Adaptive two-direction pitch tracking algorithm for MBE vocoder

In this paper, an adaptive two-direction pitch tracking algorithm for multiband excitation (MBE) vocoder is proposed. Instead of the multiple constraint equations, a difference inequation is constructed. The adaptive adjusting model of the difference threshold is established by utilizing the information including voicing decisions, pitch estimate, and multiple pitch error identification of the previous frame. To identify the multiple pitch error, an approximate corrective matching error measure from the spectral analysis-bysynthesis (AbS) method is utilized. Because the difference threshold can be adjusted adaptively, the proposed algorithm can efficiently avoid continuous multiple and continuous submultiple pitch errors. Moreover, the proposed algorithm almost needs no additional time complexity and computational complexity, so it can easily be implemented in actual systems. From the experimental results, it is justified that, the proposed algorithm outperforms the conventional algorithm, improving the accuracy of the pitch estimation and displaying excellent robustness to different speakers and white Gaussian noise conditions¹.