DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

Table 6.3 Video systems are
classified as analog or digital,
and component or composite
(or S-video). SDTV may be
represented in component,
hybrid (S-video), or composite
forms. HDTV is always in
component form. (Certain
degenerate forms of analog
NTSC and PAL are itemized in
Table 49.1, on page 581.)
The 4f SC notation will be
introduced on page 108.
By NTSC, I do not mean 525/59.94
or 480i; by PAL, I do not mean
625/50 or 576 i ! See Introduction
to composite NTSC and PAL, on
page 103. Although SECAM is
a composite technique in that luma
and chroma are combined, it has
little in common with NTSC and
PAL. SECAM is obsolete for video
production; see page 576.
HDTV Component R’G’B’,
709Y’P B P R
SDTV
Component R’G’B’,
601 Y’PBP R
Hybrid S-video
Analog Digital
Composite NTSC, PAL 4f SC
4:2:2
709Y’C B C R
4:2:2
601 Y’CBC R
remains in use for analog broadcast and in consumers’
premises; much composite digital (4f SC ) equipment is
still in use by broadcasters in North America. However,
virtually all new video equipment – including all
consumer digital video equipment, and all HDTV equipment
– uses component video, either Y’P B P R analog
components or Y’C B C R digital components.
A video system can be classified as component HDTV,
component SDTV, or composite SDTV. Independently,
a system can be classified as analog or digital. Table 6.3
above indicates the six classifications, with the associated
color encoding schemes. Composite NTSC and PAL
video encoding is used only in 480i and 576i systems;
HDTV systems use only component video. S-video is
a hybrid of component analog video and composite
analog NTSC or PAL; in Table 6.3, S-video is classified in
its own seventh (hybrid) category.
Conversion among systems
In video, encoding traditionally referred to converting
a set of R’G’B’ components into an NTSC or PAL
composite signal. Encoding may start with R’G’B’,
Y’CBCR, or Y’PBPR components, or may involve matrixing
from R’G’B’ to form luma (Y’) and intermediate [U, V] or
[I, Q] components. Quadrature modulation then forms
modulated chroma (C); luma and chroma are then
summed. Decoding historically referred to converting an
NTSC or PAL composite signal to R’G’B’. Decoding
involves luma/chroma separation, quadrature demodulation
to recover [U, V] or [I, Q], then scaling to recover
[CB, CR] or [PB, PR], or matrixing of luma and chroma to
recover R’G’B’. Encoding and decoding are now general
CHAPTER 6 RASTER SCANNING 63