Automatic 3DTV Quality Assessment Based On Depth Perception Analysis

Quality assessment is a key factor for stereoscopic 3D video content as some observers are affected by visual discomfort in the eye when viewing 3D video, especially when combining positive and negative parallax with fast motion. In this paper, we propose techniques to assess objective quality related to motion and depth maps, which facilitate depth perception analysis. Subjective tests were carried out in order to understand the source of the problem. Motion is an important feature affecting 3D experience but also often the cause of visual discomfort. The automatic algorithm developed tries to quantify the impact on viewer experience when common cases of discomfort occur, such as high-motion sequences, scene changes with abrupt parallax changes, or complete absence of stereoscopy, with a goal of preventing the viewer from having a bad stereoscopic experience.

Dynamic gamma frequency feedback coupling between higher and lower order visual cortices underlies perceptual completion in humans

To perceive a coherent environment, incomplete or overlapping visual forms must be integrated into meaningful coherent percepts, a process referred to as ?Gestalt? formation or perceptual completion. Increasing evidence suggests that this process engages oscillatory neuronal activity in a distributed neuronal assembly. A separate line of evidence suggests that Gestalt formation requires top-down feedback from higher order brain regions to early visual cortex. Here we combine magnetoencephalography (MEG) and effective connectivity analysis in the frequency domain to specifically address the effective coupling between sources of oscillatory brain activity during Gestalt formation. We demonstrate that perceptual completion of two-tone ?Mooney? faces induces increased gamma frequency band power (55?71 Hz) in human early visual, fusiform and parietal cortices. Within this distributed neuronal assembly fusiform and parietal gamma oscillators are coupled by forward and backward connectivity during Mooney face perception, indicating reciprocal influences of gamma activity between these higher order visual brain regions. Critically, gamma band oscillations in early visual cortex are modulated by top-down feedback connectivity from both fusiform and parietal cortices. Thus, we provide a mechanistic account of Gestalt perception in which gamma oscillations in feature sensitive and spatial attention-relevant brain regions reciprocally drive one another and convey global stimulus aspects to local processing units at low levels of the sensory hierarchy by top-down feedback. Our data therefore support the notion of inverse hierarchical processing within the visual system underlying awareness of coherent percepts.

Luz industrial e imagen tecnificada: de Moholy Nagy al C.A.V.S. (Center for Advanced Visual Studies)

