Add HTML element and insert following code and give a class such as " fix-bg-vid "

<video autoplay muted loop>
<source src="http://www.w3schools.com/html/mov_bbb.mp4" type="video/mp4">
<source src="http://www.w3schools.com/html/mov_bbb.ogg" type="video/ogg">
</video>

And since RSD yet to support % for some elements all you need is adding the following code manually to your CSS for <video> tag

.fix-bg-vid video{
min-width: 100%;
}

The rest done with RSD itself , see the example in attachment

updated RSD File:

Sorry guys, the two earlier project file was not mobile friendly

With this current updated version no need to add / modify CSS file, it has done all within RSD in single file.

Check out this attachment and hope it helps.

@ mark I did on the other thread mate but I know you have found that no

@ Mansour Thanks mate I ma having a look at yours as well !!