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

[Michael Niedermayer]

On Tue, Oct 23, 2012 at 10:42:47PM -0600, Bob Maple wrote:
> On 10/23/2012 5:12 PM, Bob Maple wrote:
> 
> >With my manufactured sources, I've managed to make some 30 second test
> >files from ffmpeg that are either all aligned, all unaligned but even
> >packet sizes (except the first), or a mixture.. and I'm not getting
> >conclusive results on any of them, either way.
> 
> OK I'm making a bit more progress.  None of my contrived test files
> seemed to be failing, yet I have some clips shot on DSLR that when
> re-encoded fail almost immediately.  So it dawned on me,  I believe
> my graphic tests just weren't complex enough.. the frames themselves
> were compressing down fairly small, so the raw data-to-time ratio
> was relatively low.
> 
> So I pulled in a still with lots of detail in it (branches, leaves,
> rocks) and managed to get two different versions made through
> ffmpeg, one with all the packet sizes even in length, and all
> aligned.
> 
> It plays back miserably!
> 
> I re-saved this from Quicktime Pro (basically letting it re-mux, no
> recompression of video or audio) and... the result seems to playback
> perfectly fine.
> 
> While all of the packets in this remux are even-sized, the entire
> thing is out of alignment file position wise, apparently due to
> something in the header winding up odd sized.. but no matter, it
> seems to play.  The primary difference is that the muxing rate is
> much longer than what ffmpeg generates.  For instance, ffmpeg makes:
> 
> VaaVaaVaVaaVaVaaVaVaaVaaVaVaaVaVaaVaVaaVaaVaVaaVaVaaVaVaaVaVaaVaaVaVaaVaVaaVaVaaVaaVaVaaVaVaaVaVaaVaVaaVaaVaVaaVaVaaVaVaaVaaVaVaaVaVaaVaVaaVaaVaVaaVaVaaVaVaaVaVaaVaaVaVaaVa
> 
> etc. while the Quicktime Pro remux (and other "real" ProRes files)
> look more like:
> 
> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaVVVVVVVVVVVVVVVaaaaaaaaaaaaaaaaaaaaaaaaVVVVVVVVVVVVVVVaaaaaaaaaaaaaaaaaaaaaaaaVVVVVVVVVVVVVVVaaaaaaaaaaaaaaaaaaaaaaaaVVVVVVVVVVVVVVV
> 
> At this point I'm feeling confident that it's a general performance
> issue with the very tight mux ffmpeg is doing, AND almost certainly
> exacerbated by the odd frame lengths in most situations which helps
> explain why the behavior is so erratic.
> 
> So my next question, is there any way to tell ffmpeg to mux/re-mux
> with larger runs, to see if this greatly improves the reliability of
> playback, or is this hard-coded into the muxer (in which case, is

see -chunk_duration and -chunk_size

also please retest latest ffmpeg, it is possible that some recent
bugfixes fixed the whole issue


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Observe your enemies, for they first find out your faults. -- Antisthenes
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