2.1. Introduction

35 years ago, speech coding was a domain which was only just emerging. Today, it has become a scientific research topic and an industrial engineering sector of the utmost importance. The main factor for this fabulous growth lies in the recent development of modern telecommunications systems, which has brought about a boom in the deployment of digital signal transmission in many applications. As digital systems outperform analog technologies in many respects, digital transmission and storage of speech signals have become an absolute necessity, inducing incredible developments in the area of speech coding, over recent years.

Even though the deployment of digital networks now enables the transmission of sounds, images and all sorts of data, voice communication i.e., the telephone remains the most essential means of communication between people. This is why the development of telecommunications systems has, for its primary goal, to meet the demands in the area of telephone communication, as the recent development of mobile phones illustrates. In this sector, speech coding technologies have played a key role.

Speech coding is nothing more than a set of techniques for compressing i.e. reducing the bit-rate of the speech signal, while being able to reconstruct it with a sufficiently high quality, so as to efficiently use transmission channels and/or to lessen the memory required to store the compressed speech. However, we might wonder whether it is still relevant nowadays to compress speech, given that very high bit-rate digital...