El desarrollo de la tecnología de la luz implicará la transformación de la vida social, cultural y económica. Tanto las consideraciones espaciales del Movimiento Moderno, como los efectos producidos por la segunda Guerra Mundial, tendrán efectos visibles en las nuevas configuraciones espaciales y en la relación simbiótica y recíproca que se dará entre ideología y tecnología. La transformación en la comprensión de la articulación espacial, asociada al desarrollo tecnológico, afectará al modo en que este espacio es experimentado y percibido. El espacio expositivo y el espacio escénico se convertirán en laboratorio práctico donde desarrollar y hacer comprensible todo el potencial ilusorio de la luz, la proyección y la imagen, como parámetros modificadores y dinamizadores del espacio arquitectónico. Esta experimentación espacial estará precedida por la investigación y creación conceptual en el mundo plástico, donde los nuevos medios mecánicos serán responsables de la construcción de una nueva mirada moderna mediatizada por los elementos técnicos. La experimentación óptica, a través de la fotografía, el cine, o el movimiento de la luz y su percepción, vinculada a nuevos modos de representación y comunicación, se convertirá en elemento fundamental en la configuración espacial. Este ámbito de experimentación se hará patente en la Escuela de la Bauhaus, de la mano de Gropius, Schlemmer o Moholy Nagy entre otros; tanto en reflexiones teóricas como en el desarrollo de proyectos expositivos, arquitectónicos o teatrales, que evolucionarán en base a la tecnología y la modificación de la relación con el espectador. El espacio expositivo y el espacio escénico se tomarán como oportunidad de investigación espacial y de análisis de los modos de percepción, convirtiéndose en lugares de experimentación básicos para el aprendizaje. El teatro se postula como punto de encuentro entre el arte y la técnica, cobrando especial importancia la intersección con otras disciplinas en la definición espacial. Las múltiples innovaciones técnicas ligadas a los nuevos fundamentos teatrales en la modificación de la relación con la escena, que se producen a principios del siglo XX, tendrán como consecuencia la transformación del espacio en un espacio dinámico, tanto física como perceptivamente, que dará lugar a nuevas concepciones espaciales, muchas de ellas utópicas. La luz, la proyección y la creación de ilusión en base a estímulos visuales y sonoros, aparecen como elementos proyectuales efímeros e inmateriales, que tendrán una gran incidencia en el espacio y su modo de ser experimentado. La implicación de la tecnología en el arte conllevará modificaciones en la visualización, así como en la configuración espacial de los espacios destinados a esta. Destacaremos como propuesta el Teatro Total de Walter Gropius, en cuyo desarrollo se recogen de algún modo las experiencias espaciales y las investigaciones desarrolladas sobre la estructura formal de la percepción realizadas por Moholy Nagy, además de los conceptos acerca del espacio escénico desarrollados en el taller de Teatro de la Bauhaus por Oskar Schlemmer. En el Teatro Total, Gropius incorporará su propia visión de cuestiones que pertenecen a la tradición de la arquitectura teatral y las innovaciones conceptuales que estaban teniendo lugar desde finales del s.XIX, tales como la participación activa del público o la superación entre escena y auditorio, estableciendo en el proyecto una nueva relación perceptual entre sala, espectáculo y espectador; aumentando la sensación de inmersión, a través del uso de la física, la óptica, y la acústica, creando una energía concéntrica capaz de extenderse en todas direcciones. El Teatro Total será uno de los primeros ejemplos en los que desde el punto de partida del proyecto, se conjuga la imagen como elemento comunicativo con la configuración espacial. Las nuevas configuraciones escénicas tendrán como premisa de desarrollo la capacidad de transformación tanto perceptiva, como física. En la segunda mitad del s.XX, la creación de centros de investigación como el CAVS (The Center for Advanced Visual Studies,1967), o el EAT (Experiments in Art and Technology, 1966), favorecerán la colaboración interdisciplinar entre arte y ciencia, implicando a empresas de carácter tecnológico, como Siemens, HP, IBM o Philips, facilitando soporte técnico y económico para el desarrollo de nuevos sistemas. Esta colaboración interdisciplinar dará lugar a una serie de intervenciones espaciales que tendrán su mayor visibilidad en algunas Exposiciones Universales. El resultado será, en la mayoría de los casos, la creación de espacios de carácter inmersivo, donde se establecerá una relación simbiótica entre espacio, imagen, sonido, y espectador. La colocación del espectador en el centro de la escena y la disposición dinámica de imagen y sonido, crearán una particular narrativa espacial no lineal, concebida para la experiencia. Desde las primeras proyecciones de cine a la pantalla múltiple de los Eames, las técnicas espaciales de difusión del sonido en Stockhausen, o los experimentos con el movimiento físico interactivo, la imagen, la luz en movimiento y el sonido, quedan inevitablemente convertidos en material arquitectónico. ABSTRACT. Light technology development would lead to a social, cultural and economic transformation. Both spatial consideration of “Modern Movement” and Second World War effects on technology, would have a visible aftereffect on spatial configuration and on the symbiotic and mutual relationship between ideology & technology. Comprehension adjustment on the articulation of space together with technology development, would impact on how space is perceived and felt. Exhibition space and scenic space would turn into a laboratory where developing and making comprehensive all illusory potential of light, projection and image. These new parameters would modify and revitalize the architectonic space. as modifying and revitalizing parameters of architectonic space. Spatial experimentation would be preceded by conceptual creation and investigation on the sculptural field, where new mechanic media would be responsible for a fresh and modern look influenced by technical elements. Optical experimentation, through photography, cinema or light movement and its perception, would turn into essential components for spatial arrangement linked to new ways of performance and communication. This experimentation sphere would be clear at The Bauhaus School, by the hand of Gropius, Schlemmer or Moholy Nag among others; in theoretical, theatrical or architectural performance’s projects, that would evolve based on technology and also based on the transformation of the relationship with the observer. Exhibition and perfor-mance areas would be taken as opportunities of spatial investigation and for the analysis of the different ways of perception, thus becoming key places for learning. Theater is postulated as a meeting point between art and technique, taking on a new significance at its intersection with other disciplines working with spatial definition too. The multiple innovation techniques linked to the new foundations for the theater regarding stage relation, would have as a consequence the regeneration of the space. Space would turn dynamic, both physically and perceptibly, bringing innovative spatial conceptions, many of them unrealistic. Light, projection and illusory creation based on sound and visual stimulus would appear as intangible and momentary design components, which would have a great impact on the space and on the way it is experienced. Implication of technology in art would bring changes on the observer as well as on the spatial configuration of the art spaces2. It would stand out as a proposal Walter Groupis Total Theater, whose development would include somehow the spatial experiments and studies about formal structure of perception accomplished by Moholy Nagy besides the concepts regarding stage space enhanced at the Bauhaus Theater Studio by Oskar Schlemmer. Within Total Theater, Groupis would incorporate his own view about traditional theatric architecture and conceptual innovations that were taking place since the end of the nineteenth century, such as active audience participation or the diffusing limits between scene and audience, establishing a new perception relationship between auditorium, performance and audience, improving the feeling of immersion through the use of physics, optics and acoustics, creating a concentric energy capable of spreading in all directions. Total Theater would be one of the first example in which, from the beginning of the Project, image is combined as a communicating element with the spatial configuration. As a premise of development, new stage arrangement would have the capacity of transformation, both perceptive and physically. During the second half or the twentieth century, the creation of investigation centers such as CAVS (Center for Advanced Visual Studies, 1967) or EAT (Experiments in Art and Technology, 1966), would help to the interdisciplinary collaboration between art and science, involving technology companies like Siemens, HP, IBM or Philips, providing technical and economic support to the development of new systems. This interdisciplinary collaboration would give room to a series of spatial interventions which would have visibility in some Universal Exhibitions. The result would be, in most cases, the creation of immersive character spaces, where a symbiotic relationship would be stablished between space, image, sound and audience. The new location of the audience in the middle of the display, together with the dynamic arrangement of sound and image would create a particular, no lineal narrative conceived to be experienced. Since the first cinema projections, the multiple screen of Eames, the spatial techniques for sound dissemination at Stockhausen or the interactive physical movement experimentation, image, motion light and sound would turn inevitably into architectural material.

