Adaptive interpolation filter for motion compensated prediction

Standardized hybrid video coding systems are based on motion compensated prediction with fractional-pel displacement vector resolution. In the recent JVT video coding scheme (MPEG-4 part 10, H.264) displacement vector resolutions of 1/4- or 1/8-pel are applied. In order to estimate and compensate these fractional-pel displacements, interpolation filters are used. So far, these interpolation filters are invariant. The same filter coefficients are applied for all sequences and for all images of a sequence. Therefore it is not possible to consider non-stationary statistical properties of video signals in the interpolation process. In this paper an adaptive interpolation scheme is presented. This interpolation scheme uses filter coefficients that are adapted once per image to the non-stationary statistical properties of the video signal. The filter-coefficients are coded and transmitted. Due to the adaptive interpolation filter a coding gain up to 0.8 dB PSNR is obtained in the JVT coding scheme.