Variable dimension spectral coding of speech at 2400 bps and below with phonetic classification
Amitava Das, A. Gersho · 2002
The low bit rate enhanced multiband excitation or EMBE speech coder adds several important new features including phonetic classification and a naval spectral quantization technique called variable dimension vector quantization (VDVQ) to the basic multiband excitation vocoder. Phonetic classification allows the adaptation of spectral modeling and quantization to the local acoustic-phonetic character of the speech signal, enhancing quality and robustness. The VDVQ scheme quantizes the log-spectrum with relatively few bits while preserving perceptually important features. Both the fixed rate (2.4 kb/s) and the variable rate (1.44 kb/s average) implementations of EMBE deliver speech quality comparable to the 4.8 kb/s Federal Standard 1016 CELP coder and the 4.15 kb/s Inmarsat-M standard IMBE coder.