Magic Music Visuals

Hi Everybody!

This may be a totally stupid and illiterate question - but hey that's the internet - so I ask anyway.

Is there a way these days to remove the background from a video so that it can be substituted with another video (similar to the old blue box trick)? What I was thinking is that if I record a video A let's say of a person and then take a still or short video sequence B without the person (exact same settings, same light, etc.), is it possible to compare A and B and turn everything that is the same in both into an alpha channel for transparency in video A (so that only the person remains)?

Thanks in advance for enlightening me

We discussed this a while ago actually, and I wrote a simple shader. You can check it out here: viewtopic.php?f=2&t=945&p=6024#p6020

You can read everyone's comments but overall it's very hard to make it look perfect.

thanks a lot. this does already help.
I got some fairly promising results which make it worthwhile trying to capture some real footage and process it via Magic