SCYR 2010 - 10th Scientific Conference of Young Researchers – FEI TU of Košice
Video watermarking based on DWT 1
Peter GOČ-MATIS, Tomáš KANÓCZ, Radovan RIDZOŇ, Dušan LEVICKÝ
1
Dept. of Electronics and Multimedia Communications, FEI TU of Košice, Slovak Republic
1
[email protected],
[email protected],
[email protected],
[email protected]
Abstract— This paper describes a new method for video watermark embedding, using the knowledges already available from watermark embedding into digital static pictures. The watermark is embedded in transformed domain using Discrete Wavelet Transform (DWT). This paper also describes experiments conducted on the proposed watermark embedding method. The goal of these experiments was the test the robustness of the method presented in the paper against several watermarking attacks. Keywords— Watermarks in video, attacks, transformation domain, DWT.
I.
INTRODUCTION
In recent years, there has been a rapid progress in the digital multimedia processing as well as in the internet technologies. Analog form of multimedia was practically replaced by the digital form of multimedia almost in the all the areas of the human life. Digital multimedia has brought many advantages in comparison to the analog form of multimedia. The main advantages of digital multimedia form are easy processing and storage, compression and better noise resistance. Digital multimedia also has brought disadvantages. For example easy copying without quality degradation of copied multimedia. The copies are identical with the original multimedia and they can be transmitted over the worldwide internet. This illegal sharing is wrong for authors and distributors of the multimedia because they lose income. Also with the progress of the peer-to-peer networks and fast internet the problems with the author’s rights and copyright protection were established. Approaches for multimedia content protection can be divided into two main groups [1], [2]: - multimedia content protection during transmission, - multimedia content protection after transmission. Solution of multimedia content protection during transmission is the use of cryptographic methods which are based on content encryption of multimedia. This paper deals with multimedia content protection after the transmission using digital watermarking.
II. DIGITAL WATERMARKING Digital watermarking is a technique of embedding additional information into all kind of digital multimedia,
whereby this data modification should be imperceptible [3], [4]. The embedded watermark carries information about author or distributor of multimedia and also provides data integrity check. The form of embedded watermark may be symbol or number sequences, image information (logo) or segment of vocal signals. It depends on an application. The three basic parameters of digital watermarking are robustness, perceptual transparency and capacity [5]. A. Digital watermarking in video The digital watermarking methods in video can be divided into three main groups [6]: - methods based on watermarking in still images, - methods based on video-time dimension, - methods based on video compression standards. B. Attacks on digital watermarks in video Attacks on video watermarks represent all intended and unintended operations, which are executed by attacker with a goal to remove watermark from marked multimedia and get possession of unmarked content. Specific attacks applied to video are frame dropping, frame swapping, frame averaging, statistical analysis and unintended attacks for example compression of video sequences and affine transformations [7]. This paper focuses especially on the unintended attack of video compression and also on the intended attacks which are frame averaging, frame dropping and frame swapping.
III. THE PROPOSED WATERMARKING METHOD The proposed method which performs watermark embedding into video content is based on Discrete Wavelet Transform (DWT). Reasons for the usage of this orthogonal transformation are its good results in applications which deal with image processing. The described method is based on watermarking in still images. A. The watermark embedding block Block of watermark embedding performs: video content loading, decomposition to still images, wavelet decomposition, watermark insertion, wavelet reconstruction and reconstruction the video content from still images. Inputs of this block are original video and embedded watermark. In Fig. 1 the watermark embedding block is shown.
SCYR 2010 - 10th Scientific Conference of Young Researchers – FEI TU of Košice
Fig. 3 Watermark extraction block
Fig. 1 Watermark embedding block
Six video sequences with different dynamic properties were used in experiments. These were (Dynamic – D, Mezzo Dynamic – MD and Lightly Dynamic – LD). Resolution of all video sequences is QCIF 352x288 pixels. Videos are cut into 10 seconds long sequences and the frame rate is 25 fps. Video sequences are uncompressed and they are in true color mode. The embedded watermark is a binary image of a squarepoint star. This watermark is shown in the Fig. 2. The size of watermark depends on the resolution of original video and also depends on the level of wavelet decomposition. In our experiments size of the embedded watermark is 88 x 72 pixels.