DESEMPENHO EM TESTES DE ATENÇÃO VISUAL E INTERFERÊNCIA DE ESTÍMULOS AUDITIVOS DE MOVIMENTO EM INDIVÍDUOS COM E SEM MEDO DE ALTURA

Desordens da ansiedade, especialmente a agorafobia e a desordem do pânico foram associadas a anormalidades das funções vestibulares. Evidências de que o controle do equilíbrio pode exigir habilidades atencionais também foram relatadas. Utilizando o medo de altura como modelo clínico onde sintomas ansiosos coexistem com anormalidades com a percepção espacial e controle do equilíbrio, este estudo investigou o desempenho em testes de atenção visual em voluntários normais com altos e baixos escores obtidos do Questionário de Acrofobia. O teste de rastreio visual foi realizado em 30 indivíduos (15 em cada grupo) enquanto ouviam dois tipos diferentes de estímulos auditivos. Na condição volume um som de 900 Hz era apresentado em ambos ouvidos durante 2 segundos seguidos de mais 2 segundos de silêncio. Na condição balanço , o mesmo som era apresentado durante 2 segundos ao ouvido direito seguido por 2 segundos ao ouvido esquerdo. Estímulos auditivos de movimento provocaram maior desconforto em ambos os grupos, mas nos indivíduos com maiores escores de acrofobia estes estímulos foram associados a um pior desempenho no teste visual. Embora muito limitado pela amostra experimental, este estudo sugere que o medo de altura pode estar associado à dependência visual para manutenção do equilíbrio e que poderia piorar o desempenho nos testes visuais devido à competição dos recursos neuro-cognitivos. Implicações experimentais e clínicas destes achados preliminares exigem outras pesquisas.

