Design and implementation of a programmable bit-rate multipulse excited LPC vocoder for digital cellular radio applications

Abstract

We present the algorithm for design of an analysis-by-synthesis based multi-pulse excited/long-term prediction type LPC speech coder and discuss its real-time implementation using the state-of-art ADSP 2101 digital signal processor. The important features of this speech coder are attributed to the use of (i) an efficient search algorithm for computing the pulse locations and amplitudes involved, (ii) sigma-delta based 16-bit codec-filter VLSI chip: AD 28msp 0.2 acting as front and back ends (iii) perceptual weighting filter and (iv) an efficient output post-processing filter. A detailed objective and subjective evaluation of the speech coder is carried out.