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iljitsch
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Posted Sun Aug 01, 2021 7:33 am

When I moved to another country, I was on a minimalism kick and got rid of a lot of old stuff. Wish I still had a lot of it today.

This includes my CRT monitors/TVs. So I'm now using my A3000 and A1200 with 1920x1080 full HD or even 3840x2160 4K LCD monitors. Which has its upsides and downsides. I'll talk more about this later, but for now:

What resolution do you use to display your Amiga's Workbench? 640x200 NTSC non-interlace? 1920x1080? Something in between?

And of course: why? Most authentic? Best for games? Easiest to read with "retro" (i.e., aging) eyes? Most space available?

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nonarkitten

Posted Sun Aug 01, 2021 8:37 am

Still on the hunt, but max-overscan NTSC non-interlaced fills 16:9 okay with mostly correct aspect for modern icons expecting Workbench to be in interlaced mode. Personally temped to grab the half-scaled MagicWB icons and go back to that so the stupid icons aren't such real estate eaters. I wouldn't mind NewIcons or GlowIcons so much if they scaled properly for the aspect, but they all assume you're running RTG and I'm not a fan of it.

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McTrinsic

Posted Sun Aug 01, 2021 9:10 am

As long as my Phoenix with my Kryoflux graphics adapter was up and running, I found myself using 1152x864.

When /once I get my new system up and running, I would hope for 1280x1024.

Depends a bit on how much color I actually want or find nice to behold.

For an ECS Amiga like A500/2000 you are stuck at 2MB in ZorroII space.

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stevelord

Posted Sun Aug 01, 2021 10:21 am

I switch between 1280x720x256 and 1920x1080x65535. My ZZ9000 provides 16 bit full HD but struggles with it on my setup. 8-bit 720p Flies so I generally work in that unless I need something specific. Workbench GUI elements are fairly small so above 768 (e.g. 1024x768) the benefits drop off.

Most apps that run on their own screens (e.g. Lightwave, Vista etc) prefer lower resolutions anyway. You can force it with modepro, but the results are rarely worth the effort.

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iljitsch
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Posted Sun Aug 01, 2021 11:26 am

Interesting! Two extremes in the first two replies.

As for non-interlaced resolutions: as you may have noticed, I've been working on a tool to convert 1.x icons to newer icons that look right, and one of the issues is that 1.x. usually runs non-interlaced while 2.0+ assumes a "square pixel" resolution.

I've been thinking about an option to shrink 2.0+ icons vertically to make up for the difference. But an issue with that is that in order to do that right, you need extra colors. For instance, a MagicWB icon at 8 colors would need 8x7 = 56 colors to accurately display the colors between any of the 8 colors and 7 other colors correctly. It's probably possible to fudge that a little, but I doubt it's going to work well with less than 32 colors and also a 32-color Workbench.

As for my personal situation: I used to run the Cybergraphx card in the A3000 at 800x600 but then decided an even fraction of 1920x1080 would be better, so I tinkered until I got 960x540 out of the card over VGA. The nice thing about that is that it fills the entire screen, and it's still a resolution that's reasonably Amiga-like. 1280x720 would also work but that's a resolution that is much higher than you'd get from a regular Amiga. (And it's a 68030 with 8 MB fast RAM, so I have to be careful about making the CPU do too much work or have excessively high resolutions using up too much RAM.) That's at 256 colors.

The A1200 has an Indivision MK3 so it can output the Amiga's resolutions to almost arbitrary HDMI (or VGA, but haven't tested that) resolutions. I also worked on 960x540 for that, but the MK3 still depends on the limitations of the AGA chipset so it's 960x540 at 50 Hz interlace or 960x540 at 25 non-interlaced (with a lot of tweaking) and that's not ideal. So I usually run the A1200 at 720x540 DblPAL at 32 colors. Or if I need more colors PAL ~720 x 540 interlaced at 64+ colors.

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nonarkitten

Posted Sun Aug 01, 2021 1:30 pm

iljitsch wrote:
Sun Aug 01, 2021 11:26 am
[...] 1280x720 would also work but that's a resolution that is much higher than you'd get from a regular Amiga.
Superhires; "am I a joke to you?"

Amiga can literally do 720P. Ever since ECS.

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SPiFF

Posted Sun Aug 01, 2021 7:04 pm

A1200 here with AGA MK3. I run with either a Sony Trinitron 17SFII VGA CRT or a 17" 4:3 VGA LCD that has 1280x1024 native resolution but can do 15khz.

