Note these instructions are for Ubuntu 9.10 (Karmic).
In prior versions of Ubuntu, I have had some problems getting the VGA and S-Video outputs on my Inspiron 1720 working, so today I tackled this problem. In Karmic, this process is quite straightforward. Once you connect your video cable to the laptop, whether it is S-Video to a television or VGA to a monitor, you can cycle through various video distribution modes using the Fn-F8 keys. This is marked as “CRT/LCD” on the F8 key. Here is the cycle that I found using S-Video output.
1. LCD on at full resolution ; TV off
2. LCD off ; TV on at 848×480
3. LCD on at full resolution ; TV on and to right of LCD, 848×480 ; desktop shared across both screens
4. LCD on, 1024×768 ; TV on, 1024×768 ; mirrored desktop
You can change the parameters of each of these cycles by running the Display Preferences applet (System->Preferences->Display). This applet has a spacial depiction ofÂ both displays and you may drag a display to be in a specific location with respect to the other display. For example, if in 3 above, you wanted the TV to appear logically above the CRT, you would drag the TV rectangle (labeled “unknown” for me) above the rectangle labeled “Laptop 17”.
Mode 3 shares the desktop over the 2 screens so that you can move the mouse cursor from one screen to the other screen, effectively extending your desktop. If you use an image as your desktop background, you may get the background color showing around the edges of the image as the image is centered in the extended display resolution.
Mode 4 shows the same content on the laptop LCD panel as on the connected screen. Note that in this mode for a connected television, the video quality is less crisp than in mode 3 due to the scaling of the 1024×768 resolution to something the television can handle.
If you connect a VGA cable to a monitor, a similar cycle is used, but the VGA resolutions used will be different.
Out of curiosity, I connected both a VGA monitor and S-Video to the TV, but preference seems to be given to the VGA monitor such that the TV never gets a signal.