DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

Square sampling
Component 4:2:2
Rec. 601
Composite 4fsc
Monochrome systems having
405/50 and 819/50 scanning
were once used in Britain and
France, respectively, but transmitters
for these systems have now
been decommissioned.
525
525
525
480i29.97 SCANNING 576i25 SCANNING
480
780
640
858
704 or 720
480
483
NTSC
910
768
Analog broadcast of 480i usually uses NTSC color
coding with a color subcarrier of about 3.58 MHz;
analog broadcast of 576i usually uses PAL color coding
with a color subcarrier of about 4.43 MHz. It is important
to use a notation that distinguishes scanning from
color, because other combinations of scanning and
color coding are in use in large and important regions of
the world. Brazil uses PAL-M, which has 480i scanning
and PAL color coding. Argentina uses PAL-N, which has
576i scanning and a 3.58 MHz color subcarrier nearly
identical to NTSC’s subcarrier. In France, Russia, and
other countries, SECAM is used. Production equipment
is no longer manufactured for any of these obscure
standards: Production in these countries is done using
480i or 576i studio equipment, either in the component
domain or in 480i NTSC or 576i PAL. These studio
signals are then transcoded prior to broadcast: The color
encoding is altered – for example, from PAL to
SECAM – without altering scanning.
96 DIGITAL VIDEO AND HDTV ALGORITHMS AND INTERFACES
625
625
625
944
768
576
576
576
864
720
1135 4 ⁄ 625
Figure 11.1 SDTV digital video rasters for 4:3 aspect ratio. 480i29.97 scanning is at the left,
576i25 at the right. The top row shows square sampling (“square pixels”). The middle row shows
sampling at the Rec. 601 standard sampling frequency of 13.5 MHz. The bottom row shows
sampling at four times the color subcarrier frequency (4f SC ). Above each diagram is its count of
samples per total line (S TL ); ratios among S TL values are written vertically in bold numerals.
See PAL-M, PAL-N on page 575,
and SECAM on page 576.
Consumer frustration with a diversity
of functionally equivalent standards
has led to proliferation of
multistandard TVs and VCRs in
countries using these standards.
30
33 :
35 :
PAL
948
33 : 36 1 ⁄ 18