Study on Fast Fixed-Codebook Search Algorithm in G.729 Speech Coding

G.729 is called conjugate structured-algebraic code excited linear prediction (CS-ACELP), its fixed-codebook adopts algebraic- codebook. The algebraic structure of the codebook allows for a fast search procedure, but it still requires large computational load using the nested-loop search method. The focused search used in G.729 and the depth-first tree search used in G.729a can reduce the searching complexity efficiently. However it still occupies a larger proportion of whole encoding complexity. In this paper, we study various methods and propose a fast Codebook Search method, it can largely reduce the complexity, and speech still maintain at almost the same quality.