Pre-Mixes, or Pre-Dubs

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Pre- Mixes , or Pre-Dubs

When you finally sit down to mix your project, you might find that there are so many tracks of different audio parts that the task of blending them all together at once seems impossible . All the audio tracks used in a film production could easily exceed the 200-track mark. It is not even possible for a current Pro Tools system to handle this track count by itself. Several systems would have to be linked together to provide that many tracks.

Due to the large size and complexity of post-production audio recordings, the technique of submixing related tracks together prior to a final mixdown is used to help simplify this daunting task. These submixes are called pre-dubs or pre-mixes .

Large film productions have several sound teams that work on different aspects of the film's soundtrack. Each team might generate one or more pre-mixes of their work that a mix engineer can use on the dub stage to create the final master or "dub" for the film. Often, mixers will prefer to have each individual track dry and without volume automation in order to combine and EQ them to their liking. This is especially true with dialog tracks. Matching the ADR dialog with production audio can be more accurately done on the dub stage with a calibrated monitor system, in the environment in which it will be heard by an audience. EQ-ing dialog, or any other sound, in a small editing suite that might have substandard monitoring and lots of environmental noise is probably not a good idea.

Find out ahead of time what is expected of you as relates to the overall sound production. If you are doing the entire sound editing and mixing job yourself, you can make up your own rules. If the mixers are expecting dry, unprocessed tracks and you provide entirely pre-mixed material without any options, you might not work there again. If you are mixing in a limited environment with only so many channels available and the editors provide 500 tracks for you to mix in two days, you might not appreciate it. Again, communication between all members of the production staff is the key to getting any project to completion. The responsibilities and job descriptions of editors and mixers are hotly debated topics among post-production professionals, and each situation will be different.

Typically, multiple pre-mixes will be created for each facet, or unit, of the sound production. Dialog, foley, sound effects, and music will each have its own set of pre-mixes. In addition to each pre-mix, certain key elements will be transferred to the final mix stage outside of the pre-mix, allowing for more detailed manipulation during the final mixdown. Principle characters ' dialog would be an example of tracks that you would want to keep separate and not mixed into a pre-dub.

NOTE

THE DUB STAGE

The "Dub Stage" is a studio that is basically built into a movie theater, such as Enterprise Post's Stage A, shown in Figure 8.25. This mixing room has the same basic acoustic characteristics as a typical movie theater. This way, a mixer can hear what the movie will sound like when it is played for an audience. Dub stages have very accurate and highly calibrated monitor systems that allow accurate control of the mix. While it is possible to mix a film in a small room, it's always preferable to mix film in a theater-like setting.

Enterprise Post's Stage A. Centered around a Neve Capricorn digital console with 202 inputs, the studio is connected to a machine room that has several Pro Tools systems and MMR-8 digital dubbers. This is a top- tier dub stage. The TV series 24 is mixed here, using 111 channels at mixdown.

Mixing Dialog

Mixing dialog that sounds natural and intelligible, and maintains enough dynamics to convey the emotion of the scene, is a challenging task. Often, one of these aspects is in direct opposition to the other. For example, to make a dialog more intelligible, compression is often used to increase the volume of quiet passages. This works directly against the principle of retaining dynamics within the dialog that convey the emotion of the scene, as compression is designed to remove dynamics. Many times, the dialog has to fight through a bevy of sound effects, music, and even explosions, while still sounding natural and clear. Making sure it does is what dialog mixing is all about. With experience, you will be able to reduce the dynamic range of dialog tracks to maintain clarity without losing the emotional impact.

Pre-Dub versus Final Mix

The task when creating a dialog pre-mix is to keep everything very natural so as to not limit your options during the final mixdown. You also might be creating this pre-mix for another engineer to use during the final dub, in which case keeping the dialogue as natural as possible is very important. He or she should be able to turn up the dialog tracks and hear every line, every nuance, of the dialog in a smooth, even, and yet dynamic mix. If you are preparing pre-dubs for a mix engineer, each character might have her own track with additional ones for supporting characters. Even within one character's dialogue there might be separate tracks for ADR takes and production audio. Dialog pre-mixes need to have as much flexibility as possible.

