NTSC vs PAL vs SECAM

[+SpiceWare]

I've created a page Atari NTSC vs PAL vs SECAM and would appreciate any feedback.

[CPUWIZ]

Cool, don't like the color scheme though.

 

If anyone in their respective country, is confused about what television standard they have, take a look here...

 

http://www.kropla.com/tv.htm

[+Wonder007]

great link CPUWIZ...

[alex_79]

I've created a page Atari NTSC vs PAL vs SECAM and would appreciate any feedback.

You could add that the "TV TYPE" switch on SECAM vcs actually affects the video signal (enabling or disabling colors), while its behaviour in NTSC and PAL consoles is determined by software; games that require that switch (Secret Quest for example) aren't playable correctly on SECAM consoles.

[+SpiceWare]

Yeah, the color scheme is left over from my old site. One of these days I'd like to learn CSS and revamp it.

 

Good idea on the TV TYPE - I'll work something in for my next update.

[A.J. Franzman]

Darrell,

 

Excellent page, does a good job explaining everything in a simple way that should be good enough for most Atari players and collectors. There's only one minor detail that's technically incorrect, but to go into the minutiae needed to make it right would probably be confusing and unnecessary: you say that each system displays 60 or 50 "frames" per second when the correct terminology is "fields". I can't think of an elegant way to improve what you've written though, so you should probably leave it as-is.

 

On the other hand, I've sent the owner of the World TV Standards page on kropla.com some corrections about his "60 vertical lines" and similar errors found in his descriptions of all three major standards.

[oldric]

When you see these horrible SECAM colors you understand why i let my SECAM Darth vader in his box and only play with my PAL RGB 7800.

 

Could be fine to have a NTSC one but can't find any games in Europe...

[SeaGtGruff]

you say that each system displays 60 or 50 "frames" per second when the correct terminology is "fields".

If you want to get a little more complete and precise, here are some *approximate* numbers:

 

+------------------+-----------+-----------+------------+------------+
|  Display Format  | Lines per | Lines per | Frames per | Fields per |
|				  |   Frame   |   Field   |   Second   |   Second   |
+------------------+-----------+-----------+------------+------------+
|	NTSC TV-B&W   |	525	|	262.5  |	30	  |	60	  |
|	NTSC TV	   |	525	|	262.5  |	29.97   |	59.94   |
|	NTSC 2600	 |	262	|	262	|	59.92   |	59.92   |
|	NTSC 2600-i   |	525	|	262.5  |	29.90   |	59.81   |
|   PAL60 2600	 |	262	|	262	|	59.38   |	59.38   |
|   PAL60 2600-i   |	525	|	262.5  |	29.63   |	59.26   |
+------------------+-----------+-----------+------------+------------+
| PAL/SECAM TV	 |	625	|	312.5  |	25	  |	50	  |
| PAL/SECAM 2600   |	312	|	312	|	49.86   |	49.86   |
| PAL/SECAM 2600-i |	625	|	312.5  |	24.89   |	49.78   |
+------------------+-----------+-----------+------------+------------+

Notes:

 

All values showing two decimal places have been rounded to two decimal places. To calculate the exact values, use the formulas given below.

 

NTSC, PAL, and SECAM represent different methods of encoding *color* into the signal (with the exception of the old black-and-white NTSC format). There are actually several "TV systems" that use one color encoding method with a different number of lines, such as using PAL color-encoding with 525 lines. The values given above represent the "standard" systems in which NTSC has 525 lines, and PAL/SECAM has 625 lines. Black-and-white NTSC (or "NTSC-I") is no longer used (except in monochrome security monitors?), and is given above only for comparison purposes.

 

Atari 2600 game screens can vary as far as the number of lines in the display. The values shown above are for the "standard" screen sizes.

 

The "2600-i" values shown above are for game screens that use interlacing to get either 525 or 625 lines per frame. There might not be any homebrew Atari 2600 games that actually use interlacing, but the interlaced values have been given for comparison purposes.

 

PAL60 games are played on PAL 2600s and displayed on PAL TVs, but the PAL60 values have been grouped with the NTSC values for comparison purposes.

 

The following formulas can be used to calculate the exact values:

 

NTSC cc = NTSC color clocks per second = 227.5 * 262.5 * 60 * 1000 / 1001.

