When you link to (at least) a Vimeo video using the video element, it includes a black border on each side.
Why and how do you remove it? (I don’t use the video as background)
1. put a negative padding on the video. That only removes one side and moves the “in video” buttons so that doesn’t work.
2. Put the videon inside a group and make the group smaller than the video. It looks ok in the editor, but live the video adjusts its size to the group dimensions. Doesn’t work either.
This topic How to display video without youtube border on my web page talks about Youtube. Not sure if it’s the same problem.