Improved fast fixed-codebook search method in G.729 encoder
一种改进的G.729标准固定码本快速搜索算法*

The fixed-codebook searching complexity occupies larger proportion of the whole encoding complexity in G.729, which influences the efficiency of the encoding algorithm. The nested-loop search can obtain the optimal codebook vector, but it requires large computational load. Although the traditional pulse replacement search method can reduce the search times greatly, the synthesized speech quality degrades. In order to solve this problem, gave a new approach based on pulse replacement method. In each track of the reordered pulse sequence, searched the codebook partly in accordance with a fixed threshold which related to the loop times. Introduced a double pulse replacement method, which could increase the accuracy of the codebook search with low search load. Tests show that the synthesized speech quality has been greatly improved with the proposed algorithm. Meanwhile, the computational complexity increases slightly compared to the traditional pulse replacement method.