[FFmpeg-user] ProRes: ffmpeg vs. ffmbc

[Thomas Worth]

On Tue, May 22, 2012 at 12:01 AM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
> Jeremy Oddo <joddo <at> jerfu.com> writes:
>
>> I've been having a lot of success with ProRes QTs from ffmbc
>> but less so on the ffmpeg front.
>
>> Also, there seems to be a problem with FCP not accepting
>> ffmpeg ProRes files as "proper"
>
> Do you feel that this is sufficient for the developers to
> understand, reproduce and fix the problem?
>
> Consider opening a report including all necessary information
> on trac.

Carl, here's all the necessary information needed to fix this very old
and annoying bug.

This has been discussed before and the issue, as explained by Baptiste
Coudurier (who has already fixed this in ffmbc), is a problem with
ffmpeg's mov muxer writing audio chunk sizes incorrectly (or at least
not in a way Final Cut Pro wants):

http://ffmpeg.org/pipermail/ffmpeg-user/2012-March/005682.html

As Baptiste explains, "FCP expects audio chunks to be approximately
48000 samples."

Movies with co64 atoms (that is, MOVs over 4GB) do not have this
problem and do not throw the media performance warning in Final Cut
Pro. So, what this means is that audio chunk sizes are written
correctly when co64 is used (i.e. written with 64 bit offsets), just
not when 32 bit chunk offsets (stco) are written.

This is a BIG HINT for anyone who wants to fix this. I would gladly do
it, but I don't know avcodec source well enough. This fix would be
better handled by someone already familiar with avcodec source,
especially movenc.c.

I will happily assist anyone who needs to verify their work with Final
Cut Pro if they don't have a Mac.