Joint optimization of excitation parameters in analysis-by-synthesis speech coders having multi-tap long term predictor

Codebook searches in analysis-by-synthesis speech coders typically involve minimization of a perceptually weighted squared error signal. Minimization of the error over multiple codebooks is often done in a sequential manner, resulting in the choice of overall excitation parameters being sub-optimal. In this paper, we propose a joint excitation parameter optimization framework in which the associated complexity is slightly greater than the traditional sequential optimization, but with significant quality improvement. Moreover, the framework allows joint optimization to be easily incorporated into existing pulse codebook systems with little or no impact on the codebook search algorithms. This technique is part of the 3GPP2 source-controlled variable-rate multimode wideband speech codec (VMR-WB) rate set 1 standard.