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That's the entire basis of PAL. Rather than have the hue adjustment like old NTSC TVs, PAL (Phase Alternating Line) transmits the (R-Y) component for each line with opposing phase, then circuity at the receiving end averages them out.

 

I believe in the old days they used a quartz crystal to create the necessary delay.

 

Ed: according to my ancient "How it Works" encyclopedia:

 

The delay device is usually a glass block and the delay is achieved by propogating ultrasonic waves through it.

Edited by Rybags
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so if the PAL color mixing is done in the PAL decoder I still wonder how it is done..the TV or monitor should have some memory or signal delay circuit to produce the mixing of colors on consecutive scanlines....How is it done??

PAL encoding works as follows: You have three signal Y, U and V. Y is the luminance, U is the color distance for blue to yellow, V is the color distance for red to cyan.

 

Now Y is basically just a black and white signal. U and V need to be encoded on top of it to allow b/w TV sets to display a picture but still have color information which can be decoded. U and V are simply encoded in a 4.43 MHz color carrier which is added to the Y-signal (or for seperate video it isnt added).

 

The color carrier C is simply a 4.43 MHz sinus signal with amplitude U+V on even rasterlines and U-V on odd rasterlines. Getting back U+V or U-V is simple: Simply get the amplitude. But how to get U and V again? Well, that's simply done by adding/subtracting the color carrier of the previous rasterline with the one from the current rasterline, so you get 2*U = (U+V) + (U-V) and 2*V = (U+V) - (U-V). But to do this, the decoder needs to keep the color carrier signal of the previous rasterline, and thats done in a so-called "delay loop" which delays the signal for the time of a rasterline. That's also what made PAL a bit more expensive than NTSC in the beginning and NTSC advocates said that PAL means "Pay for Added Luxury" :)

 

Anyway, since the color carrier of two rasterlines is mixed, you get a 50:50 mix of the color tone of two rasterlines, so if you alternate mode 9 lines and mode 10 lines, you can mix a plain luminance signal with a plain chrominance signal :)

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thx frohn&rybags

 

Ed: according to my ancient "How it Works" encyclopedia:

 

The delay device is usually a glass block and the delay is achieved by propogating ultrasonic waves through it.

 

these must be very highpitched waves then...if it's a soundwave propagating through a crystal

 

but indeed, silly I didn't think of that...electromagnetic waves propagate at 2/3 of the speed of light (through copperwires), so a delay line in a wire must be about 12 kilometers, but with soundwaves it's a lot shorter ;) ...with a soundpulse in a crystal it's in the order of 10^-2 meters

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  • 3 months later...

what i would suggest is a bigger "overall" usage of pc native screen resolution... it seems that tebe is using the great tool on a 640x480 pc/laptop but on a 1280x resolution i personally find that the tool is very "small". so actually a scalable "windows like" GUI would be great... ;)

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  • 6 months later...
  • 4 weeks later...

I just noticed Graph2Font 3.8.5.6 was released today :)

Tezz

 

http://g2f.atari8.info/

 

I think the update information roughly translated is as follows:

 

Current version MADS added 1.8.0

Optimization of ASM, if picture has unused PMG the data is not recorded

Boosted degree of file compression G2F zcDefault zcMax

Edited by Tezz
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I would prefer Tebe to increase the main window size... running G2F on a 1280x1024 or higher monitor resolution is not fun... ;)

 

but did i missed the XEX folder last time? there are additional examples with some music tunes?

Edited by Heaven/TQA
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I would prefer Tebe to increase the main window size... running G2F on a 1280x1024 or higher monitor resolution is not fun... ;)
Me too! It would be much better if it was scalable or I would like to see more tools available in zoom mode. Either would be a great addition.
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  • 1 month later...

I want to use G2F to convert 160x192 4 colors images from .bmp to .mic.

Is it possible with this program to save files 7680 bytes long only (160x192 pixels not 160 x240)?

 

Another noob question:

Is it possible to add 4 bytes with the 4 colour values?

Edited by Philsan
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  • 4 months later...

I visited Fandal's site yesterday. G2F is still alive :) ...a whole bunch of new pitcures appeared.

 

I especially like the HiRes picture named 'dizzy 3', by an unknown G2F artist. You can see it below.

 

I wonder if this could be extended to a real working game engine, maybe even with some scrolling???

 

Here is the executable:

 

http://atari.fandal.cz/detail.php?files_id=5804

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Since the game doesn't really have that many moving objects, I reckon hires + underlays would work.

 

That implementation actually works well - usually I don't like the look of most hires + underlay pics.

 

Scrolling would introduce a whole set of headaches though - although in the context of the game itself, scrolling isn't really a critical feature.

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I especially like the HiRes picture named 'dizzy 3', by an unknown G2F artist. You can see it below.

 

Picture created by Gonzo. I like it very much, too. Just few days ago there was a news about it on atari-online.

http://www.atari.online.pl/v01/index.phtml...&ct=nowinki

 

 

I think that scrolling is not necessary, because most of the Dizzy games didn't support it.

Edited by urborg
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I especially like the HiRes picture named 'dizzy 3', by an unknown G2F artist. You can see it below.

 

Picture created by Gonzo. I like it very much, too. Just few days ago there was a news about it on atari-online.

http://www.atari.online.pl/v01/index.phtml...&ct=nowinki

 

Translated from Polish to English using Google Translate. I agree, the Dizzy picture is great!

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