Apple Final Cut Pro 6 - Manual (Page 1901)

418 Part V Appendixes
Telecine, Pull-Down, and Reverse Telecine
The following section describes methods for embedding and extracting 24p video in
different formats. Some of these techniques are based on existing film-to-video
methods, and some are newer approaches. The basic technique for transferring film to
video, called telecine, uses a process called pull-down to map 23.98 fps film to 29.97 fps
interlaced video. Once the video is captured on disk, software can perform reverse
telecine, or reverse pull-down, to restore the original 23.98 fps film frame rate.
In progressive digital video systems such as 720p60 DVCPRO HD video, a similar process
can be performed in-camera to map 23.98 fps to 59.94 fps, but entire frames are
duplicated instead of fields. During or after capture, the duplicate frames are removed.
A camcorder or deck that performs duplicate frame insertion can add metadata (known
as flags) that inform software when to remove or ignore duplicate frames.
Note: Pull-down refers to the addition or removal of fields, not duplicate frames.
Standard 3:2 Pull-Down
Also known as 2:3:2:3 pull-down, this is the standard telecine method of transferring
film to NTSC video. The film is slowed by 0.1 percent (a factor of 1000/1001) from 24 fps
to 23.98 fps and then each film frame is transferred to interlaced video in a repeating
2:3:2:3 field pattern.
In the illustration below, film frames A, B, and D are mapped to video frames 1, 2, and 5.
However, because film frame C is split into two fields across video frames 3 and 4,
pull-down removal requires deinterlacing, which is more processor-intensive than
removal of pull-down patterns such as advanced (2:3:3:2) pull-down. Pull-down
removal typically requires manual identification of the A frame in the pattern, which
you can identify visually by moving frame by frame through your footage until you
recognize the pull-down pattern.
24 Versus 23.98 fps
Although the term 24p implies 24 frames per second, the value 24 is usually
inaccurate, because most people working within NTSC standards actually shoot at a
frame rate of 23.976 fps (commonly referred to as 23.98 fps). On the other hand, 24 fps
footage transferred to PAL, as well as most film, is recorded at exactly 24 fps.
Although it may be easier to say “24p,” keep in mind that in some cases, such as during
audio post-production, it’s critical to state the exact frame rate of your footage.