Disclosed herein is a signal processing apparatus including a plurality of frame head detection sections configured to determine whether a frame head complying with any one of a plurality of different communication methods is detected by comparing the waveform of a signal sent from an external apparatus with a plurality of predetermined different symbol patterns; a communication method selection section configured to select the communication method for communicating with the external apparatus based on results of the determination by the frame head detection sections and on the priority of each of the plurality of communication methods; and a priority changing section configured such that if a second communication method different from an initially selected first communication method is selected anew, then the priority changing section changes the priority of each of the plurality of communication methods based on the newly selected second communication method.