[Libquicktime-devel] Count image description extension crash in QT

[Balázs O. <oro...@gm...>]

Hi,

There was a bug in libquicktime-generated MOVs, which makes the
QuickTime API function CountImageDescriptionExtensionType() and/or
GetNextImageDescriptionExtensionType() crash.
This was discussed and eventually fixed here:
http://sourceforge.net/p/libquicktime/mailman/libquicktime-devel/thread/44736.91.22.94.234.1239326393.squirrel%40ipfmv1.e-technik.uni-stuttgart.de/

The behaviour was also discussed in the following places (among others):
http://trac.perian.org/ticket/103
http://lists.apple.com/archives/quicktime-api/2009/Jan/msg00128.html

I've noticed however, that if any user atom is present, but none of
the ones mentioned in the fix (pasp, clap, colr, fiel, gama), the
written MOV won't have the mentioned padding and will make programs
trying to use the QT function CountImageDescriptionExtensionType()
crash.
An example of this situation for example is when only a 'glbl' user
atom is present (created by ffmpeg for various codec headers).

I've attached a trivial patch to add the padding also when any user
atom is present, and I've verified with my own QuickTime components,
that MOV files generated this way no longer crash when using the
CountImageDescriptionExtensionType() function.

Greets,
Balázs