Adapting waveform interpolation (with pitch-spaced subbands) for quantisation

Adaptation of the waveform interpolation (WI) paradigm to allow waveform coding of the speech signals was reported by Kleijn et al. (see Proc. 5^th Int. Conf. Spoken Language Processing, Sydney, Australia, Dec. 1998). However, since the signal is time-warped to a constant pitch, processing the surface derived from the new technique is extremely dependent on having an accurate pitch track. In order to facilitate vector quantisation techniques, it is necessary to manipulate the pitch track to ensure phase-alignment of critically sampled pitch periods. In addition, pitch cycles following unvoiced segments must also carry the same phase offset. The adjusted pitch track is used to facilitate a re-warping of the residual signal. The effects of warping and pitch inaccuracies on the transformed result of the warped periods are also discussed