Video projector not detected anymore (under Xorg 1.18.4)

Thu Nov 3 14:41:52 UTC 2016

Hi Folks,

I'm assistant professor and I teach with the same video projectors
since years (with each of the last three kubuntu releases on my
laptop). I have a strange trouble since my last kubuntu update (2
weeks ago). Now I'm under kubuntu 16.10, with a 1.18.4 Xorg server:

>8===================================================================8<

phil at IUTNC-DOSCH log % uname -a03-11-2016 15:29:14
Linux IUTNC-DOSCH 4.8.0-26-generic #28-Ubuntu SMP Tue Oct 18 14:39:52 
UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

phil at IUTNC-DOSCH log % Xorg -version

X.Org X Server 1.18.4
Release Date: 2016-07-19
X Protocol Version 11, Revision 0
Build Operating System: Linux 3.13.0-95-generic x86_64 Ubuntu
Current Operating System: Linux IUTNC-DOSCH 4.8.0-26-generic #28-Ubuntu 
SMP Tue Oct 18 14:39:52 UTC 2016 x86_64
Kernel command line: BOOT_IMAGE=/boot/vmlinuz-4.8.0-26-generic 
root=UUID=edf9bff8-818a-40ff-86fd-9af28d32382b ro quiet splash vt.handoff=7
Build Date: 07 September 2016  05:11:52AM
xorg-server 2:1.18.4-1ubuntu6 (For technical support please see 
http://www.ubuntu.com/support)
Current version of pixman: 0.33.6
	Before reporting problems, check http://wiki.x.org
	to make sure that you have the latest version.

>8===================================================================8<

Using the VGA port, if I use my external monitor, which has the same
resolution as my laptop (i.e. 1920x1080), all is fine. This monitor is
well detected as shown by the logfile (/var/log/Xorg.0.log):

[  7132.040] (II) modeset(0): EDID vendor "AUO", prod id 4925
[  7132.040] (II) modeset(0): Printing DDC gathered Modelines:
[  7132.040] (II) modeset(0): Modeline "1920x1080"x0.0  141.00  1920 
1936 1952 2104  1080 1083 1097 1116 -hsync -vsync (67.0 kHz eP)

However, if I connect one of the video projectors that I use since
years, nothing happens... Not even a single line in the log file. I've
tried with the same VGA wire... And of course, since the projectors are
not detected, I'm unable to make they work.

I've searched for similar topics on the Web, but nothing... Below are
the output of xrandr for both configurations:

-> With an external monitor
---------------------------

phil at IUTNC-DOSCH log % xrandr 
                                   03-11-2016 11:33:38
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
eDP-1 connected primary 1920x1080+0+0 (normal left inverted right x axis 
y axis) 309mm x 173mm
    1920x1080     60.05*+  59.93
    1680x1050     59.95    59.88
    1600x1024     60.17
    1400x1050     59.98
    1280x1024     60.02
    1440x900      59.89
    1280x960      60.00
    1360x768      59.80    59.96
    1152x864      60.00
    1024x768      60.04    60.00
    960x720       60.00
    928x696       60.05
    896x672       60.01
    960x600       60.00
    960x540       59.99
    800x600       60.00    60.32    56.25
    840x525       60.01    59.88
    800x512       60.17
    700x525       59.98
    640x512       60.02
    720x450       59.89
    640x480       60.00    59.94
    680x384       59.80    59.96
    576x432       60.06
    512x384       60.00
    400x300       60.32    56.34
    320x240       60.05
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 connected (normal left inverted right x axis y axis)
    1920x1080     59.93 +
    1600x1200     60.00
    1680x1050     59.95
    1280x1024     60.02
    1440x900      59.89
    1280x960      60.00
    1280x800      59.81
    1024x768      60.00
    800x600       60.32    56.25
    640x480       59.94
HDMI-2 disconnected (normal left inverted right x axis y axis)

-> With an external video projector
-----------------------------------

phil at IUTNC-DOSCH log % xrandr 
                                   03-11-2016 11:33:41
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
eDP-1 connected primary 1920x1080+0+0 (normal left inverted right x axis 
y axis) 309mm x 173mm
    1920x1080     60.05*+  59.93
    1680x1050     59.95    59.88
    1600x1024     60.17
    1400x1050     59.98
    1280x1024     60.02
    1440x900      59.89
    1280x960      60.00
    1360x768      59.80    59.96
    1152x864      60.00
    1024x768      60.04    60.00
    960x720       60.00
    928x696       60.05
    896x672       60.01
    960x600       60.00
    960x540       59.99
    800x600       60.00    60.32    56.25
    840x525       60.01    59.88
    800x512       60.17
    700x525       59.98
    640x512       60.02
    720x450       59.89
    640x480       60.00    59.94
    680x384       59.80    59.96
    576x432       60.06
    512x384       60.00
    400x300       60.32    56.34
    320x240       60.05
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
HDMI-2 disconnected (normal left inverted right x axis y axis)

I would like to point out that the same video projector is used
without any trouble by my colleagues and that all were fine (monitor +
video projectors) when I was under kubuntu 16.04 with the same laptop.

Do you have an idea of what could make this trouble happens? And do you
have an idea of some tools that I could use to make more
investigations about it?

Thanks for any tips,
-- 
Philippe