1、IntroductionCharacteristics of multimedia dataQuality of service managementResource managementStream adaptationCase study: the Tiger video file serverSummaryChapter 15: Distributed Multimedia SystemsDistributed multimedia applicationsNetworked video library, Internet telephony, videoconferenceCharac

2、teristics of multimedia applicationsTimely delivery of streams of multimedia data to end-usersAudio sample, video frameTo meet the timing requirementsQoS( quality of service) Characteristics of distributed multimedia applicationsTraditional real-time systemE.g. avionics, air traffic control, telepho

3、ne switchingSmall quantities of data, strict time requirementQoS management: fixed schedule that ensures worst-case requirements are always metDifferent requirements of multimedia app.General environmentCompete with other distributed app. for network bandwidth, computing resourceDynamic resource req

4、uirements E.g. the number of participants of a video conference may varyUser participant in the control of resource consumptionQoS managementWeb-based multimediaExtensive bufferingBest-effortNetwork phone and audio conferenceRelatively low bandwidthEfficient compression techniquesHigh interactive la

5、tencyVideo-on-demand servicesRequire sufficient dedicated network bandwidthExisting distributed multimedia Apps. without QoSExamplesVideoconference (cooperative)Distributed online ensemble (synchronous)RequirementsLow-latency communicationround trip delays 4The maximum streams the Tiger system can s

6、upport simultaneously T/t * the number of disksDistributed schedule (2)Initial prototype 19945 x cubs: 133MHz Pentium PCs(48M RAM, 2G SCSI disk, Windows NT), ATM network68 simultaneous streams with perfect qualityOne cub failed, the loss rate is 0.02% 14 cubs: each 4 disks, ATM network 1997602 simul

7、taneous streams ( 2Mbps)Loss rate 0.01%; with one cub failed, loss rate 0.04%The designers suggested that Tiger could be scaled to 1000 cubs supporting 30,000 clients.Microsoft NetShow Theater ServerPerformance and scalabilityIntroductionCharacteristics of multimedia dataQuality of service managemen

8、tResource managementStream adaptationCase study: the Tiger video file serverSummaryChapter 15: Distributed Multimedia SystemsCharacteristics of distributed multimedia apps.Large volumes of time-dependent dataQoS managementQoS negotiationBandwidth, latency, loss rateTraffic shapping: bucket leaky alg

9、orithm, token bucket leaky algorithmAdmission controlScheduleFair scheduleReal-time scheduleSummaryStream adaptionScaleFilterThe Tiger video file serversDate layoutStripingMirroringDistributed scheduleslotsSummaryA typical distributed multimedia systemCharacteristics of typical multimedia streamsDat

10、a rate(approximate) Sample or frame frequency sizeTelephone speech64 kbps8 bits8000/secCD-quality sound1.4 Mbps16 bits44,000/secStandard TV video( pressed)120 Mbpsup to 640 x 480pixels x 16 bits24/secStandard TV video (MPEG-1 compressed)1.5 Mbpsvariable24/secHDTV video( pressed)10003000 Mbpsup to 19

11、20 x 1080pixels x 24 bits2460/secHDTV videoMPEG-2 compressed)1030 Mbpsvariable2460/secTypical infrastructure components for multimedia applicationsQoS specifications for components of the application shown in Figure 15.4Component BandwidthLatencyLoss rateResources requiredCameraOut:10 frames/sec, ra

12、w video -640 x480 x16 bitsZero -ACodecIn:Out:10 frames/sec, raw videoMPEG-1 streamInteractiveLow10 ms CPU each 100 ms;10 Mbytes RAMBMixerIn:Out:2 44 kbps audio1 44 kbps audioInteractiveVery low1 ms CPU each 100 ms;1 Mbytes RAMHWindowsystemIn:Out:various50 frame/sec framebufferInteractiveLow5 ms CPU

13、each 100 ms; 5 Mbytes RAMKNetworkconnectionIn/Out:MPEG-1 stream, approx.1.5 MbpsInteractiveLow1.5 Mbps, low-lossstream protocolLNetworkconnectionIn/Out:Audio 44 kbpsInteractiveVery low44 kbps, very low-lossstream protocolThe QoS managers taskTraffic shaping algorithmToken generator(a) Leaky bucket(b) Token bucketThe RFC 1363 flow SpecProtocol versionMaximum transmission unitToken bucket rateToken bucket sizeMaximum transmission rateMinimum delay noticedMaximum delay variationLoss sensitivityBurst loss sensitivityLoss intervalQuality of guaranteeBandwidth:Delay:Loss:FilteringSourceTargetsH