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Now that you’ve recorded it, what shall you do with it? The recording
of the sound and picture on set is the production phase, now we’re in
postproduction.
Transfer
You’ll be working in an editing system and must get the audio media
into it. If you’ve recorded onto a device with a hard drive or flash
card, you’re close to home. As long as you keep the file format, speed
and resolution of the audio the same as the original recording, you can
copy onto any digital media with impunity -- CD, DVD, firewire drive,
SCSI drive, flash card, jump drive, ipod, FTP, email and your laptop,
all different containers for the stuff you’ve digitized. It is good
practice to confirm some parameters of your copies to make sure you are
copying the data correctly. Check things as file size and file format
to make sure the copy matches the source. It’s never a bad idea to
actually open up the copied file and listen for that bit of certainty
that life so rarely offers.
If you recorded to tape, you’ll have to transfer the audio into the
system in real time. From DV, you will load audio into your system via
firewire. This digital transfer in theory should make a perfect copy of
the audio. Even digital-to-digital copies can be corrupted with
clocking errors and other noise. Listen to the result of the transfer
for distortion, change in level, little tiny clicks or pops and summing
of tracks from stereo into mono. The DV will start with two tracks, and
there should be two tracks once it’s in your system.
Copying audio from CD’s usually entails a sample rate conversion, since
you will likely be editing at 48khz and CD’s are 44.1khz. Be sure to
actually copy the files as converted 48khz audio. If you don’t, your
system must convert the sample rate on the fly. This is bad because it
makes your system work harder and may contribute to overall performance
problems. More maddening is that mixed sample rates can trip up your
OMF export later, so keep your audio consistent within your system.
If you’re coming from DAT, 1/4”, cassette or minidisc, you’ll be
getting in via analog. Use a system with best quality audio converters,
and listen carefully to the transferred audio over good speakers to be
sure it all worked. Real time transfers are subject to many little
issues that may alter the audio, and you always want the audio to be as
close to identical to the original as possible.
Editing
You can do a perfectly acceptable sound edit on your picture editing
system, even one that is of the lower budgetary kind. The most
time-consuming aspects of editing are finding the right audio and
arranging it on tracks in an orderly manner. So long as you acquire the
audio as a digital file, such as copying from a CD or via firewire, the
sound quality will be identical to a more expensive system. If you are
coming in analog, such as through a microphone and preamp, you will
want to be sure that the converter hardware into which these are
plugged be of high quality. Working in Pro Tools or some other editing
system can be a great way to go because an experienced operator can
work more quickly in a system optimized for sound editing. In any case,
you’ll have to work with the audio to some extent while doing the
picture edit just to make sure the current cut of the film is
functioning, artistically. The following editing tips apply to all
systems.
The edit is where you choose the audio you will use in your final
product. If your film is using only the audio recorded on location,
such as a documentary, you will edit the existing audio so that it can
be mixed into a smooth whole. One would think this would be the easiest
kind of edit, as there tend to be fewer tracks with less added
ambiences and effects. In truth, these are difficult because there is
no place to hide. This is because of masking.
Masking is a psychoacoustic effect where one sound hides another, and
it is the bedrock of audio editing for film. It is only natural when
you record your sound on location that audio from one shot may not
necessarily match that of the next shot. This is due to unavoidable
variations in microphone placement relative to the room where you place
it and relative to the subject, you are recording. When the audio of
adjacent shots does not match, you must smooth it out. You can do this
in two ways.
Ease the transitions with audio dissolves. If the background sound
(room tone) abruptly shifts from one shot to another, the shots must
overlap and dissolves added between them. These soft transitions fool
the ear into thinking that the reality between the two previously
unrelated shots is continuous in the reality of the film. How much
transition do you need? It depends upon how different the adjacent
shots are. The bigger the contrast between shots, the longer the
required transition. If audio between shots is identical, you may need
no transition at all and a hard cut between shots will be acceptable.
Slightly contrasting shots may need a half-second or less. Severely
contrasting shots may require a couple of seconds of dissolve between
them. You will be limited by the amount of available overlap in your
takes. If a subject speaks non-stop, with no gaps between words, you
may have to build out room tone to have sufficient overlap.
Add room tone. If your audio takes have wide variations in background
noise, you must add some of the noisy room tone in a separate track
under the quiet (well recorded) takes to help even it out. The
implication is clear: the overall room tone of a scene cannot be lower
than that of the noisiest take. A scene that can be spread over two
tracks will thus end up with at least a third track of tone that will
make it play consistently.
Consistency is more important to how sound in a film plays than overall
noise level. If an audience hears jumps in noise level between shots
they will be taken out of the film without quite knowing why.
If a scene is too noisy, you may wish to re-record the dialogue for
that scene, also called ADR (automatic dialogue replacement), looping
or dubbing. This is a complex undertaking, involving scheduling the
actors into a studio, causing them to re-read their lines with the
appropriate energy and interpretation, adding ambience to match the
original production sound and adding foleys of any sounds the actors
may have made while doing the original scene, such as walking or
shifting about in their chairs. The director must work with the actors
and the sound engineer must coax them to make it work. It doesn’t sound
like the original and people become cranky. In the case of a
documentary, there are probably no actors, just subjects who may not be
available, willing or even capable of performing such a task. Replacing
dialogue is hard, so it is best to consult a professional.
