Variable rate code excited linear predictive coding of speech

Pao Yue-kong Library Electronic Theses Database

Variable rate code excited linear predictive coding of speech

 

Author: Yuen, Siu-keung
Title: Variable rate code excited linear predictive coding of speech
Degree: M.Sc.
Year: 1997
Subject: Speech processing systems
Coding theory
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Pages: vi, 97 leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1398640
URI: http://theses.lib.polyu.edu.hk/handle/200/2820
Abstract: This thesis presents a variable rate Code-Excited Linear Predictive (CELP) [9] speech coding which can be applied to communication and consumer products. The coder can run at either 7.35 kbps for voiced speech or 2.1 kbps for unvoiced speech under an adaptive rate selection algorithm based on QCELP [4] concept. The objective of this thesis is to simulate the variable rate CELP speech coder in software, and evaluate the rate determination and speech quality using objective measures. The CELP coding algorithm is presented in detail with balanced theory and practical consideration. Some variable rate coding algorithms such as VAD, QCELP, and phonetic classifications are outlined. Speech evaluation techniques such as objective and subjective measures are also described. A software based variable rate CELP coder is developed for simulation. With quantization, the coder achieves on average 8.9 dB segmental SNR at an average bit rate of 6.2 kbps. The effect of speakers, input level variations, and input signal to noise ratio variation are also evaluated.

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