I run in NTSC. I tried to run in 800x600 using the SUPERPLUS High Res Laced screen mode for a while, but I just didn't like it. Classic WB just doesn't look right to me at those resolutions. This mode does look good on the LCD as it is an integer multiple of the native resolution and the AGAmk3 does a good job with the de-interlacing.

Since you only have fixed pixel displays, for sure the best outcome will be a resolution that is an integer multiple especially if you don't have a good scaler. The LCD looks like crap at NTSC, but the CRT is glorious. Not because of the low resolution just because of the non-integer scaling.

EDIT, here is the 800x600 screen mode on the two displays.
A1200-AGAmk3_800x600_trinitron.jpeg
A1200-AGAmk3_800x600_lcd.jpeg

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nonarkitten

Posted Sun Aug 01, 2021 8:11 pm

It's possible to have almost non-integer scaling look as sharp as a CRT ever did, people are just too lazy to do it right. The reality is that you only have to do integer scaling on the vertical axis and you can do very non-integer on the horizontal to maintain original aspect ratio and still have it look perfect.

This image has integer scaling on the vertical but imitates PAL pixel aspect with a very non-integer (and not even close to integer) scale.

Image

Same thing with scanlines, it's just laziness darkening every other line or something to that effect. In truth you want an overlay filter at about 50% blend to effectively copy scanlines. If you're curious, that makes a "hysteresis" curve that ensures that the average of two lines, one dark and one light average to a 1:1 with the source.

So no stupid darkening. Perfect aspect ratio and looks just as sharp. But like I said, too lazy to implement it.
Image

With these two powers combined we even get a pseudo soft bloom that was characteristic of CRTs for free. No pixel shaders required, simple horizontal linear filter and simple vertical scaling with a super basic overlay function.
Image

I worked out the other day what that function was and came up with:

Code: Select all

static inline uint8_t scanline_filter(uint8_t component, bool is_light) {
    uint8_t min = (component < 127) ? 127 : component;
    uint8_t cd2 = (component >> 1);
    return cd2 + (is_light) ? min : (component - min);
}
Note that I've not tested this as I to am lazy. And also swamped with Buffee. It would be super keen if someone out there gave this a try.

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iljitsch
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Posted Mon Aug 02, 2021 2:07 am

Nonarkitten: which hardware is applying your filter??


The Workbench image with the scanlines is pretty good, but it there's a wave of non-uniformess over it. With the Indivision MK3 it's worse and I find it very distracting. IMO scanlines is the only way to go for non-interlaced resolutions, so I only use integer scaling on the MK3 side. This works great for PAL on 1920x1080 monitors as 270 / 540 lines fits 256 / 512 with just the right amount of overscan.

NTSC is much more difficult. However, my monitors have much smoother scaling and non-integer works much better on those, so what works here is 432 lines (400 plus modest amount of overscan) multiplied by 2 = 864 lines. The monitor then has to do 1.25 x scaling to get to 1080 lines (2.x x on the 4K monitor). That looks fine. I then like to stretch the image a bit to fill the entire screen width.

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nonarkitten

Posted Mon Aug 02, 2021 10:28 am

iljitsch wrote:
Mon Aug 02, 2021 2:07 am
Nonarkitten: which hardware is applying your filter??
None, this is done post right now with just screen shots. I don't really have the know how on how to apply it really, but I guess I could take a stab at it. Maybe put it on my ReDenise...
iljitsch wrote:
Mon Aug 02, 2021 2:07 am
The Workbench image with the scanlines is pretty good, but it there's a wave of non-uniformess over it.
I'm not sure I'm seeing that. Could you explain this?
iljitsch wrote:
Mon Aug 02, 2021 2:07 am
With the Indivision MK3 it's worse and I find it very distracting. IMO scanlines is the only way to go for non-interlaced resolutions, so I only use integer scaling on the MK3 side. This works great for PAL on 1920x1080 monitors as 270 / 540 lines fits 256 / 512 with just the right amount of overscan.
Interger scaling makes the aspect wrong, however, and their scan line implementation is just the simple "make it darker" approach. If you don't have a 1600 NITS HDR monitor, it ends up being too dark, IMHO.
iljitsch wrote:
Mon Aug 02, 2021 2:07 am
NTSC is much more difficult. However, my monitors have much smoother scaling and non-integer works much better on those, so what works here is 432 lines (400 plus modest amount of overscan) multiplied by 2 = 864 lines. The monitor then has to do 1.25 x scaling to get to 1080 lines (2.x x on the 4K monitor). That looks fine. I then like to stretch the image a bit to fill the entire screen width.
Interlacing needs to be fixed at the source, there is no acceptable way to deinterlace video after the fact -- they're all compromises.





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