Colour conversion within a hierarchical coding scheme

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 wide color gamut signal.

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 wide color gamut signal.