Most probable mode list generation scheme

1. A method of signaling an intra prediction mode used to encode a current block in an encoded video bitstream using at least one processor, the method comprising:

determining a plurality of candidate intra prediction modes;

generating a most probable mode (MPM) list using the plurality of candidate intra prediction modes;

signaling a reference line index indicating a reference line used to encode the current block from among a plurality of reference lines including an adjacent reference line and a plurality of non-adjacent reference lines; and

signaling an intra mode index indicating the intra prediction mode,

wherein the MPM list is generated based on the reference line used to encode the current block and whether an intra sub-partition (ISP) mode is enabled, wherein the ISP mode relates to dividing luma intra-predicted blocks vertically or horizontally into sub-partitions based on block size dimensions,

wherein a first intra prediction mode of the MPM list is a planar mode.

2. The method of claim 1 , wherein a DC mode is included in the plurality of candidate intra prediction modes,

wherein based on the reference line being the adjacent reference line and the ISP mode being disabled, the MPM list includes all of the plurality of candidate intra prediction modes, and

wherein based on the reference line being the adjacent reference line and the ISP mode being enabled, the MPM list includes all of the plurality of candidate intra prediction modes except for the DC mode.

3. The method of claim 1 , wherein a DC mode is included in the plurality of candidate intra prediction modes, and

wherein based on the reference line being the adjacent reference line and the ISP mode being enabled, the MPM list includes all of the plurality of candidate intra prediction modes except for the DC mode.

4. The method of claim 1 , wherein a DC mode and the planar mode are included in the plurality of candidate intra prediction modes, and

wherein based on the reference line being the one from among the plurality of non-adjacent reference lines, the MPM list includes all of the plurality of candidate intra prediction modes except for the DC mode and the planar mode.

5. The method of claim 1 , wherein the MPM list is a same MPM list based on the reference line being the adjacent reference line and the ISP mode being disabled, based on the reference line being the adjacent reference line and the ISP mode being enabled, and based on the reference line being the one from among the plurality of non-adjacent reference lines.

6. The method of claim 5 , wherein a second intra prediction mode of the MPM list is a DC mode.

7. The method of claim 1 , wherein based on the reference line index indicating that the reference line is the adjacent reference line, a first one or two bins of the intra mode index are context coded, wherein a context is determined based on whether the ISP mode is enabled.

8. The method of claim 1 , wherein based on the reference line index indicating that the reference line is the adjacent reference line, a first one or two bins of the intra mode index are context coded, wherein a context is determined based on a value of the reference line index.

9. The method of claim 1 , wherein based on the reference line index indicating that the reference line is the adjacent reference line, a first one or two bins of the intra mode index are context coded, wherein a context is determined based on whether the ISP mode is enabled and the reference line index.

10. The method of claim 1 , wherein based on the reference line index indicating that the reference line is the adjacent reference line, a first two bins of the intra mode index are context coded, wherein a context is determined based on the intra mode index and a reference line index indicating a reference line used to encode a neighboring block.

11. A device for signaling an intra prediction mode used to encode a current block in an encoded video bitstream, the device comprising:

at least one memory configured to store program code; and

at least one processor configured to read the program code and operate as instructed by the program code, the program code including:

determining code configured to cause the at least one processor to determine a plurality of candidate intra prediction modes;

generating code configured to cause the at least one processor to generate a most probable mode (MPM) list using the plurality of candidate intra prediction modes;

first signaling code configured to cause the at least one processor to signal a reference line index indicating a reference line used to encode the current block from among a plurality of reference lines including an adjacent reference line and a plurality of non-adjacent reference lines; and

second signaling code configured to cause the at least one processor to signal an intra mode index indicating the intra prediction mode,

wherein the MPM list is generated based on the reference line used to encode the current block and whether an intra sub-partition (ISP) mode is enabled, wherein the ISP mode relates to dividing luma intra-predicted blocks vertically or horizontally into sub-partitions based on block size dimensions,

wherein a first intra prediction mode of the MPM list is a planar mode.

12. The device of claim 11 , wherein based on the reference line being the adjacent reference line and the ISP mode being disabled, the MPM list includes all of the plurality of candidate intra prediction modes.

13. The device of claim 11 , wherein a DC mode is included in the plurality of candidate intra prediction modes, and

wherein based on the reference line being the adjacent reference line and the ISP mode being enabled, the MPM list includes all of the plurality of candidate intra prediction modes except for the DC mode.

14. The device of claim 11 , wherein a DC mode and the planar mode are included in the plurality of candidate intra prediction modes, and

wherein based on the reference line being the one from among the plurality of non-adjacent reference lines, the MPM list includes all of the plurality of candidate intra prediction modes except for the DC mode and the planar mode.

15. The device of claim 11 , wherein the MPM list is a same MPM list based on the reference line being the adjacent reference line and the ISP mode being disabled, based on the reference line being the adjacent reference line and the ISP mode being enabled, and based on the reference line being the one from among the plurality of non-adjacent reference lines.

16. The device of claim 15 , wherein a second intra prediction mode of the MPM list is a DC mode.

17. The device of claim 11 , wherein based on the reference line index indicating that the reference line is the adjacent reference line, a first one or two bins of the intra mode index are context coded, wherein a context is determined based on whether the ISP mode is enabled.

18. The device of claim 11 , wherein based on the reference line index indicating that the reference line is the adjacent reference line, a first one or two bins of the intra mode index are context coded, wherein a context is determined based on a value of the reference line index.

19. The device of claim 11 , wherein based on the reference line index indicating that the reference line is the adjacent reference line, a first one or two bins of the intra mode index are context coded, wherein a context is determined based on whether the ISP mode is enabled and the reference line index.

20. A non-transitory computer-readable medium storing instructions, the instructions comprising: one or more instructions that, when executed by one or more processors of a device for signaling an intra prediction mode used to encode a current block in an encoded video bitstream, cause the one or more processors to:

determine a plurality of candidate intra prediction modes;

generate a most probable mode (MPM) list using the plurality of candidate intra prediction modes;

signal a reference line index indicating a reference line used to encode the current block from among a plurality of reference lines including an adjacent reference line and a plurality of non-adjacent reference lines; and

signal an intra mode index indicating the intra prediction mode,

wherein the MPM list is generated based on the reference line used to encode the current block and whether an intra sub-partition (ISP) mode is enabled, wherein the ISP mode relates to dividing luma intra-predicted blocks vertically or horizontally into sub-partitions based on block size dimensions,

wherein a first intra prediction mode of the MPM list is a planar mode.