US Patent 7619551 Audio codec, digital device and voice processing method

An audio codec is provided, comprising an analog to digital converter (ADC) operable to receive an analog input signal for producing a first digital signal, and a first decimator down samples the first digital signal to generate a first intermediate signal. A second decimator receives a second digital signal from a digital microphone and down sample the second digital signal to generate a second intermediate signal. A multiplexer selects either the first intermediate signal or the second intermediate signal as a selected signal based on a control signal. A third decimator down samples the selected signal to generate a down sampled signal. A data formatter produces a digital output signal based on the down sampled signal.