All the above is true for flash clients only. Ffmpeg-family tools treat such streams in a completely different way. They wait for both (audio and video) streams to appear in RTMP stream until probesize bytes pass through. That setting can (and should) be reduced in real life.
Moreover since 0.9.7 version of nginx-rtmp-module new default values are set for several options:
- wait_key is now ON by default. That's the most reasonable setting for most cases.
- play_restart is now OFF by default. Several flash players stop streaming on NetStream.Play.Stop and do not resume it later on NetStream.Play.Start which is not what expected.