Music editing. In films with tight budgets, music is usually added
while the picture is being edited. Music is either taken from CD’s
(with the appropriate permissions) or composed on a separate system and
dropped in as mixed sound files. The music cues are placed to work with
the picture; various music cues may be tried before finding the one
that works best. Cues may be chopped up, re-arranged, truncated and
duplicated once they are on the tracks to make them shorter or longer
or to generally fit the picture better. Music has its own set of rules,
and having a person with musical chops involved in the edit insures
that the music retains its feel. Audiences will sense changes in music
even when it is playing under dialogue, so try to keep your tempos,
rhythms and progressions in the pocket.
Effects editing. You may enhance the feel of a film by adding sound
effects to it. Hard effects, the kinds that sync up with images on the
screen can add detail, realism and impact to a scene in addition to
helping to draw focus to specific events in the frame. If money is
changing hands at the bottom of the frame, a little paper crinkle at
the right moment will call attention to the action. Background
ambiences that run under entire scenes will make them play more easily
on the ear if not overdone.
Effects come from production sound, effect libraries, Foley work and
postproduction field recording. For those regularly engaged in post
production, it is essential to have at least one good sound effects
library; thirty or forty well-indexed CD’s will last you a long time.
They cost more than regular CD’s because legal rights are included in
the price of purchase. One would think that effects from such a library
would be easily overused, but because these effects come layered with
existing production sound they have a longer life than their visual
clip art counterparts do.
OMF exports. If you have to move your edited audio from one system to
another, you’ll be doing an OMF export wherein you convert the various
tracks, regions and audio media into a lump of data that can be opened
in Pro Tools or other mixing system. This operation should be
coordinated with whoever is doing your mix. If you mix within your
editing system, you will not need an OMF.
Mixing
Once all of the audio has been selected and placed in the sound edit,
it is mixed. Filtering and equalization is added as well as reverb and
other effects. The balance between the various elements is decided, and
the overall absolute volume is set. If your distributor has
requirements for the elements, the mixer makes sure that the final
audio conforms to the specifications. If you do one audio operation at
a post house, it should be the mix.
Equivalent to a video online session, the mix is where you put the
finish on the sound for your film. The mix room must have a high
quality mixing system. The room must be quiet and comfortable for the
hours of work that is required for long-format projects. The speakers
must be of high quality, and the acoustics of the room must be neutral.
The picture must be viewed at a good resolution on a system that holds
sync, does not drop frames as some inexpensive firewire DV converters
do and does not introduce a delay in picture playback as some plasma
displays do.
Cost effective picture editing systems tend to have a handy toolbox of
audio gizmos to clean up your sound. Audio in these cases tends to be
an afterthought to the primary function of the systems, which is to
edit video. A dedicated mix room with an experienced mix engineer will
be an improvement on a picture edit mix every time. If you choose to
mix in your picture system, at the very least, you should set up your
room for audio, and all of the above requirements apply.
To mix you will need an OMF export and a picture reference tape. The
OMF has all of the sound that has been prepared in your picture system.
The picture that you must mix to is the reference tape. The most
efficient workflow is to lock your picture prior to mixing which will
save you the labor of having to recut the audio in your mixing system
to match updated image edits. You should take care with the reference
tape to insure that it is an accurate output from your system, with no
dropped frames or other mayhem. It should have a reference mix on the
audio tracks of the tape. The tape must have a 2 pop at the head and
again at the tail of the program; the OMF must have a beep to
correspond to each 2 pop in the picture. Armed with a good reference
tape and an OMF, you can trust the sync of the sound with the picture
and you will be able to make any final sync adjustments to the audio
during the mix.
If you’re new at this and decide to mix the project yourself, check the
mix on a variety of playback systems to insure consistency of
intelligibility, sync, balance, loudness and overall tone. The world of
consumer audio is a treacherous and chaotic landscape for homo sonus,
and a mix will not play back the same on any two systems. The goal is
to craft a mix that holds up well on the greatest number of systems.
People who mix sound regularly have many opportunities to hear their
finished work over the life of a given film which helps them make good
decisions while doing the mixing.
To maximize your odds and accumulate some of your own knowledge, listen
to the mix very quietly. Play it in the living room and listen from the
kitchen. Listen over big speakers. Listen over small speakers. Play it
over your TV and compare it to ten of your favorite DVD’s of various
genres. Screen your mix for some viewers who are unfamiliar with the
film and do a little survey. Could they understand all of the dialogue?
Did the film lose them at any point? These sorts of inquiries will help
you gain valuable insight into how well the sound is functioning in
your film and sharpen your ears besides.
To Summarize:
Transfer the audio from your location sound device into your editing
system as accurately as possible.
Assemble all of the sound for your film in one place. This is your
sound edit. It includes arranging the dialogue for the mix as well as
adding effects and music.
Mix the edited sound to create the final product. Apply equalization
and other effects and set the absolute level of the program.
If you’re mixing it yourself, listen to the mix on a variety of systems
for greatest consistency of playback.
Our next installment will cover final audio formats and output of your
finished mix.
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Carmen Borgia is the head of audio services for DuArt Film & Video
in New York City. He oversees a post production sound department that
provides mixing, sound design, restoration, transfer and printmastering.
His department caters to independent projects in all formats from mono
optical up to digital 5.1.
Editor’s note: If anyone has any questions, please submit them to
cborgia@duart.com. Carmen will
do his best to answer any of your queries.
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The
Art And Technology Of Listening, Part 3