Zero-branch tree encoding of speech pitch/voicing signals

A computationally efficient, although suboptimal, tree encoding method for the pitch and voicing parameters of an LPC (linear predictive coding) vocoder is presented. It is shown that when pitch and voicing signals are combined, it becomes difficult to take advantage of linear predictors and at the same time avoid any errors in voicing. The modified pitch tree coder presented here solves this problem by incorporating a branch leading to zero pitch value from each node of the tree. Only two bits per analysis frame are used to convey the combined pitch/voicing signal, with 1.585 bits being used to encode nonzero pitch values