Bandwidth Extension of Narrowband Speech using Soft-decision Vector Quantization

Vector quantization (VQ) is normally used to extend the spectral envelope of narrowband speech into that of the wideband speech. This paper proposes a novel soft-decision approach for VQ and it can be shown that the result is better than the direct method as well as the interpolated VQ method. The resulting cepstral wideband coefficients are obtained using a weighted combination of several set of coefficients in the codebook. The weighting factors are determined by an inverse-distance formula