JACK getting insane number of xruns

[D. Michael McIntyre]

I've just replaced Dapper with Ubuntu Studio.  I ported my /home directory 
forward, but to eliminate any cruft issues, I've tried all of this with a 
clean user.

I have an ice1712.  I've recently reinstalled an old emu10k1 that I was using 
for experiments to determine the cause of broken sound on Dapper, and that 
card is still in my machine, although I'm not currently using it for 
anything.

The presence of the emu10k1 represents one change, and swapping for 
Feisty/Ubuntu Studio represents another. Somewhere in the mix, JACK got 
busted horribly.

I'm open to suggestions how I should diddle my JACK command options for better 
results.  I assume with this being Ubuntu Studio, all the low latency and 
security limits PAM realtime priority gobbledegook will have been done for me 
out of the box.  (If that isn't the case, I'm sorely, sorely disappointed.)

I run JACK by way of QJackCtl.  This is the jackd command it had been using 
probably for two or more years:

/usr/bin/jackd -v -R -P5 -t1000 -dalsa -dhw:0 -r48000 -p512 -n2 -s -S -M

Running that now, I get:
getting driver descriptor from /usr/lib/libjack0.100.0/jack_freebob.so
getting driver descriptor from /usr/lib/libjack0.100.0/jack_oss.so
getting driver descriptor from /usr/lib/libjack0.100.0/jack_dummy.so
getting driver descriptor from /usr/lib/libjack0.100.0/jack_alsa.so
jackd 0.102.20
Copyright 2001-2005 Paul Davis and others.
jackd comes with ABSOLUTELY NO WARRANTY
This is free software, and you are welcome to redistribute it
under certain conditions; see the file COPYING for details

JACK compiled with System V SHM support.
server `default' registered
loading driver ..
apparent rate = 48000
creating alsa driver ... hw:0|hw:0|512|2|48000|0|0|nomon|hwmeter|soft-mode|
16bit
control device hw:0
configuring for 48000Hz, period = 512 frames, buffer = 2 periods
ALSA: final selected sample format for capture: 32bit little-endian
ALSA: use 2 periods for capture
ALSA: final selected sample format for playback: 32bit little-endian
ALSA: use 2 periods for playback
23154 waiting for signals
registered builtin port type 32 bit float mono audio
registered builtin port type 8 bit raw midi
clock source = system clock via gettimeofday
required capabilities not available
capabilities: =
new client: alsa_pcm, id = 1 type 1 @ 0x805af28 fd = -1
new buffer size 512
registered port alsa_pcm:capture_1, offset = 2048
registered port alsa_pcm:capture_2, offset = 4096
registered port alsa_pcm:capture_3, offset = 6144
registered port alsa_pcm:capture_4, offset = 8192
registered port alsa_pcm:capture_5, offset = 10240
registered port alsa_pcm:capture_6, offset = 12288
registered port alsa_pcm:capture_7, offset = 14336
registered port alsa_pcm:capture_8, offset = 16384
registered port alsa_pcm:capture_9, offset = 18432
registered port alsa_pcm:capture_10, offset = 20480
registered port alsa_pcm:capture_11, offset = 22528
registered port alsa_pcm:capture_12, offset = 24576
registered port alsa_pcm:playback_1, offset = 0
registered port alsa_pcm:playback_2, offset = 0
registered port alsa_pcm:playback_3, offset = 0
registered port alsa_pcm:playback_4, offset = 0
registered port alsa_pcm:playback_5, offset = 0
registered port alsa_pcm:playback_6, offset = 0
registered port alsa_pcm:playback_7, offset = 0
registered port alsa_pcm:playback_8, offset = 0
registered port alsa_pcm:playback_9, offset = 0
registered port alsa_pcm:playback_10, offset = 0
++ jack_rechain_graph():
client alsa_pcm: internal client, execution_order=0.
-- jack_rechain_graph()
load = 0.0563 max usecs: 12.000, spare = 10654.000
delay of 53040.000 usecs exceeds estimated spare time of 10654.000; 
restart ...
[snip of thousands of xruns generated in a continuous stream]
jack main caught signal 2
starting server engine shutdown
stopping driver
delay of 53004.000 usecs exceeds estimated spare time of 10654.000; 
restart ...
unloading driver
freeing shared port segments
stopping server thread
stopping watchdog thread
last xrun delay: 53004.000 usecs
max delay reported by backend: 53043.000 usecs
freeing engine shared memory
max usecs: 12.000, engine deleted
no message buffer overruns
cleaning up shared memory
cleaning up files
unregistering server `default'

-- 
D. Michael McIntyre