Video Watermarking Using Motion Vector - Semantic Scholar

16th IPPR Conference on Computer Vision, Graphics and Image Processing (CVGIP 2003)

2003/8/17~19, Kinmen, ROC

Video Watermarking Using Motion Vector C. H. Kung(龔志賢) 1, J. H. Jeng(鄭志宏) 2 Y. C. Lee(李泳展) 1, H. H. Hsiao(蕭涵徽) 2, W. S. Cheng(鄭婉淑) 3 1. Engineering & Management of Advanced Technology Department, Chang-Jung Christian University, Tainan, Taiwan, ROC 2. College of Electrical and Information Engineering, I-Shou University, Kaohsiung, Taiwan, ROC 3. Department of Information Management, Chang-Jung Christian University, Tainan, Taiwan, ROC Tel: +886-6-278-5123 ext.2407, Fax: +886-6-278-5886, e-mail: [email protected] how to embed information into digital still image. There were some researches proposed for embedding watermarks into video streams. Cappellini et. al.[8] proposed a video watermarking scheme that embed watermarks into watermarked frame’s DFT coefficients. Langelaar and Lagendijk[9] proposed a DEW technique that embed information into DCT coefficients by discarding high frequency band based on DCT. The way they used may cause computationally inefficient that redo the inverse DCT and forward DCT for processing a compressed video sequence. In the scheme, the watermark is embedded into video streams. For saving the storage space and accelerate the transmission speed, compressing the video is required. In the proposed approach three innovative advantages three kinds of techniques are proposed. The first is that the original video wouldn’t be required in the extraction process. The second is that the watermark would be obtained without extracting the video, that is, it’s easy for decoding. The third is that the proposed technique makes hardware realization feasible.

Abstract Digital videos become more and more popular, meanwhile, the illegal usages and distribution also grow as well. It also arise another problems such as users can copy vast amount of digital data at will. Watermark is a logo belongs to the owner and watermarking is the technique which is created for protecting the copyright. The watermark can be embedded and hidden into the owner’s video products. Because the owner can prove his ownership by extracting the watermark such that the watermarked videos are distributed via the public channel, the unauthorized copying may be discouraged. In the proposed scheme, the watermark is embedded into the MV (Motion Vector) of ME (Motion Estimation) of the video and the watermark in the video could be retrieved without original video. The proposed technique of embedding watermark into videos will not increase the data quantity; on the other hand, the information quantity can be increased.

Keyword: Motion Vector, Motion Estimation,

2. Permutation

Watermark, Video.

This permutation is defined as TK . The permutation matrix is given by 1  1 (1) TK =  K K + 1  for any positive integer K , there exists a minimum number ρ (K ) such that T Kρ ( K ) = I 2 . There are three purposes for performing the permutation on the watermark. First, the spatial correlation can be removed. Second, the watermark is robust against picture-cropping operations. Third, the parameters K and α can be kept for security considerations.

1. Introduction The watermark technology is divided into two categories: visible watermark and invisible watermark. Invisible watermark technique is classified into special domain [3-5] and frequency domain approaches. By adjusting each pixel’s gray level embedding watermarks into digital still image in the spatial domain can be achieved. In the frequency domain watermarking, digital still image is first transformed by a function such as DCT[6,7] and then modify these transformed coefficients. In general, a watermark technique should have the following basic features: Transparency, Robustness, Soblivious, and Security. Most watermarking scheme was mainly researched on

3. System Implementation The block diagrams of encode and decode processes diagrams are shown as the Fig. 1 and Fig. 2. 547


The steps of hiding message into the Motion Vector of MPEG video using watermarking and MPEG techniques are illustrated as Fig. 3., the MV wm is the watermark embedded Motion Vector.

2003/8/17~19, Kinmen, ROC

Step1: Extracting The extracting processes are depicted as the Fig. 6. Step1: Depermute

A. Watermark Embedding The processes of embedding the watermark w into the host video are as following:

Reverse the permutation process: The reverse can β be done by the transform Tδ on the pixel positions of w p ' , where β is given in permuting the

Step 1: Scramble

embedding scheme.

