CB; generating a second intermediate CB by applying, to the down-sampled luma CB, the cross-component filter applied to the chroma CB, a filter shape of the cross-component filter being independent of a chroma subsampling format and a chroma sample type of the chroma CB, the chroma sample type indicating a relative position of a chroma sample with respect to at least one luma sample in the corresponding luma CB; and determining a filtered chroma CB based on the first intermediate CB and the second intermediate CB by combining the loop filtered chroma CB with the cross-component filtered down-sampled luma CB, wherein a number of filter coefficients of the cross-component filter is signaled in the coded video bitstream; and the filter shape of the cross-component filter is determined based on the number of filter coefficients. ### Claim 10 (depends on 9) The method of claim 9, wherein the down-sampling filter corresponds to a filter applied to co-located luma samples in a CCLM mode. ### Claim 11 (depends on 9) The method of claim 9, wherein the down-sampling filter is a {1, 2, 1; 1, 2, 1}/8 filter and the chroma subsampling format is 4:2:0. ### Claim 12 (depends on 9) The method of claim 9, wherein the filter shape of the cross-component filter is one of a 7×7 diamond shape, a 7×7 square shape, a 5×5 diamond shape, a 5×5 square shape, a 3×3 diamond shape, and a 3×3 square shape. ### Claim 13 An apparatus for video decoding, comprising: processing circuitry configured to: decode coded information of a chroma coding block (CB) from a coded video bitstream, the coded information indicating that a cross-component filter is applied to the chroma CB, the coded information further indicating a chroma subsampling format and a chroma sample type that indicates a relative position of a chroma sample with respect to at least one luma sample in a corresponding luma CB; determine a filter shape of the cross-component filter applied to the chroma CB based on at least one of the chroma subsampling format or the chroma sample type; generate a first intermediate CB by applying a loop filter to the chroma CB; generate a second intermediate CB by applying, to the corresponding luma CB, the cross-component filter applied to the chroma CB and having the determined filter shape; and determine a filtered chroma CB based on the first intermediate CB and the second intermediate CB by combining the loop filtered chroma CB with the cross-component filtered luma CB, wherein a number of filter coefficients of the cross-component filter is signaled in the coded video bitstream; and the filter shape of the cross-component filter is determined based on the number of filter coefficients and the at least one of the chroma subsampling format or the chroma sample type. ### Claim 14 (depends on 13) The apparatus of claim 13, wherein the chroma sample type is signaled in the coded video bitstream. ### Claim 15 (depends on 13) The apparatus of claim 13, wherein the chroma subsampling format is 4:2:0; the at least one luma sample includes four luma samples that are a top-left sample, a top-right sample, a bottom-left sample, and a bottom-right sample; the chroma sample type is one of six chroma sample types 0-5 indicating six relative positions 0-5, respectively, and the six relative positions 0-5 of the chroma sample correspond to a left-center position between the top-left and the bottom-left samples, a center position of the four luma samples, a top left position co-located with the top-left sample, a top-center position between the top-left and the top-right samples, a bottom left position co-located with the bottom-left sample, and a bottom-center position between the bottom-left and the bottom-right samples, respectively; and the processing circuitry is configured to determine the filter shape of the cross-component filter based on the chroma sample type. ### Claim 16 (depends on 15) The apparatus of claim 15, wherein the coded video bitstream includes a cross-component linear model (CCLM) flag indicating that the chroma sample type is 0 or 2. ### Claim 17 (depends on 13) The apparatus of claim 13, wherein the cross-component filter is a cross-component adaptive loop filter (CC-ALF) and the loop filter is an adaptive loop filter (ALF). ### Claim 18 (depends on 13) The apparatus of claim 13, wherein a range of filter coefficients of the cross-component filter is less than or equal to K bits and K is a positive integer.