[PD-dev] audioindev with several devices

David Merrill dmerrill at media.mit.edu
Tue Sep 18 15:25:09 CEST 2007


thanks Jason - this sounds promising, and I'll give it a try on my system.
-Dave

On 9/18/07, Jason Plumb <jason at noisybox.net> wrote:
>
> 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
>
>
> pcm.iMic1 {
>         type hw
>         card 0
> }
> ctl.iMic1 {
>         type hw;
>         card 0;
> }
>
> pcm.iMic2 {
>         type hw
>         card 1
> }
>
> pcm.iMic3 {
>         type hw
>         card 2
> }
>
> pcm.iMic4 {
>         type hw
>         card 3
> }
>
> pcm.capture8 {
>         type multi;
>         slaves.a.pcm hw:0
>         slaves.a.channels 2;
>         slaves.b.pcm hw:1
>         slaves.b.channels 2;
>         slaves.c.pcm hw:2
>         slaves.c.channels 2;
>         slaves.d.pcm hw:3
>         slaves.d.channels 2;
>
>         bindings.0.slave a;
>         bindings.0.channel 0;
>         bindings.1.slave a;
>         bindings.1.channel 1;
>
>         bindings.2.slave b;
>         bindings.2.channel 0;
>         bindings.3.slave b;
>         bindings.3.channel 1;
>
>         bindings.4.slave c;
>         bindings.4.channel 0;
>         bindings.5.slave c;
>         bindings.5.channel 1;
>
>         bindings.6.slave d;
>         bindings.6.channel 0;
>         bindings.7.slave d;
>         bindings.7.channel 1;
>
> }
>
> ctl.capture8 {
>         type hw;
>         card 0;
> }
>
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>
>


-- 
MIT Media Lab
dmerrill at media.mit.edu
http://web.media.mit.edu/~dmerrill/
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