Embed youtube video in tinymce editor

You may find that you can not embed youtube video in tinymce editor.
This is due to that YouTube upgrade the embed code to iframe, for example:
<iframe width="640" height="360" src="https://www.youtube.com/embed/rwQFwS26rrE?feature=player_detailpage" frameborder="0" allowfullscreen></iframe>

By default, iframe is filter out by tinymce. To add iframe in tinymce, add
   valid_elements : "iframe[src|title|width|height|allowfullscreen|frameborder]"
in  tinyMCE.init as below.
tinyMCE.init({
//....other configuration, and add
     valid_elements : "iframe[src|title|width|height|allowfullscreen|frameborder]"
  });