Adaptive Postfilter used in Waveform Interpolation Speech Coding
Shenghui Zhao · Signal Processing · 2007
This paper combines adaptive postfilter technique with 3kbps characteristic waveform interpolation (CWI) algorithm. The decoder is in tandem with short-term postfilter,spectral tilt compensation,long-term postfilter and automatic gain control.The param- eters of postfilter are set properly by theory analysis and subjective listening test and are varied adaptively with the speech frame feature. The coding speech is processed and keeps the energy by the postfiter with attenuation between formant peaks and pitch harmonic peaks but without a spectral tilt.The experiment results show that after postfiltering the quantization noise of the 3kbps CWI synthesized speech is obviously reduced and the speech quality is improved.