Method and apparatus for video coding
Aspects of the disclosure provide methods and an apparatus for video decoding. In some embodiments, the apparatus for video decoding includes processing circuitry. The processing circuitry decodes at least one syntax element from a coded video bitstream. The at least one syntax element is indicative of a block size of a non-square block under reconstruction that has a rectangular shape. The block size includes a first size in a first dimension and a second size in a second dimension. The first size is different from the second size. The processing circuitry predicts a sample of the non-square block based on a first set of intra prediction directions for the non-square block. The first set of intra prediction directions does not include at least one of a second set of intra prediction directions for a square block.
1. A method for video decoding in a decoder, comprising:
decoding at least one syntax element of a block to be reconstructed from a coded video bitstream, the at least one syntax element indicative of the block being a non-square block that has a rectangular shape; and
predicting a sample of the non-square block based on a first set of intra prediction directions for the non-square block, the first set of intra prediction directions including a first subset of intra prediction directions in a second set of intra prediction directions for a square block and not including a second subset of intra prediction directions in the second set of intra prediction directions, wherein
the second subset of intra prediction directions that is not shared with the non-square block is outside a first angular subrange covered by the first subset of intra prediction directions that is shared with the non-square block, and
the second subset of intra prediction directions is at an end of an angular range of the second set of intra prediction directions for the square block.
2. The method of claim 1 , wherein one of the second subset of intra prediction directions corresponds to the end of the angular range covered by the second set of intra prediction directions.
3. The method of claim 1 , wherein
the first angular subrange is between a first end and a second end,
the second subset of intra prediction directions covers a second angular subrange between a third end and a fourth end, and
the angular range covered by the second set of intra prediction directions includes the first angular subrange and the second angular subrange and is between the first end and the fourth end.
4. The method of claim 2 , wherein intra prediction modes used for the first set of intra prediction directions do not include an intra prediction mode used for the one of the second subset of intra prediction directions.
5. The method of claim 2 , wherein one or more intra prediction directions in the first set of intra prediction directions are not included in the second set of intra prediction directions.
6. The method of claim 5 , wherein an intra prediction mode used for the one of the second subset of intra prediction directions is assigned to one of the one or more intra prediction directions in the first set of intra prediction directions.
7. The method of claim 5 , wherein in a combined angular range covered by the first set of intra prediction directions and the second subset of intra prediction directions, one of the one or more intra prediction directions in the first set of intra prediction directions corresponds to a first end of the combined angular range, and the one of the second subset of intra prediction directions corresponds to a second end of the combined angular range.
8. The method of claim 5 , wherein a number of the one or more intra prediction directions in the first set of intra prediction directions is equal to a number of the second subset of intra prediction directions.
9. The method of claim 5 , wherein the one or more intra prediction directions in the first set of intra prediction directions are opposite to one or more intra prediction directions in the second subset of intra prediction directions.
10. The method of claim 1 , wherein a number of intra prediction modes used for the second set of intra prediction directions for the square block is equal to a number of intra prediction modes used for the first set of intra prediction directions for the non-square block.
11. The method of claim 1 , wherein
the second set of intra prediction directions for the square block includes the first set of intra prediction directions for the non-square block, and
a number of intra prediction modes used for the first set of intra prediction directions is less than a number of intra prediction modes used for the second set of intra prediction directions.
12. The method of claim 1 , wherein
the at least one syntax element indicates a ratio of a width of the non-square block over a height of the non-square block; and
the second subset of intra prediction directions is based on the ratio of the width of the non-square block over the height of the non-square block.
13. An apparatus for video decoding, the apparatus comprising:
processing circuitry configured to:
decode at least one syntax element of a block to be reconstructed from a coded video bitstream, the at least one syntax element indicative of the block being a non-square block that has a rectangular shape; and
predict a sample of the non-square block based on a first set of intra prediction directions for the non-square block, the first set of intra prediction directions including a first subset of intra prediction directions in a second set of intra prediction directions for a square block and not including a second subset of intra prediction directions in the second set of intra prediction directions, wherein
the second subset of intra prediction directions that is not shared with the non-square block is outside a first angular subrange covered by the first subset of intra prediction directions that is shared with the non-square block, and
the second subset of intra prediction directions is at an end of an angular range of the second set of intra prediction directions for the square block.
14. The apparatus of claim 13 , wherein one of the second subset of intra prediction directions corresponds to the end of the angular range covered by the second set of intra prediction directions.
15. The apparatus of claim 14 , wherein intra prediction modes used for the first set of intra prediction directions do not include an intra prediction mode used for the one of the second subset of intra prediction directions.
16. The apparatus of claim 14 , wherein one or more intra prediction directions in the first set of intra prediction directions are not included in the second set of intra prediction directions.
17. The apparatus of claim 16 , wherein an intra prediction mode used for the one of the second subset of intra prediction directions is assigned to one of the one or more intra prediction directions in the first set of intra prediction directions.
18. The apparatus of claim 16 , wherein the one or more intra prediction directions in the first set of intra prediction directions are opposite to one or more intra prediction directions in the second subset of intra prediction directions.
19. The apparatus of claim 13 , wherein
the second set of intra prediction directions for the square block includes the first set of intra prediction directions for the non-square block, and
a number of intra prediction modes used for the first set of intra prediction directions is less than a number of intra prediction modes used for the second set of intra prediction directions.
20. The apparatus of claim 13 , wherein
the at least one syntax element indicates a ratio of a width of the non-square block over a height of the non-square block; and
the second subset of intra prediction directions is based on the ratio of the width of the non-square block over the height of the non-square block.