Speech Compression and Evaluation
Final rept. Dec 1974-Dec 1977
BOLT BERANEK AND NEWMAN INC CAMBRIDGE MA
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This report describes our work in the past three years on data compression and quality evaluation of digital speech. We developed and implemented linear predictive coding LPC techniques with the overall objective of digitally transmitting high quality speech at the lowest possible average data rates over packet-switched communication media. Major techniques reported include covariance lattice method of linear prediction analysis, adaptive lattice methods, linear predictive spectral warping, improved quantization of LPC parameters, variable frame rate transmission of LPC parameters based on a functional perceptual model of speech, and a mixed-source model for LPC synthesizer to produce more natural-sounding speech. Also, we developed a reliable method for measuring subjective speech quality. This method was employed to formally demonstrate the quality improvements provided by our speech analysissynthesis techniques as well as for studying speech quality as a function of LPC parameters. As subjective procedures are generally expensive and time-consuming, we developed and tested several objective procedures for speech quality evaluation. The results from these objective procedures were found to be highly correlated to the corresponding subjective quality judgments. Another highlight of our work is the development of a speech processing computer facility with the ultimate goal of transmitting narrowband speech in real time over the ARPA Network.
- Non-Radio Communications