[FFmpeg-user] Tagging ProRes as BT.709 not BT.601

[Bob Maple]

> The host application uses a 601 or 709 decoding matrix based on the values
> in the MOV's "colr" atom (specifically, the nclc atom within it). If one
> isn't present, it's possible the application will default to 601 for 4:2:2
> sources. I'd start looking there. I'm not sure avformat writes such atoms,
> however.

Yeah, I'm turning up empty.  I just found 'AtomBox Studio' from 
jongbel.com and it looks like no, ffmpeg isn't writing the colr atom so 
that explains why I can't find anything in the source :)  It looks like 
MediaInfo just arbitrarily says 'BT.601' even though it doesn't seem to 
be explicitly tagged in the file at all.

I do so hate Quicktime...