I'm probably missing something very simple here, but I can't find any way of setting the output mode of the TV encoder in the xorg.conf. My setup is as follows:
The board is the Intel D945GCLF2 "Little Falls 2" Mini-ITX motherboard with a 945 chipset and the Chrontel 7021A video encoder conntected to SVDO-B. OS is Ubuntu 8.04.4 LTS with the standard 1.4 X-Server.
I created a Linux install package using the IEGD CED package and (with a little bit of script editing) installed it on the target system - when started up, the TV mode follows the one set in the BIOS - and the only way to override it seems to be using the iegdgui program - but switching between 50 and 60 Hz modes results in corrupt video (can be fixed by restarting GDM using control-alt-backspace) and, more importantly, these format changes do not appear to be recorded in any persistent manner.
Restarting the xserver keeps the previously set video mode (PAL or NTSC) but if you restart the board it reverts to the BIOS default. Right now, I can fix this by changing the mode in the BIOS - but obviously this will not be available if the BIOS is replaced by a bootloader.
I have looked at the "iegd" manpage, and it lists a whole lot of options - but none of them seem to have anything to do with TV output modes.
The key here is to use the CED utility and on the SDVO Port Page, go into the CH7022 (same as a CH7021) attributes and changing the "Display Type attribute (ID 9) to Composite or S-Video which are both TV modes. When you do that, you will have a sample xorg.conf section for the IEGD parameters that contains something like this:
Option "ALL/1/Port/2/Attr/9" "4"
(this example sets it to composite by using option 4, if you set it to 8 then it will be S-Video)
Hope this helps.