Coding Apparatus and Decoding Apparatus

A scalable coding apparatus that encodes a voice signal or audio signal separated into a low frequency band and high frequency band, the scalable coding apparatus comprising:

• a first coding section that encodes a low frequency band signal of the voice signal or the audio signal;
• a second coding section that encodes a high frequency band signal of the voice signal or the audio signal;
• a first spectrum generation section that performs frequency domain conversion of the low frequency band signal and generates a first spectrum of the low frequency band;
• and
• a second spectrum generation section that performs frequency domain conversion of the voice signal or the audio signal, and generates a second spectrum including the low frequency band and the high frequency band,
• wherein the second coding section comprises:
• a generation section that calculates an estimated spectrum of the high frequency band of the second spectrum using the first spectrum;
• a search section that searches for a parameter indicating the estimated spectrum having a highest similarity to the high frequency band of the second spectrum;
• and
• a coding section that encodes the parameter indicating the estimated spectrum having the highest similarity, instead of the high frequency band of the second spectrum.

A spectrum decoding apparatus comprising:

• a spectrum acquisition section that acquires a spectrum of a low frequency band out of a spectrum including the low frequency band and a high frequency band;
• a parameter acquisition section that acquires a parameter indicating an estimated spectrum that is generated using the spectrum of the low frequency band and that has a highest similarity to a spectrum of the high frequency band associated with an original signal;
• and
• a decoding section that decodes the spectrum of the low frequency band and the spectrum of the high frequency band using the spectrum of the low frequency band and the parameter.

A spectrum coding method for encoding a spectrum including a first band and a second band, the coding method comprising:

• a generating step of calculating an estimated spectrum of the second band using a spectrum of the first band having at least a bandwidth of the second band;
• a searching step of searching for a parameter indicating the estimated spectrum having a highest similarity to a spectrum of the second band;
• and
• a coding step of encoding the parameter indicating the estimated spectrum having the highest similarity, instead of the spectrum of the second band.

A spectrum decoding method comprising:

• a spectrum acquiring step of acquiring a spectrum of a low frequency band out of a spectrum including the low frequency band and a high frequency band;
• a parameter acquiring step of acquiring a parameter indicating an estimated spectrum that is generated using the spectrum of the low frequency band and that has a highest similarity to a spectrum of the high frequency band associated with an original signal;
• and
• a decoding step of decoding the spectrum of the low frequency band and the spectrum of the high frequency band using the spectrum of the low frequency band and the parameter.