[LAD] a forward re: a JACK performance problem

[Dave Phillips]

Greetings,

Sorry for the forward. Kim Cascone sent this message to the LAU list, but I think it needs the Eyes Of LAD. His email is kim at anechoicmedia.com. AFAIK he does not sub to this group.

Here's Kim's text:

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my config:
Dell Studio
Ubuntu 9.04
rt kernel 2.6.29.4-rt15-rt
jackd version 0.116.1 tmpdir /dev/shm protocol 24
Ardour 2.7.1 (built from revision 4296)
USB iMic audio interface
KOrg nanoKontrol
cpufreq-set - both cpu's are set to 2.0GHz and userspace

I'm trying to get Jack and Ardour set up/optimized for my fall tour
I'm using the rt kernel as stated above

my Jack settings are 44.1kHz: frames 512: periods 5
latency is not a huge issue for me since I'm only playing back audio for 
a live mix situation
and xruns in Jack seem to be tamed to 0 during playback

my Ardour session is 30 minutes in length, has 8 tracks of audio, and 
the fader levels are assigned to the nanoKontrol

everything works fine for the session except at some random point after 
playing for a while I get a single short burst of AM sideband noise, 
like I'm multiplying the audio on the mix buss by another audio signal

it doesn't happen (so far) more than once per session and it doesn't 
seem to be correlated to anything like mix buss levels or clipping on a 
single channel etc

is there a setting in Jack that I'm overlooking or has anyone 
experienced a similar intermittent burst of noise in playback with 
similar Jack settings? or if this topic has already been discussed can 
someone point me to a link in the archives? I wasn't able to find 
anything on a cursory search

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-- also, I  started Ardour from command line when Jack wasn't running 
and I got three panels in the open dialog box -- one of them being a 
Audio Setup panel

-- is there a way to see this panel after starting Ardour with Jack 
already running?


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Kim Cascone <kim at anechoicmedia.com>