Flexible transform scheme for residual blocks
The various implementations described herein include methods and systems for coding video. In one aspect, a method of video decoding includes receiving video data including a first block and a syntax element, from a video bitstream, where the syntax element is signaled at a first processing unit level. The method further includes selecting a transform coding mode based on the syntax element and performing a transform process for the first block using the selected transform coding mode, where the transform process is performed on a transform block at a second processing unit level, and where the second processing unit level is not signaled (e.g., is inferred from coded information).
1. A method of video decoding performed at a computing system having memory and one or more processors, the method comprising:
receiving video data comprising a plurality of blocks, including a first block, and a syntax element, from a video bitstream, wherein the syntax element is signaled at a first processing unit level;
selecting a transform coding mode based on the syntax element;
performing a transform process for the first block using the selected transform coding mode, wherein the transform process is performed on a transform block at a second processing unit level, wherein the transform process comprises applying an inverse transform to a plurality of residue coefficients for the first block to generate a refined residue block corresponding to the first block, and wherein the second processing unit level is inferred; and
generating a residue block from the refined residue block by applying a short distance intra prediction to the refined residue block, wherein:
the residue block is generated by adding a short distance intra prediction block to the refined residue block,
the short distance intra prediction comprises a line-by-line prediction in which residues in a particular row or column are predicted using an adjacent preceding row or column, and
the residue block is used to reconstruct the first block.
2. The method of claim 1 , wherein a first transform kernel is applied to the residue block and a second transform kernel is applied to the refined residue block, the second transform kernel being different than the first transform kernel.
3. The method of claim 1 , wherein the short distance intra prediction comprises a bi-directional prediction in which residues in a third index line and a fourth index line of the residue block are predicted using a weighted average of residues in a first index line and a second index line of the residue block.
4. The method of claim 1 , wherein the first processing unit level and the second processing unit level are the same.
5. The method of claim 1 , wherein the first processing unit level and the second processing unit level are different.
6. The method of claim 1 , wherein the video bitstream further includes a second syntax element that indicates whether the first processing unit level is the same as the second processing unit level.
7. The method of claim 1 , wherein the transform process includes an identity transform applied in a first direction and a Hadamard transform applied in a second direction.
8. A computing system, comprising:
control circuitry;
memory; and
one or more sets of instructions stored in the memory and configured for execution by the control circuitry, the one or more sets of instructions comprising instructions for:
receiving video data comprising a plurality of blocks, including a first block, and a syntax element, from a video bitstream, wherein the syntax element is signaled at a first processing unit level;
selecting a transform coding mode based on the syntax element;
performing a transform process for the first block using the selected transform coding mode, wherein the transform process is performed on a transform block at a second processing unit level, wherein the transform process comprises applying an inverse transform to a plurality of residue coefficients for the first block to generate a refined residue block corresponding to the first block, and wherein the second processing unit level is inferred; and
generating a residue block from the refined residue block by applying a short distance intra prediction to the refined residue block, wherein:
the residue block is generated by adding a short distance intra prediction block to the refined residue block,
the short distance intra prediction comprises a line-by-line prediction in which residues in a particular row or column are predicted using an adjacent preceding row or column, and
the residue block is used to reconstruct the first block.
9. The computing system of claim 8 , wherein a first transform kernel is applied to the residue block and a second transform kernel is applied to the refined residue block, the second transform kernel being different than the first transform kernel.
10. A non-transitory computer-readable storage medium storing one or more sets of instructions configured for execution by a computing device having control circuitry and memory, the one or more sets of instructions comprising instructions for:
receiving video data comprising a plurality of blocks, including a first block, and a syntax element, from a video bitstream, wherein the syntax element is signaled at a first processing unit level;
selecting a transform coding mode based on the syntax element;
performing a transform process for the first block using the selected transform coding mode, wherein the transform process is performed on a transform block at a second processing unit level, wherein the transform process comprises applying an inverse transform to a plurality of residue coefficients for the first block to generate a refined residue block corresponding to the first block, and wherein the second processing unit level is inferred; and
generating a residue block from the refined residue block by applying a short distance intra prediction to the refined residue block, wherein:
the residue block is generated by adding a short distance intra prediction block to the refined residue block,
the short distance intra prediction comprises a line-by-line prediction in which residues in a particular row or column are predicted using an adjacent preceding row or column, and
the residue block is used to reconstruct the first block.
11. The non-transitory computer-readable storage medium of claim 10 , wherein a first transform kernel is applied to the residue block and a second transform kernel is applied to the refined residue block, the second transform kernel being different than the first transform kernel.