var connection_nc:NetConnection = new NetConnection();
connection_nc.connect(null);   
var stream_ns:NetStream = new NetStream(connection_nc);   
function mcLoad(link:String):Void {      
   loader.vC.my_video.attachVideo(stream_ns);   
   stream_ns.play(link);
   stream_ns.pause(true);      
   var loaded_interval:Number = setInterval(checkBytesLoaded, 500, stream_ns);      
}

function checkBytesLoaded(my_ns:NetStream) {
   var pctLoaded:Number = Math.round(my_ns.bytesLoaded / my_ns.bytesTotal * 100);
   if (pctLoaded >= 100) {
   clearInterval(loaded_interval);
   stream_ns.pause(false);
   }
}   

   stream.onMetaData = function(infoObject:Object) {
     for (var propName:String in infoObject) {
       if (propName == "duration") {               
         nsDuration = infoObject[propName]; // и есть наша продолжительность;
       }
     }
    }