RetroArch/Genesis Plus GX - EU/PAL region, bad aspect ratio


I’m trying to find out what the issue is that causes the emulation to output a bad aspect ratio for PAL region ROMs with core default aspect ratio. The image is stretched horizontally quite a bit; forcing the aspect ratio to 4:3 does almost fix the issue (it adds 13 pixels in comparison to NTSC), but I’d rather understand why this is an issue only for PAL region. Also, defaulting the core aspect ratio to NTSC PAR does the same as forcing 4:3 in global configs.

I would appreciate if someone could comment on this. Thanks in advance.


  • Windows 10
  • RetroArch v1.8.3
  • Genesis Plus GX (v1.7.4.92b3528)

Here are some screenshots:

The issue is the behavior of PAL consoles :smiley:

2D content that was developed originally and /or with NTSC regions in mind will usually look off on real PAL hardware.

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Thanks for the reply, although the PAL region has nothing to do with this issue, in fact NTSC is not being scaled accurately either, but it is scaled horrendously worse in PAL.

It is not that it feels off because the game was designed a certain way or with a certain resolution in mind. It is very much off because the image is being badly stretched by the emulator and/or RetroArch.

In fact, in my case, NTSC games are being scaled closer to PAL resolutions and PAL games are just being stretched way wider than they should ever be.

Keeping in mind that I’m playing at 1080p, I did some math and this is what I got:

Native resolutions:

  • NTSC: 320 x 224
  • PAL: 320 x 240

6.8% divergence between resolutions

Example of correct ratio (ie: BizHawk/Genesis Plus GX)

  • NTSC: 320 x 224 -> 1542 x 1080 (W +482%)
  • PAL: 320 x 240 -> 1440 x 1080 (W +450%)

6.8% divergence between resolutions

Ratio in RetroArch/Genesis Plus GX (auto core-provided ratio)

  • NTSC: 320 x 224 -> 1411 x 1080 (W +440%)
  • PAL: 320 x 240 -> 1711 x 1080 (W +535%)

19.2% divergence between resolutions

Ratio in RetroArch/Genesis Plus GX (global 4:3 enforced)

  • NTSC: 320 x 224 -> 1440 x 1080 (W +450%)
  • PAL: 320 x 240 -> 1440 x 1080 (W +450%)

No divergence between resolutions

Ratio in RetroArch/Genesis Plus GX (manual NTSC PAR ratio)

  • NTSC: 320 x 224 -> 1411 x 1080 (W +440%)
  • PAL: 320 x 240 -> 1424 x 1080 (W +445%)

0.9% divergence between resolutions

Ratio in RetroArch/Genesis Plus GX (manual PAL PAR ratio)

  • NTSC: 320 x 224 -> 1695 x 1080 (W +529%)
  • PAL: 320 x 240 -> 1711 x 1080 (W +535%)

0.9% divergence between resolutions

Apparently only 4:3 and NTSC come close to delivering a ratio close to the original, but PAL ratio does not seem to be taken into account at all, being stretched horizontally far more than it should. The most problematic thing though is that the core-provided ratio when detecting PAL delivers this bad resolution, I would guess this to be a mistake.

I would be glad if someone could chime in about this, it seems to me that the core isn’t even the issue, but I am not sure which core version BizHawk uses or if that may even be a factor. Maybe I should open an issue in GitHub concurrently.


GitHub issues created:

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I did some more comparisons and it really seems to be exaggerating horizontally.

Screengrabs used for comparison

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Not directly Genesis related, but i think you should watch this:

Maybe it helps you understanding retrogames aspect ratios better :slight_smile:

[EDIT] found the Genesis video :slight_smile:

[EDIT2] another good video (i know, i’m a bit of a fanboy of this channel :wink: )


Thanks for the videos. I guess I fell into that pitfall of using circles to try to make a point :slight_smile:

By that I mean, I used the 240p Test Suite ROM in Retroarch, alternating between NTSC and PAL regions for linearity test sets. 256x224 PAL is the only one which looks pretty bad, but it may well be the result of upscaling an already crunched aspect ratio.

