Hi
i searched this forum and saw that it was not pssobilepossible to put a waterwak (subtitle or text on the video) without reencoding. I understand that.

What i want to do is to let people download mp4 files and make each downloaded file unique with an invisible 'signature' (i don t know if it is the right word (i am not english fluent).

Is that possible to add a header or something else on the fly on the mp4 file downloaded?

i am not searching to put some drm on the file, but just to find out who put the file on P2P if it happens.

Regards