1) Installer « gstreamer-tools »

$ gst-launch v4l2src device=/dev/video0 ! \
'video/x-raw-yuv,width=640,height=480,framerate=30/1' ! \
xvimagesink

gst-launch v4l2src ! 'video/x-raw-yuv,width=640,height=480,framerate=30/1' ! \
queue ! videorate ! 'video/x-raw-yuv,framerate=30/1' ! theoraenc ! \
queue ! oggmux ! filesink location=me_funny_dancing.ogg

Tutorial complet