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a
Luma (Y)
sample
-
Chroma (Cb/Cr)
samples
-
b c d ed c b n - 1 n n - 1 n - 2 n - 3n - 4 n - 3 n - 2
a b c d eSAV n - 1 n EAVn - 4 n - 3 n - 2
Leading edge replicated pixels
Trailing edge replicated pixels
Active line
a
Luma (Y)
sample
-
Chroma (Cb/Cr)
samples
-
b c d ea-4 a-3 a-1 n-1 n n+1 n+2 n+3n-4 n-3 n-2
a-2 a-1 a b cSAV n-1 n EAVn-4 n-3 n-2
Leading edge replicated pixels
Trailing edge replicated pixels
Active line
a-4 a-3 d e n+4n+1 n+2 n+3
XSIZE
XSTART
3.6AncillaryDataCapture
AncillaryDataCapture
NotethatedgepixelreplicationonlycomesintoeffectwhenthefullBT.656streamisbeingcaptured.If
VCXSTARTisgreaterthan0,thenonlysomeoftheleadingedgereplicatedpixelsareusedbythefilter.If
VCXSTARTisgreaterthanm,thennoneoftheleadingedgereplicatedpixelsareused.Similarly,if
VCXSTOPislessthanthenumberofsamplesbeforeEAV,thennoneoronlysomeofthetrailingedge
replicatedpixelsareusedbythefilters.
Figure3-11.EdgePixelReplication
Figure3-12showsanexampleofacapturewindowthatissmallerthantheBT.656activeline.Samplea
isthefirstsampleinthehorizontalcapturewindowandsamplenisthelastsample.Inthiscase,any
filteringdoneonthefirstsamplelocationusesthemleadingedgecapturedpixels(mis3inthisexample),
andanyfilteringdoneonthelastsamplelocationusesthemtrailingcapturedpixels.(Froman
implementationstandpoint,themirroringandfilteringcanstillbeginandendwithSAVandEAV,butthe
samplesbeforeVCXSTARTorafterVCXSTOPmustnotbesavedtotheYCbCrbuffers.)
Figure3-12.CaptureWindowNotRequiringEdgePixelReplication
TheBT.656andsomeY/Cspecificationsincludesprovisionforcarryingancillary(non-video)datawithin
thehorizontalandverticalblankingregions.Horizontalancillary(HANC)dataappearsbetweentheEAV
codeandSAVcodes.Verticalancillary(VANC)data,alsocalledverticalblankinginterval(VBI)data,
appearsduringtheactivehorizontallineportionofverticallyblanking(forexample,afteranSAVwith
V=1).Ancillarydatablocksarealwaysprecededbyanancillarydataheader00h,FFh,FFh.
60VideoCapturePortSPRUEM1–May2007
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