As a prof, pre-recording video lectures doesn't save time -- it's a lot of work. And then you can't see the faces of students and react to their current state o

As a prof, pre-recording video lectures doesn't save time -- it's a lot of work. And then you can't see the faces of students and react to their current state of understanding. Students "slowing down the class" are about 80% of the time providing the primary value of in-person instruction: they're creating the interaction that makes a lecture valuable. What you suggest has essentially been done, with "book" substituted for "video". That's why all those profs wrote books -- they figured the students could read beforehand, thus saving the teacher lecture time and allowing students who need extra help to visit during office hours. That's the dream; video is simply a change in format. I point out to students often what parts of the book they should return to when they struggled to follow. The most interesting question for me is what new technology adds or allows beyond old technologies. Analogize: what were the elements that changed from reading a serial in the paper to watching a show on TV to listening to a serial podcast to watching a YouTube series? As someone currently employed as a "prof who makes videos" I refuse to do any video unless I think it adds something beyond simply changing information format!