Fellow speaker,
Jeremy Donovan's study of TED talks suggests when you use videos, it helps to use videos that steadily get briefer and briefer. This gives the audience the sense that the speech is quick moving. For example, start out with a 90 second video, followed by a 60 second video followed by a 30 second video followed by a 15 second video. Make sure to discuss relevant points between the videos.
Quickly,
Tim Wilson
Professional Speech Coach
Free speaking tips at: http://speakingquicktips.blogspot.com
