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. (June 1972), "Discrete representation of signals", Proceedings of the IEEE 60 (6): 681–691, doi:10.1109/PROC.1972.8727, (subscription required (help))
• Strube, Hans Werner (Oct 1980), "Linear prediction on a warped frequency scale" (PDF), Journal of the Acoustical Society of America 68 (4): 1071–1076, doi:10.1121/1.384992
• Härmä, Aki; Laine, Uno K. (July 2001), "A comparison of warped and conventional linear predictive coding" (PDF), IEEE Transactions on Speech and Audio Processing 9 (5): 579–588, doi:10.1109/89.928922, CiteSeerX: 10.1.1.99.1455
• 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, (subscription required (help))
• Laine, Unto K.; Karjalainen, Matti; Altosaar, Toomas (April 1994), "Warped linear prediction (WLP) in speech and audio processing" (PDF), 1994 IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP-94) III, pp. III–349–III–352, doi:10.1109/ICASSP.1994.390018