How do screen video capture apps record audio?

[brassplyer]

Trying to get to the bottom of a problem with MSI Afterburner in capturing online game play.

XP Pro SP3, Audigy Platinum ES audio. I made some test captures of online gameplay. I find it only captured the audio in mono. It's supposed to do it in stereo. Tried various settings. I was getting stereo capturing the home screen which has some audio background but once it got to the level of gameplay, only mono. There are plenty of examples of Afterburner capturing stereo audio on YouTube.

Normally I have the onboard audio disabled but for purposes of experimentation I re-enabled the Azalia audio in bios, loaded the Realtek drivers. The Audigy is still installed but I have the Realtek audio selected as the default within Windows and specified within Afterburner.

With the Realtek audio I'm getting the same behavior as with the Audigy. I get stereo audio at the point of the home screen but only mono audio within the game. Youtube video records as stereo.

Follow up:

If I start recording while I'm still on the main screen, I get stereo, if I wait until I'm in game, I get mono audio.

Anyone have any insights?

Thanks.