Encoding device, decoding device, encoding method, and decoding method for coding efficiency

1. A decoding device comprising:

processing circuitry configured to:

decode fixed point precision representing precision of a weighting factor that is used for multiplying a reference image;

determine a first reference value based on the fixed point precision;

decode the weighting factor by adding the first reference value to a first difference value that is a difference value between the weighting factor and the first reference value;

determine a second reference value of an offset to be added to the reference image for correcting the pixel value, by subtracting a value obtained by both multiplying a median value of a maximum pixel value by the weighting factor and shifting to right for a bit or bits of the fixed point precision, from the median value; and

decode the offset by adding the second reference value to a second difference value that is a difference value between the offset and the second reference value,

wherein the first difference value is included in a first range of given bit precision, the first range having 0 at an approximate center, and the second difference value is included in a second range of given bit precision, the second range having a given value as approximate center.

2. The decoding device according to claim 1 , wherein the first range is of −128 to 127.

3. The decoding device according to claim 1 , wherein the first reference value indicates a factor to be set if a difference of pixel value between a reference image and a target image to be encoded is less than or equal to a specific value.

4. The decoding device according to claim 1 , wherein the second range is a fixed range of the given bit precision.

5. The decoding device according to claim 1 , wherein the processing circuitry is configured to perform a clipping process such that the offset is included in the second range when the offset is not included in the second range.

6. The decoding device according to claim 1 , wherein the processing circuitry is configured to derive the first reference value being 2 raised to the power of the fixed point precision.

7. A decoding method comprising:

decoding, via processing circuitry, fixed point precision representing precision of a weighting factor that is used for multiplying a reference image;

determining, via the processing circuitry, a first reference value based on the fixed point precision;

decoding, via the processing circuitry, the weighting factor by adding the first reference value to a first difference value that is a difference value between the weighting factor and the first reference value;

determining, via the processing circuitry, a second reference value of an offset to be added to the reference image for correcting the pixel value, by subtracting a value obtained by both multiplying a median value of a maximum pixel value by the weighting factor and shifting to right for a bit or bits of the fixed point precision, from the median value; and

decoding, via the processing circuitry, the offset by adding the second reference value to a second difference value that is a difference value between the offset and the second reference value,

wherein the first difference value is included in a first range of given bit precision, the first range having 0 at an approximate center, and the second difference value is included in a second range of given bit precision, the second range having a given value as approximate center.

8. The decoding method according to claim 7 , wherein the first range is of −128 to 127.

9. The decoding method according to claim 7 , wherein the first reference value indicates a factor to be set if a difference of pixel value between a reference image and a target image to be encoded is less than or equal to a specific value.

10. The decoding method according to claim 7 , wherein the second range is a fixed range of the given bit precision.

11. The decoding method according to claim 7 , further comprising:

performing, via the processing circuitry, a clipping process such that the offset is included in the second range when the offset is not included in the second range.

12. The decoding method according to claim 7 , wherein the deriving derives the first reference value being 2 raised to the power of the fixed point precision.

13. A decoding device comprising:

means for decoding fixed point precision representing precision of a weighting factor that is used for multiplying a reference image;

means for determining a first reference value based on the fixed point precision;

means for decoding the weighting factor by adding the first reference value to a first difference value that is a difference value between the weighting factor and the first reference value;

means for determining a second reference value of an offset to be added to the reference image for correcting the pixel value, by subtracting a value obtained by both multiplying a median value of a maximum pixel value by the weighting factor and shifting to right for a bit or bits of the fixed point precision, from the median value; and

means for decoding the offset by adding the second reference value to a second difference value that is a difference value between the offset and the second reference value,

wherein the first difference value is included in a first range of given bit precision, the first range having 0 at an approximate center, and the second difference value is included in a second range of given bit precision, the second range having a given value as approximate center.