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  • 1.
    Eichhorn, Alexander
    et al.
    Simula Research Laboratory, Norway.
    Ni, Pengpeng
    Simula Research Laboratory, Norway.
    Pick your Layers wisely - A Quality Assessment of H.264 Scalable Video Coding for Mobile Devices2009Ingår i: ICC ’09. IEEE International Conference on Communications, Dresden, Germany, 2009Konferensbidrag (Refereegranskat)
  • 2.
    Ni, Pengpeng
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Towards Optimal Quality of Experience via Scalable Video Coding2009Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    To provide universal multimedia experience, multimedia streaming services need to transparently handle the variation and heterogeneity in operating environment. From the standpoint of streaming application, video adaptation techniques are intended to cope with the environmental variations by utilizing manipulations of the video content itself. Scalable video coding (SVC) schemes, like that suggested by the standards H.264 and its SVC extension, is highly attractive for designing a self-adaptive video streaming system. When SVC is employed in streaming system, the produced video stream can be then easily truncated or tailored to form several sub-streams which can be decoded separately to obtain a range of preferable picture size, quality and frame rate. However, questions about how to perform the adaptation using SVC and how much adaptation SVC enables are still remaining research issues. We still lack a thorough understanding of how to automate the scaling procedure in order to achieve an optimal video Quality-of-Experience for end users.

    Video QoE, depends highly on human perception. In this thesis, we introduce several video QoE studies around the usability of H.264 SVC. Several factors that contribute significantly to the overall QoEs have been identified and evaluated in these studies. As an example of application usage related factor, playback smoothness and application response time are critical performance measures which can benefit from temporal scalability. Targeting on applications that requires frequent interactivity, we propose a transcoding scheme that fully utilizes the benefits of Switching P and Switching I frames specified in H.264 to enhance video stream's temporal scalability.  Focusing on visual quality related factors, a series of carefully designed subjective quality assessment tests have been performed on mobile devices to investigate the effects of multi-dimensional scalability on human quality perception. Our study reveals that QoE degrades non-monotonically with bitrate and that scaling order preferences are content-dependent. Another study find out that the flickering effect caused by frequent switching between layers in SVC compliant bit-streams is highly related to the switching period. When the period is above a certain threshold, the flickering effect will disappear and layer switching should not be considered as harmful. We have also examined user perceived video quality in 3D virtual worlds. Our results show that the avatars' distance to the virtual screen in 3D worlds contribute significant to the video QoE, i.e., for a wide extent of distortion, there exists always a feasible virtual distance from where the distortion is not detectable for most of people, which makes sense to perform video adaptation.

    The work presented in this thesis is supposed to help improving the design of self adaptive video streaming services that can deliver video content independently of network technology and end-device capability while seeking the best possible experience for video.

  • 3.
    Ni, Pengpeng
    et al.
    Simula Research Laboratory, Norway .
    Eichorn, A
    Simula Research Laboratory, Norway .
    Griwodz, C.
    Simula Research Laboratory, Norway .
    Halvorsen, P.
    Simula Research Laboratory, Norway .
    Fine-grained scalable streaming from coarse-grained videos2009Ingår i: Proceedings of the International Workshop on Network and Operating System Support for Digital Audio and Video 2009, 2009, s. 103-108Konferensbidrag (Refereegranskat)
  • 4.
    Ni, Pengpeng
    et al.
    Simula Research Laboratory, Norway .
    Gaarder, F.
    Department of Informatics, University of Oslo, Norway .
    Griwodz, C.
    Department of Informatics, University of Oslo, Norway .
    Halvorsen, P.
    Department of Informatics, University of Oslo, Norway .
    Video streaming into virtual worlds: the effects of virtual screen distance and angle on perceived quality2009Ingår i: MM'09 - Proceedings of the 2009 ACM Multimedia Conference, with Co-located Workshops and Symposiums, 2009, s. 885-888Konferensbidrag (Refereegranskat)
    Abstract [en]

    There is an increasing trend to include streamed video data in 3D environments. Such environments allow potentially several concurrently visiblevideos on a single display device, and consequently, network and processing bottlenecks. As a first step towards an avoidance of such problems, we have performed subjective assessments using a 3D application prototype to determine how positioning of video in the 3D environment influences the user perception of reduced-quality videos. Using video clips from several genres, we have compared the influence of various ways to reduce video quality and users' perception of degraded quality. We evaluated the influence of distance and angle of the placement.

  • 5.
    Ni, Pengpeng
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Isovic, Damir
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Support for Digital VCR functionality over Network for H.264/AVC2008Ingår i: EEE International Conference on Communications 2008, 2008, s. 520-525Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we propose a scalable video coding scheme for H.264/AVC video that fully utilizes the benefits of Switching frames (SP/SI) to facilitate user-friendly remote multimedia stream browsing and editing. A content aware rate-control algorithm is developed to adaptively determine the optimal encoding configuration for balancing the trade-off between video coding efficiency and temporal scalability. Our temporal scalable coding scheme is useful for implementing DVCR-like interactive functionality such as fast-forwarding and reversing in multimedia streaming applications such as Video-On-Demand, video broadcasting and remote video editing.

  • 6.
    Ni, Pengpeng
    et al.
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Isovic, Damir
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Fohler, Gerhard
    University of Kaiserslautern, Kaiserslautern, Germany.
    User-friendly H.264/AVC for Remote Browsing2006Ingår i: Proceedings of the International ACM Multimedia conferance (ACM 06), Santa Barbara, California, USA, 2006, s. 643-646Konferensbidrag (Refereegranskat)
    Abstract [en]

    With the growing popularity of variable network technologies, it is highly desirable to enable effective and quick browsing of remote multimedia content. In this paper we present a method for quick access of remote video content as an initial step towards a full digital Video Cassette Recording functionality in multimedia streaming applications such as Video-On-Demand, video broadcasting and remote video editing.We propose a transcoding scheme for H.264/AVC video that fully utilizes the benefits of recently proposed SP- and SI-frames to facilitate user-friendly remote stream browsing and editing. The transcoding parameters can be adaptively changed and optimized to support different characteristics of H.264 video streams.

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