Ok, thanks so far. But when I include that line into my xorg.conf i get strange lines on the main lcd of my notebook. i can see my desktop but there are black lines flickering horizontal and vertical. the resolution is also not the right one any more. are there perhaps any possibilities that i have to configure something more in my xorg to get it work nice?

this is what xrandr tells me (the svideo is now detected with atomtvout option true)

Code:
stefan@champery:~$ xrandr
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 1440 x 1440
VGA-0 disconnected (normal left inverted right x axis y axis)
LVDS connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1440x900       59.9 +   59.9  
   1280x854       59.9  
   1360x768       59.8  
   1280x800       59.8  
   1152x864       60.0  
   1280x720       59.9  
   1152x768       59.8  
   1024x768       60.0     59.9* 
   800x600        60.3     59.9  
   640x480        59.9     59.4  
S-video connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1360x768       59.8  
   1024x768       59.9* 
   800x600        60.3     59.9  
   848x480        59.7  
   720x480        59.7  
   640x480        59.9     59.4  
DVI-0 disconnected (normal left inverted right x axis y axis)
and this is my xorg.conf
Code:
Section "Device"
	Identifier	"Configured Video Device"
	Driver		"radeon"
	#Option		"ATOMTvOut"	"true"
EndSection

Section "Monitor"
	Identifier	"Configured Monitor"
EndSection

Section "Screen"
	Identifier	"Default Screen"
	Monitor		"Configured Monitor"
	Device		"Configured Video Device"
EndSection