How to understand live stream is online

Question

Hi,
First sorry about my english, i search my problem, but i couldnt find my answer,
We have more then 80 live stream videos. More than 20 PC with capture cards, send cam streams to FSM with FME,
Problems,
PC can crush, capture card can crush, fme can crush, camera connection can crush,
so with below code, i can unterstand if FMS server is alive, "NetConnection.Connect.Success"
but is my stream  alive? How i can understand "1test1" is alive,
for example i can unterstand with onMetaData info, if there is no meta info, no stream,
but i am a noob, what is the true way to understand live stream is alive, meta info isn't true way i think
i change var videoURL:String ="1test1" to a false value
but no error i get, it never says "NetStream.Play.StreamNotFound":
my goal is, i will make a web page, it will find all livestreams from xml, and cheack them, so systemadmin will see problem easly,
last question, if there is a camera problem, livestream gives a blank black screen, can i understand automaticly  this screen
var videoURL:String ="1test1"
var nc:NetConnection = new NetConnection();
nc.client = this;
nc.connect("rtmp://myFMS/live/");
nc.addEventListener(NetStatusEvent.NET_STATUS, netStatusHandler);
function netStatusHandler(event:NetStatusEvent):void{
trace(" trace netStatusHandler: " +event.info.code);  
switch (event.info.code)
case "NetConnection.Connect.Success":
connectStream();
break;
case "NetStream.Play.StreamNotFound":
trace("Stream not found: " + videoURL);
break;
function connectStream():void
var vid:Video = new Video(640,480);
var ns:NetStream = new NetStream(nc);
ns.addEventListener(NetStatusEvent.NET_STATUS, netStatusHandler);
var meta:Object = new Object();
meta.onMetaData = function(info:Object){
trace("metadata: duration=" + info.duration + " width=" + info.width + " height=" + info.height + " framerate=" + info.framerate)}        
ns.client = meta;
addChild(vid);     
vid.attachNetStream(ns);
ns.play(videoURL);

Answer 1

thanks, now i am able to understand what's your requirement.
first you create a sample live chat application. just for testing purpose. 
1- create video object.; 
2- create camera object; 
3- attache camera object to video object; 
4- create a button and register a event and listener function write below code. 
5- download adobe.image.PNGEncoder class 
hope, you can capture photo from video object into you testing application 
package
    import com.adobe.image.PNGEncoder;
    import flash.display.Sprite;
    import flash.display.DisplayObject;
    import flash.events.*;
    import flash.display.Bitmap;
    import flash.display.BitmapData;
    import flash.media.Video;
    import flash.media.Camera;
    import flash.geom.*;
    import flash.net.FileReference;
    import flash.utils.ByteArray;
    public class SavePng extends Sprite
        private var cam:Camera;
        private var video:Video;
        private var ab:FileReference;
        public function SavePng()
            cam = Camera.getCamera();
            cam.setMode(800,600,25);
            cam.setQuality(0, 90);
            video = new Video(1024,768);
            video .smoothing=true;
            video.attachCamera(cam);
            addChild(video);
            btn.addEventListener(MouseEvent.CLICK,saveImage);
            ab=new FileReference();
        private function saveImage(evt:MouseEvent):void
            var count:int = 0;
            var scaleW:Number = .5;
            var scaleH:Number = .5;
            var m:Matrix = new Matrix();
            m.scale(scaleW,scaleH);
            var bmd:BitmapData = new BitmapData(320,240,true);
            bmd.draw(video);
            var img:Bitmap=new Bitmap(bmd);
            img.x=250;
            img.y=200;
            addChild(img);
            var ba:ByteArray = PNGEncoder.encode(bmd);
           ab.save(ba,"sushil.png")