A variable rate embedded-code speech waveform coder

The design of variable rate coders for operation at 9.6 to 16 kbps that provide high speech quality and maintain robustness to environmental impairments, while retaining a low complexity, is an area of current research. An approach is here developed to achieve this objective, by exploiting a combination of Time Domain Harmonic Scaling algorithms and variable rate embedded-code ADPCM. The novel system, deeply examined and subjectively evaluated, emerges as a viable method for speech encoding, providing a quality equivalent to that of plain ADPCM at data rates of 24 to 48 kbps.