Here are two command lines to play 2 different video files in sync with VLC.
network clock client :
vlc --network-synchronisation --netsync-master-ip 127.0.0.1 sync-test-rouge.mp4
network clock master :
vlc --network-synchronisation --netsync-master sync-test.mp4
It seems to work only with videos of the same length.
Both audio and video are synchronized. The jitter compensation algorithm take a few time to compensate and after a dozen of seconds all videos are in sync.
It was tested on Ubuntu 13.10 with VLC 2.0.8, the two players on the same machine but it should work over the network.
Also the client must be started before master.