Digital video technology has been characterized by a steady growth in the last decade. With the development of mobile communications and multimedia techniques in recent years, the traditional audio service no longer satisfies the ongoing demand for better communications. New applications like 3G mobile phone video communications; video conferencing and video streaming on the web continuously push for further evolution of research in digital video coding. Aware of this relevant challenge, research has been focusing on video compression for already more than twenty years. People from both the industry and research teams have collaborated in groups like the International Telecommunication Union (ITU) or the Moving Picture Experts Group (MPEG) to design several international standards for transmission and storage of digital video. Compression is mainly realized by exploiting the redundancy present in the data. A sequence of images contains an intrinsic, intuitive and simple idea of redundancy; two successive images are very similar. This simple concept is called temporal redundancy. Motion estimation and compensation techniques have shown their efficiency to reduce the temporal redundancy in this respect. The principle is the following. The displacement of objects between successive frames is first estimated (motion estimation). The resulting motion information is then exploited for an efficient inter-frame coding (motion compensation). Consequently the motion information along with the prediction error is transmitted instead of the frame itself.