Variable Rate Voice Vocoder And The Research Of Its Performance

In this paper ,combined with currently voice coding technique ,espically with the fabulosity development of the mixed voice coding and the increasingly utility of the digital signals processor.we investigated the voice coding technique and discussed emphasizedly the technology of variable rate voice coding technology .In this paper ,we briefly introduced the performance of wave coding and vocoder , emphasizedly studied the principle and performance of variable rate vocoder Q4401 ,including the internal construction and pins,Qcelp coder&vocoder,Pcm interface,Cpu interface initialization process ,command formatand so on .we also designed a application circuit ,with the experiment validated itsperformance .In this design ,the Pcm interface chip is TP3057,it was used tofinish A/D transform ,The compress coding was finished by Q4401 ,the initialization and control were accomplished by 8051 singlechip. Then we gave detailedly the hardware and software reality method of the resolvent introduced its hardware development theory ,the reality method of all the circuits, and its theory chart, gave its total software flow chart and the reality method .at last presented the experiment conclusion.When the speech signal coding is at 8kb/s and 9.6kb/s, its understanding and definition are quite satisfaction .completely achieve the common telephone effect.only in the shade of naturalness . When the speech signal coding is at 4kb/s and 4.8kb/s the voice transmission result is as good as that of the ordinary telephones. So Q4401 is a high molar voice vocoder.lt has a very extensive application.