Patent ID: 7310428

Claim:
A watermark information detection method for detecting watermark information from a motion picture of any scanning method and having any picture size, the watermark information being embedded in said motion picture by changing pixel blocks of fields constituting said motion picture positioned at predetermined locations in a certain coordinate system, the method comprising: a conversion step for converting said motion picture into a standard motion picture arranged according to a predetermined scanning method and having a predetermined picture size; a coordinate transformation step for transforming the certain coordinate system into a transformed coordinate system with scale factors determined from the scanning method and picture size of said motion picture at a time of embedding the watermark information in said motion picture and the scanning method and picture size of said standard motion picture; and a detection step for detecting the watermark information from fields constituting said standard motion picture by using said transformed coordinate system including specifying the pixel blocks positioned at the predetermined locations in said transformed coordinate system and a step of comparing the data of the specified pixel blocks with reference data and judging whether the watermark information is embedded in said pixel blocks.