Sync Path for Film: Overview
On location, audio is recorded onto analogue recorders like a Nagra (1/4"
reel - reel tape recorder), a Walkman Pro (portable audio cassette) or
a digital recorder or DAT. Synchronization on professional shoots usually
involves the use of SMPTE time code and the use of a stereo Nagra or a
"time code DAT".
For semi-pro and student shoots, it is more common to find a mono Nagra
using Pilot tone or a more simple, less expensive DAT. In any situation
where lip sync is required, the camera must run at an exact 24 frames per
second (generally 25 fps outside of North America). Also the camera must
be relatively silent (or blimped) - especially when filming indoors.
|For the student shoot, the Nagra maintains synchronization with the
film through the Pilot tone recorded on the tape.
|The slate or clapper plays a key role in this process
by providing the sound and image for synchronization and by identifying
pertinent sections of the project for screening "dailies" and for post
|The procedure is for the recordist to start the recorder and to state
("rolling") when the device is ready to synchronize (for the Nagra this
is when the white Pilot tone flag is visible on the recorder, for time
code DATs this is when time code input is indicated) and for the clapper/loader
to position the slate in front of the camera. The boom is positioned near
the slate and when the two parts of the slate are snapped together after
the camera has started filming, the scene, roll number, take, etc., are
announced and the filming begins in earnest. The film is processed and
either (usually) transferred to video for editing or a work print is made
and that is cut on an editing machine.
The Nagra tapes may be transferred via a resolver to a number of different
Magnetic film, using a magnetic film recorder (Magnasync, Magnatech, etc.)
Digital Audio Workstation (DAW) such as a Macintosh running Deck, ProTools,
Non-linear Video Editor such as an Avid, or DVision, etc.
To all Systems
In the systems listed above there are many principles common to all.
Primary is the splitting of sound into various tracks (real or virtual).
The usual categories are:
dialogue (minimum 2)
|The second major principle is laying the sound onto these tracks so
that sounds in the same category which follow another closely are placed
on different tracks. (Checker boarding or splitting tracks). This is necessary
for the mixing stage which is to follow and insures flexibility as well
as proper level and equalization settings.
Once the tracks have been prepared the next step is to prepare for "the
"The mix" refers to when the tracks are mixed to the final presentation
The usual venue is a studio configured for this purpose with a large
and a mixing console customized for this purpose.
Preparation for this with magnetic film requires running the
audio tracks through a synchronizer.
This is a simple hand cranked system which insures that the tracks are
in sync by providing interlocked sprocket wheels for all of the audio tracks
and the work print. This process is necessary because editing machines
(like Steinbeck) cannot always be trusted to be frame accurate.
|An accurate mixing sheet is then drawn (DAWs can create these automatically)
for the mixers to follow. In the mixing studio a wide variety of audio
playback and image systems may be found. Conventional studios use 16 or
35 mm dubbers or sound film playback machines synchronized to the work
print or a black and white copy of the work print known as a slash print.
The later may be marked with punched holes (cue punch) or lines (streamers)
as visual cues for the mixers. A video projector may be used instead of
a film projector: although the image lacks resolution, video rewinds/fast
forwards much faster than film. Audio may also be stored on analogue or
digital multitrack, time code DAT, sound film loops or be mixed directly
from a professional DAW (such as a Synclavier or a ProTools system).
These various sources are mixed to a multitrack format - the minimum
being three (dialogue, sfx, music) for mono releases. This is required
to allow the dialogue to be dubbed into another language without affecting
sfx or music and to facilitate the mixing process. (Usually dialogue is
mixed first, then sfx and foley, followed by music.) Various mixes will
be done for feature films; Dolby Surround, mono, International (w/o dialogue),
The multitrack mix tape is then transferred to optical film, video or
digital film format for release.