Capture screen with mencoder

[Rodolfo Medina <rodolfo.medina@gmail.com>]

I posted this to Mplayer mailing list but got no answer so am sharing it here
hoping someone can help...

I capture my webcam stream with:

 $ mencoder tv:// -tv driver=v4l2:width=640:height=480:device=/dev/video0:forceaudio:alsa:adevice=hw.1,0 -ovc lavc -oac mp3lame -lameopts cbr:br=64:mode=3 -o webcam.avi

and it works fine.  How can I modify the above command so to capture desktop
screen instead (with audio)?  I suppose it's a matter of replacing /dev/video0
with something else but don't know what nor the correct syntax...

Thanks for any help,

Rodolfo