Patent attributes
Unique encoding of each of a substantial number of distribution video copies of a program such as a motion picture is produced by altering the images slightly at several pre-selected locations in the program in a uniquely coded pattern. Suspected counterfeits can be compared with an unaltered master video to determine the encoded number for the copy which was counterfeited to enable tracking the source of the counterfeit. Preferably, each frame of several whole scenes is altered at each location by shifting an image so as to make the alterations largely undetectable by counterfeiters but easily detected by comparison with an unaltered master video. Artifacts are inserted in patterns representing a unique number for the program. These supplement the encoding by alteration of images and gives added means to aid in tracing counterfeit copies.
