Image Scaling On A Fixed Pixel Display

[DaveC]

Since this topic of scaling comes up alot here is a basic explanation of what its effects are on an LCD. Note that it doesn't include smoothing which adds a level of blurr to the scaled image to attempt to hide the artifacts.

It also explains why the 320 x 240 screen on the GP32/GP2X is pretty much ideal for emulation. A 640 x 480 would be best but we know that wouldn't be cost effective for the GP2X at this time. 320 x 240 is second best, Zodiac and PSP res would be the worst.

 

[iignotus]

Wow this thread is pretty useless. First of all, bickering about screens between handhelds = lose. Second of all, you seem to have no concept of pixel size. Every screen is 'ideal' for emulation as long as it has at least as many pixels as the original.

 

[DaveC]

Wow this thread is pretty useless. First of all, bickering about screens between handhelds = lose. Second of all, you seem to have no concept of pixel size. Every screen is 'ideal' for emulation as long as it has at least as many pixels as the original.

​

It is not about "bickering" it is just some information.

You missed the whole point completely. Every screen is NOT ideal for emulation as long as it has enough pixels. Some require scaling if the pixel size is smaller and is higher res. When you scale you get the distortion as shown above.

 

[iignotus]

You missed the whole point completely.

​

I sure didn't.

Every screen is NOT ideal for emulation as long as it has enough pixels. Some require scaling if the pixel size is smaller and is higher res. When you scale you get the distortion as shown above.

​

ANY screen is not ideal for all emulation, either. Genesis is one of the few examples that pans out to having a perfect 4:3 resolution. And even the Genesis strays from this resolution from time to time.

Nothing requires scaling. You'll just have a smaller image, is all. Once again, any screen is 'ideal' for emulation of an older system as long as it doesn't remove any information during display, i.e, it has as many pixels.

 

[Hanz™]

Nothing requires scaling. You'll just have a smaller image, is all. Once again, any screen is 'ideal' for emulation of an older system as long as it doesn't remove any information during display, i.e, it has as many pixels.

DaveC's point exactly.

 

[Vimacs]

another proof that we need crts in handhelds...

 

[Aaaaaaaa]

You missed the whole point completely.

​

I sure didn't.

Every screen is NOT ideal for emulation as long as it has enough pixels.  Some require scaling if the pixel size is smaller and is higher res.  When you scale you get the distortion as shown above.

​

ANY screen is not ideal for all emulation, either. Genesis is one of the few examples that pans out to having a perfect 4:3 resolution. And even the Genesis strays from this resolution from time to time.

Nothing requires scaling. You'll just have a smaller image, is all. Once again, any screen is 'ideal' for emulation of an older system as long as it doesn't remove any information during display, i.e, it has as many pixels.

​

the link in your sig is broke

 

[DaveC]

ANY screen is not ideal for all emulation, either. Genesis is one of the few examples that pans out to having a perfect 4:3 resolution. And even the Genesis strays from this resolution from time to time.

Nothing requires scaling. You'll just have a smaller image, is all. Once again, any screen is 'ideal' for emulation of an older system as long as it doesn't remove any information during display, i.e, it has as many pixels.

​

Well yeah but if you run something like Genesis on a 320 x 480 screen the image is much smaller than when on a 320 x 240 at 1:1, again see above.

There are screen sizes/resolution/aspect ratio combinations that just come out *better* for running emus than others even if not "perfect". That is the point.

Just like below see how some give smaller images at 1:1. That was just part of the point of this.

 

[deadlychicken22]

Thanks for the diagram, davec. iignotus, what you're saying doesn't make any sense to me. Why would you want to play it smaller or stretched when you can play it perfect at the gp32's res? . Davec's completely right.

 

[DaveC]

another proof that we need crts in handhelds...

​

That would be the best as they are not fixed pixel. Now only to find a CRT small enough and that uses little power..

