Image coding device and method based on filtering-related information signaling

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 the filter coefficients for the ALF procedure,

wherein the information related to the filter coefficients for the ALF procedure includes first syntax element for an absolute value of a filter coefficient and second syntax element for a sign of the filter coefficient,

wherein the filter coefficients for the ALF procedure are derived based on the first syntax element and the second syntax element,

wherein the first syntax element is 0-th order exponential golomb coded syntax, and

wherein a value of the first syntax element is within a predetermined range.

2 . The image decoding method of claim 1 , wherein the image information includes ALF data,

wherein the ALF data includes the first syntax element and the ALF data is included in APS (adaptation parameter set).

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 the filter coefficients for the ALF procedure,

wherein the information related to the filter coefficients for the ALF procedure includes first syntax element for an absolute value of a filter coefficient and second syntax element for a sign of the filter coefficient,

wherein the first syntax element is 0-th order exponential golomb coded syntax, and

wherein a value of the first syntax element is within a predetermined range.

7 . The image encoding method of claim 6 , wherein the image information includes ALF data,

wherein the ALF data includes the first syntax element and the ALF data is included in APS (adaptation parameter set).

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 the filter coefficients for the ALF procedure,

wherein the information related to the filter coefficients for the ALF procedure includes first syntax element for an absolute value of a filter coefficient and second syntax element for a sign of the filter coefficient,

wherein the first syntax element is 0-th order exponential golomb coded syntax, and

wherein a value of the first syntax element is within a predetermined range.

12 . A method for transmitting a bitstream 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;

encoding the bitstream including the residual information and the ALF-related information; and

transmitting image information including the bitstream,

wherein the image information includes information related to the filter coefficients for the ALF procedure,

wherein the information related to the filter coefficients for the ALF procedure includes first syntax element for an absolute value of a filter coefficient and second syntax element for a sign of the filter coefficient,

wherein the first syntax element is 0-th order exponential golomb coded syntax, and

wherein a value of the first syntax element is within a predetermined range.