Research on 4~6bit Pitch Quantization Algorithm in Low-Rate WI Coder

Pitch parameter is often quantized uniformly with no distortion using 7 bit in speech coding applications. As pitch changes slowly in voiced segments, in order to remove the correlation between two consecutive pitch more effectively, based on Eriksson and Kangs 4 bit pitch quantization algorithm, this paper implements a pitch quantization algorithm using 4~6 bit for Chinese. This algorithm has a small complexity and no codebook is needed. This pitch quantization algorithm is applied to WI model and WI coder, the results from the subjective A/B listening test indicate that this algorithm not only quantized pitch effectively, but also kept the quality of synthesized speech with no obvious hearing distortion. Therefore, it satisfies the accuracy of the quantized pitch of WI coder completely.