the software that is being used is swww for showing background wallpapers
and it uses only gif
if I try with any other thing then it will throw an error 
╭─ankur@ankur in ~
╰─λ swww img custom_wallpapers/animated/experimental.mp4
Error: "failed to decode image: The image format could not be determined"
when the user will select any video file from the script then with the help of ffmpeg it is converted into gif .
This is a sample of how it is being converted :
The reason to use swww is that is not consuming something like too much of processing power and it is also being used for static wallpapers
BTW<, I would recommend to use smaller videos so that it doesn’t takes too long to load the live wallpaper 