Re: Difference in luma-chroma delay of C64/C128 compared to standard S-video

Den Tue, 5 Sep 2017 14:38:40 +0200 skrev silverdr@wfmh.org.pl:
> 
> > On 2017-09-03, at 23:30, Mia Magnusson <mia@plea.se> wrote:
> > 
> > I fired up my old CRT TV and also a supposedly good DVD player
> > (Yamaha DVD-S1700), and my C128.
> > 
> > Here are some pictures. [...]
> > 
> > This is how my C128 looks on my modern Samsung plasma. I assume the
> > TV set notices a delay and takes a bad guess how to adjust to the
> > situation, making it even worse:
> > https://farm5.staticflickr.com/4394/36199906213_a74e676c9d_o.jpg
> 
> Having a look at this (the DVD stuff doesn't add any value here as
> its signal is probably way closer to the standard specs than what the
> computer gives) I would say:
> 
> a) you seem to have the colour shifted not only to the right but also
> down. You don't expect that adding some tens of metres of cable for
> chroma can fix this, do you?

I didn't even notice that. That's a PAL problem, the vertical resolution
of chroma is supposed to be half of the luma resolution within each
field so the TV probably doesen't really know how to handle the signal.
I guess that the CRT TV does some tricks here.

But I expect that tens of meters of cable would correct the horisontal
shift.

> b) I'd say you are rather lucky getting picture, which is that good.
> I recall my quest to get something even remotely palatable some time
> ago and all (six) but one were worse than yours.
> 
> The above is not to say that you should be happy with this picture.
> Surely not. What it is to say that we seem to be barking under the
> wrong tree here.

Well, although the signal from a C64/128 doesn't follow the standards,
there is no reason for not being able to decode the signal into a
perfect picture.

I haven't looked into how the picture looks with some s-video to hdmi
converter, if there even are any that has some mode especially made for
C64/128. If there aren't any such that gives a perfect picture there is
definitively room for one in the market IMHO.

I shall look into doing some more tests, i.e. getting a test picture
with all combinations of text color x on background color y and use
either just plain letters of perhaps checker patterns/stripes of
different width. That would probably make the timing issue more
visible. Or perhaps it's just to use a white background and display
text in different colors; red seems to be the worst.


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