Showing papers on "Cepstrum published in 1979"

Minimum and mixed phase speech analysis-synthesis by adaptive homomorphic deconvolution

Abstract: In this paper short-time homomorphic analysis, the harmonic representation of speech, and the spectral smoothing interpretation of homomorphic deconvolution are explored, resulting in adaptive time-domain windowing and logmagnitude smoothing techniques for improved spectral estimates and enhanced quality of a minimum phase homomorphic vocoder. With an adaptive window alignment scheme a slowly varying (over successive frames) mixed-phase impulse-response estimate is introduced through the complex cepstrum, yielding somewhat higher quality speech than its minimum phase counterpart. For a cepstral window of unity and exact pitch knowledge, this analysis-synthesis scheme acts as an identity system on stationary periodic waveforms. In addition, results of coding the smooth logmagnitude and a comparative study of conventional and sliding chirp-z transform implementation schemes are briefly presented.

A mixed-phase homomorphic vocoder

Abstract: In this paper short-time homomorphic analysis and the harmonic representation of voiced speech are explored with the result of a mixed-phase homomorphic vocoder of somewhat higher quality than its minimum-phase counterpart. A theoretical framework is presented for unwrapped phase estimation from harmonic spectra through smoothing real and imaginary spectral components. The short-time harmonic model leads to pitch adaptive duration and alignment requirements on time-domain windowing. The underlying phase envelope is consequently preserved so that cepstral windowing can he applied. In addition, two alternative vocoders with mixed-phase are considered: the first is based on linear interpolation of complex harmonic peaks, and the second on Lim's spectral root deconvolution scheme.

Multichannel zero-crossing-interval pitch estimation

Abstract: A method for estimating the pitch of voiced speech is presented, based on the following operations: multichannel band-pass filtering; envelope extraction; low-frequency emphasis and DC-level removal; bin analysis of zero-crossing interval times of the yielded waveforms; smoothing of the resulting histogram to give the pitch-period estimator function for a single frame of speech. Since most of these steps are time-serial, a hybrid analog-digital realization suggests itself which makes real-time applications feasible.