I really needed help with JACK - Linux-audio-user

27 Jan 2013

This is kind of OT, but Bob's problems with jack inspired me to share my 
experience:

I recently bought a Toshiba Sattelite p 850 and installed Ubuntu Studio 
12.10. It's slick and mostly just minor tweaks needed to take care of my 
office needs.

Then onto musical needs; connect Roland Edirol UA-25EX and start Ardour, 
which exits unable to start jack. Run qjackctl, try different settings. 
Finally getting it to run and able to start Ardour I completely fail to 
record anything. More fiddling with settings. Jack hangs on exit. Ardour 
crashes. There is no sound from gmusicbrowser or internet either. Hair 
is pulled out. Starting over.

And everything seems to work, I say "testing, testing" to my mike and 
hit a few keys on my synth, meters showing input - but it turns out what 
is actually working is the internal mike. No recording through USB...

I search forums and pull out more hair, to no avail. I randomly change 
settings, and suddenly!

So here's my recipe to have it all work _out of the box_:

1. connect UA-25EX
2. power up Ubuntu Studio
3. Start jack. Settings:

Realtime box: checked
Priority: DEFAULT
Frames/period: 128 (higher number, more latency. With this I have 8ms)
Sample Rate: 48000 (same as USB interface UA-25EX)
Periods/buffer: 3
Dither: None
Audio: Duplex
Interface: hw:1 (this will possibly be different on another machine)
Input device: default
Output device: default
Channels I/O: default
Latency I/O: default

4. Open sound settings. Disable built-in-audio and set jack sink as fallback
5. Run Ardour and record whatever from wherever! All playback going 
through USB interface.

So in the end it was quite simple and working out of the box, it was 
just bloody unintuitive to figure out. And mind you, I still get in 
trouble if I run sound through pulse before starting jack.

But all in all I like my Ubuntu Studio better and better!

Hope this will be helpful for someone.

Alf