Vector quantized MBE with simplified V/UV division at 3.0 kbit/s

A speech coding algorithm for application to the Japan digital cellular half-rate coder has been developed based on the multiband excitation (MBE) algorithm using 3.0 kbit/s. The target performance is at the same level as that of a full-rate coder operating at 6.7 kbit/s. The quantization scheme for the spectral envelope of the MBE coder parameters is described. New features of the scheme include an efficient dimension converter, interframe coding of spectral envelope vectors, and multistage vector quantization with interpolative vector quantization. A simplified model of voiced/unvoiced division and a method of detecting/manipulating background noise have also been devised for MBE analysis. Informal listening tests indicate that, while the quality is slightly lower than that of a full-rate coder, it is nevertheless sufficiently high for digital telephony.