SPECTRAL PHASE MODELING OF THE PROTOTYPE WAVEFORM COMPONENTS FOR A FREQUENCY DOMAIN INTERPOLATIVE SPEECH CODEC SYSTEM

摘要

Encoding of prototype waveform (PW) components applicable to GeoMobile and Telephony Earth Station (TES), provides improved voice quality, enabling a dual-channel mode of operation which permits more users to communicate over the same physical channel. A PW gain (34) is quantized using a vector quantizer (VQ) having a codebook representative of steady-state and transient vectors for tracking abrupt speech level variations during onsets and other non-stationary events, while maintaining accuracy during stationary conditions. The rapidly evolving waveform (REW) and slowly evolving waveform (SEW) component vectors, (42) and (40), respectively, are converted to magnitude-phase. A voicing measure, characterizing the degree of signal periodicity, and an interpolated pitch countour, based on estimated open loop pitch, are determined for each speech frame. Only the SEW and REW spectral magnitude information, the voicing measure, and pitch frequency countour are transmitted. The SEW phase component is reconstructed at the decoder from this information. The REW phase component is reconstructed at the decoder from the reconstructed SEW component, the voicing measure, REW magnitudes, and the pitch frequency contour information.