Of itu-t sg16 wp3 and iso/iec jtc1/SC29/WG11

JCTVC-O0363 Colour Mapping SEI message [P. Bordes (Technicolor)] [late]

Reviewed Thu pm (GJS).

This contribution proposes a colour mapping SEI message to support colour mapping post-processing on reconstructed frames. The colour mapping function is coded using a 3D Colour LUT.

There was a similar but somewhat different proposal N0180 at the previous meeting.

It provides an expression of an encoder-preferred LUT mapping from the colour representation indicated in Annex E to an alternative colour space for rendering on an alternative display.

It was suggested not to use the "repetition period" syntax convention.

The LUT was specified using an "octree" structuring.

The proposed text had problems with respect to our editorial conventions, e.g. for syntax element names.

3-8 kilobits was suggested as the typical LUT size.

The previous meeting report said "It was remarked that this seems closely related to new parent-level inputs under substantial consideration – e.g. input from studios on XYZ and input submitted for CICP consideration. It may also be related to the colour gamut scalability, in the sense that it provides a way to provide compatible service targeting alternative displays."

It was asked how large the LUT would be. The contributor said it could sometimes be pretty small and that 9x9x9 is typical (uncompressed size).

A participant said that 3D LUTs are used commonly in production environments, but not in consumer devices because the complexity of using them is high.

An interpolation needs to be performed at the receiving side to interpret the data. How this is done was not described in the contribution, and the contributor said that various methods are used.

The contributor said it could be expected to be adapted on individual scenes.

Some complexity concerns were expressed about using this.

Another contributor said that the existing tone mapping SEI message may have some similar complexity concerns.

It was asked whether this is the best approach and whether the complexity is appropriate, and that the parameters may need to be refined.

Further study was encouraged.