[mythtv-users] TV out size

Tim Phipps mythtv-users at phipps-hutton.freeserve.co.uk
Thu Feb 21 12:11:21 UTC 2008

Michael Skaastrup wrote:
> Using Xorg via drivers and 720x576pal mode i get good picture but the 
> image is surrounded by black bars.

That mode will turn on the TV chips scaler and de-interlacer. You get 
black bars because the scaler shrinks the screen output so you can see 
it all an a variety of CRT TVs (they all overscan by different amounts).
> I also tried 720x576Noscale. This IMO produces the best image quality 
> but not all on-screen.
That mode turns off the scaler and de-interlacer (as long as you don't 
have a display attached to the VGA port). What do you mean by "not all 
on-screen"? Your CRT TV will overscan by some amount so you may not see 
all the MythTV GUI.

You can run the GUI in a different mode to the TV-playback. I get the 
best results having the GUI in 800x600 and TV playback in 
720x576Noscale. The GUI mode is the default for themes so the frontend 
doesn't have to spend time scaling and caching the theme files. It also 
turns on the scaler which means I see the whole GUI and horizontal 
lines don't boggle up and down.

You need 'Modes "800x600" "720x576Noscale"' in the Display subsection of 
xorg.conf so it starts in 800x600. Turning on the mode switching is done 
in /Setup/Setup/Appearance/Page3.

> For my test I am using a Nokia 32" 100Hz CRT television but have also 
> tried various other televisions with same results.

That's going to have a de-interlacer running even in 720x576Noscale so 
you might have to live with a bit of smearing with interlaced action. 
Films might be OK.


More information about the mythtv-users mailing list