Signaling of adaptive picture size in video bitstream

1. A method of decoding a coded picture of a coded video sequence, the method being performed by at least one processor and the method comprising:

decoding, from a parameter set, a plurality of candidate decoded resolutions;

selecting, through an index coded in a transient header structure applicable to a group of samples, a candidate decoded resolution among the plurality of candidate decoded resolutions;

resampling a sample of the group of samples based on an output resolution and the selected candidate decoded resolution; and

enabling prediction using the resampled sample based on meta-information obtained during decoding of previous parts of the coded picture or coded video sequence and previously reconstructed and loop-filtered sample values.

2. The method of claim 1 , wherein the transient header structure is any one or any combination of a picture header, a tile group header, a tile header, a slice header, and a Group of Blocks header.

3. The method of claim 2 , wherein the index is coded in an Exp-Golomb code.

4. The method of claim 2 , wherein the transient header structure is the tile group header and the tile group header comprises a resampling factor.

5. The method of claim 2 , wherein the transient header structure is the tile group header and the tile group header comprises adaptive resolution change (ARC) reference information.

6. The method of claim 5 , wherein the ARC reference information refers to a subset of ARC information available in a parameter set.

7. The method of claim 1 , wherein a number of the candidate decoded resolutions is coded in an Exp-Golomb code coded syntax element preceding the plurality of candidate decoded resolutions.

8. An apparatus for decoding a coded picture of a coded video sequence, the apparatus comprising:

at least one memory configured to store computer program code; and

at least one processor configured to access the at least one memory and operate according to the computer program code, the computer program code comprising:

decoding code configured to cause the at least one processor to decode, from a parameter set, a plurality of candidate decoded resolutions;

selecting code configured to cause the at least one processor to select, through an index coded in a transient header structure applicable to a group of samples, a candidate decoded resolution among the plurality of candidate decoded resolutions;

resampling code configured to cause the at least one processor to resample a sample of the group of samples based on an output resolution and the selected candidate decoded resolution; and

enabling code configured to cause the at least one processor to enable prediction using the resampled sample based on meta-information obtained during decoding of previous parts of the coded picture or coded video sequence and previously reconstructed and loop-filtered sample values.

9. The apparatus of claim 8 , wherein the transient header structure is any one or any combination of a picture header, a tile group header, a tile header, a slice header, and a Group of Blocks header.

10. The apparatus of claim 9 , wherein the index is coded in an Exp-Golomb code.

11. The apparatus of claim 9 , wherein the transient header structure is the tile group header and the tile group header comprises a resampling factor.

12. The apparatus of claim 9 , wherein the transient header structure is the tile group header and the tile group header comprises adaptive resolution change (ARC) reference information.

13. The apparatus of claim 12 , wherein the ARC reference information refers to a subset of ARC information available in a parameter set.

14. The apparatus of claim 8 , wherein a number of the candidate decoded resolutions is coded in an Exp-Golomb code coded syntax element preceding the plurality of candidate decoded resolutions.

15. A non-transitory computer-readable storage medium storing a program for decoding a coded picture of a coded video sequence, the program comprising instructions that cause a processor to:

decode, from a parameter set, a plurality of candidate decoded resolutions;

select, through an index coded in a transient header structure applicable to a group of samples, a candidate decoded resolution among the plurality of candidate decoded resolutions;

resample a sample of the group of samples based on an output resolution and the selected candidate decoded resolution; and

enable prediction using the resampled sample based on meta-information obtained during decoding of previous parts of the coded picture or coded video sequence and previously reconstructed and loop-filtered sample values.

16. The non-transitory computer-readable storage medium of claim 15 , wherein the transient header structure is any one or any combination of a picture header, a tile group header, a tile header, a slice header, and a Group of Blocks header.

17. The non-transitory computer-readable storage medium of claim 16 , wherein the index is coded in an Exp-Golomb code.

18. The non-transitory computer-readable storage medium of claim 16 , wherein the transient header structure is the tile group header and the tile group header comprises a resampling factor.

19. The non-transitory computer-readable storage medium of claim 16 , wherein the transient header structure is the tile group header and the tile group header comprises adaptive resolution change (ARC) reference information.

20. The non-transitory computer-readable storage medium of claim 15 , wherein a number of the candidate decoded resolutions is coded in an Exp-Golomb code coded syntax element preceding the plurality of candidate decoded resolutions.