MIME types and metadata encoding for Dolby Vision formats

[markafoltz]

This issue tracks some open comments on PR #300 by @chrisn.

From #300 (comment):

Dolby has registered a number of MIME types to represent their proprietary HDR metadata encodings, so remote playback capability detection for these formats would be handled by the remote-playback-source message, which accepts full MIME types.

I see. If we need to we can follow this up with them via the new A/V Media Formats CG, which started at TPAC 2022.

From #300 (comment):

Thanks. I've asked a colleague for advice on this part:

[2] Unclear if this happens in practice as HLG support may be a proprietary profile of Dolby Vision and not part of smpteSt2094-10.