I refer to these notes. Ive been using Wiener filters for some time now but it is teh causal version. I am puzzled by the uncausal one because it is unstable. Therefore how do people manage to use it? Is it because it is being used offline or something? I know the FFT implements it - is it FIR or something so no poles and therefore stable? I know the FIR Wiener filter appears to be an uncausal one but is stable for that reason. The usual uncausal Wiener filter though is the IIR one and that must have poles.