Re: Multiplexing and mixing

On Sat, 27 Jun 2009 13:44:25 -0700, Bob.Jones5400@xxxxxxxxx wrote:

I want to design a system, unless something similar exists, that
multiplexes digital audio signals but also allow for mixing of those
signals in arbitrary ways. This should be relatively cheap because I
want to use a lot of them.

The signal is arranged Sample1_audio1, sample1_audio2, etc...

Where a sample is n bits with some way to determine when a new sample
happens(I guess another line to signal the new bit or a serial like
protocol with start and stop after a "frame").

In any case it should not be difficult to "mix" to signals. I would just
extract a sample, multiply it by a the "mix" value, and add it to a some
a buffer.

But how difficult will this be to implement using discrete components
(IC's but not fpga's or uP's)? The number of signals is fixed around
20(the more the better). The audio rate is ~200khz @ 24-bit. 200khz is
over sampling so please don't whine about the human ear not being able
to hear above 20khz. This requires about 5Mhz per audio signal.

Once the signal's are mixed the new mixed signal is added to a slot in
the "bus"(it will replace one of the slots as designated by the user).

If this is easily implementable in an fgpa and doing it "discretely" is
just as costly then I suppose it is the better option. I'm just not
quite sure...

Onto what sort of a channel do you wish to multiplex these signals?
Something like USB, or the now-obsolete IEEE-1394/Firewire, to go from a
box to a PC? Something like RocketIO to go from one chip to another on a
board, or between two closely-spaced boards inside a box? A
transcontinental cable?

You're talking about enough logic content that doing it with discretes
would be huge, troublesome and expensive; depending on the nature of your
channel and what you _really_ want to accomplish this would be a routine
to moderately difficult job using FPGAs or DSPs.

--
www.wescottdesign.com
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