Method and apparatus for processing video content with ALF and CCALF

1. A computer-implemented method of decoding a bitstream to output one or more pictures for a video stream, the method comprising:

receiving a bitstream associated with video content, wherein the bitstream does not comprise adaptation parameter set (APS) network-abstraction-layer (NAL) unit;

decoding, using coded information of the bitstream, one or more pictures,

wherein the decoding comprises:

determining whether the APS NAL unit is present in the bitstream; and

in response to the determination that the APS NAL unit is not present in the bitstream, disabling both a cross component adaptive loop filter (CCALF) process and a chroma adaptive loop filter (ALF) process; and

performing a luma ALF process based on a slice-level flag associated with a predetermined set of filters,

wherein disabling the CCALF process further comprises:

decoding a first sequence-level flag indicating that the CCALF process is disabled for a video sequence associated with the sequence-level flag; and

decoding a second sequence-level flag indicating that luma mapping with chroma scaling (LMCS) is disabled for the video sequence,

wherein the decoding of the second sequence-level flag is immediately after the decoding of the first sequence-level flag.

2. The method according to claim 1 , wherein the determining of whether the APS NAL unit is present in the bitstream is based on a first signal in the bitstream.

3. The method according to claim 1 , further comprising:

receiving a second signal for controlling the chroma ALF process at a picture parameter set level, a sequence parameter set level, a picture header level, or a slice header level.

4. The method according to claim 3 , wherein

the second signal indicates whether the chroma ALF process is enabled in decoding of chroma components of pictures in a coded layer video sequence (CLVS) associated with the video content.

5. The method according to claim 3 , wherein

the second signal indicates whether the chroma ALF process is enabled in decoding of chroma components of pictures referring to a picture parameter set (PPS) associated with the video content.

6. A method of encoding a video sequence into a bitstream, the method comprising:

receiving a video sequence;

encoding one or more pictures of the video sequence; and

generating a bitstream,

wherein the encoding comprises:

encoding a first flag indicating whether adaption parameter set (APS) network-abstraction-layer (NAL) unit is present in the bitstream; and

in response to the first flag indicating that the APS NAL unit is not present in the bitstream, encoding a set of flags disabling both a cross component adaptive loop filter (CCALF) process and a chroma adaptive loop filter (ALF) process; and

encoding a slice-level flag associated with a predetermined set of filters, the predetermined set of filters being used for performing a luma ALF process,

wherein the set of flags comprises:

a first sequence-level flag indicating that the CCALF process is disabled for a video sequence associated with the first sequence-level flag; and

a second sequence-level flag indicating that luma mapping with chroma scaling (LMCS) is disabled for the video sequence,

wherein the first and second sequence-level flags are both encoded into the bitstream, and the second sequence-level flag is signaled immediately after the first sequence-level flag.

7. The method of claim 6 , further comprising:

in response to the first signal having a first value, encoding the set of flags disabling both the CCALF process and the ALF process.

8. The method of claim 6 , wherein the set of flags comprises a second flag, and the method further comprises:

setting a value of the second flag to disable the chroma ALF process at a picture parameter set level, a sequence parameter set level, a picture header level, or a slice header level.

9. The method of claim 8 , wherein

the second flag indicates whether the chroma ALF process is enabled for chroma components of pictures in a coded layer video sequence (CLVS) associated with the video content.

10. The method of claim 8 , wherein

the second flag indicates whether the chroma ALF process is enabled for chroma components of pictures referring to a picture parameter set (PPS) associated with the video content.

11. The method according to claim 2 , wherein the first signal is a flag, and the method further comprises:

in response to the flag having a value equal to 1, determining that the APS NAL unit is not present in the received bitstream.

12. The method according to claim 1 , wherein disabling the chroma ALF process further comprises:

receiving one or more slice-level flags indicating that the chroma ALF process is disabled for a video slice associated with the one or more slice-level flags.

13. The method according to claim 12 , wherein the first and second sequence-level flags are signaled in a sequence parameter set (SPS).

14. The method of claim 7 , wherein the first value is equal to 1.

15. The method of claim 6 , wherein the set of flags comprises:

one or more slice-level flags indicating that the chroma ALF process is disabled for a video slice associated with the one or more slice-level flags.

16. The method according to claim 15 , wherein the first sequence-level level flags are signaled in a sequence parameter set (SPS).

17. A non-transitory computer readable medium storing a bitstream associated with video content, wherein the bitstream comprises:

a flag indicating that adaption parameter set (APS) network-abstraction-layer (NAL) unit is not present in the bitstream;

a first sequence-level flag indicating that a cross component adaptive loop filter (CCALF) process is disabled;

a second sequence-level flag indicating that luma mapping with chroma scaling (LMCS) is disabled;

one or more slice-level flags indicating that a chroma adaptive loop filter (ALF) process is disabled;

a slice-level flag indicating that a luma ALF process is enabled; and

a slice-level flag indicating that a predetermined set of filters is used for the luma ALF process,

wherein second sequence-level flag is signaled immediately after the first sequence-level flag.

18. The non-transitory computer readable medium of claim 17 , wherein the bitstream further comprises:

a sequence parameter set (SPS), wherein the first and second sequence-level flags are signaled in the SPS.