Hierarchical Vector Quantization: Theory and Application to Speech Coding

Authors:

Erdmann, C.

Editors:

Vary, P.

Ph. D. Dissertation

 

School:

IND, RWTH Aachen

Adress:

Templergraben 55, 52056 Aachen

Series:

Aachener Beiträge zu Digitalen Nachrichtensystemen (ABDN)

Number:

19

Date:

Jul. 2005

ISBN:

3-861-30646-8

Language:

English

Abstract

Digital speech communication in increasingly heterogeneous communication networks requires flexible speech coding algorithms. In Voice-over-IP (VoIP), for example, significant parameters such as the instantaneous bit rate, the delay or the packet loss rate may hwavily vary over time. Hierarchical speech coding algorithms are particularly well suited to accommodate to these changing conditions, as bit rate reductions can be effected at any point along the communication network without transmiitting any additional signaling information.
The objective of this thesis is hierarchical vector quantization (HVQ) and its application to speech coding. The aim is to increase the flexibility of variable bit rate (VBR) speech coding algrithms while maintaining the coding efficieny in a rate-distortion sense. A general HVQ scheme is developed that comprises well-known generic approaches to hierarchical coding such as multistage VQ and multiresolution VQ. The formulation of a general approach to hierarchical coding within the VQ framework allows us to apply the theoretical tools provided by raate-distortion theory and high-rate theory in order to analyze the performance penalty that those generic hierarchical coding systems suffer compared to non-hierarchical coding systems. Based on the insight gained freom this theoretical performance analysis, new bit rate efficient algorithms for hierarchical speech coding are developed.
The main results of this work are:
* formulation of a general approach to vector quantization (VQ) based hierarchical coding;
* information theoretic analysis on the performance of hierarchical coding systems;
* new theoretic upper bounds on the performance penalty that generic herarchical coding systems suffer compared to non-hierarchical coding systems;
* new algorithms for bit rate efficient hierarchical coding of speech.
Compared to conventional, non-hierarchical algorithms for VBR speech coding, the proposed algorithms provide enhanced flexibility in terms of bit rate scalability

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