Dispersion phase vector quantization for enhancement of waveform interpolative coder

This paper presents an efficient analysis-by-synthesis vector quantizer for the dispersion phase of the excitation signal which was used to enhance a waveforminterpolative coder. The scheme can be used to enhance other harmonic coders, such as the sinusoidal-transform coder and the multiband-excitation coder. The scheme incorporates perceptual weighting, and does not require any phase unwarping. The proposed quantizer achieves a segmental signal-to-noise ratio of up to 14dB for as low as 6-bit quantization. Subjective testing shows improvement in synthesized speech quality using the quantized phase over a male speaker extracted phase. The improvement was larger for female speakers.