New development: GTIA in CPLD

[_The Doctor__]

A program written for pal would and should use the extra lines available to them to make the circle round again by using more square pixels to make up the difference. That's part of how that's suppose to work.. up until 2009 almost everything still had height and width controls to help out, weather or not you had to take the cover off the tv/monitor to access that depends on the system, manufacturer or country..

 

and before I hear how some one opened their pal television/crt monitor and there was no height adjust... there was you just didn't know what to adjust.. there was a voltage adjust, and a linearity adjustment among others, these were there so we could handle differences in mains power so you didn't have ballooning(too large a picture) or the opposite where the picture didn't fill the screen... there was a zillion alignment manuals and procedures sitting in dusty drawers about this all over the world

Edited December 21, 2017 by _The Doctor__

[flashjazzcat]

For the very reason that the user can often adjust the picture height as he likes, we can make absolutely no assumptions about aspect ratio, and therefore might as well assume pixels are 1:1. As I say: circles look reasonably round to me without any adjustment in PAL.

[+CharlieChaplin]

and before I hear how some one opened their pal television/crt monitor and there was no height adjust...

 

... but there was high voltage, ouch !!!

[_The Doctor__]

Actually you can, since the standards, test patterns, and alignment materials all exist even to this day. Once that's done, you do your best to program the computer to output as close to what you want as possible. Then you can fine tune the display to conform to perfection. You must start from a calibrated crt/lcd. I thought it was academic..

 

There are calibration services for flat panel / home theater these days.... although not as many as there used to be. I am sure you can find all the gadgets and such on the webs and forums. Lengthy discussions, but I'm not going down that rabbit hole, you can.

Edited December 21, 2017 by _The Doctor__

[+mytek]

I remember having to open up an SC1224 to access the horizontal width coil, in order to reduce it. I made the adjustment a little at a time with the monitor powered off, and would turn it on afterwards to see my progress. There's lot's of high voltage very near to where I was working, so I didn't want to take a chance of it leaping out and biting me. But just a word of caution, even with power off there is still a pretty good charge that hangs around in the caps and the CRT, so even when not powered BE CAREFULL .

[_The Doctor__]

ah that tingly glad I'm not dead feeling

[Level42]

A program written for pal would and should use the extra lines available to them to make the circle round again by using more square pixels to make up the difference. That's part of how that's suppose to work..

I'm sorry my friend, but you just don't understand how it works.

 

NTSC has frames of 525 lines.

PAL has frames of 625 lines.

 

The A8 was developed in the US so it is only natural that they designed the system around , and aimed at NTSC.

 

The maximum number lines the A8 can produce is 192.

That doesn't change between NTSC and PAL systems.

 

So, if a circle is drawn in perfect circular shape on NTSC, it will look lower (squashed) on PAL.

 

To compensate for that following your reasoning, the ratio between TV lines and A8 lines would have to remain the same.

 

Let's do the math:

525 : 192

625 : X

 

525.X = 625x192

 

X= (625x192)/525

X= 228,5714285714

 

So...the A8 would have to produce (about) 229 lines to keep things "straight". But the 192 line was probably the max they could do/afford/fit in the first ever dedicated graphic chips ANTIC and GTIA.

 

So, following your reasoning, to keep aspect ratios correct, the US programmers would have to leave out lines....why would they want to do that ? It's "their" system and "their" country....

 

Again some math...

 

625:192

525:X

 

Xx625 =192x525

X= (192x525)/625

X= 161,28

 

So...if thenUS developers and programmers would accept PAL as being the system they have to account for, they would have to use 161.28 lines. That .28 causes even more problems but let's ignore that for now.

 

Anyway, they would have to give up on over 30 lines of graphics on the screen.......in other words waste resolution.

 

And even if they did go throguh all this trouble, it would have meant they had to redesign all graphics between the systems, resulting in PAL having more detailed vertical graphics,

 

It would mean double the amount of required graphics space in the program, a lot of extra code etc. etc.

 

So...the option the Atari designers went for makes perfect sense. We in PAL land had to live with the fact that our beloved system was designed in and for the US and that our graphics would be squashed down "forever". (Now, any good monitor can stretch the vertical size. But I doubt my parents would have appreciated watching TV with very thin people on the screen....)

 

Today, we can easily compare, but BITD I hadn't ever seen the correct aspect ratio of a NTSC system....so we were used to seeing it a bit in "Letter-box" format.

Edited December 23, 2017 by Level42

[ivop]

I'm afraid you don't know exactly how it works either...

 

Proper NTSC is 262.5 (note the half) lines per field, 525 lines per frame.

Proper PAL is 312.5 lines per field, 625 lines per frame.

