Specifications

4
A Digital Video Primer
Converting film
e term telecine refers to the combination of processes, equipment, and soware used to per-
form lm-to-video conversion. Pulldown techniques are used in the telecine process to convert
the 24 fps rate of lm to the approximately 30 fps rate of NTSC video and to handle the conver-
sion from progressive frames to interlaced elds.
Pulldown performs its magic without speeding the lm up by inserting redundant elds as the
lm is being transferred. Here’s how it works:
1. Film frame 1 transfers to the rst two elds of video frame 1.
2. Film frame 2 transfers to the two elds of video frame 2 as well as the rst eld of video frame 3.
3. Film frame 3 transfers to the second eld of video frame 3 and the rst of video frame 4.
4. Film frame 4 transfers to the second eld of video frame 4 and the two elds of video frame 5
and the process repeats.
By inserting two extra elds every 1/6th of a second, four lm frames ll ve video frames, and
24 frames ll 30.
3-2 or 2-3 pulldown is used to match the frame rate of lm (24 fps) to that of video (29.97 fps) for transferring.
e term cadence refers to the allocation of frames to elds. With a 2-3 cadence, the rst lm
frame is transferred to 2 elds, the second frame to 3 elds; with a 3-2 cadence, the rst frame is
transferred to 3 elds, the second frame to 2.
For PAL telecine, 2-2 pulldown is used, which allocates each lm frame to two video elds, yield-
ing the required 50 elds per second. e lm runs through the telecine machine at 25 fps, 4%
faster than normal speed, to compensate for the frame rate dierence.
Pulldown is also used to convert 24P video to 30p and 60i formats.
THE PROMISE OF 24P
Frame rate dierences and video interlacing com-
plicate the process of converting lm to video when
motion pictures are to be shown on TV. It’s even more
complicated when converting from video to lm.
Standards conversion (converting from one format
to another) often causes motion artifacts and softens
crisp images.
The advent of digital television has underscored the
need for a better way to move between formats. In
the U.S., the digital television mandate by the FCC
allows broadcasters to choose from among 18 dier-
ent SD and HD formats. These formats are specied
with a number indicating the lines of vertical resolu-
tion, and a letter indicating whether the display is
interlaced (i) or progressive (p). CBS and NBC have
chosen 1080i; ABC prefers 720p; and FOX works with
480p, 480i, and 720p. It sounds like the commence-
ment of chaos, doesn’t it? Imagine the poor producer
who must be prepared to deliver in one or more
formats.
The benets to the lm industry of having a suitable
digital production format are enormous. Savings on
the cost of traditional lm and lm processing, not to
mention the time required for lm processing is huge.
When digital eects are incorporated into footage,
lm must be digitized anyway, so being able to begin
with digital material makes sense.
The solution may be the 24P format—a 24 fps, pro-
gressive scanned HD image with 1080 lines of vertical
resolution. 24P digital cameras are delivering major
motion picture quality content, such as Star Wars: Epi-
sode Ill. Film is easily converted to 24P video, because
lm is 24 fps and compatible with progressive scan-
ning. Because it’s digital, you can make a single digital
master from which multiple formats can be produced
with virtually no generation loss: from NTSC or PAL, to
any of the HD formats, even lm.