Patent ID: 7941319

Claim:
An audio decoding apparatus comprising: a bit stream separator that separates a bit stream into a low-frequency bit stream and a high-frequency bit stream; a low-frequency decoder that decodes said low-frequency bit stream to generate a low-frequency audio signal; a subband divider that divides said low-frequency audio signal into a plurality of complex-valued signals in respective frequency bands to generate low-frequency subband signals; a corrective coefficient extractor that calculates an energy corrective coefficient based on said low-frequency subband signals; an energy corrector that corrects a target energy described by said high-frequency bit stream with said energy corrective coefficient to calculate a corrected target energy; a band expander that generates a high-frequency subband signal by correcting, in amplitude, the signal energy of a signal which is generated by copying and processing said low-frequency subband signals as instructed by said high-frequency bit stream, at said corrected target energy; and a subband combiner that combines real parts of said low-frequency subband signals and said high-frequency subband signals to produce a decoded audio signal, wherein said corrective coefficient extractor calculates the signal phase of said low-frequency subband signals and calculates the energy corrective coefficient based on said signal phase.