COMPLEX, LINEAR-PHASE FILTERS FOR EFFICIENT IMAGE-CODING

With the exception of the Haar basis, real-valued orthogonal wavelet f ilter banks with compact support lack symmetry and therefore do not po ssess linear phase, This has led to the use of biorthogonal filters fo r coding of images and other multidimensional data, There are, however , complex solutions permitting the construction of compactly supported , orthogonal linear phase QMF filter banks, By explicitly seeking solu tions in which the imaginary part of the filter coefficients is small enough to be approximated to zero, real symmetric filters can be obtai ned that achieve excellent compression performance.