Patent ID: 7383177

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, a gain code, and an adaptive code, and synthesizes a speech using an excitation codebook and an adaptive codebook, the speech decoding method comprising: obtaining an adaptive code vector from the adaptive codebook based on the received adaptive code; decoding a gain from the gain code in a decoding period corresponding to the coded speech, the decoded gain being used for weighting the adaptive code vector; obtaining a time series vector with a number of samples with zero amplitude-value from the excitation codebook; determining whether modification of the time series vector is necessary according to the gain; if modification of the time series vector is determined to be necessary, modifying the time series vector such that the number of samples with zero amplitude-value is changed; weighting the adaptive code vector and the time series vector using the decoded gain as a weight; adding together the weighted adaptive code 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.