Design of regularity constrained linear phase modulated lapped transforms

The regularity constrained linear phase filter banks reported recently are based on generalized bi-orthogonal lapped transforms. They do not have a modulated structure and hence all the basis functions are to be optimized separately. Design and implementation complexity increases with the size of the block transform. In this paper, a cosine-modulated approach for the design of orthogonal modulated lapped transforms with basis functions having regularity, arbitrary length and linear phase is presented. Due to the modulated structure, only the prototype filter needs to be optimized to satisfy all the design criteria. Besides simplifying the design process they have efficient implementation based on poly-phase structure and discrete cosine transforms. Added regularity features enhance the performance of the transform in capturing dc as well as polynomial signal variations, leading to smooth reconstructed signals even under low bit rate