Support H.264/AAC/MP3 video/audio playback on desktop Firefox (https://bugzilla.mozilla.org/show_bug.cgi?id=799318)
On Linux Firefox will use GStreamer, the same backend also used in Firefox OS, its not enabled in the nightly builds since not all distros have the right version of GStreamer and it ca not be loaded dynamically right now (https://bugzilla.mozilla.org/show_bug.cgi?id=794282)
For OS X the plan seams to be to use AV Foundations but no patch has been submitted so far. (https://bugzilla.mozilla.org/show_bug.cgi?id=801521)