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JohnNovak
Brisbane, Australia
Website

Posted Sat Apr 16, 2022 12:42 am

Hey guys, first post here. I've recently discovered a method to emulate the C= 1084S quite faithfully in WinUAE via shaders, so I wrote a lengthy blog post about it because I think this information is not widely known, and there are quite a few pitfalls and gotchas to run into when you attempt to set it up for the first time. I love WinUAE, but it's really not newcomer friendly; I've spent days figuring out all these little details about the configuration that I'm explaining in the article.

https://blog.johnnovak.net/2022/04/15/a ... the-amiga/

As you'll see, I borrowed a few CRT photos from the games library and the forums -- hope that's fine with everybody! :D

I'm sure intric8 and Shot97 will be happy to discover that I dedicated an entire section to emulating NTSC games with the correct aspect ratio & timings. There's so much misinformation about the aspect ratio topic that it's not even funny, so I'm doing my small part in raising awareness to this issue.

Anyway, check out my article if you're interested, and I'd love to hear your opinion about my setup. Here's a few screenshots as bait :)

Cheers!

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fxgogo
London, U.K.
Website

Posted Sat Apr 16, 2022 1:45 am

John, you are speaking my language. Definitely will take a look. Been on the same journey myself but for post processing images of all types in packages like After Effects etc. The images you posted look awesome.

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intric8
Seattle, WA, USA
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Posted Sat Apr 16, 2022 8:47 am

Hi John!

This is a topic near and dear to my heart, as well as Shots. Where is your blog post? (I just woke up and I'm not seeing it.)

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JohnNovak
Brisbane, Australia
Website

Posted Sat Apr 16, 2022 4:04 pm

intric8 wrote:
Sat Apr 16, 2022 8:47 am
Hi John!

This is a topic near and dear to my heart, as well as Shots. Where is your blog post? (I just woke up and I'm not seeing it.)
My bad, I wasn't fully wake either when I created the thread... Updated the post with the link! :boing:

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fxgogo
London, U.K.
Website

Posted Mon Apr 18, 2022 1:11 pm

Wow, so that is one detailed blog post. Still going through it and gonna test out your settings. They look very intriguing. I know you said PAL pixels are almost square that we can consider them as such, but I just can’t do that. I think it is my job as a designer that sees such imperfections, he he.

Don’t know if you have seen this, but it is one of the best simulations of CRT’s I have seen. However the rendering time needed is rather funny.

https://int10h.org/blog/2021/01/simulat ... t-1-color/

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iljitsch
Website

Posted Tue Apr 19, 2022 5:19 am

Ugh, my MacBook Pro crashed while I was typing!

Anyway, interesting post, but about the NTSC stretch: my A1200 tells me that this is 26:22 = 1.181818... so a hair less than a factor 1.2.

We did discuss the stretch thing a while back on this forum, and it's obvious that this is not just an intended for PAL / intended for NTSC thing.

Having to deal with non-square pixels is extremely annoying for programmers, so I'm sure many never bothered, as the difference is usually not too obvious. But then DPaint automatically applies the stretch when it deems that appropriate, so you can easily end up with stretched as well as non-stretched content in the same game.

It's cool that the Amiga was so flexible with its video modes when we were still dealing with PAL/NTSC timing. But the jump to higher flicker-free resolutions didn't stick the landing. I so much wish it was easier to make games run in the resolution I want to run them in rather than have the run in the resolution that the original programmer hardcoded decades ago.

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JohnNovak
Brisbane, Australia
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Posted Tue Apr 19, 2022 5:13 pm

Thanks guys, glad you found the article interesting. Replying to a few points:
fxgogo wrote:
Mon Apr 18, 2022 1:11 pm
I know you said PAL pixels are almost square that we can consider them as such, but I just can’t do that. I think it is my job as a designer that sees such imperfections, he he.
Well, Amiga OS itself reports PAL as 44/44 pixel aspect ratio. Pixels are *supposed* to be square in PAL, at least when using a monitor. Because of the PAL TV standard, when you hooked up your Amiga with an RF adapter to a properly calibrated TV, the pixel aspect ratio was a tiny little bit off. Like 1.03 or something instead of 1.0. But who cares about TVs, really...

I think you might be referring to stretching of the 5/4 PAL image to fill the 3/4 screen, for which you had to stretch the image a tiny bit horizontally. I'd say that's incorrect, and even back in the day I drew a large 200x200 square or something in DPaint and adjusted my monitor stretch controls until the sides were the same length when measured with a ruler. That makes perfect sense for PAL games, as squares will be square, circles will be circles, and so on. But yeah, I guess quite a few users just did the full horizontal stretch thing... the evil what men do :)

You can easily adjust my settings for that: keep the vertical scale factor at x3 etc. and only adjust the horizontal scale factor the the desired "squash" (I published the formulas to use, just do the math yourself). Don't do it the other way around (keep horizontal stretch constant and adjust vertical stretch) because that could introduce scanline-aliasing.
fxgogo wrote:
Mon Apr 18, 2022 1:11 pm
Don’t know if you have seen this, but it is one of the best simulations of CRT’s I have seen. However the rendering time needed is rather funny.

https://int10h.org/blog/2021/01/simulat ... t-1-color/
Yeah, some of the low-res single-scanned example look decent or even quite good, but the double-scanned VGA stuff is completely wrong. There is *no way* you're gonna emulate the ~0.25 triad dot mask at 1080p, it simply won't happen, it's a physical impossibility. Even 4k isn't enough for that, 8k would be about right (and at fullscreen only, probably).

