Most probable mode list generation scheme

1 . A method of encoding a video bitstream in an intra sub-partition (ISP) mode using at least one processor, the method comprising:

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 adjacent to the current block and a plurality of non-adjacent reference lines;

signaling an intra sub partition mode (ISP) index indicating whether to divide luma intra-predicted blocks vertically or horizontally into sub-partitions based on block size dimensions;

determining a plurality of candidate intra prediction modes, the plurality of candidate intra prediction modes including a DC mode;

generating a most probable mode (MPM) list using the plurality of candidate intra prediction modes based on a reference line corresponding to the reference line index, wherein the MPM list includes all of the plurality of candidate intra prediction modes except for the DC mode when the reference line is the adjacent reference line; and

encoding the current block based on at least on the generated MPM list.

2 . The method of claim 1 , wherein the dividing of the luma intra-predicted blocks is processed in a reverse order based on the ISP mode and sub-partitions.

3 . The method of claim 1 , wherein the reference line index is signaled before one or more ISP syntax elements indicating whether the ISP mode is enabled.

4 . The method of claim 1 , wherein a planar mode is 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 1 , wherein an intra prediction mode of the MPM list is a planar 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 method for decoding a video bitstream in an intra-sub-partition (ISP) mode, the method comprising:

receiving a bitstream comprising 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 adjacent to the current block and a plurality of non-adjacent reference lines, and an intra sub partition mode (ISP) index indicating whether to divide luma intra-predicted blocks vertically or horizontally into sub-partitions based on block size dimensions;

determining a plurality of candidate intra prediction modes, the plurality of candidate intra prediction modes including a DC mode;

generating a most probable mode (MPM) list using the plurality of candidate intra prediction modes based on a reference line corresponding to the reference line index, wherein the MPM list includes all of the plurality of candidate intra prediction modes except for the DC mode when the reference line is the adjacent reference line; and

decoding the current block based on at least on the generated MPM list.

12 . The method of claim 11 , wherein the dividing of the luma intra-predicted blocks is processed in a reverse order based on the ISP mode and sub-partitions.

13 . The method of claim 11 , wherein an intra prediction mode of the MPM list is a planar mode.

14 . The method of claim 11 , wherein a planar mode is 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 method 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 method of claim 11 , wherein the reference line index is signaled before one or more ISP syntax elements indicating whether the ISP mode is enabled.

17 . The method 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 method 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 method 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 to generate a video bitstream in an intra sub-partition (ISP) mode, the video bitstream generated by a video encoding method comprising:

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 adjacent to the current block and a plurality of non-adjacent reference lines; signal an intra sub partition mode (ISP) index indicating whether to divide luma intra-predicted blocks vertically or horizontally into sub-partitions based on block size dimensions;

determining a plurality of candidate intra prediction modes, the plurality of candidate intra prediction modes including a DC mode;

generating a most probable mode (MPM) list using the plurality of candidate intra prediction modes based on a reference line corresponding to the reference line index, wherein the MPM list includes all of the plurality of candidate intra prediction modes except for the DC mode when the reference line is the adjacent reference line; and

encoding the current block based on at least on the generated MPM list.