I want to learn some technique about video decryption to download some protected videos online,I find a great video describing what I am explaining text, it shows all the process about how videos are requested and sent from the client and server, is there more concise tutorial or books that explains them in more detail from top to bottom, what other knowledge do I need to master to finally be able to decrypted various videos by myself? here is a link about someone decrpyt the video in pratical, text, I hope I can do something like this.