Multi-Channel output and Audio Midi
Ok, there are a lot of people confused about surround sound and digital out. In Audio Midi, Digital Output will ALWAYS show 2ch-Xbit Integer. This is normal. As I stated on page 9, OS X always outputs in stereo. It's just how Macs work. No real Mac has ever offered multi channel analogue output (native). Any source besides movies with encoded audio (whether it's from iTunes or an iMovie/FCP project) will always be 2-ch stereo. Since the G4s, Apple has included digital out. Yay! So, for compatibility reasons, everything is in 2-ch stereo. Programs like VLC and iTunes will automatically switch to Encoded bitstream when Digital out is set to output and connected to a receiver via TosLink. You need not worry. DD and DTS will be sent via Bitstream and will be decoded correctly.
HOWEVER, a lesson (cliff notes) on multi-channel and Bitstream. 2ch-24bit is technically multi-channel. Bitstream/PCM will always be sent to the receiver in this way. When I play a DTS encoded movie and check the signal info on my receiver, it shows 2ch-24bit Bitstream. Full DTS! When I stream a movie via PS3 Media Server to my PS3, and check out the info it says 2ch-24bit. Again, full DTS.
To sum things up, please don't worry (or freak out). Test things out for yourself. I have used many ALC chipsets, and never experienced Multi-channel out problems via TosLink, regardless what Audio Midi says.
**Note: In my experience, iTunes can be real pissy when it comes to Encoded multi-channel out while playing movies rented/purchased from the iTunes store. You have to set EQ to off, take off sound check and the sound enhancer, as well as SRS iWow in order to have DD/DTS work. Otherwise you will get nothing but static. Sometimes, you will get static regardless. If you are savvy enough to get rid of the DRM from the movie, and play through VLC, DD/DTS work just fine. On a real Mac, this isn't a problem whatsoever. My iMac can play multichannel sources, whether it's through VLC or iTunes. Even HD multichannel audio FLAC/AIFF/Wave (SACD and whatnot) work great; It is a pain in the butt on a Hachintosh.