Design and performance of robust embedded ADPCM coder

An embedded adaptive DPCM (EADPCM) speech coder is described which allows bit rate reductions to be achieved by progressive deletion of bits from output codewords. Optimised step size multipliers are given for a robust implementation using an improved algorithm for adaptive quantisation. Simulation shows that a graceful reduction in speech quality with bit rate is achieved in the range 16–48 kbit/s.