Enhanced region-based adaptive interpolation filter

Motion compensation with quarter-pel accuracy was added to H.264/AVC to improve the coding efficiency of images exhibiting fractional-pel movement. To enlarge the reference pictures, a fixed 6-tap filter is used. However, the values of the filter coefficients are constant regardless of the characteristic of the input video. An improved interpolation filter, called the Adaptive Interpolation Filter (AIF), that optimizes the filter coefficients on a frame-by-frame basis was proposed to solve the problem. However, when the image is divided into multiple regions, each of which has different characteristics, the coding efficiency could be further improved by performing optimization on a region-by-region basis. Therefore, we propose a Region-Based AIF (RBAIF) that takes account of image locality. Simulations show that RBAIF offers about 0.43 point higher coding gain than the conventional AIF.