Signaling for reference picture resampling
A method of video processing includes determining, for a conversion between a current block of a video and a coded representation of the video, that a resolution of a current picture containing the current block and a reference picture used for the conversion are different, and performing the conversion based on the determining such that predicted values of a group of samples of the current block are generated using a horizontal or a vertical interpolation filter.
1. A method of processing video data, comprising:
determining, for a conversion between a current block of a current picture of a video and a bitstream of the video, usage of a wraparound clipping operation that is applied to a reference picture for determining a prediction block for the current block based on at least one syntax element;
performing the conversion based on the determining;
wherein the wraparound clipping operation is used to reselect samples in the reference picture in case that samples are outside the reference picture, and
wherein the at least one syntax element includes a first syntax element included in a picture parameter set (PPS), wherein the first syntax element indicates whether the wraparound clipping operation is enabled in a horizontal direction for the current block, and wherein a value of the first syntax element depends on a first size associated with a coding tree block of the current block and a second size associated with a width of the current picture comprising the current block.
2. The method of claim 1 , wherein the at least one syntax element includes a second syntax element included in a sequence parameter set (SPS), and the second syntax element indicates whether the wraparound clipping operation is enabled in the horizontal direction for the current block.
3. The method of claim 2 , wherein the value of the first syntax element depends on a value of the second syntax element.
4. The method of claim 3 , wherein the first syntax element indicates the wraparound clipping operation is disabled in case that the second syntax element indicates the wraparound clipping operation is disabled for the current block.
5. The method of claim 3 , wherein the first syntax element is conditionally included in the bitstream in case that the second syntax element indicates the wraparound clipping operation is enabled for the current block.
6. The method of claim 1 , wherein the first syntax element indicates that the wraparound clipping operation is disabled in case that the first size is greater than the second size.
7. The method of claim 1 , wherein the first size is equal to (CtbSizeY/MinCbSizeY+Offset1), where CtbSizeY indicates a height or a width of the coding tree block of the current block, MinCbSizeY indicates a minimum allowed size for coding blocks for the conversion, and Offset1 is an integer, and
wherein the second size is equal to (pic_width_in_luma_samples/MinCbSizeY— Offset2), where pic_width_in_luma_samples indicates a width of the current picture in luma samples indicated in the picture parameter set, and Offset2 is an integer.
8. The method of claim 7 , wherein Offset2=Offset1=1.
9. The method of claim 1 , wherein the value of the first syntax element being “1” indicates that the wraparound clipping operation is enabled in the horizontal direction, and the value of the first syntax element being “0” indicates that the wraparound clipping operation is disabled in the horizontal direction.
10. The method of claim 1 , wherein the conversion comprises encoding the current block into the bitstream.
11. The method of claim 1 , wherein the conversion comprises decoding the current block from the bitstream.
12. An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:
determine, for a conversion between a current block of a current picture of a video and a bitstream of the video, usage of a wraparound clipping operation that is applied to a reference picture for determining a prediction block for the current block based on at least one syntax element;
perform the conversion based on the determination;
wherein the wraparound clipping operation is used to reselect samples in the reference picture in case that samples are outside the reference picture, and
wherein the at least one syntax element includes a first syntax element included in a picture parameter set (PPS), wherein the first syntax element indicates whether the wraparound clipping operation is enabled in a horizontal direction for the current block, and wherein a value of the first syntax element depends on a first size associated with a coding tree block of the current block and a second size associated with a width of the current picture comprising the current block.
13. The apparatus of claim 12 , wherein the at least one syntax element includes a second syntax element included in a sequence parameter set (SPS), and the second syntax element indicates whether the wraparound clipping operation is enabled in the horizontal direction for the current block.
14. A non-transitory computer-readable storage medium storing instructions that cause a processor to:
determine, for a conversion between a current block of a current picture of a video and a bitstream of the video, usage of a wraparound clipping operation that is applied to a reference picture for determining a prediction block for the current block based on at least one syntax element;
perform the conversion based on the determination;
wherein the wraparound clipping operation is used to reselect samples in the reference picture in case that samples are outside the reference picture, and
wherein the at least one syntax element includes a first syntax element included in a picture parameter set (PPS), wherein the first syntax element indicates whether the wraparound clipping operation is enabled in a horizontal direction for the current block, and wherein a value of the first syntax element depends on a first size associated with a coding tree block of the current block and a second size associated with a width of the current picture comprising the current block.
15. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises:
determining, for a current block of a current picture of the video, usage of a wraparound clipping operation that is applied to a reference picture for determining a prediction block for the current block based on at least one syntax element;
generating the bitstream based on the determining;
wherein the wraparound clipping operation is used to reselect samples in the reference picture in case that samples are outside the reference picture, and
wherein the at least one syntax element includes a first syntax element included in a picture parameter set (PPS), wherein the first syntax element indicates whether the wraparound clipping operation is enabled in a horizontal direction for the current block, and wherein a value of the first syntax element depends on a first size associated with a coding tree block of the current block and a second size associated with a width of the current picture comprising the current block.
16. The apparatus of claim 13 , wherein the value of the first syntax element depends on a value of the second syntax element.
17. The apparatus of claim 16 , wherein the first syntax element indicates the wraparound clipping operation is disabled in case that the second syntax element indicates the wraparound clipping operation is disabled for the current block.
18. The apparatus of claim 17 , wherein the first syntax element is conditionally included in the bitstream in case that the second syntax element indicates the wraparound clipping operation is enabled for the current block.
19. The apparatus of claim 12 , wherein the first syntax element indicates that the wraparound clipping operation is disabled in case that the first size is greater than the second size.
20. The apparatus of claim 12 , wherein the first size is equal to (CtbSizeY/MinCbSizeY+Offset1), where CtbSizeY indicates a height or a width of the coding tree block of the current block, MinCbSizeY indicates a minimum allowed size for coding blocks for the conversion, and Offset1 is an integer, and
wherein the second size is equal to (pic_width_in_luma_samples/MinCbSizeY— Offset2), where pic_width_in_luma_samples indicates a width of the current picture in luma samples indicated in the picture parameter set, and Offset2 is an integer.
21. The apparatus of claim 20 , wherein Offset2=Offset1=1.