A 600bps Vocoder Algorithm Based on MELP

In order to meet the bandwidth requirements of low-bit-rate speech communication, there is an improvement of standard Mixed Excitation Linear Prediction (MELP) encoder and a 600bps MELP vocoder algorithm with higher quality is proposed. The algorithm forms a super frame by using 5 sub-frames. Joint quantization was carried out to remove redundancy information between intra-frames and inter-frames. We use the method of predictive split vector quantization to quantize the Line Spectral Frequency (LSF) parameters and the other parameters are jointly quantized. Compared to standard 2.4kbps MELP vocoder, the Mean Opinion Score(MOS) of the synthetic speech which is synthesized by the vocoder using the proposed algorithm is 2.54, and the synthetic speech quality is good.