For state-of-the-art CRT shaders, check out this LibRetro thread. This is Guest's new work (sadly can't be backported to WinUAE as it doesn't have the advanced shader architecture that RetroArch has):

https://forums.libretro.com/t/new-crt-s ... 25444/2131
iljitsch wrote:
Tue Apr 19, 2022 5:19 am
Anyway, interesting post, but about the NTSC stretch: my A1200 tells me that this is 26:22 = 1.181818... so a hair less than a factor 1.2.
Yeah, that's what DPaint V reports, 44/52 (=22/26) pixel aspect ratio for NTSC low-res, and it gets it from the OS.

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iljitsch wrote:
Tue Apr 19, 2022 5:19 am
We did discuss the stretch thing a while back on this forum, and it's obvious that this is not just an intended for PAL / intended for NTSC thing.
Sorry I can't parse that sentence, what's obvious and why?

As I see it, this is all purely theorethical, bit of a much ado about nothing situation:

- For PAL, the OS reported PAR is 1:1, and that's what the more discerning users did back in the day (adjusted their monitors for 100% square pixels)
- For NTSC, all the different reported, calculated, etc. values don't matter one bit. In practice people, adjusted their monitors so the 320x200 image fills the whole 4/3 screen, which gives 1:1.2 PAR. Exact same deal as with VGA.

Of course, you have my formulas, you can do whatever easily. But I didn't want to confuse my readers with all that unnecessary detail that ultimately doesn't give you "better" or "more authentic" results. Plus these are the exact settings I'm using; I wasted a day trying all these esoteric ratios, but my conclusion was it's not worth the effort, the differences are so minimal, and not even desirable.

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iljitsch
Website

Posted Tue Apr 19, 2022 9:13 pm

Well, in such a long post mentioning that you're rounding 26:22 to 1:1.2 could have made the cut...

From this earlier discussion on this forum I took away that obviously there's more to the whole stretch thing than the TV standard in use where the program was created. See for instance my Frontier example in the linked thread, which runs in 320x200 in either PAL or NTSC. Or maybe that's a bad example because it was created by a British game developer but published by a US game publisher.

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JohnNovak
Brisbane, Australia
Website

Posted Tue Apr 19, 2022 11:10 pm

iljitsch wrote:
Tue Apr 19, 2022 9:13 pm
Well, in such a long post mentioning that you're rounding 26:22 to 1:1.2 could have made the cut...
It's not about adding a few more extra sentences to the already long article, it's just that all such discussions are ultimately fruitless, confusing, and of little practical utility, hence I decided it's best to leave it out.

If you want to be super-anal about it, the OS reported 44/52 figure is also an approximation, and technically incorrect. There's a discussion about it on EAB or LemonAmiga, I can't be bothered to find it again. People go into lengthy arguments about the Ultimate-Technically-100%-Correct-Pixel-Aspect-Ratio(TM), and the results are quite inconclusive as far as I could tell...

In practice: use 1.2 and move on with your life.
iljitsch wrote:
Tue Apr 19, 2022 9:13 pm
From this earlier discussion on this forum I took away that obviously there's more to the whole stretch thing than the TV standard in use where the program was created. See for instance my Frontier example in the linked thread, which runs in 320x200 in either PAL or NTSC. Or maybe that's a bad example because it was created by a British game developer but published by a US game publisher.
Oh yes, if that's what you meant that's definitely true. And I've discussed it in my article under the "But life ain't simple" section -- I even provided an "algorithm" for determining the correct aspect ratio to use per game, you might have missed that part. For American made games, the answer is really simple, for the rest, it's a bit more involved.

https://blog.johnnovak.net/2022/04/15/a ... int-simple

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Shot97
Detroit, MI, USA
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Posted Sat Apr 23, 2022 8:56 pm

Enjoyed the article, good stuff and looks great. U.S Gold was actually a European software house, but you're still correct in recommending people use NTSC for the most part with that company, as their whole "thing" was acting as a European publisher for American designed games when the American publishers did not have a presence in Europe. That's not always correct, as there were some games which were developed by them, not just published. Until about 1993 they had no actual U.S. presence, it's just a name which implies the "best" of the U.S., of course they also published some turds too. Eventually they actually did set up a division in America kind of doing the reverse, publishing European stuff here. - Just wanted to add some interesting (to me) history there.

In general I can't stand when people name U.S. gold in connection with most games. They were among the laziest of the lazy in terms of their publishing. Magazines and people today gave them way too much credit, and they were never even bothered to slap in their logo or something into the title screens, where when a European game came to America with a different publisher, they still lifted a tiny finger and would put in their logo or something. SSI's stuff was published by U.S. Gold in Europe (by themselves in America), as was Lucas Arts, that was often the go-to for American companies with no European office. But while I often give both a developer and publisher credit, U.S. Gold can suck it, they were just publishing stuff which had already been published.





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