I know HTML5 doesn't allow DRM in video and audio files (which would be a pain anyway), but is there anyway to stop a user downloading the file?<p>Can you forbid downloading, but not playing? Can you hide the URL from "view source," "inspect element," and the activity window?
No more than you can protect an image in a page from being downloaded. e.g. you could escape the URL or check referrers, but that's not really going to stop anybody.