Instal the gstreamer main components:
:~$ apt-get install gstreamer0.10-plugins-base gstreamer0.10-plugins-good gstreamer0.10-plugins-ugly gstreamer0.10-tools gstreamer0.10-alsa
Create the Script, and set it to the ip of the VLC UDP multicast server.
:~$ vim /etc/init.d/gst.sh
#!/bin/sh killall gst-launch-0.10 gst-launch-0.10 udpsrc port=1234 multicast-group=239.255.12.42 ! decodebin ! audioconvert ! alsasink
To run it on boot, simply do:
:~$ update-rc.d gst.sh defaults
