Now, go to go to FRAME and turn on FOUR MOTION VECTORS, place MAXIMUM I- FRAMES to 90,000, then put the B-FRAMES to 0. go to MOTION and turn off RATE DISTORTION and CHROMA MOTION, then turn on QUARTER PIXEL MOTION ESTIMATION. Once you're there go to the place under VIDEO where it says COPY and change that to MPEG-4 ASP (Xvid) and click configure. Then it'll load the video, but don't get to excited. Take your AVI video and drag it into the middle of Avidemux and it'll ask you something about B frames.
If you're wanting to datamosh youtube videos then go to google and search 'youtube to AVI' and click the one that says (idk if its sketchy or not, but it works.) You're going to have to work with AVI files so if you have adobe premiere or any other video editing software that exports in AVI, then you're golden.
