None of yours are solved my problem. But, I found a good solution for me to work properly right now. In between tags write this code:
<div style="position: fixed; z-index: -99; width: 100%; height: 100%">
<iframe frameborder="0" height="100%" width="100%"
src="https://youtube.com/embed/**[CHANGE HERE WITH YOUR YOUTUBE VIDEO ID]**?autoplay=1&controls=0&showinfo=0&autohide=1">
</iframe>
</div>