Filter
Top Products
www.ti.com
4.4.2ChrominanceRe-samplingOperation
YCbCr 4:2:2 interspersed
source pixels
YCbCr 4:2:2 co-sited
output results
Luma (Y)
sample
Cb’
f
= (-3Cb
ab
+ 33Cb
cd
+ 101Cb
ef
- 3Cb
gh
) / 128
Cr’
f
= (-3Cr
ab
+ 33Cr
cd
+ 101Cr
ef
- 3Cr
gh
) / 128
Chroma (Cb/Cr)
samples
-
a b c d e f g h i j k l
-
4.4.3ScalingOperation
2× upscaled output
YCbCr 4:2:2 co-sited
source pixels
Luma (Y)
sample
Y’
d’
= (-1Y
c
+ 17Y
d
+ 17Y
e
- 1Y
f
) / 32
Cb’
d
= (-1Cb
a
+ 17Cb
c
+ 17Cb
e
- 1Cb
g
) / 32
Cr’
d
= (-1Cr
a
+ 17Cr
c
+ 17Cr
e
- 1Cr
g
) / 32
-
Chroma (Cb/Cr)
samples
-
a a’ b b’ c c’ d d’ e e’ f f’
a b c d e f g
g
Cr’
c
= Cr
c
Cb’
c
= Cb
c
Y’
b
= Y
b
VideoOutputFiltering
Chrominancere-samplingcomputeschrominancevaluesatsamplepointscorrespondingtooutput
luminancesamplesbasedontheinputinterspersedchrominancesamples.Thisfilterperformsthe
conversionbetweeninterspersedYCbCr4:2:2formatandco-sitedYCbCr4:2:2format.Thevertical
portionoftheconversionfromYCbCr4:2:0tointerspersedYCbCr4:2:2mustbeperformedinsoftware.
Thechrominancere-samplingfilterscalculatetheimpliedvalueofCbandCrco-sitedwithluminance
samplepointsbaseduponnearbyinterspersedCbandCrsamples.Theresultingvaluesareclampedto
between01handFEhbeforebeingoutput.Chrominancere-samplingisshowninFigure4-15.
Figure4-15.ChrominanceRe-sampling
The2x-scalingmodeisusedtodoublethehorizontalresolutionofoutputluminanceandchrominance
data.ThisallowsprocessedCIFresolutionimagestobeoutputatfullsize.Verticalscalingmustbe
performedinsoftware.Scalingforco-sitedsourceisshowninFigure4-16andscalingforinterspersed
sourceisshowninFigure4-17.
Foraco-sitedsource,thesourceluminancepixelsareoutputunchangedforeveryevenpixel(a,b,c,
etc.,inFigure4-16).Oddluminancepixels(a',b',c',etc.)aregeneratedfromneighboringsource(even)
pixelsusingafourtapfilter.Thechrominancesourcepixelsareoutputunchangedforeveryothereven
pixel(a,c,e,etc.).Otherevenoutputpixel(b,d,f,etc.)chrominancevaluesaregeneratedfrom
neighboringsourcechrominancepixelsusingafourtapfilter.
Foraninterspersedsource,theluminanceisoutputidenticallytotheco-sitedcase.Chrominanceoutputis
generatedusingafourtapfilterwithoneoftwodifferentcoefficientsetsdependingonwhichsource
chrominancepixeltheoutputpixelisclosest.
Notethatbecauseinputscalingislimitedto2x,fullBT.656widthoutputisnotachievedfromCIFsource
images.ThehorizontallocationofthereducedimagecanbeadjustedusingHOFFSET.
Figure4-16.2xCo-SitedScaling
104VideoDisplayPortSPRUEM1–May2007
SubmitDocumentationFeedback