OK, after my post about SP/DIF I got afew mails where I was asked to =
share what I know about the SP/DIF and Creative systems.
I will now spill my guts :-)

Most of my knowledge on the SP/DIF system is actually based on the =
following links, so I will NOT take credit for this.

http://www.epanorama.net/documents/audio/spdif.html
Very good info on the SP/DIF codec and AES/EBU.  There are altso =
numerous converter circuits there.  I am working on a modification of =
some of theese so that I can do TTL or 0.5Vptp signals on the same input =
and convert to TTL and Optical...
This page has oltso very good info on the format on the SP/DIF data.  =
Here you can learn how to manipulate the stream to conform with or break =
copyright if you read closely.  All specs are there.  It altso states =
the possibility for multichannel beyond stereo.  (Wich is why I am =
thinking about a four-channel version/muxer...)

http://www.cl.cam.ac.uk/Research/SRG/HAN/docs/sp-dif.txt
More info on the SP/DIF.  All by DJ Greaves.  More of a history lesson =
:-)

http://members.tripod.com/~Psych/md-cdrom.html
Even more info.  This time with more circuits...  Using a CD-ROMs SP/Dif =
etc...
CD-rom tom minidisc is altso covered :-)

In addition to this I have found some stuff on my own about the SBs.  I =
have altso talked to Creative Tech personell and designers, but they are =
very sparse with info.

What I do know:

The Creative SB Live 1024 has four digital output channels onboard.  =
Theese are situated in a yellow 4 channel mini-jack on the back of the =
card.  The reason for the four channels is that there are ground =
reference and power in this plug.  This is altso why your computer may =
hang if you connect a plug into this socket while running.  You actually =
short some of the power in the computer before the card realizes what is =
happening and disables it.  This power makes it possible for the =
"Digital Output Module" to function and convert the two digital stereo =
channels to Toslink optical.
The bad thing is that theese two channels can't be used by a normal =
decoder as fourpoint sorround since they are two seperate stereo =
signals.  Unless you have some Digital desktop theatre wich is designet =
for this specifig purpose. Recieving two digital streams one for the =
front and one for the back speakers, and then amplifying and outputting =
to speakers.  Other recievers/amplifiers want this signal in any of the =
following: (All on one digital transmission channel)

1) Mono digital
2) Stereo Digital in PCM/RAW
3) Multichannel (4point) can possibly be PCM/RAW
4) AC3 multi/single channel streams
5) DTS or similar streams...

All on one channel...  There may be others, but who can know everything =
?

The Soundblaster Live 5.1 is different.  They have removed the power on =
the yellow connector.  Now the card wont hang your system if you connect =
something while computer is runnjng.  But, alas now you can't use the =
Digital Output Module either!
The new card has an extra digital stereo output.  This is for the center =
and sub channels.
All SB digital outputs are TTL level, so interfacing a PIC would be no =
challenge.  Altso most recievers accept this TTL level SP/DIF with no =
mucking about :-)

Altso: There are ways to enable extra line inputs and SP/DIF digital =
inputs and outputs on both Live cards as well as the SB128.  This is =
seamingly done by interfacing/connecting systems and jumpers/resistors =
to the internal pin header on the boards.  The drivers should normally =
detect theese "enhancements" at bootup.

The last thing I will add it that NO, there is NO way of getting the =
soundcard to output a multichannel (more that 2) digital stream to a =
reciever, unless you are playing some AC3 or multichannel source with =
special software.  (Like a AC3 output compatible software DVD-player)  =
Creative was simply to cheap to include hardware that would do this =
compression/encoding on the fly.  You can however do a software =
recompression of up to six channels using comercial software and then =
outputting on the primary/front speakers digital output.  This would be =
like playing a DVD or thelike.

What I am trying to find out is if there is a way to let a (perhaps =
top-line) PIC do some multiplexing/coding to atleast get four channels =
into a PCM or similar stream...

Any extra info or reports on errors are greatly apprechiated!

(Whew! that was alot of typing!)

    KreAture

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