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    A method of compressing a high dynamic range original image to provide compressed image data for use with (i) a high dynamic range decoder for viewing the high dynamic range image and (ii) a reduced bit depth decoder for viewing an image of lower dynamic range which has been derived from the high dynamic range original image. The difference between the image of the high dynamic range original image and the lower dynamic range is measured and that difference information is compressed. Compressed image data is produced comprising the compressed image of the lower dynamic range and the compressed image data.
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    A method of compressing and decompressing High Dynamic Range images utilising the relationship : (I) Where γ ≥ 2.5; and (II) = compressed; and (III) = linear
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  • Uniform Color Space-Based High Dynamic Range Video Compression

    Mukherjee, Ratnajit   Debattista, Kurt   Rogers, Thomas-Bashford   Bessa, Maximino   Chalmers, Alan  

    Recently, there has been a significant progress in the research and development of the high dynamic range (HDR) video technology and the state-of-the-art video pipelines are able to offer a higher bit depth support to capture, store, encode, and display HDR video content. In this paper, we introduce a novel HDR video compression algorithm, which uses a perceptually uniform color opponent space, a novel perceptual transfer function to encode the dynamic range of the scene, and a novel error minimization scheme for accurate chroma reproduction. The proposed algorithm was objectively and subjectively evaluated against four state-of-the-art algorithms. The objective evaluation was conducted across a set of 39 HDR video sequences, using the latest x265 10-bit video codec along with several perceptual and structural quality assessment metrics at 11 different quality levels. Furthermore, a rating-based subjective evaluation (n =3D 40) was conducted with six sequences at two different output bitrates. Results suggest that the proposed algorithm exhibits the lowest coding error amongst the five algorithms evaluated. Additionally, the rate-distortion characteristics suggest that the proposed algorithm outperforms the existing state-of-the-art at bitrates >=3D 0.4 bits/pixel.
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    A method of compressing a block (2) of multisensory data. The block comprises at least one frame comprising a plurality of different types of data. There are stored quality settings (7) for each type of data and these include parameters determining the level of compression for that type of data in the block. Each type of data in the block is subjected to compression in accordance with the quality settings to produce a compressed bock of multisensory data (11). A package of data is (10) is created which includes the compressed block and a header (12) which identifies the compression technique and includes the respective parameters used, for compressing each type of data. A number of packages are then subjected to inter- package compression to create a final package (14). This combines the individual packages, but the headers have been replaced by mini headers (15) which now contain only the parameters for the individual compression of the data types. The final package (14) has a main header (16), which contains temporal compression parameters, as well as data identifying the types of compression applied to the different types of data of the individual packages in the final package.
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  • An evaluation of power transfer functions for HDR video compression

    Hatchett, Jonathan   Debattista, Kurt   Mukherjee, Ratnajit   Bashford-Rogers, Thomas   Chalmers, Alan  

    High dynamic range (HDR) imaging enables the full range of light in a scene to be captured, transmitted and displayed. However, uncompressed 32-bit HDR is four times larger than traditional low dynamic range (LDR) imagery. If HDR is to fulfil its potential for use in live broadcasts and interactive remote gaming, fast, efficient compression is necessary for HDR video to be manageable on existing communications infrastructure. A number of methods have been put forward for HDR video compression. However, these can be relatively complex and frequently require the use of multiple video streams. In this paper, we propose the use of a straightforward Power Transfer Function (PTF) as a practical, computationally fast, HDR video compression solution. The use of PTF is presented and evaluated against four other HDR video compression methods. An objective evaluation shows that PTF exhibits improved quality at a range of bit-rates and, due to its straightforward nature, is highly suited for real-time HDR video applications.
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  • Olfaction and Selective Rendering

    Harvey, Carlo   Bashford-Rogers, Thomas   Debattista, Kurt   Doukakis, Efstratios   Chalmers, Alan  

    Accurate simulation of all the senses in virtual environments is a computationally expensive task. Visual saliency models have been used to improve computational performance for rendered content, but this is insufficient for multi-modal environments. This paper considers cross-modal perception and, in particular, if and how olfaction affects visual attention. Two experiments are presented in this paper. Firstly, eye tracking is gathered from a number of participants to gain an impression about where and how they view virtual objects when smell is introduced compared to an odourless condition. Based on the results of this experiment a new type of saliency map in a selective-rendering pipeline is presented. A second experiment validates this approach, and demonstrates that participants rank images as better quality, when compared to a reference, for the same rendering budget.
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  • HDR video past, present and future: A perspective

    Chalmers, Alan   Debattista, Kurt  

    High dynamic range (HDR) video has emerged from research labs around the world and entered the realm of consumer electronics. The dynamic range that a human can see in a scene with minimal eye adaption (approximately 1,000,000:1) is vastly greater than traditional imaging technology which can only capture about 8 f-stops (256:1). HDR technology, on the other hand, has the potential to capture the full range of light in a scene; even more than a human eye can see. This paper examines the field of HDR video from capture to display: past, present and future. In particular the paper looks beyond the current marketing hype around HDR to show how HDR video in the future can and, indeed, should bring about a step change in imaging, analogous to the change from black and white to colour.
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  • Context-aware HDR video distribution for mobile devices

    Melo, Miguel   Barbosa, Luis   Bessa, Maximino   Debattista, Kurt   Chalmers, Alan  