DESEMPENHO EM TESTES DE ATENÇÃO VISUAL E INTERFERÊNCIA DE ESTÍMULOS AUDITIVOS DE MOVIMENTO EM INDIVÍDUOS COM E SEM MEDO DE ALTURA

Desordens da ansiedade, especialmente a agorafobia e a desordem do pânico foram associadas a anormalidades das funções vestibulares. Evidências de que o controle do equilíbrio pode exigir habilidades atencionais também foram relatadas. Utilizando o medo de altura como modelo clínico onde sintomas ansiosos coexistem com anormalidades com a percepção espacial e controle do equilíbrio, este estudo investigou o desempenho em testes de atenção visual em voluntários normais com altos e baixos escores obtidos do Questionário de Acrofobia. O teste de rastreio visual foi realizado em 30 indivíduos (15 em cada grupo) enquanto ouviam dois tipos diferentes de estímulos auditivos. Na condição volume um som de 900 Hz era apresentado em ambos ouvidos durante 2 segundos seguidos de mais 2 segundos de silêncio. Na condição balanço , o mesmo som era apresentado durante 2 segundos ao ouvido direito seguido por 2 segundos ao ouvido esquerdo. Estímulos auditivos de movimento provocaram maior desconforto em ambos os grupos, mas nos indivíduos com maiores escores de acrofobia estes estímulos foram associados a um pior desempenho no teste visual. Embora muito limitado pela amostra experimental, este estudo sugere que o medo de altura pode estar associado à dependência visual para manutenção do equilíbrio e que poderia piorar o desempenho nos testes visuais devido à competição dos recursos neuro-cognitivos. Implicações experimentais e clínicas destes achados preliminares exigem outras pesquisas.

Feature integration in pattern perception

The human visual system is able to effortlessly integrate local features to form our rich perception of patterns, despite the fact that visual information is discretely sampled by the retina and cortex. By using a novel perturbation technique, we show that the mechanisms by which features are integrated into coherent percepts are scale-invariant and nonlinear (phase and contrast polarity independent). They appear to operate by assigning position labels or “place tags” to each feature. Specifically, in the first series of experiments, we show that the positional tolerance of these place tags in foveal, and peripheral vision is about half the separation of the features, suggesting that the neural mechanisms that bind features into forms are quite robust to topographical jitter. In the second series of experiment, we asked how many stimulus samples are required for pattern identification by human and ideal observers. In human foveal vision, only about half the features are needed for reliable pattern interpolation. In this regard, human vision is quite efficient (ratio of ideal to real ≈ 0.75). Peripheral vision, on the other hand is rather inefficient, requiring more features, suggesting that the stimulus may be relatively underrepresented at the stage of feature integration.

The neurological basis of conscious color perception in a blind patient

We have studied patient PB, who, after an electric shock that led to vascular insufficiency, became virtually blind, although he retained a capacity to see colors consciously. For our psychophysical studies, we used a simplified version of the Land experiments [Land, E. (1974) Proc. R. Inst. G. B. 47, 23–58] to learn whether color constancy mechanisms are intact in him, which amounts to learning whether he can assign a constant color to a surface in spite of changes in the precise wavelength composition of the light reflected from that surface. We supplemented our psychophysical studies with imaging ones, using functional magnetic resonance, to learn something about the location of areas that are active in his brain when he perceives colors. The psychophysical results suggested that color constancy mechanisms are severely defective in PB and that his color vision is wavelength-based. The imaging results showed that, when he viewed and recognized colors, significant increases in activity were restricted mainly to V1-V2. We conclude that a partly defective color system operating on its own in a severely damaged brain is able to mediate a conscious experience of color in the virtually total absence of other visual abilities.

Optical images of visible and invisible percepts in the primary visual cortex of primates

We optically imaged a visual masking illusion in primary visual cortex (area V-1) of rhesus monkeys to ask whether activity in the early visual system more closely reflects the physical stimulus or the generated percept. Visual illusions can be a powerful way to address this question because they have the benefit of dissociating the stimulus from perception. We used an illusion in which a flickering target (a bar oriented in visual space) is rendered invisible by two counter-phase flickering bars, called masks, which flank and abut the target. The target and masks, when shown separately, each generated correlated activity on the surface of the cortex. During the illusory condition, however, optical signals generated in the cortex by the target disappeared although the image of the masks persisted. The optical image thus was correlated with perception but not with the physical stimulus.

