Warped linear predictive coding (warped LPC or WLPC) is a variant of linear predictive coding in which the spectral representation of the system is modified, for example by replacing the unit delays used in an LPC implementation with first-order all-pass filters. This can have advantages in reducing the bitrate required for a given level of perceived audio quality/intelligibility, especially in wideband audio coding.
Kruger, Elmar; Strube, Hans Werner (September 1988), "Linear prediction on a warped frequency scale", IEEE Transactions on Acoustics, Speech, and Signal Processing, 36 (9): 1529–1531, doi:10.1109/29.90384