 

[sam fisher]

ya hes saying that so if we want full screen you have to have a certain type of screen or you get crappy artifactial scaling so stfu!

 

[DaveC]

Let's not flame. That wasn't the point of this. There just seemed to be some confusion about res, pixel size, scaling etc and this was supposed to clear some of that up. iignotus started off by claiming that this was for "bickering". It wasn't supposed to be for that let's not turn it into his prediction

 

[Tobriand]

Nice diagram, DaveC .

Ignotus, clearly some screens are better for some systems, but the vast majority of 16 bit consoles and pre-them era use roughly 320x240, hence why its a good one. Genesis pans out, Snes too, Amiga, ST, PCE, Master System, NES... quite a few.

If you want an example of why this is important, play a stretched gamegear game on a GP32 - an RPG would be good - and tell me it doesn't look a little (if not totally) strange. Now imagine that effect with all of the above systems when stretched to fullscreen on PSP, Zodiac, and many others (generally anything with a fixed widescreen non-qvga resolution).

Sure you can play it without stretching but since the pixels on a PSP or Palm or Zodiac or... lots of others are smaller, the resultant image is too. Just coz its high res don't mean it's big, after all.

Was going to suggest DaveC dig out the Genesis pictures, but I've noticed they're already there... can't have loaded when I was reading the thread lol.

 

[iignotus]

Thanks for the diagram, davec. iignotus, what you're saying doesn't make any sense to me. Why would you want to play it smaller or stretched when you can play it perfect at the gp32's res? . Davec's completely right.

​

Ok, I'll explain it further.

Let's just say we're comparing PSP and GP2X's screens, right? And for this comparison, we'll be talking about Genesis emulation.

The PSP's screen is 4.3". The GP2X's screen is 3.5". The PSP's screen is physically larger, and can be considered 'better'.

The PSP's screen resolution is 480x272, almost perfectly 16:9 (off by a mere 2 vertical pixels). The GP2X's screen resolution is 320x240, a perfect 4:3 ratio. The PSP's resolution is larger, and can be considered better.

The original resolution of a Sega Genesis screen, directly from the console, is 256x192 (in mode 4). A perfect 4:3 ratio. However, it requires scaling to fit the GP2X's 320x240 screen resolution. This requires every 4th horizontal and vertical pixel to be doubled. Oops! However, since it's the same ratio, after scaling, you will no longer see black borders anywhere.

But wait, I hear you say "You said that the Genesis strays from the 4:3 ratio! You must be wrong!" Well, no. It's not common, but technically, the Genesis' hardware can go into mode 5 and render a screen that is 256x224 -- no longer 4:3 ratio. Genesis PAL roms can technically hit upto 320x240.

But see, this 256x192 resolution will display PERFECTLY on a PSP screen. It will look absolutely wonderful. 256 fits into 480, and 192 fits into 272. You'll have a perfect render of the screen. You'll see lots of black nothing around the image, but the game will look perfect. However, since the PSP's screen pitch is smaller than the GP2X's, the actual, physical image you see will be smaller on a PSP than on a GP2X, since the GP2X has a smaller resolution.

And also like I said, very many consoles don't have a 4:3 display ratio, and NONE of them have a 320x240 resolution that I can think of off the top of my head.

Scaling is not needed unless you want a bigger image. I know you're saying "well duh that's what we want". Well that's fine. But you'll have to scale on the GP2X just as you will the PSP for nearly every system out there that you want to emulate -- only, you do a bit less scaling on the GP2X.

Aspect ratio of an image does not indicate whether or not you have to scale an image.

 

[Hanz™]

Scaling is not needed unless you want a bigger image. I know you're saying "well duh that's what we want". Well that's fine. But you'll have to scale on the GP2X just as you will the PSP for nearly every system out there that you want to emulate -- only, you do a bit less scaling on the GP2X.

Nicely put.
We want a bigger image with as little scaling as possible, so the GP2X for us is better than the PSP. Is that what you were getting at?

