A Rate of 4kbps Vocoder Based on MELP
Yan Ming, Li Zhen Wang, Xu Jiu Xia · Advanced materials research · 2014
A 4kbps vocoder based on MELP is presented in this paper. It uses the parameter encoding and mixed excitation technology to ensure the quality of speech. Through adopting the scalar quantization of Line Spectrum Frequency (LSF), the algorithm reduces the storage and computational complexity. Meanwhile, 4kbps vocoder adds a new frame type-transition frame. The classifier can reduce the U/V decision errors and avoid excessive switching between voiced frame and unvoiced frame. A modified bit allocation table is introduced and the PESQ-MOS and coding time test shows that the synthetic speech quality has been improved and reached the quality of communication.