Tks for the team that provide a solution that let Safari showing the background video normally, As I dont want to see the youtube video 2nd time, so I make the width & height to 2, if anyone want this theme work but looking exactly same as the demo, you can try this code:
<iframe width=”2″ height=”2″ src=”//www.youtube.com/embed/xxxxxxxx” frameborder=”0″ allowfullscreen></iframe>
*But as most of the Android devices / iPhone/ iPad / iPad mini, do NOT have flash player to play your background video embed code, which must need Flash player(I guess you use the old style youtube embed code, like: <object…….), so please fix the code for embed youtube to iframe (just like the one you just suggest.