Stream data and a command output from a drive device are individually packetized in a first packet processing unit. The stream data packet and the command packet are further multiplexed, and the multiplexed data is transmitted to a transmission path using a synchronous channel. When the command output from a decoding unit is packetized in a second packet processing unit, it is packetized by multiplexing flow control information output from the decoding unit, and is transmitted to the first packet processing unit using a synchronous channel of the transmission path. Based on this flow control information, reading/writing by the drive device is controlled.