High-Accuracy Length-6 Cubic Interpolators

This letter proposes a frequency-domain weighted least-squares (WLS) method for designing a length-6 cubic interpolation kernel constructed by connecting three piecewise polynomials of third-degree, and the optimal coefficients are found through minimizing the weighted squared error between the desired and actual frequency responses of the length-6 cubic. This frequency-domain approach can design various cubics with different frequency responses by adjusting the weighting functions in different frequency bands, and even ignore “don´t care” bands. An interpolation example is given to illustrate that the length-6 cubic can achieve much higher accuracy interpolations than the other interpolators with fixed frequency characteristics.