The inputs of the watermark extraction process are original video and marked video. The process of watermark extraction can be described by the following equation: T (2) .WEXT (i, j ) APK DWT (i, j ) APK DWT (i, j ) where
T APK DWT (i, j ) and APK DWT (i, j ) represent block
of marked approximation coefficients from the tested and original video. WEXT (i, j ) is the extracted binary watermark and α (alpha) is the power of the embedded watermark. After extraction process elimination of factor α which gives information about robustness of watermark is necessary. Watermark extraction is performed from a random frame of the marked video and also from every of color components (R, G, B).
IV. EXPERIMENTAL RESULTS Fig. 2 Embedded watermark
Proposed method performs watermark embedding into coefficients, which are obtained after two dimensional Discrete Wavelet Transform of second level. Watermark is embedded into approximation coefficients. The process of watermark embedding can be described by the following equation: W (1) APK DWT (i , j ) APK DWT (i, j ) .W (i, j )
APK WDWT (i, j ) and APK DWT (i, j ) represent block of marked and original approximation coefficients. W (i, j ) where
is embedded binary watermark and α (alpha) is the power of the embedded watermark. We can adjust the required robustness with this α factor. In proposed method the α factor is adjusts to values: 5, 7, 10 and 15. In the proposed method watermark is embedded into all frames of original video sequences and also every color components (R, G, B) are marked. This approach increase robustness of embedded watermark against attacks like frame dropping, frame swapping and frame averaging.
The proposed method of watermarking was tested against unintended attacks MPEG standard compressions. Next attacks were frame averaging, frame dropping and frame swapping. These attacks are specific for a video and most used. The quality of the extracted watermark after the attacks was judge by objective aspects, which were Mean Square Error (MSE), Peak Signal/Noise Ratio (PSNR) and also Bit Match (BM). The influence of the embedded watermark into approximation coefficients was measured by PSNR and MSE and values are presented in Table I. When the power of watermark α is increased the PSNR is decrease. The α factor is linked with robustness. the power of the watermark α
video
1. D 2. 1. MD
B. The watermark extraction block This block performs extraction of the watermark from marked approximation coefficients in the video. The process of the watermark extraction is shown in the Fig. 3.
2. 1. LD 2.
α = 15 α = 10
α=7
α=5
PSNR[dB]
36.09
41.17
42.11
48.13
MSE
15.99
4.97
3.99
0.99
PSNR[dB]
36.09
41.16
42.11
48.13
MSE
15.98
4.98
3.99
0.99
PSNR[dB]
36.09
41.17
42.11
48.13
MSE
15.98
4.97
4.00
1.00
PSNR[dB]
36.14
41.22
42.13
48.18
MSE
15.82
4.91
3.98
0.99
PSNR[dB]
36.11
41.17
42.12
48.13
MSE
15.94
4.97
3.99
0.99
PSNR[dB]
36.09
41.18
42.11
48.13
15.98 4.96 3.99 TABLE I PSNR AND MSE COMPARISON
0.99
MSE
SCYR 2010 - 10th Scientific Conference of Young Researchers – FEI TU of Košice
First attack was lossy compression. Six video sequences Dynamic (D), Mezzo dynamic (MD) and Lightly Dynamic (LD) were compressed by MPEG-1, MPEG-2, MPEG-4 and MJPEG. After compression watermark is extracted from a random frame and also from every color components (R, G, B). Finally watermark which is used for bit match calculation is averaged from the watermarks from components R, G and B. The results of the watermarks extraction after lossy compression are shown in the TABLE II, TABLE III, TABLE IV and TABLE V. Bit Match is the quantity of identical pixels in the original and extracted watermarks. As can be seen from the tables the proposed method which performs watermark embedding into approximation coefficients is most robust against compression by MJPEG standard, next are MPEG-2, MPEG-1 and method is least robust against compression by MPEG-4. the power of the watermark α Video
D MD LD
α =5
α =7
α = 10
α = 15
BM[%]
BM[%]
BM[%]
BM[%]
1.
87.42
95.34
98.22
99.72
2.
