Patent ID: 7797065

Claim:
An apparatus comprising: digital signal processor that applies at least a first digital filter to digital signals corresponding to a first audio channel to generate processed signals; a first gain stage coupled to the output of the digital signal processor that applies volume control to the processed signals; pulse-width-modulation (PWM) circuitry coupled to the output of the first gain stage, wherein the PWM circuitry includes a noise shaping function having an input coupled to the output of the first gain stage and the applies spectral noise shaping to the signal corresponding to the first audio channel; and automute detection circuitry having: a first input coupled to an input to the digital signal processor; a second input coupled to the output of the digital signal processor; a volume ramp output coupled to the first gain stage; a stop output coupled to the PWM circuitry, wherein the stop output controls the first gain stage to ramp a volume of the signals corresponding to the first audio channel responsive to an amplitude of digital signals corresponding to the first audio channel at the input of the digital signal processor being below a first threshold level, and wherein the stop output disables PWM circuitry for the first audio channel responsive to an amplitude of digital signals corresponding to the first audio channel at the output of the digital signal processor being below a second threshold level; and a noise shaper stop control circuit having an input coupled to the output of the noise shaping circuit and an output coupled to the stop output, wherein the noise shaper generates a stop signal responsive to a signal state at the output of the noise shaping circuit.