Trouble with PAL/NTSC Output on CRT

[BraveToaster]

Hi,

I'm pretty new to MiSTer and have gotten a MiSTer Multisystem a while back. For video output, I use the built-in RGB SCART port. In case you aren't familiar with this hardware, this is what the manual says about it:

For technical reference the SCART sync output is automatically combined from the VSync and HSync signals, this combined sync is then connected to the SCART Composite sync output via a 68 Ohm resistor.
This combined sync means that you do not need to select composite sync output in the MiSTer.INI file. It can be enabled or disabled and the SCART sync output will still function.
For the Analogue RGB SCART output to function correctly, the resolution of the analogue RGB must be allowed to output at the original raw signal of the machine/computer/console being simulated. This basically means that the VGA scaler must always be turned off in the MiSTer.INI file

I have connected a Loewe Calida CRT TV via RGB SCART. It is a 100/120Hz TV from the late 90's that can happily display PAL, PAL60, and NTSC signals. It has run ₃₅,000 hours as a regular PAL TV, but seems to be in perfect working condition in general. I've played around with different cores on the MiSTer and am super happy with the results. However, I cannot really get a consistent signal out of the device across cores. It's particularly noticeable for PAL (for which I didn't touch the TV's factory settings) - for example, while the picture is fine in the Amiga core, it's noticeably squished and misaligned in Genesis and SNES:

Amiga PAL

Amiga-PAL.jpg (216.3 KiB) Viewed 3418 times

SNES PAL

SNES-PAL.jpg (222.1 KiB) Viewed 3418 times

For NTSC, I took the 240p test suite on SNES and adjusted the image in TV's service menu as best I could. It's near perfect on SNES, and still almost perfect on Genesis, as shown here:

Genesis NTSC

Genesis-NTSC.jpg (265.77 KiB) Viewed 3418 times

However, with the same settings, NTSC games on Amiga now aren't in the right place anymore:

Amiga NTSC

Amiga-NTSC.jpg (290.2 KiB) Viewed 3418 times

What's the matter here? Is it really true that the original systems had vastly different outputs and so it's an artifact of the original hardware or is there some kind of setting that I'm missing? It's particularly annoying that I cannot display PAL games on SNES/Genesis correctly without massively screwing up the image calibration for everything else on the TV.

I have attached my current MiSTer.ini as well.

Thanks for any suggestions!

P.S.: Is there any way with my setup to make the scripts and INI editor display correctly? With the current settings, the scripts immediately terminate because it can't display them, so I have to run them via SSH.

[jlancaster86]

This is all typical with gaming on a CRT TV. Avoid PAL wherever possible for most systems, as the games were often poorly converted from NTSC (hence the squished image).

[BraveToaster]

Well, but the image I was showing above is the 240p Test Suite for PAL. That clearly can't be a bad game conversion, that's a matter of the general PAL output of the SNES core. Surely the original European SNES didn't always output a misaligned image?

[jlancaster86]

It will look squished in PAL if you're using the 256 × 224 test pattern. Have you tried the 256 × 239 pattern?

[FoxbatStargazer]

The Amiga is horrible and deviant for normal TV standards, yes. Barring any new options being added to the core, your main recourse is going to be to mess with the scaler rather than the simple direct output to try and standardize things. Maybe something like

Code: Select all

[minimig]
vga_scaler=1
direct_video=0
video_mode_ntsc=660,240,60,cvt
video_mode_pal=660,278,50,cvt

in the core menu choose aspect_ratio=full and disable any filters.

You can replace the shorthand modes with a more explicit one that adjusts all the blanking settings, to tweak the size and centering from the Mister side.

same deal with using scripts on a CRT, just use the scaler

Code: Select all

[menu]
vga_scaler=1
direct_video=0
video_mode=640,240,60,cvt

[Grumpy-Old-Gamer]

The Amiga is horrible and deviant for normal TV standards, yes. Barring any new options being added to the core, your main recourse is going to be to mess with the scaler rather than the simple direct output to try and standardize things. Maybe something like

Code: Select all

[minimig]
vga_scaler=1
direct_video=0
video_mode_ntsc=660,240,60,cvt
video_mode_pal=660,278,50,cvt

in the core menu choose aspect_ratio=full and disable any filters.

