Method and apparatus for improved intra prediction
Flag information associated with the current block is obtained in coded information, which indicates whether the current block is intra predicted based at least in part on an intra mode derivation. In response to the flag information being true, a plurality of candidate intra modes is determined based on neighboring samples of the current block. A first intra mode of the current block is determined based on a first syntax element that is included in the coded information. The first syntax element indicates the first intra mode of the current block from a most probable mode (MPM) list and a MPM remainder. A second intra mode of the current block is determined based on the first intra mode and the plurality of candidate intra modes. The current block is reconstructed based on the first intra mode and the second intra mode.
1. A method of video decoding, the method comprising:
receiving coded information of a current block and neighboring samples of the current block from a coded video bitstream;
obtaining flag information associated with the current block in the coded information, the flag information indicating that the current block is intra predicted based at least in part on an intra mode derivation in which a plurality of candidate intra modes is derived based on the neighboring samples;
determining the plurality of candidate intra modes based on the neighboring samples;
determining a first intra mode of the current block based on a first syntax element that is included in the coded information when the flag information indicates that the current block is intra predicted based at least in part on the intra mode derivation, the first syntax element indicating the first intra mode of the current block from a most probable mode (MPM) list and a MPM remainder;
determining a second intra mode of the current block based on the plurality of candidate intra modes; and
reconstructing the current block based on a combination of the first intra mode and the second intra mode.
2. The method of claim 1 , further comprising:
when the flag information indicates that the current block is not intra predicted based on the intra mode derivation,
determining a third intra mode based on a second syntax element that is included in the coded information,
wherein the plurality of candidate intra modes is determined based on the neighboring samples when the flag information indicates that the current block is intra predicted based at least in part on the intra mode derivation.
3. The method of claim 1 , wherein the intra mode derivation includes decoder-side intra mode derivation (DIMD) in which the plurality of candidate intra modes is determined based on a histogram of gradients (HoGs) associated with the neighboring samples.
4. The method of claim 1 , wherein the intra mode derivation includes template based intra mode derivation (TIMD) in which the plurality of candidate intra modes is determined based on cost values of the neighboring samples.
5. A method of video encoding, the method comprising:
determining a current block is to be intra predicted based at least in part on an intra mode derivation in which a plurality of candidate intra modes is derived based on neighboring samples of the current block;
determining the plurality of candidate intra modes based on the neighboring samples;
determining a second intra mode of the current block based on the plurality of candidate intra modes;
encoding flag information in a bitstream, the flag information indicating that the current block is intra predicted based at least in part on the intra mode derivation;
encoding a first syntax element in the bitstream when the current block is intra predicted based at least in part on the intra mode derivation, the first syntax element indicating the first intra mode of the current block from a most probable mode (MPM) list and a MPM remainder; and
encoding the current block based on a combination of the first intra mode and the second intra mode.
6. The method of claim 5 , further comprising:
when the current block is not intra predicted based on the intra mode derivation, encoding a second syntax element that indicates a third intra mode in the video bitstream,
wherein the plurality of candidate intra modes is determined based on the neighboring samples when the current block is intra predicted based at least in part on the intra mode derivation.
7. The method of claim 5 , wherein the intra mode derivation includes decoder-side intra mode derivation (DIMD) in which the plurality of candidate intra modes is determined based on a histogram of gradients (HoGs) associated with the neighboring samples.
8. The method of claim 5 , wherein the intra mode derivation includes template based intra mode derivation (TIMD) in which the plurality of candidate intra modes is determined based on cost values of the neighboring samples.
9. A method of processing visual media data, the method comprising:
processing a bitstream that includes the visual media data according to a format rule, wherein
the bitstream includes flag information associated with a current block, the flag information indicating that the current block is intra predicted based at least in part on an intra mode derivation in which a plurality of candidate intra modes is derived based on neighboring samples of the current block; and
the format rule specifies that
the plurality of candidate intra modes is determined based on the neighboring samples,
a first intra mode of the current block indicated by a first syntax element that is included in the bitstream when the flag information indicates that the current block is intra predicted based at least in part on the intra mode derivation, the first syntax element indicating the first intra mode of the current block from a most probable mode (MPM) list and a MPM remainder,
a second intra mode of the current block is determined based on the plurality of candidate intra modes, and
the current block is processed based on a combination of the first intra mode and the second intra mode.
10. The method of claim 9 , wherein the format rule specifies that:
when the flag information indicates that the current block is not intra predicted based on the intra mode derivation, determining a third intra mode based on a second syntax element that is included in the bitstream; and
the plurality of candidate intra modes is determined based on the neighboring samples when the flag information indicates that the current block is intra predicted based at least in part on the intra mode derivation.
11. The method of claim 9 , wherein the intra mode derivation includes decoder-side intra mode derivation (DIMD) in which the plurality of candidate intra modes is determined based on a histogram of gradients (HoGs) associated with the neighboring samples.
12. The method of claim 9 , wherein the intra mode derivation includes template based intra mode derivation (TIMD) in which the plurality of candidate intra modes is determined based on cost values of the neighboring samples.