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DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

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Component video<br />

color coding for HDTV 26<br />

In the previous chapter, Component video color coding<br />

for SDTV, I detailed various component color coding<br />

systems that use the luma coefficients specified in<br />

Rec. 601. Unfortunately, for no good technical reason,<br />

Rec. 709 for HDTV standardizes different luma coefficients.<br />

Deployment of HDTV requires upconversion and<br />

downconversion capabilities both at the studio and at<br />

consumers’ premises; this situation will persist for a few<br />

decades. Owing to this aspect of conversion between<br />

HDTV and SDTV, if you want to be an HDTV expert,<br />

you have to be an SDTV expert as well!<br />

Today’s computer imaging systems – for still frames,<br />

desktop video, and other applications – use the<br />

Rec. 601 parameters, independent of the image’s pixel<br />

count (“resolution independence”). As I write, it isn’t<br />

clear whether Rec. 601 or Rec. 709 coding will be used<br />

when computer systems start performing HDTV editing.<br />

To me, it is sensible to retain the Rec. 601 coefficients.<br />

In this chapter, I assume that you’re familiar with the<br />

concepts of Luma and color differences, described on<br />

page 281. I will detail these component sets:<br />

• B’-Y’, R’-Y’ components, the basis for P B P R and C B C R<br />

• P BP R components, used for analog interface<br />

• C BC R components, used for digital interface<br />

313

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