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PAL / NTSC


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#26 R0ger OFFLINE  

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Posted Fri Mar 2, 2018 9:46 AM

Btw. I would need someone to test some minor piece of software on real hardware NTSC. Somebody who is online often, and is really willing to do it. I will bother you. You'll be sorry in the end. Ideally someone who can test both CRT and LCD. I will also want photos of the screen so I can compare the colors. I offer nothing. Possibly mention in credits. Also under strict NDA, as it's supposed to be surprise, right ? :-D

 

Ps. not you emkay. Sorry but you English is sometimes way hard to understand  :skull: 



#27 _The Doctor__ OFFLINE  

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Posted Fri Mar 2, 2018 10:02 AM

Rescue becomes real? :) Move from tech demo to game play? That of course could not be as it is a new super secret NDA wrapped mystery.

 

Very exciting!



#28 MrFish OFFLINE  

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Posted Fri Mar 2, 2018 10:19 AM

Pixel aspect ratio is an inexact science.  The old CRTs varied widely, even some PAL TVs only barely show the 240 scanline normal display area.

 

And even plenty of LCDs cut off overscan.  It does seem ridiculous but in some cases even though you've got a 1920x1080 panel the pixel mapping isn't 1:1.  Especially if you're using an analog input type which = anything short of HDMI.  Generally it'll be remapped such that you're not seeing the full display.

 

It's an exact (enough) science when both systems can be compared on the same monitor.

And the results shown here from Altirra are demonstrating the difference more than accurately

enough to draw the conclusions stated.

 

 

But that said, it's a long known fact that the NTSC hires pixels are stretched vertically, the PAL ones are almost square.

 

It's not my point to say that -- as I know it's common knowledge -- but rather "as a result of

that known fact" NTSC systems can utilize a character set defined in an 8x8 grid to display

characters that have a desirable height to width ratio, whereas PAL systems would need

to utilize an 8x10 character definition grid in order to have characters of similar desired

dimensions -- which maybe isn't such a long known fact.

 



#29 R0ger OFFLINE  

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Posted Fri Mar 2, 2018 10:26 AM

Rescue becomes real? :) Move from tech demo to game play? That of course could not be as it is a new super secret NDA wrapped mystery.

 

Very exciting!

 

Sorry to disappoint. I said 'minor'. It's just an intro for our discmag. It's not like the intro is not cool though ..

The discmag used to be Czech only, so NTSC was not an issue. We're trying to include English articles this time, so even if some of the binary entries might not be NTSC compatible, it would be nice if at least the intro and the text reader was compatible.


Edited by R0ger, Fri Mar 2, 2018 10:27 AM.


#30 flashjazzcat ONLINE  

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Posted Fri Mar 2, 2018 10:34 AM

The notion that an 8x8 character cell is "more pleasing" on a vertically stretched NTSC display is completely subjective. Another way to achieve the same aspect ratio in PAL is to to mess with the VSize control on a CRT monitor, which will also turn all circles into nice ellipses. :) Of course the A8 has a 10x8 character mode built in, should one need it.

But I like my pixels square, which isn't to say that I dislike the way everything looks in NTSC. I just dislike the way circles come out, and I won't even bother posting the results of GR.8: COLOR 1: CIRCLE 50,50,50 on an emulated NTSC machine.

#31 landgraf OFFLINE  

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Posted Fri Mar 2, 2018 10:46 AM

Out of curiosity, did Atari also produce 8-Bits with PAL-M video chips (like for the Brazilian market)?

At least in theory they should give you the best of both worlds, 60 fps and the almost 20% extra vblank-cycles.



#32 MrFish OFFLINE  

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Posted Fri Mar 2, 2018 11:06 AM

The notion that an 8x8 character cell is "more pleasing" on a vertically stretched NTSC display is completely subjective. Another way to achieve the same aspect ratio in PAL is to to mess with the VSize control on a CRT monitor, which will also turn all circles into nice ellipses. :) Of course the A8 has a 10x8 character mode built in, should one need it.

