Region adaptive loop filter for video coding

1. A method of video coding, executable by a processor, comprising:

receiving a bitstream of data corresponding to an image having pre-determined multiple regions;

determining a number from the bitstream corresponding to a number of filters in an adaptive loop filter associated with the image;

decoding a region index to filter an index lookup table;

decoding filter coefficients of the filters in the adaptive loop filter; and

decoding the image based on the decoded filter coefficients and the decoded region index to filter the index lookup table.

2. The method of claim 1 , wherein the index is between 1 and the number of pre-determined regions, inclusively.

3. The method of claim 2 , where based on the index being 1 or the number of pre-determined regions, wherein the region index to filter the index lookup table is not encoded in the bitstream, and wherein the region index is decoded using a default value.

4. The method of claim 2 , wherein based on the index being between 2 and the number of pre-determined regions minus 1, inclusively, wherein the region index to filter the index lookup table is decoded from the bitstream.

5. The method of claim 1 , wherein the decoding the image comprises:

merging a set of regions of the image from among the pre-determined multiple regions; and

decoding the merged set of regions using the same filter.

6. The method of claim 5 , wherein the set of regions is merged based on minimizing a rate distortion cost associated with merging the set of regions.

7. The method of claim 5 , further comprising signaling the filter coefficients associated with the multiple regions in the bitstream with one or more syntax elements.

8. A computer system for video coding, the computer system comprising:

one or more computer-readable non-transitory storage media configured to store computer program code; and

one or more computer processors configured to access said computer program code and operate as instructed by said computer program code, said computer program code including:

receiving code configured to cause the one or more computer processors to receive a bitstream of data corresponding to an image having pre-determined multiple regions;

determining code configured to cause the one or more computer processors to determine a number from the bitstream corresponding to a number of filters in an adaptive loop filter associated with the image;

first decoding code configured to cause the one or more computer processors to decode a region index to filter an index lookup table;

second decoding code configured to cause the one or more computer processors to decode filter coefficients of the filters in the adaptive loop filter; and

third decoding code configured to cause the one or more computer processors to decode the image based on the decoded filter coefficients and the region index to filter the index lookup table.

9. The computer system of claim 8 , wherein the index is between 1 and the number of pre-determined regions, inclusively.

10. The computer system of claim 9 , where based on the index being 1 or the number of pre-determined regions, wherein the region index to filter the index lookup table is not encoded in the bitstream, and wherein the region index is decoded using a default value.

11. The computer system of claim 9 , wherein based on the index being between 2 and the number of pre-determined regions minus 1, inclusively, wherein the region index to filter the index lookup table is decoded from the bitstream.

12. The computer system of claim 8 , wherein the second decoding code comprises:

merging code configured to cause the one or more computer processors to merge a set of regions of the image from among the pre-determined multiple regions; and

decoding code configured to cause the one or more computer processors to decode the merged set of regions using the same filter.

13. The computer system of claim 12 , wherein the set of regions is merged based on minimizing a rate distortion cost associated with merging the set of regions.

14. The computer system of claim 12 , further comprising signaling the filter coefficients associated with the pre-determined multiple regions in the bitstream with one or more syntax elements.

15. A non-transitory computer readable medium having stored thereon a computer program for video coding, the computer program configured to cause one or more computer processors to:

receive a bitstream of data corresponding to an image having pre-determined multiple regions;

determine a number from the bitstream corresponding to the number of filters in an adaptive loop filter associated with the image;

decode a region index to filter an index lookup table;

decode filter coefficients of the filters in the adaptive loop filter; and

decode the image based on the decoded filter coefficients and the decoded region index to filter the index lookup table.

16. The computer readable medium of claim 15 , wherein the index is between 1 and the number of pre-determined regions, inclusively.

17. The computer readable medium of claim 16 , where based on the index being 1 or the number of pre-determined regions, wherein the region index to filter index lookup table is not encoded in the bitstream, and wherein the region index is decoded using a default value.

18. The computer readable medium of claim 16 , wherein based on the index being between 2 and the number of pre-determined regions minus 1, inclusively, wherein the region index to filter the index lookup table is decoded from the bitstream.

19. The computer readable medium of claim 15 , wherein the computer program is further configured to cause one or more computer processors to:

merge a set of regions of the image from among the pre-determined multiple regions; and

decode the merged set of regions using the same filter.

20. The computer readable medium of claim 19 , wherein the set of regions is merged based on minimizing a rate distortion cost associated with merging the set of regions.