Im almost positive that nvidia will not release a driver that will allow for any sampleing rate other than 48khz on the nforce boards. I have an nforce with a soundstorm and after much probing and poking around in the nvidia driver, I realized its the same "cursed" (it actually says that in the code) driver as i810_audio. Apparenlty we're using the AC97 chip instead of the MPT which does all of the fun 6 channel audio stuff. They will not release the code or white papers. I threw an SBLive in my box just so I could get GOOD audio, let alone anything other than 48khz; something with the ac97 chip causes buzzing in my speakers and the same goes for my laptop which uses the same chip. There is currently a petition at www.nforcershq.com
(look in the forums, then linux) to get nvidia to do something, but they probably will not.
Here's my theory -
Dolby Digital is patented (obviously) and therefore not open source. I have a feeling that nvidia and intel are simply using the DSP to do all of the 6 channel dolby decoding which means that the assembly code that sets up the DSP would probably have to be binary only since open source is out of the question. A binary only driver would probably need to be licensed which, obviously, wont happen. We can get a SPIDF out if we prod enough, providing the spidf doesnt go anywhere near the DSP.
Home theater and good quality audio just wont happen unless the manufacturers use REAL hardware decoding and not using programmable DSPs which load their routines via the OS. Linux is at a downfall here which really sucks considering im a Linux person and an audio engineer. Im stuck rebooting forever.
BTW, there is 1 card that does dolby prologic in linux, but i believe it only worked with an older 2.4 kernel and the control app isnt really supported anymore.