A Novel Scheme for Hybrid Digital Video Watermarking By Pat P. W. Chan Supervised by Michael R. Lyu 2/2/2004 Computer Science and Engineering Department The Chinese University of Hong Kong

Computer Science and Engineering Department, CUHK 2 Outline Introduction Review of Watermarking Schemes Proposed Video Watermarking Algorithms Possible Improvement Experimental Results Conclusion and Future Work

Computer Science and Engineering Department, CUHK 3 Introduction Watermarking is a concept of embedding a special pattern, watermark, into a document. Watermarking is a key process for the protection of copyright ownership of electronic data. In this presentation, we will focus on the video watermarking scheme. Watermarking Algorithm Watermarked Image Ì Stego-Image I Watermark W Secret / public key K

Computer Science and Engineering Department, CUHK 4 Introduction Video watermarking is challenging Video watermarking introduces some issues not present in image watermarking. Due to large amounts of data and inherent redundancy between frames, video signals are highly susceptible to pirate attacks, including frame averaging, frame dropping, frame swapping, statistical analysis, etc. However, the currently proposed algorithms do not solve these problems effectively.

Computer Science and Engineering Department, CUHK 5 Introduction A novel hybrid blind digital video watermarking scheme with scrambled watermarks will be introduced. The features of the video watermarking algorithm are: Our scheme first embeds different parts of a single watermark into different scenes of a video ; Our video watermarking algorithm is robust against the attacks of frame dropping, averaging and statistical analysis; Apply a hybrid approach to form a super watermarking scheme that can resist to most of the attacks; To increase robustness of the scheme, the watermark is refined by the error correcting code, while the correcting code is embedded as a watermark in the audio channel; It allows blind retrieval of embedded watermark; The watermark is perceptually invisible.

Computer Science and Engineering Department, CUHK 6 Review of Watermarking

Computer Science and Engineering Department, CUHK 7 Review of Video Watermarking Least Significant Bit Modification Correlation- Based Techniques m-frame Spread Spectrum Discrete Cosine Transform (DCT) Discrete Wavelet Transform (DWT) Discrete Fourier Transform (DFT) Radon Transform Mpeg-4 Object-based Mpeg-2 Block- based

Computer Science and Engineering Department, CUHK 8 Comparison between different watermarking schemes Frequency domain watermarking is much more robust None of the currently proposed scheme is robust to all kind of attacks

Computer Science and Engineering Department, CUHK 9 Watermarking Scheme Overview

Computer Science and Engineering Department, CUHK 10 Watermarking Scheme Video Preprocess Watermark Preprocess Video Watermark Embedding Watermark Extraction

Computer Science and Engineering Department, CUHK 11 Mark with m1 Mark with m3 Mark with m7 Mark with m0 Scene change occur Video frames are transformed to wavelet domain. Perform scene change detection. Each scene is embedded with the same watermark, so it can prevent attackers from removing the watermark by frame dropping. Different watermarks used for successive different scene can prevent attackers from colluding with frames from completely different scenes. Video Preprocess: DWT & Scene Change Detection

Computer Science and Engineering Department, CUHK 12 Watermark Preprocess Scale the watermark to a particular size with the following equations 2 n ≦ m, n>0 p + q = n, p and q > 0 Size of image = 64˙2 p X 64˙2 q Divide the image into 2 n small images with size 64 X 64 m -- # of scene change of the video m=10, n=3, p=1, q=2

Computer Science and Engineering Department, CUHK 13 Watermark Preprocess Preprocessed watermark m 0 -m 7 Original watermark Encrypted watermark m’ 0

Computer Science and Engineering Department, CUHK 14 Video Watermark Embedding if W j = 1, Exchange C i with max (C i, C i+1, C i+2, C i+3, C i+4 ) else Exchange C i with min (C i, C i+1, C i+2, C i+3, C i+4 ) LL, HH coefficients are not watermarked

Computer Science and Engineering Department, CUHK 15 Video Watermark Extraction if WC i > median (WC i, WC i+1, WC i+2, WC i+3, WC i+4 ) EW j = 1 else EW j = 0 Watermarked video frame Original video frame Extracted Watermark Recovered Watermark

