Amr Vocoder Research And Development

With the continuously increasing of the demand of high quality of speech in telecommunication field, the technology of speech coding has been rapidly developed recently. AMR is the speech coding standardization of the 3G Mobile Communication submitted by 3GPP.lt achieves multi-rate speech coding and decoding, supports nonvoice restraining and comfort noise generation. It performs as the function of gateway in MSC, and it ensures the net of 3G mobile communication interworking with the existing net of PSTN and ISDN. So, The researching and developing of AMR is of great practical value.First the paper studies the algorithms of AMR speech coder. The AMR speech coder consists of the multi-rate speech coder, a source controlled rate scheme, and an error concealment mechanism. Based on the TMS320C6000 produced by Tl, we implement it. And its quality of the synthetic speech achieves the criterion prescribed by ITU, and it passes the test sequences strictly.The paper also introduces some general methods in pitch detected, and distills the module in the arithmetic of AMR coder for research. It also brings forward a simple and effective method, which adopts autocorrelation of time domain combining with dynamic smooth of pitch period. The method eliminates the errors of most half frequency and double, and reaches satisfactory effect.