Hybrid video coding based on high-resolution displacement vectors

ABSTRACT Common motion compensated hybrid video coding standards such as H.263, MPEG-1, MPEG-2, MPEG-4 are based on a fractional-pel displacement vector resolution of 1/2-pel. Recent approaches like MPEG-4 ACE and H.26L (TML5) use a 1/4-pel displacement vector resolution. In order to estimate and compensate fractional-pel displacements, the image signal has to be interpolated. Therefore different interpolation filters are used in the standards. In this paper an enhanced motion compensated hybrid video codec is presented, which is based on high-resolution displacement vectors. For this purpose, displacement vector resolutions of 1/8and 1/16-pel are used in order to improve the motion compensated prediction and the coding efficiency. The coding results for different resolutions are presented and the dependence on different interpolation filters is analysed. It turned out that the higher the displacement vector resolution is, the higher the influence of the filter on the coding gain is. A gain up to 3.0 dB PSNR is obtained compared to a hybrid video codec, which is based on 1/2-pel resolution and bilinear interpolation like H.263, MPEG-1,2,4. Compared to 1/4-pel displacement vector resolution and a wiener interpolation filter as it is used in MPEG-4 ACE and H.26L (TML5), a gain up to 1.0 dB PSNR is obtained.