Abstract: The volume of Internet video is growing, and is expected to exceed 57 percent of global consumer Internet traffic by 2014. Peer-to-Peer technology can help delivering this massive volume of traffic in a cost-efficient, scalable, and reliable manner. However, single bitrate streaming is not sufficient given today’s device and network connection diversity. A possible solution to this problem is provided by layered coding techniques, such as Scalable Video Coding, which allow addressing this diversity by providing content in various qualities within a single bitstream. In this paper we propose a new self-adapting piece-picking algorithm for downloading layered video streams, called Deftpack. Our algorithm significantly reduces the number of stalls, minimises the frequency of quality changes during playback, and maximizes the effective usage of the available bandwidth. Deftpack is the first algorithm that is specifically crafted to take all these three quality dimensions into account simultaneously, thus increasing the overall quality of experience. Additionally, Deftpack can be integrated into Bittorrent-based P2P systems and so has the chance of large-scale deployment. Our results from realistic swarm simulations show that Deftpack significantly outperforms previously proposed algorithms for retrieving layered content when all three quality dimensions are taken into account.

Abstract: This paper describes the implementation of a VLC media player plugin enabling Dynamic Adaptive Streaming over HTTP (DASH). DASH is an emerging ISO/IEC MPEG and 3GPP standard for HTTP streaming. It aims to standardize formats enabling segmented progressive download by exploiting existing Internet infrastructure as such. Our implementation of these formats as described in this paper is based on the well-known VLC. Hence, it is fully integrated into the VLC structure and has been also submitted to the VLC development team for consideration in future releases of VLC. Therefore, it is licensed under the GNU Lesser General Public License (LGPL). The plugin provides a very flexible structure that could be easily extended with respect to different adaptation logics or profiles of the DASH standard. As a consequence, the plugin enables the integration of a variety of adaptation logics and comparison thereof, making it attractive for the research community.

Abstract: In this paper, we present a multimedia test-bed enabling session mobility in the context of the emerging ISO/IEC MPEG standard, Dynamic Adaptive Streaming over HTTP (DASH). In general, session mobility is defined as the transfer of a running streaming session from one device to another device where it may need to be consumed in an adaptive way. The two main challenges are: (1) taking into account the new context of the device (e.g., capabilities) to which the session is transferred and (2) performing the actual transfer in a seamless and interoperable way. Our system addresses both challenges supported by a prototype implementation integrated into VLC. In anticipation of the results we can conclude that interoperability is achieved adopting existing standards while the performance of the system does not depend on these standards. That is, the modules responsible for the performance are usually not defined within such standards and left out for competition. However, our system is designed in an extensible way and is able to accommodate this fact.

Abstract: LIRe (Lucene Image Retrieval) is an open source library for content based image retrieval. Besides providing multiple common and state of the art retrieval mechanisms it allows for easy use on multiple platforms. LIRe is actively used for research, teaching and commercial applications. Due to its modular nature it can be used on process level (e.g. index images and search) as well as on image feature level. Developers and researchers can easily extend and modify LIRe to adapt it to their needs.

Abstract: Searching and retrieving videos in a meaningful way on the web is still an open problem. The integration of a user's context into search is one of the most promising approaches to enhance current search interfaces and algorithms. We performed two user studies investigating video search, video retrieval, and video sharing behavior. In this paper we present an overview on the findings most promising for enhancing user experience in video retrieval. We propose a software prototype that implements an adaptive video retrieval system, that utilizes the users' intentions to provide better search results in a user interface adapted to the intentions and needs of users.

