A data conversion system for converting data output from an information processor into data in a different format in real time while preventing image defects such as dropped frames or repeated frames in moving image data by synchronizing data transfer with converted data output. One of first and second nodes on an IEEE1394 bus functions as a cycle master, and first data is transferred from the first node to the second node in synchronism with a cycle start packet outputted from the cycle master. Second data generated by converting the first data by the second node is outputted in synchronism with an external reference signal. The system includes an external synchronizing signal receiver for receiving an external reference signal provided on at least one of the first and second nodes, and a synchronization adjustment unit for synchronizing the frequency of the cycle start packet output from the cycle master with the frequency of the reference signal received by the external synchronizing signal receiver.