Lightness constancy in primary visual cortex

When the illumination of a visual scene changes, the quantity of light reflected from objects is altered. Despite this, the perceived lightness of the objects generally remains constant. This perceptual lightness constancy is thought to be important behaviorally for object recognition. Here we show that interactions from outside the classical receptive fields of neurons in primary visual cortex modulate neural responses in a way that makes them immune to changes in illumination, as is perception. This finding is consistent with the hypothesis that the responses of neurons in primary visual cortex carry information about surface lightness in addition to information about form. It also suggests that lightness constancy, which is sometimes thought to involve “higher-level” processes, is manifest at the first stage of visual cortical processing.

Motion perception: seeing and deciding.

The primate visual system offers unprecedented opportunities for investigating the neural basis of cognition. Even the simplest visual discrimination task requires processing of sensory signals, formation of a decision, and orchestration of a motor response. With our extensive knowledge of the primate visual and oculomotor systems as a base, it is now possible to investigate the neural basis of simple visual decisions that link sensation to action. Here we describe an initial study of neural responses in the lateral intraparietal area (LIP) of the cerebral cortex while alert monkeys discriminated the direction of motion in a visual display. A subset of LIP neurons carried high-level signals that may comprise a neural correlate of the decision process in our task. These signals are neither sensory nor motor in the strictest sense; rather they appear to reflect integration of sensory signals toward a decision appropriate for guiding movement. If this ultimately proves to be the case, several fascinating issues in cognitive neuroscience will be brought under rigorous physiological scrutiny.

Illusory contours activate specific regions in human visual cortex: evidence from functional magnetic resonance imaging.

The neural basis for perceptual grouping operations in the human visual system, including the processes which generate illusory contours, is fundamental to understanding human vision. We have employed functional magnetic resonance imaging to investigate these processes noninvasively. Images were acquired on a GE Signa 1.5T scanner equipped for echo planar imaging with an in-plane resolution of 1.5 x 1.5 mm and slice thicknesses of 3.0 or 5.0 mm. Visual stimuli included nonaligned inducers (pacmen) that created no perceptual contours, similar inducers at the corners of a Kanizsa square that created illusory contours, and a real square formed by continuous contours. Multiple contiguous axial slices were acquired during baseline, visual stimulation, and poststimulation periods. Activated regions were identified by a multistage statistical analysis of the activation for each volume element sampled and were compared across conditions. Specific brain regions were activated in extrastriate cortex when the illusory contours were perceived but not during conditions when the illusory contours were absent. These unique regions were found primarily in the right hemisphere for all four subjects and demonstrate that specific brain regions are activated during the kind of perceptual grouping operations involved in illusory contour perception.

Parameters affecting conscious versus unconscious visual discrimination with damage to the visual cortex (V1).

When the visual (striate) cortex (V1) is damaged in human subjects, cortical blindness results in the contralateral visual half field. Nevertheless, under some experimental conditions, subjects demonstrate a capacity to make visual discriminations in the blind hemifield (blindsight), even though they have no phenomenal experience of seeing. This capacity must, therefore, be mediated by parallel projections to other brain areas. It is also the case that some subjects have conscious residual vision in response to fast moving stimuli or sudden changes in light flux level presented to the blind hemifield, characterized by a contentless kind of awareness, a feeling of something happening, albeit not normal seeing. The relationship between these two modes of discrimination has never been studied systematically. We examine, in the same experiment, both the unconscious discrimination and the conscious visual awareness of moving stimuli in a subject with unilateral damage to V1. The results demonstrate an excellent capacity to discriminate motion direction and orientation in the absence of acknowledged perceptual awareness. Discrimination of the stimulus parameters for acknowledged awareness apparently follows a different functional relationship with respect to stimulus speed, displacement, and stimulus contrast. As performance in the two modes can be quantitatively matched, the findings suggest that it should be possible to image brain activity and to identify the active areas involved in the same subject performing the same discrimination task, both with and without conscious awareness, and hence to determine whether any structures contribute uniquely to conscious perception.

