Encoder, decoder, encoding method, and decoding method

An encoding apparatus that generates low-frequency-band encoding information and high-frequency-band encoding information from an original signal, the encoding apparatus comprising:

• a first spectrum calculating section that calculates a first spectrum of a low frequency band from a decoded signal of the low-frequency-band encoding information;
• a second spectrum calculating section that calculates a second spectrum from the original signal;
• an estimating section that estimates a high frequency band of the second spectrum using the first spectrum;
• a parameter encoding section that encodes a parameter indicating a part in the first spectrum that is most similar to a spectrum included in the high frequency band of the second spectrum;
• and
• a second error component encoding section that encodes a second error component between the first spectrum and a low frequency band of the second spectrum,
• wherein the parameter encoding section encodes the parameter after having improved quality of the first spectrum using the second error component encoded by the second error component encoding section.

A decoding apparatus comprising:

• a spectrum acquiring section that acquires low-frequency-band encoding information and high-frequency-band encoding information;
• a spectrum calculating section that calculates a first spectrum from a decoding signal of the low-frequency-band encoding information;
• and
• a parameter acquiring section that acquires a first parameter and a second parameter, the first parameter as high-frequency-band encoding information and indicating an estimated spectrum that is a part in the first spectrum and is most similar to a high frequency band of the second spectrum corresponding to an original signal, the second parameter being encoded as high-frequency-band encoding information and indicating an error component between the estimated spectrum and the high frequency band of the second spectrum;
• and
• a decoding section that decodes the second spectrum using the acquired first parameter and second parameter.

An encoding apparatus for generating low-frequency-band encoding information and high-frequency-band encoding information from an original signal, the encoding method comprising:

• calculating a first spectrum of a low frequency band from a decoded signal of the low-frequency-band encoding information;
• calculating a second spectrum from the original signal;
• estimating a high frequency band of the second spectrum using the first spectrum;
• encoding a parameter indicating a part in the first spectrum that is most similar to a spectrum included in the high frequency band of the second spectrum;
• and
• encoding a first error component between the high frequency band of the second spectrum and an estimated spectrum indicated by the parameter.

A decoding method comprising:

• acquiring low-frequency-band encoding information and high-frequency-band encoding information;
• calculating a first spectrum from a decoding signal of the low-frequency-band encoding information;
• and
• acquiring a first parameter and a second parameter, the first parameter being encoded as high-frequency-band encoding information and indicating an estimated spectrum that is a part in the first spectrum and is most similar to a high frequency band of the second spectrum corresponding to an original signal, the second parameter being encoded as high-frequency-band encoding information and indicating an error component between the estimated spectrum and the high frequency band of the second spectrum;
• and
• decoding the second spectrum using the acquired first parameter and second parameter.