NTSC 256x224

PAL 256x224

NTSC 320x224

PAL 320x224

Yeah circles … *chuckles*

covered in the DOS video from 4:15 onwards.

On 10:42 of the DOS he covers the problem of aspect ratio and scaling artefacts.

To be honest, there are a gazillion of threads around the web discussing this topic.
For example the right aspect ratio for Donkey Kong.
and so on…


After watching several streams (including a hilarious session on Allen’s channel) I “learned” that 9:6 is the correct aspect ratio.

[Best Quote ever]

Actual pixel aspect (8:7) for the win.
I can’t stand narrow Kong!
4:3 is bad enough, but this 9:6 makes me grimace.


The H-SIZE and V-SIZE pots on the DK monitor are free-adjusting, so it’s really whatever aspect ratio the user wants.


It’s worth considering that, if nothing else, the pixel art would have been designed at 8:7, since that’s the “native” ratio, making a pretty strong argument for it being how things were intended to look.

WRONG! :wink:

The same differences of opinion applies to the creators of emulators.
Square pixels or stretched or … ?

Plus there is the problem of horrible ported PAL games.
I come from the PAL area and i never knew that lot of the games were slower than their NTSC counterparts.
I also never noticed that the letterboxes on top and bottom were only on PAL games until i played the first time a NTSC game.

I personally use 4:3 for most of the games (apart from a few exceptions) but i think this is a matter of taste.

The only thing i can’t stand is when someone is stretching old games to 16:9 (playthrougs on youtube) :wink:

I was actually being sarcastic about the circles; in this particular case they demonstrate perfectly the “bad aspect ratio” in upscaled 256x224 PAL games. These were not the subject to any artistic decision, they were in fact created perfectly symmetrical in both resolutions for the very reason of testing aspect ratio in displays, although it was intended for real hardware usage (probably 4:3 displays too) and not emulation in particular.

In any case, PAL upscalling in RetroArch (and many other I would assume) stretches wider than I would be comfortable with to maintain aspect ratio in so far that that particular circle should not be oval. It may well be the case that the “bad aspect ratio” is just a byproduct of the technical standards of PAL being upscaled, whereas NTSC does better for the same reason. Basically that I feel

I grew up on PAL games and back then I wasn’t aware of the differences either, but the most striking isn’t even the resolution, it’s the game speed. There are a few NTSC games which have top/bottom borders, or rather have modes of game that are switched from full vertical borderless to vertical with borders. I would imagine that is based on the artistic or technical implementation… Street Fighter games are one such example, of course the PAL counterpart will have even bigger borders. Anyway, now days I can’t find any reason to go with PAL over NTSC, unless if I want to make the game a little easier and the music out of tune :slight_smile:

Translation in my native language is the main reason that i stick to a couple of PAL games.

But PAL Street Fighter is like slow motion.
I mean “really” slow motion.
I feel like being ====FLASH> :zap:

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The benefit of retroarch is, you can change the global options to 4:3. independent if the core supports that or not. I also prefer the original experience why I set the options of retroarch to 4:3.

I never recognized a slowdown with genesisplusgx. Only the missing soft patching annoys me a little bit. But it is ok

Sure, I was just very interested in understanding why the core aspect ratio for PAL would by default end up so wide visually, even though it may just be the case that the vertical adjustment is mathematically overcompensated horizontally in practice.

As for the slowdowns, if I am not mistaken in the context, we were actually referencing how PAL is slower than NTSC, and while as kids we didn’t know any better and/or didn’t care, nowdays we can just run both side by side and see a disparity that is obvious, especially in the sound department if it was not optimized.

What is that about the soft patching by the way?

Soft patching means, if you have a romhack/translation (e.g. look there you can have it side by side with your roms:
gamename.ips (or.bps, .xdelta, or wathever format your patch is)

This works well on some cores, but not on Genesis Plus GX.
Here you must “hard” patch your game

Right, I get it now. I have a few but I hard-coded the patching in the roms. But yeah, I would see why soft-patching would be interesting, especially for legal distribution.