An intrinsically reliable and fast algorithm to compute the line spectrum pairs (LSP) in low bit rate CELP coding
Résumé
The code excited linear prediction coder (CELP) makes it possible to synthesize good quality speech at low bit rates. In such a case, speech quality mainly depends on spectral envelope design accuracy. Different kinds of parameters belonging to the parametrical domain (linear prediction coefficients {ai}-LPC-parameters), to the time domain (partial correlation-PARCOR-parameters) and to the frequency domain (line spectrum pairs-LSP-parameters) are used to design the vocal tract transfer function. The latter present interesting properties both for quantization and interpolation, confirming their increasing utilization in low bit rate speech coding. In real time processing, efficient methods must be used to compute this set of parameters. The purpose of this paper is to show attractive properties in real time processing for line spectrum pair computing (LSP). The possibility of computing each LSP parameter independently characterizes the intrinsic reliability of this method based on the use of the Split Levinson algorithm. This method is compared to the one using the Chebyshev polynomials