PURPOSE: To prevent jamming of a film in a sound cinecamera, by decelerating or stopping a film driving motor when the quantity of sag of a film exceeds a certain value.

CONSTITUTION: If a film sags by a certain quantity when a switch SW2 interlocked with a release switch is turned on, a switch SW3' is turned off. Then, the voltage of a power source E is applied to a capacitor C3 to start charging. When a transitor TR4 is turned on by this charge voltage, a TR1 is turned on also. Then, TRs 2 and 3 are turned off, and a film driving motor FM is stopped. In this case, the motor FM may be decelerated. When the sag of the film is reduced by the stop of the motor FM, a regular film driving speed is restored again. Thus, the speed is balanced properly between a capstan motor CM and the film driving motor FM to prevent jamming of the film.