ISSN:1124-318X    

DOI:10.1002/ett.4460120302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2001

数据来源: WILEY

摘要:

AbstractDespite much research in the field of mobile multimedia, delivery of real—time—interactive video over noisy wireless channels remains a challenging problem. Two of the major issues in providing true end—to—end mobile multimedia capability are interoperability between platforms and networks and the poor performance of video compression algorithms in error—prone environments. This paper presents a method for prioritising data partitioned MPEG—4 video in a way suitable for transmission over a mobile network. The effectiveness of the technique is demonstrated by examining the performance when transmitted using the Real—Time Transport protocol over GPRS (General Packet Radio Service) data channels under varying chann

ISSN:1124-318X    

DOI:10.1002/ett.4460120303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2001

数据来源: WILEY

摘要:

AbstractThe MPEG—2 standard, describes several options to split the video stream in sub—streams conveying information at different detail level. This fact can be exploited to generate a low quality stream with all what is necessary for a basic service while all other sub—streams carry “detail” information to improve the quality of the reconstructed signal. In a mixed network environment this can be exploited to allow the stream to be decoded by different terminals. Another use is to provide flexibility in tough transmission systems where either traffic or noise can give rise to severe impairments. In this paper signal—to—noise—ratio scalability is used in a radio transmission system targeted as the DVB—S (Digital Video Broadcasting — Satellite) to investigate the eventual gains. It is shown that for a given target rate, differentiated coding allows the received signal to be decoded at a channel Signal to Noise Ratio which is 3 dB lower than the one necessary for a single—

ISSN:1124-318X    

DOI:10.1002/ett.4460120304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2001

数据来源: WILEY

摘要:

AbstractAutomatic Repeat Request (ARQ) strategies reduce error propagation in low bitrate video transmission. However, retransmission of corrupted data introduces delay which may be critical in some practical applications. In such cases, only a FEC strategy is feasible at the expense of a significant increase of the overall transmission bit rate. In this paper, a strategy is proposed which instead of protecting the whole H. 263 video stream, uses all the redundancy to protect the most important parts of the bit stream, i. e. GOB start codes. More specifically, the 22—bit—long start code used in the H. 263 standard is replaced with longer Gold sequences which ensure a higher protection against noise. A different sequence is used for each GOB so that additional information can be obtained which can be used to improve the quality of the decoded sequence. The new technique is derived by assuming a slow—fading channel such as those encountered in pedestrian applications. Simulation results prove the effectiveness of the proposed technique with respect to classical FEC schemes in terms of PSNR and overall bit

ISSN:1124-318X    

DOI:10.1002/ett.4460120305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2001

数据来源: WILEY

摘要:

AbstractA new Rate—Distortion (R—D) optimized image sequence encoding scheme is introduced, fully compatible with the standard MPEG—2 decoder. R—D optimal DCT coefficient thresholding is used, so that best image reproduction quality is achieved under the constraint of a “local” target bit rate for every image. The proposed technique combines R—D optimal coefficient thresholding and some elements of the MPEG—2 rate control model “Test Model 5” and results in a new video encoding scheme, which offers in most cases a higher representation quality than “Test Model 5”. The performance of the proposed technique is experimentally evaluated for the coding of standa

ISSN:1124-318X    

DOI:10.1002/ett.4460120306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2001

数据来源: WILEY

摘要:

AbstractIn this paper, the problem of DCT information loss in the transmission of coded pictures over unreliable packet networks is studied. Due to the use of variable length coding, packet losses can make impossible the reconstruction of large areas, causing annoying artifacts in the decoded image. Here, different methods of error concealment directly working in the transformed domain are described and their performance are compared with reference to the results of an extensive testing phase. Our analysis spans from very simple interpolation algorithms, which require only minor computational resources, even if at expense of a limited reconstruction quality, to more complex techniques, based on the use of Artificial Neural Networks, which yield good results even in very detailed areas, but require longer computational time.

ISSN:1124-318X    

DOI:10.1002/ett.4460120307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2001

数据来源: WILEY

摘要:

AbstractThis paper presents a new network layer traffic control protocol for rapid layer adaptation and prompt congestion recovery of a layered—video multicast session. The proposed protocol SMART, which stands for Scalable Multimedia Rapid Rate Control in Multicast Networks, defines a concept of dependency between multicast group addresses that are pertaining to the same layered—video session. The information on dependency is carried on an extended version of Internet Group Managenemt Protocol, which is called IGMP—DX (Dependency Extension). SMART router creates a database to manage the dependency information. With SMART, receivers can adapt their subscription level to the right level rapidly by the function of Fast Learning. Emergency Drop Request is sent by a host who detects intensive congestion, and the router blocks the associated traffic. In this manner network can recover from congestion rapidly while not impairing the minimal multicast service. SMART supports both IGMPv2 and IGMPv3, including sourcespecific multicast in Internet. It is shown by simulations that SMART provides a rapid rate control mechanism and good scalability with small amount of control s

ISSN:1124-318X    

DOI:10.1002/ett.4460120308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2001

数据来源: WILEY

摘要:

AbstractA dynamic quality of service (QoS) mapping control scheme, which includes feedforward and feedback QoS control, is proposed for the differentiated services (DiffServ) networks in this work. To achieve reliable and consistent end—to—end video streaming with relative service differentiation, the proposed solution consists of two parts: (1) relative priority—based indexing and categorization of streaming video content at the sending end—system and (2) dynamic and aggregate QoS mapping control with packet, session, and class—based granularity level for categorized packets at the edge of the DiffServ domain, called the video gateway (VG), based upon the load variation of the network. In particular, we focus on dynamic solutions to handle QoS demand variations of continuous media applications (e. g. varying priorities from aggregated/categorized packets) and QoS supply variations of the DiffServ network (e. g. varying loss/delay due to fluctuating network loads). Thus, with the proposed dynamic QoS mapping control, video streaming with enhanced quality is demonstrated under a pric

ISSN:1124-318X    

DOI:10.1002/ett.4460120309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2001

数据来源: WILEY

摘要:

AbstractUntil the present, the digital television (DTV) industry has focused providing high—quality basic video and audio services. With advancements in the underlying technologies, digital television is likely to evolve into a much more interactive medium, involving advanced data services and applications which are both integrated with and synchronized to the video/audio content of the broadcast. We present our approach for the implementation of these synchronized data services, with emphasis on the issues of content synchronization and the optimization of data placement in the broadcast strea

ISSN:1124-318X    

DOI:10.1002/ett.4460120310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2001

数据来源: WILEY

摘要:

AbstractA multimedia conferencing system, dubbed AT&T VideoTalks™, has been designed and constructed at AT&T Labs—Research. It allows presentations generated in one conference room to be received in other conference rooms and at desktop computers. Real—time interaction is provided between the conference rooms. Desktop viewers can submit audio or text based questions. Interconnection is accomplished entirely via the corporate IP intranet. Multimedia presentations, including audio, video and graphics, are also digitally recorded for later re—multicasts or on—demand viewing using indexes based on viewgraphs. Network congestion is prevented by restricting the total number of presentations and playbacks. VideoTalks is a prototype system that can be retrofitted to provide for a variety of Internet services, such as remote learning, narrowcasting to niche audiences, video telephony, video conferencing, low cost video—on

ISSN:1124-318X    

DOI:10.1002/ett.4460120311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2001

数据来源: WILEY