NTSC 2600 frame rate = NTSC cc / 228 / lines per frame,

where "lines per frame" = 262 (non-interlaced) or 525 (interlaced).

 

PAL cc = PAL color clocks per second = 283.7516 * 312.5 * 50.

PAL 2600 frame rate = PAL cc * 4 / 5 / 228 / lines per frame,

where "lines per frame" = 312 or 625 (PAL50), or 262 or 525 (PAL60).

 

The SECAM method alternates between 282 color clocks ("red") and 272 color clocks ("blue") per line, but PAL and SECAM 2600s divide the screen into 228 "Atari color clocks," so the SECAM 2600 frame rates are identical to the PAL 2600 frame rates. If "SECAM60" games can be displayed on SECAM TVs, then the "SECAM60" frame rates would be identical to the PAL60 frame rates.

 

For interlaced 2600 screens, the field rate is 2 * frame rate.

 

Michael

[supercat]

A few minor little additions with regard to fields and frames:

 

In standard NTSC video, each field has 262.5 scan lines precisely; the fields are paired off into frames, where the first field of each frame ends with a half scan line and the second field starts with a half scan line. Note that there were some video chips that tried to do interlacing by alternating fields of 262 and 263 scan lines; this will generally give poor results.

 

The 2600 considerably simplifies the standard waveform, and generally outputs standalone fields that neither begin nor end with a half scan line. Each such field can be considered a frame in and of itself.

 

Doing interlacing properly is actually a bit tricky. The way a television or monitor works, every time the video signal level falls goes below a certain threshhold (which is set a bit below the blanking level) and the electron beam is more than about 2/3 of the way across the picture, the beam will sweep back to the left. If the signal is below the sync threshhold most of the time for a scan line or two, and the beam is more than about 2/3 of the way down the picture, the beam will sweep upward.

 

If normal horizontal sync pulses were running before the vertical sync pulse, then half of the vertical sync pulses would start at the same time as a horizontal sync pulse, while half would start a half scan line later. This difference in timing could affect how long it takes to detect the pulse. To avoid this problem, broadcast video sends out what are called equalization pulses shortly before the start of vertical sync. These occur twice per line (half of them match up with ordinary horizontal sync pulses) and thus the signal preceding the vertical sync pulse will be the same on both even and odd fields. The number of equalization pulses will be different, but that won't affect things too much.

 

All this is primarily relevant if one is trying to implement interlacing "properly" on the 2600.

 

BTW, has anyone with a PAL 2600 played around to figure out that exact circumstances cause chroma loss?

[+SpiceWare]

If you want to get a little more complete and precise, here are some *approximate* numbers:

Yeah, I'm into video(bought an S-VHS back in 87 or88, HDTV in 01) and know frames vs fields and that it's not exactly 50 or 60 per second. I just figured that was way too in depth for somebody wondering "why the games look so different" or play slower/faster on their Atari. I think I'll add a footnote and link to something elsewhere for those who are interested in it.

Edited April 29, 2007 by SpiceWare

[+SpiceWare]

Cool, don't like the color scheme though.

I redid the page using an "atari orange" color scheme using this online tool and FF9000 for orange.

 

Not sure if I like it, but I think it looks better than the bright yellow I used to have.

 

Hmm - going to have to decide what to do about my old site - Road Runner is now ComCast in Houston, that site will be going away in the future.

[SeaGtGruff]

I redid the page using an "atari orange" color scheme using this online tool and FF9000 for orange.

I like the orange on the side, but the blue letters don't look all that great against the light orange background. Try making it lighter, maybe FFE4C0.

 

Michael

[+SpiceWare]

updated the page with the lighter orange, you may have to refresh the page for it to show up. Also added reviews to my Medieval Mayhem page.

[potatohead]

Has interlacing been done on the 2600. Full on ~400 lines vertical?

[SeaGtGruff]

updated the page with the lighter orange,

Yep, I think the lighter shade works better, what do you think?

 

Michael

[SeaGtGruff]

Has interlacing been done on the 2600. Full on ~400 lines vertical?

Yes, there are some examples that were posted in the Stella list some years ago, although I haven't tried running any of them on a real 2600 and TV.

 

Michael

[+SpiceWare]

I like it better too, think maybe the blue should be darker but will do that next updated.

 

I tried the interlace demo on my VCS when it was released - google - by Glenn Saunders

 

I just ran it - here's photos of even, odd and interlaced.