AC3 Divx/Xvid passthrough

[syphon00]

here's my setup
I've got a Turtle Beach Riviera with optical out connected to a Denon reciever
I'm using WinDVD6 to play my AC3 Xvid files
I've WinDVD6 set to SPDIF out, and on DVD's it's working fine I can see that my reciever is doing all the decoding
only on these Divx/Xvid files they're not coming as Dolby Digital
seems like the decoding is still being done in the software
and I know these are correctly encoded AC3's since I've tried them on my standalone Divx player and they output in Dolby Digital
the question is, what configuration changes should I make in order to allow the AC3 passthrough to my reciever

maybe I need to use a different software?

Thanks

[tr6scott]

I just bought the Riviera sound card for the same hookup, and have found the same results. I am using PowerDVD 4 which came with my Sony DVD-RW. If I play a DVD, I get the pass through to work, and the reciver, (Sony) does the decode. If I use a divx file as the source, No pass though.... Frusturating, was doing a google, for a solution, and ran across your post. There is something called meedio, http://meedio.com/partners/ that may allow you to customize and control the split A/V and decode. Still searching, will post back if I find a solution.

[celtic_druid]

Try using AC3Filter or ffdshow. They can also both do AC3 encoding for passing other non AC3 sources.