Segmentation of the glottal space from laryngeal images using the watershed transform

The present work describes a new method for the automatic detection of the glottal space from laryngeal images obtained either with high speed or with conventional video cameras attached to a laryngoscope. The detection is based on the combination of several relevant techniques in the field of digital image processing. The image is segmented with a watershed transform followed by a region merging, while the final decision is taken using a simple linear predictor. This scheme has successfully segmented the glottal space in all the test images used. The method presented can be considered a generalist approach for the segmentation of the glottal space because, in contrast with other methods found in literature, this approach does not need either initialization or finding strict environmental conditions extracted from the images to be processed. Therefore, the main advantage is that the user does not have to outline the region of interest with a mouse click. In any case, some a priori knowledge about the glottal space is needed, but this a priori knowledge can be considered weak compared to the environmental conditions fixed in former works

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

Role of coloration in antipredator strategies of Pristidactylus achalensis (Squamata: Leiosauridae) related to sex and stages of predation

The interaction between behavioural and phenotypic traits, such as coloration, plays a specific role at different stages of the predatory sequence. Cryptic coloration involves a match to the background that reduces the risk of detection, and it is usually optimized by immobility behaviour. In lizards, sexual dichromatism and within-individual changes of colour can influence the level of their crypsis and thus influence antipredator behaviour and the decision to flee. Here, we examined variation in coloration and antipredator behaviour between the sexes of the Achala copper lizard (Pristidactylus achalensis). We measured sexual dichromatism and crypsis in accordance with avian vision. We also exposed lizards to a raptor dummy to assess the colour change and behaviour at the detection and approach stages of the predatory event. Finally, we tested escape behaviour in the natural habitat. We found that males were more conspicuous than females. Additionally, individuals showed distinct behaviours at different stages of the predation simulation, but there were no differences between the sexes. However, in their natural habitat males initiated flight at greater distances than females, which might be related to their more conspicuous coloration. In summary, this study shows how differences in crypsis between the sexes affect escape behaviour during the approach stage of predation.Fil: Torres, María del Milagro. Universidad Nacional de Córdoba. Facultad de Cs.exactas Físicas y Naturales. Departamento de Diversidad Biológica y Ecológica. Cátedra de Biología del Comportam. y Div. Animal Ii; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Viladrich, Leonel Jeremías. Universidad Nacional de Córdoba. Facultad de Cs.exactas Físicas y Naturales. Departamento de Diversidad Biológica y Ecológica. Cátedra de Biología del Comportam. y Div. Animal Ii; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Naretto, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentin

Training and Predicting Visual Error for Real-Time Applications

Visual error metrics play a fundamental role in the quantification of perceived image similarity. Most recently, use cases for them in real-time applications have emerged, such as content-adaptive shading and shading reuse to increase performance and improve efficiency. A wide range of different metrics has been established, with the most sophisticated being capable of capturing the perceptual characteristics of the human visual system. However, their complexity, computational expense, and reliance on reference images to compare against prevent their generalized use in real-time, restricting such applications to using only the simplest available metrics. In this work, we explore the abilities of convolutional neural networks to predict a variety of visual metrics without requiring either reference or rendered images. Specifically, we train and deploy a neural network to estimate the visual error resulting from reusing shading or using reduced shading rates. The resulting models account for 70%-90% of the variance while achieving up to an order of magnitude faster computation times. Our solution combines image-space information that is readily available in most state-of-the-art deferred shading pipelines with reprojection from previous frames to enable an adequate estimate of visual errors, even in previously unseen regions. We describe a suitable convolutional network architecture and considerations for data preparation for training. We demonstrate the capability of our network to predict complex error metrics at interactive rates in a real-time application that implements content-adaptive shading in a deferred pipeline. Depending on the portion of unseen image regions, our approach can achieve up to $2\times$ performance compared to state-of-the-art methods.Comment: Published at Proceedings of the ACM in Computer Graphics and Interactive Techniques. 14 Pages, 16 Figures, 3 Tables. For paper website and higher quality figures, see https://jaliborc.github.io/rt-percept

Effects of resolution of lighting control systems

Advances in lighting technologies have spurred sophisticated lighting control systems (LCSs). To conserve energy and improve occupants’ wellbeing, LCSs have been integrated into sustainable buildings. However, the complexity of LCSs may lead to negative experiences and reduce the frequency of their use. One fundamental issue, which has not been systematically investigated, is the impact of control resolution (the smallest change produced by an LCS). In an ideal LCS, the resolution would be sufficiently fine for users to specify their desired lighting conditions, but the smallest change would be detectable. Thus, the design of optimal control systems requires a thorough understanding of the detectability and acceptability of differences in illuminance, luminance and colour. The control of colour is complicated by the range of interfaces that can be used to facilitate colour mixing. Four psychophysical experiments investigated the effect of LCS resolution. The first two experiments explored the effect of resolution in white light LCSs on usability and energy conservation. The results suggest that, in different applications, LCSs with resolutions between 14.8 % and 17.7 % (of illuminance) or 26.0 % and 32.5 % (of luminance) have the highest usability. The third experiment evaluated the usability of three colour channel control interfaces based on red, green, blue (RGB), hue, saturation, brightness (HSB) and opponent colour mixing systems. Although commonly used, the RGB interface was found to have the lowest usability. The fourth experiment explored the effect of hue resolution, saturation resolution and luminance resolution on the usability. Generally, middle range resolutions, which are approximately between three and five times the magnitude of the just noticeable difference (JND), for both hue and saturation were found to yield the greatest usability. The interaction between these three variables was characterised. Findings from this research provide a deeper understanding of the fundamental attribute of control resolution and can guide the development of useful and efficient lighting control systems

