I wanted to test the dga video output with mplayer, and issued the following command from a console window in kde:

mplayer -vo dga somefile.avi

It was a fault, because I lost control over my computer for almost two hours:

- mplayer was irresponsive to any keystrokes, so <ENTER>, <ESC>, <CTRL>C did not stop playback
- my whole system was irresponsive to any keystrokes: <CRTL><ALT><BACKSPACE>, <CRTL><ALT><DEL>, <CRTL><ALT><F2>, so mplayer continued playback

No matter what I did, mplayer continued playback.

I did not want to wait until the movie ends, so I pushed the power switch to switch off my machine.
It had some effect: mplayer paused playing as long as the power switch was pushed in, but it continued playback as soon as I released it. And the system did not shut down as expected.

I thought maybe mplayer stole the screen, but I could blindly login in an other terminal and kill mplayer, but it did not seemed to work either.

So, once I started mplayer playback with the dga output, I had exactly no way to stop it playing or to restart the machine, I had to wait until the movie ends and mplayer exits.

I wonder why this happened?