Green Screen Effect Doesnot work

[pawaom]

I watched this demo video of the socialite app,

https://www.youtube.com/watch?v=3zXVPU2vKXs&list=PLTQYvEMxkbXu4ZRLNhUyE0trUjzQG01PT

however when I tested the code on

Samsung galaxy f12
Samsung Tab galaxy tab A7 Lite

The "selfie" cam doesnot work