A video processor and method for swiftly detecting swaps occurring between links during transmission of images by the dual-link system. A first image combiner unit combines an image D1 of a first link as an odd-numbered image, with an image of a second link, to generate a first combination image. A second image combiner unit combines an image of a second link as an odd-numbered image, with the image of the first link to generate a second combination image. An edge detector unit detects the horizontal edge of the first combination image and the second combination image. A judgment unit compares the number of triple edges in the first combination image and second combination image, and judges the combination image having more triple edges as the error image. The triple edges contain three consecutive edges along the horizontal direction, and the rising edges and falling edges are arrayed alternately.