Official comment
The black space is, according to both Vimeo and Wistia, because the original size of the video is not in the right aspect ratio. ONTRApages uses 16:9 aspect ratio. Common sizes for 16:9 aspect ratios are:
- 600 x 360
- 800 x 450
- 1200 x 675
You can determine the right height for a given width by using an online calculator such as this one: http://size43.com/jqueryVideoTool.html
The video will be resized to fit inside the ONTRApages video block if it is the correct aspect ratio. We are sill looking at this issue, though, as several customers have stated that the black bars surrounding their videos remain even after resizing them to the 16:9 aspect ratio in Vimeo and Wistia. (The black background is actually part of the HTML5 spec and we can't physically remove it).