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

[Thomas Worth]

On Thu, Oct 18, 2012 at 8:45 AM, Tim Nicholson <nichot20 at yahoo.com> wrote:
> 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.
>>
>> 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
>
> I wonder if "other codecs" are fixed frame size? Or to put it another
> way Prores is kind of DNX++. DNX is fixed frame size, which helps
> seeking, and prores has a small amount of variability. I wonder if
> genuine prores adds the above constraint to help seek-ability which has
> been missed in the reverse engineering.

Wouldn't a straight remux of a genuine ProRes file tell us whether
this was the case or not? If the problem is indeed with the encoder,
then a remux of a genuine ProRes file (with audio) should behave
properly.