Question

My goal is to make a open source YouTube player that can be controlled via global media keys.
The global key issue I got it covered but the communication between the YouTube player and my Windows Forms application just doesn’t work for some reason.

So far this is what I have:

private AxShockwaveFlashObjects.AxShockwaveFlash player;
player.movie = "http://youtube.googleapis.com/v/9bZkp7q19f0"
...
private void playBtn_Click(object sender, EventArgs e)
{
    player.CallFunction("<invoke name=\"playVideo\" returntype=\"xml\"></invoke>");
}

Unfortunately this returns:

"Error HRESULT E_FAIL has been returned from a call to a COM component."

What am I missing? Should I load a different URL?

The documentation states that YouTube player uses ExternalInterface class to control it from JavaScript or AS3 so it should work with c#.

UPDATED:

---

Method used to embed the player: http://www.youtube.com/watch?v=kg-z8JfOIKw

Also tried to use the JavaScript-API in the WebBrowser control but no luck (player just didn’t respond to JavaScript commands, tried even to set WebBrowser.url to a working demo, all that I succeeded is to get the onYouTubePlayerReady() to fire using the simple embedded object version )

I think there might be some security issues that I’m overseeing, don’t know.

UPDATE 2:

---

fond solution, see my answer below.

Answer 1

After a lot of tries and head-hammering, I’ve found a solution:

Seems that the Error HRESULT E_FAIL... happens when the flash dosen’t understand the requested flash call. Also for the youtube external api to work, the js api needs to be enabled:

player.movie = "http://www.youtube.com/v/VIDEO_ID?version=3&enablejsapi=1"

As I said in the question the whole program is open source, so you will find the full code at bitbucket.
Any advice, suggestions or collaborators are highly appreciated.

The complete solution:

Here is the complete guide for embedding and interacting with the YouTube player or any other flash object.

After following the video tutorial
, set the flash player’s FlashCall event to the function that will handle the flash->c# interaction (in my example it’s YTplayer_FlashCall )

the generated `InitializeComponent()` should be:

...
this.YTplayer = new AxShockwaveFlashObjects.AxShockwaveFlash();
this.YTplayer.Name = "YTplayer";
this.YTplayer.Enabled = true;
this.YTplayer.OcxState = ((System.Windows.Forms.AxHost.State)(resources.GetObject("YTplayer.OcxState")));
this.YTplayer.FlashCall += new AxShockwaveFlashObjects._IShockwaveFlashEvents_FlashCallEventHandler(this.YTplayer_FlashCall);
...

the FlashCall event handler

private void YTplayer_FlashCall(object sender, AxShockwaveFlashObjects._IShockwaveFlashEvents_FlashCallEvent e)
{
    Console.Write("YTplayer_FlashCall: raw: "+e.request.ToString()+"\r\n");
    // message is in xml format so we need to parse it
    XmlDocument document = new XmlDocument();
    document.LoadXml(e.request);
    // get attributes to see which command flash is trying to call
    XmlAttributeCollection attributes = document.FirstChild.Attributes;
    String command = attributes.Item(0).InnerText;
    // get parameters
    XmlNodeList list = document.GetElementsByTagName("arguments");
    List<string> listS = new List<string>();
    foreach (XmlNode l in list){
        listS.Add(l.InnerText);
    }
    Console.Write("YTplayer_FlashCall: \"" + command.ToString() + "(" + string.Join(",", listS) + ")\r\n");
    // Interpret command
    switch (command)
    {
        case "onYouTubePlayerReady": YTready(listS[0]); break;
        case "YTStateChange": YTStateChange(listS[0]); break;
        case "YTError": YTStateError(listS[0]);  break;
        default: Console.Write("YTplayer_FlashCall: (unknownCommand)\r\n"); break;
    }
}

this will resolve the flash->c# communication

calling the flash external functions (c#->flash):

private string YTplayer_CallFlash(string ytFunction){
    string flashXMLrequest = "";
    string response="";
    string flashFunction="";
    List<string> flashFunctionArgs = new List<string>();

