Method and device for processing video signal for intra prediction

A method for encoding a video signal for intra prediction, the method comprising:

• determining whether multiple reference lines (MRL) are enabled for a current block;
• determining whether a top boundary of the current block is a boundary of a current coding tree unit (CTU);
• determining reference samples being used for the intra prediction based on whether the top boundary of the current block is the boundary of the current CTU and whether the MRL are enabled for the current block;
• generating reference sample line information of the current block, wherein the reference sample line information includes an index indicating reference sample line being used for the intra prediction;
• determining an intra prediction mode of the current block;
• generating intra prediction information based on the intra prediction mode;
• generating an intra sub-partition (ISP) flag representing whether the current block is partitioned into sub-partitions based on the reference sample line information;
• and
• generating prediction samples of the current block based on the intra prediction mode and the reference samples,
• wherein the intra prediction information includes a first flag, and
• wherein the first flag is coded with a first value based on the intra prediction mode corresponding to a predetermined first mode and coded with a second value based on the intra prediction mode corresponding to one of modes other than the first mode,
• wherein the predetermined first mode is a planar mode, and
• wherein, based on the intra prediction mode corresponding to one of modes other than the first mode, a most probable mode (MPM) index specifying one among a plurality of candidate modes is encoded.

A method of transmitting a bitstream comprising:

• determining whether multiple reference lines (MRL) are enabled for a current block;
• determining whether a top boundary of the current block is a boundary of a current coding tree unit (CTU);
• determining reference samples being used for the intra prediction based on whether the top boundary of the current block is the boundary of the current CTU and whether the MRL are enabled for the current block;
• generating reference sample line information of the current block, wherein the reference sample line information includes an index indicating reference sample line being used for the intra prediction;
• determining an intra prediction mode of the current block;
• generating intra prediction information based on the intra prediction mode;
• generating an intra sub-partition (ISP) flag representing whether the current block is partitioned into sub-partitions based on the reference sample line information;
• generating prediction samples of the current block based on the intra prediction mode and the reference samples;
• encoding the bitstream including the reference sample line information, the intra prediction information and the ISP flag;
• and
• transmitting the bitstream,
• wherein the intra prediction information includes a first flag, and
• wherein the first flag is coded with a first value based on the intra prediction mode corresponding to a predetermined first mode and coded with a second value based on the intra prediction mode corresponding to one of modes other than the first mode,
• wherein the predetermined first mode is a planar mode, and
• wherein, based on the intra prediction mode corresponding to on of modes other than the first mode, a most probable mode (MPM) index specifying one among a plurality of candidate modes is encoded and transmitted.