The program RTMPSRV.exe - which accompanies RTMPDUMP.exe in most Windows distributions - can 'sniff' the connection and find the necessary Command line settings for you.
Some practical advice which might help you -
http://stream-recorder.com/forum/rtm...ws-t10085.html
The main difference in the case of a live stream is the need to
include the switch
--live [or the alternative switch -v] in the command string, not substitute that one switch for the entire command line.