The NCG is a good statistic for block based watermarking which uses geometric warping. The NCG-strength (given by Lx and Ly) enables the estimation of the robustness of the NCG - x,y-cordinates to lossy compression. A higher strength yields a higher robustness. To embedd watermark bits the NCG - x,y-coordinate can be changed using geometric warping.
You can find papers which base on this approach in:
Pröfrock, D.; Schlauweg, M.; Müller, E.
Video Watermarking by Using Geometric Warping Without Visible Artifacts
Information Hiding (8th IH 2006), 10 -12 July 2006, Alexandria, USA
Pröfrock, D.; Schlauweg, M.; Müller, E.:
A New Uncompressed-domain Video Watermarking Approach robust to H.264/AVC
Compression. Signal Processing, Pattern Recognition and Applications
(SPPRA 2006), 15 - 17 February 2006, Innsbruck, Austria
The NCG can also be used (similiar to filters) as an edge detector. Therefor, you have to compute the NCG-strength of the pixel surrounding blocks. Lx gives the strength of the horizontal edge and Ly the strength of the vertical edge. |
