Rationalizing the coefficients of popular biorthogonal wavelet filters

Many wavelet filters found in the literature have irrational coefficients and thus require infinite precision implementation. One of the most popular filter pairs is the “9/7” biorthogonal pair of Cohen, Daubechies and Feauveau (1992), which is adopted in the FBI finger-print compression standard. We present a technique to rationalize the coefficients of wavelet filters that will preserve biorthogonality and perfect reconstruction. Furthermore, most of the zeros at z=-1 will also be preserved. These zeros are important for achieving regularity. The rationalized coefficients filters have characteristics that are close to the original irrational coefficients filters. Three popular pairs of filters, which include the “9/7” pair, are considered