Make a video ONLY 2 colors? (Not grayscale) Unfortunately I do not have an example because I do not know the name of the technique.

I have seen in films at a local film festival an "effect" that makes the video black and white. I don't mean grayscale; anyone can make a black and white movie. What I mean is only black and white.

I know how to do this in programming with individual pictures. Get pixel color, and if its average RGB value is above 128, its white, and vice versa.

How would I do this in video? I personally have Sony Vegas Pro 13, and a friend has Adobe Premiere Pro CS6 that he can let me use.

I can add more info if needed, and I'll try to find an example.

Thanks!
You could use the Posterize effect in Adobe After Effects, and set it to 2 colours.  Or the Threshold RGB effect and set it to 127 (if it's an 8 bit colour video). You may have to greyscale the video first.