You can replace the shorthand modes with a more explicit one that adjusts all the blanking settings, to tweak the size and centering from the Mister side.

same deal with using scripts on a CRT, just use the scaler

Code: Select all

[menu]
vga_scaler=1
direct_video=0
video_mode=640,240,60,cvt

The Amigas NTSC output was basically spot on spec which is why it was popular for video processing work like Genlock etc

Though it's easier just to use HDMI output and let the scaler do the work

[FoxbatStargazer]

The Amigas NTSC output was basically spot on spec which is why it was popular for video processing work like Genlock etc

Though it's easier just to use HDMI output and let the scaler do the work

So is the PAL weird because, at the end of the day, Commodore was an American company that didn't give a toss?

Sounds believable.

Too bad that's where most of the game dev ended up...

[Hetzen]

So is the PAL weird because, at the end of the day, Commodore was an American company that didn't give a toss?

Ha, over in the UK, NTSC stood for No Two Same Colours in the video industry.

[BraveToaster]

It will look squished in PAL if you're using the 256 × 224 test pattern. Have you tried the 256 × 239 pattern?

That is actually a good point, but it doesn't change all that much:

SNES PAL at 239

SNES-PAL-239.jpg (270.65 KiB) Viewed 3157 times

So as you can see, the image is still squished.

The Amiga is horrible and deviant for normal TV standards, yes.

That is a surprising statement considering the Amiga PAL output is just as I would expect while the console cores output a squished image. The TV is calibrated correctly for typical PAL DVD Player or television signals, and as you can see above in the Zool screenshot, the Amiga core outputs the image very nicely. However with the same calibration, the output from SNES for example isn't all that great (see this post).

same deal with using scripts on a CRT, just use the scaler

That was a great suggestion. With the modeline you posted, the image didn't look right (it had a clear red tint), but I looked around the interwebs and ended up with this snippet, which is quite good. No color tint and while the image is a little too narrow, it's definitely good enough for menu and scripts:

Code: Select all

[menu]
vga_scaler=1
direct_video=0
video_mode=640,65,60,108,224,16,0,26,13919

Also important was to set

Code: Select all

fb_terminal=1

otherwise scripts don't work at all on the CRT.

While we're here, this snippet made ao486 work pretty nicely for me:

Code: Select all

[ao486]
vga_scaler=1
video_mode=640,65,60,108,224,16,0,26,13919
vsync_adjust=1

ao486 with modeline

ao486(1).jpg (191.67 KiB) Viewed 3157 times

So thank you all for the suggestions.

What I still don't quite understand is why it is so hard to find a modeline that "just works" on a standard consumer PAL or NTSC TV. I mean, DVD Players with RGB SCART and/or Component output don't require all that tweaking, they just output a nice image. With that in mind, shouldn't there be a standard "PAL TV" or "NTSC TV" modeline that always works and the scaler does the rest?

[jlancaster86]

So as you can see, the image is still squished.

Of course. A PAL image is 576i, or "288p" with these systems' pseudo-progressive modes. So, a resolution of 256 × 239 translates to only 83% of the vertical screen area. It's better than the 78% of 256 × 224, but still not ideal. Either way, your image will look squished unless you can somehow adjust the monitor to compensate.

Compare that to the 480i/"240p" of an NTSC image. A resolution of 256 × 224 gives you 93% of the vertical area, and whatever black bars are present might be obscured by overscan (depending on the TV). 256 × 239 would obviously fill practically 100% of the vertical area, but then you risk losing the top and bottom parts of the image to overscan.

