When you absorb information visually, either by reading or looking at pictures, you can go as quickly or slowly as you like. It's like the audio machines I used when translating - glorified tape recorders with frequency correction based on tape playback speed, with foot pedals so you could go faster, slower, or rewind. Except you don't need any of that equipment with text or pictures.
This is why video and audio will always be an inferior method of transferring knowledge than reading and diagrams/pictures. You can use video and audio samples to demonstrate things which are best seen/heard in real-time, and live presentations are superior if they allow interaction between instructor and student. But for a general information dump, text and pictures allow the highest bandwidth, with the bandwidth controlled by the reader's mind. Video is like presenting a textbook as a flash animation with a fixed scroll speed, where you need to mess with clumsy fast-forward and rewind buttons to control bandwidth.