Perform the scrambling operation on the watermark w to obtain ws by ws = w ⊕ c (2) where c is the chaotic binary sequence of

Step2: Descramble Reverse the scramble process using the chaotic binary sequence c to obtain the retrieved watermark w′ by

size N 2 , w denotes the N × N binary watermark image, and ws is the watermark after scrambled.

w′ = w′s ⊕ c

Step2: Permutation

4. Experimental Results The video sequence 352 × 288 is compressed and 44 × 36 watermark is embedded. And the format of the testing video is illustrated in the Table. 1. As demonstrated in Fig. 7. and Fig. 8., a preliminary PC-based application which realizes the proposed scheme has been implemented. In the Fig. 8., Show logo, No show logo and the logo position options can be selected. Besides, after pressing the button of signal frame embedding, the PSNR (Peak Signal-to-Noise Ratio) can be calculated before and after embedding. The PSNR is defined as:

Perform the permuting operation on the scrambled watermark ws to obtain w p by w P ( x ' , y ' ) = ws ( x, y )

(3)

 x ' α  x (4)  y ' = TK  y  (mod N P )     for 0 ≤ x, y < N , N P is some integer with N P ≥ N

and α < ρ ( K ) . Step 3: Embedding







(7)

where f max means the maximum of the video gray level and 1 m −1 m −1 (8) MSE = ( 2 )∑ ∑ (α ij − β ij ) 2 m i =0 j =0 The PSNR of each original video and watermarked video are illustrate as the Table. 2. Then, The PSNR deviation between the original video and the watermarked video is defined as: | PSNRbe − PSNRae | (9) ε= × 100% PSNRbe where PSNRbe and PSNR ae are the PSNR value of video before embedding and after embedding. As shown in Table 2, and Fig. 9., after computing the average deviations of the eight videos, it can be found that the deviation is 0.28%. Because the value is so low that the technique influence the video quality is almost negligible and thus proved the technique is practical.

in relative coordinates; that is , we assume that ( x, y ) is at location (0,0) , and thus the motion vector is simply expressed as (u, v). Getting two dichotomy of the minimum MV (u + v) = even and (u + v) = odd from ME. Then, match up the two MV set, MV 0 and MV1 , with per pixel watermark. Such as:

MV1 = {(u , v) | (u + v)%2 = 1}

 2

f max  PSNR = 10 log 10  MSE 

In motion estimation terminology, the vector form ( x, y ) to ( x + u , y + v) is referred to as the Motion Vector (MV) associated with the macroblock at location ( x, y ) . Often, the motion vector is expressed

MV 0 = {(u , v ) | (u + v )%2 = 0}

(6)

(5)

The processes are shown as the following: B. Watermark Extracting

5. Conclusion

The extracting processes are illustrated as Fig. 5. The steps are shown as the following:

In this paper, an efficient watermark scheme on 548


2003/8/17~19, Kinmen, ROC

12th International Workshop on , 2001, pp. 825-829 [9]. Joan L. Mitchell, WilliamB. Pennebaker, Chad E. Fogg, and Didier J. LeGall, “MPEG Video Compression Standard, “Champman & Hall, 1996 [10]. V. Bhaskaran, and K. Konstantinides, Image and video compression standards, Kluwer Academic, 1997.

compressed domain for MPEG video streams is described. Embedding message into MV of ME is proposed. The technique of embedding the watermark wouldn’t increase the quantity of data but increase the quantity of the information. Because of the reason that the Motion Vector can be easily obtained by means of VLC decode process in the MPEG decode such that Motion of the Motion Estimation is employed for watermark embedding in the proposed scheme which does not require original video for embedded message (or watermark) retrieval. On the other hand, suppose the attack is attempted by altering the Motion Vector of watermark embedded video, meanwhile, the quality of the video will be affected as well. In other words, any attempts on altering watermark logo will also destroy the video such that the malicious falsification can be discouraged.

