Decoding device and decoding method, and coding device and coding method

1. A conversion device comprising:

circuitry configured to

receive image data and conversion information, the image data pertaining to an image having luminance in a first dynamic range, and the conversion information pertaining to a conversion of dynamic range of the luminance of the image from the first dynamic range into a second dynamic range, and

convert the dynamic range of the luminance of the image based on the conversion information, wherein the conversion uses a knee point and the conversion information includes applicability information that indicates an applicability of the conversion information,

wherein the knee point is located at a coordinate that is defined by an input knee point and an output knee point, the input knee point specifying a luminance level of the knee point at the coordinate for the image having the luminance in the first dynamic range, and the output knee point specifying a luminance level of the knee point at the coordinate for the image after the conversion of the dynamic range of the luminance of the image into the second dynamic range.

2. The conversion device according to claim 1 , wherein the applicability information indicates a timing of when the conversion information is applied for the conversion of dynamic range.

3. The conversion device according to claim 1 , wherein the applicable information is conversion persistence information that indicates whether or not the conversion information is applied to a plurality of continuous pictures.

4. The conversion device according to claim 1 , wherein the conversion uses a knee function to map the dynamic range of the luminance of the image from the first dynamic range into the second dynamic range, and the knee function is defined by the knee point.

5. The conversion device according to claim 4 , wherein the conversion information includes pre-conversion information and post-conversion information,

wherein the pre-conversion information indicates a range of luminance which is a knee function target in the first dynamic range, and

wherein the post-conversion information indicates a range of luminance in the second dynamic range that corresponds to the range of luminance indicated by the pre-conversion information.

6. The conversion device according to claim 5 , wherein the pre-conversion information indicates the range of luminance which is converted by knee function at a same conversion ratio as a conversion range of the first dynamic range.

7. The conversion device according to claim 5 , wherein the conversion information includes a plurality of pairs of the pre-conversion information and the post-conversion information.

8. The conversion device according to claim 4 , wherein the conversion uses the knee function by mapping the dynamic range of the luminance of the image from the first dynamic range into the second dynamic range at a first conversion ratio to a point defined by the knee point and at a second conversion ratio from the point defined by the knee point.

9. The conversion device according to claim 4 , wherein the knee function is specified by a Supplemental Enhancement Information (SEI) message.

10. The conversion device according to claim 9 , wherein the SEI message includes a setting of a knee function id.

11. The conversion device according to claim 1 , wherein the conversion uses a knee function which is defined by a plurality of knee points.

12. The conversion device according to claim 1 , wherein the conversion uses a knee function by mapping the dynamic range of the luminance of the image from the first dynamic range into the second dynamic range, and a plurality of adjacent segments of the first dynamic range of the luminance are mapped to a corresponding plurality of adjacent segments of the second dynamic range of the luminance based on boundaries between adjacent segments defined by a plurality of knee points.