DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

Color science
for video 22
Classical color science, explained in the previous
chapter, establishes the basis for numerical description
of color. But color science is intended for the specification
of color, not for image coding. Although an understanding
of color science is necessary to achieve good
color performance in video, its strict application is
impractical. This chapter explains the engineering
compromises necessary to make practical cameras and
practical coding systems.
Video processing is generally concerned with color
represented in three components derived from the
scene, usually red, green, and blue, or components
computed from these. Accurate color reproduction
depends on knowing exactly how the physical spectra
of the original scene are transformed into these components,
and exactly how the components are transformed
to physical spectra at the display. These issues
are the subject of this chapter.
Once red, green, and blue components of a scene are
obtained, these components are transformed into other
forms optimized for processing, recording, and transmission.
This will be discussed in Component video color
coding for SDTV, on page 301, and Component video
color coding for HDTV, on page 313. (Unfortunately,
color coding differs between SDTV and HDTV.)
The previous chapter explained how to analyze SPDs of
scene elements into XYZ tristimulus values representing
color. The obvious way to reproduce those colors is to
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