Evaluation of several variable FIR fractional-sample delay filters

Four main FIR filter types are examined for applicability to the task of fractional-sample delay filtering. Since a balance is sought between the small magnitude of the complex approximation error and rapid re-design for employment in variable-delay situations, techniques with closed-form design formulae have been favoured. Size of fractional delay and oddness or evenness of the filter exhibit simple, but fundamentally important interplay, and an irreducible error at the Nyquist frequency always prevails. Guidelines for choosing between these closed-form candidate filters are suggested. The popular sinc delayer is shown to be a particularly poor performer.< >