Efficient interconversion algorithm for PARCOR and LSP parameters

The paper introduces an efficient algorithm for calculating line spectrum frequencies from PARCOR coefficients and vice versa. The algorithm employs a recursive technique to generate the line spectrum from PARCOR coefficients. In each recursion, a rotation and scaling operations on the complex frequency plane are required. The even and odd line spectrum frequencies are found to be the zero crosspoints on the real and imaginary axis of the complex plane, respectively. The paper also points out some interesting relationships between PARCOR coefficients and line spectrum frequencies. These relationships can be exploited to formulate a more efficient quantization scheme for coding LPC parameters at 30 bits per frame with transparent quality