Based on your clarification, it sounds like you're asking a question about parsing XML. Here's an alternative: get back JSON, and parse that. You can make a request like
http://gdata.youtube.com/feeds/api/videos/tYMYv1zsAxE?v=2&alt=jsonc&prettyprint=true
and then look at the data->accessControl->embed element within the JSON response.
Or, you know, just parse and access the YouTube API XML exactly like you'd parse the XML from any other source. There's nothing magic going on with the YouTube API XML.