OF SPEECH SIGNALS

This paper describes an efficient Code-Excited Linear Predictive (CELP) Coder for bit rates between 6 and 16 kbills, and new effective algorithms for the selection of the excitorion signor Then we propose a chss of binary codebooks having interesting properties in terms of performance, robustness against transmission errors and &xibili@ in the choice of the bit rate. Due to the optimal structure of the coder and to the fast algorithms fur selecting the excitation signal, a real time implementation has been made possible on one 32 bits floating-point digital signal processor. I. INTRODUCTION In the recent years the analysis-by-synthesis procedure has been shown to be an effective method for selecting the optimum excitation in predictive coders. Given a synthesis model consisting of a long term and a short term synthesis filter in cascade, coder structws have been derived for different models of the excitation signal such as the multi-pulse, the regular-pulse and the codeexcitation. This paper describes a new Code-Excited Linear Predictive (CELP) structure with a minimum number of filtering operations. It is shown that, depending on the way transitioos between adjacent blocks are treated, two different methods are derived for finding the excitation signal. Finally fast algorithms are outlined for a special class of codebooks having an inherent robustness against transmission errors.