21. A non-transitory computer-readable medium comprising computer-readable instructions for causing a processor to: receive a portion of an audio signal at a first classifier in a digital audio device; classify, by the digital audio device, the portion of the audio signal at the first classifier as speech or as music; and process the portion of the audio signal, wherein processing the portion of the audio signal comprises: if the portion is classified by the first classifier as speech, then encode, by the digital audio device, the speech using a first coding mode; or if the portion is classified by the first classifier as music, then: provide the portion to a second classifier in the digital audio device; classify, by the digital audio device, the portion at the second classifier as speech or as music; and encode the portion of the audio signal, wherein encoding the portion of the audio signal comprises: if the portion is classified at the second classifier as speech, then encode, by the digital audio device, the portion using a second coding mode; or if the portion is classified at the second classifier as music, then encode, by the digital audio device, the portion using a third coding mode.
22. The computer-readable medium of claim 21 , wherein the portion of the audio signal is a frame.