# US 11,909,965 B2 · Method and apparatus for non-linear adaptive loop filtering in video coding > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,909,965 B2 - Document ID: US11909965B2 - Status: Granted - Kind: B2 - Application number: 17/819,362 - Filed: 2022-08-12 - Published: 2022-12-08 - Granted: 2024-02-20 - Earliest claimed: 2019-01-25 - Assignees: Hfi Innovation Inc. - Applicants: HFI Innovation Inc. - Inventors: Chen-Yen Lai; Ching-Yeh Chen; Tzu-Der Chuang; Yu-Wen Huang - Web page: https://patentgrep.com/patent/US11909965B2 ## CPC - H04N 19/117: Filters, e.g. for pre-processing or post-processing (sub-band filter banks H04N19/635) - H04N 19/159: Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction - H04N 19/167: Position within a video image, e.g. region of interest [ROI] - H04N 19/186: the unit being a colour or a chrominance component - H04N 19/82: involving filtering within a prediction loop - H04N 19/86: involving reduction of coding artifacts, e.g. of blockiness - H04N 19/176: the region being a block, e.g. a macroblock - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract Methods and apparatus for Adaptive Loop Filter (ALF) processing of reconstructed video are disclosed. According to one implementation, a method receives reconstructed pixels of a current block and determines one or more clipping values for the ALF processing, wherein a target clipping value is always signaled at an encoder side or parsed at a decoder side even if the target clipping value is zero. The method then derives a current ALF output for the current block, wherein the current ALF output has a weighted sum of clipped differences and each of the original differences is calculated between a first reconstructed pixel at a non-center filter location and a center reconstructed pixel at a center filter location, and each of the original differences is clipped according to a corresponding clipping value to form one clipped difference. The method then provides filtered-reconstructed pixels. ## Claims ### Claim 1 A method for Adaptive Loop Filter (ALF) processing of reconstructed video, the method comprising: receiving reconstructed pixels, wherein the reconstructed pixels comprise a current block; determining one or more clipping values for the ALF processing, wherein a target clipping value is always signaled at an encoder side or parsed at a decoder side even if the target clipping value is zero; deriving a current ALF output for the current block, wherein the current ALF output comprises a weighted sum of clipped differences of original differences and each of the original differences is calculated between a first reconstructed pixel at a non-center filter location and a center reconstructed pixel at a center filter location, and wherein each of the original differences is clipped according to a corresponding clipping value to form one clipped difference; and providing filtered-reconstructed pixels, wherein the filtered-reconstructed pixels comprise the current ALF output. ### Claim 2 (depends on 1) The method of claim 1, wherein said one or more clipping values are signaled in a slice, tile or tile group. ### Claim 3 An apparatus for Adaptive Loop Filter (ALF) processing of reconstructed video, the apparatus comprising one or more electronic circuits or processors arranged to: receive reconstructed pixels, wherein the reconstructed pixels comprise a current block; determine one or more clipping values for the ALF processing, wherein a target clipping value is always signaled at an encoder side or parsed at a decoder side even if the target clipping value is zero; derive a current ALF output for the current block, wherein the current ALF output comprises a weighted sum of clipped differences of original differences and each of the original differences is calculated between a first reconstructed pixel at a non-center filter location and a center reconstructed pixel at a center filter location, and wherein each of the original differences is clipped according to a corresponding clipping value to form one clipped difference; and provide filtered-reconstructed pixels, wherein the filtered-reconstructed pixels comprise the current ALF output. ### Claim 4 A method for Adaptive Loop Filter (ALF) processing of reconstructed video, the method comprising: receiving reconstructed pixels, wherein the reconstructed pixels comprise a current block; determining one or more clipping values for the ALF processing, wherein said one or more clipping values are encoded at an encoder side or decoded at a decoder side using a fixed-length code; deriving a current ALF output for the current block, wherein the current ALF output comprises a weighted sum of clipped differences of original differences and each of the original differences is calculated between a first reconstructed pixel at a non-center filter location and a center reconstructed pixel at a center filter location, and wherein each of the original differences is clipped according to a corresponding clipping value to form one clipped difference; and providing filtered-reconstructed pixels, wherein the filtered-reconstructed pixels comprise the current ALF output. ### Claim 5 (depends on 4) The method of claim 4, wherein the fixed-length code corresponds to two-bit codes. ### Claim 6 (depends on 4) The method of claim 4, wherein the fixed-length code corresponds to truncated unary codes. ### Claim 7 (depends on 4) The method of claim 4, wherein said one or more clipping values are signaled in a slice, tile or tile group. ### Claim 8 An apparatus for Adaptive Loop Filter (ALF) processing of reconstructed video, the apparatus comprising one or more electronic circuits or processors arranged to: receive reconstructed pixels, wherein the reconstructed pixels comprise a current block; determine one or more clipping values for the ALF processing, wherein said one or more clipping values are encoded at an encoder side or decoded at a decoder side using a fixed-length code; derive a current ALF output for the current block, wherein the current ALF output comprises a weighted sum of clipped differences of original differences and each of the original differences is calculated between a first reconstructed pixel at a non-center filter location and a center reconstructed pixel at a center filter location, and wherein each of the original differences is clipped according to a corresponding clipping value to form one clipped difference; and provide filtered-reconstructed pixels, wherein the filtered-reconstructed pixels comprise the current ALF output.