Block size dependent interpolation filter selection and mapping

A device implementing the subject video coding system may include a processor that encodes an N×M block using an x-tap filter for horizontal interpolation and a y-tap filter for vertical interpolation, where x is proportional to N and y is proportional to M. The processor may use a current block size to select an interpolation filter with a first length or a second length for a current block, use an overlapped block size to select an interpolation filter with a first length or a second length for overlapped areas, and, when a neighboring block uses a long interpolation filter and a short interpolation filter is selected for the overlapped area, maps the long interpolation filter to a short interpolation filter of a selected type. The processor may calculate a reference block size based on a scaling factor and use the reference block size to select a filter length.