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2016-12-12 00:26

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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2017-06-15 09:01

ptoing

Registered: Sep 2005
Posts: 271

Noticed a small bug with the delay line stuff as far as U only goes. I have a 1084S and solid colors display hanover bars, but when mixing luma pairs they get pretty much eliminated.

So in Joe's "Playing With Colors 2", the light red/green mixes look nothing like that on a real 1084S, they are much more uniform, pretty much like with the "on U only" thing off.

2017-11-05 18:00

pepto
Account closed

Registered: Nov 2004
Posts: 35

Quote: Noticed a small bug with the delay line stuff as far as U only goes. I have a 1084S and solid colors display hanover bars, but when mixing luma pairs they get pretty much eliminated.

So in Joe's "Playing With Colors 2", the light red/green mixes look nothing like that on a real 1084S, they are much more uniform, pretty much like with the "on U only" thing off.

Thanks for noticing!! This really gave me some sleepless nights, since mid-june... ;P

I have a fix coming... \o/ it really only affects hanover-bars for certain color-combinations (like the red/green you mentioned) when not having delayline for both U and V).

"Play With Colors 2" is by Ed of Wrath Designs btw, not Joe...

I spent the whole day comparing the 1084S to the output of experimental colodore-versions and I think that I finally found a solution that looks very similar to the real thing. It seems that the "transparency" of the effect that the delayline of the V signal creates, is dependant on the phase of the color-angle.

I'm not sure how this translates to electronics though... O_o ...like U has a solid delayline-effect in monitors like the 1084S, but V's delayline-effect is only visible the more you get away from the center of the V-axis? It certainly looks like it, but where's the logic in that? Is this some weird way to multiplex two signals into one delayline or some signal-bleed crosstalk?

This is basically what I have now, in pseudo-code:

delayLine_v[ x,y ].alpha = parseInt( Math.abs( Math.sin( screenPixel[ x,y ].colorAngle ) * 0xFF ) );

My current implementation is full of debug-output in weird places though. I will tidy this up and write a small section about it on the website before the year is over (unfortunately I'm a lil' busy at work right now)... just wanted to give you a heads-up...

2017-11-06 01:32

ptoing

Registered: Sep 2005
Posts: 271

Nice, glad to be of help :)