> I did some more digging since you peaked my curiosity.

Yes... Isn't it fun!

> An FPGA isn't going to cut it either because AC3 uses 'perceptual coding',
> AKA Heavy duty DSP.

I know, That's why I'm talking about multiple PIC's atleast one for each
stream in addition to one or two for combining the data and some external
hardware.

> You are starting out with 6 channels of PCM data and have to compress
> them into the lower bit rate of a 5.1 stream. NOT an easy process,
> which is probably why you do not see 5.1 sound in games. In theory
> you could write a sound device shim that would take the AC97/99 data
> stream coming from the game, and reformat it into something you could
> pump out the SPDIF pin. This would be sound card independent if the
> card used WDM drivers and had the required resources (logical SPDIF
'pin').
> http://www.intelligraphics.com/articles/WDMaudiodesign_article.html

If you set the soundcard to "digital out only" you will have 3 uncompressed
stereo PCM streams of 48k, 16 bit.
Theese can be split into whatever is necessary (not necessary) for
compression of each element.

> The key thought here is that most DD & DTS formats are 'compressed' so
> you'll have to do a LOT of work to get the PCM data stream to fit, only to
> decomress the data 15' away in the DTS decoder. It's really just a LOT
> simpler to run a fat multiconductor RCA cable to your amp.

I urge you to take a test with simple stereo out.
Test with a good amp and the normal cable you would use from comp to amp.
Listen to the music and pay especially close attention to the higher and
lower portions of the spectrum.
Now, take the same song and send it to your amp with a coaxial or optical
cable carrying a digital, uncompressed stream.  Listen to the difference.
-> Now, you won't question me in wanting digital transfer from comp to amp.

    Kyrre

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