1. An audio encoding method, comprising: transforming an input audio signal into a set of spectral coefficients; coding a baseband portion of the set of spectral coefficients in the output bitstream; dividing an extended band of the spectral coefficients into plural sub-bands; scaling the plural sub-bands in the extended band; transforming at least one codeword from a library of plural codewords using a codeword transform; comparing the set of spectral coefficients of a sub-band to at least one transformed codewords from the library; coding the spectral coefficients of the sub-band in an output bitstream comprising coding an identifier of one or more codewords from the library and a codeword transform identifier.