On propagating intra prediction mode information of IBC block by using block vector
According to an aspect of the disclosure, a method of video decoding performed in a video decoder is provided. In the method, coded information of a current block in a current picture of a video is received from a coded video bitstream. The coded information indicates that the current block is an intra block copy (IBC) block. An intra prediction mode is derived for a subblock of the current block based on a reference subblock in a reference block. The reference subblock corresponds to the subblock of the current block, and the reference block is referenced by a block vector of the IBC block. The intra prediction mode for the subblock of the current block is further stored. A neighboring block of the current block is determined as an IBC block. A most probable mode (MPM) list is constructed for the neighboring block using the stored intra prediction mode.
1. A method of video decoding performed in a video decoder, the method comprising:
receiving coded information of a current block in a current picture of a video from a coded video bitstream, the coded information indicating that the current block is an intra block copy (IBC) block;
deriving an intra prediction mode for a subblock of the current block as an intra mode of a pixel positioned at a center location of a reference subblock in a reference block, the reference subblock corresponding to the subblock of the current block such that the reference subblock is positioned at a same relative position in the reference block as the subblock in the current block, the reference block being referenced by a block vector of the IBC block, the center location being one of (i) a second row and a second column of the reference subblock, (ii) the second row and a third column of the reference subblock, (iii) a third row and the second column of the reference subblock, and (iv) the third row and the third column of the reference subblock;
storing the intra prediction mode for the subblock of the current block;
determining that a neighboring block of the current block is an IBC block; and
constructing a most probable mode (MPM) list for the neighboring block using the stored intra prediction mode for the subblock of the current block.
2. The method of claim 1 , wherein
the center location is at the second row and the second column of the reference subblock.
3. The method of claim 1 , wherein
the center location is at the second row and the third column of the reference subblock.
4. The method of claim 1 , wherein
the center location is at the third row and the second column of the reference subblock.
5. The method of claim 1 , wherein
the center location is at the third row and the third column of the reference subblock.
6. The method of claim 1 , wherein:
the current block is partitioned into a first partition and a second partition based on a geometric partition mode (GPM), the first partition being predicted by IBC and the second partition being predicted by intra prediction, and
the subblock is positioned in the first partition that is predicted by the IBC.
7. The method of claim 1 , wherein the subblock of the current block is a 4 by 4 pixel unit.
8. The method of claim 1 , further comprising:
determining the intra prediction mode for the subblock as a candidate prediction mode in the MPM list for the neighboring block of the current block, the neighboring block being predicted by IBC.
9. A method of video encoding performed in a video encoder, the method comprising:
determining an intra prediction mode for a subblock of a current block in a current picture as an intra mode of a pixel positioned at a center location of a reference subblock in a reference block, the reference subblock corresponding to the subblock of the current block such that the reference subblock is positioned at a same relative position in the reference block as the subblock in the current block, the reference block being referenced by a block vector of an intra block copy (IBC) block, the center location being one of (i) a second row and a second column of the reference subblock, (ii) the second row and a third column of the reference subblock, (iii) a third row and the second column of the reference subblock, and (iv) the third row and the third column of the reference subblock;
determining a neighboring block of the current block is an IBC block;
constructing a most probable mode (MPM) list for the neighboring block using the intra prediction mode for the subblock of the current block; and
encoding the subblock of the current block based on the MPM list.
10. The method of claim 9 , wherein the center location is at the second row and the second column of the reference subblock.
11. The method of claim 9 , wherein the center location is at the second row and the third column of the reference subblock.
12. The method of claim 9 , wherein the center location is at the third row and the second column of the reference subblock.
13. The method of claim 9 , wherein the center location is at the third row and the third column of the reference subblock.
14. The method of claim 9 , further comprising:
partitioning the current block into a first partition and a second partition based on a geometric partition mode (GPM), the first partition being predicted by the IBC and the second partition being predicted by intra prediction,
wherein the subblock is positioned in the first partition that is predicted by the IBC.
15. The method of claim 9 , wherein the subblock of the current block is a 4 by 4 pixel unit.
16. The method of claim 9 , further comprises:
indicating the intra prediction mode for the subblock as a candidate prediction mode in the MPM list for the neighboring block of the current block, the neighboring block being predicted by the IBC.
17. 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 coded information of a current block in a current picture, the coded information indicating that the current block is an intra block copy (IBC) block; and
the format rule specifies that
an intra prediction mode for a subblock of the current block is derived as an intra mode of a pixel positioned at a center location of a reference subblock in a reference block,
the reference subblock corresponds to the subblock of the current block such that the reference subblock is positioned at a same relative position in the reference block as the subblock in the current block,
the reference block is referenced by a block vector of the IBC block,
the center location is one of (i) a second row and a second column of the reference subblock, (ii) the second row and a third column of the reference subblock, (iii) a third row and the second column of the reference subblock, and (iv) the third row and the third column of the reference subblock,
a neighboring block of the current block is determined as an IBC block, and
a most probable mode (MPM) list for the neighboring block is constructed using the intra prediction mode for the subblock of the current block.
18. The method of claim 17 , wherein:
the current block is partitioned into a first partition and a second partition based on a geometric partition mode (GPM), the first partition being predicted by IBC and the second partition being predicted by intra prediction, and
the subblock is positioned in the first partition that is predicted by the IBC.
19. The method of claim 17 , wherein the subblock of the current block is a 4 by 4 pixel unit.
20. The method of claim 17 , wherein the format rule specifies that:
the intra prediction mode for the subblock is determined as a candidate prediction mode in the MPM list for the neighboring block of the current block, the neighboring block being predicted by IBC.