Hybrid video coding based on highresolution displacement vectors Common motion compensated hybrid video coding standards such as H.263, MPEG1, MPEG2, MPEG4 are based on a fractionalpel displacement vector resolution of xc2xbdpel. Recent approaches like MPEG4 ACE and H.26L (TML5) usea 14pel displacement vector resolution. In order to estimate and compensate fractionalpel 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 highresolution displacement vectors. For this purpose, displacement vector resolutions of 18 and 116pel 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 xc2xbdpel resolution and bilinear interpolation like H.263, MPEG1,2,4. Compared to 14pel displacement vector resolution and a wiener interpolation filter as it is used in MPEG4 ACE and H.26L (TML5), a gain up to 1.0 dB PSNR is obtained.

Advances in hybrid video coding Hybrid video coding is known for a long time and is applied in all video coding standards such as MPEGx or H.26x. This paper shows that there is still enough potential for further coding efficiency improvements. The paper starts with an overview of stateoftheart hybrid video coding schemes such as H.264AVC. Thereafter, our advances on main building blocks of H.264AVC are presented that significantly improve the coding efficiency. For instance, intra prediction is improved by changing scan directions and thus providing better reference pixels for specific prediction directions. Adaptive filtering and high precision motion compensation improves the motion compensated prediction. Furthermore, the combination of transformation, quantization, and entropy coding of the prediction error is improved using an advanced frequency selective coding technique. With the transmission of postfilter hints it is possible to design a Wiener postfilter that significantly enhances the picture quality. Finally, texture synthesis techniques are used to improve the subjective quality for specific textures with homogenous statistical characteristics. This paper presents our abovementioned techniques in detail. Depending on the input sequence and the bit rate, the objective andor subjective gains compared to H.264AVC are quite significant.