Estudo do impacto visual de alguns sinais horizontais de trânsito: avaliação utilizando métodos da psicofísica

Neste trabalho são feitas comparações entre os principais sinais horizontais de trânsito (Parada Obrigatória, Faixa de Pedestre e Lombada) padronizados pelo Código de Trânsito Brasileiro (CTB), com modelos alternativos que sofreram variações na forma e/ou cor, alguns deles já usados em algumas cidades brasileiras, com o objetivo de identificar se essas alterações melhoram ou não a percepção do sinal (impacto visual). Para isso são utilizados dois métodos da Psicofísica. Numa primeira etapa a análise é feita utilizando o Método de Comparação aos Pares, para um grupo de quatro estímulos para cada sinal estudado. Em seguida, aplicando o Método de Estimativa das Categorias, foi avaliado o impacto visual do sinal horizontal de Parada Obrigatória quanto à presença ou ausência de orla externa. Por fim, também pelo Método de Comparação aos Pares, foi avaliado o impacto visual causado pelo uso conjugado de sinais horizontais em cruzamentos não semaforizados. Foram estudadas as combinações entre os sinais de parada obrigatória, faixa de pedestres e faixa de retenção. Os resultados obtidos permitem inferir as seguintes conclusões: as alterações na forma e cor propostas para os sinais de parada obrigatória e faixa de pedestres causam maior impacto visual quando comparadas ao modelo padronizado pelo CTB mas, no caso das lombadas, a sinalização padrão mostrou-se ser mais perceptível; quanto a presença ou não da orla externa no sinal de parada obrigatória, esta demonstrou ser positiva; o uso conjugado dos sinais de parada obrigatória, faixa de pedestres e faixa de retenção é a combinação que mais desperta a atenção dos usuários.

Visual Manifestations of Primary Metaphors Through Mise-en-scène Techniques

Grady distinguishes two main types of metaphor in order to provide a solution in the controversies stemming from the conceptual theory of metaphor: correlation-based metaphors and resemblance metaphors. In “correlation-based metaphors”, the source domain is sensory-motor, while the target domain is not. On the contrary, “resemblance metaphors” are originated by a physical or conceptual perception which is common in both domains, by the association of concepts with common features. Primary metaphors are the minimal units of correlation-based metaphors; they are inherent in human nature and the result of the nature of our brain, our body and the world that we inhabit. We acquire them automatically and we cannot avoid them. Furthermore, as corporal experiences are universal, so are primary metaphors. In this paper, I will argue that primary metaphors manifest themselves visually through scene-setting techniques such as composition, framing, camera movement or lighting. Film-makers can use the different aspects of mise-en-scène metaphorically in order to express abstract notions like evil, importance, control, relationship or confusion. Such visual manifestations, as also occurs with their verbal equivalents, frequently go unnoticed or have been used so often that they have become clichés. But the important thing to bear in mind is that their origin lies in a primary metaphor and due to this origin these kinds of film-making strategies have been so expressively successful.

Visual and optical performance and quality of life after implantation of posterior chamber phakic intraocular lens

Purpose To evaluate visual, optical, and quality of life (QoL) outcomes and intercorrelations after bilateral implantation of posterior chamber phakic intraocular lenses. Methods Twenty eyes with high to moderate myopia of 10 patients that underwent PRL implantation (Phakic Refractive Lens, Carl Zeiss Meditec AG) were examined. Refraction, visual acuity, photopic and low mesopic contrast sensitivity (CS) with and without glare, ocular aberrations, as well as QoL outcomes (National Eye Institute Refractive Error Quality of Life Instrument-42, NEI RQL-42) were evaluated at 12 months postoperatively. Results Significant improvement in uncorrected (UDVA) and best-corrected distance (CDVA) visual acuities were found postoperatively (p < 0.01), with significant reduction in spherical equivalent (p < 0.01). Low mesopic CS without glare was significantly better than measurements with glare for 1.5, 3, and 6 cycles/degree (p < 0.01). No significant correlations between higher order root mean square (RMS) with CDVA (r = −0.26, p = 0.27) and CS (r ≤ 0.45, p ≥ 0.05) were found. Postoperative binocular photopic CS for 12 cycles/degree and 18 cycles/degree correlated significantly with several RQL-42 scales. Glare index correlated significantly with CS measures and scotopic pupil size (r = −0.551, p = 0.04), but not with higher order RMS (r = −0.02, p = 0.94). Postoperative higher order RMS, postoperative primary coma and postoperative spherical aberration was significant higher for 5-mm pupil diameter (p < 0.01) compared with controls. Conclusions Correction of moderate to high myopia by means of PRL implantation had a positive impact on CS and QoL. The aberrometric increase induced by the surgery does not seem to limit CS and QoL. However, perception of glare is still a relevant disturbance in some cases possibly related to the limitation of the optical zone of the PRL.