Copy Protection of video file

If the video has already been played on client computer, it means it has been "copied" already. If this is a media streaming, no copy of the media is available on the local computer in the form of a file. For majority of users it will be very difficult to save the file. However, for the expert it won't be a big problem, no matter how hard you "protect" it. If the media player can play it, it means some other player can play and save it. So, even for a non-expert person who is able to do Web search and read documentation obtaining a copy would be possible. For example, VLC will do the trick is one is able to read its help and write a pretty complex command line.

—SA

There's no way to do that. In order to play the file, it must be readable by the user. In order to copy the file, it must be readable by the user. Since code runs AS the user, it can do anything the user can do. See what's happening?

A file read operation is a file read operation. There's no way to tell the difference between the two operations, nor for what purpose the file being operation is being used for.

You cannot copy protect a file like that.