Piecewise linear predictive coding (PLPC)

A great deal of current research in the area of narrowband digital speech compression makes use of the Linear Prediction Coding (LPC) algorithm to extract the vocal track spectrum. This paper describes a technique that splits the spectrum into two equal halves and performs a piecewise LPC approximation to each half. By taking advantage of the classical benefits of piecewise approximation, the fidelity is expected to be higher than standard LPC. In addition, by making use of under-sampling and spectrum folding, computational requirements are reduced by about 40%. PLPC has been implemented in real time on the CSP-30 computer at the Speech Research and Development Facility of the Communications Security Engineering Office (DCW) at ESD.