# US 2013/0156097 A1 · Adaptive Loop Filtering (ALF) for Video Coding > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0156097 A1 - Document ID: US20130156097A1 - Status: Published application - Kind: A1 - Application number: 13/720,995 - Filed: 2012-12-19 - Published: 2013-06-20 - Earliest claimed: 2011-12-20 - Assignees: Texas Instruments Incorporated - Inventors: Madhukar Budagavi; Minhua Zhou - Web page: https://patentgrep.com/patent/US20130156097A1 ## CPC - H04N 19/82: involving filtering within a prediction loop - H04N 19/46: Embedding additional information in the video signal during the compression process (H04N19/517, H04N19/68, H04N19/70 take precedence) - H04N 19/86: involving reduction of coding artifacts, e.g. of blockiness - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract A method for adaptive loop filtering of a reconstructed picture in a video encoder is provided that includes determining whether or not sample adaptive offset (SAO) filtering is applied to the reconstructed picture, and using adaptive loop filtering with no offset for the reconstructed picture when the SAO filtering is determined to be applied to the reconstructed picture. ## Claims ### Claim 1 A method for adaptive loop filtering of a reconstructed picture in a video encoder, wherein parameters of an adaptive loop filter comprise a plurality of coefficients and an offset, the method comprising: determining whether or not sample adaptive offset (SAO) filtering is applied to the reconstructed picture; and using adaptive loop filtering with no offset for the reconstructed picture when the SAO filtering is determined to be applied to the reconstructed picture. ### Claim 2 (depends on 1) The method of claim 1, further comprising: using adaptive loop filtering with a computed offset for the reconstructed picture when the SAO filtering is determined to not be applied. ### Claim 3 (depends on 1) The method of claim 1, wherein using adaptive loop filtering with no offset comprises: determining filter parameter values for an adaptive loop filter to be applied to a selected portion of reconstructed pixels in the reconstructed picture, wherein the offset is assumed to be zero and wherein only values of the plurality of coefficients are determined; applying the adaptive loop filter to at least some pixels of the portion of reconstructed pixels using the values of the plurality of coefficients, wherein a value of the offset is assumed to be zero; and signaling the filter parameter values in a compressed video bit stream. ### Claim 4 (depends on 3) The method of claim 3, wherein applying the adaptive loop filter comprises: computing a filtered pixel value q(x,y) for each pixel p(x,y) of the at least some pixels as per q(x,y)=Σi=0Ncipi(x,y), wherein N+1 is a number of the plurality of filter coefficients and ci are the filter coefficients. ### Claim 5 (depends on 3) The method of claim 3, wherein the portion of reconstructed pixels is a region of the reconstructed picture selected from a plurality of regions of the reconstructed picture. ### Claim 6 (depends on 3) The method of claim 3, further comprising: signaling in the compressed video bit stream that adaptive loop filtering with no offset is used, and wherein signaling the filter parameter values comprises signaling only the values of the plurality of coefficients. ### Claim 7 (depends on 3) The method of claim 3, wherein signaling the filter parameter values comprises signaling the values of the plurality of coefficients and a value of zero for the offset. ### Claim 8 (depends on 3) The method of claim 3, wherein signaling the filter parameter values comprises: signaling filter parameter values for each row of regions in the reconstructed picture, wherein the filter parameter values for a row are signaled one of immediately prior to data for the row or immediately following the data for the row. ### Claim 9 (depends on 3) The method of claim 3, wherein signaling the filter parameter values comprises: signaling filter parameter values for each region in the reconstructed picture, wherein the filter parameter values for a region are signaled one of immediately prior to data for the region or immediately following the data for the region. ### Claim 10 (depends on 2) The method of claim 2, wherein using adaptive loop filtering with a computed offset comprises: determining filter parameter values for an adaptive loop filter to be applied to a selected portion of reconstructed pixels in the reconstructed picture, wherein values of the plurality of coefficients and a value of the offset are determined; applying the adaptive loop filter to at least some pixels of the portion of reconstructed pixels using the values of the plurality of coefficients and the value of the offset; and signaling the filter parameter values in a compressed video bit stream. ### Claim 11 A method for adaptive loop filtering of a reconstructed picture in a video decoder, wherein parameters of an adaptive loop filter comprise a plurality of coefficients and an offset, the method comprising: determining whether or not adaptive loop filtering with no offset is to be applied to the reconstructed picture; decoding filter parameters for an adaptive loop filter wherein a value of the offset is not included in the filter parameters when adaptive loop filtering with no offset is to be applied; and applying the adaptive loop filter to at least some pixels of a portion of the reconstructed picture using the decoded filter parameters, wherein a value of the offset is assumed to be zero. ### Claim 12 (depends on 11) The method of claim 11, wherein applying the adaptive loop filter comprises: computing a filtered pixel value q(x,y) for each pixel p(x,y) of the at least some pixels as per q(x,y)=Σi=0Ncipi(x,y), wherein N+1 is a number of the plurality of filter coefficients and ci are the filter coefficients. ### Claim 13 (depends on 11) The method of claim 11, wherein decoding filter parameters comprises decoding filter parameters for each row of regions in the reconstructed picture, wherein the filter parameter values for a row are signaled one of immediately prior to data for the row or immediately following the data for the row. ### Claim 14 (depends on 11) The method of claim 11, wherein decoding filter parameter values comprises decoding filter parameter values for each region in the reconstructed picture, wherein the filter parameter values for a region are signaled one of immediately prior to data for the region or immediately following the data for the region. ### Claim 15 An apparatus configured for adaptive loop filtering of a reconstructed picture in a video encoder, wherein parameters of an adaptive loop filter comprise a plurality of coefficients and an offset, the apparatus comprising: means for determining whether or not sample adaptive offset (SAO) filtering is applied to the reconstructed picture; means for using adaptive loop filtering with no offset for the reconstructed picture when the SAO filtering is determined to be applied to the reconstructed picture; and means for using adaptive loop filtering with a computed offset for the reconstructed picture when the SAO filtering is determined to not be applied. ### Claim 16 (depends on 15) The apparatus of claim 15, wherein the means for using adaptive loop filtering with no offset comprises: means for determining filter parameter values for an adaptive loop filter to be applied to a selected portion of reconstructed pixels in the reconstructed picture, wherein the offset is assumed to be zero and wherein only values of the plurality of coefficients are determined; means for applying the adaptive loop filter to at least some pixels of the portion of reconstructed pixels using the values of the plurality of coefficients, wherein a value of the offset is assumed to be zero; and means for signaling the filter parameter values in a compressed video bit stream. ### Claim 17 (depends on 16) The apparatus of claim 16, wherein the means for applying the adaptive loop filter comprises: means for computing a filtered pixel value q(x,y) for each pixel p(x,y) of the at least some pixels as per q(x,y)=Σi=0Ncipi(x,y), wherein N+1 is a number of the plurality of filter coefficients and ci are the filter coefficients. ### Claim 18 (depends on 16) The apparatus of claim 16, wherein the portion of reconstructed pixels is a region of the reconstructed picture selected from a plurality of regions of the reconstructed picture. ### Claim 19 (depends on 16) The apparatus of claim 16, further comprising: means for signaling that adaptive loop filtering with no offset is used in the compressed video bit stream, and wherein the means for signaling the filter parameter values signals only the values of the plurality of coefficients. ### Claim 20 (depends on 16) The apparatus of claim 16, wherein the means for signaling the filter parameter values signals the values of the plurality of coefficients and a value of zero for the offset.