[Openchrome-users] letterbox on monitor while 720p on tv

[John Robinson]

On 09/12/2009 23:51, vpcompany at tiscali.it wrote:
> hello devs,
> I ask you a trick to make it possible to letterbox 1280x720 @ 1280x1024 on 4:3 monitors while using a 720p tvout.
> 
> if I use 720p I get a nice view on the tv but on the monitor is vertically stretched because native res is 1280x1024 SXGA on digital (dvi) lcd
> 
> I think theoretically speaking it must be something like 152 black lines then the display and finally other 152 black lines to be sent only to the monitor.
> 
> does it make sense to you?

I'm not a dev but it makes sense to me. I'm not sure but you may be able 
to do this by adding a custom Modeline; start with a standard 1280x1024 
modeline at the vertical refresh rate you want, then tweak the line 
numbers to subtract 304 lines from vdisp (making it 720), and 152 lines 
from vsyncstart and vsyncend, and leave vtotal alone. For example, if 
you started with:
Modeline "1280x1024"   108   1280 1328 1440 1688   1024 1025 1028 1066 
+hsync +vsync

(the above is a VESA 60Hz mode) you'd end up with:
Modeline "1280x720_1024"   108   1280 1328 1440 1688   720 873 876 1066 
  +hsync +vsync

Please be sure this is what you want to do, and don't blame me if this 
blows up your monitor, startles your cat, etc...

Cheers,

John.