Method and apparatus for video filtering

1. A method for filtering in video decoding, comprising:

determining, by a processor, an offset value associated with a first filter shape configuration of a loop filter based on signals in a coded video bitstream that carries a video, a number of filter taps of the first filter shape configuration being smaller than five, the loop filter being based on a non linear mapping; and

applying, by the processor, the non linear mapping based loop filter on a sample that is to be filtered, using the offset value associated with the first filter shape configuration, the offset value associated with the first filter shape configuration corresponding to a predefined combination of quantized differences between the sample and reconstructed samples of the first filter shape configuration.

2. The method of claim 1 , wherein the loop filter includes at least one of a cross-component sample offset (CCSO) filter and a local sample offset (LSO) filter.

3. The method of claim 1 , wherein positions of the filter taps of the first filter shape configuration include a position of the sample.

4. The method of claim 1 , wherein positions of the filter taps of the first filter shape configuration exclude a position of the sample.

5. The method of claim 1 , further comprising:

selecting the first filter shape configuration from a group of filter shape configurations of the loop filter.

6. The method of claim 5 , wherein the filter shape configurations in the group respectively have the number of filter taps.

7. The method of claim 5 , wherein one or more filter shape configurations in the group have a different number of filter taps from the first filter shape configuration.

8. The method of claim 5 , further comprising:

decoding an index from the coded video bitstream that carries the video, the index being indicative of a selection of the first filter shape configuration from the group for the video loop filter.

9. The method of claim 8 , further comprising:

decoding the index from a syntax signaling of at least one of a block level, a coding tree unit (CTU) level, a super block (SB) level, a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, a tile header and a frame header.

10. The method of claim 1 , wherein

the differences are quantized into one of a number of possible quantization outputs, the number of possible quantization outputs being an integer in a range from 1 to 1024 inclusive.

11. The method of claim 10 , further comprising:

decoding an index from a syntax signaling of at least one of a block level, a coding tree unit (CTU) level, a super block (SB) level, a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, a tile header and a frame header, the index being indicative of the number of possible quantization outputs.

12. An apparatus for video decoding, comprising processing circuitry configured to:

determine an offset value associated with a first filter shape configuration of a loop filter based on signals in a coded video bitstream that carries a video, a number of filter taps of the first filter shape configuration being smaller than five, the loop filter being based on a non linear mapping; and

apply the non linear mapping based loop filter on a sample that is to be filtered using the offset value associated with the first filter shape configuration, the offset value associated with the first filter shape configuration corresponding to a predefined combination of quantized differences between the sample and reconstructed samples of the first filter shape configuration.

13. The apparatus of claim 12 , wherein the loop filter includes at least one of a cross-component sample offset (CCSO) filter and a local sample offset (LSO) filter.

14. The apparatus of claim 12 , wherein positions of the filter taps of the first filter shape configuration include a position of the sample.

15. The apparatus of claim 12 , wherein positions of the filter taps of the first filter shape configuration exclude a position of the sample.

16. The apparatus of claim 12 , wherein the processing circuitry is configured to:

select the first filter shape configuration from a group of filter shape configurations of the loop filter.

17. The apparatus of claim 16 , wherein the filter shape configurations in the group respectively have the number of filter taps.

18. The apparatus of claim 16 , wherein one or more filter shape configurations in the group have a different number of filter taps from the first filter shape configuration.

19. The apparatus of claim 16 , wherein the processing circuitry is configured to:

decode an index from the coded video bitstream that carries the video, the index being indicative of a selection of the first filter shape configuration from the group for the loop filter.

20. The apparatus of claim 19 , wherein the processing circuitry is configured to:

decode the index from a syntax signaling of at least one of a block level, a coding tree unit (CTU) level, a super block (SB) level, a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, a tile header and a frame header.

21. The apparatus of claim 12 , wherein

the differences are quantized into one of a number of possible quantization outputs, the number of possible quantization outputs being an integer in a range from 1 to 1024 inclusive.

22. The apparatus of claim 21 , wherein the processing circuitry is configured to:

decode an index from a syntax signaling of at least one of a block level, a coding tree unit (CTU) level, a super block (SB) level, a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, a tile header and a frame header, the index being indicative of the number of possible quantization outputs.