Filter evaluation and selection in wavelet image compression

Choice of filter bank in wavelet compression is a critical issue that affects image quality as well as system design. Although regularity is sometimes used in filter evaluation, its success at predicting compression performance is only partial. A more reliable evaluation can be obtained by considering an L-level synthesis/analysis system as a single-input, single-output, linear shift-variant system with a response that varies according to the input location modulo (2^L, 2^L). By characterizing a filter bank according to its impulse response and step response in addition to regularity, the authors obtain reliable and relevant (for image coding) filter evaluation metrics. Using this approach, they have evaluated all possible reasonably short (less than 34 taps in the synthesis/analysis pair) minimum order biorthogonal wavelet filter banks. Of this group of over 4300 candidate filter banks, they have selected and presented the filters best suited to image compression. While some of these filters have been published previously, others are new and have properties that make them attractive in system design