RTMPsink bandwidth consumption - advice sought

[Tim Wood]

Hi

We are in the process of setting up a mixing application that outputs to multiple sinks.  One of the targets is rtmp.   Our process so far is to implement a pipeline using gst-launch that works for the given sink, then implement it into the app.  
For RTMP we have found an issue that we are unable to resolve , so I'm wondering if someone on the list might have some information / suggestions on how to deal with this.

Using the following basic command line:

gst-launch-1.0 videotestsrc !  videorate ! video/x-raw,framerate=25/1   ! queue ! x264enc name=e256k bitrate=256 key-int-max=25 bframes=0  ! \
    flvmux name=muxer ! rtmpsink location='*****'  \
    audiotestsrc ! queue ! audioconvert ! muxer.

The issue we have is that we are expecting to see upstreaming at something like < 300Kbps .  The actual upstream usage measured from the network interface is ~1870 Kbps. For what its worth, the stream itself, once it gets to our CDN's FMS , is viewable on ffplay, and only consumes the expected ~ 300 or so .  

 I've looked around on google for potential switches / issues that might resolve this, but it seems pretty much everyone else using rtmp sink is not having this problem.

Some misc info:
gst-launch-1.0 version 1.4.1
librtmp version 2.3
GStreamer 1.4.1
kernel -3.10.17c1
arch- x86_64 AMD FX(tm)-4300 Quad-Core

Any advice on this would be greatly appreciated, for us its a show stopper at the moment

Cheers
Tim