Voice messaging system with unified pitch and voice tracking

Abstract

This voice messaging system provides an LPC analyzer in combination with a pitch extractor wherein LPC parameters and a residual signal organized in a sequence of speech data frames are provided by the LPC analyzer as an output representative of an analog speech signal. The pitch extractor is operably associated with the LPC analyzer and produces a plurality of pitch candidates for each of the speech data frames in the sequence thereof. Dynamic programming is performed on the plurality of pitch candidates for each speech data frame and also with respect to a voiced/unvoiced decision of the speech data for each frame by tracking both pitch and voicing from frame to frame to provide an optimal pitch value and also an optimal voicing decision. During dynamic programming, a cumulative penalty for a sequence of frame pitch/voicing decisions is accumulated by defining a transition error between each pitch candidate of a current speech data frame and each pitch candidate of the preceding frame, and defining a cumulative error for each pitch candidate of the current frame equal to the transition error between the pitch candidate of the current frame plus the cumulative error of an optimally identified pitch candidate in the preceding frame to locate the track providing optimal pitch and voicing decisions based upon the lowest cumulative penalty. An encoder then encodes the LPC parameters as generated by the LPC analyzer and the optimal pitch and voicing decisions for each speech data frame for subsequent use in providing an audible synthesized speech output substantially identical to the original speech input.