just started using sony vegas and this thing is pretty awesome. currently, im trying to edit a video using a "green screen" footage i got from http://www.kickinitmovie.com/challenge/. im trying to use chroma effects to change the background but the footage has a black background. needless to say, the output i've produced is not that too good. am i missing something here or was i doomed to failure to begin with? lol... can anybody help?