利用FPGA实现广播视频基础设施

外文翻译姓名：翁新武学号：201003052专业：信号与信息处理BroadcastVideoInfrastructure

ImplementationUsingFPGAsIntroductionTheproliferationofhigh-definitiontelevision(HDTV)videocontentcreationandthemethodofdeliveringthesecontentsinabandwidth-limitedbroadcastchannelenvironmenthavedrivennewvideocompressionstandardsandassociatedvideoimageprocessingapplications.Traditionally,onlycableandsatelliteoperatorsprovidedvideodelivery.Nowtelecommunicationcompanies(telcos)aregettingintothisarenabyusingthelatestvideocoder/decoders(CODECs)andvideo-processingtechnologytotransmitdigitalvideototheconsumerviaInternetprotocoltelevision(IPTV).VideoandImageProcessingTrendsManynewandexcitinginnovations,suchasHDTVanddigitalcinema,revolvearoundvideoandimageprocessing,andtheevolutionofthistechnologyisrapid.Leapsforwardinimagecaptureanddisplayresolutions,advancedcompressiontechniques,and利用FPGA实现广播视频基础设施引言新兴的高清电视（HDTV）的视频创作和在有限带宽的无线信道环境下的传输方法，推动了新的视频压缩标准和相关视频图像处理技术。在以往只有有线和卫星运营商提供视频传输。现在电信公司（telcos）是进入这个领域并使用最新的视频编码器/解码器（CODECs）和视频处理技术，再通过互联网协议电视（IPTV）来传输数字视频的给消费者。视频和图像处理许多新的和振奋人心的创新，如高清晰度电视和数字电影，以及围绕视频和图像处理这项技术的迅速发展。图像采集和显示分辨率,及先进的数据压缩技术的迅速发展，视频处理videointelligencearethedrivingforcesbehindthisinnovation.Resolutionsinbroadcastequipmenthaveincreasedsignificantlyoverthelastfewyears,asshowninTable1.Table1.ResolutionbyBroadcastEndEquipmentEndEquipmentResolutionHDTV1920x1080pixelsDigitalCinema4096x1714pixelsAdvancedcompressiontechniquesarereplacingprevious-generationtechnology,offeringenhancementslikebetterstreamingcapability,highercompressionforagivenquality,andlowerlatency.JPEG2000isalsogainingmomentuminstorageanddigitalcinema.Evenasthesenewcompressionsolutionsaredeployed,standardscommitteescontinuetoenhanceH.264andJPEG2000standards.Inthelast10years,thedigitaltelevisionbroadcastindustryhasbeenwellservedbytheMPEG-2standardforstandard-definitiontelevision(SDTV).H.264-AVC(MPEG4-Part10)andtheMicrosoftversion,VC1,willeventuallyreplaceMPEG-2asavideo-encodingmethodforbothSDTVandHDTV.Broadcastequipmentmanufacturersmustprovide智能化是这种创新的动力。在过去的几年中，解决广播终端设备的方案已大大增加，如表1所示。表1.解决广播终端设备的方案EndEquipmentResolutionHDTV1920x1080pixelsDigitalCinema4096x1714pixels先进的压缩技术取代了老的技术，并提供了更强的性能，像更快的数据率，更高的压缩率，和更快的处理速度。JPEG2000是在图像存储和数字影院方面也是有很大优势。即使这些新的压缩技术已经被采纳，标准委员会仍然在为增强H.264和JPEG2000的标准而努力。在过去的10年里，数字电视广播业采用MPEG-2标准的标准清晰度电视(SDTV)已经很好了。H.264-AVC(MPEG4-Part10)和微软的VC1版本，最终将取代MPEG-2,并作为标准清晰度和高清晰度电视的一种编码方法。广播设备制造商必须提供各种编码标准，variousencodingstandardsinordertosatisfycurrentandfutureneeds.InadditiontothevariouscorevideoCODECstandards,therearealsodifferenttypesofvideopre-andpostprocessingalgorithmsusedtoenhancetheoverallpicturequalityfortheconsumer.Withexpandingresolutionsandevolvingcompression,thereisaneedforhighperformancewhilekeepingarchitecturesflexibletoallowforquickupgradeability.Inaddition,asatechnologymaturesanditsvolumesincrease,therewillbeadesiretoreducecosts.Byprovidingsolutionsfortheseneeds,programmablelogicdevices(PLDs)playanimportantrolefortheemergingdigitalvideobroadcastinfrastructure.VideoContentCreationThefirststageofthevideobroadcastchainistheprofessionaldigitalvideocamerathatcapturesthevideoandaudiocontents.ThevideocaneitherbeSDorHD.ThisdigitalcamerawilltypicallyhaveaSocietyofMotionPictureandTelevisionEngineers(SMPTE)-definedserialdatainterface(SDI)output.SDIisanuncompressedvideostreamrunningat以满足当前和未来需求。