[Bug 740575] Fixing DTS in GStreamer

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=740575

--- Comment #80 from Matej Knopp <matej.knopp at gmail.com> ---
So, there are three ways to handle it.

Keep atom version 1 and signed (initially negative) CTTS; The file will conform
to specification, but iOS 7 and QuickTime player 7 will not be able to play it.
Not great.

Change version back to 0 and use signed CTTS anyway. The files will not
strictly conform to MP4 specification, but most players will likely play them,
because CTTS was signed in original QuickTime specification. So mov files can
contain negative CTTS and atom version = 0; This is what I'm doing right now,
since we produce files that are mostly "transient" and are targeting Apple
devices exclusively.  

If you don't want to have negative CTTS, you need to offset it by appropriate
amount, but then you also need to add that amount to other stream edit lists
(elst), so that you keep the A/V sync. Given that by the time CTTS is written
you have all timestamps, the amount should be easy to determine. This is best
option because it produces conforming files and doesn't need ctts atom version
= 1; But it needs some changes and I don't currently have time to implement and
test it right now. :-/

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