Introduction
Thenetworkvideoserver(DVS,DigitalVideoServer)ismainlyusedforthemultimediaserverofreal-timetransmissionofdigitalaudioandvideothroughEthernet.Theimagesandsoundsaresimultaneouslytransmittedthroughthenetwork.Thevideoservercansmoothlyupgradethevideosurveillancesystemtoanetwork-basedvideosurveillancesystemwhileretainingtheexistinganalogvideosurveillanceequipment.ItisverysuitableforintegrationwiththeexistinganalogCCTV(closed-circuittelevisionsurveillance)system.Thevideoserverbringsbrand-newfeaturestoanalogvideoequipment,andcompletelyeliminatesthesystem'sdependenceonspecialequipmentsuchascoaxialcables,analogmonitors,andDVRs.DVRwillnolongerbeanecessitytorealizetherecordingfunction,becausewiththehelpofthevideoserver,thevideoimagecanberecordedandmanagedbyastandardPCserver.
Wirelessnetworkvideoserver(2photos)
Avideoserverusuallyhas1to4analogvideoinputportsforconnectinganalogcameras,andithas1atthesametimeTheEthernetinterfaceisusedtoconnecttothenetwork.Likeanetworkcamera,itcontainsabuilt-inwebserver,imagecompressionchipandoperatingsystem.Undertheactionofthesecomponents,theanalogvideoinputwillbeconvertedintoadigitalvideosignal,whichcanbetransmittedandstoredthroughacomputernetwork,whichgreatlysimplifiesAccessandmanagementofvideoresources.Inadditiontovideoinput,thevideoservercanalsoachieveothermorefunctionsandtransmitmoreinformationthroughthesamenetworkconnection,including:digitalalarminputandoutput(I/Ointerface,whichcanbeusedtotriggertheservertostartRecordingfunctionandtransmissionofvideo,oractivationofexternalalarmdevices(suchaswarninglightsoropeningthedoor,etc.),audio,serialportlightsforserialdatatransmissionorPTZdevicecontrol.Throughtheimagecache,thevideoservercanalsosendtheimagesbeforeandafterthealarm.Thevideoservercanalsoconnectmorededicatedcameras,suchashigh-sensitivityblackandwhitecameras,miniaturecameras,ormicroscopiccameras,andsoon.
Videoserversareusedinthesurveillancefield.Everyoneknowsverywell,butnotcommonapplications,suchasstreamingmedia.Usethestreamingmediamethod,thatis,setupastreamingmediaservertoestablishaconnectionwiththevideoserver,andallvideoaccesstothevideoserverisforwardedthroughthestreamingmediaforwardingserversoftwaremodule,sothatthevideoserviceofthevideoserveronlyoccupiesonechannel.Thisensuresthatthereisonlyoneconnectionwiththevideoserver,whichimprovesplaybackperformanceandquality.
Concept
Afterrecentyearsofdevelopment,ithasevolvedfromsingle-functionvideotransmissiontoaWIFInetworkwithlocalSDcardstorage,orUSBstorageorIDEharddiskstorage.Thetransmissionchannelhasgraduallydevelopedfromtheoriginalsingle-channelto:single-channelD1,two-channelHD1,four-channelCIFandmulti-channelcompatiblemulti-menuoperationandmanagementintegratedsystem.Amongthem,JiudingGroup'snetworkvideoserverproductisoneofthemoreauthoritativerepresentatives.
Thecommunicationmodeofthenetworkvideoserverhasalsograduallydevelopedfromtheoriginalpurewirednetworkto:wiredandwirelessWIFI(802.11abgcommunicationprotocol)compatible,andthewirelesstransmissiondistancehasalsochangedfromtheoriginaltensofmeters(30-100meters),developedintothecurrenttensofkilometers(30-50kilometers).
Thenetworkvideoserverandtheanalogcameraareconnectedtogethertoformadigitalcamera,alsoknownasanIPcamera,whichisanintermediateproductforthetransitionfromananalogcameratoanIPcamera.Somenetworkvideoservershavestoragefunctions.Suchproductsandharddiskvideorecorders(DVR)withnetworkfunctionsarealreadyverycloseinfunction,andthereisatrendofgradualintegration.
Composition
Networkvideoserverisakindofspecialequipmentthatrealizesaudioandvideodataencodingandnetworktransmissionprocessing.Itconsistsofaudioandvideoencoder,networkinterface,audioandvideointerfaceRS422/RS485Serialinterface,RS232serialinterfaceandothercomponents.