除了各种核心的视频编解码标准，也有不同类型的视频前和后处理算法用于提高整体画面质量以满足消费者。在视频处理的解决方法不断改善和压缩技术不断改进时，我们在兼顾系统高性能的同时也要保持系统结构灵活并能方便快速升级。此外，在一个技术的成熟和提高的同时也希望能够降低成本。为解决这些需求，可编程逻辑器件(PLDs)将在新兴的数字视频广播基础设施中发挥着重要的作用。视频内容创作视频广播制作流程的第一阶段是用专业数字视频摄像机捕捉的视频和音频内容。视频可以是标清或者是高清的。数字相机要有一个电影和电视工程师协会(SMPTE)定义的串行数据接口(SDI)的输出接口。SDI的输出一个未压缩的视频数据，工作在270Mbps(SD),1.485Gbps(HD),或2.97Gbps(1080pHD)o270Mbps(SD),1.485Gbps(HD),or2.97Gbps(1080pHD).Altera'sStratix®IIGXFPGAs,withtheirintegratedserializer/deserializer(SERDES)andclock/datarecovery(CDR),processthevideostreamontotheSDIoutputofthecamera.VideoPre-andPostprocessingTheNTSCstandardfortelevisiontransmission,usedbybroadcastersinNorthAmerica,hasafixed6-MHzbandwidthperchannel.(The8-MHzPALstandardisusedinEuropeandotherpartsoftheworld.)Thisbandwidthlimitationwassetlongbeforedigitaltelevisionemerged.Thisanalogbandwidthlimitationdictatedthecurrentdigitaltelevision(DTV)transmissionspecification.Digitalvideoqualityissuperiortotheclassicalanalogvideo.Thehigherthedigitalresolution,thehigherthebandwidththatisrequiredtoconveyortransmitthevideodata.Deliveringgoodqualityvideoalmostinvariablyrequirespreprocessingthesourcevideo.Limitingtheavailablebandwidthinthedigitaldomainwithvariousvideocompressionswilldecodedstream.PushingthevideocompressorhardAltera7sStratix®IIGXFPGAs,通过串/并行综合器(SERDES)和时钟/数据恢复模块(CDR)来处理摄像机SDI接口输出的视频数据。视频预先处理和后加工在北美地区的电视广播公司使用NTSC制式电视信号标准，这种制式电视信号的每一个通道的带宽为6MHzo(8MHz带宽的PAL制式电视信号标准一般在欧洲和世界其他一些地区使用。)这种带宽限制的设置要早于数字电视出现。这种模拟带宽的限制决定了当前数字电视(DTV)传输规范。数字视频质量优于传统的模拟视频信号。这就要求在传递或传送视频数据时需要更多数据量和更宽带宽。高质量的视频几乎总是需要预先对源视频进行处理。各种视频压缩由于限制了可用带宽，所以在展开解码的数据流时会表现在不同的方式。过度的视频压缩将会带来块噪声或块假manifestindifferentwayswhendisplayingthewillproduceblocknoiseorblockingartifacts,duetotheDCToftheblock-basedCODEC.Videopre-andpostprocessingmakesiteasierfortheencodertocompressthevideo,aswellasfurtherenablingittoimprovepicturequalityandreducedeliverybandwidthrequirements.Thiscapabilityisofcriticalimportanceforcable,satellite,telcos,andIPTVbroadcastbusinessmodelswheremeetinghighqualitydemandsmustbeachievedwithinnarrowbandwidthconstraints.Thepreprocessingmayinvolveusing2Dfilteringtosmoothoutsomeofthehigh-frequencycontentbeforeitenterstheencodertoreducetheamountofblocknoise.Altera'sVideoandImageProcessingSuiteincludes2Dfiniteimpulseresponse(FIR)andmedianfilterfunctions.Theyprovideaflexibleandefficientmeanstoperform2DFIRfilteringoperationsusingmatricesof3x3,5x5,or7x7constantcoefficients.Therefore,pre-andpostprocessingarekeydifferentiatorsforanytypeofvideocompressiontohavethebestperformanceinabandwidth-limitedenvironment.象,这是由于块编解码器的离散余弦变换导致的。视频预先处理和后加工使得编码器压缩视频更易于实现，以及进一步使它能够提高图像质量和降低传送带宽要求。这种能力是至关重要的，尤其是在电缆、卫星、电信运营商和网络电视广播业务模式下，满足高质量的要求，必须实现在窄带宽的限制。