Adaptive loop filter with adaptive parameter set
A method for signaling adaptive loop filter (ALF) settings is provided. A video decoder receives data from a bitstream for a block of pixels to be decoded as a current block of a current picture of a video. The video decoder parses whether to use adaptive parameter set (APS) for filtering the current block without determining whether to select a particular APS from a plurality of APSs. When the APS is used to filter the current block, the video decoder parses a first filter selection index for selecting a filter from a set of filters in the APS. When the APS is not used to filter the current block, the video decoder signals a second filter selection index for selecting a filter from a set of default fixed filters. The video decoder filters the current block based on the selected filter. The video decoder outputs the filtered current block.
1. A video decoding method comprising:
receiving data from a bitstream for a block of pixels to be decoded as a current block of a current picture of a video;
parsing whether to use adaptive parameter set (APS) for filtering the current block without determining whether to select a particular APS from a plurality of APSs;
when the APS is used to filter the current block, parsing a first filter selection index for selecting a filter from a set of filters in the APS;
when the APS is not used to filter the current block, parsing a second filter selection index for selecting a filter from a set of default fixed filters;
filtering the current block based on the selected filter; and
outputting the filtered current block.
2. The method of claim 1 , wherein the APS comprises information for deriving filter coefficients and clipping values for adaptive loop filters (ALF).
3. The method of claim 1 , wherein the current block is a coding tree block (CTB).
4. The method of claim 3 , wherein the APS comprises a plurality of sets of filters applicable to luma and chroma CTBs.
5. The method of claim 1 , wherein the APS is selected from a plurality of APSs by using an APS identifier signaled in a slice header.
6. The method of claim 5 , wherein the selected APS is for providing a filter for chroma pixels of the current block.
7. The method of claim 5 , wherein the APS identifier identifies temporal filters used in a current slice or tile group that encompass the current block.
8. The method of claim 1 , wherein parameters for filters of chroma component are included in an APS for luma component.
9. The method of claim 1 , wherein a flag indicating whether to use APS for filtering the current block is inferred to be true or false based on chroma format, chroma indicator, or slice type.
10. A video encoding method comprising:
receiving raw pixel data for a block of pixels to be encoded as a current block of a current picture of a video into a bitstream;
signaling whether to use adaptive parameter set (APS) for filtering the current block without determining whether to select a particular APS from a plurality of APSs for filtering the current block;
when the APS is used to filter the current block, signaling a first filter selection index for selecting a filter from a set of filters in the APS;
when the APS is not used to filter the current block, signaling a second filter selection index for selecting a filter from a set of default fixed filters; and
encoding the current block by applying the selected filter.
11. An electronic apparatus comprising:
a video decoder circuit configured to perform operations comprising:
receiving data from a bitstream for a block of pixels to be decoded as a current block of a current picture of a video;
parsing whether to use adaptive parameter set (APS) for filtering the current block without determining whether to select a particular APS from a plurality of APSs;
when the APS is used to filter the current block, parsing a first filter selection index for selecting a filter from a set of filters in the APS;
when the APS is not used to filter the current block, parsing a second filter selection index for selecting a filter from a set of default fixed filters
filtering the current block based on the selected filter; and
outputting the filtered current block.