Audioandvideocompressionencoder:Becausetheamountofanalogvideodataisverylarge,afterdigital-to-analogconversion,theamountofdataisalsoverylarge,soitisnecessarytousematurecodingtechnologytoconvertthevideodatatomeettherequirementsofnetworktransmission.Encodingwithhighcompressionratioundertechnicalindicatorstomeettransmissionrequirements.PreviousnetworkvideoserversgenerallyuseencoderssuchasM-JPEG,anduserscannotachievehighercompressionratestosuitvariousnetworkenvironments.Theycanonlyachievegeneralnetworktransmissioneffectsbyreducingtheframerate.VariouscompanieshaveintroducedMPEG4networkvideoserverstobettermeettherequirementsofvideonetworktransmission.
Networkinterface:Asthepreviousnetworkingofanalogproductsmainlyrealizednetworktransmissionthroughtheestablishmentofexpensiveindependentopticalfibers,theEthernetinterfaceofthenetworkvideoservercaneasilyrealizeIPnetworkingandrealizedatatransmission.ThenetworkvideoservermainlyusesprotocolssuchasTCP/IPtorealizethenetworktransmissionofaudioandvideodata,controldata,andstatusdetectioninformation.
Audioandvideointerface:Thenetworkvideoserverhasastandardanalogaudioandvideoinputinterface,whichisconvenientformonitoringthevideosignalofeachchannel.NVS900usesDynamicStreamControltechnologytoensuretwo-wayaudioreal-timetransmission,videoframerateisautomaticallyadjustedaccordingtobandwidth,andautomaticconnectiontechnologyafternetworkinterruption.
RS422/RS485serialinterface:ThenetworkvideoserverisequippedwithRS422/RS485serialcommunicationinterface,whichcanbeconnectedtovariousperipheralssuchaspan-tiltanddomethroughthecommunicationline.
Thenetworksurveillancevideoservercancooperatewiththecomputercentralcontrolsoftwaretorealizethelarge-scalesystemnetworkingscheme.Somemanufacturers'networkvideoserversprovideopenSDKforusersorthird-partymanufacturerstodevelopandbuildnewapplicationmethods.
Features
Withthedevelopmentofnetworktechnologyandthepopularizationofbroadbandnetworks,networkvideosurveillancewillgraduallyencroachonthemarketshareoftraditionalvideosurveillanceequipment.Let’stakealookatthefourmajorvideoservers.Basicfeatures:
Smallmodel
Usuallyusually1-4channelsofanalogvideoinput,notlikeaharddiskvideorecorderwithmorethanadozenchannelsofvideoinput,andwillnotcarryaharddiskrandomly,Puttingthestoragedeviceinthemonitoringcenterismoreconducivetothestorageandprotectionofimagedata,whichsavesalotofspaceandlocation.
Simplicity
Transmittingvideodatatothemonitoringcenterthroughafast-developing,cost-effectivecomputercommunicationnetworkrequiresonlyalow-costCategory5networkcable.IfthevideoserverThereisaWIFImoduleinside,ifthewirelessLANmodeisadopted,theneventhecategory5networkcablesaresaved.
Centralcontrol
Anindustrystandardserverandasetofcontrolmanagementapplicationsoftwarecanruntheentiremonitoringsystem.UsersonlyneedtoopenaclientprogramonacomputerconnectedtotheInternet,EntertheIPaddressofthecorrespondingvideoserverinittoperformcomprehensiveremotemonitoring.Anyauthorizedclientcandirectlyaccessanycamera,andcanalsoaccessthemonitoredimagethroughthecentralserver.
Scalability
Morecamerascanbeeasilyadded,andthecentralservercanbeeasilyupgradedtofasterprocessors,largercapacitydiskdrives,andgreaterbandwidthinthefuture.
Advantages
Convenience
Installationandmaintenance
Somepeoplemaysay,"ThecurrentnetworkbandwidthNotenough,usingopticaltransceiversandopticalfibersforremotetransmission,thequalityandtransmissionspeedofvideoimagesarebetterthannetworktransmission."However,theexpensivecostoflayingopticalfibersandthecomplicatedwiringprojectareunbearableformanycustomersandcontractors.Duetothepopularizationofcomputernetworks,anetworkmonitoringsystemcanbebuiltwherethereisanetwork,andtheinstallationcostisgreatlyreduced.
Easytouse
Networkmonitoringisnotlimitedbytimeandplace,andcanbemonitoredatanytimeondemand.YoucanselectivelywatchtheimagesatthedesignatedlocationinsteadofTheimagesthatneedtobeviewedarenottransmitted,whichsavesnetworkbandwidthresources.
