Enhanced analysis-by-synthesis waveform interpolative coding at 4 KBPS

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