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Although only 16 different colors were allowed on c64 (more exactly, in the VIC-II), which came from a fixed palette, the video output created an analogoue tv signal.

Which means, somewhere in the final, D/A conversion phase of the vic signal generation, a palette should have existed, which defined the different rgb signal levels, indexed by the 4bit color code.

What is known from it? How many analogoue signal levels did it have?

(Btw, in this 16-color palette, there were 5 greyscale colors. Thus, the number of analogoue signal levels should have been at least 5.)

Extension, reacting @Mark's answer:

Ok, the TV output had a YIQ. But, somewhere in the VIC II, there should have been something with a color index 0-15 as input, and with an analogoue YIQ as output. I suspected it was some hardwired palette table and a D/A converter, but you say it wasn't. What was it then? How did the 4 color bit -> 3 YIQ signal level work?

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    Are you familiar with the following resource? It may or may not answer your question, Commodore VIC-II Color Analysis (Preview) – Q.Q. Quinn Apr 20 '16 at 6:53
  • @Q.Q.Quinn Yes! It is an IT-historical relic! – peterh Apr 21 '16 at 4:54
  • @Q.Q.Quinn I would like to upvote/accept your answers but you haven't one. :-( – peterh Apr 21 '16 at 11:59
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"Output levels" are a feature of digital-to-analog converters, particularly of the sort used with computer monitors with distinct red/green/blue signal channels.

The VIC-II doesn't do this, so it's not really meaningful to say it had output levels. Instead, it creates a broadcast television signal directly (either PAL or NTSC), with each color mapped to a distinct luminance/chrominance (YIQ) combination (as noted in the Wikipedia article, they had complete freedom in selecting these combinations). The presence of five shades of grey just means that five of those combinations had an I and Q of 0.

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  • Ok, the TV output had a YIQ. But, somewhere in the VIC II, there should have been something with a color index 0-15 as input, and with an analogous YIQ as output. I suspected it was some hardwired palette table and a D/A converter, but you say it wasn't. What was it then? How did the 4 color bit -> 3 YIQ signal level work? – peterh Apr 21 '16 at 4:44
  • Ok, meanwhile I've understood your answer using QQ's link. Thank you! – peterh Apr 21 '16 at 4:55
  • @peterh: in that case, can you edit the missing piece of information from QQ's link into the accepted answer? – Cactus Apr 21 '16 at 11:57
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    @Cactus Yes, at the end of the CET worktime :-) – peterh Apr 21 '16 at 12:05

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