[FFmpeg-user] Levels and Primaries
Carl Eugen Hoyos
cehoyos at ag.or.at
Wed Feb 12 12:11:07 CET 2014
Rio Kierkels <riokierkels <at> gmail.com> writes:
> Could be just my paranoia, but I always have the feeling
> that the decoder does some magic on the numbers or something.
(This may now be the terminology problem in the other
Concerning the decoder, I suspect that there actually is a
guarantee that an MPEG decoder in FFmpeg really only
outputs MPEG levels (unless told otherwise).
But is that really your question?
> Which is why right now I'm also not certain what
> I'm looking for in the output.
I thought you are looking for levels from 0 to 15 and
236 to 255 (but as said, I may just not understand the
problem that you say don't exist).
> I think it's on a byte level.
> So yeah if I've got the time I'll be going through
> the mxf files byte by byte...
Why not rawvideo which would make the task
indefinitely easier imo?
> That is why currently I'm content with the
> assumption that ffmpeg does the correct thing
> until I have the means to completely verify this
> myself when my coding and color science skills
> are of such a level that I can be confident
> that I'm doing the right thing.
Do you mean you want to improve your coding skills
so that you can (mathematically if you want) show
that the scaler does the correct thing?
I don't think this is realistically possible.
But to just test a large number of samples and
show that for the given samples, the output level
is always (as in "100%") correct does not need any
coding skills, just hexdump and grep (or python).
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