MKV Convert Noob Question

[bumbo]

Hi guys

I've searched but can't see an answer/reason to this so apologies if it's there..

I am trying to export an MKV to MP4/M4V in QT Pro.

The video is fine (left as Pass-through) but the audio only shows AAC-LC and stereo but the file has a 5.1 AC3 audio track.

I'd rather not lose the surround sound but also don't want to lose the speed of exporting through QT

I've tried extracting the AC3 and then re-inserting it to the new MP4 and M4V but neither will save - it forces me to save as a MOV.

Is there a way around this??

BTW I have handbrake and VisualHub also.

Thanks