[PD] wierd feedback popping with pd/freebob/jack/rt
ken at restivo.org
Thu May 22 00:20:26 CEST 2008
On Wed, May 21, 2008 at 02:23:20PM -0700, Rich E wrote:
> > 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.
> Where are you getting this info from? This is not what I have read, but
> maybe I am missing something somewhere. I thought that the Ubuntu kernel
> packagers recently switched to using full realtime preemption... I find this
My info is from having installed Ubuntu and used it... but that was a few years ago. Glad they're using Ingo's patches now.
> in the package description of linux-image-2.6.22-14-rt :
> Ingo Molnar's full real time preemption patch (126.96.36.199-rt9)
> Here is the output of uname -a:
> Linux pal 2.6.22-14-rt #1 SMP PREEMPT RT Tue Feb 12 09:57:10 UTC 2008 i686
> .. and here are the kernel settings from cat /boot/config-2.6.22-14-rt |
> grep PREEMPT
> # CONFIG_PREEMPT_NONE is not set
> # CONFIG_PREEMPT_VOLUNTARY is not set
> # CONFIG_PREEMPT_DESKTOP is not set
> # CONFIG_DEBUG_PREEMPT is not set
> # CONFIG_CRITICAL_PREEMPT_TIMING is not set
> Looks realtime to me.. also the latency is really low (5-10ms
> conservatively), much lower than I have experienced on other OS's, with or
> without realtime. But, if you know something I don't... I have open ears.
Nope, you got real-time there, for sure. I was wrong then.
> Ubuntu runs so nicely on a laptop though... would hate to switch after
> finding such an easy-to-operate linux distribution because pd and only pd
> doesn't like jack in realtime.
Dunno. You're playing Xrun whack-a-mole. Done that; it's not fun.
Here's what I did to RT-ify my system (on Debian, but Ubuntu is based on it):
Also, I expect you know to use chrt to give the IRQ of your audio interface top priority, higher than JACK and any other process. That's a crucial step. If I omit that, then I get clicks and pops too, which is why I wrote a script to do it automatically. You could also install and configure the "rtirq" package, which works great too.
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