Identifying the functional architecture underlying multiple representations in visual working memory

ABSTRACT This thesis aimed to investigate how visual working memory takes advantage of long-term knowledge in order to allow semantic elaboration in the form of chunking and the role of the central executive in this process. Two leading theoretical frameworks of working memory which both emphasise the role of long-term memory are discussed. One of which views working memory as consisting of multiple discrete, modality specific subsystems (Baddeley, 2000) and one which views working memory as an activated subset of long term memory (Cowan, 2005). Both of these models propose the integration of short- and long-term representations to be attentionally demanding. To investigate this assumption, two forms of visual matrix pattern were generated; a high semantic set which lends itself to long-term memory support and a low semantic set which does so to a lesser extent. The initial block of empirical work aimed to establish the characteristics of the patterns sets. Superiority for the high semantic patterns was observed in terms of greater stability across increasing maintenance intervals. The benefit of increased presentation time was also shown to be greater for the high semantic pattern set indicating the importance of time in the semantic elaboration process. A second block of studies was then conducted to identify the implications of the two patterns sets for the functional architecture of working memory. In a secondary interference paradigm the pattern sets were shown to be differentially dependent on visual and verbal interference with low semantic patterns negatively affected by visual and not verbal interference and the opposite pattern observed for high semantic patterns. The use of executive and attentional interference paradigms demonstrated two levels of binding. Firstly, when attentional resources were continually captured by a secondary task, a degree of chunking was observed for both pattern sets, this is discussed in terms of passive binding on the basis of long-term knowledge in the absence of executive resources. In the absence of interference, effortful elaboration of the pattern sets is observed and this is greater for the high semantic patterns. This is discussed in terms of active binding with the involvement of executive resources. These findings are then discussed in terms of both the Cowan (2005) and Baddeley (2000) models and recent observations made by Baddeley et al (in press) to support a modification of the episodic buffer in Baddeley?s model to allow for both passive and active binding and how this leads to striking similarities between the two theoretical perspectives

A practical guide and software for analysing pairwise comparison experiments

Most popular strategies to capture subjective judgments from humans involve the construction of a unidimensional relative measurement scale, representing order preferences or judgments about a set of objects or conditions. This information is generally captured by means of direct scoring, either in the form of a Likert or cardinal scale, or by comparative judgments in pairs or sets. In this sense, the use of pairwise comparisons is becoming increasingly popular because of the simplicity of this experimental procedure. However, this strategy requires non-trivial data analysis to aggregate the comparison ranks into a quality scale and analyse the results, in order to take full advantage of the collected data. This paper explains the process of translating pairwise comparison data into a measurement scale, discusses the benefits and limitations of such scaling methods and introduces a publicly available software in Matlab. We improve on existing scaling methods by introducing outlier analysis, providing methods for computing confidence intervals and statistical testing and introducing a prior, which reduces estimation error when the number of observers is low. Most of our examples focus on image quality assessment.Comment: Code available at https://github.com/mantiuk/pwcm

Evaluation of changes in image appearance with changes in displayed image size

This research focused on the quantification of changes in image appearance when images are displayed at different image sizes on LCD devices. The final results provided in calibrated Just Noticeable Differences (JNDs) on relevant perceptual scales, allowing the prediction of sharpness and contrast appearance with changes in the displayed image size. A series of psychophysical experiments were conducted to enable appearance predictions. Firstly, a rank order experiment was carried out to identify the image attributes that were most affected by changes in displayed image size. Two digital cameras, exhibiting very different reproduction qualities, were employed to capture the same scenes, for the investigation of the effect of the original image quality on image appearance changes. A wide range of scenes with different scene properties was used as a test-set for the investigation of image appearance changes with scene type. The outcomes indicated that sharpness and contrast were the most important attributes for the majority of scene types and original image qualities. Appearance matching experiments were further conducted to quantify changes in perceived sharpness and contrast with respect to changes in the displayed image size. For the creation of sharpness matching stimuli, a set of frequency domain filters were designed to provide equal intervals in image quality, by taking into account the system’s Spatial Frequency Response (SFR) and the observation distance. For the creation of contrast matching stimuli, a series of spatial domain S-shaped filters were designed to provide equal intervals in image contrast, by gamma adjustments. Five displayed image sizes were investigated. Observers were always asked to match the appearance of the smaller version of each stimulus to its larger reference. Lastly, rating experiments were conducted to validate the derived JNDs in perceptual quality for both sharpness and contrast stimuli. Data obtained by these experiments finally converted into JND scales for each individual image attribute. Linear functions were fitted to the final data, which allowed the prediction of image appearance of images viewed at larger sizes than these investigated in this research