Patent ID: 7092885

Claim:
A speech decoding method according to code-excited linear prediction (CELP) wherein the speech decoding method receives a coded speech including a linear prediction parameter code and an adaptive code, and a gain code, and synthesizes a speech using at least an excitation codebook, the speech decoding method comprising: obtaining an adaptive code vector from an adaptive codebook based on the received adaptive code; obtaining a time series vector with a noise level from the excitation codebook based on the excitation code; decoding a gain of the adaptive code vector and a gain of the time series vector from the gain code; determining whether modification of the time series vector is necessary; if modification of the time series vector is determined to be necessary, modifying the time series vector such that the density of zero-amplitude samples is changed as a function of whether the coded speech is voiced or unvoiced; weighting the adaptive codebook vector and the time series vector using the decoded gains as weights; adding together the weighted adaptive codebook vector and the weighted time series vector; decoding a linear prediction parameter from the received linear prediction parameter code; and synthesizing a speech using the linear prediction parameter and the addition result.