Intelligence
Alargeamountofinformationcanbeextractedfromthevideostreaminatimelyandautomaticmanner.Thisinformationcanbetransmitted,saved,retrieved,storedindifferentplaces,andstoredinmultiplemachines;Itisprogrammedtotransmitimagesonlywhencertaineventsoccur.
Smallattenuation
Adoptingadvanceddigitalcompressiontechnology,digitalsignalattenuationissmallduringtransmission,andthequalityisguaranteed.Theanalogvideosignalistransmittedoveralongdistance,thesignalwillbeattenuated,andvideoamplifiercompensationneedstobeconfigured.
Stableandreliable
Thenetworkvideoserverusesanembeddedoperatingsystem,andthehardwareuseshigh-performancechips,whichmakesitstable.
Wirelesstransmission
Usinganetworkvideoservertoconvertthevideosignalofthecameraintoadigitalsignal,inthecaseofinconvenienttrafficanddifficultwiring,thedigitalvideosignalItissenttothemonitoringcenter,andthenpublishedbythemonitoringcentertotheInternetforviewingbytheremotemanagementdepartment.Theadvantagesofwirelesslocalareanetworkareconvenientnetworking,shortcycle,lowinvestment,andflexiblestructure.
Difference
TheDVRmentionedherereferstotheDVRproductthathasexpandedthenetworkfunctiononthebasisofthetraditionalDVR,sothatmoreuserscanaccessit,preciselybecauseThisproductdevelopmentconceptmakesDVRproductswithnetworkfunctionsstilltraditionalDVRs,anditsmainfunctionisstillstorage,whichalsodeterminesitsmarketpositioninginasmall-scalenetworkenvironmentwithlimitedmonitoringpoints..Themainfunctionsofthenetworkcameraandvideoserverfocusonnetworktransmission.Thenetworkmentionedhereisabigconcept.Thedesignoftheproductispositionedtoadapttodifferentnetworkenvironments,suchasLAN,WAN,INTERNETorWirelessnetwork,etc.,anddoesnotlimitthenumberofmonitoringpoints,doesnotlimitthenumberofuseraccess,etc.
Fromtheperspectiveofproductapplications,networkcamerasandvideoserversfocusonremotemonitoring,suchasroadtraffic,unattendedsubstations,oilfieldproductionmanagement,andtelecommunicationsroomSurveillanceandotherfields,thesurveillancepointsintheseareasarescattered,anditisdifficulttowireatalongdistance.Ifyouwanttobuildabrand-newsystem,youcandirectlychoosenetworkcamera,ifthesystemhasatraditionalsurveillancefrontend,youcanUsingvideoserverasaneffectivesupplement;ifthemonitoringrangeisinasmallareaandremotemonitoringisnotrequired,itwillbemorepracticaltouseDVR.
SomenetworkproductmanufacturersbelievethatDVRisjustatransitionalproduct.Ifthenetworkenvironmentismorematureandthepriceofnetworkproductsisadjustedinthefuture,installasetofsoftwareontheback-endcomputeratwillRemotemonitoringcanberealized,whichwillreplacecurrentproducts.However,somepeopleinthesecurityindustrysaidthattheapplicationscopeofthesethreeproductsisdifferent,andeachhasitsownlivingspace.Especiallyinthesecurityindustry,datasecurityistheprimarygoal,sothestoragefunctionofDVRisstillveryimportant..
Withtheadventoftheinformationage,peoplehaveputforwardhigherrequirementsfornetworkapplications.NetworkcamerasandvideoserverscanberemotelymonitoredthroughtheInternetinanycorneroftheworld.,Eliminatingthecomplicatednetworkconfigurationandwiringwork,greatlyreducingtheengineeringcost,andplayinganimportantroleinthelong-distancecentralizedmonitoringenvironment.AlthoughnetworkcamerasandvideoserversarerepresentativeproductsoftheInternetera,theyarestillintheprocessofcontinuousdevelopmentandimprovement.Withthecontinuousimprovementofnetworkresources,theproductwillfurtherdevelopitspotential.
Wirelessnetwork
Withthedevelopmentandextensionof3Gtechnology,the3Gmobilecommunicationwirelesssystemhasgonefromconceptualoperation,tosmall-scalepiloting,andthentothecurrentofficialcommercialuse.Inthelongprocess,thethreemajoroperatorshaveplannedinadvanceservicesbasedon3Ghigh-speedwirelessaccessfeatures,andvideosurveillanceapplicationsbasedon3Gwirelessnetworkswillbethecorepillar.
