DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

f FR
f H
30
= ≈ 29. 97 Hz
1. 001
9
= ≈ 15. 734 kHz
0. 572
It is confusing to refer to fields as
odd and even. Use first field and
second field instead.
480i component video 41
This chapter details the scanning, timing, sync structure,
and picture structure of 480i29.97
(525/59.94/2:1) video. The scanning and timing information
in this chapter applies to all variants of 480i
video, both analog and digital. The sync information
relates to component analog, composite analog, and
composite digital systems.
Frame rate
480i video represents stationary or moving two-dimensional
images sampled temporally at a constant rate of
30 ⁄1.001 frames per second. For studio video, the tolerance
on frame rate is normally ±10 ppm. In practice the
tolerance applies to a master clock at a high frequency,
but for purposes of computation and standards writing,
it is convenient to reference the tolerance to the frame
rate.
Interlace
A frame comprises a total of 525 horizontal raster lines
of equal duration, uniformly scanned top to bottom and
left to right. Scanning has 2:1 interlace to form a first
field and a second field; scan lines in the second field
are displaced vertically by half the vertical sampling
pitch, and delayed temporally by half the frame time,
from scanning lines in the first field. In MPEG-2 terms,
the first field is the bottom field.
Lines are numbered consecutively throughout the
frame, starting at 1.
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