Encoding device, decoding device, encoding method, and decoding method for efficient coding
According to an embodiment, an encoding device includes a deriving unit and an encoding unit. The deriving unit derives a first reference value based on fixed point precision representing roughness of a weighting factor that is used for multiplying a reference image. The encoding unit encodes a first difference value and the fixed point precision. The first difference value is a difference value between the weighting factor and the first reference. The weighting factor is included in a first range of given bit precision having the first reference value at approximate center. The first difference value is in the given range.
1. An encoding device comprising:
processing circuitry configured to
determine a first reference value based on fixed point precision representing precision of a weighting factor that is used for multiplying a reference image;
encode a first difference value and the fixed point precision, the first difference value being a difference value between the weighting factor and the first reference value;
determine a second reference value of an offset of a color difference to be added to the reference image for correcting 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 the right for a bit or bits of the fixed point precision, from the median value; and
encode 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 encoding device according to claim 1 , wherein the first range is −128 to 127.
3. The encoding 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 encoding device according to claim 1 , wherein the second range is a fixed range of the given bit precision.
5. The encoding 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 encoding device according to claim 1 , wherein the processing circuitry is configured to determine the first reference value being 2 raised to the power of the fixed point precision.
7. An encoding method comprising:
determining, via processing circuitry, a first reference value based on fixed point precision representing precision of a weighting factor that is used for multiplying a reference image;
encoding, via the processing circuitry, a first difference value and the fixed point precision, the first difference value being a difference value between the weighting factor and the first reference value;
determining, via the processing circuitry, a second reference value of an offset of a color difference to be added to the reference image for correcting 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 the right for a bit or bits of the fixed point precision, from the median value; and
encoding, via the processing circuitry, 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 encoding method according to claim 7 , wherein the first range is −128 to 127.
9. The encoding 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 encoding method according to claim 7 , wherein the second range is a fixed range of the given bit precision.
11. The encoding method according to claim 7 , further comprising:
performing, via the processing circuitry, a clipping process such that the offset is included in the first range when the offset is not included in the first range.
12. The encoding method according to claim 7 , wherein the determining of the first reference value determines the first reference value being 2 raised to the power of the fixed point precision.
13. An encoding device comprising:
means for determining a first reference value based on fixed point precision representing precision of a weighting factor that is used for multiplying a reference image
means for encoding a first difference value and the fixed point precision, the first difference value being a difference value between the weighting factor and the first reference value;
means for determining a second reference value of an offset of a color difference to be added to the reference image for correcting 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 encoding 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.