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Forums > CSDb Discussions > colodore is the new pepto
2016-12-12 00:26
pepto
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Registered: Nov 2004
Posts: 35
colodore is the new pepto

Hey guys, I remeasured the video-signals of my VIC-II's and slightly updated my 15 year old attempt at calculating an rgb-clone. While at it, I also measured VIC & TED and made a little website about it, that allows you to adjust brightness, contrast and saturation as you like and then save your own custom palette to a png-file.

http://www.colodore.com


I took extra care to make sure, that the brightness, contrast and saturation sliders behave the same way as my 1084s.

While closely comparing my LCD to the 1084s, I found that making the transparency of scanlines dependent on YUV's Y (so they are less visible for brighter colors) looked a lot more like the real thing. I also noticed that the phase-shift on odd-lines happens for YUV's V only and there's even a name for it in video-lingua: hanover bars.

After implementing this, I'm happy to say that the images on my LCD and 1084s are remarkably close.


I will write a more detailed article about it in January, but seriously need a christmas-break first...

Cheers,
pepto
 
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2017-02-18 21:07
pepto
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Registered: Nov 2004
Posts: 35
Quoting pepto
You are correct, a delay-line would be the weapon of choice to suppress hanover bars, but they are a clearly visible artefact, along with delay-line style vertically blended chroma.

Oh snap, the 1084s seems to have a delay-line for YUV's U only. This explains a lot of things, especially why the phase-offset for YUV's V still is perfectly visible on screen after passing the delay-line and why more modern TVs manage to hide the hanover bars so much better, as they delay-line both YUV's U & V...


Quoting pepto
I have a first idea on how to get "play with colors" to blend right. I have a feeling it's something simple. I will try to find some time this weekend to investigate.

The solution is simple indeed. I have an internal version of colodore.com now, that renders every single field of "play with colors 2" precisely like the real VIC II and solid single-colored fields still look identical to the original version... \o/

I will try to find time tomorrow to tidy up my code, update the website and tell you how it appears to work tomorrow.
2017-02-19 08:38
pepto
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Registered: Nov 2004
Posts: 35
Considering how important it is, that a color ends up on an even or odd line, for this effect to work: Is the first line of the 200 line high main-field (without borders) considered an even or odd line, if you start counting at 1?
2017-02-19 08:46
chatGPZ

Registered: Dec 2001
Posts: 11088
you can scroll it.... so... :) i think you should start counting from the actual first scanline
2017-02-19 08:51
pepto
Account closed

Registered: Nov 2004
Posts: 35
Quoting Groepaz
you can scroll it.... so... :) i think you should start counting from the actual first scanline


Yeah well... unscrolled, freshly booted C64... Vice shows 35 pixels of upper-border for me. But as far as I understand, the first line in Vice isn't the first scanline, right? Isn't Vice's view masked to a sane value to hide overscan?
2017-02-19 09:13
chatGPZ

Registered: Dec 2001
Posts: 11088
to bei honest.... not sure how exactly VICE determines that... alankila write those renderers, i just improved some bits here and there.

but isnt it just a matter of trying both options and check against a real monitor which one is correct? :)
2017-02-19 09:17
pepto
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Registered: Nov 2004
Posts: 35
Quoting Groepaz
but isnt it just a matter of trying both options and check against a real monitor which one is correct? :)


Yes, it's easy to check with a test-image like "play with colors 2", there are just two ways to do it... I just wanted to use correct terminology for variables, that's all... :)
2017-02-19 09:47
chatGPZ

Registered: Dec 2001
Posts: 11088
as said, count from the first actual scanline, then its obvious what is odd and what is even :)
2017-02-19 13:14
pepto
Account closed

Registered: Nov 2004
Posts: 35
I updated http://www.colodore.com

Changes:

- do hanover-bars before delay-line
- added option to delay-line YUV's U only -- 1084s style (default for now)
- added Ed's "Play With Colors 2" at bottom of image-list

None of the changes affect the palettes.


In order for hanover-bars to work correct, there's a phase-shift (hue-rotation) needed for both U & V of 22.5 degrees on even lines, and -22.5 degrees on odd lines, before going into the delay-line.

To check if you have the even/odd stuff in the right order, make sure that the two fields in "Play With Colors 2", look like this (greyish on left, greenish on right)...

2017-02-19 15:11
Oswald

Registered: Apr 2002
Posts: 5007
scanlines are too strong imho
2017-02-19 17:48
chatGPZ

Registered: Dec 2001
Posts: 11088
delay line only for U is interesting. i think 1701 does the same....

perhaps that finally explains why so many ppl complain about scanlines being too strong - they are used to displays that have delay line for U and V?
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