The FFmpeg documentation suggests this syntax:
rtmp://[username:password@]server[:port][/app][/instance][/playpath]
However, this will give you an “Problem accessing the DNS.” error when trying to connect to the Wowza server.
In this thread it is suggested to use Wowza SecureURLParams instead of RTMP authentication, when streaming from FFmpeg.
Is it still not possible to use FFmpeg with RTMP authentication?