Content Adaptation Framework Research Articles

Low-delay single holoscopic 3D computer-generated image to multiview images

Due to the nature of holoscopic 3D (H3D) imaging technology, H3D cameras can capture more angular information than their conventional 2D counterparts. This is mainly attributed to the macrolens array which captures the 3D scene with slightly different viewing angles and generates holoscopic elemental images based on fly’s eyes imaging concept. However, this advantage comes at the cost of decreasing the spatial resolution in the reconstructed images. On the other hand, the consumer market is looking to find an efficient multiview capturing solution for the commercially available autostereoscopic displays. The autostereoscopic display provides multiple viewers with the ability to simultaneously enjoy a 3D viewing experience without the need for wearing 3D display glasses. This paper proposes a low-delay content adaptation framework for converting a single holoscopic 3D computer-generated image into multiple viewpoint images. Furthermore, it investigates the effects of varying interpolation step sizes on the converted multiview images using the nearest neighbour and bicubic sampling interpolation techniques. In addition, it evaluates the effects of changing the macrolens array size, using the proposed framework, on the perceived visual quality both objectively and subjectively. The experimental work is conducted on computer-generated H3D images with different macrolens sizes. The experimental results show that the proposed content adaptation framework can be used to capture multiple viewpoint images to be visualised on autostereoscopic displays.

Multi-Objective Optimization in Dynamic Content Adaptation of Slide Documents

In mobile web conferencing, slide decks should be optimized before delivery to meet the constraints and environments of target mobile devices. To deliver optimally adapted slides, a trade-off between the visual aspect and delivery time must be reached. Static adaptation methods are CPU-intensive, and require large storage space. The dynamic approach is attractive as the optimal version is created on the fly when the actual slide is to be shared. Existing dynamic solutions are optimized for the resolution of the target mobile device and use good visual quality settings. However, they do not control the resulting data size, which creates serious usability issues, such as increasing the delivery time. Prediction-based methods require much less memory and processing resources than static approaches while yielding an excellent user experience. In this paper, we propose a multi-objective dynamic content adaptation framework, in which we maximize the visual quality and minimize the delivery time simultaneously. We compare our solution with an ideal optimal point, called utopia, and with all the optimal solutions (Pareto front) provided by a static exhaustive system. The obtained results show that our framework yields solutions very close to the utopia and, for the majority of the documents tested, the obtained solutions are on the Pareto front.

Robust QoE-aware prediction-based dynamic content adaptation framework applied to slides documents in mobile Web conferencing

In mobile Web conferencing, enterprise documents are generally adapted into JPEG-based Web pages to be visualized on mobile devices. Dynamically identifying the optimal adapted content is very challenging, as a compromise between high visual quality and small delivery time must be made. In this paper, we propose a robust prediction-based dynamic content adaptation framework for JPEG and XHTML formats that computes near-optimal transcoding parameters dynamically with very few computations. The proposed framework is comprised of five methods making different compromises between computational complexity and accuracy. For JPEG, the average deviation from optimality (exhaustive method) is 6 % and 3 % respectively for two of the proposed methods. For XHTML, the average deviation from optimality is 3 % and 1 % respectively using the same two methods. Moreover, the methods reached optimality 30 % and 59 % of the time on the tested documents for JPEG and XHTML respectively, which makes the proposed framework very appealing.

Quality Prediction-Based Dynamic Content Adaptation Framework Applied to Collaborative Mobile Presentations

Today, professional documents, created in applications such as PowerPoint and Word, can be shared using ubiquitous mobile terminals connected to the Internet. GoogleDocs and EasyMeet are good examples of such collaborative web applications dedicated to professional documents. The static adaptation of professional documents has been studied extensively. Dynamic adaptation can be very useful and practical for interactive multimedia applications, because it allows the delivery of highly customized content to the end user without the need to generate and store multiple transcoded versions. In this paper, we propose a dynamic framework that enables us to estimate transcoding parameters on the fly to generate near-optimal adapted content for each user. The framework is compared to current dynamic methods as well as to static adaptation solutions. We show that the proposed framework provides a better tradeoff between quality and storage compared to other static and dynamic approaches. To quantify the quality of the adapted content, we introduce a measure of the quality of the experience based on the visual quality of the adapted content, as well as on the impact of its total delivery time. The framework has been tested on (but is not limited to) OpenOffice Impress presentations.

