Every filter Si is convolved, using the Overlap&Save
method, to L-point blocks of input data (each block
begins L – K points after the previous).
Each block is treated as a separate IR, zero-padded to L and
transformed with FFT in order to obtain a collection of frequency domain
filters S.
(i.e. P = 3).
The results of the multiplications of the P
filters S with the FFTs of the latest P input
blocks are summed in P frequency-domain accumulators, and at the
end an IFFT is done on the content of first accumulator for producing a block
of output data. Only the latest L-K points of the
block have to be kept.