| 摘要 |
<p>A global motion vector for a first video frame identifies a shift that, when applied to another frame of a television picture, increases the similarity between the two frames. In order to estimate this shift the method comprises selecting picture elements from the first frame; comparing the selected picture elements with correspondingly positioned picture elements of the other frame to produce a measure of similarity in respect of zero shift; comparing, for each of a plurality of trial shifts, the selected picture elements with picture elements of the other frame that have the same mutual positions but shifted by the respective shift, to produce a measure of similarity in respect of that shift; and identifying that shift (or zero) which gives rise to a measure indicative of high similarity. The number of selected picture elements is in the range of 0.1 % to 5% of the total number of picture elements in the frame - for example, they may be taken only from selected lines of the picture, the number of selected lines being less than 5% of the total number of lines in the frame - possibly even as few as three. The selected picture elements consist of a set of contiguous picture elements taken from the central portion of each selected line. The shifts considered may be primarily or even exclusively horizontal.</p> |
