They're basically the master tapes, when it was shown it would be edited together (her face asking the questions, Gary's face answering the questions).
Oldman has said quite recently that he has come to believe Oswald did do it. Here he's just repeating Oliver Stone type stories of people claiming they met Oswald.
also he does stammer when not acting and apparently works hard to not stammer when he is on a job ..... he does loses it here a few times if you listen carefully
