Adapt annotations for HDR content

[nicholas-fr]

When the source content is HDR, to avoid using overly bright graphics, it may be useful to adapt the annotations overlayed (i.e. the white text, QR code pixels, and red arrows).

[jpiesing]

When someone commits to working on an HDR media profile, we should test that the current mezzanine content is suitable. It would need to be encoded, a test run with that content, captured by a camera & analysed by the observation framework. We should get confirm the suitability (or otherwise) of the current mezzanine content before a lot of encoding is done.

[gitwjr]

Deferred for future work.