Themobility,highbandwidthandothercharacteristicsof3Gtechnologymakethetraditionalsecuritymonitoringmethodshaveadeeperintegrationapplication.Everyoneknowsthatthetechnologicaldevelopmentofsecuritymonitoringis:fromthefirstgenerationofanalogmonitoring,tothesecondgenerationofdigitalmonitoring,andthentothethirdgenerationofnetworkmonitoring.Now,drivenby3G,networkedmonitoringhaschangedfromwiredmonitoring.Therapiddevelopmentofwireless,itshouldbesaidthatthe3Gmobilesurveillancebusinesshasgreatlyexpandedthecommercialmarketspaceofthesurveillanceindustry.
Differenttypesof3Gwirelessnetworkvideoserverscanbedividedintotwocategories.Oneisthebuilt-in3Gfunctionnetworkvideoserver,suchas3Gnetworkvideoserver,3Gnetworkcameraandotherequipment,whichwillcollectthevideoAfterthesignalisencoded,itistransmittedthroughthe3Gnetwork,andisnolongerrestrictedbygeographiclocation,siteenvironment,lineresources,etc.;theothertypeisthescalable3Gwirelessnetworkvideoserver,whichismainlyinsertedintothenetworkvideoserverthroughthe3Gwirelessnetworkcard.Theextended3GfunctionrealizedontheUSBinterface.Taketheapplicationdiagramofthe3GvideoserverproductofDatangNews'ssingle-channelnetworkvideoserverasanexample.Itcanbeclearlyseenhowhisapplicationis:
Application
Withthecontinuousimprovementofvideocompressiontechnologyandthedevelopmentofcomputertechnology,videoservershavebeenwidelyusedinTVbroadcastsystems.Thefullapplicationofvideoserversinmulti-channelbroadcastsystemshasmadeitaTVstationbroadcastThemostimportantpartofthesystem,thisproductcangreatlyimprovetheefficiencyofTVbroadcast.Infact,thevideoserveralsohasmanyadvantagesthattraditionalvideosurveillanceequipmentdoesnothave,andmanynovelapplicationscanbedeveloped.(Non-monitoringfield)
1.Thecompositionofthevideoserver
Thenetworkvideoserverisaspecialcomputerthatcompresses,stores,andprocessesvideoandaudiodata.Itconsistsofavideoandaudiocompressionencoder.,Massstorageequipment,input/outputchannels,networkinterface,audioandvideointerface,RS422serialinterface,protocolinterface,softwareinterface,audioandvideocross-pointmatrix,etc.,whileprovidingexternalphaselockandvideoprocessingfunctions.
Videoandaudiocompressionencoder:Afterthevideoisdigitized,theamountofdataisverylarge,soitisnecessarytousematurecompressiontechnologytocompressthevideodatawithahighcompressionratioundertheconditionofmeetingtherequirementsoftechnicalindicators.Storageandtransmissionrequirements.VideoserversgenerallyusecompressionencoderssuchasH.264orMPEG-4.Userscanchoosecompressionrateandcompressionstructureaccordingtoactualconditionstosuitvariousbroadcastoccasions,savingharddiskspaceandincreasingprogramstorage.,Andcanguaranteethepurposeofbroadcastingquality.
Massstoragedevice:Thevideoserveruseshigh-speed,broadbandSCSIinterfaceharddiskorthemostadvancedFCinterfaceharddiskasthestoragemediumofvideoandaudiomaterials.Atthesametime,theharddiskexpansionofvideoandaudiodataisalsomoreflexible.
Input/outputchannel:Thevideoserverisequippedwithamulti-channelinput/outputsystem,whichenablesmulti-channelinputandplaybacktobecarriedoutatthesametime,realizingmulti-tasking.
Networkinterface:Thevideoserverisequippedwithanetworkinterfacetofacilitatenetworkingandrealizedatasharing.Generally,videoservershaveFCandEthernetinterfaces.FCopticalfibernetworkusesIPprotocolasafast,real-timecopyingandmovingmaterialexchangenetworkbetweenvideoservers,andEthernetisusedtotransmitcontroldataandstatusdetectioninformation.
Videoandaudiointerface:Thevideoserverisequippedwithastandardvideoandaudiointerfaceandananalogmonitoringvideointerfacetofacilitatemonitoringofthevideosignalofeachchannel.Theinput/outputsignalcanbeselectedamonganalog,componentandSDI.
RS422serialinterface:ThevideoserverisequippedwithmultipleRS422serialcommunicationinterfaces,andeachinterfacecanbecontrolledbyanexternalcomputerthroughtheRS422communicationlinetorealizerecordingandplayback.
