In my Fedora 12, when I run this for just a test, it shows a window but then it shows nothing like its frozen. And, it keeps my terminal image instead of video source.
$ gst-launch-0.10 v4l2src ! xvimagesink
or
$ gst-launch-0.10 autovideosrc ! autovideosink
How to do a test loopback, not having my screen shot inside the popup window?