This is what I've been doing, it works great. I've tested up to 4GB video files transcoded in the browser, then uploading the resulting video data. Also extracts thumbnail images, then uploads them to the server. Then I just do a quick verification server-side to check that it is actually a video or jpeg file, but the user's computer does all the work, so there is essentially zero cost for the whole ffmpeg transcode operation. It's brilliant.