This was a video Syd made documenting his first (supposedly) experimentation with LSD. It was his use of acid that lead to his being dumped from the Pink Floyd. He literally turned into a zombie, doing things like standing on stage and just barking, or other outrageous behavior. Syd was eventually replaced by current Floyd guitarist and songwriter, David Gilmour, around the time of Pink Floyd's 1968 album, Ummagumma.