1. Blind Watermark Detection on MPEG4-2D Mesh Animation 報告者：梁晉坤 指導教授：楊士萱博士

2. Outline Public and Private Watermarks Wavelet Transform Watermark Embedding Watermark Detection Simulation Results

3. Public and Private Watermarks Public watermarks are those where an end user of the data is able to extract the watermark. (Blind detection, the original work is not need) Private watermarks are those where watermark extraction requires secret information known only to the watermark embedder. (informed detection, the original work is need)

5. Wavelet Transform Multiresolution representation Two methods of wavelet transform Convolution Lifting Realizing discrete time wavelet transform by “ Filter Bank ”

6. Analysis and Synthesis h 0 (t) h 1 (t) 22 22 y1y1 y0y0 X 22 22 g 0 (t) g 1 (t) X’X’ Analysis FilterSynthesis Filter

7. Multiresolution Representation Original L1L1 H1H1 L2L2 H2H2 …… LpLp HpHp Local Global

8. h 0 (t) h 1 (t) 22 22 y 0,1 y 0,0 2 ‘ th level decomposition1 ‘ th level decomposition h 0 (t) h 1 (t) 22 22 y1y1 y0y0 X

9. Watermark Embedding Step 1, embedding component selection Select larger component (X or Y) In tie, select X component Step 2, perturbing selected component Bit=1, positive direction Bit=0, negative direction Record Key file for blind detection

10. X>Y X<Y X=Y Watermarking Bit = 1/ 0

11. Watermark Detection Informed detection(Hard decision) According to Original mesh and Attack mesh to extract watermark sequences If PointW>=pointO extractBits push 1 else extractBits push 0 Counting correct bits from extract bits Original mesh is need

12. Informed detection(Soft decision) According to Attack mesh and key file to detect whether watermark is embedded. Original mesh is not need, but some of the original mesh coefficients mush be saved in the key file.

13. Correlation: Original Correlation Embedded Correlation If m=1 then Mi=1, else if m=0 then Mi=-1

14. Attacked Correlation If CorrA = CorrE-thres then watermark is embedded. Otherwise watermark is not embedded.

15. Correlation Coefficient CorrCoef(X,Y)=Corr(X,Y)/SigmaX*SigmaY SigmaX = sqrt(E[X 2 ]-(E[X]) 2 ) SigmaY = sqrt(E[Y 2 ]-(E[Y]) 2 ) Corr(X,Y) = E[XY]-E[X]E[Y] -1=<CorrCoef(X,Y)<=1

16. X:Original Coefficients Y:Embed Coefficients Z:Attack Coefficients W:Watermark Sequences(1, -1) Compute CorrCoef(Y-X,W), CorrCoef(Z-X,W), CorrCoef(X,W), CorrCoef(Y,W) and CorrCoef(Z,W) If CorrCoef(Z-X,W)> threshold, we consider watermark is detected. Otherwise, watermark is not detected

17. Simulation results(Parameters) Mesh12 MPEG-4 conformance testing 128 MOPs, each MOP has 120 points and 187 triangles Threshold=0 Watermark, 127 bits PN code Quality=0.01 (MMSE) Resolution level ： 2,4,6

18. Working environment GTS Mesh12 FindWI_Mesh12 par_final_mesh12_128_001 Key File Intensity CorrO, CorrE,(Original Coefficients) Embedded Location

19. Affine attack Ite m ScalingRotate degreeTranslate distance 11.30(12, 0) 2125(0,5) 30.765(-11,-9)

20. Smoothing attack Smooth filter S3={1/4,1/2,1/4} S5={1/5,1/5,1/5,1/5,1/5}

21. Other Attacks Simplifying attack Enhancement(1.5) and Attenuation(0.6) RNTest RNMVTest RNMVAffineTest