KDE and Underscan

[Guest]

I recently switched from Windows to KDE. I've got my laptop hooked up to a TV through HDMI, but the edges of the desktop extended past the edge of the screen, and I couldn't see them. (I had the same problem with Windows.)

So I used NVidia X Server Settings to add an underscan of 36 pixels. it worked, but two weird things happened:

1) The DPI went crazy - everything was many times too big. I had to force it to 96 DPI to get a reasonable GUI.

2) I can scroll past the right and bottom edges of the desktop. If I move the mouse to the right or bottom of the screen, it scrolls down into 36? 72? pixels of blackness. I can no longer see the top left corner of the desktop, but can scroll back by moving the mouse to the top left corner. Very annoying!

Does anyone know how to disable the "underscan scrolling" in KDE? There's never anything of use to see, just black space.



[EDIT] The following is from /var/log/Xorg.0.log if that's any help:
[ 7.827] (II) NVIDIA(0): Validated MetaModes:
[ 7.827] (II) NVIDIA(0):
[ 7.827] (II) NVIDIA(0): "HDMI-0:nvidia-auto-select+0+0{viewportout=1848x1039+36+20}"
[ 7.827] (II) NVIDIA(0): Virtual screen size determined to be 1848 x 1039
[ 8.883] (--) NVIDIA(0): DPI set to (293, 293); computed from "UseEdidDpi" X config
[ 8.883] (--) NVIDIA(0): option
[ 8.883] (--) Depth 24 pixmap format is 32 bpp
[ 8.887] (II) NVIDIA: Using 768.00 MB of virtual memory for indirect memory access.
[ 8.896] (II) NVIDIA(0): Setting mode "HDMI-0:nvidia-auto-select+0+0{viewportout=1848x1039+36+20}"

[oshunluvr]

The problem - since you had the same issue with Windows as you are having now - is not really with your desktop settings - it's the TV. Many TV's (especially older or cheap models) incorrectly report EDID information and xorg needs that to correctly determine optimal settings. I suspect most of the issues you're having are caused by the "underscan" you set up.

You have two options: create an xorg config file that correctly defines your TV/Monitor or create xrandr commands that correctly set everything for you at boot time. For either option, you need the correct settings (resolution and scan freqs.) for the TV.

I suggest clearing out the edits you made, search the internet for the proper settings for your TV, test the settings with xrandr until you get it right, then decide how you want to save the settings.

I always used /etc/X11/xorg.conf in the old days, but anymore it get deleted with every driver upgrade. Now-a-days I think the "correct" way to add manual settings is in a file in /etc/X11/Xsession.d/

[Guest]

OK, I've reset the underscan to zero. When I type "xrandr" I get:

Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 8192 x 8192
VGA-0 disconnected (normal left inverted right x axis y axis)
LVDS-0 connected (normal left inverted right x axis y axis)
   1600x900      60.08 +
HDMI-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 160mm x 90mm
   1920x1080     60.00*+  60.00    59.99    59.94    29.97    23.97    60.05    60.00  
   1280x1024     60.02  
   1280x720      60.00    59.94  
   1024x768      60.00  
   800x600       60.32  
   720x480       59.94  
   640x480       59.95    59.94

I've looked up my TV's specs. It's got model number 42LK450-UB, and I found the following:

HDMI Input, Resolution = 1920*1080:
    H-freq(kHz) 67.5
    V-freq(kHz) 60
    Pixel clock 148.5

If I understand things correctly, I need to send this to gtf, which will generate the xrandr command to use. Am I on the right track? The man page for gtf just says it takes a "refresh rate". Does it want the horizontal or vertical frequency, or something altogether different?

[oshunluvr]

According to the above, you laptop internal monitor is on at 1600x900 @60 and your external via hdmi (I assume the TV) is on at 1920x1080 @60 - all of which sounds normal. What are you seeing on the displays? Are you using extended desktop or trying to mirror?

[claydoh]

Have you looked at the picture settings on the TV itself?

I just got a new 1080p TV, and had the same issue with the desktop extending beyond the edges. I had to go into the Picture settings and change the "pixel shape" setting to "100% full"

Yours may have something similar that you can adjust. I didn't have to muck about with xorg at all.

Sent from my HTC6435LVW using Tapatalk

[Frank616]

I have a similar issue, but am using the display port output and an adapter that goes between display port and HDMI. I also have but one display connected, not two.

We have a 1080p 30" flatscreen TV in our travel trailer. It has HDMI inputs. Today I bought an old compact case Lenovo PC to use as a media center. It has a 3 GHz Core-2 Duo with integrated Intel graphics, and a display port output. I installed Kubuntu 14.04 on a 60 GB SSD, plugged a display port to HDMI adapter into the display port of the computer, and an HDMI cable to the other end of the adapter, and then into the TV, and booted. Worked the first time!!

My only issue now is the image size. It is slightly bigger in all directions than the TV screen. Most of the bottom 'ribbon' menu is below the bottom edge of the screen.

There are few adjustments in the 'monitor' section of the Kubuntu control panel, only allowing me to choose different resolutions. None of them solve the problem. 1920 x 1080 should work, and that is what it is set at.

I have tried changing settings on the TV as well, making sure that it is not set to an 'expanded' or 'wide view' mode. That may have helped with width, but not with height. The image coming from the computer is still larger than the screen of the TV.

I'll start looking for the specs for my TV now, and hopefully I can 'piggy back' off this thread to solve my issue as well.

Thanks.

Frank.

[Frank616]

OK, part of the problem is that this is NOT a 1080 unit. The owner's manual says max resolution is 1366 x 768.

Changing to the closest resolution available on the PC (1360 x 768) helps, but the picture is still too large for the screen.

Not being a patient person by nature, and not finding any technical information on this TV on the web, I did the 'quick and dirty' and used the VGA connection. Now all the screen height, width etc. controls all work, and the picture is the right size. Not 'quite' as sharp, but good enough for the trailer.

Job done.

Frank.