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Apple Says 'Jelly Scrolling' on iPad Mini 6 is Normal Behavior for LCD Screens

I don't know if this is applicable... but...
I remember years ago writing a Public Access Automation system. It had a smooth-scroll of announcements; upcoming shows, community events, etc. etc.

I had a terrible screen-tearing (jelly) problem with my smooth scroll machine. I realized that it was the way that it re-drew the window; it exhibited exactly the same behavior that you're seeing on the minis.

The way that I fixed that was to have a separate memory space where I did my "scroll" to move my image up a pixel, then I used a machine language call called BITBLT (Bit Block Transfer) to "instantly" update the visible window. The scroll tearing was gone.

It looks like just some lazy programming to me; their redraw routine is inefficient, much like it was in my project, prompting my workaround.
 
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klasma said:
This isn't screen tearing, an unrelated to buffers. The display itself has no buffer, and it can update the state of each pixel only sequentially, one pixel at a time. The graphics hardware sends a stream of pixel data to the display, and the display updates the state of the LCD pixels accordingly. That happens in a line-by-line scanning process, and each pixel is updated once per frame. The buffers on the GPU side ensure that during each such frame update, the display is updated with a consistent image, i.e. no tearing. But the update itself still causes a gradual state transition across the screen from one frame contents to the next, because the screen state can't flip instantly. In addition, the physical LCD pixels take some time to actually change their color in reaction to the state change (pixel response time). The color doesn't flip instantly, but "slowly" fades from the previous color to the new color.

In combination, this causes the display to look as in the photo below (when scrolling). You can see that the pixels are updated from left to right, with the "fading" effect created by the pixel response time. In motion, the human eye perceives the horizontal lines as slanted/skewed, because it merges the upper lines fading in on the right with the lower lines fading out on the left. (I'm not sure if it would be better or worse with a faster or slower response time. A faster repsonse time may actually make it worse.)

1632844285859.png
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That's the issue I just described (along with the resolution) in my response. :)
 
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GBaughma said:
That's the issue I just described (along with the resolution) in my response. :)
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No, iOS and/or the GPU already does buffer as you describe. But the actual physical screen pixels still need to be updated with the contents of that buffer, and because that updating is (necessarily) done sequentially pixel after pixel, rather than all at once, you always have a combination of two frames on the physical screen. This is true for all LCD and OLED displays.
 
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klasma said:
No, iOS and/or the GPU already does buffer as you describe. But the actual physical screen pixels still need to be updated with the contents of that buffer, and because that updating is (necessarily) done sequentially pixel after pixel, rather than all at once, you always have a combination of two frames on the physical screen. This is true for all LCD and OLED displays.
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Well, that doesn't make sense. The way you describe it, the display is a serial device... if that were the case, the system would be completely unable to play any video / games / etc.

The fact that you can watch video without artifacting and screen tearing (such as scrolling credits at the end of a movie) would indicate that it's an issue with their scroll routine, not with the hardware.
 
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GBaughma said:
Well, that doesn't make sense. The way you describe it, the display is a serial device... if that were the case, the system would be completely unable to play any video / games / etc.

The fact that you can watch video without artifacting and screen tearing (such as scrolling credits at the end of a movie) would indicate that it's an issue with their scroll routine, not with the hardware.
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Screens are serial devices. Pixels are not connected individually, but are positioned on a matrix of wires (see e.g. https://en.wikipedia.org/wiki/Liquid-crystal_display#Connection_to_other_circuits). That means individual pixels cannot be addresses simultaneously (because they are on the same wire if they are on the same row or column), but only sequentially one after the other. It would be physically impossible to wire each pixel individually (e.g. having 400.000 wire pairs on the mini 6) with current technology.
 
@GBaughma: See also here:
blurbusters.com

Understanding Display Scan-Out Lag With High Speed Video - Blur Busters

High Speed Video Makes Display Refresh Behaviour Easy To Understand Blur Busters released the high speed video of motion blur reduction in year 2012, and we were the world's first website to measure the input lag of G-SYNC via high speed camera in 2014. New TestUFO Test For High Speed Cameras We...
blurbusters.com blurbusters.com
www.testufo.com

TestUFO: Display Scan Skew - Jelly Effect

TestUFO: Display Scan Skew - Jelly Effect
www.testufo.com www.testufo.com

The first page links to this video with a slow-motion recording of a 60 Hz LCD (see also the reply to the first comment there):

The black-white switching shows how the screen updates from one frame to the next. Note how the transition is smooth (due to pixel reaction time) and not a sharp line as it would be with screen tearing. Due to the smoothness, the human eye generally doesn't notice the "scanning".
 
It’s driving me nuts. I really enjoy using the new Mini in landscape, but just look at this is in portrait- look at the bold text as I scroll quickly, slowly, it’s just sooooo pronounced. And it was like this on all the display units I saw in store recently too.



 
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klasma said:
It's a function of the width of the screen edge along which the refresh occurs, and on the mini 6 the refresh occurs along the short edge, which makes the issue very prominent. It's like how an ascending slope gets steeper the shorter you make the horizontal distance, assuming a fixed vertical height. With the iPad Pros, the 120 Hz also decreases the effect by half. There may be other factors like pixel response time (how fast a pixel reacts to a change in color).
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Which explains why I don't see it on my 10.5" iPad Pro.
 
DMG35 said:
Do the older iPad Mini's do this?
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Yes. My mini 5 jelly scrolls in landscape. My mini 6 jelly scrolls in portrait. Since I use both orientations 50/50, the issue (or lack of) is the same. Maybe Apple optimized the new mini for more landscape use?

Even my new M1 MacBook Pros jellies a bit when scrolling sideways.
 
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ScanTheNavian said:
I'm really hoping Apple does a silent update with a orientation change in the near future. It's just completely unuseable to me with the jelly thing going on. I'm happy for those that don't see it!
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They can’t. The direction of the jelly depends on which side of the LCD the display driver wires are connected.
 
Those who have 120Hz pro motions going not like using non 120Hz screens like the 60Hz Mini 6 and limited 4GB RAM.

I heard that Mini 6 dual speakers will only come on in landscape too!
 
Wrong choice of words. Should say the Feature is Normal and not the Problem is Normal.
 
vartanarsen said:
I dont mind jelly scrolling on mine. Makes it feel more real as you were pulling up a newspaper page the left side lags as you pull up the right side. Makes it feel like a real object. I love Apple
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lol~
I don't know if you're serious or not, but I appreciate the positive spin on it anyways

Particularly the "I love Apple" at the end :D :p 🤟
 
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I'm glad people are finally waking up around here, and seeing Apple for what they are quickly becoming...a second rate tech company. #Sculley #Cook

Buy a Galaxy Z Fold 3, you'll thank me later. It is superior to both the iPhone 13 Pro Max and the iPad Mini 6. You're welcome 😁
 
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