A high quality CELP for AUDETEL NICAM and Teletext applications

A commentary channel, describing the main features of a scene on the television screen, using some spare capacity in the NICAM and Teletext transmission systems, will be introduced in Europe for the benefit of partially sighted people who are mainly elderly. The speech coding algorithm for this application has to cope with a number of constraints. The authors describe several speech coding standards which cover a wide range of bit rates with varying complexity and quality. The best quality speech coder is based on code excited linear prediction (CELP), in which the excitation is modelled as the sum of pitch modelling and a random stochastic process. A derivative of this coder has been selected to be optimized for the AUDETEL application. A detailed description of the speech coding algorithm together with its real-time implementation and hardware details are explained