Compositing video clips?

[whosithis]

Does AviSynth composite video clips on top of eachother. Say I had an animated logo AVI that I wanted to overlay on top of another AVI after dropping out the logo's key background color. Is there a way to do compositing like this?

[dividee]

The only way (I think) is to use Virtualdub's logo filter in avisynth (but it uses a sequence of BMPs, not an avi file)

[whosithis]

It would be pretty awesome to have this kind of capability. I've seen Nothing Real's Shake, and that is one powerful piece of compositing software.