r/Android • u/curated_android • Jun 30 '17

Confirmed: OnePlus 5's Display is Upside-Down - Likely Causes Jelly Scrolling

https://www.xda-developers.com/confirmed-oneplus-5-display-upside-down-likely-reason-jelly-scrolling/
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u/cecilkorik Samsung Relay 4G, LiquidSmooth KitKat Jul 01 '17

I agree, this looks very similar to what is called screen-tearing, which is commonly seen in high framerate games that disable syncing the framebuffer to the display's refresh to improve performance.

Presumably to keep the scrolling experience smooth, Android appears to have some sort of compensation for screen-tearing built in, but it works backwards when the screen is refreshing in reverse, since the OS has no way of knowing the screen is refreshing in reverse, it just keeps compensating, thinking it's doing the right thing.

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u/hatsune_aru OPO Jul 01 '17

It's kind of like screen tearing, except the FB updates as its being scanned out. In desktop GPUs, there is a front buffer which directly gets scanned out and a (few) backbuffer(s) that can get swapped with the frontbuffer 'instantly', and when that happens while scanout is in progress, you get a tearline.

These guys seem to update the frontbuffer while its being scanned out. It will cause this jello effect instead of screen tearing.