1. An apparatus configured to filter an input sample vector, wherein the apparatus comprises: comparison circuitry configured to compare each input sample of the input sample vector to a corresponding element of a reference vector; correction circuitry configured to apply a correction to a reference sum responsive to determining the input sample does not equal the corresponding element of the reference vector, wherein applying the correction to the reference sum comprises: adding a multiple of a corresponding filter coefficient value to the reference sum if the input sample is greater than the corresponding element of the reference vector; and subtracting the multiple of the corresponding filter coefficient value from the reference sum if the input sample is less than the corresponding element of the reference vector; and circuitry configured to utilize the reference sum, after applying any corrections, as a filter output.