[LAU] Raspberry Pi and real-time, low-latency audio

[Jeremy Jongepier]

On 04/18/2013 02:59 PM, Nicola wrote:
> Hi, thanks for sharing.
> The idea is simply brilliant and it works quite smoothly following the
> wiki[1] (Thanks again Jeremy!), i've got a UA25EX[2] and a Terratec
> Aureon dual-usb[3].

Hi Nicola,

You're welcome! To me the RPi is just another device running Linux. And 
if it runs Linux it can run JACK and some of my favorite software. I'm 
sometimes baffled by the immense detour people are taking just to get 8 
note polyphony out of the RPi for instance. Or using some real-time 
effects. Or building a drum sequencer. All the stuff is already there! 
But no, apparently they prefer to reinvent the wheel.

> Just a couple of things i noticed:
>
> 1)Using the nexus7 power adaptor everything works fine, it's a 5w 2.0A.
> 2)if you run jack with following command as the wiki suggested "jackd
> -P70 -p16 -t2000 -dalsa -dhw:UA25 -p128 -n3 -r44100 -s" make sure to add
> the background "&" at the end of the line, without this the sound was
> lousy and glitchy, at least for my UA25EX.

So if you don't run it in the background sound is lousy and glitchy? 
That's weird as it shouldn't make a difference? I did find that raising 
JACK's rtprio even more (I'm now using 84) decreases the number of glitches.

> 3)Using this usb wireless adapter[4], so in a headless fashion, i had
> many jack's disconnection no matter what frames/periods i choose.Any
> suggestion to improve it?

At the moment, no. I don't have any experience with WiFi dongles and the 
RPi. I should give it a try.

> 4)I really love the tubescreamer in guitarix, it sounds GREAT!

It sure does. I for one can't do without the Treble Booster though :)

> 5)I've got my PI amp now saved in a separate sd card, now i'm able to
> switch my pi from a server into an amp by just replacing the sd card,
> how lovely it is!?
>
> p.s. I was thinking to install Ubuntu on my nexus7 to control Guitarix
> (headless through ssh -X) with the touch screen!!!
>

Great idea! I've got a bricked tablet lying around too and supposedly it 
can run Ubuntu too. Keep us posted on anything that comes out of this!

Jeremy

> [1]http://wiki.linuxaudio.org/wiki/raspberrypi
> [2]http://www.rolandus.com/products/details/970
> [3]http://www.amazon.co.uk/Terratec-Aureon-Dual-USB-Notebook/dp/B000WL23KC/ref=sr_1_1?ie=UTF8&qid=1366289839&sr=8-1&keywords=terratec+aureon+dual+usb
>
> [4]http://www.edimax.co.uk/en/produce_detail.php?pd_id=328&pl1_id=1&pl2_id=44
>
>
> Nicola