Unevenly scaled pixels in screenshots/videos

[XTM]

A few days ago, I was watching a video of an old Speccy game on a YouTube channel whose owner uses original hardware - in this case, a 48k Speccy with AY interface and a DivIDE. In the past, he had used a composite mod for the picture but at some point he upgraded to the ZX-HD from ByteDelight to show the picture via HDMI. So far so good.

This guy creates his videos using OBS Studio, with the Speccy screen being in a window, obviously upscaled. Now, the issue I'm talking about wasn't that noticeable in other videos, but in this particular case where the graphics had a lot of diagonals, I noticed the unevenly upscaled pixels and commented on that. Maybe he didn't notice it as he said the upscaling looks fine to him.

So I uploaded this picture showing a portion of the title screen ... (sentence continues after the piccy)



... and made a new comment in which I linked to it, simply to make him aware of what the issue is and that it doesn't look too nice. Which I didn't write - what I wrote was that "I certainly don't want to tell him how to make his videos." Well, his response was to simply delete the comment. Fair enough. So I just deleted my initial comment and moved on.

My personal view regarding this: I think it looks terrible and in a way does a disservice to any old platform. If someone absolutely not familiar with old computers or consoles sees graphics like that they may well think this is "the real deal". I mean, if one is already going to the effort of using original hardware then they might as well show the screen like it would have looked back in the day (like Zeusdaz does in his videos), "warts and all", possibly with dot-crawl in case of the older models ... the composite mode is fine too. Or upscale it - properly (2x, 3x, whatever). But upscaling with uneven pixels dimensions? No thanks ... could just have used an emulator then. Even anti-aliased/interpolated pixels look better than this (in my view).

Is there a technical term for this kind of upscaling, by the way? I wasn't sure what to call it.

[Morkin]

Yeah, it took me a while before I noticed that some of my own screen grabs were like this because of my emulator zoom... Since that point I've desperately tried to avoid it..(!)

I'll happily play Speccy games on a big TV in widescreen/16:9 ratio (which some people hate!) but at least the 'stretch' is consistent - I don't really like it where the pixels are completely distorted.

[XTM]

Oh look, it's the master of "counting things" himself, I feel honoured. You surely have counted the pixels? Or do you only use this trait over on WOS?

[Morkin]

Ha..! More 'sizing' than 'counting'...

[PeterJ]

I'll happily play Speccy games on a big TV in widescreen/16:9 ratio

I'm so glad it's not just me!

[XTM]

Yeah, 16:9 while not great certainly looks less irksome that this. I mean, the Speccy was ever so slightly "widescreenish" back in the day, right? It wasn't a perfect 4:3 on TVs back then, probably more like 4,5:3 or something?

[4thRock]

The simplest approach is to consider square pixels and use integer scaling - 1x, 2x, 3x, etc.

Interpolation on both axes is problematic, because that's not how CRTs worked...

CRTs displayed a raster image, with some value averaging along each line - a sort of horizontal "pixel" smearing - that depended on pixel size, whether colour was used or not, and the type of connection (composite, RGB, etc)...
But each line was drawn separately, with no vertical smearing. In fact, on the Spectrum you could see some space between scanlines.

So a good simple approximation would be to interpolate horizontally but duplicate vertically

Here's a simulation (1280x960, click for full resolution):


Zoomed in detail (click for full resolution):


But I don't know of any emulator that does this....

[Pobulous]

There's a certain channel that does a lot of ZX81 videos, and on top of the wrong aspect ratio and uneven scaling, the uneven scaling constantly changes to make it even more irritating.

I've found that most channels don't seem to take kindly to these things being pointed out - not sure why...

[AndyC]

But each line was drawn separately, with no vertical smearing. In fact, on the Spectrum you could see some space between scanlines.

That's not entirely true. The mask used on old televisions often displaces alternate "pixels" so if you look at an old CRT very closely you'll see that "straight" lines aren't actually entirely straight. It's also why a lot of people tend to think scanlines added to emulators look "wrong" because it's a very poor imitation of how real displays actually worked.

With high density 4K displays it's actually possible to start getting much closer to a realistic display, including the way red, green and blue guns are aligned separately. It's probably the next big thing in emulation accuracy.

[Ralf]

Yep, resized screenshots look crap.
I also hate screenshots saved as .jpg with all this added blur and artifacts. If someone does it for example in his article,
he immediately becomes a "lamer" for me.

Using proper screenshots can be also practical, if you want to copy and use some graphics or count colours used.

The funny thing is that in the 80s we actually had it originally blurred on our analogue TVs with scanlines etc.

But I guess that I'm using emulation that much so I forgot the 80s and actually prefer the crips, sharp pixels.
In many emulators you can emulate the classic look but I don't like it and never do it.

[p13z]

In many emulators you can emulate the classic look but I don't like it and never do it.

None of them really come close to a true Speccy image using RF on an old TV.
Some add caricature blurriness or distortions, or the horizontal "scanlines" that just weren't there.
The Speccy was codged / tweaked to actually look pretty good on an analogue tuned, analogue scanned typical 1980 TV set.
The image was pretty bold / sharp, with pixel definition, and just enough natural aliasing from the phosphor dots to make it look way better than more expensive similar res setups with dedicated monitors. There was just enough colour bleed through the analogue signals and RF encoding to make Speccy resolution hatching effective. And the phosphor fade constant update of the scanline running made games designed to chase the raster at 50hz feel smoother than many games 40 years on, with displays that jump instantly from one frame to the next.
People forget, chasing sharper images - and living though decades of more modern TVs not coping with the crude Speccy output. I have old TVs for running my Speccy, and keep the modulator in circuit - because nothing looks quite the same or as good for many old games. IMO.

