invFFx
invFFx is the inverse operation of a parametric class of frequency-domain transforms referred to as FFx. FFx denotes a family of linear transforms that map data from the time or spatial domain into a frequency-like domain, with the parameter x controlling properties such as windowing, phase, or scaling. The term invFFx therefore represents the process of recovering the original signal from its FFx-transformed representation, provided FFx is invertible.
Definition and properties: If FFx is represented by a square invertible matrix F_x, the forward transform is
Computational aspects and applications: The cost of invFFx depends on the specific FFx family; many implementations