Use of the card under Vis

Question

I've been doing a lot of reading about the changes that were made to how audio is processed under Vista as opposed to earlier versions of Windows and from what I understand, all audio decoding is done via software and the sound card does, well, essentially nothing as far as audio processing is concerned.
I get audio from my sound card to speakers using a coaxial SPDIF connector and so, again, all decoding is done externally through the use of the receiver for my speakers. Where in all this does the sound card come in and what advantage would a Creative card such as the Audigy2 ZS Platinum which I am using, (if any) have over my cheap on-board Realtek AC97' sound card? As far as I can tell, the card does no processing whatsoever and digital data is digital data; you can't screw it up.Message Edited by mrps2man on 04-3-200707:2 AM

Answer 1

Ah okay, well presumably the sound card could still apply affects to the digital stream, although it may have to convert from digital to analog, apply the effects in the analog domain, and then reconvert back to digital before forward it to your receiver. Let me give a practical example.
The thing is it's complicated. Let me give a practical example. Suppose you start with an MP3 audio file played via say ITunes. ITunes may do it's own MP3 stream parsing, and analog audio reconstruction, applying it's own filters, equalizers, etc. This is all done in software and not new to Vista. But at some point ITunes has to create a new digital stream in a format that is compatible with the Windows APIs. No sound card has been involved so far.
Where would the sound card come into play then? Well if you have an analog receiver, then of course the sound card has to convert the digital stream received Windows APIs to analog, and out it's analog am
ps.
What about if you have Dolby Digital or DTS receiver? Then the sound card, or software (running either in the driver or via some accelerator like a processor on the sound card) has to real time convert the multiple digital streams received via the Windows APIs into a Dolby Digital or DTS digital stream.
The point is there are many conversions of the digital data, but at some point the sound card driver receives these digital streams from all channels. At this point the sound card driver or driver+hardware can apply it's own effects (like the crystalizer and cmss) or convert multiple channels into 2 (e.g., using a head related transfer function, aka HRTF, to simulate multiple channels with 2 or 3), equalize, and after all of that, either send the digital data to it's onboard DACs or re-digitize the modified data (e.g., into a Dolby Digital stream, DTS stream etc.).
Things are more complicated still though when it comes to the DRE stuff. It's not clear to me if a sound card driver is allowed to modified the data, or record it, but that's by agreement, there is no technical reason why the sound card couldn't, just they won't in order to be DRE compliant.
Anyway I realize that's a long and obstuse answer, but the bottom line is that digital data in a computer already typically goes through various digital to analog and analog to digital conversions in software, or re-digitization in software. The sound card is just the final step along the way to your analog speakers, or if you have a receiver that has DTS or Dolby Decoding, the sound card can re-digitize in those formats after applying it's own effects.