Default video/audio codecs are the ones at the top of the list
Submitted by Jeff F.T.
Assigned to Jeff F.T.
After selecting a container, the video codec (and probably audio codec too) that gets selected is simply the one that happens to be at the top of the list (most of the time, Dirac), not the most common/useful one.
Imported from https://bugzilla.gnome.org/show_bug.cgi?id=637080