[FFmpeg-user] Questions about readout important metadata from DPX files ("logarthmic/linear") and recreate DPX with same metadata

[Dave Rice]

Hi Carl,

> On Mar 9, 2015, at 9:24 AM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
> 
> Christoph Gerstbauer <christophgerstbauer <at> gmail.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? Isn’t verifying that an original source and a presumed lossless copy both decode to the same samples one of the primary purposes of framemd5? I put an article into trac about it: http://trac.ffmpeg.org/wiki/framemd5%20Intro%20and%20HowTo <http://trac.ffmpeg.org/wiki/framemd5%20Intro%20and%20HowTo>.

>> The Original has LOGARITHMIC 10bit (RGB 10bit log)
> 
> FFmpeg does not support logarithmic dpx 
> afaict.
> If this is really a feature that would 
> help you, it would be possible to force 
> the "logarithmic" flag on encoding (but 
> I am not convinced this is really useful).
> 
> (It is of course trivial to read the 
> information from the file but I wonder 
> how it would be useful given that FFmpeg 
> doesn't know what to do with the 
> information.)

I would be in favor in preserving this info even if FFmpeg does not (presently) use the information.
Dave

> Consider to upload a sample (or post a 
> gm command line).
> 
> Carl Eugen
> 
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