FIELD: copyprotecion of video materials by input of stable identification codes into video signals. SUBSTANCE: water mark is used in digital video signal in method and single-copying device. Built-in water-mark has two versions: one water-mark symbolizes total prohibition of copying and another water- mark denotes permission for single copying. They differ by one bit of water-mark. Water-mark includes additional bits presenting attribute ( image parameters ) of particular TV frame of video signal in digital form, for instance, mean value of amplitude of video signal field. Attribute frame of it is included in water-mark, has field or frame marker which is special signal located in invisible part of frame. Video tape recorder tests water-mark and bit ( 48, 54 ) of single copying, extracts proper attribute from water-mark ( 56 ) and compares it with measured attribute from marked video signal. Recording is allowed only if extracted value of attribute and measured value of attribute match. In process of recording frame marker is removed which prevents formation of second generation copies from recorded video signal and single copying bit is set in correspondence with total prohibition of copying. EFFECT: simplified approach to copyprotection of video materials. 45 cl, 11 dwg
