Enhanced waveform interpolative coding at 4 kbps

Abstract

This paper presents an enhanced waveform interpolative (EWI) speech coder at 4 kbps. The system incorporates novel features such as analysis-by-synthesis (AbS) vector-quantization (VQ) of the dispersion-phase, AbS optimization of the slowly evolving waveform (SEW), a special pitch search for transitions, and switched-predictive analysis-by-synthesis gain VQ. Subjective quality tests indicate that it exceeds that of MPEG-4 at 4 kbps and of G.723.1 at 5.3 kbps, and it is slightly better than that of G.723.1 at 6.3 kbps.