ok, I think I'm done with this project?

it now plays conway's game of life and creepy noises, all from a single STM32G431 MCU with minimal external components, which is really all you can want from some lowfi analogue TV stuff.

In the process of making the audio work I ended up changing from channel 2 to channel 3 to get rid of the interference from the 48MHz clock I use for audio, which also means I'm running the CPU faster and get a little bit more processing time. Number of external components is now 4 resistors for mixing the baseband video signal and 5.5MHz audio carrier. Unfortunately going to the higher frequency also meant losing some signal quality, since I'm operating the internal opamp even more out of spec. Or maybe I'm just unlucky and there is more interference on that frequency here.