How many viewable TV lines?

[SeaGtGruff]

This topic has come up once or twice in the past, but I'm not sure if there's been a definitive answer.

 

How many scan lines are viewable on most NTSC television sets? I know it's probably going to vary from set to set, and may depend on the age of the set, but I'm trying to get an idea of how many scan lines are reasonably safe to use for an Atari 2600 game screen (although this would also apply to an Atari 800 screen on a TV).

 

I should mention that only the central portion of the screen (96 color clocks wide) is being used for what I'm doing, so I'm not worried about lines that might get cropped at the ends in the corners of the screen. In particular, the numbers of scan lines I'm interested in are as follows:

 

240 lines?

 

224 lines?

 

208 lines?

 

I'm guessing that 240 lines would be pushing it-- that some sets might crop some of the lines at the top and/or bottom of the screen-- but I'd like to use 224 lines if it wouldn't be too unwise, otherwise I'll just go with 208 lines.

 

Does anyone have any firsthand experience with taller-than-usual screen displays on the Atari 2600, 7800, 5200, or 800? What's the largest number of scan lines that you've found to be reasonably safe?

 

MR

[mos6507]

Atari specified 192 at a time when TVs were rounder and more of the picture fell into overscan. By the early to mid 80s, TVs could easily display 200 pixels. You can go to about 208 usually with only the corners getting cut off on tube TVs. Anything over that and you are really pushing it.

[Thomas Jentzsch]

I suppose nobody has ever really tested those limits. Maybe you could write a small test program and ask some people for their results.

[SeaGtGruff]

I suppose nobody has ever really tested those limits. Maybe you could write a small test program and ask some people for their results.

I created a simple program last year for this, which displays 240 lines in a rainbow pattern. If you display it on your TV, you should be able to count the number of hues, multily by 8, and subtract for any lines that get cropped at the top or bottom. I would have done it differently today, as I now realize that a proper 240-line screen would (I think) have 4 VBLANK lines, then 3 VSYNC lines, then 15 more VBLANK lines, then 240 active lines, since there are 3 pre-equalizing lines before VSYNC, 3 post-equalizing lines after VSYNC, then 11 blanked lines after that, plus 1 more blanked line (the CC line), and then we can also blank the line that comes before the 3 pre-equalizing lines, so:

 

1 blanked before pre-equalizing

3 pre-equalizing

3 vsync

3 post-equalizing

11 blanked

1 more blanked (closed-captioning)

240 active

 

equals

 

4 blanked pre-vsync

3 vsync

15 blanked post-vsync

240 active

 

Anyway, here's a link to the program I did before. When I get home tonight I'll do another version that does the lines as above.

 

http://www.atariage.com/forums/index.php?s...st&p=937522

 

MR

 

PS-- I was googling last night, reading about the "safe title area" and "safe action area" in NTSC TV. From the sounds of those, it sounds like 192 lines (80% of 240) corresponds to the "safe title area," and the "safe action area" would be 216 lines (90% of 240)-- although I'm wondering if those guidelines are still good by today's standards (excluding people who are still stuck with really old, crappy TVs), or if they should be revised for today's TVs?

Edited October 17, 2006 by SeaGtGruff

[+FujiSkunk]

PS-- I was googling last night, reading about the "safe title area" and "safe action area" in NTSC TV. From the sounds of those, it sounds like 192 lines (80% of 240) corresponds to the "safe title area," and the "safe action area" would be 216 lines (90% of 240)-- although I'm wondering if those guidelines are still good by today's standards (excluding people who are still stuck with really old, crappy TVs), or if they should be revised for today's TVs?

 

Modern flat-panel displays (plasma, LCD, etc.) should display a complete picture. CRT displays, however, still tend to crop the edges. The 90% guideline is still a safe one to follow until all CRTs are extinct (which even now won't be happening any time soon).