Computer Science and Engineering Department, CUHK 16 Video Watermarking Scheme Scrambled Watermark in different Scene Change GA-based Optimization Audio Watermark Aided Approach Hybrid Watermarking Approach Possible Improvement

Computer Science and Engineering Department, CUHK 17 Watermarking Scheme Overview

Computer Science and Engineering Department, CUHK 18 Error correcting code is extracted from the watermark image Embedded in audio channel as an audio watermark This watermark can provided the error correction and detection capability for the video watermark Audio Watermark Average

Computer Science and Engineering Department, CUHK 19 Audio Watermark Embedding Spread-Spectrum Watermarking Modulated Complex Lapped Transform (MCLT)

Computer Science and Engineering Department, CUHK 20 Watermarked Frame & Wave Watermarked video frame and waveOriginal video frame and wave

Computer Science and Engineering Department, CUHK 21 Watermark Extraction Video is split into video stream and audio stream. Watermarks are extracted separately by audio watermark extraction and video watermark extraction. Then the extracted watermark undergoes refining process

Computer Science and Engineering Department, CUHK 22 Watermark Refining Error correcting codes are extracted from the audio stream The video watermark extracted is refined by this information with the following equation RW ij is refined watermark EW ij is the extracted video watermark Avg k is the extracted audio watermark, k is the k th block of the average image, (i, j) is coordinate of the video watermark, f:g is a ratio of importance of the extracted video watermark to the audio watermark.

Computer Science and Engineering Department, CUHK 23 Video Watermarking Scheme Scrambled Watermark in different Scene Change GA-based Optimization Audio Watermark Aided Approach Hybrid Watermarking Approach Possible Improvement

Computer Science and Engineering Department, CUHK 24 Hybrid Approach with Different Watermarking Scheme No watermarking scheme found in the current technologies is capable of resisting to all watermark attacks. Hybrid approach is one of the solutions. It can be classified into two types: Independent watermarking schemes Dependent watermarking schemes

Computer Science and Engineering Department, CUHK 25 Independent Hybrid Watermarking Scheme The watermarks are embedded into the frame with different watermarking scheme in various domain. The schemes are not affecting each other. There are two approaches to combine the schemes:

Computer Science and Engineering Department, CUHK 26 Independent Hybrid Watermarking Scheme When there is an attack on the watermarked video, different watermarking schemes are resistant against various attacks. Consequently, some parts of the watermark still survive after the attack. This approach enhances the chance of survival under several attacks.

Computer Science and Engineering Department, CUHK 27 Dependent Hybrid Watermarking Scheme The same watermark is embedded serially in a frame with different watermarking scheme in various domains. For each frame, four different watermarking schemes are applied. DWT  DFT  DCT  Radon Transform

Computer Science and Engineering Department, CUHK 28 Experimental Setup VirtualDub -- a video capture/processing utility ( A video clip with 1526 frames of size 352 X 288 A DWT-based watermarking scheme for comparison Experiments: Experiment with Frame Dropping Experiment with Frame Averaging and Statistical Analysis Experiment with Lossy Compression Experiment with StirMark 4.0 Measurement, Normalized Correlation:

Computer Science and Engineering Department, CUHK 29 Experiment with Frame Dropping As a video contains a large amount of redundancies between frames, it may suffer attacks by frame dropping. This experiment is aimed to examine the robustness of the scheme under attack by frame dropping.

Computer Science and Engineering Department, CUHK 30 Experiment with Frame Dropping When frames are dropped, the error is only introduced to a corresponding small part of the watermark. The performance of the scheme is significantly improved by combining with an audio watermark, especially when the dropping rate of video frame is high. When the dropping rate increases, the error of the extracted watermark is increased. The error correcting code from the audio watermark provides information to correct the error and overcome the corrupted part of the video watermark

Computer Science and Engineering Department, CUHK 31 Experiment with Frame Averaging and Statistical Analysis Frame averaging and statistical analysis is another common attack to the video watermark. When attackers collect a number of watermarked frames, they can estimate the watermark by statistical averaging and remove it from the watermarked video Scenario of statistical averaging attack

Computer Science and Engineering Department, CUHK 32 Experiment with Frame Averaging and Statistical Analysis The watermarked video is statistically analyzed by colluding a number of video frames and the watermarks are extracted and NC values are obtained. The identical watermark used within a scene can prevent attackers from taking the advantage of motionless regions in successive frames and removing the watermark by comparing and averaging the frames statistically. Independent watermarks used for successive, but different scenes can prevent attackers from colluding with frames from completely different scenes to extract the watermark.

