For everyone else still curious the problem to overcome is getting a direct link to the video which does require a small hack but it's very reliable and easy to do. Firstly you need the video id so you can get the youtube url which you can use the youtube api for. Then do something like this. I pretty much converted a userscript to silverlight.
WebClient client = new WebClient();
string url = "http://www.youtube.com/watch?v=HLQqOpILDcI";
client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(ClientDownloadStringCompleted);
client.DownloadStringAsync(new Uri(url, UriKind.Absolute));
the next bit looks bad.
private void ClientDownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
rx = new Regex("(?<=url_encoded_fmt_stream_map=)([^(\\\\)]*)(?=\\\\)", RegexOptions.IgnoreCase);
match = rx.Matches(flashvars);
string video_format = match[0].ToString();
string sep1="%2C";
string sep2="%26";
string sep3="%3D";
string link = "";
string[] videoFormatsGroup = Regex.Split(video_format, sep1);
for (var i=0;i<videoFormatsGroup.Length;i++){
string[] videoFormatsElem = Regex.Split(videoFormatsGroup[i], sep2);
if (videoFormatsElem.Length<5) continue;
string[] partialResult1 = Regex.Split(videoFormatsElem[0], sep3);
if (partialResult1.Length<2) continue;
string url = partialResult1[1];
url = HttpUtility.UrlDecode(HttpUtility.UrlDecode(url));
string[] partialResult2 = Regex.Split(videoFormatsElem[4], sep3);
if (partialResult2.Length<2) continue;
int itag = Convert.ToInt32(partialResult2[1]);
if (itag == 18){
link = url;
}
}
}
the last bit itag==18 selects the quality according to this
{'5':'FLV 240p','18':'MP4 360p','22':'MP4 720p (HD)','34':'FLV 360p','35':'FLV 480p','37':'MP4 1080p (HD)','38':'MP4 4K (HD)','43':'WebM 360p','44':'WebM 480p','45':'WebM 720p (HD)','46':'WebM 1080p (HD)'};
now you can do whatever you want with the link like open it with mediaplayerlauncher or mediaelement. personally i'd love to download it to isolated storage and play it at the same time but at the moment that seems easier said than done. thanks for your time sorry for the long post.