87.03
96.61
98.82
99.92
1.
88.38
96.21
98.99
99.78
2.
86.19
95.17
97.13
98.99
1.
87.78
96.56
98.60
99.70
the power of the watermark α Video
D MD LD
α =5
α =7
α = 10
α = 15
BM[%]
BM[%]
BM[%]
BM[%]
1.
80.08
87.31
91.07
96.26
2.
75.88
83.54
85.78
93.73
1.
83.46
89.50
95.04
98.45
2.
81.36
89.03
91.98
96.76
1.
83.21
88.67
93.83
97.95
2.
83.79 91.62 97.08 99.15 TABLE V THE QUALITY OF THE EXTRACTED WATERMARK AFTER MPEG-4 COMPRESSION.
The results of the watermarks extraction after frame averaging are shown in the TABLE VI. The same watermark is embedded into all frames and the power of the watermark is α = 7. As can be seen from the table quality of extracted watermarks depends on dynamic properties of video. Extraction is the best from lightly dynamic movie because there are small changes of approximation coefficients which give information about heavy features of image. When the attacker averaged more than three frames, the quality of this frame is much degraded. Degradation of averaged frames is shown in the Fig. 4.
2.
89.17 97.57 99.04 99.84 TABLE II THE QUALITY OF THE EXTRACTED WATERMARK AFTER MJPEG COMPRESSION.
the power of the watermark α Video
D MD LD
α =5
α =7
α = 10
α = 15
BM[%]
BM[%]
BM[%]
BM[%]
1.
82.75
90.66
97.38
99.45
2.
82.77
91.89
97.84
99.64
1.
82.53
90.69
97.73
99.62
2.
85.13
93.07
97.87
99.57
1.
82.88
90.34
97.01
99.68
Fig. 4 Five averaged frames
the number of averaged frames
2.
84.01 91.92 97.90 99.68 TABLE III THE QUALITY OF THE EXTRACTED WATERMARK AFTER MPEG-2 COMPRESSION.
Video
D the power of the watermark α Video
D MD LD
α =5
α =7
α = 10
α = 15
BM[%]
BM[%]
BM[%]
BM[%]
1.
83.63
89.32
94.00
97.11
2.
77.16
86.03
88.99
95.25
1.
82.59
88.26
94.60
98.61
2.
85.28
92.17
96.31
98.53
1.
83.18
89.69
96.65
99.37
2.
84.03 91.08 96.97 99.26 TABLE IV THE QUALITY OF THE EXTRACTED WATERMARK AFTER MPEG-1 COMPRESSION.
MD LD
2
3
5
7
BM[%]
BM[%]
BM[%]
BM[%]
1.
61.85
57.77
54.47
53.90
2.
64.76
62.07
60.29
59.56
1.
79.78
74.57
70.25
64.11
2.
72.74
67.68
65.97
66.13
1.
96.56
94.87
90.39
82.17
2.
99.56 98.39 96.42 95.11 TABLE VI THE QUALITY OF THE EXTRACTED WATERMARK AFTER FRAME AVERAGING.
Last attacks were frame dropping and frame swapping. The method is robust against these attacks, because the watermark is embedded into all frames of original video. When the potential attacker dropped one or more frames, watermark from another frame can be extracted.
SCYR 2010 - 10th Scientific Conference of Young Researchers – FEI TU of Košice
V. CONCLUSION Experimental results shown, that the proposed watermarking method based on DWT is robust against the unintended attacks like lossy compression. Method is also robust against specific attacks on the video like frame swapping, frame dropping and frame averaging. The increasing of the robustness against attacks can be achieved by α factor increasing. Experimental results highly depend on the dynamic properties of video. When the video content is less dynamic the extraction of watermark is better. Primary disadvantages of the proposed methods are computing time and the need of the original video in the watermark extraction process.
ACKNOWLEDGEMENTS The work presented in this paper was supported by Ministry of Education of Slovak republic VEGA Grant No. 1/0065/10, INDECT Grant (7th Research Frame Programme no. 218086) and Centre of Information and Communication
Technologies for Knowledge Systems (project number: 26220120020) supported by the Research & Development Operational Programme funded by the ERDF.
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