I was trying to get the TVout library working and I found that the given circuit diagram appears to have the resistors reversed.
You can use an 8ohm speaker to check the signals coming out of pins 7 and 9. Pin 7 has a variable signal while pin 9 has a steady tone which indicates it's the sync signal.
Having the resistors set up the way the TVout page says resulted in no image.
The other thing I found is that that 75ohm resistor between video and ground isn't really optional. Even when the video in on your device shows a 75+ ohm resistance, the image is still fuzzy.
I was wondering if anyone else found these same issues or if the resistors depend on the monitor.
I confirmed flipping the resistors and adding the 75ohm to ground works on a genuine UNO and the cheap Chinese Duemilanove / Diecimila nanos with a low cost LCD monitor