I'm not a native English speaker, so even though all the lectures have really kind and exact pronounced speeches, some parts are hard to understand only by listening.
I know this is a kind of annoying works, but if you can provide subtitles or scripts for lectures, I guess that it will contribute much for enlarging the potential of this service.
@bobbybouwmann Edx videos go through automatic speech recognition to produce caption and transcript. They use external service from Cielo24 or 3 Play Media.
@Tetravalence True, however more than 2 years ago the tools weren't that good and an external service might make mistakes which is not ideal in a tutorial video ;)