Can I crop the borders of a video directly on Prezi like I could do for an image?
You may also try this method to crop video at http://www.idealshare.net/video-converter/video-cropper.html
Hello Charlotte Kelly,
as a workaround (depending on your Prezi background) you may be able to use a .png or .swf file with a transparent background to cover the video (this works with the flash player when presenting) in this way you could crop part the video and show what you need.
hope this helps