Pitch estimation using spectral covariance method for low-delay MBE vocoder

The synthesized speech quality of the multiband excitation (MBE) vocoder highly depends on the accuracy of the pitch estimation, and it is uses pitch tracking and spectral analysis-by-synthesis (AbS) procedures to determine the fine pitch with reduced gross pitch errors. However, pitch tracking has limits in practice because it requires a large lookahead. Also, the spectral AbS, if used alone, results in frequent gross pitch errors. So we propose a weighted spectral AbS method which can reduce gross pitch errors without extra-lookahead in comparison with spectral AbS method. The weight in the proposed method is defined by the covariance of excitation spectrum of speech signal to compensate for the gross pitch error. From the comparison of the pitch contours between the spectral AbS and the weighted spectral AbS methods, it is confirmed that the proposed method considerably reduces gross pitch errors rather than spectral AbS method.