A portable terminal, the portable terminal comprising: a storage unit configured to store digital data encoded in a predetermined format; a decoder unit configured to decode digital data stored in the storage unit; an USB device controller configured to support an interface (1051-1054) to communicate with an audio/video system having an USB host controller , the USB controllers being capable of performing transmission and reception of control information in both directions and transmission and reception of the decoded digital data in one direction; a digital/analog conversion unit configured to convert decoded digital data into analog data; an output unit configured to output the analog data; and a control unit configured to receive control information from the audio/video system through the USB device controller, to cause the decoder unit to decode the stored digital data corresponding to the received control information and to cause a transmission of the decoded digital data to the audio/video system, wherein the direction of transferring data is changed according to a switching principle that either causes the decoded digital data to be transferred to the audio/video system, or that causes the conversion of the decoded digital data into analog data, and said analog data to be output to the output unit of the portable terminal, and wherein the USB device controller comprises a streaming terminal transmitting the decoded digital data, an interface terminal receiving the control information, and a setup terminal for transmitting and receiving information required to set the streaming and interface terminals. a storage unit configured to store digital data encoded in a predetermined format; a decoder unit configured to decode digital data stored in the storage unit; an USB device controller configured to support an interface (1051-1054) to communicate with an audio/video system having an USB host controller , the USB controllers being capable of performing transmission and reception of control information in both directions and transmission and reception of the decoded digital data in one direction; a digital/analog conversion unit configured to convert decoded digital data into analog data; an output unit configured to output the analog data; and a control unit configured to receive control information from the audio/video system through the USB device controller, to cause the decoder unit to decode the stored digital data corresponding to the received control information and to cause a transmission of the decoded digital data to the audio/video system, wherein the direction of transferring data is changed according to a switching principle that either causes the decoded digital data to be transferred to the audio/video system, or that causes the conversion of the decoded digital data into analog data, and said analog data to be output to the output unit of the portable terminal, and wherein the USB device controller comprises a streaming terminal transmitting the decoded digital data, an interface terminal receiving the control information, and a setup terminal for transmitting and receiving information required to set the streaming and interface terminals. <EOS>