[ubuntu-uk] using laptop (11.10) thru tv (VGA)

[Jim Price]

On 29/07/12 19:18, pete smout wrote:
> Hi all,
>
> I'm using ubuntu 11.10 (12.04 won't install on it!) when I plug it into
> my tv via VGA out on laptop to the VGA input on my tv the resolution is
> all wrong and no matter what I try I can't put it right!
>
> with the laptop screen turned off (fn F6 on my laptop) the desktop
> appears on the tv, with a 2 inch (ish) gap down the left hand side of
> the screen and the bottom of the desktop missing off the screen. I open
> the system settings / displays to change resolution and the correct
> resolution is not listed.
>
> On Lucid I had to boot the laptop whilst plugged into the TV the first
> time to get it to 'register' the tv's settings so I tried the same on
> 11.10 with no joy!
>
> I have copied the xorg.conf file from lucid into 11.10 (there was not
> one there already) this has made no difference has xorg been replaced?

It shouldn't need to be there on most installations nowadays. I would 
try getting it to work without one first.

> the only resolution that shows the whole desktop on the tv is 800*600
> not ideal on a HD tv (wide screen) this is not wide screen, old 4.3 format
>
> Any one got any ideas?

What's the make and model of the TV - you should be able to find out 
what its native resolution is from that info. If it really does have a 
native resolution of 800x600 it must be fairly old. Most newer TVs have 
native resolutions greater than that, a minimum of 1280x720 if they are 
advertised as "HD Ready", but often 1366x768 or 1920x1080.

Are you trying to mirror the laptop screen on the TV, or have a second 
monitory on the TV as an extension of your desktop? Trying to mirror a 
4x3 laptop screen on a wide screen TV is going to be a choice between 
dark areas at the sides or a screwed up aspect ratio. Your TV should 
have settings to correct the size of the displayed image, but some are 
better than others.

Typing:

xrandr

in a terminal while the TV is connected should report the min, max and 
other available resolutions for both screens, and also the names that 
the screens use so you can set the resolutions independently. You can do 
this from the monitor settings dialog for settings it recognises, but if 
it should work with an unrecognised setting, you should be able to set 
it with xrandr. My TV has a non-standard resolution of 1280x960, but 
does support a 1280x720 mode if you set it. I use a script using 
information from the output of the following command:

gtf 1280 720 75

This is for a monitor which supports 1280x720 at 75 Hz. You need to put 
numbers appropriate for your TV in there. 60Hz is usually what the 
native display runs at on an LCD TV (despite the TV signal in this 
country being 50Hz), so you might be better off using:

gtf 1280 720 60

This gives a modeline, which gets used in the following script:

#!/bin/bash

# This line adds the mode using the modeline output from gtf
# Note that it is all one line, so remove any wrap
xrandr --newmode  "1280x720_75.00"  95.65  1280 1352 1488 1696  720 721 
724 752  -HSync +Vsync

# This line adds the mode, as it is not available by default.
# Note that HDMI-0 is the name of the monitor from the xrandr command
xrandr --addmode HDMI-0 1280x720_75.00

# This line sets the resolution on HDMI-0
xrandr --output HDMI-0 --mode 1280x720_75.00

#This is the end of the script.

You would need to create your own script by customising the modeline and 
monitor name, and run it when you need to use the TV as a monitor. Don't 
just copy my settings - that might be bad for your monitor.

There may be an easier way, but this approach works for me on most 
modern Linux distros.

-- 
JimP