    Regex func2xml = new Regex(@"([a-z][a-z0-9]*)(\(([^)]*)\))?", RegexOptions.Compiled | RegexOptions.IgnoreCase);
    Match fmatch = func2xml.Match(ytFunction);

    if(fmatch.Captures.Count != 1){
        Console.Write("bad function request string");
        return "";
    }

    flashFunction=fmatch.Groups[1].Value.ToString();
    flashXMLrequest = "<invoke name=\"" + flashFunction + "\" returntype=\"xml\">";
    if (fmatch.Groups[3].Value.Length > 0)
    {
        flashFunctionArgs = pars*emphasized text*eDelimitedString(fmatch.Groups[3].Value);
        if (flashFunctionArgs.Count > 0)
        {
            flashXMLrequest += "<arguments><string>";
            flashXMLrequest += string.Join("</string><string>", flashFunctionArgs);
            flashXMLrequest += "</string></arguments>";
        }
    }
    flashXMLrequest += "</invoke>";

    try
    {
        Console.Write("YTplayer_CallFlash: \"" + flashXMLrequest + "\"\r\n");
        response = YTplayer.CallFunction(flashXMLrequest);                
        Console.Write("YTplayer_CallFlash_response: \"" + response + "\"\r\n");
    }
    catch
    {
        Console.Write("YTplayer_CallFlash: error \"" + flashXMLrequest + "\"\r\n");
    }

    return response;
}

private static List<string> parseDelimitedString (string arguments, char delim = ',')
{
    bool inQuotes = false;
    bool inNonQuotes = false;
    int whiteSpaceCount = 0;

    List<string> strings = new List<string>();

    StringBuilder sb = new StringBuilder();
    foreach (char c in arguments)
    {
        if (c == '\'' || c == '"')
        {
            if (!inQuotes)
                inQuotes = true;
            else
                inQuotes = false;

            whiteSpaceCount = 0;
        }else if (c == delim)
        {
            if (!inQuotes)
            {
                if (whiteSpaceCount > 0 && inQuotes)
                {
                    sb.Remove(sb.Length - whiteSpaceCount, whiteSpaceCount);
                    inNonQuotes = false;
                }
                strings.Add(sb.Replace("'", string.Empty).Replace("\"", string.Empty).ToString());
                sb.Remove(0, sb.Length);                       
            }
            else
            {
                sb.Append(c);
            }
            whiteSpaceCount = 0;
        }
        else if (char.IsWhiteSpace(c))
        {                    
            if (inNonQuotes || inQuotes)
            {
                sb.Append(c);
                whiteSpaceCount++;
            }
        }
        else
        {
            if (!inQuotes) inNonQuotes = true;
            sb.Append(c);
            whiteSpaceCount = 0;
        }
    }
    strings.Add(sb.Replace("'", string.Empty).Replace("\"", string.Empty).ToString());


    return strings;
}

adding Youtube event handlers:

private void YTready(string playerID)
{
    YTState = true;
    //start eventHandlers
    YTplayer_CallFlash("addEventListener(\"onStateChange\",\"YTStateChange\")");
    YTplayer_CallFlash("addEventListener(\"onError\",\"YTError\")");
}
private void YTStateChange(string YTplayState)
{
    switch (int.Parse(YTplayState))
    {
        case -1: playState = false; break; //not started yet
        case 1: playState = true; break; //playing
        case 2: playState = false; break; //paused
        //case 3: ; break; //buffering
        case 0: playState = false; if (!loopFile) mediaNext(); else YTplayer_CallFlash("seekTo(0)"); break; //ended
    }
}
private void YTStateError(string error)
{
    Console.Write("YTplayer_error: "+error+"\r\n");
}

usage ex:

YTplayer_CallFlash("playVideo()");
YTplayer_CallFlash("pauseVideo()");
YTplayer_CallFlash("loadVideoById(KuNQgln6TL0)");
string currentVideoId = YTplayer_CallFlash("getPlaylist()");
string currentDuration = YTplayer_CallFlash("getDuration()");

The functions YTplayer_CallFlash, YTplayer_FlashCall should work for any flash-C# communication with minor adjustments like the YTplayer_CallFlash‘s switch (command).