Speech coding at 4 and 8 kb/s based on iterative sequential CELP optimization

The authors introduce sequential optimization of the parameters of a 4- and 8-kb/s codebook excited linear predictive (CELP) coder. The short-term filter, the long-term adaptive codebook, and the excitation codebook parameters were sequentially optimized to minimize the resulting weighted mean square error. The sequential optimization procedure considers at each subframe the most probable choice of excitation parameters for the next subframe. A simulated annealing algorithm was used to optimize the short-term filter to minimize weighted mean-squared error. The closed-loop algorithm is iterative in nature, and iterations are conducted over the adaptive codebook, the codebook excitation and the short-term filter in an attempt to jointly optimize the corresponding parameters