1. A method for detecting change, comprising: a) receiving, by a processor, a video image from a video stream and a reference image; b) dividing, by the processor, the video image into non-overlapping blocks and the reference image into non-overlapping blocks; c) performing, by the processor, orthogonal transformations on a first corresponding pair of blocks to produce an orthogonally transformed pair of blocks, wherein a corresponding pair includes a block in the video image and a block in the reference image corresponding to the block in the video image; d) modifying, by the processor, the orthogonally transformed pair of blocks by zeroing average value components in the orthogonally transformed pair of blocks; and e) determining, by the processor, an infinity-norm difference between the modified orthogonally transformed pair of blocks.