That is not supported out of the box by Onebox, but if you allow iframes from Facebook on the site settings, and grab the incorporation link in a Facebook video, you will get something like:
<iframe src="https://www.facebook.com/plugins/video.php?href=https%3A%2F%2Fwww.facebook.com%2FPortaDosFundos%2Fvideos%2F1981258538657064%2F&show_text=0&width=560" width="560" height="315" style="border:none;overflow:hidden" scrolling="no" frameborder="0" allowTransparency="true" allowFullScreen="true"></iframe>
Which should work like