[LAU] jack trouble

Hi

I have some trouble with jack, that I'm hoping someone here could help
me with. First a bit about my system: It's a laptop running ubuntu 8.04
on a 2.6.24-23-rt kernel. I use an edirol ua-1a usb soundcard, since the
buildin HDA soundcard seems to be total crap.

Sometimes my jack (started with qjackctl) is "messed up" by a client,
often caused by some kind of high load, either on cpu or loading large
stuff. This happens both with my DAW (eXT2) and chuck (which is what I'm
trying to fix the problem for right now). Is sounds like some kind of
sync with the soundcard is messed up (how evert that sounds like), the
sound is distorted in a very charasteristic way, with lots of crackling.
The problem persists until I restart jack, then everything is fine again.

If this could be fixed somehow, the hotfixes in the rest of the post are
irrellevant, or only of general interrest.

Now I figured I start jack from the commandline (something I never did
before) on every song, to emulate the "restart jack" strategy mentioned
above. I looked in ~/.jackdrc and found:

/usr/bin/jackd -R -P80 -dalsa -dhw:1 -r44100 -p512 -n3 -s -S

I I run that command, jack is started just fine. However sometimes it
dies like this:

subgraph starting at ChucK timed out (subgraph_wait_fd=7, status = 0,
state = Running)

It might be something I do wrong in my chuck code, but it's random
places (always on a down beat) and never happens when jack is started
from qjackctl. What does the above errormessage mean, and can this
information be used to start jack differently to avoid the problem?

Notes:
1( I played around with stuff after writing the above and it seems that
jack can also crackle when started from the commandline.

2) I also tried to kill X and run from a terminal, same problem.

3) The problem seems to be related to the cpu load. If the load is over
80, the problem is almost always there, if lower than 60 it's sometimes
there.

4) The problem (crackling noise) is also there with the buildin HDA intel.

5) I also booted my debian stable on another partition, same problem.

It seems to me that it all boils down to jack. Possibly it could
(should?) get a better soundcard (Behringer FCA202 firewire seems to
work with linux), but would this really solve anything?

Any input appreciated!

-- 
Atte
http://atte.dk    http://modlys.dk
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