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3.2.4BT.656DataSampling
3.2.5BT.656FIFOPacking
BT.656VideoCaptureMode
Table3-5.CommonVideoSourceParameters
NumberofActiveLines
VideoSource(Field1/Field2)NumberofActivePixelsFieldRate(Hz)
squarepixel240/24064060
60Hz/525lines
BT.601244/24372060
60Hz/525lines
squarepixel288/28876850
50Hz/625lines
BT.601288/28872050
50Hz/625lines
FortheBT.656videocapturemode,theFIFObufferisdividedintothreesections(threebuffers).One
sectionis1280bytesdeepandisdedicatedforstorageofYdatasamples.Theothertwosectionsare
dedicatedforstorageofCbandCrdatasamples,respectively.ThebuffersforCbandCrsamplesare
each640bytesdeep.TheincomingvideodatastreamisseparatedintoY,Cb,andCrdatastreams,
scaled(ifselected),andtheY,Cb,andCrbuffersarefilled.Eachofthethreebuffershasa
memory-mappedlocationassociatedwithit;YSRC,CBSRC,andCRSRC.TheYSRC,CBSRC,and
CRSRClocationsarereadonlyandareusedbyEDMAstoaccessvideodatasamplesstoredinthe
FIFOs.
Ifvideocaptureisenabled(BLKCAPbitinVCxCTLiscleared),pixelsinthecapturewindowarecaptured
intheY,Cb,andCrbuffers.ThevideocapturemoduleusestheYEVT,CbEVT,andCrEVTeventsto
notifytheEDMAcontrollertocopydatafromthecapturebufferstotheDSPmemory.Thenumberof
doublewordsrequiredtogeneratetheeventsissetbytheVCTHRLDnbitsinVCxTHRLD.Onevery
YEVT,theEDMAshouldmovedatafromtheYbuffertoDSPmemoryusingtheYSRClocationasthe
sourceaddress.OneveryCbEVT,theEDMAshouldmovedatafromtheCbbuffertoDSPmemoryusing
theCBSRClocationasthesourceaddress.OneveryCrEVT,theEDMAshouldmovedatafromtheCr
buffertoDSPmemoryusingtheCRSRClocationasthesourceaddress.Notethattransfersizefromthe
CbandCrbuffersishalfofthetransfersizefromtheYbuffersinceforeveryfourYsamples,thereare
twoCbandtwoCrsamples.
Incomingdata(includingtimingcodes)aresampledandtheHCOUNTcounteradvancedonlyonclock
cyclesforwhichtheCAPENinputisactive.InputswhenCAPENisinactiveareignored.Thetiming
referencecodesarerecognizedonlywhenthreesequentialsampleswithCAPENvalidaretheFFh,00h,
00hsequence.Anon-00hsampleaftertheFFhorafterthefirst00hcausesthetimingreference
recognitionlogictoberesetandtolookforFFhagain.(Unsampleddata;thosewithCAPENinactive;in
themiddleofatimingreferencedonotcausetherecognitionlogictoberesetsincethesearenot
consideredtobevalidinputs.)
Captureddataisalwayspackedinto64-bitsbeforebeingwrittenintothecaptureFIFO(s).Bydefault,data
ispackedintotheFIFOfromrighttoleft.
The8-bitBT.656modeusesthreeFIFOsforcolorseparation.Samplesarepackedintoeachwordas
showninFigure3-2.
SPRUEM1–May2007VideoCapturePort49
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