Temporal dithering and impaired graphical performance started appearing on Intel HD 530 graphics

[Patrick Wigmore]

I am experiencing a regression in linux-image-generic-hwe-16.04 with Intel HD Graphics 530 (Core i5-6600T), starting in 4.13.0-43 (considering only kernels which appear in my GRUB menu).

Some form of spatio-temporal dithering has been enabled. This is causing a shimmering effect and visible dithering patterns (like woven textile) which are noticeable on photographs and areas of similar colour. 1px borders in the UI can appear to have a "marching ants" effect.

The effect is visible under Xorg if the displayed colours are suitable to trigger it.

The effect is also visible in a virtual console (Ctrl+Alt+F1) if suitable colours are displayed, but it seems that the presence of the effect in virtual consoles predates its appearance under Xorg and the reporting of this bug, going back at least as far as 4.13.0-31, but with no reason to believe it does not go back further (besides lack of testing).

Reverting from 4.13.0-43 by booting 4.13.0-41 eliminates the temporal dithering in Xorg.

This occurs on a (presumed) 6bpp laptop LCD panel, so dithering is necessary, but in previous kernels only a form of spatial dithering is applied, which is less visually obvious.

Concurrent with the temporal dithering, I have also noticed general poor graphical performance with the affected kernels. E.g. 50fps and 60fps video playback is choppy, sometimes slow redraw and other graphical glitches on UI elements. Like the temporal dithering, these additional problems disappear if I revert to 4.13.0-41.
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InstallationDate: Installed on 2016-09-16 (634 days ago)
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[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.17 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.17

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1776642

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Patrick Wigmore (patrick-wigmore)]

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[Patrick Wigmore (patrick-wigmore)]

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[Patrick Wigmore (patrick-wigmore)]

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[Patrick Wigmore (patrick-wigmore)]

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[Patrick Wigmore (patrick-wigmore)]

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[Patrick Wigmore (patrick-wigmore)]

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[Patrick Wigmore (patrick-wigmore)]

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[Patrick Wigmore (patrick-wigmore)]

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[Patrick Wigmore (patrick-wigmore)]

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[Patrick Wigmore (patrick-wigmore)]

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[Patrick Wigmore (patrick-wigmore)]

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[Patrick Wigmore (patrick-wigmore)]

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[Patrick Wigmore (patrick-wigmore)]

I can confirm that the temporal dithering is present when running mainline kernel 4.17.0-041700-generic.

[Patrick Wigmore (patrick-wigmore)]

Concurrent with the temporal dithering, I have also noticed general poor graphical performance with the affected kernels. E.g. 50fps and 60fps video playback is choppy, sometimes slow redraw and other graphical glitches on UI elements. Like the temporal dithering, these additional problems disappear if I revert to 4.13.0-41.

[Patrick Wigmore (patrick-wigmore)]

In 4.15.0-25-generic, the symptoms have changed. The objectionable temporal dithering persists in virtual terminals (e.g. Ctrl+Alt+F1) but under KDE Plasma 5 it has disappeared or become imperceptible, and high fps video playback is no longer choppy.

However, with this kernel, the blurring effect applied to semi-transparent Plasma widget backgrounds has stopped working (replaced with opaque background).

[Patrick Wigmore (patrick-wigmore)]

Under 4.18-rc3 from http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.18-rc3/ the symptoms appear identical to those under 4.15.0-25-generic.

I tested mainline 4.17, 4.17.2, 4.17.3, 4.17.4 and 4.18-rc2 from the kernel.ubuntu.com, which all displayed the original symptoms reported for this bug.

Correction/clarification: Previously, I failed to test whether the temporal dithering appeared in virtual consoles under 4.13.0-41. I only tested to see whether it affected virtual consoles on kernels where it also affected X. It turns out that the dithering has always been present in virtual consoles at least as far back as 4.13.0-31, but it did not appear under X until 4.13.0-43. I will amend the bug description to reflect this.

The issue with semi-transparent backgrounds in Plasma widgets may be unrelated, as this is now appearing under all kernels I've tried booting.

[Patrick Wigmore (patrick-wigmore)]

So, to summarise, the bug in regard to Xorg seems to be fixed in 4.15.0-25 and in 4.18-rc3. The bug appears to have always been present under virtual terminals (only tested as far back as 4.13.0-31.

[Patrick Wigmore (patrick-wigmore)]

I've marked this bug as fix released since that appears to be the case.
The issues I mentioned regarding semi-transparent backgrounds seem to be an unrelated bug #1780664 in mesa.

[Paul F (pf1985)]

Question link > https://askubuntu.com/questions/1190609/eye-strain-and-nausea-when-running-18-04-1-on-intel-i915-graphics

I have eye strain and headaches using Ubuntu which I believe is caused by temporal dithering being enabled. I have posted on AskUbuntu and it was suggested I update this bug report with some information.

*-display
       description: VGA compatible controller
       product: Core Processor Integrated Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 12
       width: 64 bits
       clock: 33MHz
       capabilities: msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:26 memory:fb800000-fbbfffff memory:d0000000-dfffffff ioport:dc00(size=8) memory:c0000-dffff

Linux paul-Aspire-X3950 5.0.0-36-generic #39~18.04.1-Ubuntu SMP Tue Nov 12 11:09:50 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

00:02.0 VGA compatible controller: Intel Corporation Core Processor Integrated Graphics Controller (rev 12)

I would like the option to turn dithering off. I believe this can be performed using xrandr on Nvidia cards however no such solution is available for Intel.

[Patrick Wigmore (patrick-wigmore)]

Paul F, if you think you have found a bug, then you need to make a new, separate bug report under a new bug number, because your hardware is different and you are not discussing a regression in kernel 4.13.0-43, which is what this particular bug was about.

Here are some instructions for reporting kernel bugs in Ubuntu: https://wiki.ubuntu.com/Kernel/Bugs