IP Telephony: Packet-based Multimedia Communications Systems

Chapter 5. Voice coding

Introduction

Transmitted bandwidth, sampling and quantization

The analogue to digital conversion is a process to represent an infinite precision signal originally in an analogue form, such as an electrical signal produced by a microphone, by a finite set of numbers at a fixed sample rate. This simple procedure, is mandatory to allow computer-based analysis, bitrate reduction, digital storage and transmission of any speech or sound signal. It has important factors that influence the quality of digitized speech:^{2, 21, 22}

• the rate of sampling

• the total amount of different representatives (number of bits) used to encode the signal.

The sampling rate is directly related to the frequency bandwidth of the signal that needs to be transmitted ...