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pepto
Account closed
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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chatGPZ
Registered: Dec 2001
Posts: 11350 |
oh it doesnt? i guess thats the problem with the vice renderer. are you sure it actually doesnt? does joes "play with colors" work correctly with your stuff? |
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pepto
Account closed
Registered: Nov 2004
Posts: 35 |
Quote: oh it doesnt? i guess thats the problem with the vice renderer. are you sure it actually doesnt? does joes "play with colors" work correctly with your stuff?
How do I know if it works? I'm actually cooking dinner right now, but I will look into this later... ;-) |
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chatGPZ
Registered: Dec 2001
Posts: 11350 |
Play With Colors 2 should look like this |
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pepto
Account closed
Registered: Nov 2004
Posts: 35 |
Quoting Groepazdoes joes "play with colors" work correctly with your stuff?
This is really interesting! I didn't know about this test before.
I would say 90% of the fields look correct (I'm comparing colodore to the real C64 on the 1084s) and this is because of delayline-style chroma-blending.
A few adjacent fields however, which only differ by one color being on even lines in one field and on odd lines in the other, blend differently on the 1084s compared to colodore.
Which means the color-generation described on http://www.pepto.de/projects/colorvic/ works just fine and also the delay-line on colodore, but the way I do hanover bars doesn't seem to work 100% yet, even though it looks like a perfect match on solid colored fields, so it definitely is the phase-shift on v, just like it should be.
I'm puzzled for the moment and need to get some sleep.
At which point do you guys inject hanover-bars into the signal in Vice? I do it after the delayline, that's why a field with (lgrn/yel) looks the same as (yel/lgrn) before the hanover bars are added. |
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chatGPZ
Registered: Dec 2001
Posts: 11350 |
VICE uses two yuv palettes, one for odd and one for even lines, and both go into the delay line stuff. this is pretty much required to get those mixed colors 100% right (hence my question before)
you could also use this little test image, it shows all the mixed colors - the important bit is that some of them are different depending on what colors are in odd and even lines. |
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ilesj
Registered: Jun 2012
Posts: 27 |
Quoting peptoAt which point do you guys inject hanover-bars into the signal in Vice? I do it after the delayline, that's why a field with (lgrn/yel) looks the same as (yel/lgrn) before the hanover bars are added.
Should it be the other way around? Your article links to this Wikipedia article https://en.wikipedia.org/wiki/Hanover_bars that says
Quoting wiki
To suppress Hanover bars, PAL color decoders use a delay line which repeats the chroma information from each previous line, and blends it with the current line
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pepto
Account closed
Registered: Nov 2004
Posts: 35 |
Quoting wiki
To suppress Hanover bars, PAL color decoders use a delay line which repeats the chroma information from each previous line, and blends it with the current line
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.
Something doesn't seem to add up in the crt-emu/video-signal portion (e.g. detached from the general palette color generation). I came to the same conclusion originally, but unfortunately reality still differs.
Quoting GroepazVICE uses two yuv palettes, one for odd and one for even lines, and both go into the delay line stuff.
Hmm, but shouldn't this cancel out hanover bars completely?
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. |
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chatGPZ
Registered: Dec 2001
Posts: 11350 |
Quote:Hmm, but shouldn't this cancel out hanover bars completely?
apparently not... they are only completely gone if the phase difference between odd and even lines is exactly 180 degr. |
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JackAsser
Registered: Jun 2002
Posts: 2014 |
Quote: Quoting wiki
To suppress Hanover bars, PAL color decoders use a delay line which repeats the chroma information from each previous line, and blends it with the current line
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.
Something doesn't seem to add up in the crt-emu/video-signal portion (e.g. detached from the general palette color generation). I came to the same conclusion originally, but unfortunately reality still differs.
Quoting GroepazVICE uses two yuv palettes, one for odd and one for even lines, and both go into the delay line stuff.
Hmm, but shouldn't this cancel out hanover bars completely?
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.
Keep me informed so that I can update the webgl-port. (will release soonish). |
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pepto
Account closed
Registered: Nov 2004
Posts: 35 |
Quoting JackAsserKeep me informed so that I can update the webgl-port. (will release soonish).
Cool! No worries, I will keep you updated... |
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