video header background

It’s been a while since i’ve looked at any code, needless to say i’m struggling a little.
the website working on is https://www.moorediamonds.com

I’m wanting to use a video as the landing page header background. I’ve manage to pull it though a separate home_video.php file and it seems to play fine. The problem i’m having is the positioning of the brand logo which is being forced down below the header. I would simply like it to appear as normal over the top of the video. I’ve tried using z-index but it doesn’t seem to work.

Any help would be greatly appreciated!