Hi Tom,
@PeteSharp provided some code in this post a few months ago. There is no example web page of that code in use, unfortunately, but perhaps it can be of help to you. He is switching out video based on breakpoint, but the context of what he is doing is important. He is using a Code Widget to put a video inside a DIV and then he styles it separately with CSS code. So you could do something similar whereby you adding padding in the CSS.
Here’s another discussion about background video and padding: