Liyun Wang

Real-Time Compressed- Domain Video Watermarking Resistance to Geometric Distortions

A proposed real-time video watermarking scheme is transparent and robust to geometric distortions, including rotation with cropping, scaling, aspect ratio change, frame dropping, and swapping.

Robust video watermarking based on affine invariant regions in the compressed domain

This paper proposes a novel robust video watermarking scheme based on local affine invariant features in the compressed domain. This scheme is resilient to geometric distortions and quite suitable for DCT-encoded compressed video data because it performs directly in the block DCTs domain. In order to synchronize the watermark, we use local invariant feature points obtained through the Harris-Affine detector which is invariant to affine distortions. To decode the frames from DCT domain to the spatial domain as fast as possible, a fast inter-transformation between block DCTs and sub-block DCTs is employed and down-sampling frames in the spatial domain are obtained by replacing each sub-blocks DCT of 2x2 pixels with half of the corresponding DC coefficient. The above-mentioned strategy can significantly save computational cost in comparison with the conventional method which accomplishes the same task via inverse DCT (IDCT). The watermark detection is performed in spatial domain along with the decoded video playing. So it is not sensitive to the video format conversion. Experimental results demonstrate that the proposed scheme is transparent and robust to signal-processing attacks, geometric distortions including rotation, scaling, aspect ratio changes, linear geometric transforms, cropping and combinations of several attacks, frame dropping, and frame rate conversion.

Robust localized image watermarking based on invariant regions

The robustness of the localized watermarking methods mainly depends on the robustness of the feature locating the watermark. Based on the mean luminance of the disk, a rotation and scale invariant feature extraction algorithm is proposed. A theoretical verification of the rotation and scale invariance of extracted feature points in the continuous image is further performed. The extracted feature points are used to construct rotation and scale invariant circular regions, where the watermark is embedded after affine normalization. Experimental results show that the constructed regions fit the watermarking applications much better than those in previous feature-based watermarking schemes from the aspect of robustness against common attacks including filtering, JPEG compression, cropping, rotation and scaling, and the proposed localized image watermarking scheme has better robustness than previous feature-based watermarking schemes against common signal process and geometrical attacks while maintaining imperceptibility.

Fine-search for image copy detection based on local affine-invariant descriptor and spatial dependent matching

Copies are somehow a subset of near-duplicates, but the approaches extensively employed in near-duplicate retrieval only obtain rough and imprecise query results. Therefore a fine-search scheme is proposed to refine these rough results and attempt to completely detect the real copies accurately. This scheme first employs a local affine-invariant descriptor based on polar-mapping and discrete Fourier transform. Then a spatial dependent matching method is proposed combining nearest neighbor distance ratio with the spatial relationships among the local features. Experimental results demonstrate that the employed descriptor is more robust, distinctive and suitable for copy detection in comparison with the SIFT descriptor. And the spatial dependent matching is able to improve the recall and precision, and lower the false positives and ambiguities.

Real-time video watermarking scheme resistant to geometric distortions

A real-time video watermarking scheme against geometric distortions is proposed for DCT-encoded compressed video data. The full DCT coefficients have proven to be invariant to scaling and local geometric attacks. Therefore, watermarks are embedded into watermark minimal sequences (WMS) by modulating the low-frequency full DCT coefficients. To meet the requirement of real-time performance, a fast intertransformation is employed to construct full DCT directly from block DCTs. The modified differences of full DCT coefficients are inversely transformed to the differences of block DCT coefficients that are subsequently added to the original block DCTs to generate the WMS. To resist various video format conversions, the watermark detection is performed in spatial domain. This does not affect the real-time performance because the watermark detection need not re-encode the frames into compressed data, and compressed video can be easily decoded fast by employing some codec or decoding chips. Furthermore, the proposed scheme can resist rotation attacks by employing a rotation compensation strategy. Experimental results demonstrate that the proposed scheme is real-time, transparent, and robust to signal distortions, geometric distortions including rotation, scaling, aspect ratio change, linear geometric transforms, cropping and combination attacks, frame dropping and swapping, file format conversion, as well as camcorder recording.

PM-DFT: A New Local Invariant Descriptor Towards Image Copy Detection

Currently, global-features-based image copy detection is vulnerable to geometric transformations like cropping, shift, and rotations. To resolve this problem, some algorithms based on local descriptors have been proposed. However, the local descriptors, which were originally designed for object recognition, are not suitable for copy detection because they cause the problems of false positives and ambiguities. Instead of relying on the local gradient statistic as many existing descriptors do, we propose a new invariant local descriptor based on local polar-mapping and discrete Fourier transform. Then based on this descriptor, we propose a new framework of copy detection, in which virtual prior attacks and attack weight are employed for training and selecting only a few robust features. This consequently improves the storage and detection efficiency. In addition, it is worth noting that the feature matching takes the locations and orientations of interest points into consideration, which increases the number of matched regions and improves the recall. Experimental results show that the new descriptor is more robust and distinctive, and the proposed copy detection scheme using this descriptor can substantially enhance the accuracy and recall of copy detection and lower the false positives and ambiguities.

Low-complexity video watermarking scheme resisting geometric distortions

A low-complexity video watermarking scheme against geometric distortions is proposed for DCT-encoded compressed video data. The full DCT coefficients have proven to be invariant to scaling and local geometric attacks. Therefore the watermark is embedded into frames by modifying the low-frequency full DCT coefficients. To meet the requirement of real time performance, a fast inter-transformation is employed to construct full DCTs directly from block DCTs. The experimental results show that the proposed scheme is transparent and robust to signal processing attacks, lots of geometric distortions and frame dropping.

Robust embedding and detection for multimedia fingerprinting

For the fingerprinting system, both collusion attacks and geometrical distortions are very harmful to its performance on tracing traitors. In this paper, we propose a novel multimedia fingerprinting scheme for images and videos with high robustness to geometrical distortions as well as collusion attacks. First of all, the full inverse DCT (IDCT) transform is applied on the fingerprint, and then the result is embedded into the space domain of the multimedia. This process is equivalent to embedding the fingerprint in the full DCT domain directly. Furthermore, the computing cost decreases significantly. In the detection, we propose the image correction method based on the scale invariant features transform (SIFT) feature for recovering suspicious multimedia suffering from geometrical distortions. With the proposed fingerprint embedding and robust detection, the experimental results show that the system not only resists a variety of geometrical distortions, but also can resist collusion attacks.

A real-time robust digital fingerprinting algorithm

As a branch of digital watermarking, digital fingerprinting, a technology being used to trace the leakage of the multimedia content, has become a hot topic in recent years. As users increase, a practical fingerprinting system has the following requirements, such as robustness, collusion-resistance, and realtime processing. To lower the computational complexity of fingerprint embedding, we propose a spatial-domain based large scale real-time embedding algorithm in this paper. At first, the fingerprints are converted into an embedding template. And then, the template is superimposed to the host signal directly in spatial domain. The proposed embedding algorithm is simple and efficient, and it could be used in various types of multimedia data. Though the fingerprint template is added in spatial domain, the efficacy is the same as in DFT (Discrete Fourier transform) domain. Therefore, the robustness can be maintained. Comparing with the traditional algorithms in transform-domain, the proposed algorithm performs much better in real-time processing. This is because that no transformations are needed for video frames or images during the process of fingerprint embedding. The experimental results show that the proposed algorithm has many advantages in real-time processing and robustness.