Accession Number : ADA114068

Title :   Development of a Good-Quality Speech Coder for Transmission Over Noisy Channels at 2.4 kb/s.

Descriptive Note : Final rept. Aug 80-Mar 82,

Corporate Author : BOLT BERANEK AND NEWMAN INC CAMBRIDGE MA

Personal Author(s) : Viswanathan,V R ; Berouti,M ; Higgins,A ; Russell,W

PDF Url : ADA114068

Report Date : Mar 1982

Pagination or Media Count : 192

Abstract : This report describes the development, study, and experimental results of a 2.4 kb/s speech coder called harmonic deviations (HDV) vocoder, which transmits good-quality speech over noisy channels with bit-error rates of up to 1%. The HDV coder is based on the linear predictive coding (LPC) vocoder, and it transmits additional information over and above the data transmitted by the LPC vocoder, in the form of deviations between the speech spectrum and the LPC all-pole model spectrum at a selected set of frequencies. At the receiver, the spectral deviations are used to generate the excitation signal for the all-pole synthesis filter. The report describes and compares several methods for extracting the spectral deviations from the speech signal and for encoding them. To limit the bit-rate of the HDV coder to 2.4 kb/s the report discusses several methods including orthogonal transformation and minimum-mean-square-error scalar quantization of log area ratios, two-stage vector-scalar quantization, and variable frame rate transmission. The report also presents the results of speech-quality optimization of the HDV coder at 2.4 kb/s.

Descriptors :   *Speech transmission, *Vocoders, *Noise reduction, Noise(Radio), Channels, Quality, Speech, Spectrum analysis, Data rate, Comparison, Transformations, Orthogonality, Optimization, Degradation, Errors, Algorithms, Extraction, Narrowband

Subject Categories : Cybernetics
      Voice Communications

Distribution Statement : APPROVED FOR PUBLIC RELEASE