I don't think this BB has the ability to upload a video clip to it, because of general upload restrictions, relating to the size of the uploaded file.
Best technique .. is to upload to free video upload website of your choice (e.g. - YouTube, Putfile, Rapidshare) .. then post the URL link to it, on here ..
It saves the bandwidth on this site from being eaten up excessively, thataway .. video files can be sizeable ..