In Finland (You know, in Europe) it is legal to record conversations in general that you participate. There are examples where citizens have videotaped cops in their duties and complained about them in court. Supreme court has always thought that it is legal to record or take a video of a conversation that you videotape. The point is that you won't violate other persons privacy.
But it is a different thing if you publish the conversation. Then it brings up a different question: will the published video or tape offend the other persons privacy?
But answering the question: it is legal to tape or videotape conversation with anyone and it doesn't matter if the other person knows about it or not.