Deepayan Bhowmik

Video based technology for ambient assisted living: A review of the literature

Ambient assisted living (AAL) has the ambitious goal of improving the quality of life and maintaining independence of older and vulnerable people through the use of technology. Most of the western world will see a very large increase in the number of older people within the next 50 years with limited resources to care for them. AAL is seen as a promising alternative to the current care models and consequently has attracted lots of attention. Recently, a number of researchers have developed solutions based on video cameras and computer vision systems with promising results. However, for the domain to reach maturity, several challenges need to be faced, including the development of systems that are robust in the real-world and are accepted by users, carers and society. In this literature review paper we present a comprehensive survey of the scope of the domain, the existing technical solutions and the challenges to be faced.

Visual Attention-Based Image Watermarking

Imperceptibility and robustness are two complementary but fundamental requirements of any watermarking algorithm. Low strength watermarking yields high imperceptibility but exhibits poor robustness. High strength watermarking schemes achieve good robustness but often infuse distortions resulting in poor visual quality in host media. If distortion due to high strength watermarking can avoid visually attentive regions, such distortions are unlikely to be noticeable to any viewer. In this paper, we exploit this concept and propose a novel visual attention-based highly robust image watermarking methodology by embedding lower and higher strength watermarks in visually salient and non-salient regions, respectively. A new low complexity wavelet domain visual attention model is proposed that allows us to design new robust watermarking algorithms. The proposed new saliency model outperforms the state-of-the-art method in joint saliency detection and low computational complexity performances. In evaluating watermarking performances, the proposed blind and non-blind algorithms exhibit increased robustness to various natural image processing and filtering attacks with minimal or no effect on image quality, as verified by both subjective and objective visual quality evaluation. Up to 25% and 40% improvement against JPEG2000 compression and common filtering attacks, respectively, are reported against the existing algorithms that do not use a visual attention model.

Video watermarking using motion compensated 2D+t+2D filtering

Frame-by-frame video watermark embedding without considering motion, results in flicker and other motion mismatch artifacts in the watermarked video. Motion compensated temporal filtering (MCTF) provides a better framework for video watermarking by accounting object motion. However, depending on motion and texture characteristics of the video and the choice of spatial-temporal sub band for watermark embedding, MCTF has to be performed either on the spatial domain (t+2D) or in the wavelet domain (2D+t). In this work we propose improved video watermarking schemes by offering a generalized motion compensated 2D+t+2D framework for watermark embedding. An improved MCTF is used by modifying the MCTF update step to follow the motion trajectory in hierarchical temporal decomposition by using direct motion vector fields in the update step and implied motion vectors in the prediction step. The proposed 2D+t+2D framework with the modified MCTF-based watermarking shows better embedding distortion in terms of both mean square error and flicker metric for various combinations of spatial-temporal decompositions, compared to the existing frame-by-frame and t+2D domain video watermarking. The proposed scheme outperforms the conventional t+2D watermarking in terms of robustness performance, particularly for blind watermarking schemes where the motion is estimated from the watermarked video.

Scalable watermark extraction for real-time authentication of JPEG 2000 images

This paper proposes a novel scalable authentication scheme that utilizes the progressive enhancement functionality in JPEG 2000 scalable image coding. The proposed method first models the wavelet-based quality scalable coding to identify the effect of the quantization and de-quantization on wavelet coefficient magnitudes and the data embedded within such coefficients as a watermark. A relationship is then established between the watermark extraction rule and the embedding rule, using the magnitudes of the reconstructed and original coefficients. It ranks the wavelet coefficients according to their ability to retain the embedded watermark data intact under various quantization levels corresponding to quality enhancements. Then watermark data is embedded into wavelet coefficients according to their rank followed by JPEG 2000 embedded coding. At the decoder as more and more quality and resolution layers are decoded the authentication metric is improved, thus resulting in gradually increasing complexity of the authentication process according to the number of quality and resolution enhancements. The low complexity authentication is available at low quality low resolution decoding, enabling real-time authentication for resource constrained applications without affecting the authentication metric. Compared to the existing methods, the proposed method results in highly robust scalable authentication of JPEG 2000 coded images.

Quality Scalability Aware Watermarking for Visual Content

Scalable coding-based content adaptation poses serious challenges to traditional watermarking algorithms, which do not consider the scalable coding structure and hence cannot guarantee correct watermark extraction in media consumption chain. In this paper, we propose a novel concept of scalable blind watermarking that ensures more robust watermark extraction at various compression ratios while not effecting the visual quality of host media. The proposed algorithm generates scalable and robust watermarked image code-stream that allows the user to constrain embedding distortion for target content adaptations. The watermarked image code-stream consists of hierarchically nested joint distortion-robustness coding atoms. The code-stream is generated by proposing a new wavelet domain blind watermarking algorithm guided by a quantization based binary tree. The code-stream can be truncated at any distortion-robustness atom to generate the watermarked image with the desired distortion-robustness requirements. A blind extractor is capable of extracting watermark data from the watermarked images. The algorithm is further extended to incorporate a bit-plane discarding-based quantization model used in scalable coding-based content adaptation, e.g., JPEG2000. This improves the robustness against quality scalability of JPEG2000 compression. The simulation results verify the feasibility of the proposed concept, its applications, and its improved robustness against quality scalable content adaptation. Our proposed algorithm also outperforms existing methods showing 35% improvement. In terms of robustness to quality scalable video content adaptation using Motion JPEG2000 and wavelet-based scalable video coding, the proposed method shows major improvement for video watermarking.

