A real-time vector excited adaptive predictive coder at 9.6 kbit/s

A real-time speech coder which operates at 9.6 kb/s is described. In order to favor the excitation coding, an original structure called the vector excited adaptive predictive coder (VEAPC) is presented where neither the short-term predictor nor the long-term predictor is quantized and transmitted to the receiver. According to scalar ADPCM techniques, this approach uses backward adaptive predictive coding to sequentially update the short-term predictor coefficients. The ADPCM scheme is generalized to the vector case as long as the quantized and transmitted error is a vector. The excitation vector computation leads to an analysis by synthesis procedure where fast CELPC/VXC algorithms are efficiently used