Adding autoplay videos to portfolio

Hey all! So, this site:

https://andyrobertscreative.com/

Has videos in it's portfolio! Which I have been trying to do for ageees. Using inspect I've been able to see that they've somehow attached .sqs-video-background to those projects and that somehow it makes a video iframe appear with a fallback image while it's loading. 

Can anyone figure out how they've got this working and help? I'm getting pretty desperate. 

Thanks so much in advance! 

Hi,

You can consider using Gif Image instead. We can give code to change default image to gif image