Image coding device and method based on filtering-related information signaling
According to embodiments of the present document, a zero-order exponential Golomb coding scheme(ue(v)) is used for a parsing procedure of an information/syntax element related to luma/chroma ALF filter coefficient absolute values, so that operational overhead and complexity can be reduced. In addition, since the range of values of the information related to the luma/chroma ALF filter coefficient absolute values is fixed, coding that uses ue(v) can be efficiently performed.
1. An image decoding method performed by a decoding apparatus, the method comprising:
obtaining image information including prediction mode information and residual information through a bitstream;
deriving transform coefficients based on the residual information;
deriving residual samples based on the transform coefficients;
deriving prediction samples based on the prediction mode information;
generating reconstructed samples based on the prediction samples and the residual samples;
deriving filter coefficients for an adaptive loop filter (ALF) procedure for the reconstructed samples; and
generating modified reconstructed samples based on the reconstructed samples and the filter coefficients,
wherein the image information includes information related to absolute values of luma filter coefficients for the ALF procedure and information related to absolute values of chroma filter coefficients for the ALF procedure,
wherein the information related to the absolute values of the luma filter coefficients for the ALF procedure includes a syntax element for an absolute value of a luma filter coefficient,
wherein the information related to the absolute values of the chroma filter coefficients for the ALF procedure includes a syntax element for an absolute value of a chroma filter coefficient,
wherein the syntax element for the absolute value of the luma filter coefficient and the syntax element for the absolute value of the chroma filter coefficient are coded based on 0-th order exponential golomb coding, and
wherein a value of the syntax element for the absolute value of the luma filter coefficient and a value of the syntax element for the absolute value of the chroma filter coefficient are within a predetermined range.
2. The image decoding method of claim 1 , wherein the image information includes parameter sets and ALF data,
wherein at least one of the parameter sets includes an adaptation parameter set (APS),
wherein the ALF data includes the information related to absolute values of luma filter coefficients for the ALF procedure and the information related to absolute values of chroma filter coefficients for the ALF procedure, and
wherein the ALF data is included in the APS.
3. The image decoding method of claim 1 , wherein the image information includes header information and an ALF-related adaptation parameter set (APS),
wherein the header information includes information related to a number of ALF-related APS IDs,
wherein the number of ALF-related APS IDs is derived based on a value of information related to the number of ALF-related APS IDs, and
wherein a number of ALF-related APS ID syntax elements is equal to the number of ALF-related APS IDs is included in the header information.
4. The image decoding method of claim 1 , wherein the image information includes header information and an ALF-related adaptation parameter set (APS),
wherein the header information includes an ALF availability flag indicating whether or not the ALF is available for usage within a picture or slice and information related to a number of ALF-related APS IDs,
wherein, when a value of the ALF availability flag is equal to 1, the header information includes the information related to a number of ALF-related APS IDs, and
wherein a value of the information related to a number of ALF-related APS IDs is equal to the number of ALF-related APS IDs.
5. The image decoding method of claim 1 , wherein the predetermined range is from 0 to 128, inclusive.
6. An image encoding method performed by an encoding apparatus, the method comprising:
deriving prediction samples for a current block;
generating prediction mode information based on the prediction samples;
deriving residual samples for the current block;
deriving transform coefficients based on the residual samples;
generating residual information based on the transform coefficients;
generating reconstructed samples for the current block;
deriving filter coefficients for an adaptive loop filter (ALF) procedure for the reconstructed samples;
generating ALF-related information based on the filter coefficients; and
encoding image information including the residual information and the ALF-related information,
wherein the image information includes information related to absolute values of luma filter coefficients for the ALF procedure and information related to absolute values of chroma filter coefficients for the ALF procedure,
wherein the information related to the absolute values of the luma filter coefficients for the ALF procedure includes a syntax element for an absolute value of a luma filter coefficient,
wherein the information related to the absolute values of the chroma filter coefficients for the ALF procedure includes a syntax element for an absolute value of a chroma filter coefficient,
wherein the syntax element for the absolute value of the luma filter coefficient and the syntax element for the absolute value of the chroma filter coefficient are coded based on 0-th order exponential golomb coding, and
wherein a value of the syntax element for the absolute value of the luma filter coefficient and a value of the syntax element for the absolute value of chroma filter coefficient are within a predetermined range.
7. The image encoding method of claim 6 , wherein the image information includes parameter sets and ALF data,
wherein at least one of the parameter sets includes an adaptation parameter set (APS),
wherein the ALF data includes information related to absolute values of luma filter coefficients for the ALF procedure and information related to absolute values of chroma filter coefficients for the ALF procedure, and
wherein the ALF data is included in the APS.
8. The image encoding method of claim 6 , wherein the image information includes header information and an ALF-related adaptation parameter set (APS),
wherein the header information includes information related to a number of ALF-related APS IDs,
wherein the number of ALF-related APS IDs is derived based on a value of information related to the number of ALF-related APS IDs, and
wherein a number of ALF-related APS ID syntax elements is equal to the number of ALF-related APS IDs is included in the header information.
9. The image encoding method of claim 6 , wherein the image information includes header information and an ALF-related adaptation parameter set (APS),
wherein the header information includes an ALF availability flag indicating whether or not the ALF is available for usage within a picture or slice and information related to a number of ALF-related APS IDs,
wherein, when a value of the ALF availability flag is equal to 1, the header information includes the information related to a number of ALF-related APS IDs, and
wherein a value of the information related to a number of ALF-related APS IDs is equal to the number of ALF-related APS IDs.
10. The image encoding method of claim 6 , wherein the predetermined range is from 0 to 128, inclusive.
11. A non-transitory computer readable digital storage medium storing a bitstream generated by an image encoding method, the image encoding method comprising:
deriving prediction samples for a current block;
generating prediction mode information based on the prediction samples;
deriving residual samples for the current block;
deriving transform coefficients based on the residual samples;
generating residual information based on the transform coefficients;
generating reconstructed samples for the current block;
deriving filter coefficients for an adaptive loop filter (ALF) procedure for the reconstructed samples;
generating ALF-related information based on the filter coefficients; and
encoding image information to generate the bitstream, wherein the image information includes the residual information and the ALF-related information,
wherein the image information includes information related to absolute values of luma filter coefficients for the ALF procedure and information related to absolute values of chroma filter coefficients for the ALF procedure,
wherein the information related to the absolute values of the luma filter coefficients for the ALF procedure includes a syntax element for an absolute value of a luma filter coefficient,
wherein the information related to the absolute values of the chroma filter coefficients for the ALF procedure includes a syntax element for an absolute value of a chroma filter coefficient,
wherein the syntax element for the absolute value of the luma filter coefficient and the syntax element for the absolute value of the chroma filter coefficient are coded based on 0-th order exponential golomb coding, and
wherein a value of the syntax element for the absolute value of the luma filter coefficient and a value of the syntax element for the absolute value of chroma filter coefficient are within a predetermined range.