Table Look-Up
A general approach to variable filtering is to tabulate the filter coefficients as a function of the desired variables. In the case of fractional delay filters, the impulse response is tabulated as a function of delay , , , where is the interpolation-filter order. For each , may be sampled sufficiently densely so that linear interpolation will give a sufficiently accurate ``interpolated table look-up'' of for each and (continuous) . This method is commonly used in closely related problem of sampling-rate conversion [462].
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Polynomials in the Delay
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Order 5 over a range of fractional delays