Reminds me of a weekend hobby project I did back in 2014 or so. I had an itch to play with analog video signal generation from an atmega328p. Rather than use one of the existing libraries, though, I started from scratch with the goal of achieving the highest possible resolution. I used the SPI peripheral to clock out 8 pixels at a time at 8Mhz without any gaps, giving me something like 12 instructions to prepare the next byte. There wasn't enough RAM for a frame buffer at the resolution, so I instead used character tiles; that ate up the whole budget. I forget what the resolution was, but it was significantly higher than the existing library was capable of. There was a jitter, which I tracked down the the variability in interrupt latency due to the AVR having variable cycle length instructions. I was using a timer interrupt to schedule the start of and complete transmission of each scanline, so that the main program could focus purely on application logic. I wrote an inline assembly routine at the start of the interrupt handler to insert a variable number of noop instructions depending on the relative phase of the hardware timer, and the output became rock solid.
That of course reminds me of a project in 2007 where I needed to go the other direction, and decode an analog video signal on an 8 bit PIC microcontroller. The signal was from a camera on an actuator, meant to detect the relative position of the sun for the purpose of aiming a parabolic solar concentrator. I was able to filter out all visible light with some overdeveloped film negative so that the video signal was simply a white dot on a black background, and then wire it up through some voltage dividers to the PIC's two voltage comparators. One comparator detected sync pulses, and the other one detected black to white transitions. The firmware would simply track the timing of sync pulses to know the current scanline and position within the current scanline. Good times!
