by JAB Creations » Sun Oct 02, 2011 5:27 am
There are more difficult and technically in-depth ways. You did not list the context of why thus you are currently open to pretty much any answer that comes to mind by others.
YouTube has very slowly started switching to WebM format, I download videos with a toolbar because my ISP insists on not letting me watch videos without stuttering on a 12 megabit internet connection. It gives me several options and sometimes the choice between mp4 and webm file extensions.