          some frame rates. 15, 24, 25, 29.97,
                                   and 30 should work with most codecs.  

     framesPerSecond   X      X    An alias for fps.

     fpsNum, fpsDenom  X      X    This pair of parameters allows frames
                                   per second to be specified as a
                                   rational number.  Either both or
                                   neither parameter must be given.

     framesPerSecond_num           Alias for fpsN