 

I said "desirable" not "more pleasing". And what I mean by desirable is something that more closely emulates what can be seen, for instance, in the fonts we're using to respond to each other on this forum. So, what I'm saying isn't entirely subjective.

 

I suppose you could mess with the vertical size on a PAL monitor, but most people probably aren't going to do that.

 

Yes, the 8x10 mode can help -- although it only affects descenders, which is just part of the problem.

 

 

But I like my pixels square, which isn't to say that I dislike the way everything looks in NTSC. I just dislike the way circles come out, and I won't even bother posting the results of GR.8: COLOR 1: CIRCLE 50,50,50 on an emulated NTSC machine.

 

There are plenty of benefits of square pixels, and drawing circles is one of them (although ellipses can easily compensate on NTSC). I'm just trying to show some of the benefits of NTSC's oblong half-color clock pixels.


Edited by MrFish, Fri Mar 2, 2018 11:32 AM.


#33 flashjazzcat ONLINE  

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Posted Fri Mar 2, 2018 12:08 PM

I thought the desirable aspect ratio would be the more pleasing one, but maybe it's less pleasing. As for drawing ellipses to compensate for AR variations: it's not so easy to change - say - the circular system information icon in the U1MB BIOS setup menu so it doesn't look elliptical on an NTSC display. Stuff drawn on the fly - sure: run all your drawing program's rubber-banded circles through a fixed vertical divider to account for non-square pixels, if you absolutely must. But the matter remains entirely subjective (and not just a bit subjective, which is what it would be if "not entirely subjective") until I can be convinced that the supposed benefits of non-square hi-res pixels are empirical. Right now, I'm hearing that one guy prefers tall characters and is willing to program his way around elliptical circles in those instances where it's even possible to do so before the proportions become fixed.


Edited by flashjazzcat, Fri Mar 2, 2018 12:09 PM.


#34 MrFish OFFLINE  

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Posted Fri Mar 2, 2018 12:33 PM

I thought the desirable aspect ratio would be the more pleasing one, but maybe it's less pleasing. As for drawing ellipses to compensate for AR variations: it's not so easy to change - say - the circular system information icon in the U1MB BIOS setup menu so it doesn't look elliptical on an NTSC display. Stuff drawn on the fly - sure: run all your drawing program's rubber-banded circles through a fixed vertical divider to account for non-square pixels, if you absolutely must. But the matter remains entirely subjective (and not just a bit subjective, which is what it would be if "not entirely subjective") until I can be convinced that the supposed benefits of non-square hi-res pixels are empirical. Right now, I'm hearing that one guy prefers tall characters and is willing to program his way around elliptical circles in those instances where it's even possible to do so before the proportions become fixed.

 

It's a fact that NTSC characters are ~2 (PAL pixels) taller than PAL characters.

 

It's a fact that the taller characters produced on NTSC systems more closely emulate the vast majority of general purpose fonts.

 

My opinion that it's desirable to more closely emulate general purpose fonts is subjective.


Edited by MrFish, Fri Mar 2, 2018 12:37 PM.


#35 Rybags OFFLINE  

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Posted Fri Mar 2, 2018 5:38 PM

PAL-M is also 525 lines so wouldn't benefit from 60 frames and more cycles.

What Atari did for that market?  Not sure, but I think I remember reading that their TVs were usually multi-standard so they probably used NTSC machines.



#36 Rybags OFFLINE  

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Posted Fri Mar 2, 2018 5:42 PM

The sawtooth wave generators on dual standard CRTs won't necessarily adjust such that 50 and 60 Hz display the proper aspect in relation to each other.

Note that the horizontal rate on NTSC is greater which would mean even more speedup needed.

