[Openchrome-users] 720x576Noscale does scale 720x576Over doesn't scale

[Paul Gardiner]

I've recently set up a MythTV frontend using Minimyth on a board with  
a CN700 and a VT1622A. I'm using TV out via S-Video to a CRT TV with  
Scart input. I initially set up mode 720x576Noscale, and was pleased  
to find the TV image fitted to the TV screen exactly, but there were a  
few strange things that started to make me think that the image was  
being scaled:

1) The OSD images had to be adjusted to about 650x550, for it to also fit the
TV screen.

2) The TV image showed various artifacts that could be exaplain by  
scaling (jagged diagonal edges, rippling during pans, a general  
softness of focus).

When I first looked at the X screen via VNC I found TV was being  
scaled. The X screen was 720x576, but the decoded TV image was being  
mapped onto a 650x550 subarea, and this area was somehow mapping  
exactly onto the TV screen.

I've just swapped to using the mode 720x576Over. I get a much better  
quality image, and now the TV image extends off the edge of my TV  
screen by the same amount as the OSD. If I look via VNC, I can see the  
TV image mapping directly to the full 720x576 area of the X screen.

Anyone know what's going on here? Also, anyone know how I should  
adjust the mode to fit correctly to the TV. I have no real experience  
of adjusting X. Is there a tool that allows on-the-fly adjustment of  
mode variables?

Cheers,
   Paul.


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