An alternative that often works is to open the transcript and simply read it. If you find something unclear you can click to jump to that point. Coursera classes have this feature too.
Obviously doesn't work for everything, but it's especially useful when you want to know more about a subject you already know about (say a programming language you've used but never formally learnt).
If I can't do this I usually just close the tab -- the information rate of a video is typically quite low.