Im going over all the settings and i see
Newer mobile devices can display HD video (iPhone 4/iPad 1/some Android play 720p, iPhone 4s/iPad 2+ play 1080p) but many older devices (iPhone 3Gs/older Android) can't play higher than 480p. Increase at your own risk.
So my thought is, what the big guys do at least is to encode into several formats, and sizes
so, if device can play 1080p, then serve the 1080p file, if only 720p, then serve that file.