 

The half lines are there so a HSYNC after half a line adjusts the vertical position of the beam by half a line, effectively displaying the next 262.5/312.5 lines in between the previous lines.

 

The Atari 8-bit computers don't have the half lines and are in fact 262/312 lines per field and could be called progressive scan avant la lettre, because the fields are aligned and not in between each other. GTIA/ANTIC generate 240 lines for both PAL and NTSC. The rest is black. The number of black lines is determined by ANTIC/GTIA and depends on being NTSC or PAL.

 

Edit: your reasoning about PAL circles being squashed is sound BTW. Just the numbers are off

Edited December 23, 2017 by ivop

[_The Doctor__]

I'm sorry my friend, but you just don't understand how it works.

 

NTSC has frames of 525 lines.

PAL has frames of 625 lines.

 

The A8 was developed in the US so it is only natural that they designed the system around , and aimed at NTSC.

 

The maximum number lines the A8 can produce is 192.

That doesn't change between NTSC and PAL systems.

 

So, if a circle is drawn in perfect circular shape on NTSC, it will look lower (squashed) on PAL.

 

To compensate for that following your reasoning, the ratio between TV lines and A8 lines would have to remain the same.

 

Let's do the math:

525 : 192

625 : X

 

525.X = 625x192

 

X= (625x192)/525

X= 228,5714285714

 

So...the A8 would have to produce (about) 229 lines to keep things "straight". But the 192 line was probably the max they could do/afford/fit in the first ever dedicated graphic chips ANTIC and GTIA.

 

So, following your reasoning, to keep aspect ratios correct, the US programmers would have to leave out lines....why would they want to do that ? It's "their" system and "their" country....

 

Again some math...

 

625:192

525:X

 

Xx625 =192x525

X= (192x525)/625

X= 161,28

 

So...if thenUS developers and programmers would accept PAL as being the system they have to account for, they would have to use 161.28 lines. That .28 causes even more problems but let's ignore that for now.

 

Anyway, they would have to give up on over 30 lines of graphics on the screen.......in other words waste resolution.

 

And even if they did go throguh all this trouble, it would have meant they had to redesign all graphics between the systems, resulting in PAL having more detailed vertical graphics,

 

It would mean double the amount of required graphics space in the program, a lot of extra code etc. etc.

 

So...the option the Atari designers went for makes perfect sense. We in PAL land had to live with the fact that our beloved system was designed in and for the US and that our graphics would be squashed down "forever". (Now, any good monitor can stretch the vertical size. But I doubt my parents would have appreciated watching TV with very thin people on the screen....)

 

Today, we can easily compare, but BITD I hadn't ever seen the correct aspect ratio of a NTSC system....so we were used to seeing it a bit in "Letter-box" format.

no you don't know how it works, you idea is right but your numbers are all wrong... it's all been covered before...

[_The Doctor__]

Ivop is the winner!

 

But you can still draw a close enough circle by adding extra plots like I said... sheesh

[+mytek]

Wow I sure provoked a lot of discussion about circles, but then isn't that what happens in circular logic?

 

Good thing I didn't mention infinity, otherwise this discussion would never end. But all good stuff for sure .

[Level42]

I'm afraid you don't know exactly how it works either...

 

Proper NTSC is 262.5 (note the half) lines per field, 525 lines per frame.

Proper PAL is 312.5 lines per field, 625 lines per frame.

 

The half lines are there so a HSYNC after half a line adjusts the vertical position of the beam by half a line, effectively displaying the next 262.5/312.5 lines in between the previous lines.

 

The Atari 8-bit computers don't have the half lines and are in fact 262/312 lines per field and could be called progressive scan avant la lettre, because the fields are aligned and not in between each other. GTIA/ANTIC generate 240 lines for both PAL and NTSC. The rest is black. The number of black lines is determined by ANTIC/GTIA and depends on being NTSC or PAL.

 

Edit: your reasoning about PAL circles being squashed is sound BTW. Just the numbers are off

 

Ivo......I made an attempt to simplify things....

[Level42]

no you don't know how it works, you idea is right but your numbers are all wrong... it's all been covered before...

Wow man....I'm impressed......tell me where ?

[Mathy]

Hello guys

 

And you're not even talking about crop circles....

 

Sincerely

 

Mathy

[dmsc]

Hi!

 

For the correct Pixel Aspect Ratio (this is the width v/s height of one pixel), you should see the Altirra Hardware Reference Manual, for a properly adjusted TV, NTSC graphics 8 pixels measure 0.857:1, PAL graphics 8 pixels measure 1.04:1.

