Using mp4mux with faststart option produces empty file

[stic at free.fr]

Hi,
I am trying to use mp4mux with faststart option. But I've never been able to use this option.
It gives me an empty output file when faststart=true.

Here is an example of my pipeline: 
appsrc is-live=true do-timestamp=true ! video/x-h264,framerate=30/1,width=1280,height=800 ! queue ! h264parse ! mp4mux faststart-file=/data/local/tmp/faststart_file fragment-duration=200 faststart=true ! filesink location=/data/local/tmp/test.mp4

I tried to specify the faststart-file and I have seen that the size of the faststart file always increases with the time... and the size of the target output file is still 0.
I also tried to specify fragment-duration but it doesn't change anything.
This is on gstreamer 1.4.5 Android release (but same on earlier releases too), would it be possible that there might be something wrong with mp4mux running on Android ?

Does someone have any idea why this doesn't work ?
Thanks.