Methods and systems for cross-component adaptive loop filter

1. A method for video processing using Cross-Component Adaptive Loop Filter (CCALF), comprising:

filtering decoded video content using a CCALF, wherein the CCALF is a 24-tap 9×9 filter having a cross shape defined as:

[

C

0

C

1

C

2

C

3

C

9

C

10

C

11

C

12

C

4

C

13

C

14

C

15

C

16

C

17

C

18

C

19

C

20

C

5

C

21

C

22

C

23

C

24

C

6

C

7

C

8

]

wherein C 0 to C 24 are filter coefficients of the 24-tap 9×9 filter.

2. The method according to claim 1 , wherein the decoded video content comprises a video slice, and the 24-tap 9×9 filter is applied to all coding tree units (CTUs) of the video slice.

3. The method according to any one of claim 1 , wherein values of the filter coefficients are integer values between −64 and +64.

4. The method according to claim 1 , wherein the filter coefficients are coded using variable length code.

5. A method for video processing using Cross-Component Adaptive Loop Filter (CCALF), comprising:

filtering video content using a CCALF, wherein the CCALF is a 24-tap 9×9 filter having a cross shape defined as:

[

C

0

C

1

C

2

C

3

C

9

C

10

C

11

C

12

C

4

C

13

C

14

C

15

C

16

C

17

C

18

C

19

C

20

C

5

C

21

C

22

C

23

C

24

C

6

C

7

C

8

]

wherein C 0 to C 24 are filter coefficients of the 24-tap 9×9 filter.

6. The method according to claim 5 , wherein the video content comprises a video slice, and the 24-tap 9×9 filter is applied to all coding tree units (CTUs) of the video slice.

7. The method according to any one of claim 5 , wherein values of the filter coefficients are integer values between −64 and +64.

8. The method according to claim 5 , wherein the filter coefficients are coded using variable length code.

9. A non-transitory computer readable medium storing a bitstream, wherein the bitstream comprises a first index associated with encoded video data, the first index identifying a Cross-Component Adaptive Loop Filter (CCALF), wherein the CCALF is a 24-tap 9×9 filter having a cross shape defined as:

[

C

0

C

1

C

2

C

3

C

9

C

10

C

11

C

12

C

4

C

13

C

14

C

15

C

16

C

17

C

18

C

19

C

20

C

5

C

21

C

22

C

23

C

24

C

6

C

7

C

8

]

wherein C 0 to C 24 are filter coefficients of the 24-tap 9×9 filter, and the first index causes a decoder to filter decoded video content using the 24-tap 9×9 filter.

10. The non-transitory computer readable medium according to claim 9 , wherein the bitstream further comprises a coded syntax element, the encoded syntax element comprising filter coefficients of the 24-tap 9×9 filter.

11. The non-transitory computer readable medium according to claim 10 , wherein the filter coefficients are coded using variable length code.

12. The non-transitory computer readable medium according to claim 9 , wherein the first index indicating a first CCALF for Cr component, the bitstream further comprises a second index indicating a second CCALF for Cb component, the first CCALF is a first 24-tap 9×9 filter, the second CCALF is a second 24-tap 9×9 filter, and the first index and the second index cause the decoder to filter the Cr component of the decoded video content using the first 24-tap 9×9 filter, and filter the Cb component of the decoded video content using the second 24-tap 9×9 filter.

13. The non-transitory computer readable medium according to claim 12 , wherein the bitstream further comprises a coded syntax element, the coded syntax element comprising filter coefficients of the first 24-tap 9×9 filter and filter coefficients of the second 24-tap 9×9 filter.

14. The non-transitory computer readable medium according to claim 13 , wherein in the bitstream, the filter coefficients of the first 24-tap 9×9 filter and the filter coefficients of the second 24-tap 9×9 filter are coded using variable length code.