Ralph McDaniels has forgotten more about hip hop than most people have ever known. The creator and host of the New York City public access show “Video Music Box,” which debuted in 1983, McDaniels had a decades-long run documenting the evolution of hip hop from the front row and backstage. Now the show and McDaniels himself are the subjects of a new documentary, out on Showtime, called “You’re Watching Video Music Box,” directed by Nas. We discuss his life in hip hop history.