An adaptive short-term postfilter based on pseudo-cepstral representation of line spectral frequencies

We propose an adaptive short-term postfilter for speech coders by incorporating the properties of the pseudo-cepstrum [IEEE Trans. Speech Audio Process. 8 (2) (2000) 195]. Since the proposed postfilter implicitly has a characteristic of tilt compensation, it does not require an additional tilt compensation filter as conventional techniques. We derive a relationship between the postfilter parameters so that the postfilter has a minimum phase distortion, which helps simplify the tuning procedure for the parameters. We also show that the postfilter can be successfully implemented with a lower order. By applying this postfilter to several international speech coding standards, we reduce the complexity while obtaining a comparable performance to conventional approaches.