4D film is an immersive entertainment system that presents various physical effects with a film in order to enhance viewers' experiences. Despite the recent emergence of 4D theaters, production of 4D effects relies on manual authoring. In this paper, we present algorithms that synthesize three classes of motion effects from the audiovisual content of a film. The first class of motion effects is those responding to fast camera motion to enhance the immersiveness of point-of-view shots, delivering fast and dynamic vestibular feedback. The second class moves viewers as closely as possible to the trajectory of slowly moving camera. Such motion provides an illusional effect of observing the scene from a distance while moving slowly within the scene. For these two classes, our algorithms compute the relative camera motion and then map it to a motion command to the 4D chair using appropriate motion mapping algorithms. The last class is for special effects, such as explosions, and our algorithm uses sound for the synthesis of impulses and vibrations. We assessed the subjective quality of our algorithms by user experiments, and results indicated that our algorithms can provide compelling motion effects.