Audio taped conversations require authorization from both sides unless there is a wiretap warrant. This includes cellular conversations pulled from airwaves in the public domain since the communication is intended to be within a "reasonable expectation of privacy". This is why paparrazi taking pictures through brush hedges is illegal.

Video in a public parking lot is admissable. Same with following a couple from a driveway to the front door when viewed from public streets. Ask any private investigator working an adultry case.

Video on private property where the public visits (grocery store, banks) must first inform the people that they will be taped, but do not have to permit the subjects to "opt-out" of surveillance since it's on public property.