Shanwei Cen

Bio: Shanwei Cen is an academic researcher from Oregon Health & Science University. The author has contributed to research in topics: The Internet & Video server. The author has an hindex of 6, co-authored 8 publications receiving 545 citations.

A Distributed Real-Time MPEG Video Audio Player

Abstract: This paper presents the design, implementation and experimental analysis of a distributed, real-time MPEG video and audio player. The player is designed for use across the Internet, a shared environment with variable traffic and with great diversity in network bandwidth and host processing speed. We use a novel toolkit approach to build software feedback mechanisms for client/server synchronization, dynamic Quality-of-Service control, and system adaptiveness. Our experimental results show that the feedback mechanisms are effective, and that the player performs very well in the Internet environment.

Flow and Congestion Control for Internet Media Streaming Applications

Abstract: This paper proposes a new flow and congestion control scheme, SCP (Streaming Control Protocol), for real-time streaming of continuous multimedia data across the Internet. The design of SCP arose from our long-time experience in building and using an adaptive real-time streaming video player. The proposed scheme is designed to allow SCP-based streaming traffic to live in harmony with each other, and with TCP-based traffic. At the same time, it improves smoothness in streaming, and ensures low, predictable latency and effective use of network bandwidth. SCP also incorporates mobility awareness and supports limited data rates and possible pauses in streaming. In this paper, we present a description and analysis of SCP, and an evaluation of it through Internet-based experiments.

Player for adaptive MPEG video streaming over the Internet

Abstract: This paper describes the design and implementation of a real-time, streaming, Internet video and audio player. The player has a number of advanced features including dynamic adaptation to changes in available bandwidth, latency and latency variation; a multi-dimensional media scaling capability driven by user-specified quality of service (QoS) requirements; and support for complex content comprising multiple synchronized video and audio streams. The player was developed as part of the QUASAR project at Oregon Graduate Institute, is freely available, and serves as a testbed for research in adaptive resource management and QoS control.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

System support for mobile multimedia applications

Abstract: The emergence of free streaming media players, coupled with the availability of powerful inexpensive laptop computers has created a domain for mobile multimedia applications. Mobile multimedia applications must deal with the inherent variability generated when migrating from office to conference room, den to patio, or classroom to dorm room. This paper presents a multi-layered multimedia architecture utilizing adaptive layers and cross-layer notifications. An implementation of that architecture is demonstrated using a streaming media player that communicates with a video server while switching from wired LAN to POTS to wireless LAN, transparently adapting to new network addresses and bandwidth fluctuations. Mobility is supported by using device indications to force the adaptive feedback system into an "exploratory" mode and signal the application to re-establish the control and data channels.

Adaptive methods for distributed video presentation

Abstract: This paper describes problems and solutions for delivering real-time, multi-media presentations across the Internet. A key characteristic of presentations of continuous media datatypes, such as digital video and audio, is their need for predictable real-time data delivery. For example, an NTSC quality video presentation requires video frames to be displayed every 1/30th of a second. Variations in this display rate can be observable as stalls or glitches in the video stream and reduce the quality of the presentation [6]. Delivering such presentations across the Internet is di cult because highly variable bandwidth and latency make it di cult to predict the arrival time of network packets containing video or audio data. Our solution is for distributed multi-media systems to adapt dynamically to these changing network conditions. This paper describes the use of software feedback to make multimedia presentations adaptive, and shows how video can be played across an unpredictable network such as the Internet without bene t of resource reservations. The Internet's unpredictable latency and bandwidth characteristics arise because di erent links in the network have performance that varies by several orders of magnitude. Hence, the location of a video client relative to its video server in uences the performance characteristics of the connection. Furthermore, even if the capability of the hardware in question can be established, the available bandwidth varies wildly from moment to moment because the Internet is a shared resource: just a few concurrent large data transfers can easily take up most of a connection's bandwidth. In this environment, adaptive methods are essential to maintaining video quality.

An application-specific protocol architecture for wireless microsensor networks

Abstract: Networking together hundreds or thousands of cheap microsensor nodes allows users to accurately monitor a remote environment by intelligently combining the data from the individual nodes. These networks require robust wireless communication protocols that are energy efficient and provide low latency. We develop and analyze low-energy adaptive clustering hierarchy (LEACH), a protocol architecture for microsensor networks that combines the ideas of energy-efficient cluster-based routing and media access together with application-specific data aggregation to achieve good performance in terms of system lifetime, latency, and application-perceived quality. LEACH includes a new, distributed cluster formation technique that enables self-organization of large numbers of nodes, algorithms for adapting clusters and rotating cluster head positions to evenly distribute the energy load among all the nodes, and techniques to enable distributed signal processing to save communication resources. Our results show that LEACH can improve system lifetime by an order of magnitude compared with general-purpose multihop approaches.

Error control and concealment for video communication: a review

Abstract: The problem of error control and concealment in video communication is becoming increasingly important because of the growing interest in video delivery over unreliable channels such as wireless networks and the Internet. This paper reviews the techniques that have been developed for error control and concealment. These techniques are described in three categories according to the roles that the encoder and decoder play in the underlying approaches. Forward error concealment includes methods that add redundancy at the source end to enhance error resilience of the coded bit streams. Error concealment by postprocessing refers to operations at the decoder to recover the damaged areas based on characteristics of image and video signals. Last, interactive error concealment covers techniques that are dependent on a dialogue between the source and destination. Both current research activities and practice in international standards are covered.

Client-server based interactive television program guide system with remote server recording

Abstract: An interactive television program guide system is provided. An interactive television program guide provides users with an opportunity to select programs for recording on a remote media server. Programs may also be recorded on a local media server. The program guide provides users with VCR-like control over programs that are played back from the media servers and over real-time cached copies of the programs. The program guide also provides users with an opportunity to designate gift recipients for whom programs may be recorded.

Application-specific protocol architectures for wireless networks

Abstract: In recent years, advances in energy-efficient design and wireless technologies have enabled exciting new applications for wireless devices. These applications span a wide range, including real-time and streaming video and audio delivery, remote monitoring using networked microsensors, personal medical monitoring, and home networking of everyday appliances. While these applications require high performance from the network, they suffer from resource constraints that do not appear in more traditional wired computing environments. In particular, wireless spectrum is scarce, often limiting the bandwidth available to applications and making the channel error-prone, and the nodes are battery-operated, often limiting available energy. My thesis is that this harsh environment with severe resource constraints requires an application-specific protocol architecture, rather than the traditional layered approach, to obtain the best possible performance. This dissertation supports this claim using detailed case studies on microsensor networks and wireless video delivery. The first study develops LEACH (Low-Energy Adaptive Clustering Hierarchy), an architecture for remote microsensor networks that combines the ideas of energy-efficient cluster-based routing and media access together with application-specific data aggregation to achieve good performance in terms of system lifetime, latency, and application-perceived quality. This approach improves system lifetime by an order of magnitude compared to general-purpose approaches when the node energy is limited. The second study develops an unequal error protection scheme for MPEG-4 compressed video delivery that adapts the level of protection applied to portions of a packet to the degree of importance of the corresponding bits. This approach obtains better application-perceived performance than current approaches for the same amount of transmission bandwidth. These two systems show that application-specific protocol architectures achieve the energy and latency efficiency and error robustness needed for wireless networks. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)