[AndyC]

I think the one advantage of the Speccy's limited colour resolution is that graphics artists were less likely to use colour artifacts in their favour. On more graphically advanced machines like the MegaDrive, the lack of any kind of smoothing can make some games look butt ugly where they never were originally.

[MatGubbins]

Just add it to the long list of stupidly annoying things that users want...
Unevenly scaled pixels
Blurrrrr effects with dot crawl.
16:9 stretched Spectrum screens.
Scan lines and curved CRT effects in emulators

Every effect I switch off, if it can't then I don't use that emulator.
Hell, I even switch off all text smoothing within Windows and all the web browsers that I use - I want to see those pixels as they are and not smudged fuzzy-o-vision, and it's a damn sight easier to read.

Just waiting for the users that wants a burn-in screen effect on their Pac-Man/Space Invader emulator (with a range gauge from 1 year to 40 years).

[Stefan]

Just waiting for the users that wants a burn-in screen effect on their Pac-Man/Space Invader emulator (with a range gauge from 1 year to 40 years).

Hasn't [mention]Tommo[/mention] already included that in CLK?
More in this discussion.

[XTM]

I get the impression MatGubbins didn't read the opening post.

[MatGubbins]

I get the impression MatGubbins didn't read the opening post.

Yup, I did read the opening post, understand and share your frustration of the uneven pixels in the video/screen grabs, I've added a list of the things that I find annoying in emulators, youtube vids/screen grabs in wrong screen ratio.
As to wanting a name for the technical term for the uneven pixels, just call it annoying unsquare out-of-proportion dodgy pixel syndrome.

[p13z]

Every effect I switch off, if it can't then I don't use that emulator.
Hell, I even switch off all text smoothing within Windows and all the web browsers that I use - I want to see those pixels as they are and not smudged fuzzy-o-vision, and it's a damn sight easier to read.

Meanwhile, in the SCREEN$ thread:

[MatGubbins]

Every effect I switch off, if it can't then I don't use that emulator.
Hell, I even switch off all text smoothing within Windows and all the web browsers that I use - I want to see those pixels as they are and not smudged fuzzy-o-vision, and it's a damn sight easier to read.

Meanwhile, in the SCREEN$ thread:

As taken from the youtube video of the game.....

[AndyC]

Obviously part of the problem can be YouTube itself in those cases, as it also applies it's own compression and scaling to submitted videos)

[XTM]

Yup, I did read the opening post, understand and share your frustration of the uneven pixels in the video/screen grabs, I've added a list of the things that I find annoying in emulators, youtube vids/screen grabs in wrong screen ratio.

I see. What confused me was the first part:

Just add it to the long list of stupidly annoying things that users want...
Unevenly scaled pixels
Blurrrrr effects with dot crawl.
16:9 stretched Spectrum screens.
Scan lines and curved CRT effects in emulators

To me this reads like "Unevenly scaled pixels" is one of the things users want in an emulator. Now, I can't imagine anyone wanting pixels to look like that and judging by the poll results so far I'm right ... therefore you adding this to the top of this particular list gave me the impression you had just skimmed the first post, as this one is certainly something users don't want.

[Ast A. Moore]

Is there a technical term for this kind of upscaling, by the way? I wasn't sure what to call it.

Aliasing.

[MarkRJones1970]

I posted a tweet about this a while back after seeing an offender in Retro Gamer mag:
https://twitter.com/MarkRJones1970/stat ... ki1-A&s=19

[XTM]

Thanks [mention]Ast A. Moore[/mention]!

[mention]MarkRJones1970[/mention], that looks bad indeed. And the baddies look like Gary Bracey when he sported the mullet!

By the way, I was reading a few of your recent tweets - here's a better version of that "The Invisible Man" video by Queen (the one with the dozen or so games at the start and the Renegade poster on the wall for those who don't know).

There is a poster for Xeno at 0:45, something by Microdeal at 0:47 (could probably figure it out if one was to look at all Microdeal game inlays) and there are what looks like more game posters to left of the Xeno one ... the bottom one, seen in the top-left corner at 1:34, is Black Lamp by Firebird, it's a bit blurry but I just about recognized it. At 1:49 there is a poster for Romulus by Quicksilva (a C64 game). At 2:35 there is a poster for what appears to be a game by Rainbird (logo in the bottom right of the poster), not sure which one it is. However at 2:37 I could recognize the one below it - it is Trap by Alligata (another C64 game).

Damn, you've brought out the detective in me again! Given more time I'll probably guess the missing ones, but I think there is an edit time limit, so here goes ... submitting.

[MatGubbins]

Microdeal poster at 00:47 is "Lands Of Havoc"
Rainbird poster is "Legend of the Sword"

[presh]

Is there a technical term for this kind of upscaling, by the way? I wasn't sure what to call it.

Aliasing.

The scaling method is called nearest neighbour interpolation, whereas aliasing is the visual artefact which results from this.

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