Abstract: Adaptive video streaming based on TCP/HTTP is becoming popular because of its ability to adapt to changing network conditions. We present an in-depth experimental analysis of the use of HTTP-based request-response streams for video streaming. In this scheme, video fragments are fetched by a client from the server, in smaller units called chunks, potentially via multiple parallel HTT P requests (TCP connections). A model for the achievable throughput is formulated.The model is validated by a broad range of streaming experiments, including an evaluation of TCP-friendliness. Our findings include that request-response streams are able to scale with the available bandwidth by increasing the chunk size or the number of concurrent streams. Several combinations of system parameters exhibiting TCP-friendliness are presented. We also evaluate the video streaming performance in terms of video quality in the presence of packet loss. Multiple request-response streams are able to maintain satisfactory performance, while a single TCP connection deteriorates rapidly with increasing packet loss. The results provide experimental evidence that HTTP-based request-response streams are a good alternative to classical TCP streaming

Abstract: Wireless router platforms based on the Linux operating system are becoming popular in consumers' home networks. The transmission of multimedia data or their use as media-aware network elements imposes high traffic and computational loads on these devices. Thus, it is interesting to evaluate the networking and processing capabilities of such home router platforms in order to assess their usefulness for improved multimedia services such as in-network H.264/SVC video stream adaptation. This paper presents a performance evaluation of three home router platforms representative for low-end, mid-range, and high-end devices. The scope of the evaluation is the performance of the Linux networking stack on these routers; results for both application-layer (TCP and UDP) transmission and kernel-level (UDP) traffic routing are given. The results show that both TCP and UDP throughputs are significantly below (less than half of) the outgoing (wired) links' nominal capacities and depend very much on the sizes of the transmitted data blocks. This clearly indicates that the networking performance is limited by the platforms' processing capabilities and the lack of mechanisms that offload networking tasks from the CPUs. This behaviour cannot be observed on today's PC systems and has to be considered when deploying multimedia services on these network devices. Furthermore, a detailed analysis of the Linux networking stack reveals that the performance is heavily impacted by the netfilter code, even when no packet filtering or network address translation is being performed. Considerable performance gains can be achieved when this netfilter code is bypassed.

Abstract: In this paper, we present an approach for in-network adaptation of H.264/SVC in the context of 802.11 wireless networks. It builds upon our previous work on an adaptive RTSP/RTP proxy which allows to adapt video streams on Linux-based home router platforms. The proposed approach tackles the throughput variations that occur as a consequence of the physical rate adaptation in 802.11 equipment caused by the mobility of clients. By combining monitoring information available exclusively on the wireless router with the ability to adapt scalable video streams on-the-fly, the proposed in-network adaptation approach allows to quickly adjust the video bit rate to the current link conditions. Instead of reacting on packet loss, our approach uses an increase in queueing delay at the router to detect phases of throughput degradation. This allows a higher responsiveness compared to traditional end-to-end approaches that rely solely on RTCP feedback. The behavior of our novel approach was evaluated in several mobility scenarios in an experimental test bed. The results obtained by streaming and adapting high-definition content clearly demonstrate the feasibility and benefits of this approach.

Abstract: Today's omnipresent demand for access to multimedia content via diverse devices places new challenges on efficient content delivery. This work introduces the concept of Scalable Video Coding (SVC) tunneling developed in the EU FP7 ALICANTE project and shows that the quality impact of the transcoding steps for a transcoding chain from MPEG-2 to SVC and back to MPEG-2 accumulates to a PSNR reduction of up to 2.1 dB for transcoding at fixed target bitrate points. We also discuss research challenges and open issues in SVC tunneling.

Abstract: Today's omnipresent demand for access to multimedia content via diverse devices places new challenges on efficient content delivery. While the Scalable Video Coding (SVC) extension of Advanced Video Coding (AVC) has proven to be a useful tool for the advanced delivery of video content, it has not yet found major adoption in practice. This paper introduces the concept of SVC tunneling developed in the EU FP7 ALICANTE project, which attempts to provide device-independent access to media resources at reduced network load. For SVC tunneling, video transcoding is performed at the ingress/egress points of the network, which may impact the video quality. We show that the quality impact of these transcoding steps for a transcoding chain from MPEG-2 to SVC and back to MPEG-2 accumulates to a PSNR reduction of up to 2.1 dB for transcoding at fixed target bitrates. We also discuss research challenges and open issues in SVC tunneling.

