Warped linear predictive coding

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 allpass filters. This can have advantages in reducing the bitrate required for a given level of perceived audio quality/intelligibility, especially in wideband audio coding.

History

Warped LPC was first proposed in 1980 by Hans Werner Strube.

References

• Oppenheim, A.V.; Johnson, D.H. (1972) Discrete representation of signals, Proceedings of the IEEE, vol. 60, no. 6, pp. 681–691, June 1972
• Strube, H.W. (1980) Linear prediction on a warped frequency scale, Journal of the Acoustical Society of America, vol. 68, no. 4, pp. 1071–1076, Oct 1980
• Harma, A.; Laine, U.K. (2001) A comparison of warped and conventional linear predictive coding, Speech and Audio Processing, IEEE Transactions on, vol. 9, no.5 pp. 579–588, July 2001
• Kruger, E.; Strube, H.W. (1988) Linear prediction on a warped frequency scale, Acoustics, Speech, and Signal Processing [see also IEEE Transactions on Signal Processing], IEEE Transactions on, vol. 36, no. 9 pp. 1529–1531, September 1988
• Laine, U.K.; Karjalainen, M.; Altosaar, T. (1994) Warped linear prediction (WLP) in speech and audio processing, Acoustics, Speech, and Signal Processing, 1994. ICASSP-94., 1994 IEEE International Conference on, vol.iii, no.pp.III/349-III/352 vol.3, 19–22 April 1994