Let me add some news.
QuicktimePlayer 7.6 even crashes when you try to feed it with movies compressed with Handbrake and multi audio tracks. But this has to do with HB generating tracks with "unknown" language.
You could download "Subler" which lets you edit mp4 files. Change the language to English for example and save file optimized.
Than open in QT and make the edits audio assignment described here:
http://discussions.apple.com/thread.jspa?threadID=1706701&start=0&tstart=0
That is all very complicated and time consuming.
I'm sure the problem for Apple is to make 5.1 passthrough and normal stereo system sounds work at the same time. You can see how problematic this is when you change the volume in QT or iTunes when playback a 5.1 audio file. It always has to be full up for passthrough.
If you chose passthrough in any App you'll loose sound output for all other apps.
That's why it is offered in ATV. But with a normal mac, you want a lot of different Apps to work at the same time, even if you have QT open and watch a movie with 5.1.
Apps like Plex don't have to deal with this. They kind of "Highjack" the whole system for their tasks.
I'm very confident that Apple handles all these problems with a new Quicktime in SnowLeopard.
ps
I've written this in the "iTunes for Windows" category already.
Message was edited by: cigame2
Message was edited by: cigame2
