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

[Thomas Worth]

On Sat, Oct 27, 2012 at 10:42 PM, Bob Maple <bobm-ffmpeg at burner.com> wrote:
> On 10/27/2012 2:40 PM, Thomas Worth wrote:
>
>> Bob was using the asetnsamples filter to force the muxer to write the
>> audio in larger chunks than normal. Could he have used -chunk_duration
>> with a value of say, 1000000 to group the muxing of audio/video into 1
>> second chunks?
>
>
> I played around with that first but couldn't get any results that made any
> sense to me versus the values I'd entered.  Most of the time I would get
> long runs of audio and video packets but then every so often it'd go VAVAVA
> in the middle and then back to longer runs.

I've seen AVFoundation do the same. It's not a perfect
AAAAAAAAVVVVAAAAAAAAVVVV throughout the entire file. Sometimes you'll
get a VA in there. Do you have a genuine ProRes file that's perfectly
muxed with an equal number of audio/video packets (meaning 2 audio per
1 video in the case of stereo PCM)? Can you confirm this is possible?


> But no matter what values I used for chunk_duration (I tried a second first,
> half, a quarter..) it seemed to make equally long runs.  Playing with
> chunk_size gave me similar results, I couldn't make heads or tails of my
> values versus what it made (-chunk_size 4096 looked almost the same as
> -chunk_size 32768)

I think -chunk_duration may be a better bet, as it groups chunks based
on time rather than size. Size will vary based on the codec and frame
content, but duration should be the same despite the codec or
compressibility of the image (see avformat.h for more info).