[FFmpeg-user] xyz to rgb conversion

betonpfeiler betonpfeiler at googlemail.com
Tue Sep 10 17:48:31 CEST 2013

Am 10.09.2013 01:15, schrieb Carl Eugen Hoyos:
> betonpfeiler <betonpfeiler <at> googlemail.com> writes:
>> Is there any documentation? I couldn't find anything,
>> which parameter is used to turn the conversion on/off...
> Sorry if my original answer was unclear:
> You cannot turn the conversion on/off.
> By default, FFmpeg does no colour space
> conversion if not told so.
> If you have xyz input, and you tell ffmpeg
> to encode prores, a conversion will be
> done (automatically) because prores does
> not support xyz.
> As said, since I don't understand your
> usecase (you simply cannot use xyz as
> input for prores), I have difficulties
> answering your original question.
> Carl Eugen
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Sometimes we want to make a quick reference movie, for subtitling for 
example. The fastest way is to use the j2ks from the MXF Container as 
source. I know, that the 12bit DCI XYZ can't be mapped in the 8-bit RGB 
colorspace, so the direct mapped result becomes a little pale and 
greenish. Also you loose some colorinformation, which are outside the 
RGB colorspace, but for subtitling or audiomixes the colors are not so 
important, even an b/w video would be enough. (I know, that the easyDCP 
Player can export a 8-bit ProRes without colorconversion, it looks 
greenish and has some artifacts, but it's totaly fine for my usecase).

And how does ffmpeg recognize the XYZ colorspace? I haven't found a tool 
yet, which can guess the right colorspace of an image file (e.g. 16bit 
TIFF). I always assumed, that the colorspace is only given in the 
Metadata, am I wrong?
Does anybody have some good literature tips regarding colorcoding in 
video? I searched the web and found a lot of Blogentrys and so on, but 
it seems to be a topic where many things are unclear/many people have 
different opinions... As it's a hughe topic, I'm looking for a good entry.


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