Re: [stella] Number of Scanlines

[Glenn Saunders <cybpunks2@xxxxxxxxxxxxx>]

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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