I decided to use a low end computer as my media center. I wanted use the HDMI connection, because doing so I don't need an extra cable for audio. The bad thing was that the output screen on the TV was clipped when using HDMI. It was just fine using VGA port, but clipped on HDMI.
I found the reason of the clipping is something called overscan (more info about it here: https://en.wikipedia.org/wiki/Overscan). After a long search on the web I found you can try disable overscan on your TV menu (mine doen't have this option), try underscan on you video board (didn't have this option either!). Another option was xrandr --tranform, but the result was not good.
The best option that I found was to create a new modeline. And this worked just fine after figuring out the right configuration.
You can fin your TV's modeline here:
https://www.mythtv.org/wiki/Modeline_Database
My TV is an old and good Panasonic TH-42PV70LB. It has a nice plasma screen and besides using it as a TV I use it as a heater to keep my room warm during the winter. The mode I picked from the site was:
TX-42PX75: Modeline "1208x679" 74.25 1208 1353 1393 1650 679 707 712 750 +hsync +vsync
I have no idea what all this numbers means, but you can find more info about it here (if you are brave enough):
https://en.wikipedia.org/wiki/XFree86_Modeline
What it actually does is configure your HDMI output to add the expected overscan/underscan that the old stuff are waiting for. So first you create the new mode:
xrandr --newmode "1208x679" 74.25 1208 1353 1393 1650 679 707 712 750 +hsync +vsync
Add it to the HDMI interface:
xrandr --addmode HDMI1 "1208x679"
And turn it on:
xrandr --output HDMI1 --mode "1208x679"
This is way to deal with the overscan problem on old TVs. Probably all the new TV has some feature to turn it off when using computer.
Remember to change HDMI1 to what is the name of your interface.
Unfortunately you will lose this after restart the system. This is something for another post.
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