Incorrect physical size detected for LG 43UD79-B

[Mikko Rantalainen]

I have monitor LG 43UD79-B and xrandr cannot correctly detect the dimensions of the monitor:

$ xrandr
Screen 0: minimum 8 x 8, current 3840 x 2160, maximum 32767 x 32767
DVI-D-0 disconnected (normal left inverted right x axis y axis)
HDMI-0 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 connected primary 3840x2160+0+0 (normal left inverted right x axis y axis) 600mm x 340mm
   3840x2160 60.00*+ 30.00
   2560x1440 59.95
   1920x1080 60.00 59.94
   1600x900 60.00
   1280x1024 60.02
   1280x800 59.81
   1280x720 60.00 59.94
   1152x864 59.96
   1024x768 60.00
   800x600 60.32
   720x480 59.94
   640x480 59.94 59.93
DP-3 disconnected (normal left inverted right x axis y axis)

According to the LG spec (https://www.lg.com/us/monitors/lg-43UD79-B-4k-uhd-led-monitor) the monitor pixel pitch is 0.2451 x 0.2451 mm so the actual panel size should be 941.184 x 529.416 mm instead of reported "600mm x 340mm".

The monitor is connected via Nvidia GTX 1060 (6 GB) in case it makes a difference.

Also, this monitor has BGR subpixel structure and it seems that every application will incorrectly default to RGB subpixel structure. I'm not sure if this information is supposed to be available via xrandr.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: x11-xserver-utils 7.7+7
ProcVersionSignature: Ubuntu 4.15.0-51.55~16.04.1-lowlatency 4.15.18
Uname: Linux 4.15.0-51-lowlatency x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
.proc.driver.nvidia.gpus.0000.01.00.0: Error: [Errno 21] Is a directory: '/proc/driver/nvidia/gpus/0000:01:00.0'
.proc.driver.nvidia.registry: Binary: ""
.proc.driver.nvidia.version:
 NVRM version: NVIDIA UNIX x86_64 Kernel Module 384.130 Wed Mar 21 03:37:26 PDT 2018
 GCC version: gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.11)
.proc.driver.nvidia.warnings.fbdev:
 Your system is not currently configured to drive a VGA console
 on the primary VGA device. The NVIDIA Linux graphics driver
 requires the use of a text-mode VGA console. Use of other console
 drivers including, but not limited to, vesafb, may result in
 corruption and stability problems, and is not supported.
.tmp.unity_support_test.0:

ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
BootLog:

CompizPlugins: [core,composite,opengl,compiztoolbox,decor,regex,mousepoll,move,resize,imgpng,wall,animation,grid,fade,place,vpswitch,gnomecompat,session,workarounds,expo,scale,ezoom]
CompositorRunning: None
CurrentDesktop: MATE
Date: Wed Jun 26 10:06:35 2019
DistUpgraded: 2016-06-10 11:06:21,514 WARNING no activity on terminal for 300 seconds (Applying changes)
DistroCodename: xenial
DistroVariant: ubuntu
DkmsStatus:
 bbswitch, 0.8, 4.15.0-50-lowlatency, x86_64: installed
 bbswitch, 0.8, 4.15.0-51-lowlatency, x86_64: installed
 nvidia-384, 384.130, 4.15.0-50-lowlatency, x86_64: installed
 nvidia-384, 384.130, 4.15.0-51-lowlatency, x86_64: installed
GraphicsCard:
 NVIDIA Corporation GP106 [GeForce GTX 1060 6GB] [10de:1c03] (rev a1) (prog-if 00 [VGA controller])
   Subsystem: ASUSTeK Computer Inc. Device [1043:865b]
InstallationDate: Installed on 2015-02-23 (1583 days ago)
InstallationMedia: Ubuntu 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1)
MachineType: System manufacturer System Product Name
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-51-lowlatency root=UUID=254cacdb-f61b-45a6-9885-37afd2b598ce ro libata.noacpi=1 quiet splash vt.handoff=7
SourcePackage: x11-xserver-utils
UpgradeStatus: Upgraded to xenial on 2016-06-10 (1110 days ago)
dmi.bios.date: 02/04/2013
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 1101
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: P8H77-M PRO
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: Rev X.0x
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr1101:bd02/04/2013:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKCOMPUTERINC.:rnP8H77-MPRO:rvrRevX.0x:cvnChassisManufacture:ct3:cvrChassisVersion:
dmi.product.family: To be filled by O.E.M.
dmi.product.name: System Product Name
dmi.product.version: System Version
dmi.sys.vendor: System manufacturer
version.compiz: compiz 1:0.9.12.3+16.04.20180221-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.91-2~16.04.1
version.libgl1-mesa-dri: libgl1-mesa-dri 18.0.5-0ubuntu0~16.04.1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 18.0.5-0ubuntu0~16.04.1
version.nvidia-graphics-drivers: nvidia-graphics-drivers-* N/A
version.xserver-xorg-core: xserver-xorg-core N/A
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati N/A
version.xserver-xorg-video-intel: xserver-xorg-video-intel N/A
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau N/A
xserver.bootTime: Tue Jun 18 10:32:33 2019
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:

xserver.version: 2:1.19.6-1ubuntu4.1~16.04.2

[Mikko Rantalainen (mira)]

Additional info:
If I run
$ xrandr --dpi 104
then xdpyinfo will display correct dimensions. However, xrandr keeps displaying the incorrect physical dimensions.

