gstreamer + mplayer

Hi guys~Now i have the difficult problem for me :<
I want to realize the function that capture the picture from webcam and transmit data to another pc.

I know the gstreamer has perform shall----gst-launch for realizing the send side 's function.

i use the command line as following"gst-launch v4lsrc ! ffenc_mpeg4 ! mpeg4videoparse ! rtpmp4vpay ! rtpmp4vdepay ! udpsink host=192.168.1.66 port=1000"

In the receive i use mplayer to realize the receive function
the command line is "mplayer -vc ffodivx udp://192.168.1.66:1000"


when the mplayer cache reach 18.67%,it stop and the fault is as following:

libavformat has been detected and Stream not seekable!


Anybody know how to solve it ~thanks again