I'm not sure why you can't have something like flash.<p>Imagine if the browser, noticing it's about to download a .flv, would not d/l the .flv, but would trampoline that to a backend server that would transcode to, say, .mp4 and then your browser (using AJAX for the async call) would load the .mp4 from the backend server.<p>I know that more complicated flash stuff, like games, and interactivity, would not work this simple way; but if there's a non-flash way of getting the same functionality in the browser via HTML5, then couldn't this "server-in-the-middle" approach work?