[TWETTI]

MP3InfoUtil.getInfo("АДРЕС_АУДИО_ФАЙЛА");
MP3InfoUtil.addEventListener(MP3InfoEvent.COMPLETE, onMP3InfoComplete);
MP3InfoUtil.addEventListener(MP3InfoEvent.ERROR, onMP3InfoError);
...
public function onMP3InfoComplete(event:MP3InfoEvent):void
{
    trace("Длительность = " + event.info["lengthSeconds"]);   
}
 
public function onMP3InfoError(e:MP3InfoEvent):void{
    trace(e.info.message);
}