First test your command with
RTMPdump. if it starts downloading successfully then you can redirect the output to vlc.
correct command line:
Code:
rtmpdump -r "rtmp://npsaflivefs.fplive.net:1935/npsaflive-live/" -a "npsaflive-live/" -f "WIN 10,3,181,14" -W "http://media-player.cdn.level3.net/flash/v1_1_1/Level3MediaPlayer.swf" -p "http://www.windowsintowonderland.org/live/live3.htm" --live -y "stream50" | "C:\Program Files\VideoLAN\VLC\vlc.exe" -