Video motion detection

[Johann Hugo]

Hi

I've got a system that receives a http://video-stream and then stores it on 
hard disk (I'm using mencoder for this). This is not very efficient and it 
fills up a lot diskspace with the same image. Are there any apps that will 
allow me to store video only if there is some activity. I had a look at 
motion.sourceforge.net, but it requires a video4linux driver and does not  
compile on FreeBSD.

Johann