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

[Tim Nicholson]

On 16/10/12 19:17, Bob Maple wrote:
> Still trying to get this one solved.  I'd been working off-list with
> Thomas Worth and here's what we've discovered so far.

I've been looking at some other. more pressing issues wrt .mov's, but
haven't forgotten this so Iam playing a bit of catch up here...

> 
> Using "ffprobe -show_packets" on ProRes files made by ffmpeg and ones
> made on a Mac under Final Cut or even files directly from the ARRI Alexa
> camera, it seems that ALL "proper" FCP ProRes Quicktimes are 16-bit
> aligned;  That is, every audio and video packet seems to be an even
> length, and the offsets are on even bytes.  Files generated by ffmpeg
> wind up about 25% odd-length and thus cause subsequent un-alignment.
> 

Is this for video only or both?

> This seems like a possible likely reason for the odd performance issues,
> with the inconsistent behavior of dropped frames.  I don't know if
> Quicktime specifies any sort of alignment, as other files generated by
> Quicktime Pro its self in other codecs don't seem to be strictly
> aligned;  but I've run dozens of "proper" ProRes files through ffprobe
> generated by both FCP and the ARRI Alexa camera, and they are all 16-bit
> aligned.
> 

ISTR you previously thought it was an issue with the A/V interleave, are
you now saying that is not the case?

> I've been browsing through the source trying to see if there's a hack I
> could do as a test, but I'm completely new to working with ffmpeg much
> less developing for it, so I'm a bit lost.  I'm not sure how to even
> make the ProRes encoder somehow come up with even lengths or how/why
> Apple's ProRes encoder seems to wind up that way, or if they are just
> doing padding, or what.
> 
> Anyway, if anyone who is more familiar with the source is willing to
> give it a look I'd be much appreciative!
> 
> 
> |  Bob Maple
> [...]
-- 
Tim