Patent ID: 8688440

Claim:
A coding apparatus comprising: an acquisition section that acquires a spectrum of a voice signal including a low frequency band spectrum and a high frequency band spectrum; a first coding section that codes the low frequency band spectrum, to generate first coded information; a first decoding section that decodes the first coded information, to generate decoded low frequency band spectrum; a generation section that generates a shape of an estimated high frequency band spectrum by duplicating the decoded low frequency band spectrum; a first subband amplitude calculation section that divides the estimated high frequency band spectrum into a plurality of subbands and calculates a first average amplitude value of the estimated high frequency band spectrum in each of the plurality of subbands; a second subband amplitude calculation section that divides the high frequency band spectrum into a plurality of subbands and calculates a second average amplitude value of the high frequency band spectrum in each of the plurality of subbands; a gain codebook that outputs only a gain of specific subbands, the specific subbands including a subband of the estimated high frequency band spectrum adjacent to the low frequency band spectrum among the plurality of subbands of the estimated high frequency band spectrum; an interpolation section that finds a gain of a subband of the estimated high frequency band spectrum other than the specific subbands by interpolating the gain of the specific subbands; a multiplication section that multiplies the first average amplitude value by the gain output from the gain codebook or the interpolation section in each of the subbands; a second coding section that calculates a distortion between a multiplied result of the multiplication section and the second average amplitude value and codes only the gain of the specific subbands when the distortion is smallest; and an output terminal that outputs coded information obtained by the first and second coding sections.