 

Doing the maths, 312 vs 262 gives a ratio of 1.1908 PAL to NTSC, which is near enough to 20%

So if the monitor did adjust properly that should mean NTSC characters being about 1.5 pixels taller.



#37 Level42 OFFLINE  

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Posted Fri Mar 2, 2018 6:51 PM

 

Indeed. I'm not used to 50 Hz flicker anymore either. But it's the age of LCDs. Flicker is not an issue.

 

Yugh. Flicker not. Lag is. Not to mention non-black blacks....ghosting etc. etc. etc.


Edited by Level42, Fri Mar 2, 2018 6:53 PM.


#38 MrFish OFFLINE  

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Posted Fri Mar 2, 2018 7:47 PM

Doing the maths, 312 vs 262 gives a ratio of 1.1908 PAL to NTSC, which is near enough to 20%

So if the monitor did adjust properly that should mean NTSC characters being about 1.5 pixels taller.

 

Actually, I was thinking about this again, earlier today, when I was setting up some custom pixel aspect ratios in Photoshop for NTSC and PAL, and 2 pixels started seeming (and looking) like it was too much. I just realized too that Altirra clips NTSC to 220 pixels (when overscan is set to "Normal") for an approximate realistic look that you get on a CRT monitor. This was probably causing NTSC to be over scaled in comparison to PAL.

 

So, your calculation makes sense and I'd say it's a correct approximation. NTSC characters are still quite a bit taller, but not as much as shown in the image I posted. As I mentioned in my first post about it, I expected the difference to be somewhere between 1 and 2. I don't think there's a way to have Altirra show 240 lines for NTSC, but I can easily do the scaling in Photoshop to get a better visual.


Edited by MrFish, Fri Mar 2, 2018 8:29 PM.


#39 phaeron OFFLINE  

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Posted Fri Mar 2, 2018 11:43 PM

Line counts isn't the way to compute aspect ratios. Convert dot clocks to pixel aspect ratios for each standard and then compare the pixel aspect ratios.

 

The PARs for the Atari dot clocks are 0.857:1 for NTSC and 1.0396:1 for PAL. The ratio between those is 1.213.



#40 _The Doctor__ OFFLINE  

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Posted Sat Mar 3, 2018 7:55 AM

LPI, or lines per inch, or the metric equivalent is also a function of the display. You can have more lines in less space or less lines in more space. Phaeron is correct in posting  dot clock to pixel ratio and comparison to pixel aspect ratio as this ends up being a three layer cake to some degree.

 

There is a fudge factor also, as a display running outside of it's country origin can also have it's output affected by it's power source. All things being equal. A side by side comparison using everything at reference levels still yields some stretching or shrinking but not to the great exaggerations we express here. Now when we use mixed systems and mixed software with mixed displays or can end up being extremely out of aspect. This is common back then as it is now. Multi mode even on today's lcd monitor don't get it correct either. My Samsung digitally masks the first few scan lines and lest few scanlines of my display in pal mode... I loose an entire line of text... no reason for it but that's what it does....plenty of panel left to do so...


Edited by _The Doctor__, Sat Mar 3, 2018 7:56 AM.


#41 landgraf OFFLINE  

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Posted Sat Mar 3, 2018 8:38 AM

PAL-M is also 525 lines so wouldn't benefit from 60 frames and more cycles.

Ah yes, you're right. Seems like I have mixed up the line count with PAL-N, which is only 50 fps, however.



#42 Level42 OFFLINE  

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Posted Thu Mar 8, 2018 4:48 PM

Ah well.... soon enough we can have both in one machine.....

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#43 Bryan OFFLINE  

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Posted Thu Mar 8, 2018 5:21 PM

Ah well.... soon enough we can have both in one machine.....

I built something like that once. I kept meaning to go back and simplify it but never did.



