NetStream Publish live mp3 or aac codecs like Adobe Media Live Encoder

I need to use NetStream.publish in my ActionScript 3 app to send a live stream with H.264 video and mp3 or aac audio to a rtmp server. Is this possible now in the latest version of the Flash Player or AIR? If not, are there any plans to make it possible in the future? This functionality is available in the Adobe Media Live Encoder, so I would like to know what is happening in that application that I can reproduce in mine to support at minimum the mp3 codec in live streams. If I am not able to do this with ActionScript 3, what are my other options to accomplish this externally? Can I intercept the rtmp stream, modify the audio bits, and send it out the same (or different) port, or a similar method?