198 research outputs found
Contribution To Signalling Of 3d Video Streams In Communication Systems Using The Session Initiation Protocol
Las tecnologĂas de vĂdeo en 3D han estado al alza en los Ăşltimos años, con abundantes avances
en investigaciĂłn unidos a una adopciĂłn generalizada por parte de la industria del cine, y una
importancia creciente en la electrónica de consumo. Relacionado con esto, está el concepto
de vĂdeo multivista, que abarca el vĂdeo 3D, y puede definirse como un flujo de vĂdeo
compuesto de dos o más vistas. El vĂdeo multivista permite prestaciones avanzadas de vĂdeo,
como el vĂdeo estereoscĂłpico, el “free viewpoint video”, contacto visual mejorado mediante
vistas virtuales, o entornos virtuales compartidos.
El propĂłsito de esta tesis es salvar un obstáculo considerable de cara al uso de vĂdeo multivista
en sistemas de comunicaciĂłn: la falta de soporte para esta tecnologĂa por parte de los
protocolos de señalizaciĂłn existentes, que hace imposible configurar una sesiĂłn con vĂdeo
multivista mediante mecanismos estándar. Asà pues, nuestro principal objetivo es la extensión
del Protocolo de Inicio de SesiĂłn (SIP) para soportar la negociaciĂłn de sesiones multimedia con
flujos de vĂdeo multivista.
Nuestro trabajo se puede resumir en tres contribuciones principales. En primer lugar, hemos
definido una extensiĂłn de señalizaciĂłn para configurar sesiones SIP con vĂdeo 3D. Esta
extensiĂłn modifica el Protocolo de DescripciĂłn de SesiĂłn (SDP) para introducir un nuevo
atributo de nivel de medios, y un nuevo tipo de dependencia de descodificaciĂłn, que
contribuyen a describir los formatos de vĂdeo 3D que pueden emplearse en una sesiĂłn, asĂ
como la relaciĂłn entre los flujos de vĂdeo que componen un flujo de vĂdeo 3D.
La segunda contribución consiste en una extensión a SIP para manejar la señalización de
videoconferencias con flujos de vĂdeo multivista. Se definen dos nuevos paquetes de eventos
SIP para describir las capacidades y topologĂa de los terminales de conferencia, por un lado, y
la configuración espacial y mapeo de flujos de una conferencia, por el otro. También se
describe un mecanismo para integrar el intercambio de esta informaciĂłn en el proceso de
inicio de una conferencia SIP.
Como tercera y Ăşltima contribuciĂłn, introducimos el concepto de espacio virtual de una
conferencia, o un sistema de coordenadas que incluye todos los objetos relevantes de la
conferencia (como dispositivos de captura, pantallas, y usuarios). Explicamos cĂłmo el espacio
virtual se relaciona con prestaciones de conferencia como el contacto visual, la escala de vĂdeo
y la fidelidad espacial, y proporcionamos reglas para determinar las prestaciones de una
conferencia a partir del análisis de su espacio virtual, y para generar espacios virtuales durante
la configuraciĂłn de conferencias
Stereoscopic high dynamic range imaging
Two modern technologies show promise to dramatically increase immersion in
virtual environments. Stereoscopic imaging captures two images representing
the views of both eyes and allows for better depth perception. High dynamic
range (HDR) imaging accurately represents real world lighting as opposed to
traditional low dynamic range (LDR) imaging. HDR provides a better contrast
and more natural looking scenes. The combination of the two technologies in
order to gain advantages of both has been, until now, mostly unexplored due to
the current limitations in the imaging pipeline. This thesis reviews both fields,
proposes stereoscopic high dynamic range (SHDR) imaging pipeline outlining the
challenges that need to be resolved to enable SHDR and focuses on capture and
compression aspects of that pipeline.
The problems of capturing SHDR images that would potentially require two
HDR cameras and introduce ghosting, are mitigated by capturing an HDR and
LDR pair and using it to generate SHDR images. A detailed user study compared
four different methods of generating SHDR images. Results demonstrated that
one of the methods may produce images perceptually indistinguishable from the
ground truth.
Insights obtained while developing static image operators guided the design
of SHDR video techniques. Three methods for generating SHDR video from an
HDR-LDR video pair are proposed and compared to the ground truth SHDR
videos. Results showed little overall error and identified a method with the least
error.
Once captured, SHDR content needs to be efficiently compressed. Five SHDR
compression methods that are backward compatible are presented. The proposed
methods can encode SHDR content to little more than that of a traditional single
LDR image (18% larger for one method) and the backward compatibility property
encourages early adoption of the format.
