Patent ID: 8600737

Claim:
A method of processing an audio signal having frequency content in a low-frequency subband and in a high-frequency subband that is separate from the low-frequency subband, said method comprising: filtering the audio signal to obtain a narrowband signal and a superhighband signal; based on information from the narrowband signal, calculating an encoded narrowband excitation signal; based on information from the encoded narrowband excitation signal, calculating a superhighband excitation signal; based on information from the superhighband signal, calculating a plurality of filter parameters that characterize a spectral envelope of the high-frequency subband; and calculating a plurality of gain factors by evaluating a time-varying relation between a signal that is based on the superhighband signal and a signal that is based on the superhighband excitation signal, wherein the narrowband signal is based on the frequency content in the low-frequency subband, and wherein the superhighband signal is based on the frequency content in the high-frequency subband, and wherein a width of the low-frequency subband is at least three kilohertz, and wherein the low-frequency subband and the high-frequency subband are separated by a distance that is at least equal to half of the width of the low-frequency subband.