A fast-search algorithm for the predictive split VQ of LPC parameters

A fast-search method is introduced to reduce the searching range of a codebook using the ordering property of LSF parameters. We apply the proposed fast-search method to the G.723.1 coder with the predictive split VQ structure. Simulation results indicate that using this fast-search method, the average searching range of the codebook can be reduced by 20.1% without degradation of the spectral distortion (SD) and additional increases of memories. The reduction of 20.1% in the average searching range results in the decrease of 19.1%, 20.1%, 19.4%, and 12.2% in the number of additions, subtractions, multiplies, and comparisons, respectively.