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Signal Processing Magazine, IEEE

Issue 4 • Date July 2000

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Displaying Results 1 - 5 of 5
  • Multimedia communications over networks [guest editor]

    Page(s): 9
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    Freely Available from IEEE
  • Error resilient video coding techniques

    Page(s): 61 - 82
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    We review error resilience techniques for real-time video transport over unreliable networks. Topics covered include an introduction to today's protocol and network environments and their characteristics, encoder error resilience tools, decoder error concealment techniques, as well as techniques that require cooperation between encoder, decoder, and the network. We provide a review of general principles of these techniques as well as specific implementations adopted by the H.263 and MPEG-4 video coding standards. The majority of the article is devoted to the techniques developed for block-based hybrid coders using motion-compensated prediction and transform coding. A separate section covers error resilience techniques for shape coding in MPEG-4 View full abstract»

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  • IP-networked multimedia conferencing

    Page(s): 31 - 43
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    This article looks at video conferencing, specifically the VideoTalks system developed by AT&T Labs. This system was designed to alleviate some of the problems of both user experience and audiovisual signal quality. It allows talks and presentations generated in one auditorium or conference room to be received in other conference rooms, multicast to desktop computers, and received at home or on the road. VideoTalks is a prototypical system that can be retrofitted to provide for a variety of Internet services, such as remote learning, narrowcasting to niche audiences, video telephone, video conferencing, low cost video-on-demand, etc. An effort was also made to make the system function without a full-time operator View full abstract»

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  • Channel-adaptive wideband wireless video telephony

    Page(s): 10 - 30
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    The fundamental advantage of burst-by-burst (BbB) adaptive intelligent multimode multimedia transceivers (IMMTs) is that-irrespective of the propagation environment encountered-when the mobile roams across different environments subject to path loss; shadow- and fast-fading; co-channel-, intersymbol-, and multiuser interference, while experiencing power control errors, the system will always be able to configure itself in the highest possible throughput mode, while maintaining the required transmission integrity. Finding a specific solution to a distributive or interactive video communications problem has to be based on a compromise in terms of the inherently contradictory constraints of video quality, bit rate, delay, robustness against channel errors, and the associated implementational complexity. Considering some of these tradeoffs and proposing a range of attractive solutions to various video communications problems is the basic aim of this overview. The article portrays a range of proprietary video codecs and compares them to some of the existing standard video codecs. A number of multimode video transceivers are also characterized. Systems employing the standard H.263 video codec in the context of wideband BbB adaptive video transceivers are examined, and the concept of BbB-adaptive video transceivers is then extended to CDMA-based systems View full abstract»

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  • Multimedia services over digital subscriber lines

    Page(s): 44 - 60
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    We study the problem of reliable and yet efficient multimedia communications over asymmetric digital subscriber line (ADSL) through joint consideration of compression/coding and channel transmission techniques. The transmission of digital multimedia data requires the existing systems to be augmented with functions that can handle not only ordinary (nonmultimedia) data. In addition, the high volume of multimedia data can be handled efficiently only if all available system resources are carefully optimized. We consider the special characteristics of ADSL channels to formulate optimization criteria. We present a system where the encoder consists of a layer coder that divides and compresses the source data into coded layers of multimedia data with different performance and quality-of-service requirements. The encoded bit streams are then transmitted over a noisy channel, where channel noise may distort the data. The decoder removes all the coding and compression applied in the encoder to obtain as close as possible the original data. It is conceivable that for such a system the loss of information occurs not only during the source compression but also in the channel transmission. The source coding scheme and bit stream arrangement have a direct impact on the channel distortion. Therefore, the joint consideration of source/channel coding design is ideal to reduce the overall information loss View full abstract»

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Aims & Scope

IEEE Signal Processing Magazine publishes tutorial-style articles on signal processing research and applications, as well as columns and forums on issues of interest.

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Meet Our Editors

Editor-in-Chief
Min Wu
University of Maryland, College Park
United States 

http://www/ece.umd.edu/~minwu/