Method and apparatus for offset in video filtering
Aspects of the disclosure provide methods and apparatuses for video encoding/decoding. In some examples, an apparatus for filtering in video decoding includes processing circuitry. For example, the processing circuitry determines first reconstructed sample values of reconstructed samples of a first color component within a filter support region of a to-be filtered sample of a second color component. The to-be filtered sample is at a center position of the filter support region. Based on a mapping that associates offset values with reconstructed sample values within the filter support region, a first offset value of the offset values in the mapping that is associated with the first reconstructed sample values is determined. The first offset value is applied on the second color component for the to-be filtered sample to determine a filtered sample value of the second color component for the to-be filtered sample.
1. A method for filtering in video decoding, comprising:
determining first reconstructed sample values of reconstructed samples of a first color component within a filter support region of a to-be filtered sample of a second color component, the to-be filtered sample being at a center position of the filter support region;
determining, based on a mapping of offset values with different combinations of reconstructed sample values within the filter support region, a first offset value of the offset values in the mapping with a combination of the first reconstructed sample values; and
applying the first offset value on the second color component for the to-be filtered sample to determine a filtered sample value of the second color component for the to-be filtered sample,
wherein the second color component is a different color component from the first color component.
2. The method of claim 1 , wherein the mapping is a non linear mapping defined in a form of a lookup table.
3. The method of claim 1 , wherein the filter support region of the to-be filtered sample includes sample positions in four directions to the to-be filtered sample.
4. The method of claim 1 , wherein the mapping associates the offset values with a complete domain of combinations for the reconstructed samples of the first color component within the filter support region.
5. The method of claim 1 , wherein the mapping associates the offset values with a subset of combinations for the reconstructed samples of the first color component within the filter support region.
6. The method of claim 1 , further comprising:
receiving the mapping that is included in at least one of a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, and a tile header of a coded video bitstream.
7. The method of claim 1 , wherein
the offset values of the mapping are derived based on cost measures; and
the mapping is included in at least one of a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, and a tile header of a coded video bitstream.
8. The method of claim 1 , further comprising:
adding the first offset value with the to-be filtered sample of the second color component to determine an intermediate filtered sample; and
clipping the intermediate filtered sample based on a maximum value and a minimum value to determine the filtered sample value of the second color component.
9. A method for filtering in video encoding, comprising:
determining first reconstructed sample values of reconstructed samples of a first color component within a filter support region of a to-be filtered sample of a second color component, the to-be filtered sample being at a center position of the filter support region;
determining, based on a mapping of offset values with different combinations of reconstructed sample values within the filter support region, a first offset value of the offset values in the mapping with a combination of the first reconstructed sample values; and
applying the first offset value on the second color component for the to-be filtered sample to determine a filtered sample value of the second color component for the to-be filtered sample,
wherein the second color component is a different color component from the first color component.
10. The method of claim 9 , wherein the mapping is a non linear mapping defined in a form of a lookup table.
11. The method of claim 9 , wherein the filter support region of the to-be filtered sample includes sample positions in four directions to the to-be filtered sample.
12. The method of claim 9 , wherein the mapping associates the offset values with a complete domain of combinations for the reconstructed samples of the first color component within the filter support region.
13. The method of claim 9 , wherein the mapping associates the offset values with a subset of combinations for the reconstructed samples of the first color component within the filter support region.
14. The method of claim 9 , further comprising:
encoding the mapping in at least one of a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, and a tile header of a coded video bitstream.
15. The method of claim 9 , further comprising:
deriving the offset values of the mapping based on cost measures; and
encoding the mapping in at least one of a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, and a tile header of a coded video bitstream.
16. The method of claim 9 , further comprising:
adding the first offset value with the to-be filtered sample of the second color component to determine an intermediate filtered sample; and
clipping the intermediate filtered sample based on a maximum value and a minimum value to determine the filtered sample value of the second color component.
17. A method of processing visual media data, the method comprising:
performing a conversion between a visual media file and a bitstream of visual media data according to a format rule, wherein
the bitstream includes coded information; and
the format rule specifies that:
first reconstructed sample values of reconstructed samples of a first color component within a filter support region of a to-be filtered sample of a second color component are determined, the second color component being a different color component from the first color component, the to-be filtered sample being at a center position of the filter support region,
based on a mapping of offset values with different combinations of reconstructed sample values within the filter support region, a first offset value of the offset values in the mapping with a combination of the first reconstructed sample values is determined, and
the first offset value is applied on the second color component for the to-be filtered sample to determine a filtered sample value of the second color component for the to-be filtered sample.
18. The method of claim 17 , wherein the mapping is a non linear mapping defined in a form of a lookup table.
19. The method of claim 17 , wherein the filter support region of the to-be filtered sample includes sample positions in four directions to the to-be filtered sample.
20. The method of claim 17 , wherein the mapping associates the offset values with a complete domain of combinations for the reconstructed samples of the first color component within the filter support region.