Fabián Esqueda, Vesa Välimäki and Stefan Bilbao
Companion page for a paper in the 2016 European Signal Processing Conference (EUSIPCO-16),
Budapest, Hungary, Aug 29 – Sept 2, 2016
A new method for aliasing reduction in soft-clipping nonlinearities is proposed. Digital implementations of saturating systems introduce harmonic distortion which, if untreated, gets reflected at the Nyquist limit and is mixed with the signal. This is called aliasing and is heard as a disturbance. A new correction function, derived by integrating the bandlimited ramp function, is presented. This function reduces the level of aliasing distortion seen at the output of soft clippers by quasi-bandlimiting the discontinuities introduced in the second derivative of the signal. The proposed method increases the quality of the signal by attenuating those aliased components that lie on the lower end of the spectrum, which are known to be perceptually important. The four-point version of the algorithm reduces aliasing at low frequencies by up to about 50 dB. This work extends our understanding of aliasing in nonlinear systems and provides a new tool for its suppression in virtual analog models.
You can download a PDF version of the EUSIPCO-16 presentation slides here.
Clipped logarithmic chirp before and after integrated BLAMP correction:
Guitar riff before and after clipping with integrated BLAMP correction: