[Object]To make it possible for the reception side to carry out an optimum process for an image signal (image data) depending upon the type of a content.[Solving Means]An AV system 40 composed of an HD recorder 41 and a display unit 42 uses a communication interface of the HDMI. An HDMI source 53 of the HD recorder 41 transmits image data (image signal) in the form of differential signals to an HDMI sink 61 of the display unit 42 through three TMDS channels. The HDMI source 53 inserts content identification information for the identification of the type of a content of image data to be transmitted into an AVI InfoFrame packet placed in a blanking period. A control section 64 of the display unit 42 controls operation of a display processing section 62 which carries out a process for displaying for the image data based on the content identification information (ITC, CT1 and CT0) received by the HDMI sink 61 and a display section 63 for displaying an image.