Simplified 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:

generating a first most probable mode (MPM) list corresponding to a zero reference line of the current block, wherein the first MPM list comprises a plurality of angular intra prediction modes;

generating a second MPM list corresponding to one or more non-zero reference lines of the current block, wherein the second MPM list comprises the plurality of angular intra prediction modes;

signaling a reference line index indicating a reference line used to encode the current block from among the zero reference line and the one or more non-zero reference lines; and

signaling an intra mode index indicating the intra prediction mode within the first MPM list or the second MPM list,

wherein based on the reference line index indicating the reference line is the zero reference line, based on a respective intra prediction mode of a first neighboring block of the current block being a non-angular mode, and based on a respective intra prediction mode of a second neighboring block of the current block being an angular mode, a first intra prediction mode of the first MPM list is the non-angular mode, and a second intra prediction mode of the first MPM list is the angular mode.

2. The method of claim 1 , wherein the first MPM list further comprises one or more non-angular intra prediction modes, and

wherein the second MPM list does not include the one or more non-angular intra prediction modes.

3. The method of claim 2 , wherein the one or more non-angular intra prediction modes comprise at least one from among a planar mode and a DC mode.

4. The method of claim 1 , wherein the first MPM list includes a first plurality of indexes corresponding to the plurality of angular intra prediction modes,

wherein the second MPM list includes a second plurality of indexes corresponding to the plurality of angular intra prediction modes, and

wherein the first plurality of indexes is same as the second plurality of indexes.

5. The method of claim 4 , wherein the plurality of angular intra prediction modes includes a first angular intra prediction mode and a second angular intra prediction mode,

wherein the first angular intra prediction mode corresponds to a first index of the first plurality of indexes,

wherein the second angular intra prediction mode corresponds to a second index of the first plurality of indexes,

wherein the first angular intra prediction mode corresponds to a first index of the second plurality of indexes,

wherein the second angular intra prediction mode corresponds to a second index of the second plurality of indexes,

wherein the first index of the first plurality of indexes is same as the first index of the second plurality of indexes, and

wherein the second index of the first plurality of indexes is same as the second index of the second plurality of indexes.

6. The method of claim 1 , wherein based on the respective intra prediction mode of the first neighboring block of the current block being a DC mode, and based on the reference line index indicating the reference line is the zero reference line, the first intra prediction mode of the first MPM list is the DC mode.

7. The method of claim 1 , wherein based on the respective intra prediction mode of the first neighboring block of the current block being a planar mode, and based on the reference line index indicating the reference line is the zero reference line, the first intra prediction mode of the first MPM list is the planar mode.

8. The method of claim 1 , wherein based on the reference line index indicating the reference line is the zero reference line, the first intra prediction mode of the first MPM list is a planar mode, the second intra prediction mode of the first MPM list is the angular mode, and a third intra prediction mode of the first MPM list is a DC mode.

9. The method of claim 1 , wherein based on the reference line index indicating the reference line is the zero reference line, and based on the respective intra prediction mode of the first neighboring block of the current block being the non-angular mode, and based on the respective intra prediction mode of the second neighboring block of the current block being the angular mode, a position of at least one from among a planar mode and a DC mode in the first MPM list with respect to the angular mode is determined based on a mode number of the angular mode.

10. The method of claim 9 , wherein based on the angular mode being one of a horizontal mode and a vertical mode, the first intra prediction mode of the first MPM list is the angular mode, and the second intra prediction mode of the first MPM list is the at least one from among the planar mode and the DC mode, and

wherein based on the angular mode being a mode other than the horizontal mode and the vertical mode, the first intra prediction mode of the first MPM list is the at least one from among the planar mode and the DC mode, and the second intra prediction mode of the first MPM list is the angular mode.

11. The method of claim 9 , wherein based on the angular mode being one of a horizontal mode and a vertical mode, the first intra prediction mode of the first MPM list is the angular mode, and the second intra prediction mode of the first MPM list is the at least one from among the planar mode and the DC mode, and

wherein based on the angular mode being a mode other than the horizontal mode and the vertical mode, the first intra prediction mode of the first MPM list is a left neighboring mode of a left neighboring block of the current block, and the second intra prediction mode of the first MPM list is an above neighboring mode of an above neighboring block of the current block.

12. The method of claim 9 , wherein based on the angular mode being a mode which does not generate prediction samples at fractional position using interpolation, the first intra prediction mode of the first MPM list is the angular mode, and the second intra prediction mode of the first MPM list is the at least one from among the planar mode and the DC mode, and

wherein based on the angular mode being a mode which does generate the prediction samples at the fractional position using the interpolation, the first intra prediction mode of the first MPM list is the at least one from among the planar mode and the DC mode, and the second intra prediction mode of the first MPM list is the angular mode.

13. 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:

first generating code configured to cause the at least one processor to generate a first most probable mode (MPM) list corresponding to a zero reference line of the current block, wherein the first MPM list comprises a plurality of angular intra prediction modes;

second generating code configured to cause the at least one processor to generate a second MPM list corresponding to one or more non-zero reference lines of the current block, wherein the second MPM list comprises the plurality of angular 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 the zero reference line and the one or more non-zero 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 within the first MPM list or the second MPM list,

wherein based on the reference line index indicating the reference line is the zero reference line, based on a respective intra prediction mode of a first neighboring block of the current block being a non-angular mode, and based on a respective intra prediction mode of a second neighboring block of the current block being an angular mode, a first intra prediction mode of the first MPM list is the non-angular mode, and a second intra prediction mode of the first MPM list is the angular mode.

14. The device of claim 13 , wherein the first MPM list further comprises one or more non-angular intra prediction modes, and

wherein the second MPM list does not include the one or more non-angular intra prediction modes.

15. The device of claim 13 , wherein the first MPM list includes a first plurality of indexes corresponding to the plurality of angular intra prediction modes,

wherein the second MPM list includes a second plurality of indexes corresponding to the plurality of angular intra prediction modes, and

wherein the first plurality of indexes is same as the second plurality of indexes.

16. The device of claim 15 , wherein the plurality of angular intra prediction modes includes a first angular intra prediction mode and a second angular intra prediction mode,

wherein the first angular intra prediction mode corresponds to a first index of the first plurality of indexes,

wherein the second angular intra prediction mode corresponds to a second index of the first plurality of indexes,

wherein the first angular intra prediction mode corresponds to a first index of the second plurality of indexes,

wherein the second angular intra prediction mode corresponds to a second index of the second plurality of indexes,

wherein the first index of the first plurality of indexes is same as the first index of the second plurality of indexes, and

wherein the second index of the first plurality of indexes is same as the second index of the second plurality of indexes.

17. 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:

generate a first most probable mode (MPM) list corresponding to a zero reference line of the current block, wherein the first MPM list comprises a plurality of angular intra prediction modes;

generate a second MPM list corresponding to one or more non-zero reference lines of the current block, wherein the second MPM list comprises the plurality of angular intra prediction modes;

signal a reference line index indicating a reference line used to encode the current block from among the zero reference line and the one or more non-zero reference lines; and

signal an intra mode index indicating the intra prediction mode within the first MPM list or the second MPM list,

wherein based on the reference line index indicating the reference line is the zero reference line, based on a respective intra prediction mode of a first neighboring block of the current block being a non-angular mode, and based on a respective intra prediction mode of a second neighboring block of the current block being an angular mode, a first intra prediction mode of the first MPM list is the non-angular mode, and a second intra prediction mode of the first MPM list is the angular mode.