Intra prediction-based image coding method and apparatus using MPM list

1. A video decoding method performed by a decoding apparatus, the method comprising:

constructing a most probable mode (MPM) list by deriving MPM candidates for a current block based on a neighboring block adjacent to the current block, wherein the MPM candidates include at least one of a first MPM candidate derived from a left neighboring block and a second MPM candidate derived from an upper neighboring block, wherein the MPM list includes at least one of the first MPM candidate and the second MPM candidate;

deriving an intra prediction mode for the current block based on the MPM list;

generating predicted samples by performing prediction for the current block based on the intra prediction mode; and

generating a reconstructed picture for the current block based on the predicted samples,

wherein the step of deriving the intra prediction mode for the current block includes:

obtaining MPM flag information related to whether the intra prediction mode for the current block is included among the MPM candidates;

obtaining MPM index information for indicating the intra prediction mode for the current block among the MPM candidates, based on the MPM flag information being a value of 1, wherein the MPM flag information being the value of 1 is that the intra prediction mode for the current block is included among the MPM candidates;

obtaining remaining mode information for indicating the intra prediction mode for the current block among remaining intra prediction modes except for the MPM candidates, based on the MPM flag information being a value of 0, wherein the MPM flag information being the value of 0 is that the intra prediction mode for the current block is not included among the MPM candidates; and

deriving the intra prediction mode for the current block based on the MPM index information or the remaining mode information,

wherein the remaining mode information is obtained based on a binarization process,

wherein the step of obtaining the remaining mode information includes performing the binarization process on the remaining mode information based on predetermined binarization type information on the remaining mode information,

wherein the predetermined binarization type information on the remaining mode information is a truncated binary (TB) binarization type.

2. The video decoding method of claim 1 , wherein the MPM candidates are derived based on 67 intra prediction modes, including 2 non-directional intra prediction modes and 65 directional intra prediction modes, and

the remaining mode information represents, as a value of a syntax element, indication information for an intra prediction mode derived based on the remaining intra prediction modes except the number of MPM candidates among the 67 intra prediction modes.

3. The video decoding method of claim 2 , wherein the value of the syntax element representing the remaining mode information is a value derived using a variable number of bits from 1 bit to 5 bits based on the truncated binary (TB) binarization process.

4. The video decoding method of claim 2 , wherein when the value of the syntax element representing the remaining mode information is smaller than a specific value derived based on the number of remaining intra prediction modes, the value of the syntax element representing the remaining mode information is a value derived using a variable number of bits from 1 bit to 5 bits based on the truncated binary (TB) binarization process.

5. The video decoding method of claim 1 , wherein the left neighboring block is located on a most bottom side among neighboring blocks neighboring a left boundary of the current block and the upper neighboring block is located on a most right side among neighboring blocks neighboring an upper boundary of the current block.

6. A video encoding method performed by an encoding apparatus, the method comprising:

constructing a most probable mode (MPM) list by deriving MPM candidates for a current block based on a neighboring block adjacent to a current block, wherein the MPM candidates include at least one of a first MPM candidate derived from a left neighboring block and a second MPM candidate derived from an upper neighboring block, wherein the MPM list includes at least one of the first MPM candidate and the second MPM candidate;

determining an intra prediction mode for the current block;

generating prediction samples by performing a prediction for the current block based on the intra prediction mode; and

encoding image information including intra prediction mode information for the current block,

wherein the step of determining the intra prediction mode for the current block includes:

generating MPM flag information based on whether the intra prediction mode for the current block is included among the MPM candidates;

generating MPM index information for indicating the intra prediction mode for the current block among the MPM candidates, based on the MPM flag information being a value of 1, wherein the MPM flag information being the value of 1 is that the intra prediction mode for the current block is included among the MPM candidates;

generating remaining mode information for indicating the intra prediction mode for the current block among remaining intra prediction modes except the MPM candidates, based on the MPM flag information being a value of 0, wherein the MPM flag information being the value of 0 is that the intra prediction mode for the current block is not included among the MPM candidates,

wherein the MPM flag information and the remaining mode information are included and encoded in the intra prediction mode information, and

wherein the remaining mode information is encoded based on a binarization process,

wherein the step of generating the remaining mode information includes performing the binarization process on the remaining mode information based on predetermined binarization type information on the remaining mode information,

wherein the predetermined binarization type information on the remaining mode information is a truncated binary (TB) binarization type.

