Motion-compensated image interpolation - rate conversion algorithms for hdtv
K.A. Bugwadia, N.N. Puri · 1997
The Grand Alliance High Definition Television (GA HDTV) system has been tested and approved by the Federal Communications Commission (FCC) Advisory Committee on Advanced Television Service. The aim of this dissertation is to develop new frame rate up-conversion algorithms for utilizing current media (24/30 Hz) source materials for HDTV. A high quality frame rate up-conversion from 24/30 Hz to 60 Hz is essential for displaying information such as motion-picture films available at 24/30 Hz on HDTV receivers. In this dissertation we first address the problem of frame rate conversion and then develop new algorithms for high quality frame rate conversion of different types of source materials. These algorithms are used to perform the necessary frame rate up-conversion of source materials from a temporal rate of 24/30 to 60 Hz for HDTV. A cost effective approach is presented for displaying 24/30 Hz source materials on HDTV by utilizing the developed algorithms. The algorithms utilize motion information along with information about the 2-D sampling grids of the available digitized frames to directly interpolate from them the missing frames. Different methods are used for motion estimation between the available frames. For image sequences from panning static scenes, a simple block matching technique is used to estimate the pel-shifts between the available frames. For image sequences with in-scene motion, a 3-level hierarchical block matching scheme is used to estimate the displacement vector fields in a given image sequence. To better approximate motion field of a 3-D moving rigid object and linear deformation such as rotation and zooming, a 2-D affine transform motion model utilizing 2-D deformable triangular patches is used for motion estimation. A polynomial curve fit is used for estimating displacements of the available information within the missing frames. The missing frames are interpolated using corresponding pels/blocks lying on the same sampling grid from the other available frames. A fallback mode is incorporated into the algorithms to discontinue the interpolation process for those regions that are not present (or cannot be estimated properly) within the other available frames. Finally, programs are written to implement the algorithms and are tested on different real video sequences. A display is created under the X windows system for simultaneous animation of both the original 24/30 Hz as well as the newly generated 60 Hz sequences.