    HDR video on mobile devices is in its infancy and there are no solutions yet that can achieve full HDR video reproduction due to computational power limitations. In this paper we present a novel and versatile solution that allows the delivery of HDR video on mobile devices by taking into account contextual information and retro-compatibility for devices that do not have the computational power to decode HDR video. The proposed solution also enables the remote transmission of HDR video to mobile devices in real-time. This context-aware HDR video distribution solution for mobile devices is evaluated and discussed by considering the impact of HDR videos over conventional low dynamic range videos on mobile devices as well as the challenge of playing HDR videos directly locally or remotely.
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  • A Machine-Learning-Driven Sky Model

    Satilmis, Pinar   Bashford-Rogers, Thomas   Chalmers, Alan   Debattista, Kurt  

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  • Subjective and Objective Evaluation of Local Dimming Algorithms for HDR Images

    Duan, Lvyin   Debattista, Kurt   Lei, Zhichun   Chalmers, Alan  

    In order to enhance viewing experiences, a number of backlight local dimming (BLD) algorithms have been developed to improve the image contrast ratio and provide power efficiency for modern displays. In order to evaluate which BLD algorithm performs best for HDR images rendering on dual-panel displays, this paper presents a comprehensive subjective and objective evaluation conducted with five BLD algorithms across a number of scenes. The subjective evaluation (N & x003D; 24) required participants to rank each BLD generated image based on which they thought was the most natural looking. The objective evaluation was undertaken via the use of a novel methodology to generate the images per BLD for comparison against the ground truth High Dynamic Range (HDR) image. Resulting images were compared with the ground truth using qualitative methods namely: HDR-VDP, puPSNR, puSSIM and puVIFP. The power-saving rate of each method was also calculated. The results demonstrate a strong correlation between objective and subjective evaluation. Furthermore, results show that BLD algorithms that consider the luminance balance between backlight and LCD images perform better than straightforward BLD methods.
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  • A review of attack graph and attack tree visual syntax in cyber security

    Lallie, Harjinder Singh   Debattista, Kurt   Bal, Jay  

    Perceiving and understanding cyber-attacks can be a difficult task, and more effective techniques are needed to aid cyber-attack perception. Attack modelling techniques (AMTs) - such as attack graphs, attack trees and fault trees, are a popular method of mathematically and visually representing the sequence of events that lead to a successful cyber-attack. These methods are useful visual aids that can aid cyber-attack perception. This survey paper describes the fundamental theory of cyber-attack before describing how important elements of a cyber-attack are represented in attack graphs and attack trees. The key focus of the paper is to present empirical research aimed at analysing more than 180 attack graphs and attack trees to identify how attack graphs and attack trees present cyber-attacks in terms of their visual syntax. There is little empirical or comparative research which evaluates the effectiveness of these methods. Furthermore, despite their popularity, there is no standardised attack graph visual syntax configuration, and more than seventy self-nominated attack graph and twenty attack tree configurations have been described in the literature - each of which presents attributes such as preconditions and exploits in a different way. The survey demonstrates that there is no standard method of representing attack graphs or attack trees and that more research is needed to standardise the representation. (C) 2020 Elsevier Inc. All rights reserved.
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  • Displaying detail in bright environments:A 10,000 nit display and its evaluation

    Hatchett, Jonathan   Toffoli, Domenico   Melo, Miguel   Bessa, Maximino   Debattista, Kurt   Chalmers, Alan  

    Consumer High Dynamic Range (HDR) displays are appearing on the market. Capable of generating a peak luminance of up to 2,000 nits, the improved dynamic range they provide can only be perceived when viewed in a dark environment. In this paper, we present a display architecture that is capable of generating a peak luminance of 10,000 nits. We demonstrate, with a subjective evaluation, that the increased peak luminance is required to perceive a high dynamic range in bright ambient environments. Furthermore, we show that by fitting a surface through the data, we can predict the dynamic range that can be perceived from the luminance and illuminance with low error. We can also invert the prediction to estimate the required peak luminance for a particular combination of dynamic range and ambient lighting.
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  • Optimal exposure compression for high dynamic range content

    Debattista, Kurt   Bashford-Rogers, Thomas   Selmanovi?, Elmedin   Mukherjee, Ratnajit   Chalmers, Alan  

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  • Subjective Evaluation of High-Fidelity Virtual Environments for Driving Simulations

    Debattista, Kurt   Bashford-Rogers, Thomas   Harvey, Carlo   Waterfield, Brian   Chalmers, Alan  

    Virtual environments (VEs) grant the ability to experience real-world scenarios, such as driving, in a virtual, safe, and reproducible context. However, in order to achieve their full potential, the fidelity of the VE must provide confidence that it replicates the perception of the real-world experience. The computational cost of simulating real-world visuals accurately means that compromises to the fidelity of the visuals must be made. In this paper, a subjective evaluation of driving in a VE at different quality settings is presented. Participants (n =3D 44) were driven around in the real world and in a purposely built representative VE and the fidelity of the graphics and overall experience at low-, medium-, and high-visual settings were analyzed. Low quality corresponds to the illumination in many current traditional simulators, medium to a higher quality using accurate shadows and reflections, and high to the quality experienced in modern movies and simulations that require hours of computation. Results demonstrate that graphics quality affects the perceived fidelity of the visuals and the overall experience. When judging the overall experience, participants could tell the difference between the lower quality graphics and the rest but did not significantly discriminate between the medium and higher graphical settings. This indicates that future driving simulators should improve the quality, but once the equivalent of the presented medium quality is reached, they may not need to do so significantly.
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  • Subjective Evaluation of High-Fidelity Virtual Environments for Driving Simulations

    Debattista, Kurt   Bashford-Rogers, Thomas   Harvey, Carlo   Waterfield, Brian   Chalmers, Alan  

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  • Foreword - High dynamic range imaging

    Santos, Luis Paulo   Debattista, Kurt  

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