The read-only mode switch affects how movies interact with savestates after you start a movie playback and load a savestate. When you are in read-only mode, the movie will resume playing from the loaded savestate. When you are in read+write mode however, your input will be recorded over the original movie ('rerecording'). If you wish to start rerecording immediately, you should switch to R+W mode, save a state and then load it.
To make this more user-friendly, I also added a unique ID to the movies, which allows each movie to have an individual set of savestate slots (plus another set for when not doing any movies). This is as recommended by staff at TASVideos.
This adds a clock init time field to the CTM header. The clock settings would be overridden when playing a movie. And when recording a movie, if the clock is set to System Time, it would be set to fixed init time at the current moment as well. In this way this keeps consistency with the RNG even if the user does just no setting.
