Video play error in Actionscript3 - actionscript-3

Question

i am working on an actionscript3 project. when i am loading the video file in a class without the e:Event parameter;
private function setupVideo_2():void
{
vid = new Video(640,480);
addChild(vid);
nc= new NetConnection();
nc.connect(null);
ns= new NetStream(nc);
vid.attachNetStream(ns);
var listener:Object = new Object();
listener.onMetaData= function (evt:Object):void{};
ns.client = listener;
ns.play("introduction to 3G and 4G.flv");
}
it plays fine.
The moment i put it in the condition stating play only when the marker pattern is sited; it loadz but there is a visible lag followed by stopping of the video and repeating of the first line around 3 times and then the air application stops working and eventually crashes.
here is the code for it.
private function loop (e:Event):void
{
bmd.draw(vid);
try
{
if (detector.detectMarkerLite(raster, 80)&& detector.getConfidence() > 0.5)
{
vid = new Video(640,480);
addChild(vid);
nc= new NetConnection();
nc.connect(null);
ns= new NetStream(nc);
vid.attachNetStream(ns);
var listener:Object = new Object();
listener.onMetaData= function (evt:Object):void{};
ns.client = listener;
ns.play("4 Clever Ethernet Cable Hacks.flv");
}
}
catch(e:Error){}
}
Please tell me why is the video lagging when played inside the if condition.