Low bit rate speech coding
Date
2006-03
Authors
Kritzinger, Carl
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
Despite enormous advances in digital communication, the voice is still the primary tool
with which people exchange ideas. However, uncompressed digital speech tends to require
prohibitively high data rates (upward of 64kbps), making it impractical for many applications.
Speech coding is the process of reducing the data rate of digital voice to manageable
levels. Parametric speech coders or vocoders utilise a-priori information about the mechanism
by which speech is produced in order to achieve extremely efficient compression of
speech signals (as low as 1 kbps).
The greater part of this thesis comprises an investigation into parametric speech coding.
This consisted of a review of the mathematical and heuristic tools used in parametric
speech coding, as well as the implementation of an accepted standard algorithm for parametric
voice coding.
In order to examine avenues of improvement for the existing vocoders, we examined
some of the mathematical structure underlying parametric speech coding. Following on
from this, we developed a novel approach to parametric speech coding which obtained
promising results under both objective and subjective evaluation.
An additional contribution by this thesis was the comparative subjective evaluation of
the effect of parametric speech coding on English and Xhosa speech. We investigated the
performance of two different encoding algorithms on the two languages.
Description
Thesis (MScIng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006.
Keywords
Dissertations -- Electronic engineering, Theses -- Electronic engineering, Speech processing systems, Coding theory