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A high quality harmonic+noise speech coder is presented. This coder operates in either the steady mode or the transient mode. An efficient phase coding technique based on polynomial fitting is proposed. In this technique, the frequency deviations that are used to minimize the phase prediction errors are modeled by a 6/sup th/-order polynomial. The polynomial coefficients are quantized in closed-loop by a split vector quantizer. For the transient speech, the unvoiced part is modeled by an 8/sup th/-order all-pole model while the voiced part is modeled by the low-frequency harmonic components. The transitional behavior is characterized by the onset time and growth rate of each harmonic component. An analysis-by-synthesis procedure is proposed to determine the onset times and growth rates in the time domain. The proposed coder retains the temporal events of the speech signal and produces high quality speech at 2.4 kbps.
Yu et al. (Thu,) studied this question.