Switching default display to S-Video in BeagelBoard XM

I'm working on a project using BeagelBoard XM. I ported "Androi Froyo"
on the board but I'm having troubles in switchin the default display
to S-Video.

I edited the boot.scr files with "omapdss.def_disp=tv" ,
"omapfb.mode=tv:ntsc" but the default display is still "dvi"

I'm using Android Froyo from this link
Kernel Version : 2.6.32

Is there any other solution to my problem ?