[Heaven/TQA]

on 800 i intend to use 240 scanlines... so full "overscan"... you can not force antic to display more lines as the picture starts to roll...but 0-239 everything should fine...

 

and what about modern consoles? they display 240 scanlines as well? -->snes,megadrive,psone etc...

[Heaven/TQA]

ah... forgot to mention... i am a PAL guy...

[Rybags]

Most modern consoles should do 576 lines (or 480 on NTSC) or better.

 

Going by the standards I read in an article on Teletext, it seems we have 25 lines for Vertical Retrace, which leaves 288 lines for the display (sounds logical since DVDs are 576 lines).

 

From my experience with PAL gear, the older TVs will tend to crop some or all of the first 10 or so Atari scanlines, as well as not displaying most of the first character column of a GR. 0 display, and sometimes cropping part of column 2.

 

Newer TVs tend to be a lot better, in fact making our LMARGIN redundant. Scanlines tend not to be cropped either, in fact you can see several lines worth of the "permanently black" border which Ataris generate for PAL systems.

 

If I was to propose a "TV Safe" standard for the Atari 800, I'd suggest:

 

- avoid using the first and last 8-10 scanlines for any text or graphics which the user must be able to see.

- avoid placing text which the user must be able to read in columns 1 and 2 in a standard width display.

[Heaven/TQA]

yeah. most of the time i do not put important stuff in the borders but f.e. background gfx... i like this more than having black borders... same goes to my fave atari st games or demos which use overscan or amiga games...

[GameEngine]

yeah. most of the time i do not put important stuff in the borders but f.e. background gfx... i like this more than having black borders... same goes to my fave atari st games or demos which use overscan or amiga games...

 

 

My preference is exactly the same ie if it is not a productivity app programmer should go for the full screen.

 

For the owners of old TVs:

Waht a delight it will be when your new TV gives your old Atari a new dimention.

[Bruce Tomlin]

Most modern consoles should do 576 lines (or 480 on NTSC) or better.

That's only with interlace. Most older consoles are completely incapable of interlace, though the 2600 can apparently be tricked into doing it. So start by dividing those numbers by two. Then when you subtract 10% (5% per side), you get 240-24=216 as a realistic upper limit.

 

The big problem with overscan is that it isn't consistent due to manufacturing variances. And rotating a CRT by 90 degrees will shift the horizontal position because of the earth's magnetic field.

 

If you're going to use the extra scan lines beyond 192 NTSC, you really need some way to configure things so that the user can adjust the position and height. And most classic systems have a fixed vertical height anyhow.

 

And a modern system may very well refuse to display the first 22 lines, even with scan adjustment in the service menu, as that's where the closed captioning and other annoying stuff goes.

Edited October 31, 2006 by Bruce Tomlin

[jbanes]

Most modern consoles should do 576 lines (or 480 on NTSC) or better.

That's only with interlace.

The latest generation of consoles can use progressive scan to get the full 480p resolution. For the 360 and PS3, they're actually capable of generating a 720p and 1080p signal, respectively. (Realistically, very few PS3 games are likely to use 1080p.) The PS2, XBox, and GameCube all had 480p capabilities as well, but the latter had the feature removed to reduce manufacturing costs.

[Bruce Tomlin]

Most modern consoles should do 576 lines (or 480 on NTSC) or better.

That's only with interlace.

The latest generation of consoles can use progressive scan to get the full 480p resolution. For the 360 and PS3, they're actually capable of generating a 720p and 1080p signal, respectively. (Realistically, very few PS3 games are likely to use 1080p.) The PS2, XBox, and GameCube all had 480p capabilities as well, but the latter had the feature removed to reduce manufacturing costs.

However, progressive scan WILL NOT work over composite or S-video. You have to have to have component or digital (DVI/HDMI). You can get a TV set to up-convert 480i to 480p, but that's not the same.

 

Since this thread is about how much you can get for a 2600 game screen, mentioning modern consoles/connections is not useful.