13. A method comprising: receiving, in a portable audio device, audio data representing samples of audio content, for rendering into human-perceptible sound; applying a digital watermark decoding or audio fingerprinting algorithm to the received audio data to derive identification data therefrom; by reference to the derived identification data, selecting a favored software program for rendering of said audio data into said human-perceptible sound, said selecting being performed by a processor in the portable device that is configured to perform such act; and indicating the favored software program to a user; wherein the favored software program for rendering the audio data is selected based on identification data derived from the audio data.
13. A method comprising: receiving, in a portable audio device, audio data representing samples of audio content, for rendering into human-perceptible sound; applying a digital watermark decoding or audio fingerprinting algorithm to the received audio data to derive identification data therefrom; by reference to the derived identification data, selecting a favored software program for rendering of said audio data into said human-perceptible sound, said selecting being performed by a processor in the portable device that is configured to perform such act; and indicating the favored software program to a user; wherein the favored software program for rendering the audio data is selected based on identification data derived from the audio data. 14. The method of claim 13 that includes: receiving user input identifying a software program for rendering said audio data; and if the software program identified by the received user input is not the favored software program, then limiting use of the identified software program with the audio content.