[PD-dev] audioindev with several devices

[Jason Plumb]

David Merrill wrote:
 > yes, I've heard that alsa has the ability to create a single, 
"virtual > sound card" from multiple individual cards, but so far I 
haven't been
 > able to make this work - I'm interested though, to hear from anyone
 > who has done it. also heard a rumor that new versions of jack may be
 > able to connect to multiple cards at the same time - again, I don't
 > have specific info, but am curious to hear if anyone has done it.

David,

In my audiopint setup, I'm using 4 USB iMics in a cheapo USB 1.1 hub.  I 
use all 4 stero inputs and the one single stereo output of the first 
iMic.  I haven't confirmed it, but I'm confident that fully duplexed 
stereo on all 4 devices would go over the theoretical 1.1 bandwidth (my 
setup does not).

I multiplex the 4 cards into a single virtual card using the attached 
asoundrc (which should be named as ~/.asoundrc).

I am successfully using this 8-in-2-out virtual card with jackd 0.103.0 
(realtime) and pd 0.40-2 (realtime).  Jackd > 0.102.20 is required to 
pick up MMAP_COMPLEX, which allows memory mapping multiple multiplexed 
cards (??).  My jackd usage is:

    jackd --realtime -d alsa -C capture8 -P iMic1 -p64 -n2

and then I make sure I start pd with -jack -inchannels 8 -outchannels 2
(and other less relevant params).  I'm pretty sure the clocks aren't 
exactly synchronized (I would appreciate confirmation or refutation), 
but it hasn't really caused me any pain yet, even though I should likely 
back -p64 down to -p128.

I'm pretty sure I had limited success getting pd to work in alsa mode 
with the given .asoundrc...but to be honest, my focus was on jack first.

-jason
http://noisybox.net
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