Encoding apparatus, decoding apparatus, and methods

A coding apparatus, comprising:

• a processor;
• and
• a memory that stores instructions which, when executed by the processor, cause the processor to perform operations, including
• encoding a first band of an input audio signal to be a first spectrum;
• dividing the first spectrum into a plurality of sub-bands;
• searching a largest amplitude value of the divided first spectrum in each of the plurality of sub-bands;
• normalizing the divided first spectrum in each of the plurality of sub-bands with the largest amplitude values searched in each of the plurality of sub-bands;
• emphasizing a harmonic structure in the normalized first spectrum, wherein the processor removes or suppresses a spectrum part with an amplitude value less than a predetermined threshold in the normalized first spectrum;
• searching a best band that has a largest correlation value between each divided band of a second band spectrum and the emphasized first spectrum in which the harmonic structure is emphasized, the second band spectrum being higher than a predetermined frequency;
• and
• encoding the second band spectrum using lag information identifying the best band and transmitting the lag information to a decoder side.