Importance

Loading Importance Indicators...

Abstract

A modular system and method is provided for low bit rate encoding and decoding of speech signals using voicing probability determination. The continuous input speech is divided into time segments of a predetermined length. For each segment the encoder of the system computes a model signal and subtracts the model signal from the original signal in the segment to obtain a residual excitation signal. Using the excitation signal the system computes the signal pitch and a parameter which is related to the relative content of voiced and unvoiced portions in the spectrum of the excitation signal, which is expressed as a ratio Pv, defined as a voicing probability. The voiced and the unvoiced portions of the excitation spectrum, as determined by the parameter Pv, are encoded using one or more parameters related to the energy of the excitation signal in a predetermined set of frequency bands. In the decoder, speech is synthesized from the transmitted parameters representing the model speech, the signal pitch, voicing probability and excitation levels in a reverse order. Boundary conditions between voiced and unvoiced segments are established to ensure amplitude and phase continuity for improved output speech quality. Perceptually smooth transition between frames is ensured by using an overlap and add method of synthesis. LPC interpolation and post-filtering is used to obtain output speech with improved perceptual quality.

Loading the Abstract Image...

First Claim