adding virtual webcam

[CaesarCZ]

hello, I'm capturing input from a USB webcam, do some filtering on the video and would need to output it to another, this time virtual, webcam device that I somehow need to add to the system (WinXP SP2). Even a .NET solution is okay with me (though I doubt there is some). 1) would I need a custom device driver to do that? 2) if not, which way should I go? thanks