Как получить длину mp3, который загружаю через FMS?

Код:
var nc:NetConnection = new NetConnection();
var ns:NetStream;
var mp3Sound:Sound;
nc.onStatus = function(info){
trace(info.code);
if (info.code.indexOf("Success") != -1){
enableButton();
}
}
function enableButton(){
myButton.enabled = true;
myButton._alpha = 100;
}
ns.onMetaData = function(infoObject:Object) {
for (var propName:String in infoObject) {
trace(propName + " = " + infoObject[propName]);
}
};
function startTheStream(){
ns = new NetStream(nc);
var mc:MovieClip = _root.createEmptyMovieClip("soundAttacher", 1);
mp3Sound = new Sound(mc);
mc.attachAudio(ns);
mp3Sound.setVolume(vol);
ns.play("mp3:1");
}
myButton.onRelease = function(){
startTheStream();
}
myButton.enabled = false;
myButton._alpha = 50;
nc.connect("rtmp://192.168.1.2/songnation/mp3");