DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

For a discussion of primary
chromaticities, see page 236.
people it now denotes any scaling of B’-Y’ and R’-Y’.
I will detail the formation of true Y’UV and Y’IQ in NTSC
and PAL chroma modulation, on page 335.
The coding systems described in this chapter can be
applied to various RGB primary sets – EBU 3213,
SMPTE RP 145 (or potentially even Rec. 709). Rec. 601
does not specify primary chromaticities: SMPTE RP 145
primaries are implicit in 480i systems, and EBU 3213
primaries are implicit in 576i systems.
The equations for [Y’, B’-Y’, R’-Y’], Y’P BP R, and Y’C BC R
can be based upon either the Rec. 601 luma coefficients
of SDTV or the Rec. 709 coefficients of HDTV.
The equations and figures of this chapter are based
upon the Rec. 601 coefficients. Unfortunately, the luma
coefficients that have been standardized for HDTV are
different from those of Rec. 601. Concerning the HDTV
luma coefficients, see Rec. 709 luma on page 292; for
details of HDTV color difference components, see
Component video color coding for HDTV, on page 313.
Surprisingly, broadcasters in Japan apparently intend to
retrofit their SDTV broadcast plant with Rec. 709 luma
coefficients according to the equations that I will detail
in the following chapter, Component video color coding
for HDTV.
Chroma components are properly ordered B’-Y’ then
R’-Y’; or P B then P R ; or C B then C R . Blue associates
with U, and red with V; U and V are ordered alphabetically.
The subscripts in C B C R and P B P R are often written
in lowercase. In my opinion, this compromises readability,
so I write them in uppercase. The B in C B serves
as a tag, not a variable, so I set it in Roman type (not
italics). Authors with great attention to detail sometimes
“prime” C BC R and P BP R to indicate their nonlinear
origin, but because no practical image coding system
employs linear-light color differences, I consider it safe
to omit the primes.
302 DIGITAL VIDEO AND HDTV ALGORITHMS AND INTERFACES