Can you get a transparent background with video? with what codec?
what is wrong with sequenced images?
I’ve heard that quicktime can contain an alpha channel [I’m pretty sure most avi codecs cannot]
thanks… what do you mean sequenced images?
A “sequence” of still images. They can be any format and are usally numbered, e.g. myname0001.tga, myname0002.tga, etc.
Then, you can have the alpha channel in the image. Just assemble your video in the Blender sequence editor with the stills overlaying the background video.
hmm, well I guess that would be useful if you wanted different lighting situations… however I believe you could achieve any affect the sequence editor would produce by just modeling it… hmm- well thank you for the info! I appreciate it 
You can produce sweeps and fades from one scene into the other by modelling?
you can if you do it right
by sweeps you mean sliding one video off the screen and another video onto the screen?