英文论文翻译.docx
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英文论文翻译.docx
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英文论文翻译
LANreal-timevideocommunication
【Abstract】:
Inthispaper,todifferentlocalareanetwork,acommonreal-timevideotransmissionsolutionsisproposed.onbaseofDivxcodecinuse,Madefromcompressed,Framing,senttothereceiver,theideaofextractingtheentireprocessConcreteimplementationofprogramsandVC++toachievethecoresourcecodeaswellasthetransmissioncontrolstrategy.effectivelyensurethehighqualityreal-timevideotransmission.
【keywords】:
Guest;Server;Real-timevideotransmission;Divx
Introduction:
In-housereal-timetransmissionofvideolocalareanetworkhasbeenwidelyused.NowforthevideotransmissionisthemostwiredLANLAN,wiredLANbecausethetechnologyismature,fastspeed,goodstability.However,alargequantityofvideodata,cablenetworkswillalsobejobinsecurity,causedbyblockageofdata,overtimewillcauseseriousdelay;iftheworkingenvironmentisnotfixed,requestmobility,thentheywouldhaveusedawirelessnetwork,wirelessnetworkcardisnowworkwiththechangesintheenvironmentbecomesunstable,sothatvideotransmissionwillleadtoasignificantdeclineinthequality,easilyleadtore-screenvideo,jitter,andsoon.
Inthispaper,adifferentlocalareanetwork,acommonreal-timevideotransmissionsolutions,theuseofVC++sincethepackageofWindowsVFWSDKsoftwaredevelopmentkitforthesecondarydevelopment,throughtheDivxcodec,thetransmissioninaccordancewiththedevelopmentofstrategiestoeffectivelysolutionasaresultofnetworkinstabilitycausedbythepartialvideoimageghosting,jitter,etc.problems.
LANreal-timevideotransmissionproblems:
LANinordertoeffective,high-qualitytransmissionofvideostreamsneedtosupportavarietyoftechnologies,includingvideocompression,encodingtechnology,application-layerqualitycontroltechniquesandsoon.
Networkbandwidthislimited,soitisnecessarytotransmitvideoimagecompression,MPEG-4hasbeenwidelyusedinnetworkenvironmentsinreal-timevideotransmission,becausetheMPEG-4with:
Youcanachieveveryhighcompressionratio;withflexibleencodinganddecodingcomplexity;Object-basedencoding,allowingvideo,audio,interactiveobjects;hasstrongadvantagessuchasfaulttolerance.Inthispaper,Divxcodecforvideoencoding,compression,infact,Divx=(video)MPEG-4+(audio)MP3.
Application-layerqualitycontroltechniquesarenowusedbyRTP/RTCPprotocoltoensurethatthevideostreaminthenetworkwithlowlatency,high-qualitytransmission.RTPdatatransferprotocolisresponsibleforstreamingaudioandvideodataandload,RTCPisresponsiblefortheRTPdatapackettransmissioncontrol.Thisagreementwasadoptedbytheclient(receiver)feedbacknetworkstatus,server-side(sender)toadjusttheinformationcollection,transmissionspeedandcompressionratio.However,forafixedrateofimageacquisition,theneedforsoftwarecompression,decompression,adjustthespeedofacquisitionleadtimecompressionofdatacollecteddirectlydiscarded,
Encodertoadjustthecompressionrationeedstosettheencoderparametersandrestarttheencoder,thecorrespondingdecodertobeadjusted,theprocesswilltakealongtime,notreal-timerequirements.Therefore,thisarticledidnotuseRTP/RTCPprotocol,butstartingfromthesendingend,real-timenetworkconditionstodetermine,using"stop-and-wait"strategyinreal-timetransmission.
TherearetwotypesofnetworkcommunicationsprotocolTCPandUDP,UDPismoresuitablefornetworkvideotransmissionenvironment,butitdoesnotprovideerrordetectionanderrorcorrectionfeatures,assoonasnetworkcongestion,thelargeamountofdatapacketwillbelost.TheDivxcodectechnology,isaframeforthecodecunit,dividedintokeyframesandnon-keyframe.Duringtransmission,duetorelativelyhighcompressionratio,aslongasabitofawrongplace,willhaveanimpactonhundredsofeventhousandsofotherbits,andadirectresultofthefuzzyimage,andsoon.Onlyuntilthenextkeyframecanbetherestorationofthearrivalofaclearimage.Inordertoensuretheaccuracyoftransmission,
Theyneedtodevelopanagreementintheapplicationlayer.Inthisway,UDPadvantagesnolongerexist.Therefore,thisarticlechoosetouseTCPfornetworkcommunications.VFWintegrateduseoftechnology,streamingmediatechnology,supportto"stop,suchas"controlstrategy,thebettersolutionforreal-timevideotransmissionLANeasilyleadtotheghosting,jitterproblem.
Toachievereal-timevideotransmission:
Inordertoachievereal-timevideotransmission,withatotalofatleasttheideaistosendredundantinformation,themaximumextentpossibletosendthelatestvideo.
.LANreal-timevideotransmissionusingtheserver/clientmodel,usingVC++toachieve.ItsworkprocessesasshowninFigure1.
