You’re definitely going to need to use a combination of roto and a darn good keyer. Fortunately, After Effects should be able to handle this. Unfortunately, if you’ve never used After Effects, this is hardly a first project type of project though you’re welcome to give it a shot.
Even with the roto brush in CS5, you’ll need a decent amount of contrast for the tool to roto out your foreground. First off, is there a lot of motion in the shot? If shot, a simple mask should take care of the bulk of it. Depending on how different the green on the box, and the green on the matte are, you might get away with using two or three instances of the built in color keyer, some spill suppression (though not much, so you don’t affect the green on the box) and a matte choker.
Pete O’Connell, in the After Effects forums has some great DVDs and tutorials on roto techniques that might help you too.
Richard Sanchez
North Hollywood, CA
“We are the facilitators of our own creative evolution.” – Bill Hicks