A unified framework for LPC excitation representation in residual speech coders

The efficient representation of the excitation signal to an LPC (linear predictive coding) synthesis filter by means of a vector expansion of the residual signal is examined. According to this approach the excitation signal is represented as a linear combination of a small number of vectors taken from a given vector set, known at both ends of the transmission channel. It is demonstrated that this approach provides a unified framework for describing and analyzing a wide range of residual speech coders, from multipulse LPC and code-excited linear prediction to residual transform coders, and leads to generalization of some of these schemes. Optimally conditions based on the singular-value decomposition (SVD) of the impulse-response matrix of the perceptually weighted LPC synthesis filter are given. A resulting simplified predictive transform coder is proposed and examined by computer simulation