On robustness against JPEG2000: a performance evaluation of wavelet-based watermarking techniques

With the emergence of new scalable coding standards, such as JPEG2000, multimedia is stored as scalable coded bit streams that may be adapted to cater network, device and usage preferences in multimedia usage chains providing universal multimedia access. These adaptations include quality, resolution, frame rate and region of interest scalability and achieved by discarding least significant parts of the bit stream according to the scalability criteria. Such content adaptations may also affect the content protection data, such as watermarks, hidden in the original content. Many wavelet-based robust watermarking techniques robust to such JPEG2000 compression attacks are proposed in the literature. In this paper, we have categorized and evaluated the robustness of such wavelet-based image watermarking techniques against JPEG2000 compression, in terms of algorithmic choices, wavelet kernel selection, subband selection, or watermark selection using a new modular framework. As most of the algorithms use a different set of parametric combination, this analysis is particularly useful to understand the effect of various parameters on the robustness under a common platform and helpful to design any such new algorithm. The analysis also considers the imperceptibility performance of the watermark embedding, as robustness and imperceptibility are two main watermarking properties, complementary to each other.

A Framework for Evaluating Wavelet based Watermarking for Scalable Coded Digital Item Adaptation Attacks

A framework for evaluating wavelet based watermarking schemes against scalable coded visual media content adaptation attacks is presented. The framework, Watermark Evaluation Bench for Content Adaptation Modes (WEBCAM), aims to facilitate controlled evaluation of wavelet based watermarking schemes under MPEG-21 part-7 digital item adaptations (DIA). WEBCAM accommodates all major wavelet based watermarking in single generalised framework by considering a global parameter space, from which the optimum parameters for a specific algorithm may be chosen. WEBCAM considers the traversing of media content along various links and required content adaptations at various nodes of media supply chains. In this paper, the content adaptation is emulated by the JPEG2000 coded bit stream extraction for various spatial resolution and quality levels of the content. The proposed framework is beneficial not only as an evaluation tool but also as design tool for new wavelet based watermark algorithms by picking and mixing of available tools and finding the optimum design parameters.

A Generalised Model for Distortion Performance Analysis of Wavelet Based Watermarking

A model for embedding distortion performance for wavelet based watermarking is presented in this paper. Firstly wavelet based watermarking schemes are generalised into a single common framework. Then a mathematical approach has been made to find the relationship between distortion performance metrics and the watermark embedding parameters. The derived model shows that for wavelet based watermarking schemes the sum of energy of the selected wavelet coefficients to be modified is directly proportional to the distortion performance (the mean square error) measured in the pixel domain. The propositions are made using the energy conservation theorem between input signal and transform domain coefficients for orthonormal wavelet bases. Such an analysis is useful to choose the wavelet coefficients during watermark embedding procedure and to find suitable input parameters such as wavelet kernel or the choice of subband.

Visual attention-based watermarking

A region of interest dictates the most important visible aspects of an image, so distortion within these areas will be highly noticeable to any viewer. The visual attention model computes such regions in an image. In this paper, we present wavelet domain computation of the visual attention model and its applicability in wavelet-based watermarking. The proposed algorithm can embed more information into visually uninteresting areas within the host image, determined by the visual attention model. This algorithm has increased robustness to various natural image processing and filtering attacks, while minimum effect on the image quality as verified by both subjective and objective evaluations. Such an approach can be adopted into many multimedia forensic applications to aid the watermarking process.

The effect of quality scalable image compression on robust watermarking

The effect of quantization based compression in quality scalable image coding on the robustness of wavelet based watermarking is presented. The non-blind direct modification type watermarking is considered for the analysis presented in this paper. First we present the analysis considering any quantization parameter and then restrict it to the integer powers of two to model the bit-plane discarding based quantization used in quality scalable coding, such as JPEG2000. This work assumes that the watermark embedding and compression uses the same wavelet filters. The derived model shows the relationship between the modified coefficients and the quantization factor, which is then used to obtain the conditions for the correct watermark extraction under compression. Based on this analysis, one can select wavelet coefficients for embedding the watermark in a manner that the correct watermark extraction is possible for a given quantization level. The results show higher robustness when this model is used for embedding the watermark. The paper also evaluates the performance of the model when the watermark embedding and the compression wavelet filters are not the same.