Calculated Industries 9226 - Manual (Page 4)

NTSC (“SMPTE”) Time Code
There are two types of NTSC 30 frames-
per-second (fps) time code commonly
used in North America and Japan: Non-
Drop Frame (30
NDF
) and Drop Frame
(30
DF
). These time codes are both differ-
ent than real clock time since they typi-
cally run at a reference rate of 59.94 Hz
rather than true clock rate of 60 Hz: Since
each video frame is composed of 2 inter-
laced fields, the NTSC signal translates to
59.94 fields per second, which, when
divided by 2 fields per frame, yields 29.97
fps, not 30. The resultant speed is 0.1%
slower than real time.
Non-Drop Frame Time Code
Commonly used because of its simplic-
ity, Non-Drop Frame Time Code makes
no attempt the compensate for this real
time discrepancy — about 3.6 seconds in
one “hour” of 30
NDF
time code (i.e., one
“hour” of 30
NDF
time code equals
approximately 1 hour and 3.6 seconds of
real time). Again, this is when the time
code is referenced to 59.94 Hz.
G
ETTING
S
TARTED
4 – Frame Master ® II