[Problem] In a system for transmitting content data from a content reproducing apparatus to a content output apparatus, no complicated signal processing is required, setting change operations can be simplified, and the degradation of sound quality and the degradation of picture quality of video data are prevented. [Solution] There are included: a content reproducing apparatus that receives an operation clock signal from a content output apparatus via an operation clock transmission cable, operates on the basis of the operation clock signal, and transmits content data, which has been reproduced by a reproducing unit, to the content output apparatus via a multimedia transmission cable; and the content output apparatus that generates, on the basis of an output apparatus operation clock signal, the operation clock signal to be transmitted to the content reproducing apparatus, transmits the operation clock signal to the content reproducing apparatus reproducing apparatus via the operation clock transmission cable, receives the content data from the content reproducing apparatus via the multimedia transmission cable, and performs a signal processing of the received content data for output to an external apparatus.