Several years ago the manufacturers of PCI video cards discovered a way to increase their performance by playing unfairly with the PCI bus. This can put a lot of awful "zipper" noise into the audio output when you move windows around the screen.
Check your XF86Config file and see if there is a line like
It would be under the "Device" section. Try commenting it out and see if that helps. Or try adding this line, if it's not there. I'm not sure which is the "right way". It didn't make a difference for me, but then I don't have a PCI soundcard.
"After looking around, it seemed that AGP was the way to go to stop getting audio dropouts whenever some video event occurred. This guess was based on the common explanation that the pops are caused when the PCI video card steals the whole bus to do some operations. Since AGP is a different bus altogether, it seemed like a good step.
"And I can say, at least at first glance, that it seems to be the way to go. At home, I had a Trio64, which recieved many pops and clicks (even when doing somet hing reasonably low on CPU usage). At work, I have a PIC Riva128 card, which also gets pops and clicks during focus changes etc. Just recently I purchased an AGP RivaTNT2? card, and I haven't been able to generate an audible dropout yet. PureData? still occasionally reports DIO errors, but I haven't heard any of them yet.
"Since it's quite hard to get a non-AGP card nowadays, this has to be good news for linux audio :) "
As mentioned above, a PCI video card tries to hog the PCI bus to increase its own performance. This interferes with other devices on the bus, including soundcards.
There is a good description of the problem at http://www.zefiro.com/vgakills.txt
Note that their list of solutions are all for Windows device driver settings. The only thing there that seems to have a clear analogy for Linux is the "pci_retry" option in your XF86Config file.
Note:I have also seen some anecdotes on comp.sys.ibm.pc.soundcard.tech that some VIA chipset-based motherboards, especially those with the VIA MVP3, are especially prone to this problem, and may also have problems with using UDMA mode for hard drives. I don't have much real information about this except that some people seem to like Asus motherboards better. Note that all these reports were from people running Windows 95 or 98... maybe that's their problem.
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