GST Movie Texture - How to mute video??

Hey, I've been using GST Movie Texture for a lil' bit now and in general have an okay understanding of it and how to extend the functionality. I am having wicked trouble getting it to mute however.

The documentation says that setting the audio_index to -1 should mute all the audio from the video which doesn't seem to be the case for me. I've also tried setting the volume of the gst texture to 0.0F and setting the audio listener for the scene to 0 as well as pausing the audio listener. All to no avail.

Any thoughts or suggestions would be welcome.