Patent ID: 7454328

Claim:
A speech encoding apparatus that includes a sound source information encoder for selecting fixed excitation code for generating synthesized speech using the spectrum envelope information, and that outputs speech code of the input speech, said speech encoding apparatus comprising: a first distortion calculator for calculating a first encoding distortion corresponding to a noise-like fixed code vector output by a first fixed excitation codebook for a frame of the input speech; a first weight assignor for multiplying the first encoding distortion by a first fixed weight that is preset in accordance with a noise-like degree of noise-like fixed code vectors stored in said first fixed excitation codebook; a second distortion calculator for calculating a second encoding distortion corresponding to a non-noise-like fixed code vector output by a second fixed excitation codebook for the frame of the input speech; a second weight assignor for multiplying the second encoding distortion by a second fixed weight that is preset in accordance with a noise-like degree of non-noise-like fixed code vectors stored in said second fixed excitation codebook; and a distortion estimator for determining which of the noise-like and non-noise-like fixed code vector corresponds to the smaller one of the multiplication results obtained by said first weight assignor and by said second weight assignor, and selecting the determined one of the noise-like and non-noise-like fixed code vector to be the fixed excitation code, wherein the first fixed weight is different than the second fixed weight, and wherein the non-noise-like fixed code vectors stored in the second fixed excitation codebook are collectively more pulse-like, thus having a lesser noise-like degree, than the noise-like fixed code vectors stored in the first excitation codebook.