Erik,

32 bit fixed point - a possibility
16.16 - where the decimal point will be is completely arbitrary. 24.8 or 
somewhere in between is just as easy to do. all depends on what is needed

however for mixing:

add first then divide
 n-1 adds
 1 divide

divide first then add
 n-1 adds
 n divides

even if divide = add for processing time
 2n-1 vs n


John,

100m is the limit for ethernet.  I don't know of much that could use that 
either.  (maybe a concert in a football stadium? The longest run I've seen was 
about 27m in a church.  I was on the camcorder.  I didn't know cheap mic cables 
could pick up AM radio ;)  But I digress.  Others suggested eth and I ran with 
it because I am familiar with it and I thought it would give a good baseline.   
I would of course take a better standard with a shorter range in a heartbeat.

about AES50 - from aes.org
 CAT5 cable - cheaper than CAT6
 100m max :P
 full duplex clock over the same cable - bonus
 full duplex audio - check
 5Mb/s full duplex data channel - for control sideband - check
 point to point bus - OK
 fully developed audio protocol - very good

google search indicates 48 channels (is that 48 each way?  48 in + 48 out = 96 
- more than plenty)
this would work for the internal interconnect
maybe have 2 external ports on the card? (one to the patch box, one to the 
control box?)

I think we have a winner

this, of course, does not rule out optical connectors in addition

as far as multiple cards, I don't see much use either, but I'm sure somebody 
will come up with a need, and if it doesn't really cost extra to have that, why 
not?

live vs real-time
 my terminology may be off
 what you were describing, I would classify as 'live' - your output has to sync 
with the real world, not just play without skip

500ms delay playback - sorry, this was a tounge in cheek example.  what I meant 
was, for that sort of service you can buffer the snot out of it so there is no 
skipping even if the host computer is very busy.

for what you are talking about, I would consider 2ms delay to be excessive.  
Prebuffering sound effects is actually why I suggested 32MB+ ram.  This would 
allow a large number of samples to be preloaded (MIDI or video games can use 
>100 if it is available) for instant playback.  Repeat or overlapping playback 
of the same effect is a must for those services as well.  5 1 second buffers?  
Consider it covered :)


Jack,

MIL spec connectors could be doable - depends on cost/availability.  If someone 
is willing to pay for a run with such, I'm sure OpenGraphics could arrange for 
whatever connectors they want :)

When I say PnP, I mean anything you plug in should be immediately recognized 
and available,  without needing any device specific drivers or special 
configuration beyond backplane assignment.  Having serial numbers on units so 
preset configurations can be loaded no matter where they are connected would 
need to be supported as well.

Since this thing is a computer in its own right, stand alone units could be 
done in the future.  And, as Dieter said, the computer doesn't have to be in 
the control room, or on stage.  In the same room as the amps, or next door (so 
those cables are SHORT) would be best.  Remote GUI setup could also be arranged 
several different ways.

Flexible is the watchword :)


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