| > Might not actually be RGB, did not look at the schematic. But having RGB before modulating into NTSC's color difference signals is not uncommon The standard NTSC Apple II does not generate color this way, but the European PAL models do. The native Apple II video signal is 560x192 1-bit monochrome pixels. The PAL video circuit converts video signal into a digital stream of color pixels, 4 bits per pixel. It then converts the digital pixels into analog YPbPr signals by attaching various resistors to each of the 4 bits. The YPbPr signals are then fed into a PAL encoder chip. Presumably, the original authors used these YPbPr resistor values to determine the colors sent to their Bulgarian PAL/SECAM encoder. This is a schematic of the PAL color encoder for the Apple IIe: https://imgur.com/CQH7vNS 1. The native monochrome video signal is SEROUT in the top-left of the schematic. It is fed into the LS164 shift register. 2. The LS175 buffer captures each 4-bit color pixel from the shift register. 3. The output of the LS175 is then fed through a various resistors to generate the YPbPr signal which are fed into the TCA650 PAL encoder. |