Time code is an electronic numerical data recorded or embedded into
the signal, which allows professional audio & video playback and recording gear to be synchronized
with frame accuracy. With timecode, each frame or location on a tape or media stream
is assigned a unique number. This allows us to access that specific frame
or location again and again with frame
Its format is like a 24 hour clock: xx:xx:xx:xx.
from 00 to 23, "minutes" range from 00 to 59, "seconds" range
from 00 to 59, "frames" ranges from 00-29 (NTSC)
During recording, the camcorder, videotape recorder or audio deck (capable
of recording timecode) generates the numbers and records them to tape
Here in the US with our NTSC standard, weve been taught that video
runs at 30 frames per second- actually its 29.97. While we count
it on a 30 frames per second basis, video runs at 29.97 frames per second.
This 3/100 of a second difference seems small but significant over long
periods of time. This difference has lead us to two different ways to
count or number timecode.
Drop-frame vs Non-drop frame
There are two ways to count or create timecode: basic, (non-drop) frame
and drop frame.
In basic (non-drop) timecode, each new frame of video is assigned the
next higher number (06:01:00:29 becomes 06:01:01:00)
The problem with basic non-drop timecode is that the frame numbers drift
from the actual elapsed time of a program.
Imagine you have to edit a program for the network that is exactly 2
hours long. You begin your timeline at 01:00:00:00. You edit your piece
and end the final fade to black at 2:59:59:29. Everything's peachy, right?
If you used basic (non-drop) timecode, your program is too long. The
end is unfortunately cut off by about 7 seconds. Because of this you
lose your job, your partner dumps you because you're a loser, and he/she
takes the dog and the car. Before you know it you're out on the street.
Your target was 2 hours (120 minutes)
120 minutes x 60 seconds = 7,200 seconds.
7,200 seconds x 30 frames = 216,000 frames (assuming 30 fps)
But video actually runs at 29.97 frames per second. That's a 3/100ths
of a second difference from 30 frames per second.
So instead of 7,200 x 30, think
7,200 x 29.97 = 215,784 (this is the total number of frames in 2 hours
216,000 - 215,784 = 216 extra frames
216 / 30 = 7.2 That means the last 7.2 seconds of your show would
be cut off!
If you set your timeline to drop-frame you would avoid this problem.
(Or if you're doing linear editing, set your edit VTR to drop-frame)
Drop frame time code is harder to calculate, but it provides a numbering
system that is more accurate, timewise. It compensates for the 3/100s
of a second difference by not actually dropping frames, but by skipping
In drop frame time code, the frame numbers 0 and 1 are removed (skipped)
from each minute except for every tenth minute (starting from the first).
That is, minute 00, 10, 20, 30 and so on, do not have any frame numbers
dropped, but all other minutes do.
You can usually tell when something is drop frame because the time code
display has semicolons (06;01;00;29 becomes 06;01;01;02)
The reality is that for short projects (a few minutes) it doesn't matter
too much. But whenever you are editing longer projects, be sure to use
drop-frame. This is considered the network standard.
You can download shareware timecode calculators on the Internet. A favorite
of mine on the Mac is TC Calc. (google it to find it)