Method for encoding/decoding video signal and apparatus therefor
A video decoding method according to the present disclosure includes determining a reference sample line for a current block, deriving an intra prediction mode for the current block, and performing intra prediction of the current block based on the reference sample line and the intra prediction mode.
1. A video decoding method comprising:
determining a reference sample line for a current block;
deriving an intra prediction mode for the current block; and
performing intra prediction of the current block, based on the reference sample line and the intra prediction mode,
wherein the intra prediction mode is derived based on at least one of a default mode or a most probable mode (MPM) list,
determining whether to parse a flag indicating whether the intra prediction mode is identical with the default mode based on an index of the reference sample line, wherein determining whether to parse the flag comprises:
parsing the flag when the index of the reference sample line indicates an adjacent reference sample line, and
refraining from parsing the flag when the index of the reference sample line indicates a non-adjacent reference sample line,
wherein when the flag is parsed and the flag indicates that the intra prediction mode is identical with the default mode, the intra prediction of the current block is derived without reference to the MPM list, and
wherein when the flag is not parsed, the intra prediction mode is derived without reference to the flag.
2. The method of claim 1 , wherein deriving the intra prediction mode further includes parsing an MPM flag,
wherein when the MPM flag indicates that an MPM identical with the intra prediction mode is present in the MPM list, a number of intra prediction mode candidates which can be set as the intra prediction mode varies based on the index of the reference sample line.
3. The method of claim 1 , wherein when a first intra prediction mode for a top neighboring block adjacent to a top of the current block and a second intra prediction mode for a left neighboring block adjacent to a left of the current block are different from each other, and each of the first intra prediction mode and the second intra prediction mode is a directional intra prediction mode, the MPM list includes an intra prediction mode candidate derived by adding or subtracting 2 to or from a maximum value of the first intra prediction mode and the second intra prediction mode.
4. The method of claim 1 , wherein the default mode is a planar mode.
5. A video encoding method comprising:
determining a reference sample line for a current block;
deriving an intra prediction mode for the current block; and
performing intra prediction of the current block, based on the reference sample line and the intra prediction mode,
wherein the intra prediction mode is derived based on at least one of a default mode or a most probable mode (MPM) list,
determining whether to encode a flag indicating whether the intra prediction mode is identical with the default mode based on an index of the reference sample line, wherein determining whether to parse the flag comprises:
encoding the flag when the index of the reference sample line indicates an adjacent reference sample line, and
refraining from encoding the flag when the index of the reference sample line indicates a non-adjacent reference sample line,
wherein when the flag is encoded and indicates that the intra prediction mode is identical with the default mode, the intra prediction of the current block is to be derived without reference to the MPM list,
wherein when the flag is not encoded, the intra prediction mode is to be derived without reference to the flag.
6. The method of claim 5 , wherein deriving the intra prediction mode further includes encoding an MPM flag,
wherein when the MPM flag indicates that an MPM identical with the intra prediction mode is present in the MPM list, a number of intra prediction mode candidates which can be set as the intra prediction mode varies based on the index of the reference sample line.
7. The method of claim 5 , wherein when a first intra prediction mode for a top neighboring block adjacent to a top of the current block and a second intra prediction mode for a left neighboring block adjacent to a left of the current block are different from each other, and each of the first intra prediction mode and the second intra prediction mode is a directional intra prediction mode, the MPM list includes an intra prediction mode candidate derived by adding or subtracting 2 to or from a maximum value of the first intra prediction mode and the second intra prediction mode.
8. The method of claim 5 , wherein the default mode is a planar mode.
9. A video decoding device comprising an intra prediction unit configured to:
determine a reference sample line for a current block;
derive an intra prediction mode for the current block; and
perform intra prediction of the current block, based on the reference sample line and the intra prediction mode,
wherein the intra prediction mode is derived based on at least one of a default mode or a most probable mode (MPM) list,
determine whether to parse a flag indicating whether the intra prediction mode is identical with the default mode based on an index of the reference sample line, wherein determining whether to parse the flag comprises:
parsing the flag when the index of the reference sample line indicates an adjacent reference sample line, and
refraining from parsing the flag when the index of the reference sample line indicates a non-adjacent reference sample line,
wherein when the flag is parsed and the flag indicates that the intra prediction mode is identical with the default mode, the intra prediction of the current block is derived without reference to the MPM list, and
wherein when the flag is not parsed, the intra prediction mode is derived without reference to the flag.