[PD] wierd feedback popping with pd/freebob/jack/rt

Ken Restivo ken at restivo.org
Tue May 20 23:29:50 CEST 2008

> 2008/5/20 Rich E <reakinator at gmail.com>:
> > Currently, Pd-0.40.3-extended from the autobuiilds.  While I think this is
> > occurring on every version on Pd I have tried since I installed Hardy (which
> > is alot), I should do some testing to verify that.
> >
> > Another thing; opening Audacity only cures things for a bit, until I do
> > something like open another patch in pd.  Then, the glitch happens again, I
> > restart audacity, and it goes away.
> >
> > I'll try some testing on 0.39 - .41 vanilla when I have a moment.
> >

IIRC, Ubuntu "RT" kernel is not actually Real Time (i.e. with Ingo patches), just a "desktop RT" which is not very useful for audio and certainly not enough for JACK apps of any heft.

The "pops/clicks" phenomenon you are noticing that gets resolved by starting or killing another JACK app, is something I've experienced before. It happens when some app gets an Xrun or otherwise can't process audio in time. From that point forward it "clicks" and, in my experience, distorts as well with some bitcrushing-style aliasing distortion. When you start or stop any JACK app, the entire JACK graph structure gets re-ordered (this isn't true with jackdmp, just with single-processor JACK), and that causes the misbehaving app to "start from scratch" somewhat and get its audio organized properly.

I'd suggest 64Studio, Musix, Pure::Dyne, or some other distro that has the really serious RT set up with the Ingo patches. With one of those distros, everything should run very well on a machine of any decent heft.


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