Computer Science and Engineering Department, CUHK 33 Experiment with Lossy Compression The performance of the scheme is significantly improved by combining with audio watermark, especially when the quality factor of MPEG is low. When the quality factor of MPEG is low, the error of the extracted watermark is increased and the watermark is damaged significantly. As the error correcting code is provided from the audio watermark, it can survive the attack by lossy compression which is applied to the video channel. The performance of the scheme is also improved by hybrid approach with different watermarking schemes. When compression is applied to the watermarked video, the watermark embedded in the video with DCT-based watermarking scheme is survived. Therefore, there is at least one forth of the watermark can be retrieved from the video.

Computer Science and Engineering Department, CUHK 34 Experiment with StirMark 4.0 The pervious experiments show the effectiveness of the proposed scene-based watermarking scheme when the specification of attacks to video’s properties is applied, including frame dropping, averaging and statistical analysis. StirMark 4.0 is a benchmark to examine the robustness of the watermarking scheme against attacks by image processing.

Computer Science and Engineering Department, CUHK 35 Experiment with StirMark 4.0

Computer Science and Engineering Department, CUHK 36 Video Watermarking Scheme Scrambled Watermark in different Scene Change GA-based Optimization Audio Watermark Aided Approach Hybrid Watermarking Approach Possible Improvement

Computer Science and Engineering Department, CUHK 37 Problem Modeling Scene based video watermarking technique Embedding positions within a video are simulated as chromosomes Find the best positions to embed watermark Good quality Robust against attacks Mean Absolute Difference (MAD) to measure the objective function values during optimization

Computer Science and Engineering Department, CUHK 38 System Architecture Watermark Extraction Original Video Watermarked Image Watermark Image Referenced Watermark Scene Change detection Embedding (Polarity Reversing) IDWT GA-based Optimization Process Scene change detection Correlation Mechanisms Watermarked Image Extracted Watermark The GA-based watermarking algorithm

Computer Science and Engineering Department, CUHK 39 Chromosome encoding Positions for each part of watermark; i th watermark to be embedded into which scene change can be defined as: The last two constraints imply: In a video, scenes which have been embedded should not be embedded again. There at least two scene changes M = 8 {(Xi )| 0 ≦ Xi 1} X0X0 X2X2 X4X4 X6X6 X1X1 X3X3 X5X5 X7X7

Computer Science and Engineering Department, CUHK 40 The GA-based optimization process Replace illegal chromosomes Random production of N initial parent chromosomes Embe d tests Calculating objective function values of n parents Producing N children chromosomes by random Randomly mating Exchange parts of chromosomes Mutation Discarding illegal children Selecting N chromosomes as parents of the next generation Reproduction Crossover Mutation Rate=1/100

Computer Science and Engineering Department, CUHK 41 Conclusion Video watermarking is needed since copyright protection is essential. A hybrid digital video watermarking scheme with scrambled watermark is proposed. Other possible improvements are proposed and verified through different experiments. Our approach cultivates an innovative idea in embedding different parts of a watermark according to scene changes, in embedding its error correcting codes as an audio watermark, and in applying hybrid approaches to enhance the scheme. Although the concept is quite simple, this approach is never explored in the literature, and its advantages are clear and significant. The effectiveness of this scheme is verified through a number of experiments.

Computer Science and Engineering Department, CUHK 42 Future Direction There are several approaches to improve the watermarking scheme Implement the GA-based approach Make use of the information from the video, such as time information to increase the robustness of the watermark.