Apple Final Cut Pro 7 - Manual (Page 1924)

What Is Timecode?
Timecode is a signal recorded with your video that uniquely identifies every frame of
your tape using a time stamp in hours, minutes, seconds, and frames. Timecode uses the
following format:
Hours Minutes Seconds Frames
SMPTE timecode
01:32:15:28
Timecode was invented in the late 1960s so that computer video editing systems could
automatically find specific frames on tape and record editing decisions that could then
be performed over and over again. The Society of Motion Picture and Television Engineers
(SMPTE) standardized several electronic timecode formats for video in 1967.
Note: Other types of address code, such as keycode and ink numbers, are used for editing
film. For more information, see the documentation that came with Cinema Tools.
About Drop Frame and Non-Drop Frame Timecode
NTSC video (black-and-white) originally had a frame rate of 30 fps, so the timecode
counted at 30 fps. However, NTSC color video (the only kind of NTSC video in use today),
has a frame rate of 29.97 fps. This subtle difference between 30 fps and 29.97 fps seems
practically negligible and, in many cases, ignoring this discrepancy is fine. But not always.
What editors needed, especially in expensive broadcast markets, was timecode that
accurately reflected the exact duration of a program on tape.
There are two types of 30 fps timecode for use with NTSC video: non-drop frame and
drop frame. Non-drop frame timecode is simple: for every frame of video, there is a
corresponding timecode number. The timecode increments without any compensation.
In almost all cases, timecode is non-drop frame. In fact, drop frame timecode only matters
in the case of NTSC video.
Drop frame timecode compensates for the fact that the NTSC format has a frame rate of
29.97 fps, which is .03 fps slower than the nearest whole number frame rate of 30 fps.
Timecode can only be represented by whole numbers, so timecode numbers are
periodically skipped in drop frame timecode. This way, the timecode number always
matches the seconds and minutes of video that have played. NTSC can use either drop
frame or non-drop frame timecode.
Important: No video frames are dropped when you use drop frame timecode. Only the
associated timecode numbers are skipped.
1924 Appendix C Frame Rate and Timecode