Protocolinterface:Inadditiontoprovidingvariouscontrolhardwareinterfaces,thevideoserveralsoprovidesprotocolinterfaces.Forexample,theRS422interfacenotonlysupportstheRS422Profileprotocol,butalsosupportsLouth,Odetics,BVWandotherprotocolscontrolledbyRS422.
Softwareinterface:Thevideoserverprovidesanopensoftwareinterfaceforusersorthird-partymanufacturerstodevelopandbuildnewapplications.
Videoandaudiocross-pointmatrix:Thevideoserverhasavideoandaudiocross-pointmatrix,whichallowsflexiblevideoandaudiochannelscheduling,whileensuringthatthetechnicalindicatorsarenotdamaged.
Inaddition,thevideoserverprovidesexternalphaselockandvideoprocessingfunctionstofacilitatetheconstructionofprofessionalvideoandaudiosystems.
3.Thecharacteristicsofvideoserver
Networkvideoserverhasmanycharacteristicsthattraditionalequipmentdoesnothave.Thespecificperformanceisasfollows:
(1)Multi-channel,Recordingandplaybackandotherfunctionsareintegrated,thetraditionalequipmentwithmultipleinputandmultipleoutputfeaturesisthevideoandaudioswitchingmatrix,andtherecordingandplaybackfunctionisthevideorecorder,itgoeswithoutsayingthatthevideoservercanbeusedinthesystemInsteadofseveralvideorecordersandasmallswitchingmatrix.
(2)Videoserverusesharddiskastherecordingmedium,whichhasnon-linearcharacteristics,soithasalltheadvantagesofnon-linearequipment,suchasconvenientmaterialsearch;materialcanbesharedbymultipleoutputchannels;itcanbeadjustedsimultaneouslyorsuccessivelyPlayout.
(3)Whenthematerialisrecordedontheharddiskandhasnotformedacompletefile,itcanbecalledupandplayedbytheoutputchannel,whichisverysuitableforfieldssuchasdelayedbroadcastandvideoondemand.
(4)Thevideoserveriseasytoachieveforwardorbackwardvariablespeedplayback.Toachievethis,traditionalvideorecordersmustgothroughexpensivespecialequipment.
Four.ApplicationofvideoserverintheTVfield
Becausethenetworkvideoserverhastheaboveadvantages,itwillcreatemanynovelapplicationmethodstomeettheneedsofTVmediaandcanGreatlyimproveproductivityandreduceequipmentmaintenanceandlaborcosts.TheapplicationofvideoserverintheTVfieldmainlyhastwoaspects:oneistousethevideoservertobuildanautomaticbroadcastsystem;theotheristousethevideoservertorealizevideoondemand.
1.Usevideoservertobuildanautomaticbroadcastsystem
Inthepast,thebroadcastsystemusedtapeasthemainmedium.However,withthecontinuousimprovementofvideocompressiontechnologyandthedevelopmentofcomputertechnology,thevideoserverisusedinthebroadcastsystem.IthasbecomepossibleandhasbeenusedinmanydomesticTVstations.Ithasbecomeinevitabletochooseavideoserverasasignalsourcewhensettingupabroadcastingsystemtoday.Theharddiskbroadcastsystemwithvideoserverasthemainbody,fullyutilizestheadvantagesofharddiskstorage,avoidstheimpactofthefailureofvideorecordersandotherequipmentonthebroadcast,givesfullplaytotheadvantagesofmulti-channelresourcesharing,andeasilyrealizesbetweenprogramsThecontrolandmanagementbetweentheserialprogrammingandvariousinterruptedbroadcastsandtimingbroadcasts.Theprogramsarestoredintheharddiskintheformofcompressedfiles,whichcanbesavedwithoutframeloss.Allprogramsareuploadedfromtheproductionandeditingports,whichsimplifiesTheworkflowfromproductiontobroadcastisconducivetoimprovingworkefficiency.
Intheharddiskbroadcastsystem,theprogrammaterialisstoredandbroadcastedindigitalcompression.ThesystemcanadoptMPEG-2orM-JPEGcompressionformat.
TheharddiskbroadcastsystemcanadopttheRAIDharddiskstorageoflocalstorageandmirroringbackupmode.RAID-1isalsocalled"mirroring",whichusesadouble-diskfullcopymethodtoprotectdata,avoidingdatalossandsysteminterruptioncausedbyharddiskfailure,andits100%redundancycanachieverapiddatarecovery.Eachvideoserverusesanindependentstorageharddisk,thatis,localstorage,andthevideoserversdonotinterferewitheachotheratall,andthenusefullmirrorbackup,whichhashighsystemreliability.
