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The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. We present a multi-level multi-overlay hybrid peer-to-peer live video system that enables players of Massively Multiplayer Online Games to simultaneously stream the video of their game and watch the game videos of other players. Each live video bitstream is encoded with rateless codes and multiple trees are used to transmit the encoded symbols. Trees are constructed dynamically with the aim to minimize the transmission rate at the source while maximizing the number of served peers and guaranteeing on-time delivery and reliability. ns-2 simulations and real measurements on the Internet show competitive performance in terms of start-up delay, playback lag, rejection rate, used bandwidth, continuity index, and video quality.

The growing availability of video provides many applications for the purpose of injury-control research. Video is recognized as a tool for the identification of common injury vignettes, or hazard scenarios, and has been applied predominantly across the sports and recreational realm. The primary advantage afforded by video analysis is the accuracy of data collection associated with events that often occur in a fraction of a second and may not be accurately reported by the injured party, parent, coach, or other observer. By enabling investigators to recreate the physical, social, and environmental factors that may contribute to the injury event or predispose to injury occurrence, video offers the ability to capture mechanisms of injury (both contact and noncontact), biomechanics associated with injury events, physiological and behavioral responses to impact, and a host of other outcomes. In this chapter, we discuss applications of video analysis for sports injury research. We then address methodological considerations and the five phases of the video analysis process ((1) conceptualization, (2) resources, (3) instrument development, (4) data collection, and (5) data analysis). Lastly, we present video analysis as a tool that allows data collection for validation of proposed theories and development of interventions.

Motion estimation in H.264/AVC supports quarter-pixel precision and is usually carried out in two phases: integer motion estimation (IME) and fractional motion estimation (FME). We have talked about IME in Chap.3. After IME finds an integer motion vector (IMV) for each of the 41 subblocks, FME performs motion search around the refinement center pointed to by IMV and further refines 41 IMVs into fractional MVs (FMVs) of quarter-pixel precision. FME interpolates half-pixels using a six-tap filter and then quarter-pixels a two-tap one. Nine positions are searched in both half refinement (one integer-pixel search center pointed to by IMV and 8 half-pixel positions) and then quarter refinement (1 half-pixel position and 8 quarter-pixel positions). The position with minimum residual error is chosen as the best match. FME can significantly improve the video quality (+0.3 to+0.5dB) and reduce bit-rate (20–37%) according to our experimental results. However, our profiling report shows that FME consumes more than 40% of the total encoding time. Therefore, an efficient hardware accelerator for FME is indispensable.

Digital Video Broadcasting for handheld terminals (DVB-H) is a broadcast system designed for high-speed data transmission in highly dispersive mobile channel conditions. This so-called “TV on Mobile” technology uses the Internet Protocol (IP) to carry highly compressed audio/video information; the ITU-T H.264 Advanced Video Coding (AVC) standard has been selected by the European Telecommunications Standards Institute (ETSI) as the video compression enabling technology. This choice, motivated by the good trade-off between coding efficiency and video quality, provides the further benefit of robustness against loss of parts of the received stream. As a matter of fact, transmission errors on the mobile channel can lead to IP datagram corruptions or losses; if not recovered by the prescribed Forward Error Correction (FEC) techniques, they can determine audio and video quality degradation. To face video degradation, Error Concealment strategies at the decoder can be efficiently tailored to the available hardware and computational resources of the receiving device, and do not require any changes in the encoding technique, nor any redundancy added to the transmitted data. Error Concealment refers to postprocessing techniques employed by the video decoder, which basically exploits the remaining spatial and temporal redundancy in the received video data to compensate the lost information. This chapter discusses the main features that make the H.264/AVC standard particularly suited to wireless video communications, and provides an overview of possible Error Concealment strategies that could be efficiently implemented in DVB-H devices, to compensate for errors and data losses due to the channel impairments.

Current digital broadcasting network throughput rates are insufficient to handle raw video data in real time, even if low spatial and temporal resolution (i.e. frame size and frame rate) has been selected. Towards alleviating the network bandwidth requirements for efficient transmission of audiovisual content, coding/compression techniques have been applied on raw video data, performing compression on both temporal and spatial redundancy of the content. More specifically, coding applications that are specialized and adapted in broadcasting digitally encoded audiovisual content have known an explosive growth in terms of development, deployment, and provision. Video coding is defined as the process of compressing and decompressing a digital video sequence, which results in lower data volumes, besides enabling the transmission of video signals over bandwidth-limited means, where uncompressed video signals would not be possible to be transmitted. In this multievolutionary environment, the new era of digital video broadcasting has arrived and the beyond typical analog-based transmission for broadcasting services is a fact, setting new research challenges for the assessment of Perceived Quality of Service (PQoS) under the latest video encoding and broadcasting standards. The majority of the compression standards have been proposed by the International Telecommunication Union (ITU) and the International Organization for Standardization (ISO) bodies, by introducing the following standards H.261, H.263, H.263+, H.263++, H.264, MPEG-1, MPEG-2, MPEG-4 and MPEG-4 Advanced Video Coding (AVC). Some of the aforementioned standards were developed in

Currently, H.264/AVC is adopted in many applications. In the existing coding standard, the MPEG-2 main profile which supports B pictures for bidirectional motion prediction is widely used in applications such as HDTV and DVD's. Therefore, transcoding the MPEG-2 main profile to the H.264/ AVC baseline profile is necessary for universal multimedia access. In this transcoding architecture including the group of pictures structure conversion, for fast re-estimation, the proposed algorithms adopt the adaptive search range selection through the linearity test of a predictive motion vector. And for fast mode decision, the reference region information is used. The proposed algorithms reduce the computational complexity while maintaining the video quality.