ClientServer
LAN
Figure1Real-timevideotransmissionworkflow
AVICapfromtheuseofvideocapturevideocapturecardtocapturevideoimages,thebitmappatternofthevideoframe,andthenuseDivxencoderforcompression,toachievethroughtheWinsockcompressedvideodatainreal-timenetworktransmission,thereceivingendofthedatadeliveryDivxdecodertoextractthefinalrealizationofvideodisplay.
InVC++,usingVFWtechnology,theclientthroughcapSetCallbackOnFrame()registeracallbackfunction,whenthecollectiontoanimageacquisitioncard,thesystemwillautomaticallycallthecallbackfunction,andthenusethecallbackfunctionICSeqCompressFrame()compressionfunction.AndthenthroughtheWinsockcompresseddatawillbesenttotheserver-side.Server-sideafterreceivinganEndtotheICDecompress()extract,andfinallywithSetDIBitsToDevice()theimagedisplayed.
1.videoframeoftheformation:
Videocapturedataisabitmaptypeofvideoframe,DivxencoderaftercompressiontoformaframeforthestreamMpeg4format.Divxcodecformatalsoextractframes.Therefore,toframeasaunittosendvideodatastream.ThereceivingendinordertobeeasilyextractedfromaproposedformatasshowninFigure2toformtheframe.
beginning
oftheframe
Framesize
framenumber
FrameType
Framedata
Figure2videoframeformat
Completeafieldbyfiveofthemeaningofeachfieldisasfollows:
framethebeginningofsigns,marksthebeginningofonetotakeup4bytesofspace.Maybesetto0xffffffff.Framesizethatthesizeoftheentireframe,includingthesizeoffivefields,occupiedbyfourbytesofspace.Framenumberofsequentiallynumberedframesthattakeup4bytesofspace.Frametype,markwhetherornotthisframeisthekeyframe,occupiedbyabyteofspace.Framedata,storedinacompresseddataintegrity.
2.videoframessent:
Real-timevideotransmissioninordertoreal-time,willbecompressedtokeepgooddatasenttothereceivingend.Therefore,inthesendingendtocreateathread,designedtosenddata.Atthesametimekeepthemainthreadisstillcollectingdataandcompression.Send-threadedworkflowshowninfigure3.。
Yes
No
Figure3workflowstosendthread
MaywishtocreateathreadcalledtheassumptionsendThread,thecorecodeisasfollows:
while
(1)
{
isOK=true;//ready
SuspendThread(sendThread);//Hangthread
isOK=false;//Threadissendingdata
intlength=frameLength;//Datasetlength
if(length<50000){//Datatodeterminewhetherthenormal
intn=0;
intsendCount=0;
while(length>0){
n=send(sock,(char*)imageBuf+sendCount,length,0);//sendmessage
//imageBufisGuidelines,Readytoframe
if(n==SOCKET_ERROR)//Networkabnormal,thenwithdrawfromthethread
break;
length-=n;
sendCount+=n;
}
}
}
Threadtosendthedataframeisbasedonamethodintheformationofagooddataframe.Thisapproachcanguaranteethecurrentframeisbeingsenttoreachthereceiverintact.
Attentiontothebeginningofthisthread,orwhentosendafinished,thethreadtohangon,andwaitfortheoutsideworldtowakeup.Thistaskiscompletedbythecallbackfunctioninthecallbackfunctiontodetermineifthethreadisreadytosend(inahungstate),werecarriedoutinimagecompression,andthenwakeupthethreadaftersendingcompresseddata,ordirectlyoutof,waitforthenextcallthecallbackfunction,thisstrategycalled"stop-and-wait"strategyisdetailedintheback.
3.videoframestoreceive
Thereceivingendthemostimportantthingistoacceptthedatastreamfromtheextractedonecomplete.Methodsofthoughtis:
Firstofall,fromthedatastreamtostartlookingforsignsframe,andthennexttothebackofthedatafromtheextractedframesize,andthenreadfromthereceivebuffertotheremainderoftheframedata.Thenextframeandthenstartlookingforsigns,andsobackandforth.
Thesamereceivertocreateathreaddedicatedtotheimplementationofdatareception.MaywishtoassumethatthethreadcalledrecThread,thecorecodeisasfollows:
while(temp!
=SOCKET_ERROR)
{
if(!
isStart){//ifFramedatawillstart,trueshowsstart
if(endNum>3)//Outstandingrecordofthecurrentreceivedata
endNum=0;
temp=recv(clisock,(char*)(recBuf+endNum),1000,0);//Readdatafromthebufferzone
startPos=serchStr(temp+endNum);//Findaframemarkedthebeginning
if(startPos!
=-1){
isStart=true;
endNum=temp+endNum-startPos-4;
memcpy(imageBuf,recBuf+startPos+4,endNum);//Preservationofdataframe
}
else{
memcpy(recBuf,recBuf+temp+endNum-3,3);//Savethelastthreebytesofdata
endNum=3;
}
}
else{
if(endNum<4){//Closelyfollowthesignstodeterminethebeginningofthedata,ifthatcanno
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