iPad 3/4 Display with Integer Scaling Effects

chanunnaki
Posts: 15
Joined: Tue Jul 07, 2020 1:33 am

iPad 3/4 Display with Integer Scaling Effects

Unread post by chanunnaki »

So I got an iPad 3 retina LCD and drive board and it's awesome, I love that beautiful DPI...
IMG_0211.JPG
IMG_0224.JPG

I'm using the 2048x1536 60Hz (Video mode 13) with integer scaling turned on and trying the Integer Scaling Effects, which is supposed to give you pixel-perfect scanlines, but instead... they look off and uneven. See here:
IMG_0251.JPG
IMG_0263.JPG

I know mode 13 is the newest display mode implemented so perhaps the filters haven't been updated yet...

Has anyone else encountered this issue? Is there a fix?
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aberu
Posts: 13
Joined: Tue Jun 09, 2020 8:34 pm

Re: iPad 3/4 Display with Integer Scaling Effects

Unread post by aberu »

The typical resolutions divided...

1536 / 240 = 6.4 (Genesis/SNES resolution)
1536 / 224 = 6.85 (Genesis/SNES resolution)
1536 / 160 = 9.6 (GBA Resolution)
1536 / 144 = 10.666~ (GB/GBC Resolution)

This is expected behavior then. If the division into the resolution you are doing full-screen into doesn't yield a whole number vertically, then you don't have a 1:1 pixel representation (pixels not perfectly square from top to bottom).

A 1344 vertical resolution display for 224p would look fine if full screen 6x. A 1440p vertical resolution screen would look fine for 240p scaled 6x. I'm not aware of any 1344p resolution displays.

I don't see what advantage 1536p would have for integer scaling in full screen, what system's resolution are you trying to match?

Is this running in the Genesis/SNES 240p suite as a test?

this is why 1440p is seen as a goldilox zone, because 240p scales 6x to it full screen, 160 9x, and 144 10x. But 224p is still dead in the water as always :P

chanunnaki
Posts: 15
Joined: Tue Jul 07, 2020 1:33 am

Re: iPad 3/4 Display with Integer Scaling Effects

Unread post by chanunnaki »

So I went through each of the default modes and made this list:

Column 1 = video_mode number
Column 2 = resolution
Column 3 = Aspect ratio
Column 4 = Supported by the DIsplay/Drive Board combo.
Screenshot 2020-07-31 at 22.56.57.png
The board I have is from AliExpress which can be found here:
https://www.aliexpress.com/item/4000042 ... 4c4d4qyPg6

and was recommended by SmokeMonster in this tweet:
https://twitter.com/SmokeMonsterTWI/sta ... 0226356224
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aberu
Posts: 13
Joined: Tue Jun 09, 2020 8:34 pm

Re: iPad 3/4 Display with Integer Scaling Effects

Unread post by aberu »

That's just video mode support. That has nothing to do with integer scaling really. I think someone should make a better video on this. But here's one sort of going over it..

https://www.youtube.com/watch?v=HPJFnwKufb0

You don't understand the problem I'm describing to you.

Your screen has 1536 "square" dots vertically.

You are trying to scale up square dots into that display unevenly, so when you do that, some of them are not square. Even with nearest neighbor (which helps), you will still have imperfect squares, merely an illusion to make them look square (unless the division of the source video being scaled into your native resolution of your display equals a whole number).

What you are wanting, perfectly even lines when whole numbers cannot be achieved by division, is mathematically impossible.

Use the integer scaling option if you want good looking scanlines and learn to accept black borders on the top and bottom, or change the filters till you see something you are happy with. :P

EDIT: For clarity for GBA...

1536 / 160 = 9.6

9 * 160 = 1440

1536 - 1440 = 96.

So you either have 96 pixels worth of uneveness that you are stretching squares out over, or you turn on integer scaling and you subtract 48 pixels from the top and bottom of the screen as a black border.

EDIT2: Another edit since I forgot to mention...

A video mode is not the same thing as a native resolution. If you play on a screen that is 4k native in 1536p, the squares will not be even either.

chanunnaki
Posts: 15
Joined: Tue Jul 07, 2020 1:33 am

Re: iPad 3/4 Display with Integer Scaling Effects

Unread post by chanunnaki »

You don't understand the problem I'm describing to you.
I actually made my second post before I saw your first one, so it wasn't in response to your post. What you wrote is extremely informative though, and I'm taking my time going through it. I had no idea this is how the integer scaling worked, but after seeing your post, I've got a lot better understanding and it makes a lot of sense.

rhester72
Posts: 131
Joined: Thu Jun 11, 2020 2:31 am

Re: iPad 3/4 Display with Integer Scaling Effects

Unread post by rhester72 »

One thing I learned the hard way (and still haven't worked out in my head why this is) - the vertical scale must be at least 3x for (custom filter) scanlines to work. 2x is *not* enough.

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JBeau
Posts: 7
Joined: Sun May 24, 2020 8:00 pm

Re: iPad 3/4 Display with Integer Scaling Effects

Unread post by JBeau »

Soltan shared a pack of filters that work with 2x a while ago. Maybe ask him to share it here :)

edit: see end of this thread: viewtopic.php?f=13&t=745

rhester72
Posts: 131
Joined: Thu Jun 11, 2020 2:31 am

Re: iPad 3/4 Display with Integer Scaling Effects

Unread post by rhester72 »

Thanks for the pointer!

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