An amplifier includes a first reception section which receives multimedia data via the Internet, a first separation section which separates sound data from the multimedia data, a synchronization data generation section which generates synchronization data based on the sound data, and a synchronization data transmission section which transmits the synchronization data to a set-top box via an infrared communication channel; and the set-top box includes a second reception section which receives the multimedia data via the Internet, a second separation section which separates image data from the multimedia data, a synchronization data reception section which receives the synchronization data via the infrared communication channel, and a matching section which determines reproduction target image data based on the synchronization data.