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I use my laptop to run virtual instruments that I control with a MIDI keyboard. For this reason I need very low latency audio. I use a Roland EDIROL UA-1EX, a pretty basic USB 2.0 audio device which gets me down to about 11ms of latency. Here's the thing though - with my wireless turned on, every 30 seconds or so the audio will go choppy for about five seconds, which is terrible especially for live performance. I've gotten quite used to turning off the wireless whenever I practice or perform live, but it would be so much nicer to be able to use wireless networking while making music, for a variety of reasons.

Some extra clues: if I crank up the buffer size in my sound card's configuration, the problem goes away but the latency becomes far too great to be usable. If I use ASIO4ALL and run the audio through my onboard (sigmatel) sound instead, the problem disappears entirely. Too bad my onboard sound is so noisy and crappy - i don't need the audience hearing my mouse movements and hard drive activity over a PA system! I experience the same problem with another USB 2.0 audio device, my friend's Line 6 Pod UX2. I've tried disabling all sorts of devices and services on the machine but nothing has done the trick.

Computer specs: Dell inspiron 1525 with internal wireless N, 4GB RAM, Core Duo T8300. Windows XP Pro with all the usual tweaks and optimizations that people recommend for achieving low latency audio.

Any idea what causes this sort of problem? If it's a hardware-based reality, like wireless and USB crowding each other out on the same bus or something like that, that would inform my next laptop purchase decision. Or if there's some way to actually work around this that would be just fantastic.

Thanks for your help superusers!

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recommendation for your next laptop: go firewire for external audio hardware & applications and leave the USB to the mice. – quack quixote Oct 16 '09 at 4:59
quack, i've been looking at an expresscard solution as well, do you think that would work around this? – Barry Fandango Oct 16 '09 at 11:18
up vote 1 down vote accepted

The problem is that audio applications on Windows XP run as regular user-mode applications and are thus pre-empted when the system gets too busy. Windows Vista and Windows 7 run audio applications in a special mode called the Multimedia Class Scheduler. This may solve your problem.

It is also possible that the issue is in your wireless driver. If the driver takes too long to service requests, that can starve the system of resources for long enough that glitching will happen.

So suggestions are:

  1. Make sure you have the latest wiresless driver
  2. Upgrade to Vista or better yet Windows 7
  3. Get a new laptop. The noise you hear on your XP laptop should be missing from any Vista-logo'd device as Microsoft started measuring that in the Vista timeframe.
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