预处理一般使用2D滤波器滤除部分进入编码器之前的高频内容以减少块状噪声。Alterazs的视频和图像处理套件包括二维的有限脉冲响应（FIR）和中值滤波功能，并提供了一个灵活的和有效的方式进行二维傅里叶滤波运算，使用3x3、5x5、或7x7的矩阵作为系数。因此，视频的预处理和后加工是使任何类型的视频压缩在窄带宽下有最佳的性能的关键。VideoCompressionThenextstagesetsthecourseforcompressingthepreprocessedrawvideodatabeforetransmittingtotheenduser.TherearevariousgenerationsofcompressionstandardsrangingfromMPEG1toMPEG4,withfourmethodsforcompression:discretecosinetransform(DCT),vectorquantization(VQ),fractalcompression,anddiscretewavelettransform(DWT).Table2summarizesthevariousMPEGstandardsTable2.CompressionStandardsStandardDataRateApplicationsMPEG-1<1.5MbpsVCDforCD-ROM,Level3isthemostpopularforMP3audioMPEG-21.5Mbpsto15MbpsDTVforcablesatelliteandterrestrialbroadcastMPEG-40.5Mbpsto40MbpsVideoconferencing,surveillance,andbroadcastingwithPart10forH.264MPEG-2isthedominantstandardforDTVacrosstheworld,withdigitalcable,satellite,andterrestrialbroadcastersstillusingthisstandard.AsthebroadcastindustrytrendstowardmoreHDcontent,thegiventransmissionbandwidthisunderevermorepressuretomakeitfitinthepredefinedanalogbandwidthspectrum.AsIPTVstartstorolloutonthetraditionaltelcowiringsystems,MPEG-2definitelywillnotbeeconomicalorfeasibleforcarryingvideoprogramstoconsumers.视频压缩第二阶段的主要任务是在视频信号传输到终端用户之前，压缩预处理的原始视频数据。这里有各种样式的压缩标准，从MPEG1到MPEG4有四种压缩方法：离散余弦变换（DCT）,矢量量化（VQ）,分形压缩，离散小波变换（DWT）o表2总结了各种标准表2•压缩标准StandardDataRateApplicationsMPEG-1<1.5MbpsVCDforCD-ROM,Level3isthemostpopularforMP3audioMPEG-21.5Mbpsto15MbpsDTVforcablesatelliteandterrestrialbroadcastMPEG-40.5Mbpsto40MbpsVideoconferencing,surveillance,andbroadcastingwithPart10forH.264MPEG-2是世界各地数字电视的主要标准，在数字有线电视、卫星和地面广播的电视中仍然使用这一标准。随着电视广播行业趋向于更高清内容，这种给定的传输带宽的传输压力越来越大，使得它只适用于预先确定的模拟带宽频谱。由于网络电视（IPTV）的不建立在传统电信布线系统上，所以，对于消费者来说MPEG-2压缩已不再是电视节目的经济或可选方式。ITU-T的视频编码专家组（VCEG）,TheITU-TVideoCodingExpertsGroup(VCEG),togetherwiththeISO/IECMovingPictureExpertsGroup(MPEG),introducedtheMPEG4-Part10(alsocalledH.264)standard.Capableofprovidinggoodvideoqualityatbitratessubstantiallylowerthanpreviousstandards,H.264doessowithoutsomuchofanincreaseincomplexityastomakethedesignimpractical(excessivelyexpensive)toimplement.Anadditionalgoalwastoallowthestandardtobeflexibleenoughtobeappliedtoaverywidevarietyofapplications(bothlowandhighbitrates,aswellaslow-andhigh-resolutionvideo)andtoworkwellonaverywidevarietyofnetworksandsystems.ByusingtheStratixIIFPGA,Altera'sintellectualpropertypartnerATEMEhasintroducedtheIndustry，sfirstsingle-chipSDH.264mainprofileencoderforthebroadcastindustry(Figure1).加上ISO/IEC的运动图像专家组（MPEG）,介绍了MPEG4-Part10（也叫H.264）标准。能够提供良好的视频画质并且比特率大大低于以往的标准，H.264并没有做太多使设计不切实际（非常昂贵）的措施来增加了系统的复杂性。另外一个目标是允许这个标准有足够的灵活性，来得到更非常广泛的应用（在低/高比特率，以及在低/高分辨率视频）及能在各种网络和系统中很好运行。StratixIIFPGA是由Altera7s的知识产权核（IP）与ATEME公司合作推出的业界第一款为广播业服务的单片SDH.264编码器（图1）。

Figure1.StratixIISingle-ChipH.264EncoderBlockDiagramTherearealsoothercompressionstandardssuchasJPEG2000,whichusestatetechniquesbasedonwavelettechnology.Thearchitectureshouldlenditselffromportabledigitalcameras,videostorage,andadvancedmedicalimaging.

