Second European Conference on Speech Communication and Technology

Genova, Italy
September 24-26, 1991


Low Bit Rate Speech Coding Using CELP With Adaptive Excitation Codebook

U. Kipper, Herbert Reininger, Dietrich Wolf

Institut für Angewandte Physik der Universität Frankfurt a. M. , Frankfurt am Main, Germany

In this paper we propose a method denoted as ACELP for improving the speech quality of a Code-Excited-Linear-Predictive (CELP) codec at low bit rates by adaptation of the excitation codebook. The adaptive codebook consists of a set of basic excitation vectors which are adapted to an analysis speech frame by calculating optimum amplitude values. The amplitudes are quantized and encoded at a very low bit rate using a gain shape vector quantizer. The results of simulation experiments show that the mean squared error of CELP with an adaptive codebook is substantially lower than that of CELP with a fixed stochastic codebook. In informal listening tests the quality of the speech processed by the adaptive CELP scheme offered a reduced roughness and was less speaker dependent as with a conventionel CELP scheme.

Full Paper

Bibliographic reference.  Kipper, U. / Reininger, Herbert / Wolf, Dietrich (1991): "Low bit rate speech coding using CELP with adaptive excitation codebook", In EUROSPEECH-1991, 893-896.