1. A method for an audio processing device to encode audio, the method comprising: transforming an input block of an audio signal into spectral data, wherein the spectral data has a baseband portion and an extended portion; coding the baseband portion of the spectral data into an output bitstream; in the extended band portion of the spectral data, determining characteristics of spectral data; altering an initial configuration by which the extended band portion of the spectral data is segmented into a plurality of sub-bands based on the determined characteristics; coding the altered configuration of sub-bands comprising data indicating individual sub-bands in the extended band altered from the initial configuration.