Radu Ovidiu Preda

Robust wavelet-based video watermarking scheme for copyright protection using the human visual system

The development of the information technology and computer networks facilitates easy duplication, manipulation, and distribution of digital data. Digital watermarking is one of the proposed solutions for effectively safeguarding the rightful ownership of digital images and video. We propose a public digital watermarking technique for video copyright protection in the discrete wavelet transform domain. The scheme uses binary images as watermarks. These are embedded in the detail wavelet coefficients of the middle wavelet subbands. The method is a combination of spread spectrum and quantization-based watermarking. Every bit of the watermark is spread over a number of wavelet coefficients with the use of a secret key by means of quantization. The selected wavelet detail coefficients from different subbands are quantized using an optimal quantization model, based on the characteristics of the human visual system (HVS). Our HVS-based scheme is compared to a non-HVS approach. The resilience of the watermarking algorithm is tested against a series of different spatial, temporal, and compression attacks. To improve the robustness of the algorithm, we use error correction codes and embed the watermark with spatial and temporal redundancy. The proposed method achieves a good perceptual quality and high resistance to a large spectrum of attacks.

Quantisation-based video watermarking in the wavelet domain with spatial and temporal redundancy

In this article we introduce a new public digital watermarking technique for video copyright protection working in the discrete wavelet transform domain. The scheme uses binary images as watermarks. These are embedded in the detail wavelet coefficients of the middle wavelet sub-bands. The method is a combination of spread spectrum and quantisation-based watermarking. Every bit of the watermark is spread over a number of wavelet coefficients with the use of a secret key. The resilience of the watermarking algorithm was tested against a series of eight different attacks using different videos. To improve the resilience of the algorithm we use error correction codes and embed the watermark with spatial and temporal redundancy. The proposed method achieves a very good perceptual quality with mean peak signal-to-noise ratio values of the watermarked videos of more than 40 dB and high resistance to a large spectrum of attacks.

Blind Watermarking Capacity Analysis of MPEG2 Coded Video

Video watermarking capacity is an evaluation of how much information can be hidden with in a digital video. In this paper we want to analyze the watermarking capacity for MPEG2 coded video using different blind watermarking schemes and introduce new watermarking algorithms with high watermarking capacity. MPEG2 compression is commonly used for distribution of video content, so we decided to focus on MPEG2 coded video. The analyzed techniques are working in the spatial and DCT domain. The resistance of the watermarking algorithms against MPEG2 transcoding is tested and, because the content of the video has great influence on watermarking capacity, our techniques also take this aspect into consideration.

Automatic lesion segmentation for melanoma diagnostics in macroscopic images

Detailed segmentation of pigmented skin lesions is an important requirement in computer aided applications for melanoma assessment. In particular, accurate segmentation is necessary for image-guided evaluation of skin lesions characteristics. In this paper, we present a new approach of histogram thresholding for detailed segmentation of skin lesions based on histogram analysis of the saturation color component in the hue-saturation-value (HSV) color space. The proposed technique is specifically developed with the aim to handle the complex variability of features for macroscopic color images taken in uncontrolled environment. A dataset of 30 cases with manual segmentation was used for evaluation. We compare our results with two of most important existing segmentation techniques. For similarity report between automatic and manual segmentation we used dice similarity coefficient (DSC), the true detection rate (TDR), and the false positive rate (FPR). Experimental results show that the proposed method has high precision and low computational complexity.

Performance evaluation of subcarrier allocation methods for OFDMA

The purpose of this paper is to analyze performances of three subcarrier allocation methods used by orthogonal frequency-division multiple access (OFDMA). In OFDMA, before assigning subcarriers to users, they are first distributed into subchannels using three different subcarrier allocation methods. The results are compared in terms of bit error rate (BER) dependency on signal to noise ratio (SNR), for different multipath propagation channels, for a variable number of users and for different digital modulation schemes.

A New Class of S-Type Current Controlled Nonlinear Negative Resistances

The paper presents a new method for generating S-type nonlinear current controlled negative resistances. The presented method can be used to obtain a large number of nonlinear resistances. We apply the method for a negative resistance device, using bipolar transistors, described by theoretical characteristics and performances and we compare the results with the theoretical specifications

Thermal image filtering by bi-dimensional empirical mode decomposition

The abnormal function of cells can be detected by anatomic or physiological registrations. Most of modern approaches, as ultrasound, RMN or CT, show anatomic parametric modifications of tissues or organs. They highlight areas with a larger diameter 1 cm. In the case of skin or superficial cancers, local temperature is different, and it can be put out by thermal imager. Medical imaging is a leading role in modern diagnosis for abnormal or normal tissues or organs. Some information has to be improved for a better diagnosis by reducing or removing some unwanted information like noise affecting image texture. The traditional technologies for medical image enhancement use spatial or frequency domain methods, but whole image processing will hide both partial and specific information for human signals. A particular kind of medical images is represented by thermal imaging. Recently, these images were used for skin or superficial cancers diagnosis, but very clear outlines of certain alleged affected areas need to be shown. Histogram equalization cannot highlights the edges and control the effects of enhancement. A new filtering method was introduced by Huang by using the empirical mode decomposition, EMD. An improved filtering method for thermal images, based on EMD, is presented in this paper, and permits to analyze nonlinear and non-stationary data by the adaptive decomposition into intrinsic mode surfaces. The results, evaluated by SNR ratios, are compared with other filtering methods.

LDPC encoding performances for fading suppression in MIMO-CDMA wireless networks

In multiuser wireless communication systems, signal recovery, even at low BER is a relevant factor for ensuring a safe and reliable communication. Efforts for interference minimization include multiple analysis of source coding/decoding techniques, channel coding/decoding techniques and multiuser detection algorithms. This paper illustrates the improvement brought by LDPC technique in SS systems when AWGN and Rayleigh/Nakagami-m fading occur on communication channel. Performances are evaluated for different sets of spreading sequences (Walsh-Hadamard, Kasami and PN) and based on the simulation results several conclusions are highlighted and further improvement will be proposed for fading effects reduction and interference minimization.

Digital watermarking and segmentation of macroscopic pigmented skin lesions images

This work presents the use of digital watermarking for applications of automated pigmented skin lesions assessment. Automated skin lesion assessment by digital image processing of macroscopic pigmented skin lesion (MPLS) images uses lesion characteristics for malignant risk computation. The accuracy of the computed risk level is increased when additional information is taken into consideration: age, gender, skin type, position of the lesions on body, and the presence of multiple and similar lesions. We propose a digital watermarking scheme for embedding relevant patient information into the color MPSL image. The preliminary experimental results are promising, and suggest that the proposed watermarking scheme is suitable for this type of application.

Efficient Transform Coefficient Coding in HEVC

This paper presents an efficient coding method of transform coefficients in HEVC video encoding standard. Our approach makes use of spectral characteristics of the transform unit coefficients in inter predicted coding units. Also a coefficient significance assessment algorithm is integrated into the video encoder, for a non-zero coefficients number reduction. It is shown to be a good method from the compression point of view, without quality losses.