QUADRATURE MIRROR FIR FILTERS FOR SUB-BAND CODING OF IMAGES

Abstract

Design of multirate filterbanks (MFB) that allow for exact reconstruction is important for subband coding of images. Exact reconstruction implies no frequency b' aliasing and no amplitude and phase distortion. Imposing :uadrature symmetry condition on the filters in a MFB, frequency aliasing can be eliminated completely. When the individual filters are not constrained to be of linear phase, amplitude and phase distortion can be elim-inated. In this dissertation the mathematical basis of multirate filterbanks is studied with emphasis on the quadrature symmetry condition and exact reconstruction property. Using these mathematical results a MiB for image subband coding is simulated using spectral factorization of linear., phase filters. Lattice bank designed with the same considerations is extenuea to two-dimensions. The frequency response of the channels (subbands) are obtainea and reconstruction error are calculated for the aouve two cases. The reconstruction is found to be fairly good in both the cases.-The reconstruction error at the sub-band edges is calculated C.nd it is found to be •--0.0026 dB in the first case and—l05 d6 in the second case. These multirate filterbanks which satisfy exact reconstruction property can be useful for image subband coding applicat-ions.