Abstract: In this position paper we introduce the idea of generating a superior view of a large social event, based on user-generated -- crowdsourced -- content. Instead of just collecting and making them available in a raw form (as social platforms like YouTube), we automatically generate semantically coherent summarizations of the entire event. The individual consuming user gets thus a compact view generated by a large number of producing users. We call this idea the "Vision of Crowds". A case study has been conducted at a social event where we used user-generated content to automatically generate live reports about that event. Furthermore, we have implemented a GUI that allows users to interactively compose personalized video summaries, based on the user-generated data collected at the case study.

Abstract: With the advent of the information age and the increasing size and complexity of multimedia databases, the question of how to support users in getting access and insight into those large databases has become immensely important. While traditional content-based retrieval approaches provide query-driven access under the assumption that the users' information needs are clearly specified, modern content-based exploration approaches support users in browsing and navigating through multimedia databases in the case of imprecise or even unknown information needs. By means of interactive graphical user interfaces, exploration approaches offer a convenient and intuitive access to unknown multimedia databases which becomes even more important with the arrival of powerful mobile devices. In this paper, we formulate challenges of user-centric multimedia exploration with a particular focus on large-scale multimedia databases. We claim that adaptability and scalability should be researched on both conceptual as well as technical level in order to model multimedia exploration approaches which are able to cope with millions of multimedia objects in near-realtime.

Abstract: Self-organizing overlay networks have received a lot of attention in the recent years. However, despite the popularity of content-aware and topology-aware overlay networks, surprisingly little research has been done to combine both approaches. In this paper, we create robust and flexible overlay networks that we call “Flocks”, which can be content-aware, topology-aware, or a combination of both. We model affinity with interests and properties and show the resulting overlay networks work in a decentralized, self-organizing way, and stabilize quickly.

Abstract: The term Universal Multimedia Experience (UME) has gained momentum and is well recognized within the research community. As this approach puts the user into the center stage, additional complexity is added to the overall quality assessment problem which calls for a scientific framework to capture, measure, quantify, judge, and explain the user experience. In previous work we have proposed the annotation of multimedia content with sensory effect metadata that can be used to stimulate also other senses than vision or audition. In this paper we report first results obtained from subjective tests in the area of sensory effects attached to traditional multimedia presentations such as movies that shall lead to an enhanced, unique, and worthwhile user experience.

Abstract: In previous and related work sensory effects are presented as a tool for increasing the user experience of multimedia presentations by stimulating also other senses than vision or audition. In this paper we primarily investigated the relationship of the Quality of Experience (QoE) due to various video bit-rates of multimedia contents annotated with sensory effects (e.g., wind, vibration, light). Therefore, we defined a subjective quality assessment methodology based on standardized methods. The paper describes the test environment, its setup, and conditions in detail. Furthermore, we experimented with a novel voting device that allows for continuous voting feedback during a sequence in addition to the overall quality voting at the end of each sequence. The results obtained from the subjective quality assessment are presented and discussed thoroughly. In anticipation of the results we can report an improvement of the quality of the multimedia experience thanks to the sensory effects.

Abstract: In the past years the amount of multimedia content on the Internet or in home networks has been drastically increasing. Instead of buying traditional media (such as CDs or DVDs) users tend to buy online media. This leads to the difficulty of managing the content (e.g., movies, images). A vast amount of tools for content management exists but they are mainly focusing on one type of content (e.g., only images). Furthermore, most of the available tools are not configurable to the user’s preferences and cannot be accessed by different devices (e.g., TV, computer, mobile phone) in the home network. In this paper we present a UPnP A/V-based system for managing and sharing audio/visual content in home environments which is configurable to the user’s preferences. Furthermore, the paper depicts how this system can be used to improve the user experience by using MPEG-V.