Re: FIR filters
Now we're really getting our terminology quacked out. Peter, I was referring to your diagram, although I really should have quoted it properly.
An impulse response is not IIR or FIR, you can design IIR coefficients which have linear phase easily via the least squares method, but the internal structure is still an IIR. (there is even a MATLAB function for this, iirgrpdelay?)
IIR and FIR normally refer to the structure of the underlying filter (the fixed structure, like Peter's diagram, which you fill coefficients into), as it is implemented in code, to do the filtering! The frequency domain method, like in the lake patent would be different. More similar to the operation of something like filtfilt (MATLAB's the forward, backwards filter), which I think you both are referring to (Michael, Frank).
