BACKWARD-ADAPTIVE PREDICTION CASCADED WITH FORWARD FORMANT AND PITCH FILTERS
Yasheng Qian · 1992
Two kinds of cascaded backward-adaptive predictor (forward formant-backward formant-forward pitch and backward formant-forward pitch) are investigated in this paper. We have analyzed and tested two important parameters for the backward-adaptive formant predictor in these configurations: the update rate of the linear prediction coefficients and the analysis frame length. We have found that if the analysis frame length of the backwardadaptive formant predictor is shorter than the pitch period, the'backward prediction gain degrades rapidly. We have found that the average prediction gain for the slower update rates is close to the fast update one. The slower the update rate, the fewer the computations. Particularly, the backward predictor with slower update rate behaves more like a linear filter. These new results provide a useful platform to explore the applications of backward adaptive prediction to low bit-rate speech coders, in which the backward-adaptive formant predictor is cascaded with a forward pitch predictor or the forward formant-backward formant-forward-adaptive pitch predictor is used [I], [2]. 1.