Study and real-time implementation of an efficient 9.6 Kbit/s MultiPulse speech coder

This paper deals with the design and real-time implementation of a good quality 9.6 Kbit/s MultiPulse speech coder on a single low-cost digital signal processor, the TMS320C25 by Texas Instruments. The coder is based on a new confined pulse search method which guarantees a good trade-off between performance and complexity. From a study of pulse distribution it was possible to establish an efficient bit allocation for differential position coding and approximate the excitation frame with quite a high number of pulses achieving a good perceptive quality. The paper also deals with the CPU requirements of the coding procedures implemented and the results of a series of objective and subjective tests which show that the proposed version of the MultiPulse coder provides a speech quality which is better than that of the current 13 Kbit/s GSM speech coding standard.