Patent ID: 7058571

Claim:
An audio decoding apparatus for decoding an audio signal from a bitstream containing encoded information about a narrowband audio signal and additional information for expanding the narrowband audio signal to a wideband audio signal, the additional information containing high frequency component information denoting a feature of a frequency band higher than a frequency band of the encoded information narrowband audio signal, and sinusoid-adding information denoting a sinusoidal signal added to a specific frequency band, said audio decoding apparatus comprising: a bitstream demultiplexer operable to demultiplex the encoded information and the additional information from the bitstream; a decoder operable to decode the narrowband audio signal from the demultiplexed encoded information; an analysis subband filter operable to separate the decoded narrowband audio signal into a first subband signal composed of a plurality of subband signals; a sinusoidal signal generator operable to generate a sinusoidal signal added to a specific subband at a frequency band higher than a frequency band of the encoded information of the narrowband audio signal based on the sinusoid-adding information in the demultiplexed additional information; a correction signal generator operable to generate, based on a phase characteristic and an amplitude characteristic of the sinusoidal signal, a correction signal added to subbands near a specific subband to suppress aliasing component signals occurring in the subbands near the specific subband; a high frequency signal generator operable to generate a second subband signal composed of a plurality of subband signals in a frequency band higher than the frequency band of the encoded information of the narrowband audio signal from the first subband signal and high frequency component information in the demultiplexed additional information, and operable to add the sinusoidal signal and correction signal to the second subband signal; and a real-valued calculation subband synthesis filter operable to combine the first subband signal and the second subband signal to obtain the wideband audio signal.