Daniel Mauduit

A 4800 bps voice excited predictive coder (VEPC) based on improved baseband/Sub-bands filters

A Voice Excited Predictive Coding architecture (VEPC) has been recently proposed allowing to compress digital speech at bit rates of 9600/7200 bps with a telephone quality. In order to decrease the bit rate down to 4800 bps, while preserving a same level of quality, several improvements of the processing blocks have been considered: · an adaptive pre-emphasis of the predictor coefficients, · a five to one decimation of the residual signal to reduce the residual baseband to 800 Hz, · a parallel implementation of the sub-bands splitting-reconstruction. This paper deals with the improvements as well as the implementation aspects. Taped results will be played at the conference.

Real time signal processing software for multiplierless microprocessors

Different concepts to generate real time efficient signal processing software for microprocessors without hardwired multiplier have been recently introduced for application to digital signal filtering with fixed coefficients [1]. These approaches are extended to the generation of time efficient code for the computation of signal prediction (or filter with variable coefficients), autocorrelation (or correlation) as required in the area of digital speech processing. The reference processor, which has been specifically designed to allow both dynamic on-line code generation, is composed of a 16-bit ALU built around the Am2900 4-bit slice general purpose micro-processor which performs with a same level of accuracy as any general purpose floating point scientific program for the considered examples.