Colour conversion within a hierarchical coding scheme

1. A method of encoding a signal, the method comprising:

processing an input signal at least by converting the input signal from a first color space to a second color space, to produce a first processed signal;

encoding, by a first encoding module, the first processed signal to generate a first encoded signal;

decoding the first encoded signal to generate a decoded signal;

processing the decoded signal at least by converting the decoded signal from the second color space to the first color space, to produce a second processed signal; and

processing, by a second encoding module, the second processed signal and the input signal to generate a second encoded signal,

wherein the second encoded signal contains additional ancillary data for reconstruction of the input signal using the first encoded signal and the additional ancillary data contains metadata for reconstructing a high dynamic range signal.

2. The method of claim 1 , wherein the second encoded signal comprises a residual signal or an adjustment signal for reconstruction of the input signal using the first encoded signal.

3. The method of claim 2 , wherein generating the residual signal or the adjustment signal comprises taking a difference between the input signal and the second processed signal.

4. The method of claim 1 , wherein the method comprises down-sampling the input signal.

5. The method of claim 4 , wherein the down-sampling reduces a resolution of the input signal.

6. The method of claim 4 , wherein the method comprises down-sampling the input signal before converting the input signal from a first color space to a second color space and up-sampling the decoded signal before converting the decoded signal from the second color space to the first color space.

7. The method of claim 4 , wherein the method comprises down-sampling the input signal after converting the input signal from a first color space to a second color space and up-sampling the decoded signal after converting the decoded signal from the second color space to the first color space.

8. The method of claim 1 , wherein the converting from a first color space to a second color space comprises one or more of the following operations:

mapping a color space;

changing a sampling pattern;

converting from a first bit depth to a second bit depth, wherein the first bit depth is greater than the second bit depth;

changing a dynamic range of the luminance component;

changing the color gamut;

changing the electro-optic transfer function model;

changing the lowest luminance level;

changing the highest luminance level; and

tone mapping.

9. The method of claim 1 , wherein the input signal comprises a plurality of frames in succession, and wherein each successive frame is encoded by the first encoding module.

10. The method of claim 1 , wherein the step of converting the input signal from a first color space to a second color space is non-linear.

11. The method of claim 1 , wherein the step of converting the input signal from a first color space to a second color space, to produce a first processed signal, is non-predictive.

12. A method of decoding a signal, the method comprising:

decoding, by a first decoding module, a first encoded signal to generate a first decoded signal;

decoding, by a second decoding module, a second encoded signal to generate a second decoded signal;

processing the first decoded signal at least by converting said first decoded signal from a first color space to a second color space, to produce a processed decoded signal;

processing the second decoded signal and the processed decoded signal by the second decoding module to generate a combined decoded signal,

wherein the second encoded signal contains additional ancillary data for reconstruction of the input signal using the first encoded signal and the additional ancillary data contains metadata for reconstructing a high dynamic range signal.

13. The method of claim 12 , comprising selecting to convert the combined decoded signal back to the first color space when a display is capable of displaying a signal only in the first color space.

14. The method of claim 12 , wherein the second encoded signal comprises a residual signal or an adjustment signal for reconstruction of an original input signal using the first encoded signal, wherein the residual signal or the adjustment signal is added to the processed decoded signal to generate the combined decoded signal.

15. The method of claim 12 , wherein the converting from a first color space to a second color space comprises converting from a non-high dynamic range signal to a dynamic range signal.

16. The method of claim 15 , comprising sensing if a connected display is unable to display the high dynamic range signal, and if so, outputting the first decoded signal.

17. The method of claim 12 , wherein the first encoded signal comprises all frames of the combined decoded signal, wherein each frame in the first encoded signal is decoded by the first decoding module and provides a base version of the combined decoded signal, and wherein the second encoded signal comprises enhancement information for each frame of the base version.

18. A non-transitory computer-readable storage medium comprising instructions which when executed by a processor cause the processor to:

process an input signal at least by converting the input signal from a first color space to a second color space, to produce a first processed signal;

encode, by a first encoding module, the first processed signal to generate a first encoded signal;

decode the first encoded signal to generate a decoded signal;

process the decoded signal at least by converting the decoded signal from the second color space to the first color space, to produce a second processed signal; and

process, by a second encoding module, the second processed signal and the input signal to generate a second encoded signal,

wherein the second encoded signal contains additional ancillary data for reconstruction of the input signal using the first encoded signal and the additional ancillary data contains metadata for reconstructing a high dynamic range signal.