Method and apparatus for coding image using adaptation parameter set

1. A method of decoding an image signal including a current picture with a decoding apparatus, comprising:

obtaining, with the decoding apparatus, coefficients of a current block in the current picture from a bitstream;

decoding, with the decoding apparatus, a residual block of the current block by performing inverse-quantization on the coefficients based on a quantization-related parameter from the bitstream; and

reconstructing, with the decoding apparatus, the current block based on the decoded residual block,

wherein the quantization-related parameter is obtained from an adaptation parameter set (APS) included in the bitstream,

wherein the adaptation parameter set includes at least one of parameter type information indicating a parameter type carried in the adaptation parameter set among a plurality of parameter types pre-defined in the decoding apparatus or identification information for identifying one of a plurality of parameter candidates defined for each of the parameter types,

wherein the plurality of parameter types include an ALF (adaptive loop filter)-related parameter, a LMCS (luma mapping with chroma scaling)-related parameter, and the quantization-related parameter,

wherein, a value of the identification information is in a range of 0 to 2 N −1 when the parameter type information indicates the ALF-related parameter or the quantization-related parameter, while a value of the identification information is in a range of 0 to 2 M −1 when the parameter type information indicates the LMCS-related parameter, and

wherein a value of N is different from a value of M.

2. The method of claim 1 , wherein the value of N is greater than the value of M.

3. The method of claim 2 , wherein the plurality of parameter types use a space separated from each other for the identification information.

4. The method of claim 3 , wherein one or more parameter candidates with different identification information are defined in the space for each of the parameter types.

5. The method of claim 1 , wherein decoding the residual block of the current block comprises:

obtaining, with the decoding apparatus, a scaling list for the inverse-quantization based on the quantization-related parameter;

deriving, with the decoding apparatus, a scaling factor based on the scaling list and a predetermined weight; and

applying, with the decoding apparatus, the derived scaling factor to the coefficients of the current block.

6. The method of claim 5 , wherein the weight is obtained from one of weight candidate lists pre-defined in the decoding apparatus.

7. The method of claim 6 , wherein a first list of the weight candidate lists is representative of {40, 45, 51, 57, 64, 72} and a second list of the weight candidate lists is representative of {57, 64, 72, 80, 90, 102}.

8. The method of claim 7 , wherein in response to a case where the current block is a block encoded in a transform skip mode, the weight is obtained from the first list, and

wherein in response to a case where the current block is not the block encoded in the transform skip mode, the weight is obtained from the second list.

9. A method of encoding an image signal including a current picture with an encoding apparatus, comprising:

obtaining, with the encoding apparatus, quantized coefficients of a current block in the current picture from a residual signal of the current block; and

generating, with the encoding apparatus, a bitstream by encoding the quantized coefficients of the current block,

wherein the quantized coefficients are obtained by performing quantization based on a quantization-related parameter,

wherein the quantization-related parameter is encoded in an adaptation parameter set (APS) included in the bitstream,

wherein the adaptation parameter set includes at least one of parameter type information indicating a parameter type carried in the adaptation parameter set among a plurality of parameter types pre-defined in the encoding apparatus or identification information for identifying one of a plurality of parameter candidates defined for each of the parameter types,

wherein the plurality of parameter types include an ALF (adaptive loop filter)-related parameter, a LMCS (luma mapping with chroma scaling)-related parameter, and the quantization-related parameter,

wherein, a value of the identification information is in a range of 0 to 2 N −1 when the parameter type information indicates the ALF-related parameter or the quantization-related parameter, while a value of the identification information is in a range of 0 to 2 M −1 when the parameter type information indicates the LMCS-related parameter, and

wherein a value of N is different from a value of M.

10. A non-transitory computer-readable medium for storing data associated with an image signal including a current picture, comprising:

a bitstream including a quantization-related parameter for inverse-quantization of coefficients of a current block in the current picture,

wherein the quantization-related parameter is obtained from an adaptation parameter set (APS) included in the bitstream,

wherein the adaptation parameter set includes at least one of parameter type information indicating a parameter type carried in the adaptation parameter set among a plurality of parameter types pre-defined in a decoding apparatus or identification information for identifying one of a plurality of parameter candidates defined for each of the parameter types,

wherein the plurality of parameter types include an ALF (adaptive loop filter)-related parameter, a LMCS (luma mapping with chroma scaling)-related parameter, and the quantization-related parameter,

wherein, a value of the identification information is in a range of 0 to 2 N −1 when the parameter type information indicates the ALF-related parameter or the quantization-related parameter, while a value of the identification information is in a range of 0 to 2 M −1 when the parameter type information indicates the LMCS-related parameter, and

wherein a value of N is different from a value of M.