Theharddiskbroadcastsystemcanadoptadual-networkstructurecombiningFCandEthernet,usingFCtotransmitvideoandaudiosignals,andEthernettotransmitcontrolsignals.
Theharddiskbroadcastsystemiscomposedofvideoandaudioserver,databaseserver,collectionworkstation,previewworkstation,broadcastworkstationandothersubsystems.Twovideoandaudioserversarebackedup.Theserversareinterconnectedbyopticalfibernetworks.Thevideoandaudiomaterialsonthemainserverarecopiedtotheauxiliaryserverthroughtheopticalfibernetwork.Asetofautomaticbroadcastcontrolsystemcontrolsthebroadcastworkstationsoftwosetsofvideoandaudioserversforsimultaneousbroadcast.Thissystemisveryreliable.Atthesametime,thesystemsetsdifferentsecuritylevelsaccordingtodifferentusers,sothatirrelevantpersonnelcannotenterthesystem;iteffectivelyguaranteesthesecurityofsystemdata.Atthesametime,whenthesystemisbroadcast,itautomaticallylocksvariousotherillegaloperationsandsendsoutalarmsignalsintime.
Thespecificapplicationmethodsoftheharddiskautomaticbroadcastsystemwithvideoserverasthemainbodyareasfollows:
(1)Automaticadvertisementbroadcast
VideoserverFirstofall,itisusedtorebroadcastadvertisementswithalargenumberoftimesandashortperiodoftime.Inthisapplicationmethod,thevideoserverisaspecialequipmentforadvertisementbroadcasting,whichiscontrolledbytheautomaticcontrolsoftwareofthebroadcastingsystem.Thebroadcastingundertakenbythevideoservercanonlybecarriedoutonebyoneinorder.Theadvertisementeditingcomputerisresponsibleforthecontrol,thearrangementandcontrolofthesequenceoftheadvertisementbroadcastaretakencareofbytheadvertisementbroadcastcomputer,andthestartandendoftheadvertisementbroadcastarecontrolledbytheautomaticbroadcastcontrolcomputer.Thisapplicationmethoddoesnotrequiremajorchangestotheexistingbroadcastsystem.Theoriginalautomaticbroadcastcontrolsystemandsoftwarecancontinuetobeused.Thevideoserverisequivalenttomultiplevideorecordershere(dependingonthenumberofinputchannelsofthevideoserver).)Andmultiplevideoplayers(dependingonthenumberofoutputchannelsofthevideoserver).Therefore,theoriginalautomaticbroadcastcontrolsystemsoftwarecancontrolthevideoserverforadvertisingbroadcastjustlikecontrollingavideorecorder.
(2)Multi-channelautomaticbroadcastsystem
Usingthemulti-channelcharacteristicsofthevideoservertoestablishacyclicpadbroadcastsystemforthebroadcastroomofmultiplechannelstoshare.Inthisapplicationmethod,thepadbroadcastmaterialofeachchannelisfirstrecordedintothevideoserverthroughtheVTR.Thebroadcastroomofeachchanneloccupiesanoutputchannelofthevideoserver,andeachmaterialonthevideoservercanbebroadcastedseparately.Inthisapplicationmode,apairofvideoserverswithidenticalconfigurationscanbeusedtoestablishabroadcastsystem.Themainandbackupvideoserverseachuseacorrespondingoutputchannelasabackupchannelforeachother.Themainandbackupvideoserversareinterconnectedbyopticalfibernetwork(FC)torealizethesharing,movementandcopyingofvideoandaudiomaterialstoensurethatthemain,Thematerialofthebackupvideoserverisexactlythesame.Asetofautomaticbroadcastcontrolsystemcontrolsthebroadcastworkstationsoftwosetsofvideoserversforsimultaneousbroadcast.
(3)DelayedTVprogrambroadcastsystem
UsingavideoservertoestablishaTVprogramdelayedbroadcastsystemusesthecharacteristicsofthevideoserver,thatis,whenthematerialiswrittentotheharddisk,Withoutcompletelyformingamaterialfile,itcanbesharedandcalled,sothattheharddiskbroadcastsystemhasthefunctionofso-calledrecordandbroadcast(onlyafteraslightdelaycanbebroadcast).Thisschemeismoresuitableforbroadcastingimportantliveprograms.Recordthelivebroadcastintotheharddiskfirst,anddelaythelivebroadcasttimetotheappropriatetimeasneeded.Theprogramdirectorandattendantusethistimetocutandreplacetheunsuitablelivebroadcastonthebroadcastrateadjustmentcontrolcomputer.Suitableforthematerial,orataspeedthatisdifficultforhumaneyestodistinguish,suchasfastorslowplaybackat0.8to1.2times,inordertomaintainthecorrespondingamountofdelay.Thisblind-eyemethodbasedonadvancedtechnologycancontrolthebroadcastofimpropermaterial,whilethelivebroadcasteffectisnotaffectedinanyway.
