Method and device for assessing the presence of a watermark in a video
View Patent ↗The invention relates to a method for assessing the presence of a watermark in a video wherein the video comprises at least a sequence of frames. The method comprises for at least one frame among one of the sequences of frames the steps of computing a set of axial cross-correlation values, wherein each axial cross-correlation value corresponds to a correlation between the frame and a reference watermark shifted along a spatial horizontal axis; obtaining a detection score by computing a weighted sum of values output by a function applied to said axial cross-correlation values; assessing the presence of a watermark according to the detection score. Such method is particularly well adapted to the detection of disparity coherent watermark but is compliant with any watermarking technique. A device implementing the method is further disclosed.
1. A method for assessing the presence of a watermark in a video, wherein said video comprises at least a sequence of frames, the method comprises for at least one frame among one of the sequences of frames:
computing a set of axial cross-correlation values, each axial cross-correlation value corresponding to a correlation between said frame and a reference watermark shifted along a spatial horizontal axis;
obtaining a detection score by computing a weighted sum of values output by a function applied to said axial cross-correlation values; and
assessing the presence of a watermark according to the detection score.
2. The method according to claim 1 , further comprising a preliminary processing of said frame, said preliminary processing comprising at least one of whitening said frame, or clipping.
3. The method according to claim 1 , wherein each axial cross-correlation value is computed for a shift within a range.
4. The method according to claim 1 , wherein said function comprises an identity function.
5. The method according to claim 1 , wherein assessing the presence of a watermark according to the detection score further comprises comparing the detection score to a first threshold.
6. The method according to claim 1 , wherein the function outputs the axial cross-correlation value in case where axial cross-correlation values which is higher than a clipping threshold and the function outputs a zero in case where axial cross-correlation values which is lower than the clipping threshold.
7. The method according to claim 1 , wherein said video comprises two sequences of frames corresponding to a left view and a right view.
8. The method according to claim 1 , wherein said video comprises a sequence of synthesized frames derived from a left and a right view.
9. A non-transitory computer-readable storage medium storing program instructions computer-executable to perform the method of claim 1 .
10. A device for assessing the presence of a watermark in a video, wherein said video comprises at least a sequence of frames, the device comprising at least one processor adapted to:
compute a set of axial cross-correlation values for at least one frame among one of the sequences of frames, each axial cross-correlation value corresponding to a correlation between said frame and a reference watermark shifted along a spatial horizontal axis;
obtain a detection score by computing a weighted sum of values output by a function applied to said axial cross-correlation values; and
assess the presence of a watermark according to the detection score.
11. The device according to claim 10 , wherein the processor is further adapted to preliminarily process said frame by whitening said frame, or clipping.
12. The device according to claim 10 , wherein each axial cross-correlation value is computed for a shift within a range.
13. The device according to claim 10 , wherein said function comprises an identity function.
14. The device according to claim 10 , wherein the assessing of the presence of a watermark according to the detection score further comprises the processor further configured to compare the detection score to a first threshold.
15. The device according to claim 10 , wherein the function outputs the axial cross-correlation value in case where axial cross-correlation values which is higher than a clipping threshold and the function outputs a zero in case where axial cross-correlation values which is lower than the clipping threshold.
16. The device according to claim 10 , wherein said video comprises two sequences of frames corresponding to a left view and a right view.
17. The method according to claim 10 , wherein said video comprises a sequence of synthesized frames derived from a left and a right view.
18. A method for determining the presence of a watermark in a video, wherein said video comprises at least a sequence of frames, the method comprising for at least one frame among one of the sequences of frames:
computing a set of axial cross-correlation values, each axial cross-correlation value corresponding to a correlation between said frame and a reference watermark shifted along a spatial horizontal axis;
obtaining a detection score by computing a weighted sum of values output by a function applied to said axial cross-correlation values; and
obtaining the watermark using a polarity value of the detection score.
19. A device for assessing the presence of a watermark in a video, wherein said video comprises at least a sequence of frames, the device comprising at least one processor adapted to:
compute a set of axial cross-correlation values for at least one frame among one of the sequences of frames, each axial cross-correlation value corresponding to a correlation between said frame and a reference watermark shifted along a spatial horizontal axis;
obtain a detection score by computing a weighted sum of values output by a function applied to said axial cross-correlation values; and
obtain the watermark according to a polarity value of the detection score.