| 摘要 |
<p>Encoding of prototype waveform components applicable to Geomobile and telephony Earth Station (TES) providing improved voice quality enabling a dual-channel mode of operation which permits more users to communicate over the same physical channel. A prototype (PW) gain (34) is vector quantized uzing a vector quantizer (VQ) that explicitly populates the codebook by representative steady state and transient vectors of PW gain for tracking the abrupt variations in speech levels during onsets and other non-stationary events, while maintaining the accuracy of the speech level during stationary conditions. The rapidly evolving waveform (REW) (42) and slowly evolving waveform (SEW) (40) component vectors are converted to magnitude-phase. The variable dimension SEW magnitude vector is quantized using hierarchical approach, i.e., a fixed dimension SEW mean vector computed by a sub-band averaging of SEW magnitude spectrum, and only the REW magnitude is explicitly coded. The REW phase vector is regenerated at the decoder based on the received REW gain vector and the voicing measure, which determines a weighted mixture of SEW component and a random noise that is passed through a high pass filter to generate the REW component. The high pass filter poles are adjusted based on the voicing measure to control the REW component characteristics. At the ouput filter, the magnitude of the REW component is scaled to match the received REW magnitude vector.</p> |