Therearemanyspecificapplicationmethodsfortheharddiskautomaticbroadcastsystemusingthevideoserver.Iwillnotlistthemhere.Comparedwithtraditionalvideotapebroadcast,thesignalandmaterialoftheharddiskautomaticbroadcastsystemarenotStoredinthecassette,ithastheadvantagesofzero-framepre-rolling,non-linearretrieval,repeateduseofmaterials,andresourcesharing.Thespecificadvantagesare:improvedworkefficiency,bettersecurity,sharingofinformationresources,andadvancementofthesystem.
2.Usevideoservertorealizevideoondemand
Therearetwowaysofvideoondemand:quasivideoondemand(NVOD)andvideoondemand(VOD)
(1)quasivideoondemand(NVOD)
ThevideoserveristhecoreequipmentforrealizingNVODplayback.Withitsmulti-channelcharacteristicsandmaterialsharingcharacteristics,aprogramcanbereplayedafteraperiodoftime,andviewerscanwaitfortheshortesttimetowatchthemselvesOn-demandprograms.Forexample:Inthevideoserver,aprogramwithatimelengthofNisoutputthrough8outputchannels,thesecondchannelisdelayedbyN/8timerelativetothefirstchannel,andthethirdchannelisdelayedrelativetothesecondchannel.PlayatN/8time,andsoon.Theprogramofeachchannelisplayedcyclically,thenthenexttimethefirstchannelstartstoplayisalsodelayedbyN/8timetoplayontheeighthchannel.Inthisway,adjacentchannelsareplayingthesameprogram,butthetimeintervalisN/8.Whentheuserorders,aftertheprogramrequestingcomputerprocessestheorderinformation,theprogramplayingcontrolcomputerwillreturnthechannelnumber,authorizationandotherinformationtobeplayedimmediatelytotheuserreceivingdevice,andtheuserwillbeabletoseewhathehasorderedwithinN/8time.programme.
(2)VideoonDemand(VOD)
Videoserverscanbeusednotonlyforquasi-videoondemandsystems,butalsoforvideoondemand(VOD)systems.ThefullnameofVODisVideoOnDemand,whichisvideo-on-demandtechnology,alsoknownasinteractiveTV-on-demandsystem,whichmeanstoplaythevideostreamasneeded."Watchtheprogramyouwanttowatchwhenyouwanttowatchit",userscanchoosetowatchTVprogramsaccordingtotheirownwishes,whichfundamentallychangesthedeficienciesofpassiveTVwatchinginthepast,andfullyrealizestheinitiativeofuserstoobtaininformation.VODcanalsorealizeotherfunctionssuchasInternet,sendingandreceivinge-mail,homeshopping,travelguide,bookingreservation,stocktradingandsoon.Therefore,itcanbesaidthattheemergenceofthistechnologyallowsuserstoarrangeworkandentertainmenttimeaccordingtotheirownneeds,andtrulyrealizesthatuserscanmastertheinitiativeofviewing,whichgreatlyimprovesandimprovespeople'squalityoflifeandworkefficiency.
TheVODsystemiscomposedofthreeparts:afront-endsystem,anetworksystem,andaclientsystem.Thefront-endsystemisgenerallycomposedofavideoserver,variousfilemanagementservers,andequipmentthatcontrolsthenetworkpart.Variousfileserversmainlycompletesomeuserinformationmanagementandbillingwork,aswellasthemanagementworkandsecurityandconfidentialityoffilmandtelevisionmaterials.Thecontrolnetworkpartmainlycompletesvariousinformationtransmissionworkinvariousserversandtheexchangeofbackgroundfilmandtelevisionmaterialsanddata.Thevideoserverismainlycomposedofastoragesystemandvariouscontrollermanagementsystemsbuiltonit.Itsgoalistorealizethestorageofcompressedmediadataandtheretrievalandtransmissionofmediainformationonrequest.Videoserversaresignificantlydifferentfromtraditionaldataserversinmanyaspects,andmanyproblemsneedtobesolvedtosupportvariousnewfunctions.Atthesametime,itshigh-speeddatatransmissioncapabilitiesensurethatusershavenearlyinstantaccesstoalargenumberoffilms,videoprograms,games,businessinformationandotherservices.Itsbiggestfeatureisthatmultiplepeoplecanwatchthesameprogramfromdifferentstartingpoints,therebyavoidingtheexclusiveuseofasingleuser.
