Re: Blurry picture

From: Segher Boessenkool <>
Date: Thu, 17 Nov 2011 18:36:30 +0100
Message-Id: <>
> Our computers are more special, ie. conform to the original spec is
> generally a "don't care" bit as long as the construction provides
> colors,


> Also, if someone creates a pattern of black and white stripes on the
> screen, one pixel of width each, he'll see a color gradient on top of
> the stripes on composite displays... As explanation, the pixel  
> clock of
> the PAL C64 is 16/9 the color subcarrier frequency. A series of black
> and white pixels is therefore a square signal whose base frequency is
> half that, in other words 8/9 of the color subcarrier frequency - very
> close, almost equal. This signal will definitely be catched by the
> chroma separator in the display, and get displayed as color. As this
> signal'd be constantly shifting in reference to the PAL burst  
> (since it
> is "slower" than that of PAL's nominal frequency), the result is a
> gradient of constantly changing color. From the proportion, we could
> also conclude that the gradient is periodic for 16 pixels.
> ...Now, imagine how that'd look like if the PAL reference phase was
> unknown, or constantly shifting... :-DDD

Someone should make some pictures, hint hint :-)


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Received on 2011-11-17 18:00:05

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