Comment 0 for bug 1788308

Wojciech (wk304) wrote :

The problem affects the integrated display on a Lenovo B50-80 notebook.

Colour banding is visible everywhere on the system, as dithering seems not to be enabled. This issue was not present on non-HWE Ubuntu 16.04, and it showed up after upgrading to Ubuntu 18.04. There was already a bug #1749420 that was resolved ( with very similar symptoms, albeit the make and model of a LCD screen in that case was different. However, the source of this problem is probably the same, since I have checked that pre-4.8.0-rc2 kernels handled dithering correctly, and 4.8.0-rc2 and later kernels already had the bug described. Therefore, I believe that adding another quirk may fix the problem.

I attached the results of running
sudo get-edid | parse-edid in a file named edid.txt
sudo get-edid | edid-decode in a file named edid-decoded.txt.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.15.0-32-generic 4.15.0-32.35
ProcVersionSignature: Ubuntu 4.15.0-32.35-generic 4.15.18
Uname: Linux 4.15.0-32-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
 /dev/snd/controlC0: me 1245 F.... pulseaudio
 /dev/snd/controlC1: me 1245 F.... pulseaudio
Date: Wed Aug 22 00:26:15 2018
HibernationDevice: RESUME=UUID=93b28df5-b453-452b-960d-7173994d778e
InstallationDate: Installed on 2018-08-21 (0 days ago)
InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
MachineType: LENOVO 80EW
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-32-generic root=UUID=a1cd5b8c-2707-4840-858b-3ca12517193b ro quiet splash vt.handoff=1
 Error: command ['pacmd', 'list'] failed with exit code 1: Home directory not accessible: Permission denied
 No PulseAudio daemon running, or not running as session daemon.
 linux-restricted-modules-4.15.0-32-generic N/A
 linux-backports-modules-4.15.0-32-generic N/A
 linux-firmware 1.173.1
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install) 09/02/2016
dmi.bios.vendor: LENOVO
dmi.bios.version: A8CN54WW(V3.07)
dmi.board.asset.tag: NO Asset Tag Lenovo B50-80
dmi.board.vendor: LENOVO
dmi.board.version: 31900058 WIN
dmi.chassis.asset.tag: NO Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Lenovo B50-80
dmi.modalias: dmi:bvnLENOVO:bvrA8CN54WW(V3.07):bd09/02/2016:svnLENOVO:pn80EW:pvrLenovoB50-80:rvnLENOVO:rnLenovoB50-80:rvr31900058WIN:cvnLENOVO:ct10:cvrLenovoB50-80: IDEAPAD 80EW
dmi.product.version: Lenovo B50-80
dmi.sys.vendor: LENOVO