Subject: Re: [stella] Midified VCS... From: Oliver Achten <achten@xxxxxx> Date: Thu, 22 Nov 2001 10:26:44 +0100 (MET) |
Hello Chris! > Wrong. The video inside the chip is just a 7-bit number. The only real > CVBS thing there is the chroma delay, which is just a tapped delay line. > All the analog voltage levels are created off-chip, on the motherboard. > To represent 128 colors with RGB, you still need 7 bits, and then how do > you split them? You'd need 9 bits to split evenly between the 3 colors. > And even then, you may not be able to reproduce the colors in the original > palette. Maybe, but I don't think it's worth the effort right now. You don't have to make it so complex. Just output the 7bit color value, and route it externally through a PROM, where the color values are hardcoded (for both NTSC and PAL). Alternatively, if you want to do the RGB encoding On-Chip, using an YUV DAC could simplify the On-Chip decoding, but you would need more pins (9 color bits, as you said, and the 3 luma levels), and YUV decoders are not that cheap... So the PROM Method would be more effective. > Yes, I'm writing my thesis on this chip. I'll reprouce the chip in some > form, and the paper will be *very* detailed, and *very* complete. That sounds very great! :-) Greetings Oliver -- GMX - Die Kommunikationsplattform im Internet. http://www.gmx.net ---------------------------------------------------------------------------------------------- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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