Regarding Youtube, I just used the iframe link that Youtube provided and defined my own size for the frame:

    <div><iframe width="220" height="165" src="//www.youtube.com/embed/XgYu7-DQjDQ" frameborder="0" allowfullscreen></iframe></div>

This displayed as a video frame right there on the page, which could be viewed in the thumbnail size and in full screen view as well as on Youtube, since the frame contains the link.

I hope this helps.
Gábor