How to implement an audio-filter for the GStreamer playbin - element?

[Claus Dietrich <claus.dietrich@xxxxxxxxxx>]

Hi
I am trying to build a special AudioPlayer-class for someone in the 
German Club, who wants to play audio files with a normalized volume.
I drafted the following GStreamer pipeline, which should do the job:

$ gst-launch-1.0 playbin volume=0.5 audio-filter="audioamplify 
amplification=1" uri="file:///home/claus/song.mp3"

Unfortunately I failed to mimic this pipeline with gb.media.

This part works

  pl = New MediaPipeline As "PipeEvents"
  src = New MediaControl(pl, "playbin")
  src["volume"] = 0.5
  src["uri"] = "file:///home/claus/song.mp3"
  pl.play()

but I don't know how to implement the audio-filter with Gambas. Do I 
have to use the MediaFilter-class? If so, how do I have to set it up and 
how can I use it as for the playbin-property audio-filter? All attempts 
failed so far.

Can someone help?

Best regards, Claus