7. The video encoding method of claim 6 , wherein the MPM candidates are derived based on 67 intra prediction modes, including 2 non-directional intra prediction modes and 65 directional intra prediction modes, and

the remaining mode information represents, as a value of a syntax element, indication information for an intra prediction mode derived based on the remaining intra prediction modes except the number of MPM candidates among the 67 intra prediction modes.

8. The video encoding method of claim 7 , wherein the value of the syntax element representing the remaining mode information is a value derived using a variable number of bits from 1 bit to 5 bits based on the truncated binary (TB) binarization process.

9. The video encoding method of claim 7 , wherein when the value of the syntax element representing the remaining mode information is smaller than a specific value derived based on the number of remaining intra prediction modes, the value of the syntax element representing the remaining mode information is a value derived using a variable number of bits from 1 bit to 5 bits based on the truncated binary (TB) binarization process.

10. The video encoding method of claim 6 , wherein the left neighboring block is located on a most bottom side among neighboring blocks neighboring a left boundary of the current block and the upper neighboring block is located on a most right side among neighboring blocks neighboring an upper boundary of the current block.

11. A non-transitory computer-readable storage medium storing encoded information causing a decoding apparatus to perform a video decoding method, the method comprising:

constructing a most probable mode (MPM) list by deriving MPM candidates for a current block based on a neighboring block adjacent to the current block, wherein the MPM candidates include at least one of a first MPM candidate derived from a left neighboring block and a second MPM candidate derived from an upper neighboring block, wherein the MPM list includes at least one of the first MPM candidate and the second MPM candidate;

deriving an intra prediction mode for the current block based on the MPM list;

generating predicted samples by performing prediction for the current block based on the intra prediction mode; and

generating a reconstructed picture for the current block based on the predicted samples,

wherein the step of deriving the intra prediction mode for the current block includes:

obtaining MPM flag information related to whether the intra prediction mode for the current block is included among the MPM candidates;

obtaining MPM index information for indicating the intra prediction mode for the current block among the MPM candidates, based on the MPM flag information being a value of 1, wherein the MPM flag information being the value of 1 is that the intra prediction mode for the current block is included among the MPM candidates;

obtaining remaining mode information for indicating the intra prediction mode for the current block among remaining intra prediction modes except for the MPM candidates, based on the MPM flag information being a value of 0, wherein the MPM flag information being the value of 0 is that the intra prediction mode for the current block is not included among the MPM candidates; and

deriving the intra prediction mode for the current block based on the MPM index information or the remaining mode information,

wherein the remaining mode information is obtained based on a binarization process,

wherein the step of obtaining the remaining mode information includes performing the binarization process on the remaining mode information based on predetermined binarization type information on the remaining mode information,

wherein the predetermined binarization type information on the remaining mode information is a truncated binary (TB) binarization type.

12. The video decoding method of claim 1 , wherein the first MPM candidate is derived as an intra prediction mode of the left neighboring block, when the left neighboring block is available and an intra prediction is applied to the left neighboring block, and

wherein the first MPM candidate is derived as a planar intra prediction mode, when the left neighboring block is not available or an intra prediction is not applied to the left neighboring block.

13. The video decoding method of claim 1 , wherein the second MPM candidate is derived as an intra prediction mode of the upper neighboring block, when the upper neighboring block is available, an intra prediction is applied to the upper neighboring block, and the upper neighboring block is included in a current CTU, and

wherein the second MPM candidate is derived as a planar intra prediction mode, when the upper neighboring block is not available or an intra prediction is not applied to the upper neighboring block or the upper neighboring block is not included in a current CTU.