US Patent 8004607 Region-based cadence detector

In a method for detecting the cadence of a sequence of images, each pixel in each current field in the sequence of images is compared to at least one pixel in at least one previous field. A pixel motion phase value is assigned to each pixel in the field as a function of the result of that comparison. For each block of pixels in the current field, a block motion phase value is determined from the motion phase values of the pixels in the block. The current field is segmented into at least one region, with each region comprising a whole number of blocks, as a function of at least the determined block motion phase values. A region motion phase value is assigned to each region, based on the block motion phase values for the blocks in the region.