 

[deadlychicken22]

When you say the psp is better than the gp32 playing genesis, that is because on the psp you aren't scaling the image at all, but if you didn't scale it on the gp32 wouldn't the gp32's then be better than the psp's because it will be physically larger?

 

[Hanz™]

but if you didn't scale it on the gp32 wouldn't the gp32's then be better than the psp's because it will be physically larger?

Yeah, but you wouldn't see all of the screen.

 

[deadlychicken22]

You mean it would only take up part of the screen, right? Isn't that what he's talking about though?

 

[iignotus]

We want a bigger image with as little scaling as possible, so the GP2X for us is better than the PSP. Is that what you were getting at?

DaveC said that the GP2X's display is perfect. Well it is and it isn't. It's a better ratio than the PSP's; it's more accurate. However, you STILL HAVE TO SCALE. And this is just for Genesis.

Ignotus, clearly some screens are better for some systems, but the vast majority of 16 bit consoles and pre-them era use roughly 320x240, hence why its a good one. Genesis pans out, Snes too, Amiga, ST, PCE, Master System, NES... quite a few.

NES doesn't, PC Engine doesn't, Atari ST doesn't. Master system sometimes does, sometimes doesn't. And I'm not sure which Amiga computer you're talking about emulating.

ya hes saying that so if we want full screen you have to have a certain type of screen or you get crappy artifactial scaling so stfu!

And yes, please don't start profane arguments when you have nothing whatsoever to contribute.

 

[bourbon]

Thanks for the diagram, davec. iignotus, what you're saying doesn't make any sense to me. Why would you want to play it smaller or stretched when you can play it perfect at the gp32's res? . Davec's completely right.

​

Ok, I'll explain it further.

Let's just say we're comparing PSP and GP2X's screens, right? And for this comparison, we'll be talking about Genesis emulation.

The PSP's screen is 4.3". The GP2X's screen is 3.5". The PSP's screen is physically larger, and can be considered 'better'.

The PSP's screen resolution is 480x272, almost perfectly 16:9 (off by a mere 2 vertical pixels). The GP2X's screen resolution is 320x240, a perfect 4:3 ratio. The PSP's resolution is larger, and can be considered better.

The original resolution of a Sega Genesis screen, directly from the console, is 256x192 (in mode 4). A perfect 4:3 ratio. However, it requires scaling to fit the GP2X's 320x240 screen resolution. This requires every 4th horizontal and vertical pixel to be doubled. Oops! However, since it's the same ratio, after scaling, you will no longer see black borders anywhere.

But wait, I hear you say "You said that the Genesis strays from the 4:3 ratio! You must be wrong!" Well, no. It's not common, but technically, the Genesis' hardware can go into mode 5 and render a screen that is 256x224 -- no longer 4:3 ratio. Genesis PAL roms can technically hit upto 320x240.

But see, this 256x192 resolution will display PERFECTLY on a PSP screen. It will look absolutely wonderful. 256 fits into 480, and 192 fits into 272. You'll have a perfect render of the screen. You'll see lots of black nothing around the image, but the game will look perfect. However, since the PSP's screen pitch is smaller than the GP2X's, the actual, physical image you see will be smaller on a PSP than on a GP2X, since the GP2X has a smaller resolution.

And also like I said, very many consoles don't have a 4:3 display ratio, and NONE of them have a 320x240 resolution that I can think of off the top of my head.

Scaling is not needed unless you want a bigger image. I know you're saying "well duh that's what we want". Well that's fine. But you'll have to scale on the GP2X just as you will the PSP for nearly every system out there that you want to emulate -- only, you do a bit less scaling on the GP2X.

Aspect ratio of an image does not indicate whether or not you have to scale an image.

​

Bigger dosent mean better

And dave thats a good break down of damn near every thing to do with hand held lcd screens next week can you do memory devices or buttons :lol:

Bourbon