Re: Blurry picture

From: Segher Boessenkool <>
Date: Sat, 19 Nov 2011 11:40:03 +0100
Message-Id: <>
Hi again,

> This is how it looks in separate luma/chroma:

Yeah, nasty red/green bars every 16 pixels.

> And composite:

SHOCK!  That is AWFUL!

> The machine is a late 6569 based PAL C64 board (maybe 1986) in a flat
> box.

> I don't currently have a "good" explanation on why the checkboard
> patterns trigger colors. There's a 2-line averaging filter (a "comb
> filter") in PAL displays, that should average out any and all  
> colors of
> opposite phases. Adjacent rows of a checkboard are perfectly in
> "opposite phase". They still trigger colors - which shows that we  
> don't
> (yet) understand something.

Hrm, the colour signal from the VIC should be nil nada nothing, so all
the colour signal is that filtered luma stuff, right?  The luma signal
won't be nice steep edges, if you add two lines the signal won't be flat
I guess.  But dunno :-)

The colour signal on the composite is about as strong as you can get!

> Consequently,
> if color subcarrier was independent, the color artifacts around the
> edges would probably just also slowly change their colors with phase
> changes.

I don't want to imagine it, I get a headache already!



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Received on 2011-11-19 11:00:22

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