What setting do I need to use to transcode a MKV with an AC3 5.1 soundtrace to a 360 and maintain 5.1 audio, and is it possible to transcode an MKV with DTS and maintain the 6 channels.

I can transcode MKV files which have AC3 5.1 soundtrack, but I only get a 2.0 soundtrack on the 360.

Regards
Rich