In a previous life I edited video for a living. During slow periods, my employer would bring in work from “other sources” which included pornography. The director would have viewed all of it frame by frame, and would specify how he wanted the “film” to progress.
After a couple of those, it was time to find a new line of work, and with it a new appreciation of what pornography is not.
Oh gee now I know who dubs in that cheese 70’s porn music in all the videos!!
http://www.youtube.com/watch?v=S6kxau0ePlg&feature=related