Algorithm Improving the CELP Coder for Real-Time Communication

Abstract

Generally, the code excited linear predictive (CELP) coding is known as one of the best algorithms for bit rate between 4 kbps and 16 kbps. Recently, the algebraic CELP (ACELP) algorithm has been widely adopted in standard speech coders such as G.729 and Adaptive multi rate (AMR) and AMR Wide Band (AMR-WB).In order to improve the speech quality based on CELP algorithm, harmonic Pitch pre-emphasis is employed on the impulses and a new codebook search method is proposed. Pitch pre-emphasis is applied in the analysis-by-synthesis loop of the analyzer, so the harmonic structure is strengthened. The new codebook search method reduces the computations considerably at the expense of a slight degradation of speech quality. The experiment result shows that the speech quality of integrated speech coding algorithm offers almost the same quality as G.729 while takes less search space.