This paper introduces a new method for the interpolation that has to be performed when motion estimation and compensation are applied to interlaced sequences with subpel accuracy. It is based on the assumption that a uniform motion exists between two successive frames. The exact formulas for the estimation are derived. They show that in order to obtain a correct interpolation of each field of one frame, it is necessary to use the information of both fields of this frame. Because the ideal filters have infinite impulse responses, the filter design is discussed, and the efficiency is measured for typical sequences.

This paper deals with the problem of motion estimation and compensation with sub-pixel accuracy when interlaced moving sequences are processed. Provided a translational motion exists between consecutive frames (or that the image can be partitioned into sets of points with such a motion) the exact formulas for the prediction of pixels are derived. It is shown that in order to obtain a correct prediction of any pixel in one frame, it is required to use the information of both fields of the previous frame. The ideal interpolation filters are of infinite length. Therefore, the question of designing finite length filters is addressed and alternative design methods are proposed. The efficiency of the method is then measured on typical sequences.

A compatible coding scheme for interlaced HDTV (high-definition television) is proposed. This scheme provides a standard definition signal and a second channel containing the additional information required to reach the HD resolution. The global scheme is of the pyramidal type: the standard TV is obtained by downsampling the HDTV signal by means of a field-based operation. The standard TV signal is coded, decoded, and upsampled. It is used as a prediction of the HD signal and the prediction error is coded in a second channel. In both branches, motion-compensated hybrid DCT coding is used. In addition, the DCT is taken within the frame.>