Implementation of a RPE codec on a commercial DSP

The regular pulse excitation technique for speech coding at low bit rates provides good speech quality but involves a heavy computational effort. A novel method of reduced complexity is described which permits an efficient implementation on on a commercial DSP (digital signal processor) in terms of computation time and code compactness. The algorithm uses vector quantization for a vocal tract all-pole model. A complete implementation of an 8 kb/s codec working in full-duplex mode is performed on the Motorola mathematical μP DSP56000. According to many informal listening tests, the speech quality at 8-kb/s is very close to that achieved at 64 kb/s using standard pulse-code modulation