So, here's the issue:

I have a powermac G5 with an optical digital audio output port (SPDIF port). I would like to be able to output 5.1 audio through this into my surround decoder. Apple's DVD player does this nicely with DVDs, but is there a way to play back multichannel audio that's not on a DVD? Quicktime seems unwilling to do it. I tried a 5 channel .WAV file, but I only got stereo out. Quicktime won't even open an ac3 file. (BTW, what's the proper extension for ac3?) I tired VLC and also no luck.

Any ideas?