It can be shown that multiplication of two DFTs corresponds
to a circular convolution of their time domain sequences.
To implement a FIR filter, a linear convolution is
required.
A procedure for converting a
circular convolution into a linear convolution is the Overlap&Save
algorithm.
Long duration signal sections xm(n) are overlapped of (Q-1)
samples, where Q is the length of the Impulse Response h(n).