[FFmpeg-user] convert from bt601 to bt709
nichot20 at yahoo.com
Fri Jun 6 08:28:13 CEST 2014
On 06/06/14 00:18, Bob Maple wrote:
>> I think it's in an atom called ACLR; I doubt ffmpeg writes this either...
> So in looking at the source, ffmpeg _does_ write this Avid extension if
> the codec is DNxHD, and hard-codes it as 'RGB range' which sounds wrong
> but the Avid codecs give the right result and it looks right in
> Quicktime Player. This was converting v210 (Uncompressed 4:2:2 10-bit)
> to DNxHD.
> With that said, I just did some tests from a 10-bit RGB DPX source to
> DNxHD and I can't make it right either. The range gets re-scaled to
> 16-235 (even though it already is) and the color primaries aren't
> right... but the math for this is starting to go out of my territory,
> and trying to figure out the path through the code is going even further.
ISTR that if you give ffmpeg RGB it assumes its full range, it also by
default converts using 601 matrices. Although it has a number of
colourspaces defined which can be accessed in the libs using the API,
ffmpeg itself makes no use of them (Although I have a nagging feeling
that that may not be completely true anymore either).
There have been various threads on this subject over the years.
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