Aliasing reduction in soft-clipping algorithms
Fabián Esqueda, Vesa Välimäki, Stefan Bilbao · 2015
Soft-clipping algorithms used to implement musical distortion effects are major sources of aliasing due to their nonlinear behavior. It is a research challenge to design computationally efficient methods for alias-free distortion without over-sampling. In the proposed approach, soft clipping is decomposed into a hard clipper and a low-order polynomial part. A technique for aliasing reduction of the hard-clipped signal is presented based on a polynomial approximation of the ban-dlimited ramp function. This correction function operates by quasi-bandlimiting the discontinuities introduced in the first derivative of the signal. The proposed method effectively reduces perceivable aliasing in soft-clipped audio signals having low frequency content. This work presents the first step towards alias-free implementations of nonlinear virtual analog effects.