[FFmpeg-user] ? About ffmpeg's prores implemention

Phil Rhodes phil_rhodes at rocketmail.com
Fri Aug 28 11:10:26 EEST 2020

The ProRes implementation is not likely to be perfect in terms of Apple's internal spec. They do not publish the spec so we don't know. In general, it has been shown to be reasonably reliable when used with most software decoders. It has had problems in the past (I haven't checked for years) in playback on hardware devices such as Atomos and AJA recorders. It is possible to set ffmpeg up to create ProRes-like files that are wildly out of spec and are unlikely to play back satisfactorily on anything, but with sensible setup it's generally fine. "It's generally fine" is all you're getting, sadly. I use it freely in situations where I will have an opportunity to fix problems as they occur (they never have) but I would hesitate to use it, for instance, for submission of a final master to someone.
In general it's very difficult to figure out exactly when something has changed in a particular part of ffmpeg as no change log is published, at least nothing which calls out "we have changed something which affects prores," but the behaviour of the ProRes implementation has not changed in a way that's visible to me. Prores is a reasonably simple format, as these things go. It's technologically similar to MJPEG or DV.


    On Friday, 28 August 2020, 01:01:19 BST, Gary Yost <gary at yostopia.com> wrote:  
 ’ve got a question about the Prores implementation in ffmpeg because I’ve seen some odd behavior here with FCPX (running on a very beefy 16-core Mac Pro with 192Gram and an Afterburner card).  

When I output files from ffmpeg in ProresLT format and bring them into FCPX, they stutter badly… playback is ~5fps.  But when I transcode/optimize them in FCPX, which creates Prores422 versions of those files, they play back in FCPX seamlessly.

The ffmpeg files _used_ to play back seamlessly on this machine when I was doing this Jan-March, but I haven’t been using this workflow since March.  My questions are:

1.  Is the Prores implementation in ffmpeg a 100% accurate implementation as per the Apple spec?

2.  Has anything changed in the Prores code transcoding of ffmpeg in the lat 4 months?


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