FLV modification before play

gistfile1.as

//this code is able to load a FLV file, change stuff in his byteArray, and play the resulting FLV
//this could be helpfull to secure a web player for example, by obfuscating the flv sent by the server

import flash.net.NetConnection;
import flash.net.NetStream;
import flash.net.URLRequest;
import flash.utils.ByteArray;


public var ns:NetStream;
public var nc:NetConnection;
public var originalBytes:ByteArray;
public var modifiedBytes:ByteArray;

private function flvLoadBytes():void{ //chargement du FLV en binaire et modification
    flash.media.SoundMixer.stopAll();
    //chargement...
    
    var ur:URLRequest = new URLRequest('ex1.dub.flv');
    var ul:URLLoader = new URLLoader();
    ul.dataFormat = URLLoaderDataFormat.BINARY;
    ul.addEventListener(Event.COMPLETE, function(ev:Event):void
    {
        //fichier chargé.
        originalBytes = ul.data;
        modifiedBytes = new ByteArray();
        //copy header (header=13octets, scripttag=159octets)
        originalBytes.readBytes(modifiedBytes,modifiedBytes.length,13+159);
        
        var i:int=0;
        var n:Number;
        var tmpBytes:ByteArray;
        //modification du flv.
        while( originalBytes.bytesAvailable >= 531){
            //on lit les 531 octets
            tmpBytes=new ByteArray;
            originalBytes.readBytes(tmpBytes,0,531);
            if (i%2==0){
                //on ne garde qu'un paquet de 531 sur deux
                //s'ils sont ceux qu'il nous faut
                //on les ecrits dans modifiedBytes (à la fin)
                tmpBytes.readBytes(modifiedBytes,modifiedBytes.length,531);
            }
            i++;
        }
        
        //trace('taille = from '+originalBytes.length+' to '+modifiedBytes.length);
        
        originalBytes.position=0;
        flvPlayBytes(modifiedBytes);
        
    });
    ul.load(ur);

}
private function flvPlayBytes(bytes:ByteArray):void{ //joue le tableau de bytes d'un flv valide
    nc = new NetConnection();
    //chargement du flv modifié en mémoire.
    nc.addEventListener(NetStatusEvent.NET_STATUS, function(event:NetStatusEvent):void{
        switch(event.info.code)
        {
            case 'NetConnection.Connect.Success':
                ns = new NetStream(nc);
                ns.client = {};
                ns.play(null);
                ns.appendBytes(bytes);//attention, appendBytes après play
                break;
        }
    });
    nc.connect(null);
}