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Input lag and possible fix (works for me).

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iKlutz

Senior Member
Feb 9, 2013
708
196
London
OnePlus 7T Pro
I don't know if anybody else here has suffered this, but I've read several times when googling, that many XZP devices came with input lag out of the box. My device has always suffered with this, and flashing custom ROMs didn't seem to make a difference.

Input lag means that sometimes, keystrokes/touches are completely missed and sometimes scrolling misses too.

I unlocked my bootloader really early on, so I never wanted to send it back as I'm sure this voids my warranty.

I tested for a faulty digitizer using various screen input test apps from playstore, and they usually don't show any areas of the screen as faulty. This has always made me believe that it was most probably a software issue.
Today I discovered that yes indeed, my issue is definitely a software issue.

THE FIX:
Changing the screen resolution to 4k (3840x2160), and DPI to 821.

I've tried this before but never noted the difference in touch input. Perhaps because I wasn't looking for it.

Today I tried it again and much to my surprise, this time I noticed a HUGE improvement to input sensitivity and for now has 100% alleviated the problem. Typing, tapping and scrolling works perfect now.

This is most likely caused by the screen having to rescale pixels from 1080p to 2160p, making extra work for the CPU, but I'm no expert so I might be wrong. But it works for me.

I'll also note that I'm using Turbo ROM p75B now, and the input delay was still there until changing the resolution.

I'd like it if somebody who has suffered the same issue could provide feedback, I really hope this helps you too, as this was the only real issue that have me buyers regret, and it now works wonderfully.

Cheers.

Edit: I do believe this topic might be better recognised in the guides and discussions category. If so, could a mod please move it there.
 
Last edited:

iArvee

Senior Member
Apr 23, 2014
799
274
Manila
Luckily I haven't had this input lag issue. However, I do get input lag if I have stamina mode turned on, and set to battery time preferred.

Just so you know, you do know that you're only emulating 4k, right? The only way to set the display to 4k is on AOSP.
 

iKlutz

Senior Member
Feb 9, 2013
708
196
London
OnePlus 7T Pro
Yes I understand that it's only "emulating" 4k and that it's not native 4k. It also uses more battery, which would suggest higher CPU usage, which in part contradicts my theory about rescaling causing input lag.

Perhaps it is something to do with the "touch map" (I can't think of the term), the software/grid that maps out the touchable area to the digitizer, having to resize from 1080p to 2160p, making the grid inaccurate? But it wouldn't make sense as to why it only affects some devices.

Also, I do not have stamina mode enabled as it's almost pointless in today's phones. I believe limiting processing speed only makes process queus take longer to finish, which means that CPU takes longer to idle. It only saves a negligible amount of battery unless your phone screen is off for 80% of the day. Almost as pointless as closing applications and cleaning RAM, as your phone will just use more battery rebuilding caches and restarting processes.
 

iKlutz

Senior Member
Feb 9, 2013
708
196
London
OnePlus 7T Pro
@iKlutz I can't seem to find the resolution settings lol
There are some threads here that explain various methods to change the VM resolution and scaling. If you're unfamiliar with ADB, I suggest you read very carefully and take precautions, as setting the resolution wrong could make it really difficult to reverse the procedure and we currently don't have a way to make TWRP backups.