Why onMetaData handler doesn't be called when playing some .flv?

Question

Hello, Everyone,
I am encountering a problem:
I am using NetStream to play some .flv files on local disc. My code skeleton is:
public class AdvertisPanel extends MovieClip
          private var _video:Video;
          private var _connection:NetConnection;
          private var _stream:NetStream;
          private var _clientObject:Object;
          public function AdvertisPanel($playlist:Array, $delay:int)
                    ....(code omitted)
          public function build():void
                    this._video = new Video();
                    this._connection = new NetConnection();
                    this._connection.connect(null);
                    this._stream = new NetStream(this._connection);
                    this._video.attachNetStream(this._stream);
                    this._clientObject = new Object();
                    this._clientObject.onMetaData = this.metaDataListener;
                    this._clientObject.onXMPData = this.XMPDataListener;
                    this._stream.client = this._clientObject;
                    this._stream.addEventListener(NetStatusEvent.NET_STATUS, this.netStreamStatusHandler);
                    this._stream.addEventListener(IOErrorEvent.IO_ERROR, this.netStreamIOErrorsHandler);
                    this._stream.addEventListener(AsyncErrorEvent.ASYNC_ERROR, this.netStreamAsynErrorsHandler);
                    this.addChild(this._video);
                    this._stream.play(this._medias[this._currentPlayingIndex].mediafile); // this is the url of the video
          private function metaDataListener($metaData:Object):void
                    ....(code omitted)
                    trace(metaData.duration, $metaData.width, $metaData.height);
          private function XMPDataListener($xmpData:Object):void
                    ....(code omitted)
                    trace($xmpData);
          ....(code omitted)
I used some .flv files that I download from YouTube to test; and I found that the handler metaDataListener would not be called when playing some .flv files, but some would. Is the problem caused by the video file? Because I may resize the video before play it on the screen, and I really need to know its original width & height.
Would some ont help with that? Thanks a lot in advance.

Answer 1

Thanks, Donny.
But I failed to open the .flv file with Adobe Media Encoder, it said that the format was not suported.
And the .flv is downloaded from YouTube.