I am trying to simply play an HTML5 video which will be compatible with all common browsers (including mobile devices). For now, I am testing with one custom video and a sam
iOs doesn't support all the profiles that h.264 provides. You have to encode your h264 with a baseline profile only in order for it to be playable on iphone/ipad.
Please try to use QuickTime Player to export the video optimized for iPhone, check out this blog post http://www.treysmithblog.com/how-to-make-html5-videos-for-iphone-and-ipad/