C.V. Serdean

Combating geometrical attacks in a DWT based blind video watermarking system

This paper describes a high capacity blind video watermarking system invariant to geometrical attacks such as shift, rotation, scaling and cropping. A spatial domain reference watermark is used to obtain invariance to geometric attacks by employing image registration techniques to determine and invert the attacks. A second, high capacity watermark, which carries the data payload, is embedded in the wavelet domain according to a human visual system (HVS) model. This is protected by a state-of-the-art error correction code (turbo code). The proposed system is invariant to scaling up to 180%, rotation up to 70/spl deg/ and arbitrary aspect ratio changes up to 200% on both axes. Furthermore, the system is virtually invariant to any shifting, cropping, or combined shifting and cropping.

Adding robustness to geometrical attacks to a wavelet based, blind video watermarking system

This paper describes a high capacity blind video watermarking system invariant to geometrical attacks such as shift, rotation, scaling and cropping. A spatial domain reference watermark is used to obtain invariance to geometric attacks by employing image registration techniques to determine and invert the attacks. A second, high capacity, watermark, which carries the data payload, is embedded in the wavelet domain according to a human visual system (HVS) model. This is protected by a state-of-the-art error correction code (turbo code). For a false detection probability of 10/sup -8/, the proposed system is invariant to scaling up to 180%, rotation up to 70/spl deg/, and arbitrary aspect ratio changes up to 200% on both axes. Furthermore, the system is virtually invariant to any shifting, cropping, or combined shifting and cropping attack, and it is robust to MPEG-2 compression as low as 2-3 Mbps.

Stereo Correspondence Matching Using Multiwavelets

this paper presents a novel multiwavelet-based stereo correspondence matching technique. A multiwavelet transform is first applied to a pair of stereo images to decorrelate the images into a number of approximation (baseband) and detail subbands. Information in the basebands is less sensitive to shift variability of the multiwavelet transform. Basebands of each input image carry different spectral content of the image. Therefore, using the basebands to generate the disparity map is likely to produce more accurate results. A global error energy minimization technique is employed to generate a disparity map for each baseband of the stereo pairs. Information in the resulting disparity maps is then combined using a Fuzzy algorithm to construct a dense disparity map. A filtering process is finally applied to smooth the disparity map and reduce its erroneous matches. Middlebury stereo test images are used to generate experimental results. Results show that the proposed technique produces smoother disparity maps with less mismatch errors compared to applying the same global error energy minimization technique to wavelet transformed image data.

Limits of error correction coding in video watermarking

The paper discusses the limits of error correction coding for spread spectrum-based video watermarking. The error correction code has as input the watermark data bits and as output the values which will be scaled and used to modify the video pixels (transform coefficients). The data rate of the watermark can increase only at the expense of increasing code rate. Theoretically, the scheme is seen as a communication channel with Gaussian additive noise interference. Shannons (ideal) spherical codes are used as the error correcting code to calculate the minimum signal to noise ratio (SNR) necessary for a coding scheme with a given block length to achieve a given error probability. This limit is different from Shannons asymptotic limit, which is valid for infinite block lengths and zero error probability. In practice, in order to verify the Gaussian channel assumption, the error correction code is a concatenation of codes, of which the innermost is a repetition code. Several practical codes of different length and rates, such as turbo codes and BCH codes are investigated and their performance compared to that of the ideal code of the same size. The compromise block length/code rate is investigated for several marking schemes and attacks.