Digital Mixing.

[Batz Goodfortune]

On Sat, 3 Jun 1995, Rick Stevenson wrote:
> > I belive there are plenty of other manufactures of digital audio chips
> > besides Crystal Semiconductors but I've only been able to chase down
> > Crystal data. Christal make some hoopy chips but none realy suited to my
> > needs.
> 
> Sorry, I can't answer your questions, but I have one of my own...
> Does someone in Oz distribute Crystal stuff?

Yea I can get Crystal stuff locally ok even if at a somewhat elevated price.
Crystal make some useful S/PDIF-AES/EBU converters and CODECS etc. Even a
curious S/PDIF / D-A combo with intergrated DSP, but nothing that will
allow combining of multiple I2S Streems. Thats the serial audio bus used
to communicate digital audio between chips etc. (IC Interstage Sound). You
could do it with a bunch of synchronised shift registers but typicaly
these are only 8 bits wide. To do one stereo I2S streem you would need up
to 6 of them. Possible but messy. If you then tallied up the number
required for multiple streems and the shrapnel to glue it all together it
would become very messy indeed. Even Crystal's GS synth evaluation board
uses 3 shift registers to talk between the Synth-Engine and the DSP FX
processor. But that's quite simple because it only has to send 1 streem
synchronusly. 

How must they do it in something like A Yamaha DMP7 or the new DMP9-16.
Where, besides having the internal digital audio busses, there are 2
asynchronus S/PDIF streems comng in from the outside world? Of course
Yamaha being the beast that it is probably have a propriatory chip to do
this. 

There must be a chip(set) or DSP ready configured to handle the situation
out there somewhere. There are lots of applications for such in the
broadcast industry. I recently saw a digital satilite system which did
just this. It was in a single U 19" rack and could combine 8 S/PDIF
streems (Well AES/EBU as it happend but it's basically the same thing)
There was no chance to pop the lid and have a look inside but they managed
this in a very small space. 

It must have had at least 8 Digital Audio receiver chips @ 28 pins each +
what ever DSP hardware was involved in processing. The case would have
only been 6 to 8 inches deep. If it had that many shift registers in it,
the case would have been at least twice as big. 

I'm getting kind of desperate to find an effective and (relitively) simple
way of doing this. And I've been searching for a solution for a while now. 
I was led to belive that Crystal actually made a chip to do this but
apparently not. Crystal make some nice gear though.

Be chill.

    _ __        _                  Batz J Goodfortune          
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 batzman at apanix.apana.org,au      voice +618 356 4081