xorg interference with sound playback in selected apps

[sounds_northern]

Hi all,

This is my first post but I have used Gentoo for _at least_ three years now. I am a great believer in the 'search before post' maxim, which evidently has always served my questions with answers. However, I have come stuck and it's annoying!


Background: I am a composer and use audio apps to create live electronic music. Most commonly, I use Pure Data (PD), Rezound and Audacity. The subsystem is Jack. Hardware is more than adequate, with an AMD Athlon XP 3200, 1 gig RAM and SCSI HDDs. It all works well and is configured, as far as I know, quite well.

The problem I have, however, emerged (no pun intended) in November last year during an electronic arts festival. When producing live sounds in Rezound, the output would become jittery, as if the CPU was playing catch-up with real time. Most notably, it was when the mouse moved to/from certain parts of the GUI and scrolled the wave view, either up/down/zoom. When using PD, I notice that it does the same. Scrolling makes the sound momentarily pause several times in quick succession. Clicking on buttons in PD causes an audible click.

I assume, because it doesn't do this in only one program, that it's a problem with xfree.

If anyone has any ideas as to what I can look at, I'd be grateful. I've run out of ideas, though my technical knowledge of the inner workings of X is very little.

I can post some system info (version numbers etc.) tomorrow when the computer is back on.

Thanks in advance.