Replicate the low resolution "blocky" look of CCTV cameras

Hi there.
I am working on something in which I have to have a camera look as close to generic CCTV quality cameras as possible. I have been able to create a lower resolution output using a render texture at a lower pixel ratio to achieve a lower quality effect although I've yet to achieve the ability to recreate the "blocky" pixelated effect that can happen around motion. If anyone has any idea what I'm talking about can someone help me understand how to implement it?