Subband configuration of adaptive synthesis filter banks for image compression

Subband coding is an efficient technique in image compression, where the same analysis and synthesis filters (either linear phase or non linear phase) are used in all subband levels. In adaptive synthesis filter banks, analysis section comprises of linear phase filters whereas, synthesis section manages a combination of linear phase and non linear filters (in form of delay filters). This paper addresses a novel approach of employing different filter sets for first two levels of subband tree in the synthesis section. It is suggested that synthesis delay filters exhibiting higher degree of deviations from the linear phase synthesis filters are suitable for subband level 1 whereas the delay filters having less deviations from the linear phase filters are appropriate for subband level 2 and linear phase filters are used in all the remaining subband levels. Such subband configuration of adaptive synthesis delay filters has shown reconstruction improvements in image compression.