Yes, you can share a video clip on your desktop to other participants.
Click Share Screen.
Select "Share computer sound" and "Optimize for full-screen video clip"
Click Share.
Our colleagues in NUS have shared that it seems to stream better for participants when the video is playing on a dedicated Video Player like VLC or QuickTime and in full screen.
Playing a video embedded in a powerpoint slides or playing on a website like YouTube, doesn't seem as smooth in comparison.