Passing a variable to a video

I’m posting this again, 'cause I have posted in the wrong section…

hi all,

I’m doing an online teaching system and I was wondering if it would be possible to pass a variable to a video in real time. Nowadays it’s pretty much impossible to prevent a video to go into the web. Even if the user can’t download the video, he will record his screen. The guy who asked me to do this system wants at least to know which user posted id and for that I need to be able to insert the user’s name or id into the video. One way to do that is to have one video for each user, but that is storage and time consuming. That is why I’m looking for something that allows me to change the video in real time: either send a variable to the video or insert something like a frame into it.

much appreciated