Harmonization of raster scan and rectangular tile groups in video coding

1. A method implemented by an encoder, the method comprising:

partitioning a picture into a plurality of tiles;

including a number of the tiles into a tile group;

encoding a flag set to a first value when the tile group is a raster scan tile group and a second value when the tile group is a rectangular tile group, wherein the flag is encoded into a parameter set of a bitstream;

encoding in the bitstream an identifier of a first tile of the tile group to indicate the tiles included in the tile group;

encoding in the bitstream an identifier of a last tile of the tile group to indicate the tiles included in the tile group;

encoding the tiles into the bitstream based on the tile group; and

storing the bitstream for communication toward a decoder.

2. The method of claim 1 , wherein the flag is a rectangular tile group flag.

3. The method of claim 1 , wherein the parameter set into which the flag is encoded is a sequence parameter set.

4. The method of claim 1 , wherein the parameter set into which the flag is encoded is a picture parameter set.

5. The method of claim 1 , wherein the identifier of the first tile of the tile group and the identifier of the last tile of the tile group are encoded in a tile group header in the bitstream.

6. The method of claim 1 , wherein when the tile group is the raster scan tile group, tile inclusion in the tile group is determined by:

determining a number of tiles between the first tile of the tile group and the last tile of the tile group as the number of tiles in the tile group; and

determining the tile inclusion based on the number of tiles in the tile group.

7. The method of claim 1 , wherein when the tile group is the rectangular tile group, tile inclusion in the tile group is determined by:

determining a delta value between the first tile of the tile group and the last tile of the tile group;

determining a number of tile group rows based on the delta value and a number of tile columns in the picture;

determining a number of tile group columns based on the delta value and the number of tile columns in the picture; and

determining the tile inclusion based on the number of tile group rows and the number of tile group columns.

8. A method implemented by a decoder, the method comprising:

receiving a bitstream including a picture partitioned into a plurality of tiles, wherein a number of the tiles are included into a tile group;

obtaining a flag from a parameter set of the bitstream;

determining the tile group is a raster scan tile group when the flag is set to a first value;

determining the tile group is a rectangular tile group when the flag is set to a second value;

determining tile inclusion for the tile group based on whether the tile group is the raster scan tile group or rectangular tile group;

obtaining an identifier of a first tile of the tile group to determine the tiles included in the tile group;

obtaining an identifier of a last tile of the tile group to determine the tiles included in the tile group;

decoding the tiles to generate decoded tiles based on the tile group; and

generating a reconstructed video sequence for display based on the decoded tiles.

9. The method of claim 8 , wherein the flag is a rectangular tile group flag.

10. The method of claim 8 , wherein the parameter set including the flag is a sequence parameter set.

11. The method of claim 8 , wherein the parameter set including the flag is a picture parameter set.

12. The method of claim 8 , wherein the identifier of the first tile of the tile group and the identifier of the last tile of the tile group are obtained from a tile group header in the bitstream.

13. The method of claim 8 , wherein when the tile group is the raster scan tile group, the tile inclusion in the tile group is determined by:

determining a number of tiles between the first tile of the tile group and the last tile of the tile group as the number of tiles in the tile group; and

determining the tile inclusion based on the number of tiles in the tile group.

14. The method of claim 8 , wherein when the tile group is the rectangular tile group, the tile inclusion in the tile group is determined by:

determining a delta value between the first tile of the tile group and the last tile of the tile group;

determining a number of tile group rows based on the delta value and a number of tile columns in the picture;

determining a number of tile group columns based on the delta value and the number of tile columns in the picture; and

determining the tile inclusion based on the number of tile group rows and the number of tile group columns.

15. A method implemented by a decoder, the method comprising:

receiving a bitstream comprising a group of tiles in a picture and a parameter set containing a flag, wherein when the flag is set to a first value, the flag specifies a raster scan mode is in use for the group of tiles in the picture, and wherein when the flag is set to a second value, the flag specifies a rectangular mode is in use for the group of tiles in the picture, wherein a raster scan group of tiles contains tiles in consecutive raster scan order of the picture, and a rectangular group of tiles contains tiles collectively forming a rectangular region of the picture; and

decoding the group of tiles based on the flag.

16. The method of claim 15 , wherein the parameter set containing the flag is a picture parameter set.

17. The method of claim 15 , wherein an identifier of a first tile of the group of tiles indicates tiles included in the group of tiles.

18. A method implemented by a decoder, the method comprising:

receiving a bitstream comprising a group of tiles in a picture and a parameter set containing a flag, wherein when the flag is set to a first value, the flag specifies a raster scan mode is in use for the group of tiles in the picture, and wherein when the flag is set to a second value, the flag specifies a rectangular mode is in use for the group of tiles in the picture;

determining delta values specifying indices of a first tile of each group of tiles; and

decoding the group of tiles based on the flag and the delta values.