Working with ntsc video, A b c d, 29 chapter 2 before you begin your film project – Apple Cinema Tools 4 User Manual
Page 29
Working with NTSC Video
The original frame rate of NTSC video was exactly 30 fps. When color was added, the rate
had to be changed slightly, to the rate of 29.97 fps. The field rate of NTSC video is 59.94
fields per second. NTSC video is often referred to as having a frame rate of 30 fps, and
although the difference is not large, it cannot be ignored when transferring film to video
(because of its impact on audio synchronization, explained in
).
Another issue is how to distribute film’s 24 fps among NTSC video’s 29.97 fps.
The most common approach to distributing film’s 24 fps among NTSC video’s 29.97 fps
is to perform a 3:2 pull-down (also known as a 2:3:2:3 pull-down). If you alternate recording
two fields of one film frame and then three fields of the next, the 24 frames in 1 second
of film end up filling the 30 frames in 1 second of video.
Note: The actual NTSC video frame rate is 29.97 fps. The film frame rate is modified to
23.98 fps in order to create the 3:2 pattern.
Before (23.98 fps)
A
B
A
B B
C
C
D D D
A B C D A
D A B C D A B C D A B C D A B C D
B C
A A B B B C C D D D A A B B B C C D D D A A B B
C C D D D A A B
B
B
C
C
D D D A
B
A
B B
C
C
D D
B
D
A B C D
A A B B B C C D D D
Field
1
Field
2
Field
1
Field
2
Field
1
Field
2
Field
1
Field
2
Field
1
Field
2
3:2 Pull-Down
After (29.97 fps)
One second
As shown above, the 3:2 pattern (actually a 2:3:2:3 pattern because frame A is recorded
to two fields followed by frame B recorded to three fields) repeats after four film frames.
Virtually all high-end commercials, movies, and non-live television shows use this process
prior to being broadcast.
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Chapter 2
Before You Begin Your Film Project