5th International Conference on Spoken Language Processing

Sydney, Australia
November 30 - December 4, 1998

ITU-T G.729 Extension At 6.4 kbps

E. Ekudden (1), R. Hagen (1), B. Johansson (1), S. Hayashi (2), A. Kataoka (2), S. Kurihara (2)

(1) Audio and Visual Technology Research, Ericsson Radio Systems AB, Sweden
(2) NTT Human Interface Labs, Japan

This paper describes the 6.4 kbit/s CS-ACELP coder being standardized as annex D to ITU-T G.729. The coder is based on the same building blocks as the 8 kbit/s G.729 to facilitate low complexity extensions to G.729 in terms of additional memory usage. It is fully switchable with the 8 kbit/s coder and provides additional flexibility to existing and emerging G.729 applications. The fixed codebook is a 2-pulse algebraic codebook. The adaptive codebook quantization has been changed and a new conjugate structure gain codebook is used. In order to compensate for the sparser algebraic codebook, an adaptive post-processing technique is used to enhance the quality for unvoiced speech and background noise sounds. Subjective tests have indicated that the coder has a performance close to that of G.729, and equivalent to that of G.723.1 at 6.3 kbit/s for speech.

Full Paper

Bibliographic reference.  Ekudden, E. / Hagen, R. / Johansson, B. / Hayashi, S. / Kataoka, A. / Kurihara, S. (1998): "ITU-t g.729 extension at 6.4 kbps", In ICSLP-1998, paper 0808.