
Creating Reference Movies to Optimize Web Playback
You can use reference movies to provide the appropriate movie for different users' connection speeds. For example, you can have a smaller movie streamed to users connected over a standard modem, and a larger version of the movie streamed to users connected over a broadband connection.
Apple provides a free tool, MakeRefMovie X, that greatly simplifies the process of creating reference movies. You can download this software at Apple Developer Connection.