Table. 1. The video clips used for experiments. Video name

Video

Frame number

Bridge-close

2000

Bridge-far

2101

Highway

2000

Mobile

300

Paris

1065

Foreman

400

Carphone

382

Tempete

260

Reference [1]. T. T. Lu, L. L. Lee, and P. C. Chang, “A Key-based Image Watermarking System Using Subblock Composition in DCT Domain,” Proc. Multimedia Technology and Applications Conference 2001, pp. 157-163, Irvine, CA, Nov. 2001 [2]. S. F. Chang, and D. G. Messerchmitt, “Manipulation and Compositing of MC-DCT Compressed Video,” IEEE Journal on Selected Areas in Communications, Vol. 13, No.1, January 1995. [3]. R.G. van Schyndel, A.Z. Tirkel, and C.F. Osborne, “A Digital Watermark,” Image Processing, 1994. Proceedings. ICIP-94., IEEE International Conference , vol. 2, pp.86-90, 1994 [4]. F.M. Boland, J.J.K. O’Ruanaidh, and C. Dautzenberg, “ Watermarking Digital images for coyright protection, “Image Processing and its Applications, 1995, 5th International Conference on , 1995, PP. 326-330 [5]. Anatol.Z. Tirkel, Charles F. Osborne, and RonG.van Schyndel., “Image Watermarking-A Spread Spectrum Application, “Spread Specturm Techniques and Applications Proceedings, 1996,., IEEE 4th International Symposium on , vol. 2, 1996, pp.785-789 [6]. Adrian G. Bors and Ioannis Pitas, “Image Watermarking Using DCT Domain Constraints, “Image Processing, 1996. Proceedings., International Conference on , vol. 3 , 1996, pp.231-234 [7]. Bo Tao and Brandley Dickinson, “Adaptive Watermarking in the DCT Domain,” Acoustics, Speech, and Signal Processing, 1997. ICASSP-97, 1997 IEEE Internation Conference on , vol.4, 1997, pp.2985-2988 [8]. V. Cappellini, F. Bartolini, R. Caldelli, A. De Rosa, A. Piva, and M. Barni, “Robust Frame-based Watermarking for Digital Video, “Database and Expert Systems Applications, 2001. Proceedings. 549


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Fig. 2. Block diagram of an MPEG decoder.

Table. 2. The PSNR values and deviations of the original and watermarked video clips

MV0 ME

PSNR of original video

PSNR of watermarked video

PSNR Deviations

Bridge-close

46.29

46.22

0.15%

Bridge-far

45.72

45.67

0.11%

High-way

45.95

45.91

0.09%

Mobile

45.53

45.31

0.48%

Paris

45.93

45.67

0.57%

Foreman

45.64

45.59

0.11%

Carphone

45.74

45.66

0.17%

Temp-ete

45.48

45.23

0.55%

Video name

Logo[i ]

MV1

Permute

Scramble

Logo

Embedding

MV = {MV0 } + {MV1 } MV0 = {(u, v ) | (u + v)%2 = 0}

MVwm

MV1 = {(u, v) | (u + v)%2 = 1}

Fig. 3. The block diagram of watermark embedding processes

Embedding

i= 0

Average PSNR Deviation Rate：0.28 % No

Logo[ i ] = 1 Yes Regulator

PreProcessing

Frame Memory

+

DCT

VLC Encoder

Q

MVwm [i ] = MW0 [i ]

MVwm [i] = MV1 [i]

Buffer

IQ

IDCT

i++

+

Frame Memory

M.C.

i < ( w / 8 × h / 8)

Embedding

Permute

Scramble

Logo

End

M.E.

Fig. 4. The processes of Embedding

Fig. 1. Block diagram of an MPEG encoder

Step size Input data

VLC Decoder

Buffer

MV Q

Extracting

Depermute

Descramble

Logo

−1

IDCT

Logo

Descramble

Depermute

+

Extracting

Fig. 5. The Block Diagram of Watermark Extracting Processes Decoded data Buffer

Previous picture store Mux

12

+

0

Future picture store

Motion compensation

550


2003/8/17~19, Kinmen, ROC

Extract

i= 0

u[ i ], v[ i ]

No

( u[ i ] + v[ i ] ) % 2 = 0

Logo[ i ] = 1

Yes Log[ i ] = 0

Fig. 8. The watermark embedding function of the implemented application software.

i++

Yes

i < ( w / 8 × h / 8)

48

No

Original

Watermark

47

END

46

Fig. 6. The Extracting process

45 44 43 42 41 40 Bridge-

Bridge-far Highway

Mobile

Paris

Foreman

Carphone

Tempete

close

Fig. 9. The PSNR values and deviations of the original and watermarked video clips

Fig. 7. The MPEG encoder of the implemented application software

551