[FFmpeg-user] Decode FFV1 AVI back to DPX

[Dave Rice]

> On Dec 8, 2015, at 5:15 AM, Kieran O Leary <kieran.o.leary at gmail.com> wrote:
> 
> On Thu, Nov 26, 2015 at 11:35 AM, Abhishek Prasad
> <abhishek.prasad at efxmagic.com> wrote:
> 
>> After encoding a dpx sequence to avi/mxf with FFv1. How does one
>> decode/restore back to the dpx files?
> 
>> -----
> 
> Did you say that you encoded ffv1 in an mxf wrapper? Is that even
> possible, and if so, what was your command line output?

That is not possible yet. There were some discussions about it, but the effort would require registering a universal label and publishing a SMPTE document that documents the storage of FFV1 within MXF.

> It is indeed possible to decode back to DPX-  I've losslessly
> compressed 10bit RGB DPX to FFV1.mkv and back with matching framemd5s
> all the way. It's a beautiful thing.

But it's some context loss. For instance if the source DPX is logarithmic I'd be skeptical that the ffv1.mkv rendition would present logarithmically.

> I've included an audio argument
> which is optional, just remove it if you're silent.

IIRC, in ffmpeg options for non-existant tracks are ignored, so you may be able to leave the audio arguments in for media with no audio tracks.

> I've added
> framemd5s as well. I never losslessly compress/transcode without
> running a diff on the framemd5s of the source and output. Replace your
> startnumber and filename as applies to you.

Right. Using framemd5s is recommend for verifying losslessness. It prevents finding images like this: https://twitter.com/dericed/status/483626811356893184 <https://twitter.com/dericed/status/483626811356893184>.

Dave Rice

> ffmpeg -i input.avi output06%d -f framemd5 -an framemd5.md5
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