图1。StratixII单片H.264编码器框图也有其他压缩标准像运用基于小波技术的JPEG2000等。这种结构的压缩标准应适用于便携式数码相机，视频存储，和先进的医疗成像。VideoDistributionThecompressedvideocanberoutedanddistributedwithinthebroadcaststudiofacilitybyusingtheASIstandardforshortdistancerouting.TheindustrytrendistouseavideooverIPnetworktodistributevideodataoverlongdistances.AlteraoffersavideooverIPreferencedesignthatdemonstratesthetransmissionofMPEG-2transportstream(TS)dataoverIP-basednetworks.ThereferencedesignbridgesoneormorecompressedvideostreamsandIPpacketswith100Mbpsor1GbpsEthernet.TheASIencodeanddecodereferencedesignisalsoavailable.Adigitalvideobroadcastasynchronousserialinterface(DVB-ASI)isaserialdatatransmissionprotocolthattransportsMPEG-2packetsovercopper-basedcablesoropticalnetworks.VideoScalingandDe-InterlacingProductionstudioandhead-endequipmentcanusuallyperformvideoscalingandde-interlacingforapplicationssuchasSDtoHDconversionorviceversa.Otherapplicationsincludefiltersforedgedetectionprocessing,verticalmotionfilter,andinterfieldmotionfilter.视频分发传送压缩的视频信号通过使用一种ASI标准的短距离路由来把视频信号分发传送给演播室设备。但行业趋势是通过IP网络长距离分发视频数据来使用视频信号oAltera提出了一种基于IP网络（TS）传输方式来传输MPEG-2数据码流的IP核参考设计。这种参考设计为一个或多个压缩视频流和数据包与100Mbps或lGbps以太网搭建了连接桥。ASI的编码和解码也可同样参考这种设计方式。数字视频广播的异步串行接口（DVB-ASI）是一种通过同轴电缆或光纤网络传输MPEG-2数据包的串行数据传输协议。视频缩放和去隔行影视工作室和前端设备通常可以进行视频缩放和交错等应用，像从标清到高清转换或高清到标清的转换。其他应用包括像边缘检测滤波器，垂直运动和场间运动滤波器。OneofthecommonrequirementsformanyprofessionalstudiosistheabilitytousesingleormultipledisplaydevicestoshowavarietyofnormalSDTVorHDTVsignals.Theabilitytoeasilycontroltheswitchingbetweenthesevarioussourcesviaaremotecontrolisessentialincreatinganprofessional,easy-to-usesystem.Thereforevideoscalingandde-interlacingisessentialforthevideoswitcher/routerthatiscapableofhandlingthedifferenttypeofvideoresolutionforvideoswitching,routing,andlocaldisplays,suchastheoneshowninFigure2.Figure2.StudioMonitorsToOtherVideoSinksToOtherVideoSinks许多专业工作室有一个共同的要求就是能够使用单个或多个显示设备显示各种标清电视或高清晰度电视信号。能够很容易地远程控制来切换各种视频信号源是必不可少的专业技术的指标，使系统易于使用。因此，视频缩放和交错是视频切换器/路由器必不可少的部分，并且能够处理不同类型分辨率的视频信号的视频转换、路由和本地显示，如图2所示。图2。演播室监视器ToOtherVideoSinksVideoMonitor1图2。演播室监视器ToOtherVideoSinksVideoMonitor1VideoMonitorsColorSpaceConversionandVideoFormatsSincetherearemanyvideoformatsthatbroadcastersmustworkwith,dependingonwherethefinalendusersarelocated,thebroadcaststudiomustbeabletoconvertbetweendifferentcolorspacesandvideoformats.Colorisdescribedusingdifferentcolorspacedomains,witheachspacedomainassociatedtovariousapplicationsbasedonsystemrequirements.Colorinformationisdeterminedbytwoseparatechrominancesignals,CbandCr,whichareafunctionofathirdsignal,Y,thebrightnessorluminancesignal.TheRGBcolorspaceisalsodefinedbythreecomponents,red,green,andblue.Colorspaceconversionisoftennecessarywhentransferringdatabetweendevicesthatusedifferentcolorspacemodels.Forexample,totransferatelevisionimagetoacomputermonitor,youmayneedtoconverttheimagefromtheYCbCrcolorspacetotheRGBcolorspace.Conversely,transferringanimagefromacomputerdisplaytoatelevisionsetmayrequireatrans