How to obtain the "seek to" time in MPMoviePlayerController?

I am using an MPMoviePlayerController instance to play live-streaming videos. When the user seeks forward or backward, I want to obtain the time 开发者_StackOverflow中文版to which the play-head should seek to.

MPMoviePlayerPlaybackStateDidChangeNotification notifies me of a seek event just fine, and currentPlaybackTime returns the current time i.e. before seeking. How do I obtain the "seek-to" time without waiting for the next MPMoviePlaybackStatePlaying notification?