Buffered adaptive interpolation filters

H.264/MPEG-4 AVC uses motion prediction with fractional-pixel precision to reduce the temporal redundancy that often exists in a video signal. Previously, it has been shown that Adaptive Interpolation Filter (AIF) methods can significantly improve coding performance compared to the fixed interpolation filters used by existing codecs by adaptively tuning the motion interpolation filters to the video signal's statistics. In this work, a new AIF scheme, named the Buffered Adaptive Interpolation Filter (BAIF) scheme, is presented. The proposed scheme allows the video codec to better exploit the statistical similarities that usually exist among consecutive pictures, thereby improving performance. Specifically, filter buffers are established to store the adaptive interpolation filters previously sent in the bitstream and use them to code subsequent pictures. Further, when multiple reference pictures are used, the proposed scheme allows different interpolation filters to be used for different reference pictures. Simulation results show that the proposed scheme consistently achieves better coding performance than existing AIF schemes. Compared to the current state-of-the-art Enhanced Adaptive Interpolation Filter (EAIF) scheme, the proposed scheme achieves additional coding gain of up to 3%. Compared to H.264/AVC, coding performance is improved by up to 20%.