Is Timecode Always Necessary?
By Fred Ginsburg, C.A.S.
There is a trend in our industry
for clients and producers to clamor for the newest and latest technology,
regardless of whether or not that technology will really improve the end
product.
Case in point, recording SMPTE timecode on the audio track for shows that will
be edited non-linear.
Having SMPTE timecode on the audio track that will match timecode on the picture
is nice, but far from absolutely necessary. Considering the expense of
purchasing or renting timecode recorders and timecode slates compared to being
able to use existing non-timecode equipment, one should definitely explore all
of the post-production ramifications before blindly leaping into costly, albeit
trendy, production sound decisions.
Did you know that for the first few seasons, TV shows such as Beverly Hills
90210 did not use SMPTE timecode when recording production sound? All audio was
done with the venerable Nagra 4.2, and then transferred to non-linear digital
for post. Why? Because it was cheaper to do it that way, and gave them the same
results!
Here is what happens when audio is recorded with SMPTE timecode. Timecode is
recorded, along with production sound, on a timecode recorder such as the PD6,
PD4 DAT, FR2TC, or Nagra IV-STC. Matching (jam sync'd) timecode may or may not
be recorded on the film by means of in-the-camera keycode and an Aaton master
clock module. A Denecke slate is filmed at the head of each scene, displaying a
visual timecode as well as providing an old fashioned clapstick marker.
In post, the film is transferred to video in the telecine and then digitized
into the non-linear editing system. Audio is resolved at the proper speed
(slowed down slightly to match the picture slowdown created by telecine) and
also digitized into the non-linear system. Using the timecode numbers as a
beginning of the scene startmark or line-up reference, the editor performs a
series of in-computer audio insert edits to sync up the dailies (matching up the
picture and corresponding sync audio) for each take. (Some people are lazy and
just let the lab do it during telecine, but the labs charge you plenty for it.)
Now, examine what happens if no timecode is recorded on the audio during
production. Just as before, the picture is loaded into the edit computer. Audio
is resolved at the proper speed, and also digitized into the system. In order to
sync the dailies, the editor goes to the picture start of the take (clapstick
frame) and marks it. Audio is advanced to the audio marker (the clapstick
impact); and then the mark-in or match edit points are punched in.
Finding the start mark of the audio without timecode is easy. If one watches the
visual waveform of the audio (the optical track), it is rather easy to locate
the clapstick because it sticks out like the Washington Monument! With very
little practice, an editor can sync dailies almost just as fast as with timecode,
and at considerable savings of the production budget.
But without timecode, how does the edit computer keep everything in sync? The
same way it always does, by means of its own internal timecode. Since most
production timecode is discontinuous, it is only used for negative matching; the
actual editing is done with a form of continuous timecode within the system.
It is true that without timecode, we cannot go back to the original production
audio tapes and conform them with the negative for post. But why would we want
to or need to? The audio coming out of the non-linear system is digital CD
quality or better, far higher quality than we ever got off of a Moviola. In the
old days of tape splicing, we had to re-transfer and conform the audio in order
to correct for all of the damaged sprocket holes, bad splices, and unintentional
edits. But since out digital soundtrack is perfect, we do not need to return to
the original tapes before moving on to advanced soundtrack building.
The only step a little tricky in this non-timecode audio process is resolving.
When using timecode, we normally record on the set at 30 fps non-drop, and then
transfer at 29.97 non-drop in order to compensate for the fact that picture
filmed at 24 or 30 fps (film speed) ends up being slowed down to 23.97 or 29.97
fps (film speed) in the telecine in order to be recorded onto videotape (which
is 29.97 video speed).
If we use a conventional Nagra recording with a 60Hz sync signal, then we must
transfer that audio into the edit computer at 59.94Hz. This can be very easily
done by using an external sync box such as the TX-10 59.94 Crystal (available
from Equipment Emporium) or a similar device. Just unplug the crystal jumper
plug from the side of the Nagra and plug in the matching connector from the
59.94 external box; then play the Nagra back with resolver engaged as one
normally would.
If recording with a portable digital recorder, the process is more complicated.
Either the digital recording can be transferred to an analog machine such as a
Nagra and resolved as previously described (either on a timecode Nagra or a 60Hz
Nagra); or else the digital recording (e.g. DAT) could be played back on a
special studio decks capable of altering its sampling rate to perform the
required slowing down.
Most of the newer non-linear edit systems offer a software utility whereby the
end user can slow down the audio directly during the digitizing input process.
For instance, it is a simple routine to modify the speed of an audio clip in
Final Cut Pro by slowing it to 99.9 % to achieve a 0.1% pulldown.
If your edit system lacks a pull-down, slow-down, or pitch function -- then just
bring the audio tracks FIRST into an audio editing program (there are gobs of
them out there) and perform the correction there. Then import the file into your
video edit program for syncing.
We suggest that filmmakers do heads & TAIL clapstick slates of their first few
scenes so that it will be easy for the editor to check sync and verify that the
pull-down in being done correctly.
Of course, if you are shooting in normal video -- there is no pulldown of the
audio required, since the picture does not go through any speed change the way
that sprocketed film does. Just record normally on your Nagra, DAT, or digital
recorder and transfer your audio directly to your edit system. Sync picture and
sound via the clapsticks, but do not worry modifying the speed of your audio.
Everything is still in its original REAL TIME.
Unless, you have chosen to shoot in 24fps Progressive Video mode. This gets us
back to the film style pulldown issue, since your original video is being
modified by the edit system to playback at 29.97fps. Depending on the software
that you are using to edit with, you may or may not have to make audio
corrections. (If you recorded audio directly to the camcorder, there is not
problem, since the 24frame picture with sound is converted together.) Again, do
head and tail clapsticks on a few takes to help you determine what corrections
need to be made.
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