Maximizing memory on video, personal opinion.

1) Listen carefully, this will work on your audio memory.

2) Create good notes, highlighting important points and making your notes aesthetically pleasing, kinesthetic memory.

3) Screenshot each time you write a specific note and make annotations on the screen - chart, visual memory.

30 minutes of video often represents between 1h15 and 1H30 of work... count for a 4h video...