Multiresolution approximation using shifted splines
We consider the construction of least squares pyramids using shifted polynomial spline basis functions. We derive the pre and post-filters as a function of the degree n and the shift parameter /spl Delta/. We show that the underlying projection operator is entirely specified by two transfer functions acting on the even and odd signal samples, respectively. We introduce a measure of shift invariance and show that the most favorable configuration is obtained when the knots of the splines are centered with respect to the grid points (i.e., /spl Delta/=1/2 when n is odd and /spl Delta/=0 when n is even). The worst case corresponds to the standard multiresolution setting where the spline spaces are nested.