DIGITAL VOICE CODER WITH IMPROVED VECTOR EXCITATION SOURCE

摘要

PROBLEM TO BE SOLVED: To provide an improved technology for excitation vector generation and the retrieval thereof for application to a voice coder for code excitation linearity prediction(CELP) using a code book made of excitation code vectors. SOLUTION: A set of M-base vectors Vm (n) is used together with excitation signal code words (i), thereby generating the code book of excitation vectors Ui (n). The whole of the code book made of 2M excitable vectors is efficiently retrieved, using the vector sum generation technology together with the M-base vectors. As a result, each set of the 2M code vectors themselves does not need to be generated and evaluated as different from the conventional case. Furthermore, only the M-base vectors need to be saved in a memory, and the storage of the whole of the 2M code vectors is not required.