To hardly exert an influence by the scratch in the longitudinal direction of motion picture film, to obtain the sufficient quantity of diffused light and to compactly and inexpensively constitute a processor.

An S track or a P track where digital sound is recorded as a dot-like pit is formed on the left side or the right side of the left or the right perforation of the motion picture film 1. The light from an LED 51 is diffused on an elliptic diffusing plate 52 and radiated to the P track after it is made the diffused light whose diffusion angle is larger in the width direction than in the longitudinal direction of the film 1. The transmitted light transmitted through the P track is condensed on a line sensor 43A through a lens 42A and photoelectrically converted at the line sensor 43A, whereby the digital sound is reproduced.