Thescaleofthiskindofapplicationisrelativelylarge,andmultiplemulti-channelvideoserversmustbeformedintoabroadbandnetworkthatcansharelarge-capacityharddiskstorageandcanhandletransportstreams,soastomeetthevariousdemandsofmanyusersforprograms.need.Useron-demandinformationcanbetransmittedtotheon-demandacceptanceserverintwoways:oneistotransmitittotheon-demandacceptanceserverthroughthecity'scableTVHFCnetworkuplinkchannel;theotheristoselectprogramsontheInternetthroughageneral-purposebrowser.Transmittheon-demandinformationtotheon-demandacceptanceserver.Theon-demandacceptanceserverprocessestherelevantinformationandtransmitsittotheplaybackcontrolcomputer,whichcontrolstheplaybackoftheprogramorderedbytheuser,andtransmitsittotheuserterminalthroughtheHFCdownstreamchannel.Therearetwoformsofuserreception:oneisordinaryTV+set-topbox,andtheotheriscomputer+receivingcard,whichcanbewatchedwiththehelpofacomputermonitor.
Themulti-channeldigitalbroadcastsystembasedonthevideoserverhasmanyadvantagesunmatchedbythetraditionalanalogbroadcastsystembasedonthevideotaperecorder.Thevideoserveradoptsanopensoftwareandhardwareplatformandstandardorgeneralinterfaceprotocols.Thesystemhasstrongexpansioncapabilityandcanbeconnectedwiththefutureprogramproduction,editingandbroadcastingsystemofall-digital,disk-based,networked,andmulti-channelresourcesharingmode.Themulti-channeldigitalbroadcastingsystembasedonvideoserverbasedondisk-basedordisk-to-tapecombinationcanrealizebroadcastingerrorisolationandfaultisolation,andcanalsorealizedelayedbroadcasting.ItisthebestsolutionforthetransitionofTVprogrambroadcastingfromanalogtodigital.Fromalong-termperspective,VODhasahugepotentialmarketandfar-reachingdevelopmentprospects,becausefromadeeplevel,VODisnotonlyaproblemofvideo-on-demand,itrepresentstheapplicationoffull-featurednetworkinganddigitalinteractiveinformationinthefuture.Thedevelopmenttrendisadeeperlevelofinteractionintermsofcontentandform.Itisalsothebasisfornewapplicationssuchasdigitalcinema,interactivevideonews,andadvertising.Ithasbroaddevelopmentpotential.VODisanimportantpartofthefutureinformationhighwayarchitecture.Itisthesoulofbroadbandservicesinfutureinformationservices.Therefore,itiscertainthatwiththecontinuousdevelopmentofdigitaltechnology,multimediatechnologyandcomputertechnology,theapplicationofvideoserversintheTVfieldwillhavemoreextensions.
Prospects
Inthefuturemarket,IPCamerawillseerapidgrowth,anditsgrowthwillleadtoadeclineintheanalogcameramarket,sothattheDVSmarketwillgraduallydeclineastheanalogcameradeclines.Judgingfromthecurrenttechnology,thecostofIPCamerahasbeenlowerthanthatofanalogcamera+DVS,andIPCamerahasshownmorepowerfulvitality.
BecauseofthelowbarrierstoentryforDVS,variousmanufacturersareunwillingtopromotestandardizationinordertoprotecttheirowninterests,andthescaleoftheindustryhasalwaysbeensubjecttostandardizationissues.ThedevelopmentofIPCamerashowedatrendofstandardizationfromtheverybeginning,andDVSgraduallyrealizedstandardizationunderthedriveofIPCamera.
TheDVSmarketmayincreaseinacertainamountduetotheexpansionofthesecuritymarketinthefuture,butinthefuture,themarketshareofDVSwillbeaffectedastheanalogcameramarketdeclines.Fortunately,althoughtheanalogcameramarketwillgraduallydecline,thenumberofinstalledanalogcamerasisstaggering,coveringawiderangeoffieldsandindustries.Therefore,asanintermediatedevicebetweenthetraditionalandthe"fourmodernizations",DVSwillmaintainaconsiderablegrowthperiod.