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

[Tim Nicholson]

On 03/01/13 23:06, Bob Maple wrote:
>> 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...

quite.

You do not say what your source material for ffmpeg is. If it is already
in YUV then ffmpeg will not change the colourspace, so you may have 709,
but untagged and assumed as 601, or 601 untagged depending on the original.

If the source was RGB ffmpeg will convert to YUV using a 601 conversion
matrix. (this is "hardwired" by the setting of the DEFAULT_CS or
somesuch enum so you can only change the behaviour by changing the value
and recompiling.

So there are multiple places where it can go wrong..
-- 
Tim