Public bug reported: 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 (https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1749420) 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 and 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 AudioDevicesInUse: USER PID ACCESS COMMAND /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 PulseList: 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. RelatedPackageVersions: 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) dmi.bios.date: 09/02/2016 dmi.bios.vendor: LENOVO dmi.bios.version: A8CN54WW(V3.07) dmi.board.asset.tag: NO Asset Tag dmi.board.name: 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: dmi.product.family: IDEAPAD dmi.product.name: 80EW dmi.product.version: Lenovo B50-80 dmi.sys.vendor: LENOVO ** Affects: linux (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug bionic visual-quality ** Attachment added: "edid-decoded.txt" https://bugs.launchpad.net/bugs/1788308/+attachment/5178901/+files/edid-decoded.txt ** Attachment removed: "WifiSyslog.txt" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1788308/+attachment/5178916/+files/WifiSyslog.txt -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1788308 Title: [Regression] Colour banding appears on Lenovo B50-80 integrated display To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1788308/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
