Patent ID: 8121341

Claim:
A detecting data processing apparatus for detecting payload data from a water marked image that has been generated by combining an image frame with a two-dimensional water mark pattern, the water mark pattern comprising a plurality of regions, each region of the pattern being associated with one of a plurality of symbols of the payload data word, each region of the water mark pattern including a two dimensional water mark block selected from a predetermined set of possible water mark blocks to represent the value of the payload data symbol associated with that region, the apparatus comprising a block match prior probability calculator configured to correlate each region of the water marked image frame with each of the water marked blocks from the set of water marked blocks, to form for each region a set of block match probability surfaces, each block match probability surface providing a two-dimensional distribution of probability vectors, for each possible water mark block, representing a probability that the water mark block is present at a position identified by that distortion vector, and a payload probabilities calculator configured to combine a distortion probability value for each region with each of the block match probability surfaces for each of the water mark blocks that may be present in the region, to form for each region, for each of the possible values of the payload symbol a probability value that that region includes that symbol value, and to form from the probability values for each symbol value from each of the regions of the water mark frame a set of payload probability values representing the probability of each of the possible symbol values for each payload symbol, from which an estimate of the payload data can be generated from the payload probability values.