Most probable mode list generation scheme

A method of video encoding using one or more processors, 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, the MPM list is generated based on the reference line used to encode the current block, all candidates in the MPM list are usable for the adjacent reference line, and a planar mode is firstly inserted into the MPM list with the reference line index being equal to 0;
• signaling a reference line index, an intra mode index, and intra sub-partition (ISP) index related syntax elements, the 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, the intra mode index indicating an intra prediction mode, and the ISP index related syntax elements are signaled after signaling of the reference line index as a default value which indicates the adjacent reference line is used;
• and
• encoding a current block of a video based on the reference line index, the intra mode index and the ISP index related syntax elements.

A non-transitory computer-readable storage medium storing instructions and a video bitstream that are generated by a video encoding method, the instructions, when executed by a computer, cause the computer to implement a video encoding 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, the MPM list is generated based on the reference line used to encode the current block, all candidates in the MPM list are usable for the adjacent reference line, and a planar mode is firstly inserted into the MPM list with the reference line index being equal to 0;
• signaling a reference line index, an intra mode index, and intra sub-partition (ISP) index related syntax elements, the 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, the intra mode index indicating an intra prediction mode, and the ISP index related syntax elements are signaled after signaling of the reference line index as a default value which indicates the adjacent reference line is used;
• encoding a current block of a video based on the reference line index, the intra mode index and the ISP index related syntax elements;
• and
• transmitting the video bitstream.