I've got a problem with my new build. I've got a gigabyte GA-P35-DS3L board paired with an E4500 processor. I opted to go with an ATI 3850 card because I still hold hope that I'll try and game with it someday(starcraft 2?).
I have the computer hooked up via SPDIF from the motherboard to my receiver. Everything seems to be defaulting to 2channel output which is being decoded as prologic at my receiver. I have no idea if this is being caused by the 3850 or just some other nuisance problem of my motherboard. I initially ran into the problem with XP while I was waiting to get my copy of Vista, and then last night installed Vista to have essentially the same problem.
Here's where things get a little murky. The realtek software control app allows me to test DTS and DD output, and that works great. I installed powerDVD and did a quick test and was able to get DD output to my receiver. When I try to do anything in Sage, its always pro logic(even on OTA HD). I've tried all the available audio decoders without success. As a quick test I tried using the Fusion HDTV app, and initially it was prologic as well, but I was able to for passthrough SPDIF in the configuration and then it came out as DD.
I haven't found much by searching, but some people recommended snagging AC3filter and a smaller app called SPDIFer. Neither seemed to help. The computer seems to default to pro logic unless forced not to. I'm new to vista and not quite sure how to tackle this problem, although given that I am able to get DD and DTS output in some cases, I think its a decoder priority problem, but I just don't know where access those settings and what to change them to.