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Rate-distortion optimized bitstream switching for peer-to-peer live streaming
Jin-feng ZHANG, Rong-gang WANG, Jian-wei NIU, Yuan DONG, Hai-la WANG
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(4): 445-456.
https://doi.org/10.1631/jzus.A071343
Peer-to-peer (P2P) technology provides a cost-effective and scalable way to distribute video data. However, high heterogeneity of the P2P network, which rises not only from heterogeneous link capacity between peers but also from dynamic variation of available bandwidth, brings forward great challenge to video streaming. To attack this problem, an adaptive scheme based on rate-distortion optimization (RDO) is proposed in this paper. While low complexity RDO based frame dropping is exploited to shape bitrate into available bandwidth in peers, the streamed bitstream is dynamically switched among multiple available versions in an RDO way by the streaming server. Simulation results show that the proposed scheme based on RDO achieves great gain in overall perceived quality over simple heuristic schemes.
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Efficient video downscaling transcoder from MPEG-2 to H.264
Xiang-wen WANG, Jun SUN, Rong XIE, Song-yu YU
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(4): 457-463.
https://doi.org/10.1631/jzus.A071585
The new H.264 video coding standard achieves significantly higher compression performance than MPEG-2. As the MPEG-2 is popular in digital TV, DVD, etc., bandwidth or memory space can be saved by transcoding those streams into H.264 in these applications. Unfortunately, the huge complexity keeps transcoding from being widely used in practical applications. This paper proposes an efficient transcoding architecture with a smart downscaling decoder and a fast mode decision algorithm. Using the proposed architecture, huge buffering memory space is saved and the transcoding complexity is reduced. Performance of the proposed fast mode decision algorithm is validated by experiments.
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Trimming self-intersections in swept volume solid modeling
Zhi-qi XU, Xiu-zi YE, Zhi-yang CHEN, Yin ZHANG, San-yuan ZHANG
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(4): 470-480.
https://doi.org/10.1631/jzus.A071357
Swept volume solid modeling has been applied to many areas such as NC machining simulation and verification, robot workspace analysis, collision detection, and CAD. But self-intersections continue to be a challenging problem in the boundary representation of swept volume solids. A novel algorithm is presented in this paper to trim self-intersection regions in swept volume solids modeling. This trimming algorithm consists of two major steps: (1) roughly detecting self-intersection regions by checking intersections or overlapping of the envelop profiles; (2) splitting the whole envelop surfaces of the swept volume solid into separate non-self-intersecting patches to trim global self-intersections, and to trim local self-intersections, dividing local self-intersecting regions into patches and replacing self-intersecting patches with non-self-intersecting ones. Examples show that our algorithm is efficient and robust.
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Flower solid modeling based on sketches
Zhan DING, Shu-chang XU, Xiu-zi YE, Yin ZHANG, San-yuan ZHANG
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(4): 481-488.
https://doi.org/10.1631/jzus.A071443
In this paper we propose a method to model flowers of solid shape. Based on (Ijiri et al., 2005)’s method, we separate individual flower modeling and inflorescence modeling procedures into structure and geometry modeling. We incorporate interactive editing gestures to allow the user to edit structure parameters freely onto structure diagram. Furthermore, we use free-hand sketching techniques to allow users to create and edit 3D geometrical elements freely and easily. The final step is to automatically merge all independent 3D geometrical elements into a single waterproof mesh. Our experiments show that this solid modeling approach is promising. Using our approach, novice users can create vivid flower models easily and freely. The generated flower model is waterproof. It can have applications in visualization, animation, gaming, and toys and decorations if printed out on 3D rapid prototyping devices.
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Stereo vision based SLAM using Rao-Blackwellised particle filter
Er-yong WU, Gong-yan LI, Zhi-yu XIANG, Ji-lin LIU
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(4): 500-509.
https://doi.org/10.1631/jzus.A071361
We present an algorithm which can realize 3D stereo vision simultaneous localization and mapping (SLAM) for mobile robot in unknown outdoor environments, which means the 6-DOF motion and a sparse but persistent map of natural landmarks be constructed online only with a stereo camera. In mobile robotics research, we extend FastSLAM 2.0 like stereo vision SLAM with “pure vision” domain to outdoor environments. Unlike popular stochastic motion model used in conventional monocular vision SLAM, we utilize the ideas of structure from motion (SFM) for initial motion estimation, which is more suitable for the robot moving in large-scale outdoor, and textured environments. SIFT features are used as natural landmarks, and its 3D positions are constructed directly through triangulation. Considering the computational complexity and memory consumption, Bkd-tree and Best-Bin-First (BBF) search strategy are utilized for SIFT feature descriptor matching. Results show high accuracy of our algorithm, even in the circumstance of large translation and large rotation movements.
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A semi-custom design methodology for design performance optimization
Dong-ming LV, Pei-yong ZHANG, Dan-dan ZHENG, Xiao-lang YAN, Bo ZHANG, Li QUAN
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(4): 510-516.
https://doi.org/10.1631/jzus.A071449
We present a semi-custom design methodology based on transistor tuning to optimize the design performance. Compared with other transistor tuning approaches, our tuning process takes the cross-talk effect into account and prominently reduces the complexity for circuit simulation and analysis by decomposing the circuit network utilizing graph theory. Furthermore, the incremental placement and routing for the corresponding transistor tuning in conventional approaches is not required in our methodology, which might induce timing graph variation and additional iterations for design convergence. This methodology combines the flexible automated circuit tuning and physical design tools to provide more opportunities for design optimization throughout the design cycle.
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Input-output approach to robust stability and stabilization for uncertain singular systems with time-varying discrete and distributed delays
Hui-jiao WANG, An-ke XUE, Yun-fei GUO, Ren-quan LU
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2008, 9(4): 546-551.
https://doi.org/10.1631/jzus.A071299
Based on input-output approach, the robust stability and stabilization problems for uncertain singular systems with time-varying delays are investigated. The parameter uncertainties are assumed to be norm-bounded and the time-varying delays include both discrete delay and distributed delay. By introducing a new input-output model, the time-delay system is embedded in a family of systems with a forward system without time delay and a dynamical feedback uncertainty. A sufficient and necessary condition, which guarantees the system regular, impulse-free and stable for all admissible uncertainties, is obtained. Based on the strict linear matrix inequality, the desired robust state feedback controller is also obtained. Finally, a numerical example is provided to demonstrate the application of the proposed method.
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19 articles
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