Vector quantization of transform components for speech coding at 1200 bps

A transform-based system is described for vector quantizing speech at and below 1200 b/s. A fixed-dimension codebook is used to quantize low-resolution harmonic components of speech. To reduce the errors of the low-resolution process, transform components, within the baseband and adjacent to the pitch-harmonic components, are also encoded. Speech produced at 1200 b/s using this method was found to be intelligible, particularly for female speakers. This is because the number of harmonic components required for female (high-pitch) speakers is generally smaller than the number required for male (low-pitch) speakers