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

Phil Rhodes phil_rhodes at rocketmail.com
Mon Aug 31 11:41:27 EEST 2020


    On Sunday, 30 August 2020, 23:21:16 BST, Edward Park <kumowoon1025 at gmail.com> wrote:  
 > I'm not sure what you are referring to, what's there to spread fud about??
I'm not sure what he's referring to, either, but just be aware you're talking mainly to software engineers here and they have a well-deserved reputation for being very difficult with, well, more or less anyone who isn't a software engineer. Don't be concerned, you haven't done anything wrong. They're like this with everyone. It's normal in the world of open source (it's comically bad behaviour, but it's normal).
For what it's worth I've noticed problems playing back ffmpeg's prores on hardware devices, but it usually seems to work OK in software decoders. If your environment has changed in that regard, perhaps by handing off prores decoding to a hardware device, that might be an issue that's hard to solve with ffmpeg-generated files. I never tried that hard to fix the hardware playback issues, but if you really need to, you might try fiddling around with some of the commandline parameters you're using, if that's something you have the option to do. This may all be old news to you, but the command I use is something like this:
ffmpeg -probesize 5000000 -i %INFILE% -c:v prores_ks -profile:v 4 -qscale:v 11 -vendor ap10 -chunk_duration 500000 -c:a pcm_s16le %OUTFILE%

I honestly can't remember most of what that does but the number after "-qscale:v" controls overall bitrate from 1 to 31. Reducing it increases bitrate (obviously!) and if you set it very low, it may create files that are wildly out of specification that Apple decoders may not like. I have not had problems with 11 (again, on software decoders). The "-profile:v" controls what sort of prores you're creating, from 0 to 4 or perhaps 1 to 4. I can't remember what number means what. The "-chunk_duration" as I recall stops Final Cut complaining about unoptimised media, or at least it certainly used to. Apparently you don't actually need "-vendor ap10" but it doesn't hurt.
I'm not sure what other command line options might have relevance for ProRes but I suspect this might be quite a complicated problem to solve.

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