Direct linear conversion of LSP parameters for perceptual control in speech and audio coding

We have devised a direct and simple scheme for linear conversion of line spectrum pairs (LSP) with low computational complexity aiming at weighting or inverse weighting spectral envelopes for noise control in speech and audio coders. Using optimally prepared coefficients, we can perform the conversion directly in the LSP domain, which ensures low computational costs and also simplifies the check or the modification of unstable parameters. We show that this method performs the same as the weighting in the linear prediction coding domain but with lower complexity in a low-bit-rate situation. The devised method is therefore expected to be useful for low-bit-rate speech and audio coders for mobile communications.