Something interesting i learned today about the html5 video tag is that even if preload is set it's up to the player the render engine is using to fetch the index of the file first as with mp4 this is usually at the end of the file.

This means that for Blink and Gecko most likely fetch this first themselves. But for webkit it opens in quicktime on mobile devices which you cannot pass parameters to and flat out waits for the entire stream to start playing.