I grew up with PAL (I'm Australian), and I can assure that these Japanese systems always looked squished on our TVs with significant letterboxing, and with some basic knowledge of the resolutions involved, it's easy to understand why. At the end of the day, they were designed for NTSC and bodged in various ways to at least work in PAL.

As I said earlier, don't even bother with PAL on these systems if you can avoid it. In addition to these resolution issues, games were rarely adjusted for the speed change properly (if at all, depending on the system). And even under perfect conditions, the 50 Hz flicker of a CRT can be outright painful to look at these days.

[BraveToaster]

I grew up with PAL (I'm Australian), and I can assure that these Japanese systems always looked squished on our TVs with significant letterboxing, and with some basic knowledge of the resolutions involved, it's easy to understand why. At the end of the day, they were designed for NTSC and bodged in various ways to at least work in PAL.

That makes sense. I never owned one of these consoles in the 90s and only played with friends, so I guess I just don't remember the letterboxing. The games were stunning either way (Donkey Kong Country blew my mind at the time )

And even under perfect conditions, the 50 Hz flicker of a CRT can be outright painful to look at these days.

I noticed with the computer CRT, that was really painful. However, this TV doubles the frames (100 Hz/120Hz), so flicker is not an issue at all, which is nice.
Of course that comes with some other caveats and CRT purists would avoid this TV generation like the plague, particularly for fast action games, but I'm actually really happy with it as it is.

[FoxbatStargazer]

I'm not bagging on PAL because virtually every other Mister system I've tried has PAL positioned in ways that make sense. It's specifically Amiga that is wacky. (and I understand not even consistent between games?)

( The whole color thing is really irrelevant anyways with RGB at our fingertips. )

[Malor]

As far as I know, actual Amiga hardware does very nice signaling on both PAL and NTSC; video ended up being one of its main uses, and the good output quality was a lot of why that was true.

The Minimig core, however, is not real hardware, and it wasn't originally developed on the Mister. I haven't actually fooled with using the Amiga core on a CRT, but it may be impaired by trying to run it through the Mister's scaler. What I would try first, on the assumption that the FPGA reimplementation is high quality, is letting the Amiga core drive the CRT directly, and making adjustments so that it looks good. Then if other cores don't look right, I'd probably try running them through vga_scaler.

My assumption that the Minimig code is natively generating correct signals may be dead wrong, however. Again: not developed on the Mister. It could be doing horrible things to the video. Leaving the other cores driving the CRT natively, and piping the Amiga core through vga_scaler, may be a better approach.

[akeley]

Amiga CRT output from MiSTer should be 1:1 right out of the box, same goes for most of the other cores. You shouldn't need any specific modelines, with some rare exceptions (definitely not for the most popular consoles and micros baring ao486). The basics have been covered here: https://github.com/MiSTer-devel/Wiki_Mi ... -CRT-Guide

1:1 for Amiga means that all the quirks are present: the PAL image poistioned in the upper half, NTSC bottom often lacking, also in some cases the image might be shifted to the right (differing between WB and games). Also many games use different resolutions, often within same game. But this just how it is on the OG HW, something I confirmed during many hours of side by side comparisons. Whether one likes it or not is an acquired taste, but it's something that simply goes with the territory of being a trailblazing machine.

So my advice would be to check your config for some basic omissions/mistakes (happens very easily) and also, if possible, try your MiSTer on a "normal" 15 kHz CRT, seeing as these 100Hz sets might have their own quirks.

[BraveToaster]

Thanks! I don't have a chance to try it on another 15 kHz TV, but this 100 Hz one has served me well so far.
It's definitely usable anyway, worst case I'll have to adjust a bit in the service menu between cores or find a "mostly okay" setting that works for both.
As I said, PAL on Amiga is just fine with the factory settings - and I've optimized NTSC for the other consoles and seeing that PAL seems to be an afterthought for most games on those, that already covers most use cases tbh. According to the service manual, 50 Hz and 60 Hz settings are entirely separate.