DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

Poynton, Charles, “Motion
portrayal, eye tracking, and
emerging display technology,” in
Proc. 30th SMPTE Advanced
Motion Imaging Conference (New
York: SMPTE, 1996), 192–202.
Historically, this was called
3-2 pulldown, but with the
adoption of SMPTE RP 197, it is
now more accurately called
2-3 pulldown. See page 430.
The progressive segmented-frame
(PsF) technique is known in
consumer SDTV systems as quasiinterlace.
PsF is not to be confused
with point spread function, PSF.
Flicker is minimized by any display device that produces
steady, unflashing light for the duration of the frame
time. You might regard a nonflashing display to be more
suitable than a device that flashes; many modern
devices do not flash. However, if the viewer’s gaze
tracks an element that moves across the image,
a display with a pixel duty cycle near 100% – that is, an
on-time approaching the frame time – will exhibit
smearing of that element. This problem becomes more
severe as eye tracking velocities increase, such as with
the wide viewing angle of HDTV.
Film at 24 frames per second is transferred to interlaced
video at 60 fields per second by 2-3 pulldown.
The first film frame is transferred to two video fields,
then the second film frame is transferred to three video
fields; the cycle repeats. The 2-3 pulldown is normally
used to produce video at 59.94 Hz, not 60 Hz; the film
is run 0.1% slower than 24 frames per second. I will
detail the scheme in 2-3 pulldown, on page 429. The
2-3 technique can be applied to transfer to progressive
video at 59.94 or 60 frames per second. Film is transferred
to 576i video using 2-2 pulldown: Each film
frame is scanned into two video fields (or frames); the
film is run 4% fast.
Segmented frame (24PsF)
A scheme called progressive segmented-frame has been
adopted to adapt HDTV equipment to handle images at
24 frames per second. The scheme, denoted 24PsF,
samples in progressive fashion: Both fields represent the
same instant in time, and vertical filtering to reduce
twitter is both unnecessary and undesirable. However,
lines are rearranged to interlaced order for studio distribution
and recording. Proponents of the scheme claim
compatibility with interlaced processing and recording
equipment, a dubious objective in my view.
Video system taxonomy
Insufficient channel capacity was available at the outset
of television broadcasting to transmit three separate
color components. The NTSC and PAL techniques were
devised to combine (encode) the three color components
into a single composite signal. Composite video
62 DIGITAL VIDEO AND HDTV ALGORITHMS AND INTERFACES