Swift - Create Live Wallpaper

I simply can't find documentation on how to implement live wallpaper. Questions in the forum are all outdated and with very little information.

I did find this forum info describing the format and I've tried my best to create the mp4 as described:
https://developer.apple.com/forums/thread/18610

My app can currently share mp4's and I can save it into my photo-library. I can't seem to use any of the mp4 for live-wallpaper though.

I'm using Swift and have tried pretty much all of the AVVideoCodecType's to no awail.