allpassThiran1stOrder

Allpass interpolator. https://ccrma.stanford.edu/~jos/pasp/First_Order_Allpass_Interpolation.html http://users.spa.aalto.fi/vpv/publications/vesan_vaitos/ch3_pt3_allpass.pdf

It is recommended to use the range [0.5 .. 1.5] for best phase results. Also known as Thiran filter.