[PD] Multi-input USB audio into Raspberry Pi

[Brian Fay]

I don't want to discourage you, but from my experience there's definitely
some things to be wary of with the Raspberry Pi. For example, a lot of
people have reported needing to use USB 2.0 devices in USB 1.1 mode. I
don't know if this would necessarily hinder the functionality of the
device, but it seems like it could be a nuisance.

Personally, I've been using an interface with a single stereo input and
output (Behringer UCG102) for my guitar. Performance for that device has
been fairly satisfactory, but there are some problems I can't seem to
resolve...

I get buffer xruns every ten seconds or so when running PD, even in -nogui
mode with realtime priorities. This sounds like a little "pop," a one
sample impulse, and while it's not unplayable, it is annoying. I am running
at a pretty low latency (~8ms, which is awesome), but even raising the
latency a little and messing around with the signal vector size doesn't
seem to help stop the popping.

Also, while it's not super important for my guitar processing, I've been
unable to run duplex audio at a samplerate higher than 32kHz. It seems that
this is related to an issue in newer versions of the kernel (there's an
issue posted here: https://github.com/raspberrypi/firmware/issues/197). I
don't know anything about Operating System code, so I have no idea if this
could be addressed somehow.

So while I can't say that multi-channel input and output won't work, I will
say that even stereo I/O is a little broken.

I wonder if the BeagleBone xM would be better for this project? It is a bit
pricier, but it seems like Stanford CCRMA students have had some success
with it (more than the Pi, anyway)
Check out this link for examples of that:
https://ccrma.stanford.edu/~eberdahl/satellite/

Good luck,

Brian


On Thu, Jan 23, 2014 at 7:31 PM, Chris McCormick <chris at mccormick.cx> wrote:

> Hey Jaime,
>
> On 24/01/14 01:48, Jaime E Oliver wrote:
> > there was a thread on this just a while back and someone reported
> multiple inputs, I cannot find it right now, but it;s there!
>
> I spent a fair bit of time reading back through the archives and various
> other sources yesterday and I did see mention of someone running four
> inputs but a later post seemed to contradict what they'd said, and I
> couldn't find anything on pd-list about that in particular.
>
> Would love to be wrong about that of course!
>
> In any case, I will report back here if successful.
>
> Cheers,
>
> Chris.
>
> --
> http://mccormick.cx/
>
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