Black bars at top and bottom / Video Thumbnails

Hi and thanks much for this plugin.

I saw the topic and the explanation here: https://wordpress.org/support/topic/video-thumbnail-black-bars?replies=2 and here: https://wordpress.org/support/topic/black-bars-at-top-and-bottom?replies=8

I’m sorry but I could’t understand it exactly. Because the thumbnail of this video: https://www.youtube.com/watch?v=DAUsktOU8LY is this: http://i.ytimg.com/vi/DAUsktOU8LY/mqdefault.jpg

But on my website with video thumbnails plugin it is like this: http://i.imgur.com/hI5oBPv.png (with black bars)

How can it be possible?

Thanks in advance

https://wordpress.org/plugins/video-thumbnails/