[LAU] Fluidsynth, soundfonts, jack, and latency

Guru Prasad B. R. prasadbrg at gmail.com
Mon Nov 2 03:03:32 EST 2009

Hello everyone,
  So I've been trying out AVLinux. By the looks of it, quite impressive 
- but I soon ran into a rather serious issue, but I doubt whether it has 
anything to do with AVLinux or not. I need your help in this knowing for 

My usual setup involves a piano sample on Linuxsampler and a strings 
soundfont on qsynth. I had an unusual gig last week that required no 
piano sounds, but instead use of multiple layered samples. I therefore 
used only qsynth, with 3 engines running concurrently. So in my brand 
new AVLinux setup, I loaded up my samples, and had sooperlooper running 
2-3 loops concurrently, all on a core2-duo macbook.

Initially, all was ok. No noticeable latency, no xruns whatsoever.But 
during the rehearsals, this happened: after sometime, specially at some 
point when sooperlooper was running full steam, suddenly there was this 
HUGE latency, coupled with lots of dropped notes. As in, I could hold 
down a dozen keys simultaneously on the midi controller, and not all 
notes could be heard; those that did, would  be heard  at various 
instants upto about half a second later. Completely unuseable.

This would persist even after restarting the jack server, but dissappear 
on rebooting the OS.

To me, what is scary and irksome, is not (only) that this glitch 
happened consistently, but that there were no error messages in the 
qjackctl window. No xruns. Nothing that suggested that something had 
gone terribly wrong somewhere (which it had).

I actually compromised on my gig sound, by offloading a lot of samples 
what I wanted layered. I don't know if it was because of this, but I 
didn't notice this particular issue on the gig itself (but it gave me 
sleepless nights prior). But then, 5 mins before the start of the 
program, I was left with no audio out of my system! (again, no error 
messages). Restarted jack server, and everything back to normal.

Again, no error messages/warnings. Not so much as a by-your-leave. ;)

I'm now intent on finding the source of the problem. I'm looking for 
pointers... where do I begin? Where's the 'smoking gun'?
Thanks in advance!


More information about the Linux-audio-user mailing list