Low-cost highly-efficient speech coding is important for personal multimedia communications. In this paper we propose a new low-complexity speech coding method called "Dual-Pulse CS-CELP (DP-CS-CELP)" at 7.8 kbit/s. This method is based on ITU-T G.729. To reduce the complexity, we applied a new excitation model to the random code vectors and simplified the LPC coding, adaptive codebook search, perceptual weighting, and the other structures. The number of operations for this encoder is 3.80 MOPS, which achieves real-time speech coding and decoding on personal computers. Although the efficiency of this coder is a little lower than that of G.729, the MOS listening test showed that the subjective quality was equivalent to or a little better than that of G.726 (32-kbit/s ADPCM).
['Hitoshi Ohmuro', 'Jotaro Ikedo', 'Takehiro Moriya', 'Akitoshi Kataoka', 'Shinji Hayashi', 'Kazunori Mano']
Dual-Pulse CS-CELP: a toll-quality low-complexity speech coder at 7.8 kbit/s