Help trying to display a video within an iPhone

Hello, I’d love to know the best way to have a transparent iPhone case with a background video inside that scales correctly responsively and also allows no overflow (to the left and right of mobile prototyping video).

I’ve tried numerous different ways and can’t get it to work correctly when resizing the browser window.

Perhaps this isn’t the best way to achieve this? I’ve tried exporting RGB+Alpha video from After Effects, but the output size is too huge…

Any help would be much appreciated.

Thanks,

Nick Kelly