FLVPlayback - Streaming MP3 from RTMP - No MetadataEvent?

Any reason why the FLVPlayback wont fire a MetadataEvent.METADATA_RECEIVED event when trying to load an MP3 from a Flash Media Server?

I have some complex functionality requiring the use of the FLVPlayback component to play MP3s, but why oh why will mp3 files not fire MetadataEvents. Why can i not get the full length of the file.

I do not want to use the Sound class.

Any ideas?