Encoding device, decoding device and program

1. An encoding device that performs encoding on each of blocks generated by dividing an image composed of two or more components including a first component and a second component, the encoding device comprising:

a predictor configured to generate, for each component, a prediction block corresponding to an encoding-target block based on a prediction mode;

a residual generator configured to generate, for each component, a prediction residual representing a difference between the encoding-target block and the prediction block;

a mode selector configured to select, for a prediction residual of the first component and a prediction residual of the second component, one encoding mode either an individual residual encoding mode performing a transform process and a quantization process on the first component and the second component for each single component, or a joint residual encoding mode performing a transform process and a quantization process on a joint prediction residual generated from the prediction residual of the first component and the prediction residual of the second component;

a quantization controller configured to determine a scaling list to be used in the quantization process based on the residual encoding mode selected by the mode selector; and

a joint transformer/quantizer configured to perform the quantization process on joint transform coefficients generated through the transform process of the joint prediction residual, using the scaling list determined by the quantization controller, in a case where the mode selector selects the joint residual encoding mode.

2. The encoding device according to claim 1 , wherein the quantization controller is configured to determine the scaling list to be used in the quantization process based on whether or not the mode selector selects the joint residual encoding mode.

3. The encoding device according to claim 2 , wherein

in a case where the mode selector selects the individual residual encoding mode, the quantization controller is configured to

determine a scaling list to be applied to quantization of transform coefficients of the first component from first candidates that are candidates for a scaling list corresponding to the first component, and

determine a scaling list to be applied to quantization of transform coefficients of the second component from second candidates that are candidates for a scaling list corresponding to the second component, and

the quantization controller is configured to determine a scaling list to be applied to quantization of the joint transform coefficients from third candidates different from the first candidates and the second candidates, in a case where the mode selector selects the joint residual encoding mode.

4. The encoding device according to claim 3 , wherein the third candidates include at least one of a scaling list in which default values defined by a system in advance are stored and a scaling list in which elements set for quantization of the joint transform coefficients on the encoding device side are stored.

5. The encoding device according to claim 1 , further comprising

an entropy encoder configured to signal to a decoding side, a flag indicating a scaling list to be used in a case where the joint residual encoding mode is applied in units of sequences, in units of pictures or in units of slices.

6. The encoding device according to claim 5 , wherein the flag is configured to indicate one of a scaling list to be applied to the first component and a scaling list to be applied to the second component as the scaling list to be used in a case where the joint residual encoding mode is applied.

7. The encoding device according to claim 1 , wherein the first component is a first chrominance component, and the second component is a second chrominance component.

8. A decoding device that performs decoding on each of blocks generated by dividing an image composed of two or more components including a first component and a second component, the decoding device comprising:

an entropy decoder configured to output a prediction mode and a first flag and quantized transform coefficients by decoding an encoded stream, the first flag indicating whether or not a joint residual encoding mode is applied on an encoding device side, wherein the joint residual encoding mode performs a transform process and a quantization process on a joint prediction residual generated from a prediction residual of the first component and a prediction residual of the second component at the encoder side;

an inverse quantization controller configured to determine a scaling list to be used in an inverse quantization process to be performed on the quantized transform coefficients based on the first flag; and

a joint inverse quantizer configured to perform the inverse quantization process on the quantized transform coefficients outputted from the entropy decoder, using the scaling list determined by the inverse quantization controller, in a case where the first flag indicates that the joint residual encoding mode is applied.

9. The decoding device according to claim 8 , wherein

in a case where the first flag indicates that an individual residual encoding mode is applied, the individual residual encoding mode performing, for each single component, a transform process and a quantization process on the prediction residual of the first component and the prediction residual of the second component, the inverse quantization controller is configured to

determine a scaling list to be applied to inverse quantization of quantized transform coefficients of the first component from first candidates that are candidates for a scaling list corresponding to the first component, and

determine a scaling list to be applied to inverse quantization of quantized transform coefficients of the second component from second candidates that are candidates for a scaling list corresponding to the second component, and

the inverse quantization controller is configured to determine a scaling list to be applied to inverse quantization of quantized joint transform coefficients from third candidates different from the first candidates and the second candidates, in a case where the first flag indicates that the joint residual encoding mode is applied.

10. The decoding device according to claim 9 , wherein the third candidates include at least one of a scaling list in which default values defined by a system in advance are stored and a scaling list in which elements set for quantization of the joint transform coefficients on the encoding device side are stored.

11. The decoding device according to claim 8 , wherein

the entropy decoder is configured to further output a second flag indicating a scaling list to be used in a case where the joint residual encoding mode is applied in units of sequences, in units of pictures or in units of slices by decoding the encoded stream, and

the inverse quantization controller is configured to determine the scaling list to be used in the inverse quantization process based on the first flag and the second flag.

12. The decoding device according to claim 11 , wherein the second flag indicates one of a scaling list to be applied to the first component and a scaling list to be applied to the second component as a scaling list to be used in a case where the joint residual encoding mode is applied.

13. The decoding device according to claim 8 , wherein the first component is a first chrominance component, and the second component is a second chrominance component.

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

15. A non-transitory computer-readable medium storing a program causing a computer to function as the decoding device according to claim 8 .