[PD] wierd feedback popping with pd/freebob/jack/rt
reakinator at gmail.com
Fri May 23 21:18:13 CEST 2008
I made a comment on the patch tracker concerning this, directly on the jack
patch. However, looking at the patch, I cannot see how it would effect pd's
audio when running in real-time. All I know is I ran pd-0.40.3-extended
from April 15th yesterday, using jack in real-time, for a few hours and the
audio was almost flawless.
On Wed, May 21, 2008 at 3:34 PM, Rich E <reakinator at gmail.com> wrote:
> On Wed, May 21, 2008 at 3:20 PM, Ken Restivo <ken at restivo.org> wrote:
>> 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
>> > packagers recently switched to using full realtime preemption... I find
>> 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
>> > GNU/Linux
>> > .. 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_PREEMPT_RT=y
>> > CONFIG_PREEMPT=y
>> > CONFIG_PREEMPT_SOFTIRQS=y
>> > CONFIG_PREEMPT_HARDIRQS=y
>> > CONFIG_PREEMPT_BKL=y
>> > CONFIG_PREEMPT_RCU=y
>> > # 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
>> > without realtime. But, if you know something I don't... I have open
>> 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
>> > doesn't like jack in realtime.
>> Dunno. You're playing Xrun whack-a-mole. Done that; it's not fun.
> Ken, this made me laugh for quite a while. Thank you.
>> Here's what I did to RT-ify my system (on Debian, but Ubuntu is based on
>> 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.
> I had it on my last setup, but for got to do it this time. Thanks for
> reminding me :) Also, as my other post mentions, I sometimes got clicks
> with pd even with the script. I actually had to change the irq priority of
> pd to get rid of them, which is bad since it changes all the threads pd has
> instead of only the scheduler. I would get "I/O stuck... closing audio"
> all the time.
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