Flash从网址播放mp4

Question

        _video = new Video(); 
        _connection_nc = new NetConnection(); 
        _connection_nc.connect(null); 
        _stream_ns = new NetStream(_connection_nc); 
        _client = new Object(); 
        _stream_ns.client = _client; 
        _stream_ns.addEventListener(NetStatusEvent.NET_STATUS, onStatus); 

        _video.attachNetStream(_stream_ns); 
        this.addChild(_video); 

        _stream_ns.play("http://asd.com/test.mp4"); 

我正在尝试从http播放mp4文件，但没有任何事情发生。我只是使用Flex for android（flash builder 4.6）