SYSTEM AND METHOD FOR ERROR CORRECTION IN A CORRELATION-BASED PITCH ESTIMATOR

摘要

The present invention comprises an improved method for estimating and correcting the pitch parameter using correlation techniques. The method comprises first performing a correlation calculation on a frame of the speech waveform, which produces one or more correlation peaks at respective numbers of delay samples. The vocoder then compares the one or more correlation peaks with a clipping threshold value. If a single peak at location Pd is greater than the clipping threshold, then the vocoder perfoms additional calculations to ensure that this single correlation peak is not a second or higher multiple of the true pitch. In the preferred embodiment, the vocoder assumes the peak at location Pd is a second multiple of the true pitch, and the vocoder searches for the true pitch at a first multiple of the peak location Pd. If a peak is found at this first multiple, referred to as Pd', and certain other criteria are met, then the peak at location Pd' is presumed to be the true pitch. In this case, the pitch is set to the number of delay samples indicated by Pd'. Thus the present invention more accurately disregards false peaks which are second or higher multiples of the true pitch.