[LAU] Fedora 12 & CCRMA

Niels Mayer nielsmayer at gmail.com
Mon May 17 05:36:52 UTC 2010

On Sun, May 16, 2010 at 7:12 PM, Fernando Lopez-Lezcano <
nando at ccrma.stanford.edu> wrote:

> > > Speaking of pulseaudio,
> http://old.nabble.com/Re:-Fwd:-jack2-p28288652.html is
> > > a potential bad interaction between pulseaudio and jack (through
> > > /etc/security/limits.conf, potential priority escalation issue).
> ...
> Not that many "tweaks". The ability for all users to run jack with
> realtime scheduling is "added" when you install the Planet CCRMA jack
> package. That thread talks about some security problems that could arise
> with the use of realtime scheduling, that is definitely not the source
> of your problems.

I'm not so sure about that...  It might be a good idea to make sure it's not
the same problem described here:

I experienced the similar lockup problems with jackd/qjackctl prior to my
change (
Note that these lockups DO NOT require a reboot. What's happened is that the
GUI/Xserver ends up getting locked up (via qjackctl) so if you SSH in to
your box and "killall qjackctl" you'll unlock ( Make sure to also do
"killall jackd" afterwards.).  Unfortunatelythe X server is so locked-up
that you can't Alt-F2 and login via console and kill it that way.

HOWEVER -- in testing out a new $5.00 soundcard, I also experienced
transient lock-ups again with jackd/qjackctl. The one thing that I could
point to consistently as causing problems: having the wrong settings in
'alsamixer', i.e. when one of these is set to "on" you can neither play
directly through ALSA, and jackd will hang:

> ** in alsamixer (F3-playback):

Item: "Multi Track Rate Locking" set to  [Off]

Item: "Multi Track Rate Reset" set to [Off]

Likewise, if the card is locked to the wrong sampling rate , jack may not be
able to reset it if the above settings are wrong.... To make things worse,
it seems like some of these settings are "sticky" and may require
loading/unloading the driver module or rebooting for the change to take

Similar badness may be going on w/ your soundcard, which has been a source
of longstanding problems in jack and alsa ... problems that often can be
remedied via alsamixer magic:

-- Niels
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