The work presented in this thesis has introduced and advanced capture and
compression methods for the adoption of SHDR imaging. In general, this research
paves the way for a novel field of SHDR imaging which should lead to improved
and more realistic representation of captured scenes
Blickpunktabhängige Computergraphik
Contemporary digital displays feature multi-million pixels at ever-increasing refresh rates. Reality, on the other hand, provides us with a view of the world that is continuous in space and time. The discrepancy between viewing the physical world and its sampled depiction on digital displays gives rise to perceptual quality degradations. By measuring or estimating where we look, gaze-contingent algorithms aim at exploiting the way we visually perceive to remedy visible artifacts. This dissertation presents a variety of novel gaze-contingent algorithms and respective perceptual studies. Chapter 4 and 5 present methods to boost perceived visual quality of conventional video footage when viewed on commodity monitors or projectors. In Chapter 6 a novel head-mounted display with real-time gaze tracking is described. The device enables a large variety of applications in the context of Virtual Reality and Augmented Reality. Using the gaze-tracking VR headset, a novel gaze-contingent render method is described in Chapter 7. The gaze-aware approach greatly reduces computational efforts for shading virtual worlds. The described methods and studies show that gaze-contingent algorithms are able to improve the quality of displayed images and videos or reduce the computational effort for image generation, while display quality perceived by the user does not change.Moderne digitale Bildschirme ermöglichen immer höhere Auflösungen bei ebenfalls steigenden Bildwiederholraten. Die Realität hingegen ist in Raum und Zeit kontinuierlich. Diese Grundverschiedenheit führt beim Betrachter zu perzeptuellen Unterschieden. Die Verfolgung der Aug-Blickrichtung ermöglicht blickpunktabhängige Darstellungsmethoden, die sichtbare Artefakte verhindern können. Diese Dissertation trägt zu vier Bereichen blickpunktabhängiger und wahrnehmungstreuer Darstellungsmethoden bei. Die Verfahren in Kapitel 4 und 5 haben zum Ziel, die wahrgenommene visuelle Qualität von Videos für den Betrachter zu erhöhen, wobei die Videos auf gewöhnlicher Ausgabehardware wie z.B. einem Fernseher oder Projektor dargestellt werden. Kapitel 6 beschreibt die Entwicklung eines neuartigen Head-mounted Displays mit Unterstützung zur Erfassung der Blickrichtung in Echtzeit. Die Kombination der Funktionen ermöglicht eine Reihe interessanter Anwendungen in Bezug auf Virtuelle Realität (VR) und Erweiterte Realität (AR). Das vierte und abschließende Verfahren in Kapitel 7 dieser Dissertation beschreibt einen neuen Algorithmus, der das entwickelte Eye-Tracking Head-mounted Display zum blickpunktabhängigen Rendern nutzt. Die Qualität des Shadings wird hierbei auf Basis eines Wahrnehmungsmodells für jeden Bildpixel in Echtzeit analysiert und angepasst. Das Verfahren hat das Potenzial den Berechnungsaufwand für das Shading einer virtuellen Szene auf ein Bruchteil zu reduzieren. Die in dieser Dissertation beschriebenen Verfahren und Untersuchungen zeigen, dass blickpunktabhängige Algorithmen die Darstellungsqualität von Bildern und Videos wirksam verbessern können, beziehungsweise sich bei gleichbleibender Bildqualität der Berechnungsaufwand des bildgebenden Verfahrens erheblich verringern lässt
Perceptually Optimized Visualization on Autostereoscopic 3D Displays
The family of displays, which aims to visualize a 3D scene with realistic depth, are known as "3D displays". Due to technical limitations and design decisions, such displays create visible distortions, which are interpreted by the human vision as artefacts. In absence of visual reference (e.g. the original scene is not available for comparison) one can improve the perceived quality of the representations by making the distortions less visible. This thesis proposes a number of signal processing techniques for decreasing the visibility of artefacts on 3D displays.
The visual perception of depth is discussed, and the properties (depth cues) of a scene which the brain uses for assessing an image in 3D are identified. Following the physiology of vision, a taxonomy of 3D artefacts is proposed. The taxonomy classifies the artefacts based on their origin and on the way they are interpreted by the human visual system.
The principles of operation of the most popular types of 3D displays are explained. Based on the display operation principles, 3D displays are modelled as a signal processing channel. The model is used to explain the process of introducing distortions. It also allows one to identify which optical properties of a display are most relevant to the creation of artefacts. A set of optical properties for dual-view and multiview 3D displays are identified, and a methodology for measuring them is introduced. The measurement methodology allows one to derive the angular visibility and crosstalk of each display element without the need for precision measurement equipment. Based on the measurements, a methodology for creating a quality profile of 3D displays is proposed. The quality profile can be either simulated using the angular brightness function or directly measured from a series of photographs. A comparative study introducing the measurement results on the visual quality and position of the sweet-spots of eleven 3D displays of different types is presented. Knowing the sweet-spot position and the quality profile allows for easy comparison between 3D displays. The shape and size of the passband allows depth and textures of a 3D content to be optimized for a given 3D display.
