<title>Classified motion estimation for video coding</title>

Abstract

To reach even still higher compression ratios in video sequence coding the demands posed on the motion estimation module become higher and higher. In this paper we will present a motion estimation scheme which gives a motion field defined on every block (typical 8 by 8 or 16 by 16) and resembles very well the real motion in the scene. The first idea behind motion compensated prediction was just to minimize the local energy of a given block so that it could efficiently be coded. In more complex coding schemes other constraints were added to obtain better visual quality. The most often used constraint is the one to have a smooth motion field which is felt to have a higher correspondence to the real motion compared to the rather "noisy" motion fields obtained from the classical MAD schemes. Many strategies exist to get to these "smooth" motion fields. Most of them are based on some statistical modeling of the resulting motion vector field which asks for iterative solutions. The proposed algorithm is a "one-pass" algorithm and is not explicitly based on any statistical model. A classification procedure on a predefined number of motion vector candidates defines the final motion field.Applications for such a type of motion estimation algorithms can be found in very low bitrate coding where the amount of bits to code the motion field is important compared to the total bitrate , in codecs which want to exploit some features of the human visual system (classification for optimal bit allocation, use of motion masking. . .) or in object based coding where the motion estimation algorithm interacts with the segmentation procedure.In a first section an overview will be given of the concept of using global information to calculate the motion vector field. The second part gives a more thorough description of the new algorithm and in the last part some simulation results will be presented on real sequences. Further research on this algorithm will be done to use it in a segmentation based codec for complex scenes.