Auto-detection of audio formats is provided by using an auto-detect element to exploit differences among multiple formats to output a format select signal corresponding to the input to the auto-detect element. In a preferred embodiment, edge detection circuitry and a time counter are employed to recognize multiple audio formats automatically. The format select signal output from the auto-detect element is output to a multiplexer, or other switching means for switching among multiple input formats, so that the correct input signal processing is used. The auto-detect element removes the need for an external hardware select pin, thereby reducing the number of input pins to the circuit.