Based on knowledge of 3D artefact visibility and an understanding of distortions introduced by 3D displays, a number of signal processing techniques for artefact mitigation are created. A methodology for creating anti-aliasing filters for 3D displays is proposed. For multiview displays, the methodology is extended towards so-called passband optimization which addresses Moiré, fixed-pattern-noise and ghosting artefacts, which are characteristic for such displays. Additionally, design of tuneable anti-aliasing filters is presented, along with a framework which allows the user to select the so-called 3d sharpness parameter according to his or her preferences. Finally, a set of real-time algorithms for view-point-based optimization are presented. These algorithms require active user-tracking, which is implemented as a combination of face and eye-tracking. Once the observer position is known, the image on a stereoscopic display is optimised for the derived observation angle and distance. For multiview displays, the combination of precise light re-direction and less-precise face-tracking is used for extending the head parallax. For some user-tracking algorithms, implementation details are given, regarding execution of the algorithm on a mobile device or on desktop computer with graphical accelerator
Asymmetric 3D video coding based on regions of perceptual relevance
This dissertation presents a study and experimental research on asymmetric coding of
stereoscopic video. A review on 3D technologies, video formats and coding is rst presented
and then particular emphasis is given to asymmetric coding of 3D content and
performance evaluation methods, based on subjective measures, of methods using asymmetric
coding.
The research objective was de ned to be an extension of the current concept of asymmetric
coding for stereo video. To achieve this objective the rst step consists in de ning
regions in the spatial dimension of auxiliary view with di erent perceptual relevance
within the stereo pair, which are identi ed by a binary mask. Then these regions are
encoded with better quality (lower quantisation) for the most relevant ones and worse
quality (higher quantisation) for the those with lower perceptual relevance. The actual
estimation of the relevance of a given region is based on a measure of disparity according
to the absolute di erence between views. To allow encoding of a stereo sequence using
this method, a reference H.264/MVC encoder (JM) has been modi ed to allow additional
con guration parameters and inputs. The nal encoder is still standard compliant.
In order to show the viability of the method subjective assessment tests were performed
over a wide range of objective qualities of the auxiliary view. The results of these tests
allow us to prove 3 main goals. First, it is shown that the proposed method can be
more e cient than traditional asymmetric coding when encoding stereo video at higher
qualities/rates. The method can also be used to extend the threshold at which uniform
asymmetric coding methods start to have an impact on the subjective quality perceived
by the observers. Finally the issue of eye dominance is addressed. Results from stereo
still images displayed over a short period of time showed it has little or no impact on the
proposed method
NASA Tech Briefs, January 1995
Topics include: Sensors; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences; Books and Report
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View synthesis for depth from motion 3D x-ray imaging.
The depth from motion or kinetic depth X-ray imaging (KDEX) technique is designed to enhance the luggage screening at airport checkpoints. The technique requires multiple views of the luggage to be obtained from an arrangement of linear X-ray detector arrays. This research investigated a solution to the unique problems defined when considering the possibility of replacing some of the X-ray sensor views with synthetic images. If sufficiently high quality synthetic images can be generated then intermediary X-ray sensors can be removed to minimise the hardware requirements and improve the commercial viability of the KDEX technique. Existing image synthesis algorithms are developed for visible light images. Due to fundamental differences between visible light and X-ray images, those algorithms are not directly applicable to the X-ray scenario. The conditions imposed by the X-ray images have instigated the original research and novel algorithm development and experimentation that form the body of this work. A voting based dual criteria multiple X-ray images synthesis algorithm (V-DMX) is proposed to exploit the potential of two matching criteria and information contained in a sequence of images. The V-DMX algorithm is divided into four stages
NASA Tech Briefs, December 1989
Topics include: Electronic Components and Circuits. Electronic Systems, Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Fabrication Technology, Mathematics and Information Sciences, and Life Sciences
Augmented Reality
Augmented Reality (AR) is a natural development from virtual reality (VR), which was developed several decades earlier. AR complements VR in many ways. Due to the advantages of the user being able to see both the real and virtual objects simultaneously, AR is far more intuitive, but it's not completely detached from human factors and other restrictions. AR doesn't consume as much time and effort in the applications because it's not required to construct the entire virtual scene and the environment. In this book, several new and emerging application areas of AR are presented and divided into three sections. The first section contains applications in outdoor and mobile AR, such as construction, restoration, security and surveillance. The second section deals with AR in medical, biological, and human bodies. The third and final section contains a number of new and useful applications in daily living and learning
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