Low-delay speech coding at 16 kbs and below
M. Foodeei · eScholarship@McGill (McGill) · 1991
Development of network quality speech coders at 16 kb/s and below is an active research area. This thesis focuses on the study of low-delay Code Excited Linear Predictive (CELP) and tree coders. A 16 kb/s stochastic tree coder based on the (M.L.) search algorithm suggested by lyengar and Kabal and a low-delay CELP coder proposed by AT&T (CCITT 16 kb/s standardization candidate) are examined. The first goal is to compare and study the performance of the two coders. Second objective is to analyze the particular characteristics which make the two coders different from one another. The final goal is the improvement of the performance of the coders, particularly with a view of bringing down the bit rate below 16 kb/s. When compared under similar conditions, the two coders showed comparable performance at 16 kb/s. Issues in backward adaptive linear prediction analysis for both near and far sample redundancy removal such as analysis methods, windowing, ill-conditioning, quantization noise effects and computational complexities are studied.