In mm-renderer, the play speed is represented by an integer. Normal speed is represented by a value of 1000, and 0 is paused. Note that depending on the context's input media, trick-play speeds (such as negative, slower than normal or faster than normal) may not be supported.
To change the current play speed, call the function mmr_speed_set(). You can change the speed when the state is stopped; mm-renderer simply saves the setting and applies it when playback restarts.