Hal 9000 hit the nail on the head. I actually used these wipes some in Austin Powers where I could get away with it, but they look worse than hard cuts for something like Star Wars. But you are right, Doc, in that it will just re-encode the regions of video where change has been applied. It's always sensible to cut just the changed frames into their own region as a result, limiting the re-encoding to the smallest amount possible.