Re: Double hires mode color artifacts

[vladitx <vladitx@nucleusys.com>]

On Sep 11, 10:28 pm, Dirk Thierbach <dthierb...@usenet.arcornews.de>
wrote:
> Dirk Thierbach <dthierb...@usenet.arcornews.de> wrote:
> > Linards Ticmanis <ticma...@gmx.de> wrote:
> >> Here's a RGB color table that works well enough for this (derived from
> >> Fourier Analysis and the usual YUV-to-RGB formulas):
>
> >> static struct {
> >>        unsigned short  red;
> >>        unsigned short  green;
> >>        unsigned short  blue;
> >> } AppleIIColor[16]= {
> > [...]
> >>        {0x40,0x54,0x00},       /* Brown */
> >> };
>
> > While testing double hires, I noticed that this color comes out on
> > my monitor as some sort of olive green, and not brown. What's wrong?
>
> I've tried to do the Fourier projection myself, but I arrive at different
> values. Do you assume any phase shift between the square waves of the
> bit pattern and the sine/cosine base functions?
>
> - Dirk

I suppose there's phase shift between the colour reference mixed into
the NTSC signal and the video data. They come from the same master
clock, but pass through different gates. Can somebody measure this on
a real Apple?
Any angle like this should be taken into account.

Linards, have you tried adding some small angle phase shift and see
what happens to the problematic colour?