how can i use avcpp to push h264 rtmp stream to web server?

i test api2-decode-encode-video example,  i use this command :
./api2-decode-encode-video rtmp://xx.xx.xx.xx:1935/livetv/stream rtmp://127.0.0.1/live/stream
then i got error:
terminate called after throwing an instance of 'av::Exception'
  what():  Codec context invalid media type

question:  how can i realize the function to PUSH RTMP Stream to some rtmp server?  please help !