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, Alan V.; Johnson, D.H. (June 1972), "Discrete representation of signals", Proceedings of the IEEE, 60 (6): 681–691, CiteSeerX 10.1.1.456.9776, doi:10.1109/PROC.1972.8727
- 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, Unto K. (July 2001), "A comparison of warped and conventional linear predictive coding" (PDF), IEEE Transactions on Speech and Audio Processing, 9 (5): 579–588, CiteSeerX 10.1.1.99.1455, doi:10.1109/89.928922
- 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
- Laine, Unto K.; Karjalainen, Matti A.; 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, ISBN 978-0-7803-1775-8