Improved BSDL-based content adaptation for JPEG 2000 and HD Photo (JPEG XR)

JPEG 2000 and HD Photo (JPEG XR) enable the coding of images with several adaptivity provisions. These provisions allow taking into account the constraints of diverse usage environments. However, the actual adaptation of the coded bitstreams requires additional system complexity. This paper investigates how JPEG 2000 and HD Photo can be used in a standardized and XML-based framework for format-independent content adaptation in the compressed domain. An analysis is provided of the cost of providing adaptivity in the compressed domain, in terms of loss of coding efficiency, as well as in terms of the complexity of the format-agnostic adaptation system used. This complexity is expressed in terms of execution times, memory consumption, and file size overhead of the XML descriptions. Using the outcome of our analysis, a number of improvements are proposed that allow reducing the complexity of XML-based adaptation for JPEG 2000 and HD Photo, in particular the use of compact XML descriptions and an adaptation chain based on the Simple API for XML (SAX). Compact XML descriptions contain a minimal amount of information for the purpose of adaptation—their use is enabled by introducing an additional lightweight pre- and post-processing step in the overall adaptation chain. Our results show that editing-style operations on JPEG 2000 and HD Photo bitstreams can be executed with a feasible complexity when relying on compact XML descriptions. These editing-style operations include exploiting spatial and quality scalability, as well as interactive extraction of regions-of-interest (ROIs). However, low-level operations in the compressed domain, such as rotating an image, cannot be supported, due to the need for entropy decoding and data reordering at macroblock or codeblock level.

DCAF: An MPEG-21 Dynamic Content Adaptation Framework

Universal Multimedia Access aims at providing a gratifying end user-experience by either adapting the content, be it static or dynamic, to suit the usage environment or adapting the usage environment, be it client- or server-centric, to suit content. This paper presents our MPEG-21 Dynamic Content Adaptation Framework, acronym DCAF, which uses a fusion of Genetic Algorithms and Strength Pareto Optimality to adapt content in order to suit the usage environment.

Efficient Execution of Service Composition for Content Adaptation in Pervasive Computing

Multimedia content adaptation has been proved to be an effective mechanism to mitigate the problem of devices and networks heterogeneity and constraints in pervasive computing environments. Moreover, it enables to deliver data taking into consideration the user's preferences and the context of his/her environment. In this paper, we present an algorithm for service composition and protocols for executing service composition plan. Both the algorithm and the protocols are implemented in our distributed content adaptation framework (DCAF) which provides a service-based content adaptation architecture. Finally, a performance evaluation of the algorithm and the protocols is presented.

Media Accessibility for Low-Vision Users in the MPEG-21 Multimedia Framework

Ethical and legal requirements have made accessibility a crucial feature in any information systems. This paper presents a content adaptation framework, based on the MPEG-21 standard, to help low-vision users have better accessibility to visual contents. We first present an overview of MPEG-21 Digital Item Adaptation (DIA) and the low-vision description tool which enables interoperable content adaptation. This description tool lists seven low-vision symptoms, namely loss of fine detail, lack of contrast, central vision loss, peripheral vision loss, hemianopia, light sensitivity, and need of light. Then we propose a systematic contrast-enhancement method to improve the content visibility for low-vision users, focusing on the first two symptoms. The effectiveness of the low-vision description tool and our adaptation framework is verified by some experiments with an adaptation test-bed. The major advantages of the proposed approach include 1) support of a wide range of low-vision conditions, and 2) customized content adaptation to specific characteristics of each user.

An optimized MPEG-21 BSDL framework for the adaptation of scalable bitstreams

A format-agnostic framework for content adaptation allows reaching a maximum number of users in heterogeneous multimedia environments. Such a framework typically relies on the use of scalable bitstreams. In this paper, we investigate the use of bitstreams compliant with the scalable extension of the H.264/MPEG-4 AVC standard in a format-independent framework for content adaptation. These bitstreams are scalable along the temporal, spatial, and SNR axis. To adapt these bitstreams, a format-independent adaptation engine is employed, driven by the MPEG-21 Bitstream Syntax Description Language (BSDL). MPEG-21 BSDL is a specification that allows generating high-level XML descriptions of the structure of a scalable bitstream. As such, the complexity of the adaptation of scalable bitstreams can be moved to the XML domain. Unfortunately, the current version of MPEG-21 BSDL cannot be used to describe the structure of large video bitstreams because the bitstream parsing process is characterized by an increasing memory consumption and a decreasing description generation speed. Therefore, in this paper, we describe a number of extensions to the MPEG-21 BSDL specification that make it possible to optimize the processing of bitstreams. Moreover, we also introduce a number of additional extensions necessary to describe the structure of scalable H.264/AVC bitstreams. Our performance analysis demonstrates that our extensions enable the bitstream parsing process to translate the structure of the scalable bitstreams into an XML document multiple times faster. Further, a constant and low memory consumption is obtained during the bitstream parsing process.

MPEG-21 bitstream syntax descriptions for scalable video codecs

In order to obtain a useful multichannel publication environment, a content producer has to respect the different terminal and network characteristics of the multimedia devices of its target audience. Embedded scalable video bitstreams, together with a complementary content adaptation framework, give the possibility to respond to heterogeneous usage environments. In this paper, temporally scalable H.264/MPEG-4 AVC encoded bitstreams and bitstreams encoded by relying on the fully-embedded MC-EZBC wavelet-based codec are used. The MPEG-21 Bitstream Syntax Description Language (BSDL) specification is used to generate high-level XML descriptions of the structure of a bitstream. As such, the adaptation of a scalable video stream can be realized in the XML domain, rather than on the bitstream itself. Different transformation technologies are compared to each other as well. Finally, a practical setup of a video streaming use case is discussed by relying on the MPEG-21 BSDL framework.