I was reading about the Thomson Viper FilmStream Camera, an advanced (for the time) digital camera. It can operated at numerous fps rates. But some of them are not even fps and are slightly off. For instance the camera can operate at 24 fps but also 23.98. It can also operate at 29.97 and 59.94 but does not offer 30 or 60 fps rates. What do these odd rates achieve?