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

[Bob Maple]

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.

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.

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.

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
|
|  When love is gone, there's always justice.  And when justice is gone,
|  there's always force.  And when force is gone, there's always Mom.
|  Hi, Mom!   -Laurie Anderson