install gst-opencv
download a profile file, for example
from http://code.google.com/p/jviolajones...ce_default.xml
execute gst-launch with the facedetect module:
gst-launch-0.10 v4l2camsrc device=/dev/video1 ! video/x-raw-yuv,width=320,height=240 ! ffmpegcolorspace ! videobalance brightness=0.3 contrast=2.0 ! gamma gamma=1.5 ! ffmpegcolorspace ! facedetect profile="/home/user/haarcascade_frontalface_default.xml" ! ffmpegcolorspace ! ximagesink