Method and device for intra prediction
A method for decoding an image according to the present invention comprises the steps of: receiving and decoding MPM index information for indicating an MPM candidate which is to be used as an intra prediction mode of a current block; generating an MPM candidate list containing a plurality of MPM candidates for the current block; determining the MPM candidate indicated by the decoded MPM index information as the intra prediction mode of the current block, among the plurality of the MPM candidates which constitute the MPM candidate list; and generating a prediction block corresponding to the current block by performing intra prediction for the current block based on the determined intra prediction mode.
1. A video decoding method, comprising:
receiving, by a decoding apparatus, index information related to a candidate mode of an intra prediction mode of a current block;
receiving, by the decoding apparatus, information related to a residual sample for the current block;
constructing, by the decoding apparatus, a candidate mode list including a plurality of candidate modes for the current block;
determining, by the decoding apparatus, the intra prediction mode of the current block based on a candidate mode specified by the index information from among the plurality of candidate modes constituting the candidate mode list;
deriving, by the decoding apparatus, a predicted sample in the current block based on the determined intra prediction mode;
deriving, by the decoding apparatus, the residual sample of the current block based on the information related to the residual sample; and
deriving, by the decoding apparatus, a reconstructed sample of the current block based on the predicted sample and the residual sample,
wherein the constructing the candidate mode list includes:
setting a first ordered candidate mode and a second ordered candidate mode, among the plurality of candidate modes of the candidate mode list, based on a first block adjacent to a left side of the current block and a second block adjacent to an upper side of the current block, and
wherein the first ordered candidate mode is set equal to a planar mode and the second ordered candidate mode is set equal to a DC mode based on a case that both the first block and the second block are not available.
2. The method of claim 1 , wherein a first intra mode is derived based on the first block and a second intra mode is derived based on the second block,
wherein the first ordered candidate mode and the second ordered candidate mode are derived based on the first intra mode and the second intra mode.
3. The method of claim 2 , wherein the second intra mode is set to be the DC mode based on a case that the second block is not available.
4. The method of claim 2 , wherein the constructing the candidate mode list includes determining that the first block is not available based on a case that the first block is located outside a current picture or a current slice and determining that the second block is not available based on a case that the second block is located outside of the current picture or the current slice.
5. The method of claim 2 , wherein the constructing the candidate mode list includes determining that the first block is not available based on a case that the first block is not a block coded with an intra mode and determining that the second block is not available based on a case that the second block is not a block coded with an intra mode.
6. The method of claim 2 , wherein the first intra mode is set to the first ordered candidate mode and the second intra mode is set to the second ordered candidate mode based on a case that the first intra mode is not equal to the second intra mode.
7. The method of claim 2 , wherein the planar mode is set to the first ordered candidate mode and the DC mode is set to the second ordered candidate mode based on a case that both the first intra mode and the second intra mode are the planar mode.
8. The method of claim 2 , wherein the planar mode is set to the first ordered candidate mode and the DC mode is set to the second ordered candidate mode based on a case that both the first intra mode and the second intra mode are the DC mode.
9. A video encoding method, comprising:
constructing, by an encoding apparatus, a candidate mode list including a plurality of candidate modes for a current block;
determining, by the encoding apparatus, an intra prediction mode of the current block based on the candidate mode list;
generating, by the encoding apparatus, index information related to a candidate mode of the intra prediction mode of the current block;
generating, by the encoding apparatus, information related to a residual sample for the current block; and
generating a bitstream including the index information and the information related to the residual sample,
wherein the constructing the candidate mode list includes:
setting a first ordered candidate mode and a second ordered candidate mode, among the plurality of candidate modes of the candidate mode list, based on a first block adjacent to a left side of the current block and a second block adjacent to an upper side of the current block, and
wherein the first ordered candidate mode is set equal to a planar mode and the second ordered candidate mode is set equal to a DC mode based on a case that both the first block and the second block are not available.
10. The method of claim 9 , wherein a first intra mode is derived based on the first block and a second intra mode is derived based on the second block,
wherein the first ordered candidate mode and the second ordered candidate mode are derived based on the first intra mode and the second intra mode.
11. The method of claim 10 , wherein the second intra mode is set to be the DC mode based on a case that the second block is not available.
12. The method of claim 10 , wherein the constructing the candidate mode list includes determining that the first block is not available based on a case that the first block is located outside a current picture or a current slice and determining that the second block is not available based on a case that the second block is located outside of the current picture or the current slice.
13. The method of claim 10 , wherein the constructing the candidate mode list includes determining that the first block is not available based on a case that the first block is not a block coded with an intra mode and determining that the second block is not available based on a case that the second block is not a block coded with an intra mode.
14. The method of claim 10 , wherein the first intra mode is set to the first ordered candidate mode and the second intra mode is set to the second ordered candidate mode based on a case that the first intra mode is not equal to the second intra mode.
15. A non-transitory decoder-readable storage medium storing an encoded video information generated by an encoding process comprising: constructing, by an encoding apparatus, a candidate mode list including a plurality of candidate modes for a current block; determining, by the encoding apparatus, an intra prediction mode of the current block based on the candidate mode list; generating, by the encoding apparatus, index information related to a candidate mode of the intra prediction mode of the current block; generating, by the encoding apparatus, information related to a residual sample for the current block; and generating a bitstream including the index information and the information related to the residual sample, wherein the constructing the candidate mode list includes:
setting a first ordered candidate mode and a second ordered candidate mode, among the plurality of candidate modes of the candidate mode list, based on a first block adjacent to a left side of the current block and a second block adjacent to an upper side of the current block, and
wherein the first ordered candidate mode is set equal to a planar mode and the second ordered candidate mode is set equal to a DC mode based on a case that both the first block and the second block are not available.