Implementation of modified regular-pulse excited linear predictive codec on TMS320C25

A modified regular-pulse-excited speech coding algorithm with long-term prediction (MRPE-LTP) is proposed. This scheme has a much smaller computational load than the standard algorithm adopted by CEPT Group Special Mobile without compromising the synthetic speech quality. This advantage is attributed to the novel way of determining the initial phase. A varying-threshold clustering vector quantization with a tree search method is given to quantize linear predictive coding (LPC) coefficients. Due to the optimal structure of the MRPE codec and the simple approach of determining the excitation parameters, implementation has been made possible on one TMS320C25 digital signal processor