[FFmpeg-user] Questions about readout important metadata from DPX files ("logarthmic/linear") and recreate DPX with same metadata
Carl Eugen Hoyos
cehoyos at ag.or.at
Mon Mar 9 21:05:12 CET 2015
Dave Rice <dave <at> dericed.com> writes:
> >> As far as I tested I can say (for the
> >> ffv1-supported pixelformats "gbrp10le" and
> >> "gbrp12le") it works lossless. All FrameMD5s
> >> are equal:
> > (This is not the first time that I am slightly
> > surprised people use FFmpeg to prove that an
> > encoder of FFmpeg is lossless.)
> Why is this slightly surprising?
Assuming this is done to rule out bugs
I find it unlikely that ffv1 is not lossless
and that you will find out like this (as
opposed to feed random data to the codec).
I find it much more likely that a bug in
the dpx decoder exists: Since you use the
same decoder twice in above test you
would not find such a bug.
A bug in both gm and FFmpeg that leads to
identical output seems less likely to me.
Of course I do believe that framemd5 is
useful to compare frames.
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