[Mikko Rantalainen (mira)]

Possible problem caused by incorrect physical dimensions:
The default mouse cursor is huge (e.g. on desktop). However, most applications have normal sized cursor while the cursor hovers above the application.

[Daniel van Vugt (vanvugt)]

Using the EDID data your monitor reports in the Xrandr.txt attachment above I get the same answer
of 60x34cm so that is what the hardware is advertising itself as. Indeed that would make it 27.15 inches diagonal.

So this is a bug IN your hardware, sorry. You might be able to get a firmware update from LG. Most likely they are using the same firmware in their 27" monitors and forgot to change the dimensions for your 43" model.

---

EDID version: 1.4
Manufacturer: GSM Model 23305 Serial Number 259449
Made in week 3 of 2019
Digital display
10 bits per primary color channel
DisplayPort interface
Maximum image size: 60 cm x 34 cm
Gamma: 2.20
DPMS levels: Standby
Supported color formats: RGB 4:4:4, YCrCb 4:4:4, YCrCb 4:2:2
Default (sRGB) color space is primary color space
First detailed timing includes the native pixel format and preferred refresh rate
Color Characteristics
  Red: 0.6523, 0.3349
  Green: 0.3046, 0.6367
  Blue: 0.1484, 0.0615
  White: 0.3134, 0.3291
Established Timings I & II
    640x480 59.940 Hz 4:3 31.469 kHz 25.175 MHz (DMT)
    800x600 60.317 Hz 4:3 37.879 kHz 40.000 MHz (DMT)
   1024x768 60.004 Hz 4:3 48.363 kHz 65.000 MHz (DMT)
Standard Timings
   1152x864 59.959 Hz 4:3 53.783 kHz 81.750 MHz (EDID 1.4 source: CVT)
   1152x864 60.000 Hz 4:3 53.700 kHz 81.624 MHz (EDID 1.3 source: GTF)
   1280x1024 60.020 Hz 5:4 63.981 kHz 108.000 MHz (DMT)
   1280x720 60.000 Hz 16:9 45.000 kHz 74.250 MHz (DMT)
   1600x900 60.000 Hz 16:9 60.000 kHz 108.000 MHz (DMT, RB)
   1920x1080 60.000 Hz 16:9 67.500 kHz 148.500 MHz (DMT)
   1280x800 59.810 Hz 16:10 49.702 kHz 83.500 MHz (DMT)
Detailed mode: Clock 533.250 MHz, 600 mm x 340 mm
               3840 3888 3920 4000 ( 48 32 80)
               2160 2214 2219 2222 ( 54 5 3)
               +hsync -vsync
               VertFreq: 59.997 Hz, HorFreq: 133.312 kHz
Detailed mode: Clock 266.640 MHz, 600 mm x 340 mm
               3840 3848 3992 4000 ( 8 144 8)
               2160 2214 2219 2222 ( 54 5 3)
               +hsync -vsync
               VertFreq: 30.000 Hz, HorFreq: 66.660 kHz
Display Range Limits
  Monitor ranges (GTF): 56-61 Hz V, 30-135 kHz H, max dotclock 560 MHz
Display Product Name: LG Ultra HD
Has 1 extension block
Checksum: 0x2a

----------------

CTA-861 Extension Block Revision 3
Basic audio support
Supports YCbCr 4:4:4
Supports YCbCr 4:2:2
1 native detailed modes
13 bytes of CTA data blocks
  Video Data Block
     1920x1080 60.000 Hz 16:9 67.500 kHz 148.500 MHz (VIC 16, native)
     1280x720 60.000 Hz 16:9 45.000 kHz 74.250 MHz (VIC 4)
      720x480 59.940 Hz 16:9 31.469 kHz 27.000 MHz (VIC 3)
      640x480 59.940 Hz 4:3 31.469 kHz 25.175 MHz (VIC 1)
  Audio Data Block
    Linear PCM, max channels 2
      Supported sample rates (kHz): 48 44.1 32
      Supported sample sizes (bits): 24 20 16
  Speaker Allocation Data Block
    Speaker map:
      FL/FR - Front Left/Right
Detailed mode: Clock 148.500 MHz, 600 mm x 340 mm
               1920 2008 2052 2200 ( 88 44 148)
               1080 1084 1089 1125 ( 4 5 36)
               +hsync +vsync
       ...