Originally Posted by ovale
This is really interesting. I had a similar idea but I have not the skills or time. The problem to solve was how to write on this clut without additional address bus. A gpio or some magic color sequence switches on/off the clut in write mode. At that point the RGB data are interpreted as address, value touples.
The drawback is that clut can be changed only on the vblank.
A new vidiot savant
could also transform halfbright mode in a real 64 colors mode, and as you said perform yuv to RGB conversion for a yuv ham mode.
Please do it
YUV<>RGB can be made in analog, programming CLUT content can be done on multiple ways, first you can use genlock signal with colors to store data in CLUT (ZD zero detect signal is active on OCS for Color 00 but in ECS it can be active for any signal so... but there is few other ways - like HAM-E, having XMOS CPU on board - 3E/$ cost - simplest 400MIPS with 4 slices give some flexibility - interpolating Copper chunky for example, CLUT switching etc)
Going slightly further and accessing Denise (RGA + other signals) gives lot of possibilities.