A Real Time Implementation of a 4800 bps Self Excited Vocoder
The purpose of this paper is to describe a fully developed, real-time 4800 bps speech coding system that was designed for use in a nation-wide mobile satellite communications network . The overall goal was to build an inexpensive speech coder capable of producing “near toll quality” coded speech under bursty channel error conditions at bit error rates of approximately 10−3 BER. A form of the self excited vocoder (SEV) was chosen as the speech coding algorithm . Many of the results presented in this paper concern pragmatic issues such as the robust representation of coder parameters, the error protection, and the constraints imposed by a limited hardware environment. A particularly interesting result of this work was that significant subjective speech quality improvements can be achieved under noisy channel conditions by exploiting known properties of the speech coding parameters.
KeywordsAutocorrelation Toll Acoustics Dmax
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