Method and device for encoding both a high-dynamic range frame and an imposed low-dynamic range frame

1. A method for encoding a frame whose pixel vales belong to a high-dynamic range and an imposed frame whose pixel values belong to a lower-dynamic range, wherein the method comprises:

determining a backlight frame from the luminance component of the frame;

calculating a residual frame responsive to the frame and the backlight frame; and

predictive-encoding the residual frame using a predictor of the residual frame calculated from said imposed frame, said imposed frame being a low-dynamic version of the frame to be encoded.

2. The method of claim 1 , wherein the imposed frame and the frame to be encoded have different color-grading.

3. The method of claim 1 , wherein the imposed frame and the frame to be encoded are expressed in different color spaces.

4. The method according to claim 1 , wherein the predictor of the residual frame is calculated from a decoded version of the imposed frame.

5. The method according to claim 1 , wherein calculating the predictor of the residual frame comprises mapping the decoded version of the imposed frame to the residual frame by using a color mapping function.

6. The method according to the claim 5 , wherein the color mapping function uses a 3D color Look Up Table.

7. The method according to claim 1 , wherein the backlight frame is further determined from the imposed frame.

8. The method according to the claim 7 , wherein determining the backlight frame comprises dividing each component of the frame by a component of the imposed frame.

9. The method according to claim 1 , wherein the method further comprises mapping the residual frame before predictive-encoding and inverse-mapping each component of the imposed frame before determining the backlight frame.

10. The method of claim 1 , wherein predictive-encoding the residual frame conforms to the SHVC standard.

11. A method for decoding a frame whose pixel values belong to a high-dynamic range from at least one bitstream, the method comprising:

obtaining a backlight frame by at least partial decoding of a bitstream;

obtaining a decoded imposed frame by at least partial decoding a bitstream, said decoded imposed frame being a low-dynamic version of the frame to be decoded;

obtaining a predictor from the decoded imposed frame;

predictive-decoding a decoded residual frame by at least partially decoding a bitstream and by using the predictor obtained from the decoded imposed frame; and

decoding the frame responsive to the decoded residual frame and the decoded backlight frame.

12. The method according to claim 11 , wherein the method further comprises:

obtaining parameters related to a 3D color LUT by at least partially decoding a bitstream; and

obtaining the predictor from the decoded imposed frame and the obtained parameters.

13. The method according to the claim 11 , wherein the predictor comprises a specific predictor for each region of a 3D color LUT.

14. The method of claim 11 , wherein predictive-decoding a decoded residual frame conforms to the SHVC standard.

15. A device for encoding a frame whose pixel values belong to a high-dynamic range and an imposed frame whose pixel values belong to a lower-dynamic range, wherein the device comprises a processor configured to:

determine a backlight frame from the luminance component of the frame;

calculate a residual frame responsive to the frame and the backlight frame; and

predictive-encode the residual frame using a predictor of the residual frame calculated from an imposed frame, said imposed frame being a low-dynamic version of the frame to be encoded.

16. A device for decoding frame to whose pixel values belong to a high-dynamic range from at least one bitstream, wherein the device comprises a processor configured to:

obtain a backlight frame by at least partial decoding of a bitstream;

obtain a frame, a decoded imposed frame, by at least partially decoding a bitstream, said decoded imposed frame being a low-dynamic version of the frame to be decoded;

obtain a predictor from the decoded imposed frame;

predictive-decode a decoded residual frame by at least partially decoding a bitstream and by using the predictor obtained from the decoded imposed frame; and

decode the frame responsive to the decoded residual frame and the decoded backlight frame.

17. A non-transitory program storage device, readable by a computer, tangibly embodying a program of instructions executable by the computer to perform a method for encoding a frame comprising:

retrieving a frame to encode whose pixel values belong to a high-dynamic range and an imposed frame whose pixel values belong to a lower-dynamic range;

determining a backlight frame from the luminance component of the frame;

calculating a residual frame responsive to the frame and the backlight frame; and

predictive-encoding the residual frame using a predictor of the residual frame calculated from the imposed frame, said imposed frame being a low-dynamic version of the frame to be encoded.

18. A non-transitory program storage device, readable by a computer, tangibly embodying a program of instructions executable by the computer to perform a method for decoding a frame whose pixel values belong to a high-dynamic comprising;

obtaining a backlight frame by at least partial decoding of a bitstream;

obtaining a decoded imposed frame by at least partial decoding a bitstream, said decoded imposed frame being a low-dynamic version of the frame to be decoded;

obtaining a predictor from the decoded imposed frame;

predictive-decoding a decoded residual frame by at least partially decoding a bitstream and by using the predictor obtained from the decoded imposed frame; and

decoding the frame responsive to the decoded residual frame and the decoded backlight frame.