Jack and realtime kernel problem
 

Hi
I'm using an Inspiron 8200 as a cheap audio workstation. I've installed the Debian kernel and xfce as the desktop.
I've compiled a 2.6.18 kernel with the rt patch from http://people.redhat.com/mingo/realt...tch-2.6.18-rt5 using the instructions at http://forums.debian.net/viewtopic.php?t=13123. I've allowed realtime preemption in menuconfig.
The kernel compiles and installs properly but when I try to run jack in realtime mode, it returns the message

"jackstart: cannot get realtime capabilities, current capabilities are:
=ep cap_setpcap-ep
probably running under a kernel with capabilities disabled,
a suitable kernel would have printed something like "=eip"
back from read, ret = 1 errno == Success
jackstart: could not give capabilities: Operation not permitted
jackd 0.101.1"

I've tried editing edit /etc/security/limits.conf, appending @audio - rtprio 99
@audio - nice -10 @audio - memlock 250000 to the end of the file but no better.


Can anyone tell me what I'm doing wrong?

Further, dmesg|grep real returns
Realtime preemption support (c) 2004-2006 Ingo Molar
Realtime Clock Driver v1.12ac

a few things
first don't use jackstart
instead use
jackd -R -P70 -dalsa -dhw:0 -r44100 -p512 -n2
or something similar

i'm not 100% sure but check if jack will start as root
if it does then you need to allow RT access for users
either with the old realtime security module (not a great idea)
or with a PAM that has rt-limits
what we were doing when i installed etch not to long ago was installing the PAM package from ubuntu_studio. this appears to not be available right now but
As of version 0.79-4 the Debian pam package already comes with rtlimits
so check you version

I just downloaded the zip file for Jack. I am sure there is about 50 pges of dialog on how to install software for linux, but, is there a atraightforward explaination for wht to o next to get this installed on my copmuter so I can use it? Thanks

Thanks studioj - I tried running jack as root and got the same message. Any suggestions?

Hi phazon - what distro are you using? Jack is included in most and installation is easiest via your installation manager (e.g apt-get or synaptic for debian). You should install jack and qjackctl (which is a gui for jack).

and you used jackd directly instead of using jackstart ?

Thanks studioj. Problem solved, not sure of which step worked :) but I started again with minimal debian installation, compiled 2.6.21 kernel with rt1 patch, reinstalled jack, edited limits.conf
Now works well in realtime mode, 1 hour without xruns and counting...
I may have had the syntax for limits.conf wrong before, this time used http://alsa.opensrc.org/RealtimeKernelAndPAM