puredyne-team team mailing list archive

[Dan Stowell <danstowell+launch@xxxxxxxxx>]

Hi -

What are your experiences of xruns with the current beta?

I'm currently running jackd+scvim on latest broth on an Eee 904HD,
using the default p:d kernel (2.6.31-5-pure) and default jack settings
(block size 1024, rt, etc). Running a really simple patch (just a bit
of white noise) I get audible+reported xruns with a suspicious
regularity, they all occur when the number of seconds on the clock
ends in "2" (2.3, 12.3, 22.3, 32.3, 42.3, 52.3) - there must be an irq
every ten seconds that has the ability to get in the way.

I notice that jackd is running at a high-ish priority (20) but not as
high (70) as recommended by Flo Shmidt:
http://tapas.affenbande.org/wordpress/?page_id=40
The priority of 20 probably isn't high enough since various things
also run at that level (eg Xorg). I'm not sure which is my soundcard's
IRQ but that should also be higher than the others for smooth rt
audio.

To be honest I normally start jackd from a script, but I'm doing it
from qjackctl here because I expect that'll be how an "ordinary user"
(ho ho) will get at it. qjackctl doesn't seem to have a config option
for jackd's "-P" option. When running jackd from CLI and with "-P 70"
I don't seem to get xruns (although I don't actually get a priority of
70, according to top).

I found I can hack it by adding " -P 70" to the end of qjackctl's
"Server Path" option. This gets stored in
~/.config/rncbc.org/QjackCtl.conf and in ~/.jackdrc. The latter file
is present in skel but it's not sufficient to make the option stick if
you just do it there. It looks like it works to have a simple two-line
barebones config file /etc/skel/.config/rncbc.org/QjackCtl.conf
containing the following:

[Settings]
Server=/usr/bin/jackd -P 70

This seems to give a good default priority on first launch of
qjackctl, eliminating xruns in my simple test on one machine. What do
people think?

Dan
-- 
http://www.mcld.co.uk