A filter circuit is provided which has a filtered input and an unfiltered
input. The filtered input passes through delay elements to coefficient
circuitry. The unfiltered input passes to the coefficient circuitry
without passing through the delay elements. In this manner, an unfiltered
offset can be added to the filtered output. This filter is especially
useful when the filtered value is in phase representation form; for
example, when the filter value is a hue value encoded as a phase.