subtract the pattern from the film grain pattern selector 27 based on the output bit of the coding device 21 as described above in contrast the blending block 14 of fig1 and 3 serves only to add film grain patterns the operation of the system 1000 of fig5 most closely follows the existing film grain technology standard in the case where the image content comprises a movie a determination as to which film grain patterns undergo addition to a particular movie title occurs in advance for all users to make sure that every audience will have the same experience before the release of the movie experts with u201c golden u201d eyes will view the movie with the film grain added if such experts find some unpleasant artifacts the film grain parameters undergo adjustment to create different film grain patterns for subsequent evaluation the addition or subtraction of film grain patterns performed by the system 1000 of fig5 yields the same visual effect as adding film grain to the original movie title fig6 depicts a system 2000 in accordance a third preferred embodiment of the present principles for recovering the embedded information using the pattern addition pattern subtraction model described previously as with the detection systems 20 and 200 of fig2 and 4 the detection system 2000 of fig6 employs a comparator 24 that compares the test picture 22 to the comparison image 12 to generate a difference data 25 a film grain pattern selector 27 selects the same pattern that was selected during the embedding process this film grain pattern is then compared to the difference data 25 by a comparator 28 the comparator 28 determines whether the difference data better matches the film grain pattern or the inverse of the film grain pattern and.