1. A frame interpolation apparatus for generating a pixel value at an interpolation position in a frame interpolated between a first reference frame and a second reference frame, comprising: a block pair extractor for extracting a plurality of pixel block pairs, each pixel block pair including a first pixel block occupying a first position in the first reference frame and a second pixel block occupying a second position in the second reference frame, the first and second positions being substantially point-symmetric with respect to the interpolation position, wherein the extracted pixel block pairs include at least one pixel block pair where the first and the second positions are exactly point-symmetric with respect to the interpolation position, and at least one pixel block pair where the second position differs from a position exactly point-symmetric to the first position, the difference being at most one pixel position horizontally and vertically; a similarity index generator for calculating, for each pixel block pair extracted by the block pair extractor, a similarity index indicating a degree of mutual similarity between the first and second pixel blocks in the pixel block pair, based on values of pixels in the first and second pixel blocks; a reference pixel selector for selecting a first reference pixel from a central position in the first pixel block in a pixel block pair of maximum similarity, as indicated by the calculated similarity indexes, and selecting a second reference pixel from a central position in the second pixel block in the pixel block pair of maximum similarity; and a first interpolator for calculating the pixel value at the interpolation position from values of the first and second reference pixels.