Vga monitor screen saver shutdown detect.

I want to setup a pc where the vga monitor shuts off if theres no activity for > 15 mins.
Nothing special about that, however I want to generate a logic change when this happens to signal a microcontroller.
How does a pc typically shutdown its monitor during screensave, does the sync & video just turn off, or does something funky happen like the pc's graphics card talks to the monitor via serial or something.
It wouldnt be too hard to put a simple rc and transistor circuit togther to detect missing vertical sync pulses.

The Sync turns off.
The monitor senses the loss of sync and (may) display "input signal failure" and shuts down.

dr pepper said:

transistor circuit togther to detect missing vertical sync pulses.

Click to expand...

Missing H. sync. (usually there is some delay so the monitor will not go to sleep when the video card changes modes)

Ok then shouldnt be so hard, I'll see if it'll work, might be lazy & use a 555.