A data processing apparatus transmits and receives moving image data to and from an external device through a transmission path. A first pipe used for transferring the moving image data and a second pipe used for transferring timing information relating to the processing timing of the moving image data are provided on the transmission path. The moving image data is being transferred to the external device through the first pipe in parallel with the timing information relating to the moving image data being transferred through to the external device through the second pipe.