Circular LPC modeling and constant pitch transform for accurate speech analysis and high quality speech synthesis

In this paper, Circular LPC analysis, a windowless signal modeling method for periodic signals, is re-visited as a high-resolution pitch-synchronous speech spectrum analysis tool. In addition, the Constant Pitch Transform is introduced as an alternative residual signal representation, suitable for speech coding and text-to-speech synthesis applications. Since circular LPC analysis requires exact periodicity, the original narrowband or wideband signal is upsampled to account for fractional pitch periods at original sampling rate. Hence, both methods are formulated to work on the higher sampling rates. The analysis and synthesis using individual pitch cycles are explained in detail. Furthermore, three unique circular LPC synthesis methods are presented to address the problem of initial rest. The results of preliminary experiments show that it is possible to synthesize artifact free speech using the proposed method.