I need to build a web based video player. Something like coursera/udemy. I would like to know the following.
There can be no way to protect your video from a determined sophisticated hacker. In the very worst case, they can record the video from their screen using a iPhone.
You can learn more about blob:
URL e.g. here. The bottom line: it's a browser-side object, it's not to store videos.
You definitely can use streaming services, but this will even further reduce your control. OTOH, it's not worth your effort to develop some new streaming architecture if you only expect 500 concurrent streams.