Encoding device, decoding device and program

1. An encoding device that encodes each encoding-target block generated by dividing an image that includes three or more components including a first component, a second component, and a third component, the encoding device comprising:

a predictor configured to generate, for each of the components, a prediction block corresponding to the encoding-target block;

a residual generator configured to generate, for each of the components, a prediction residual that represents a difference between the encoding-target block and the prediction block;

a color space transformer configured to perform a color space transform process on the prediction residual of each of the components;

a transformer configured to generate transform coefficients by performing a transform process on the prediction residual;

a quantization controller configured to determine a scaling list to be used in a quantization process on the transform coefficients; and

a quantizer configured to perform the quantization process on the transform coefficients by using the determined scaling list, wherein

in a case where the encoding device sets to use a variable scaling list in which at least partially different values can be set as values of elements of the scaling list, the quantization controller is configured to determine whether the variable scaling list is used or a uniform scaling list in which the elements have equal values is used, based on whether or not the color space transformer performs the color space transform process.

2. The encoding device according to claim 1 , wherein in the case where the encoding device sets to use the variable scaling list, the quantization controller is configured to:

determine the variable scaling list as the scaling list when the color space transformer does not perform the color space transform process; and

determine the uniform scaling list as the scaling list when the color space transformer performs the color space transform process.

3. The encoding device according to claim 1 , wherein in a case where the encoding device sets to use a variable scaling list in which at least partially different values can be set as values of elements of the scaling list, the quantization controller is configured to change correspondences between the three or more components and scaling lists for the individual components, based on whether or not the color space transformer performs the color space transform process.

4. The encoding device according to claim 3 , wherein in the case where the encoding device sets to use the variable scaling list, the quantization controller is configured to:

determine a first scaling list for an R component that is the first component, a second scaling list for a G component that is the second component, and a third scaling list for a B component that is the third component when the color space transformer does not perform the color space transform process; and

determine the second scaling list for a Y component that is the first component when the color space transformer performs the color space transform process.

5. The encoding device according to claim 1 , further including an entropy encoder, wherein

the entropy encoder is configured to output a sequence parameter set or an adaptation parameter set including information indicating whether or not operation of determining the scaling list based on the color space transform process is performed.

6. A decoding device that decodes each decoding-target block generated by dividing an image that includes three or more components including a first component, a second component, and a third component, the decoding device comprising:

an entropy decoder configured to decode, for each of the components, quantized transform coefficients in the decoding-target block from a bit stream;

a predictor configured to generate, for each of the components, a prediction block corresponding to the decoding-target block;

an inverse quantization controller configured to determine a scaling list to be used in an inverse quantization process;

an inverse quantizer configured to generate transform coefficients by performing the inverse quantization process on the quantized transform coefficients by using the determined scaling list,

an inverse transformer configured to generate a prediction residual by performing an inverse transform process on the transform coefficients;

a color space inverse transformer configured to perform a color space inverse transform process on the prediction residual; and

a combiner configured to generate a decoded block by combining the prediction residual and the prediction block, wherein

in a case where an encoding side sets to use a variable scaling list in which at least partially different values can be set as values of elements of the scaling list, the inverse quantization controller is configured to determine whether the variable scaling list is used or a uniform scaling list in which the elements have equal values is used, based on whether or not the color space inverse transformer performs the color space inverse transform process.

7. The decoding device according to claim 6 , wherein in the case where the encoding side sets to use the variable scaling list, the inverse quantization controller is configured to:

determine the variable scaling list as the scaling list when the color space inverse transformer does not perform the color space inverse transform process; and

determine the uniform scaling list as the scaling list when the color space inverse transformer performs the color space inverse transform process.

8. The decoding device according to claim 6 , wherein in a case where an encoding side sets to use a variable scaling list in which at least partially different values can be set as values of elements of the scaling list, the inverse quantization controller is configured to change correspondences between the three or more components and scaling lists for the individual components, based on whether or not the color space inverse transformer performs the color space inverse transform process.

9. The decoding device according to claim 8 , wherein in the case where the encoding side sets to use the variable scaling list, the inverse quantization controller is configured to

determine a first scaling list for an R component that is the first component, a second scaling list for a G component that is the second component, and a third scaling list for a B component that is the third component when the color space inverse transformer does not perform the color space inverse transform process, and

determine the second scaling list for a Y component that is the first component when the color space inverse transformer performs the color space inverse transform process.

10. The decoding device according to claim 6 , wherein the entropy decoder is configured to acquire a sequence parameter set or an adaptation parameter set including information indicating whether or not operation of determining the scaling list based on the color space inverse transform process is performed.

11. A non-transitory computer-readable recording medium storing a program causing a computer to function as the encoding device according to claim 1 .

12. A non-transitory computer-readable recording medium storing a program causing a computer to function as the decoding device according to claim 6 .