A Real Time Implementation of a 4800 bps Self Excited Vocoder

  • Stephen J. A. McGrath
  • Richard C. Rose
  • Thomas P. BarnwellIII
Part of the The Springer International Series in Engineering and Computer Science book series (SECS, volume 114)

Abstract

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 [1]. 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 [2]. 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.

Keywords

Autocorrelation Toll Acoustics Dmax 

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References

  1. [1]
    S. J. A. McGrath and T. P. Barnwell III. Development, design, fabrication, and evaluation of a breadboard speech compression system at 4800 bps — phase four final report. Technical report, School of Electrical Engineering, Georgia Institute of Technology, 1988.Google Scholar
  2. [2]
    R. C. Rose and T. P. Barnwell III. The self excited vocoder-an alternate approach to toll quality at 4800 bps. Proc. Inter. Conf. on Acoustics, Speech, and Signal Proc., pages 453–456, April 1986.Google Scholar
  3. [3]
    R. C. Rose. The Design and Performance of an Analysis-by-Synthesis Class of Predictive Speech Coders. PhD thesis, Georgia Institute of Technology, Atlanta, Ga., 1988.Google Scholar
  4. [4]
    B. S. Atal and J. R. Remde. A new model of LPC excitation for producing natural sounding speech at low bit rates. Proc. Inter. Conf. on Acoustics, Speech, and Signal Proc., pages 614–617, April 1982.Google Scholar
  5. [5]
    M. R. Schroeder and B. S. Atal. Code excited linear prediction: High quality speech at very low bit rates. Proc. Inter. Conf. on Acoustics, Speech, and Signal Proc., pages 937–940, April 1985.Google Scholar
  6. [6]
    P. Kroon, E. F. Deprettere, and R. J. Sluyter. Regular-pulse excitation: A novel approach to effective and efficient multipulse coding of speech. IEEE Trans. Acoust., Speech, and Sig. Processing, ASSP-34(5):1054–1063, Oct. 1986.CrossRefGoogle Scholar
  7. [7]
    R. C. Rose, T. P. Barnwell III, and S. McGrath. The design and performance of a real-time self excited vocoder. Proc. Mobile Satellite Communications Conference, May 1988.Google Scholar
  8. [8]
    Joel R. Crosmer. Very Low Bit Rate Speech Coding Using the Line Spectrum Pair Transformation of the LPC Coefficients. PhD thesis, Georgia Institute of Technology, June 1985.Google Scholar
  9. [9]
    T. P. Barnwell III. Recursive windowing for generating autocorrelation coefficients for LPC analysis. IEEE Trans. Acoust., Speech, and Sig. Processing, ASSP-29(5):1062–1066, Oct. 1981.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1991

Authors and Affiliations

  • Stephen J. A. McGrath
    • 1
  • Richard C. Rose
    • 2
  • Thomas P. BarnwellIII
    • 1
  1. 1.School of Electrical EngineeringGeorgia Institute of TechnologyAtlantaUSA
  2. 2.MIT Lincoln LaboratoriesLexingtonUSA

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