Hindawi Publishing Corporation Advances in Multimedia Volume 2012, Article ID 973418, 19 pages doi:10.1155/2012/973418 Research Article 2D+t Wavelet Domain Video Watermarking Deepayan Bhowmik and Charith Abhayaratne Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield S1 3JD, UK Correspondence should be addressed to Charith Abhayaratne, c.abhayaratne@sheffield.ac.uk Received 29 November 2011; Revised 20 January 2012; Accepted 21 January 2012 Academic Editor: Chong Wah Ngo Copyright © 2012 D. Bhowmik and C. Abhayaratne. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A novel watermarking framework for scalable coded video that improves the robustness against quality scalable compression is presented in this paper. Unlike the conventional spatial-domain (t+2D) water-marking scheme where the motion compensated temporal filtering (MCTF) is performed on the spatial frame-wise video data to decompose the video, the proposed framework applies the MCTF in the wavelet domain (2D + t) to generate the coefficients to embed the watermark. Robustness performances against scalable content adaptation, such as Motion JPEG 2000, MC-EZBC, or H.264-SVC, are reviewed for various combinations of motion compensated 2D + t + 2D using the proposed framework. The MCTF is improved by modifying the update step to follow the motion trajectory in the hierarchical temporal decomposition by using direct motion vector fields in the update step and implied motion vectors in the prediction step. The results show smaller embedding distortion in terms of both peak signal to noise ratio and flickering metrics compared to frame-by-frame video watermarking while the robustness against scalable compression is improved by using 2D + t over the conventional t + 2D domain video watermarking, particularly for blind watermarking schemes where the motion is estimated from the watermarked video. 1. Introduction Several attempts have been made to extend the image water- marking algorithms into video watermarking by using them either on frame-by-frame basis or on 3D decomposed video. The initial attempts on video watermarking were made by frame-by-frame embedding [1–4], due to its simplicity in implementation using image watermarking algorithms. Such watermarking algorithms consider embedding on selected frames located at fixed intervals to make them robust against frame dropping-based temporal adaptations of video. In this case, each frame is treated separately as an individual image; hence, any image-watermarking algorithm can be adopted to achieve the intended robustness. But frame-by-frame watermarking schemes often perform poorly in terms of flickering artefacts and robustness against various video pro- cessing attacks including temporal desynchronization, video collusion, video compression attacks, and so forth. In order to address some of these issues, the video temporal dimen- sion is exploited using different transforms, such as discrete Fourier transform (DFT), discrete cosine transform (DCT), or discrete wavelet transform (DWT). These algorithms decompose the video by performing spatial 2D transform on individual frames followed by 1D transform in the temporal domain. Various transforms are proposed in 3D decomposed watermarking schemes, such as 3D DFT domain [5], 3D DCT domain [6], and more popularly multiresolution 3D DWT domain watermarking [7, 8]. A multilevel 3D DWT is performed by recursively applying the above-mentioned pro- cedure on low-frequency spatiotemporal subband. Various watermarking methods similar to image watermarking are then applied to suitable subbands to balance the impercep- tibility and robustness. 3D decomposition-based methods overcome the issues like temporal desynchronization, video format conversion, and video collusion. However, such naive subband decomposition-based embedding strategies with- out considering motion element of the sequence during watermark embedding often result in unpleasant flickering visual artefacts. The amount of flickering in watermarked sequences varies according to the texture, colour, and motion characteristics of the video content as well as the watermark strength and the choice of frequency subband used for