Decode AC3 in software in real-time?

Hi everyone. This seems like the best forum on the net to ask this question, so here goes:

First, the hardware. I just got myself a new sound card for my compy. It is a Diamond Xtreme Sound 7.1. More information (what little there is) can be found on Diamond's site at diamondmm.com. The card has S/PDIF in and out. The speakers hooked up to it are an old-and-trusty set of Klipsch Pro-Media 4.1's. The audio card downmixes all sound it outputs into a "virtual" 7.1 environment. I also own an Xbox 360 and a cable mount for it which houses an optical S/PDIF out.

So my first thought when I got the thing home was: "Hey! I could have fake surround sound out of my 360 with this card!" Unfortunately not. The 360 is outputting a Dolby Digital AC3 signal and the sound card does not decode it.

So my question is this: Is there a software solution that will decode the AC3 signal coming off of the 360 and downmix it to the speakers hooked up to my PC?

Any help would be appreciated!

I actually found a solution for this, but thanks for the link! I'm always up to looking at more codec packs.

If anyone is interested, I'll be posting an explaination on how I did this on my website soon. It's 2assholes.blogspot.com