[FFmpeg-user] [Bulk] Re: ProRes Quicktimes with audio not playing back reliably

[Tim Nicholson]

On 25/09/12 09:45, Bob Maple wrote:
> On 9/25/2012 1:42 AM, Tim Nicholson wrote:
> 
>> As I understand it ProRes is a variable bit rate codec, with the
>> variable range quite constrained. I am wondering if the ffmpeg
>> implementation is allowing too great a spread in this variable range,
>> which in the case of simple material can go too low, and for complex
>> material to high?
> 
> I don't know.. if I encode to a video-only file with ffmpeg, they play
> fine.  It's only when I do the audio as well that it fails.
> 

Whilst I have seen that too on transcodes of noisy TK material, I have
also found that using the lavfi testsrc as input makes files that play
OK. I also found that remuxing in QT Pro improved the situation, but did
not fix it completely so it seems to be not just the muxer that may be
an issue, although I suspect from your tests, its probably the biggest
single contributor.

> Even if I take the video from ffmpeg and add the audio in Quicktime Pro
> myself, _that_ plays fine.. which is what suggested to me the muxing
> ffmpeg is doing was possibly at fault, and it's definitely drastically
> different based on poking around the files with ffprobe.
> 
> I've also tried all 3 ProRes encoders (prores, prores_anatoliy and
> prores_kostya) and get the same results.
> 
> I'm doubting ffmpeg is actually doing anything out of spec, but rather
> 'out of the ordinary' such that Quicktime pukes on it... being the
> craptacular piece of software it is...
>

I suspect its bit rate variability may be "out of spec", not that the
spec is open enough to check....

I am awaiting the results of a Baton test of ffmpeg created Pro Res
material to see if that flags anything.

> 
> |  Bob Maple
> 
> [..]


-- 
Tim