A low power, digital audio interface includes support for variable length coding depending on content of the audio data sent from the interface. A particularized coding system is implemented that uses techniques of silence detection, dynamic scaling, and periodic encoding to reduce sent data to a minimum. Other techniques include variable packet scaling based on an audio sample rate. Differential signaling techniques are also used. The digital audio interface may be used in a headphone interface to drive digital headphones. A detector in the interface may detect whether digital or analog headphones are coupled to a headphone jack and drive the headphone jack accordingly.