I had this project in mind for sometime now. It is inspired by an old 80's magazine project called the "video palette". It offers several effects to toy with the video signal that has been split from the sync signal. There're two big circuits, a keyer and a posterizer and a rotary switch just send the proper signal into the keyer (negative, posterizer,...). There's also a lowpass filter to blur the image.

I wanted a bit more lo-finess to it so I added a microcontroller (STM32F03F4)  and a 12bit DAC to generate others signal that could be mixed with the video signal (as well as a midi input). Considering the lack of video encoder, the signals will only be black and white.

Considering the bandwith  requirement it's always a bit tricky to select part, especially for the multiplexer. Too much ON Resistance in the switch and you loose sharpness. For the main multiplexer (the one that split the signal and re-sync it with the modified video) I designed the PCB for two options: The NX5DV330D which is a video-multipler and could the job nicely and the trusty CD4053.

NX5DV330 datasheet