Here's how one guy broadcast a live stream:

$ ffmpeg -y -loglevel warning -f dshow -i video="screen-capture-recorder" -vf crop=690:388:136:0 -r 30 -s 962x388 -threads 2 -vcodec libx264 -vpre baseline -vpre my_ffpreset -f flv rtmp:///live/myStream.sdp

Here is my ffmpeg preset (libx264-my_ffpreset.ffpreset):
coder=1
flags2=+wpred+dct8x8
level=31
maxrate=1200000
bufsize=200000
wpredp=0
g=60
refs=1
subq=3
trellis=0
bf=0
rc_lookahead=0