[LAU] JACK on Pi... almost working

[Ken Restivo]

On Sat, Jul 26, 2014 at 08:44:30PM +0200, Jeremy Jongepier wrote:
> On 07/26/2014 07:42 PM, Ken Restivo wrote:
> > I was playing around with trying to use a Pi as a synth.
> > 
> > So far so good except for two problems:
> > 
> > 1) I've run into this:
> > 	http://comments.gmane.org/gmane.comp.audio.jackit/26263
> > 	
> >     But I'm already using  jackd2_1.9.8~dfsg.4+20120529git007cdc37-5+fixed1~raspbian1_armhf.deb
> >     which supposedly has Dbus removed/excised/banished/purged/kicked-to-the-curb.
> >     And yet, no dice, same error. Haven't had time to investigate it yet.
> >     I went back to jackd1 (wow, it's like it's 2007 all over again).
> 
> Hello Ken,
> 
> What does 'apt-cache policy jackd2' say? It seems like you were not
> using my package. Jack1 might be a better choice on the RPi anyway as it
> has a slightly smaller memory footprint. And yes, this matters on the
> RPi since it has only 512M RAM.

I'll have to look again, but I'm pretty sure that it was the autostatic packge.

> 
> > 
> > 2) The sound coming out of either the built-in audio or an external C-Media USB interface
> >    is cracking and nasty, with obvious aliasing distortion. Any ideas why? I've tried
> >    44.1k and 48k. No xruns tho, which is nice, at 44100/512/3 using jackd1 and fluidsynth. 
> > 
> 
> I've used it with a C-Media USB interface too and it worked without
> crackling. Is there anything else connected to the USB ports? Are you
> running the RPi with or without X? Probably without otherwise you
> wouldn't run into the D-Bus issue. What kind of power adapter are you
> using? Fluidsynth shouldn't be an issue, did you also try other apps
> like amsynth? Do you also get crackling then?
>

No X, all unnecessary services disabled as suggested in your excellent guide,
and a power adapter that can do 2A. Haven't tried amsynth, but mplayer
has no problem, though only using raw ALSA, not JACK. I suppose I
could try mplayer through jack.

> > I've got it overclocked to 1Ghz, all is well with that (ran the self-test), and
> > using the performance guv'na.
> >
> 
> I'm not going higher than 950Mhz, I got a lot of SD corruption issues
> when trying to go higher than that.
>

I ran the corruption test, it passed. 


> > I haven't tried with my FastTrack Pro yet because the Pi can't power it at the
> > same time as a MIDI keyboard, and a working power cube for the keyboard has gone missing.
> > 
> 
> Did you try backfeeding the RPi via a powered USB hub?
>

I'm not sure what this means.

> > The crackling/aliased sound is the big stumbling block though. Any ideas?
> > 

I dunno, I kind of gave up on the project. Maybe I'll try again with
a BeagleBone Black if I really wanted it to work. A friend gave me the
run-down on why Raspberries are crappy, and couldn't argue. I've done
quite a bit of work with BeagleBone's in the past (pre-Black days) and found
them much better engineered-- real development boards.

The dream 7 years ago was to have a portable, battery-powered, rock-solid,
headless Linux synth that could be controlled with a keytar-configured
USB controller for street busking and casual gigs. I'm not gigging anymore
and can't imagine wanting to, so it's kind of moot now. And yet, having
that project still un-completed-- but so close to being possible--
continues to nag at me.

-ken