Global Pulse Replacement Method for Fixed Codebook Search of ACELP Speech CODEC

E.-D. Lee, M.-S. Lee, and D.-Y. Kim (Korea)


speech codec, fixed codebook search, pulse replacement


In this paper, we propose a new fixed codebook search method based on global pulse replacement procedure. The proposed method is composed of two stages. At the first stage, an initial codevector is determined by the pulse positions with maximum absolute values of a "pulse position likelihood-estimate vector" for each of tracks. At the second stage, the pulse replacement procedure is repeatedly performed to enhance the performance of the selected codevector for each procedure. In each pulse replacement procedure, a new pulse is searched for all tracks to avoid the termination of the pulse replacement procedure without finding the optimal codevector. Because the change of search criterion Qk is always maximized in each procedure, the codevector approaches to the optimal solution rapidly as this procedure is repeated. The performance of the proposed fixed codebook search method is measured in terms of segmental SNRseg and P.862 PESQ(Perceptual Evaluation of Speech Quality) using various speech data. Experimental results show that the proposed method considerably reduces the computational complexity compared to conventional ACELP(Algebraic-Code Excited Linear-Prediction) fixed codebook search methods with the slight degradation of speech quality.

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