Re: [stella] Number of Scanlines

Subject: Re: [stella] Number of Scanlines
From: Glenn Saunders <cybpunks2@xxxxxxxxxxxxx>
Date: Sat, 07 Dec 2002 11:37:03 -0800
Regardless of the total number of lines, you have to decide how many active scanlines you are going to have.

It's like when you do most NTSC to PAL conversions you are padding the screen with black lines, basically letterboxing the screen, because PAL screens are a little taller than NTSC...

Even without that, an NTSC signal has a lot of scanlines it is technically generating that your monitor doesn't see. A classic example of that is closed captioning which is on scanline 21.

It's a REAL scanline, but regular TVs aren't designed to display it.

Now, how many scanlines TVs do display varies from TV to TV.

When the VCS was first being designed, Larry Wagner studied TVs that were on the market at the time to measure how much they displayed, both vertically and horizontally. Atari hadn't had to do this before because in their coinop division they used their own monitors and could calibrate them as they wished.

They had to develop a standard safe-area for the 2600.

That's where the magic 192 scanlines count comes in. This has nothing to do with the NTSC spec. It's just a best-practice. Other companies chose other values for their systems. Atari was more conservative than most.

That's why the Atari 8-bit gives you 24 rows of 8-bit characters per screen.

TV manufacturers in the mid 80s started to change manufacturing processes and from then onwards. As you may know, TVs were rounder in the 70s. Even if the scanlines beyond 192 might be visible on older sets, they'd get cropped near the edges due to the cowling around the tube or the general roundness of the tube itself. On the TV I was using with my XL in high school only the very edges of the display were cropped when I did 200 scanlines.

Modern tubes are even squarer, and are calibrated to show a few more scanlines anyway (the VERTICAL SIZE attribute of a TV set).

This is of course a matter of debate, but I've personally set a 200 pixel rule for myself. 192 is too limiting. The 2600 resolution is so low that those extra 8 scanlines can really come in handy to help expand your main playfield by pushing the score displays further to the top/bottom of the screen, and on an 8-bit you get a whole extra row of characters to play with that way.

You can probably go all the way to 204 or so depending on how bold you want to be.

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