Video and external USB sound conflict when I'm using Skype.

I have a recent M-Audio MobilePre external USB sound device (no firmware loader needed), and a Logitech QuickCam Pro 4000. I'm running Debian unstable, kernel 2.6.25 with ALSA. I'm using Skype 2.0.0.68 (either static or Debian). System is a ThinkPad T61 with HDA Intel builtin audio.

When I use the Intel soundcard built in to my ThinkPad T61, external video works. But when I use the MobilePre (snd_usb_audio), video goes weird: "Test Video" works perfectly, but actual video (my self-preview and the remote user's) just shows a random snippet of video RAM (little piece of screenshot, black, etc). When I initiate a test call and then run "test video" I get the same thing: the video test box shows random stuff, but Skype thinks it's working.

If I initiate the test call and then click test video quickly enough, I get the following:



...and the call dies, and video works as it would if there were no call.

I'm using Skype 2.0.0.68 (tested static and .deb) with "default" for all audio, which I control before Skype startup with ~/.asoundrc. For example, if the MobilePre is device 2:



...but I've also played a little bit with selecting the devices from Skype's dropdown (this method presumably won't update when I plug/unplug devices, so is not preferred). I have not tried this extensively, but I will if you tell me what to test.

I can play (audacious) or record (audacity) and then run xawtv, so this may well be a Skype-specific problem...?

Please tell me what other information I can provide in order to debug this!

Cheers,
-Ben

Update (does anyone care?): I have configured Skype with both Sound Out and Ringing set to the ALSA default device (ie. the USB MobilePre when it is attached, etc, controlled by udev) and locked the Sound In to "HDA Intel", and things seem to work now. I guess "Sound In" is the problem? Still, it would be awfully nice not to have to futz with my mic in order to make a call, and also to have the better sound quality of the external device.

Note that the mic and MobilePre feed 2-channel audio. Is that a problem, somehow? An ALSA pseudodevice could probably fix that if that's what it is.

Have you tried to put the webcam on left usb and headset on right one or viceversa?
There is probably a bandwidth problem or maybe a power problem.

Many many thanks! That was it!

No problem, happy to have solved your issue.
There are similar problems also under Windows, so now when I hear these type of issues I always recommend these things before moving ahead