US 11,991,353 B2
Adaptive loop filter
Jonathan Taquet, Talensac (FR); Christophe Gisquet, Acigne (FR); Guillaume Laroche, Saint Aubin d'Aubigné (FR); and Patrice Onno, Rennes (FR)
Assigned to Canon Kabushiki Kaisha, Tokyo (JP)
Appl. No. 17/434,361
Filed by CANON KABUSHIKI KAISHA, Tokyo (JP)
PCT Filed Mar. 5, 2020, PCT No. PCT/EP2020/055888
§ 371(c)(1), (2) Date Aug. 26, 2021,
PCT Pub. No. WO2020/182620, PCT Pub. Date Sep. 17, 2020.
Claims priority of application No. 1903187 (GB), filed on Mar. 8, 2019; application No. 1903584 (GB), filed on Mar. 15, 2019; application No. 1908937 (GB), filed on Jun. 21, 2019; and application No. 1919037 (GB), filed on Dec. 20, 2019.
Prior Publication US 2022/0159249 A1, May 19, 2022
Int. Cl. H04N 19/117 (2014.01); H04N 19/176 (2014.01); H04N 19/186 (2014.01); H04N 19/46 (2014.01); H04N 19/82 (2014.01)
CPC H04N 19/117 (2014.11) [H04N 19/176 (2014.11); H04N 19/186 (2014.11); H04N 19/46 (2014.11); H04N 19/82 (2014.11)] 22 Claims
OG exemplary drawing
 
1. A method of Adaptive Loop Filtering, the method comprising:
obtaining for a slice containing one or more coding tree blocks, data indicating a number of alternative chroma filters for Adaptive Loop Filtering, wherein the number can be more than one;
obtaining, for a coding tree block in the slice containing one or more coding tree blocks, an alternative filter index identifying one of the one or more available alternative chroma filters, the number of which is indicated by the data; and
selecting the one of the one or more alternative chroma filters identified by the alternative filter index to filter chroma image data in the coding tree block,
wherein the method further comprises:
obtaining a flag for the one or more alternative chroma filters, the flag indicating whether a chroma filter is a linear filter or a non-linear filter; and
obtaining one or more clipping value indices for the one or more alternative chroma filters when the obtained flag indicates that a chroma filter is a non-linear filter,
wherein a clipping value index for Adaptive Loop Filtering in the one or more clipping value indices of a non-linear filter indicates a clipping value used for a coefficient of a chroma filter in the one or more chroma filters,
wherein the clipping values are restricted to values which are powers of two.