 

This means that to draw a "circle" in the screen, in NTSC, you should draw an ellipse of "R/0.857" by "R", and in PAL you should draw an ellipse of "R/1.04" by "R". Current emulators scale the display to those ratios, so you can test, see pictures for NTSC and PAL:

 

NTSC:

 

PAL:

 

From memory, most TV I saw in the eighties were not properly adjusted, so the shapes in the Atari were not always the same.

[flashjazzcat]

Ah... so that's why circles look right in PAL: only four hundredths off 1:1.

[ivop]

Ivo......I made an attempt to simplify things....

 

I'm sorry if I came across harsh. That was not my intention...

[+mytek]

Ah... so that's why circles look right in PAL: only four hundredths off 1:1.

 

Now if only my Dell 1708FP monitor felt that way about it .

 

I've exhausted all the configuration possibilities via either the normal or service menus. Still no dice on making it square instead of rectangular with PAL, but I haven't tried under NTSC (probably should check that).

[Level42]

My friend.........do yourself a favor......get a CRT

Edited December 24, 2017 by Level42

[+mytek]

My friend.........do yourself a favor......get a CRT

Actually Simius was nice enough to create a 1280x1024 version for me to test, and I flashed it today. It works so nice. Now my circles are perfectly round .

 

What I really like besides the sharpness and no color bleed, is how vivid the color is, and how red really is RED. This is definitely a "you have to see it to believe it" kind of thing, and this has got to be the best picture I've ever seen coming from real hardware.

[Brentarian]

This is excellent news! I have several 1905FP models that are 1280x1024, so I'll be ordering from Simius soon.

[+mytek]

This is excellent news! I have several 1905FP models that are 1280x1024, so I'll be ordering from Simius soon.

Yep our dream has finally come true. Our Atari's now have true digital video output thanks to Simius and his latest RevC-DVI version of Sophia.

 

I'm still testing his 1280x1024 BETA core, but so far so good and all looks well. I'm not sure how it will be on your 1905FP, but on my 1708FP it entirely fills the horizontal aspect, and only leaves a small border top and bottom, so a good percentage of the screen real estate is utilized. I'll be gone for the next few days, but I'll try to post a video of what I am seeing when I get back.

 

And I just want to add that Simius has been extremely good at providing customer support on this project.

 

And just one more thing worth noting. It looks like most all of these Dell monitors with DVI input are good for 50 and 60Hz operation, so coupled with the Sophia, you can do either PAL or NTSC.

[Level42]

Actually Simius was nice enough to create a 1280x1024 version for me to test, and I flashed it today. It works so nice. Now my circles are perfectly round .

What I really like besides the sharpness and no color bleed, is how vivid the color is, and how red really is RED. This is definitely a "you have to see it to believe it" kind of thing, and this has got to be the best picture I've ever seen coming from real hardware.

No....don't start me on colors being real on CRT vs. LCD.....no.....not going there.......

 

Yes computer graphics colors may look nicer on a LCD.....but that's because they're artificial....try human skin colors though......

 

Off course that is not your goal here....and yes, today's LCDs have made a huge improvement over the last years, but fact is that a CRT can display an infinite number of colors, where LCDs have a fixed amount of them....and they look artificial on anything but the most modern and expensive TVs and monitors......but I'm anal, and analogue....I prefer vinyl over any digital audio format too....because I hear :)

 

I bought a Sophia RGB because I do want the best picture quality that can be pulled from an A8, but I will still be strictly using CRT only. Sophia (and before it VBXE) are the only solutions to get RGB signals out of an A8, and RGB is the most native signal format for a CRT. So I'm sure that my "monitor" (Bang & Olufsen MX4000 TV) will produce a fantastic picture through RGB SCART, and yet it will have the advantages of a CRT (no lag (I'm a gamer, lag is the worst thing possible), no smearing, no jumpy movement when large objects move, true blacks).....

 

Anyway, it's great Sophia can make both "camps" happy.

 

And it's awesome that Sophia is so flexible and that Simius keeps pulling more out of it all the time :)

Edited December 25, 2017 by Level42

[+mytek]

My Sc1224 + Sophia RevB-RGB looks awesome too, but for me I prefer DVI for a flicker-less PAL display. When first viewing the SC1224 in PAL, the flicker really jumps out at you, but after a while your eye/brain compensates for it. However when looking at my PC screen and then back, it jumps out again. Since this is my reality, I prefer the non-flicker of the DVI solution instead.

 

Then there is the footprint of a CRT vs LCD, and of course the power requirements. But I do agree that a good quality CRT is hard to beat from a picture standpoint.

 

Haven't done any gaming yet with the DVI version, so I can't say if there is noticable lag or not. Although at 62 years old, my lag is probably worse than any electronic device

[DirkSwizzler]

Interested in 1 for a 5200.

 

Still working my way through the whole thread to see if there’s a different method of ordering these days.