How to transcode AVI files to MP4 or other formats offline? I'm making a StepMania clone for web, but I can't use the background videos because they're in .avi format and most web browsers can't decode it. I want to transcode them to MP4 blobs. ffmpeg.js seems like a solution, but it's huge - 24 MB of JavaScript (almost the same size as my game). There should be another way.