Friedhelm Wuppermann

State of the art and trends in speech coding

An introductory review of some basic speech coding techniques covers the most important properties of speech production and hearing, the ubiquitous techniques of quantization and linear prediction, and a recital of the most important measures of coding performance. In the survey that follows, several standardized speech coding systems reflecting the state of the art in speech coding are discussed in terms of coding method, bit rate, performance, complexity and typical application areas. Major future trends are indicated on the basis of expected future standards. The paper, which primarily deals with narrowband speech coding systems, is concluded by a review of the state of affairs and an outline of the future trends in the area of wideband speech coding.

Feasibility Study of 32 Kb/S Wideband Speech and Music Coding With a Low-Delay Filterbank

Wideband speech codecs are now capable of operating at bit-rates around 16 - 32 kb/s. The state-of the-art codecs however, are primarily based on time domain speech-coding techniques and do not cater for music. We investigated a subband coding scheme, in corporating a low-delay IIR filterbank and providing an acceptable quality for speech and music, which exploits the characteristics of the human auditory system. Using the coding schemes, presented here, we developed a 32 kb/s codec with a total delay of 7.8 ms. The study has revealed the limitations of low-delay subband coding at 32 kb/s for wideband speech and music.