J. Phys. IV France 02 (1992) C1-327-C1-330
CODEUR CELP À COMPLEXITÉ RÉDUITEM. MAUC and G. BAUDOIN
ESIEE Département Signaux et Télécommunications, BP. 99, F-93162 Noisy le Grand cedex, France
CELP coder enables speech coding with good quality at bit rates as low as 4 kps. Several methods have been developed to lessen the computation task. We present a new multistage method that preserves the qualities of the CELP coder with reduced complexity. The basic idea is to find a subset S1 of candidate codewords by approximating the synthetic signal energy. This approximation is obtained by restricting the frequency range and sub-sampling. A full exact search is done on this subset. The procedure can be iterated. Typically, for an initial codebook of 1024 words and a single stage of sub-sampling by a factor equal to q1 = 5, the size of the subset S1 is 70 and the calculation gain is 9. This performance can be improved up to a calculation gain of 13 by introducing several stages of sub-sampling q1 = 5 and q2 = 2.
© EDP Sciences 1992