#44 Bryan OFFLINE  

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Posted Thu Mar 8, 2018 5:23 PM

I'm stubborn, and keep my A8 gear on a Sony PVM.  They just look so much better on CRT.  I guess to be fair - I do have an Eclaire beta board, so I have a valid way of using PAL or NTSC via HDMI.  But I try to stick to vintage gear.

 

Yeah, to me a CRT is still the standard for how something should look. I've noticed that the prices of the better CRT TVs (mostly Trinitrons) is starting to go up as well.



#45 _The Doctor__ OFFLINE  

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Posted Thu Mar 8, 2018 5:27 PM

The still litter the streets people dump them on the side of the road all over the cities of America...



#46 Rybags OFFLINE  

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Posted Thu Mar 8, 2018 5:37 PM

They throw them out of apartment windows in NYC...

 

"Hey you freakin' doit-bag!  Get a tube TV up yer ass!"



#47 AW127 OFFLINE  

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Posted Thu Mar 8, 2018 5:41 PM

The PAL / NTSC problem is a big thing with nearly ALL retro-machines (computers/consoles) and besides the debate which format is technically better, there are the facts, which are the software-releases.

 

And here it can be said, that:

 

- PAL dominates on retro-computers like C64 and Amiga and also in the overall Demo-Scene

- NTSC dominates on the most retro-consoles (SNES/Megadrive/NES/Atari-VCS and so on...)

 

With "dominates" i mean, that the better releases came out on this system. When you have a NTSC-C64 you often have incompatibility-problems with certain software or speed-problems with games which runs not in the correct speed. Some games feel strange, cause they run in a speed they were not programed for. So here are the NTSC users the unlucky persons.

 

Exactly the same problems vice-versa, when you have for example a PAL-Megadrive. "Sonic the Hedgehog" for example, feels like in slowmotion on a PAL Mega-Drive. Here are the PAL users unlucky. Same is on the Atari VCS-2600. Some games are speed-adapted and run in the same speed as the NTSC-originals, but sadly the most not. Luckily their exists over 200 PAL60 versions of the games in the meanwhile, which also can be used, but you need something like the Harmony-cart then. Then the speed and border problems are gone on PAL Atari`s.

 

When it comes to the DEMO-scene, cause this was mentioned before in the thread, then it must be said, that PAL dominates here. Even on the Atari 2600 it`s this way. Seems like most demo-groups are in Europe.

 

Normally all games on all systems could be adapted to run in same speed on NTSC and PAL computers or consoles, but the most companies seems to had no interest to make this effort. So the most games was not adapted. Not good for all users in the world, that different systems exist. But it is like it is. For SECAM users its even more worse.   :)


Edited by AW127, Thu Mar 8, 2018 5:48 PM.


#48 mytek ONLINE  

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Posted Thu Mar 8, 2018 6:07 PM

Ah well.... soon enough we can have both in one machine.....

 

How's that project coming? Looking good  :) .

 

I pretty much stay with a PAL setup in my 1088XEL's, even though I live in NTSC country. And thank's to Simius's boards such as the Sophia RevC (DVI), monitor choices for running PAL are getting better over here.



#49 Level42 OFFLINE  

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Posted Fri Mar 9, 2018 1:43 AM

Having a couple of proto's running. It has been demonstrated during Atari Invasion a few weeks ago. The boards that work just do that: work. No issues.

But (probably due to my SMD soldering skills) I have a number of proto's that don't work at all or just with one ANTIC...

Because of this (and to be sure every production board will run fine) I designed a test-PCB which I need to populate with 80 (!) LEDs....this will allow testing the PCB's in a very short time without having to put them in a real machine.

 

I'm looking into having the SMD soldering done in China for the production models.....:)



#50 Rybags OFFLINE  

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Posted Fri Mar 9, 2018 2:11 AM

Will there also be an Antic companion board?

 

Here's an idea - how about a GTIA board that intercepts reads to the PAL register and allows you to force whatever value you want (so retain your own system's GTIA and fool software into thinking you have the other)






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