Visual assessment for the quantization error in wavelet based monochrome videos

The investigation of the discrete wavelet transform (DWT) based video coder is still undergoing in the literature. One of the open problems to be solved is the perception to the quantization noise in different subbands in the DWT domain. This is a critical issue for the development of a better motion compensation (MC) scheme. An experiment and relevant results analysis are presented in this paper to address the above issue. Monochrome video sequences of natural scenes are used in the experiment therefore the so-called masking effects can be taken into account in the decision of the sensitivity to the noise hidden in the DWT domain. The preliminary results show that the most sensitive subbands are those in the lowest three resolution levels under a five-levels decomposition scheme. The further analysis proves that the distribution of the sensitivity to each individual subband has been shifted by the context of the video

Evaluation of transform based image coders, using different transforms and techniques in the transform domain

This paper addresses the most relevant aspects of lossy image coding techniques, and presents an evaluation study on this subject, using several transforms and different methods in the transform domain. We developed different transform based image coders/decoders (codecs) using different transforms, such as the discrete cosine transform, the discrete wavelet transform and the S transform. Besides JPEG Baseline, we also use other techniques and methods in the transform domain such as a DWT based JPEG-like (JPEG DWT), a JPEG DWT with visual threshold (JPEG-VT), a JPEG–like coder based on the ST, and an EZW coder. The codecs were programmed in MATLAB™, using custom and built-in functions. The structures of the codecs are presented, also as some experimental results which allow us evaluate them, and support this study

Visual quality enhancement for color images in the framework of the JPEG2000 compression standard

In the last years, the consideration of different models of the Human Visual System (HVS) in the final perceived quality of the compressed images becomes a major research subject. Therefore, it is natural to take advantage of the recent knowledge on both perception and models of the human vision in an image compression system. Thus, in this paper we propose an integration method of that knowledge for the improvement of perceptual JPEG2000 image compression quality. This method consists on two parts : a laboratory evaluation of the HVS model by the Contrast Sensitivity Function (CSF), and an implementation technique of visual weightings for the JPEG2000 scheme, using the evaluated HVS model in the Fourier domain of the color image.Durant les dernières années, la prise en compte de modèles du Système Visuel Humain (SVH) dans l'évaluation de la qualité visuelle des images couleur compressées, est devenu un sujet de recherche majeur. Il semble naturel d'intégrer davantage les connaissances récentes sur la perception et la modélisation de la vision humaine, dans les systèmes de compression d'images. Ainsi, dans cet article, nous proposons une méthode d'intégration de ces connaissances pour l'augmentation de la qualité visuelle d'images compressées JPEG2000. Cette méthode consiste en deux parties : une évaluation de laboratoire pour la modélisation du SVH par la Fonction de Sensibilité au Contraste (CSF) et une technique de calcul de facteurs de pondération visuelle pour la compression JPEG2000, utilisant le modèle SVH évalué, dans le domaine de Fourier de l'image couleur

Spread spectrum-based video watermarking algorithms for copyright protection

Merged with duplicate record 10026.1/2263 on 14.03.2017 by CS (TIS)Digital technologies know an unprecedented expansion in the last years. The consumer can now benefit from hardware and software which was considered state-of-the-art several years ago. The advantages offered by the digital technologies are major but the same digital technology opens the door for unlimited piracy. Copying an analogue VCR tape was certainly possible and relatively easy, in spite of various forms of protection, but due to the analogue environment, the subsequent copies had an inherent loss in quality. This was a natural way of limiting the multiple copying of a video material. With digital technology, this barrier disappears, being possible to make as many copies as desired, without any loss in quality whatsoever. Digital watermarking is one of the best available tools for fighting this threat. The aim of the present work was to develop a digital watermarking system compliant with the recommendations drawn by the EBU, for video broadcast monitoring. Since the watermark can be inserted in either spatial domain or transform domain, this aspect was investigated and led to the conclusion that wavelet transform is one of the best solutions available. Since watermarking is not an easy task, especially considering the robustness under various attacks several techniques were employed in order to increase the capacity/robustness of the system: spread-spectrum and modulation techniques to cast the watermark, powerful error correction to protect the mark, human visual models to insert a robust mark and to ensure its invisibility. The combination of these methods led to a major improvement, but yet the system wasn't robust to several important geometrical attacks. In order to achieve this last milestone, the system uses two distinct watermarks: a spatial domain reference watermark and the main watermark embedded in the wavelet domain. By using this reference watermark and techniques specific to image registration, the system is able to determine the parameters of the attack and revert it. Once the attack was reverted, the main watermark is recovered. The final result is a high capacity, blind DWr-based video watermarking system, robust to a wide range of attacks.BBC Research & Developmen

High performance shift invariant motion estimation and compensation in wavelet domain video compression

The contributions of this dissertation are in the development of two new interrelated approaches to video data compression: 1) A level-refined motion estimation and subband compensation method for the effective motion estimation and motion compensation. 2) A shift-invariant sub-decimation decomposition method in order to overcome the deficiency of the decimation process in estimating motion due to its shift-invariant property of wavelet transform. The enormous data generated by digital videos call for an intense need of efficient video compression techniques to conserve storage space and minimize bandwidth utilization. The main idea of video compression is to reduce the interpixel redundancies inside and between the video frames by applying motion estimation and motion compensation (MEMC) in combination with spatial transform coding. To locate the global minimum of the matching criterion function reasonably, hierarchical motion estimation by coarse to fine resolution refinements using discrete wavelet transform is applied due to its intrinsic multiresolution and scalability natures

A DWT based perceptual video coding framework: concepts, issues and techniques

The work in this thesis explore the DWT based video coding by the introduction of a novel DWT (Discrete Wavelet Transform) / MC (Motion Compensation) / DPCM (Differential Pulse Code Modulation) video coding framework, which adopts the EBCOT as the coding engine for both the intra- and the inter-frame coder. The adaptive switching mechanism between the frame/field coding modes is investigated for this coding framework. The Low-Band-Shift (LBS) is employed for the MC in the DWT domain. The LBS based MC is proven to provide consistent improvement on the Peak Signal-to-Noise Ratio (PSNR) of the coded video over the simple Wavelet Tree (WT) based MC. The Adaptive Arithmetic Coding (AAC) is adopted to code the motion information. The context set of the Adaptive Binary Arithmetic Coding (ABAC) for the inter-frame data is redesigned based on the statistical analysis. To further improve the perceived picture quality, a Perceptual Distortion Measure (PDM) based on human vision model is used for the EBCOT of the intra-frame coder. A visibility assessment of the quantization error of various subbands in the DWT domain is performed through subjective tests. In summary, all these findings have solved the issues originated from the proposed perceptual video coding framework. They include: a working DWT/MC/DPCM video coding framework with superior coding efficiency on sequences with translational or head-shoulder motion; an adaptive switching mechanism between frame and field coding mode; an effective LBS based MC scheme in the DWT domain; a methodology of the context design for entropy coding of the inter-frame data; a PDM which replaces the MSE inside the EBCOT coding engine for the intra-frame coder, which provides improvement on the perceived quality of intra-frames; a visibility assessment to the quantization errors in the DWT domain

Life Sciences Program Tasks and Bibliography for FY 1996

This document includes information on all peer reviewed projects funded by the Office of Life and Microgravity Sciences and Applications, Life Sciences Division during fiscal year 1996. This document will be published annually and made available to scientists in the space life sciences field both as a hard copy and as an interactive Internet web page