Reference Manual - 1.0.0
IDirectFBVideoProvider   SetSpeed

Set the speed multiplier.

SetSpeed (
  IDirectFBVideoProvider   * thiz,
  double   multiplier
);

Values below 1.0 reduce playback speed while values over 1.0 increase it.
Specifying a value of 0.0 has the effect of putting the playback in pause mode without stopping the video provider.