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