When creating a final mix, levels should be balanced between different characters and lines that correspond to the camera angles used during a scene. It should all make sense to the viewer. If, in one angle, a character is on the other side of the room saying his line, the sound should be slightly lower and perhaps more distant , with reverb perhaps. If the camera angle changes to a shot that is much closer to this character, even in the middle of a line, the sound should change to reflect the new camera angle: louder, more intimate, and with less reverb than before. This should happen on the exact frame that the camera angle changes. Automation is a real help when it comes to this type of task. Automation will be covered later in this chapter.

Another common technique for altering dialog tracks by camera angle is the use of checkerboarding . Checkerboarding requires two dialog submix channels. Let's call them A and B. As camera angles change, the character's dialog will jump from track A to track B. Both the A and B channels have entirely separate processing chains of equalizers, compressors, and so on. One dialog chain can be set up for sound that correlates to a certain camera angle and the other dialog chain can be set up for another camera angle. In this way, jumping back and forth between these two dialog chains makes the sonic transition from one camera angle to another. The name checkerboarding comes from the way cue sheets used to be drawn, with the alternating sound files on each track. Figure 8.26 shows what checker-boarding looks like in Pro Tools.

Figure 8.26. Checkerboarding in Pro Tools. One character's dialogue uses two channels with distinct processing chains in order to assist in making transitions between camera angles.

ADR

When mixing ADR tracks with the production audio tracks, it will be necessary to maintain the same background ambience heard on the original tracks. Hopefully, the production sound mixer has recorded for each scene long stretches of ambience, or "room tone," that you can use as filler underneath the ADR tracks in order to make them sound more natural and related to the scenes.

If you do not use the same microphone when recording the ADR tracks that was used during filming , you'll most likely have to apply a certain amount of EQ to match the ADR track's timbre to the original. You might have to add reverb as well to match the space you see onscreen. Once completed, the ADR tracks should blend seamlessly with the original production audio so as not to draw attention to themselves . The background ambience should be consistent throughout the scene without any abrupt changes in level or tone.

Animation

As animation dialog is always recorded entirely in the studio, it will need more treatment than usual to make it sound like it fits within the scene. Reverb will typically be needed in order to make a dry dialog track sound like it was recorded in a room or at a certain location. Any change in an animated camera angle might result in the apparent change of its related audio track. As the dialog is always read straight into a microphone, making it sound as if a character has turned around, walked away, or is sitting across the room will require some EQ and other processing.

There is a scene in Monsters, Inc . in which the character Sully is standing in an empty closet in his bedroom trying to explain to the small child, Boo, why there are no monsters in the closet. When he walks forward out of the closet toward the bed, you can hear a change in the quality of his voice that really makes you believe he's actually in the room. The reality is that John Goodman recorded all those lines in a very neutral-sounding recording studio, standing in front of a microphone. The techniques used to achieve that subtle effect are what make great dialog mixing a true art form. Listen to that scene, and try to notice the acoustic clues that lead you to believe he is actually in the room. Then try figure out what techniques you might use to create that same effect.

How Loud?

How loud dialog is in a film or TV show is a very subjective thing. A good rule of thumb is to make sure that the average level of dialog that occurs during normal conversation is registering somewhere between -27dBFS and -22dBFS using a VU- or RMS-calibrated meter. This is equivalent to 78dBC to 83dBC on an SPL meter. This will leave plenty of headroom for "shouting matches" and explosive car chases that will exceed the reference, and will keep the signal-to-noise ratio acceptable. Again, this is only the average level of the dialog. Certain scenes and lines will register much louder and much softer in the course of a dynamic production. Also, don't be afraid to have passages of dialogue that are much quieter than the reference level. It all depends on what the scene calls for. It is, after all, drama. What you hear in a calibrated mixing room should correlate to what you see.

Any critical adjustment of each EQ or ambience should be done in the same studio environment in which the final mixdown will occur, or at least in a calibrated, high-quality mixing room. Many re-recording mix engineers prefer to have all dialog tracks delivered raw and unprocessed. This gives them the most flexibility during the final mixdown. If you are performing all of the editing and mixing duties yourself, processing dialog in a pre-mix or pre-dub session can save lots of time in the final mix. Be careful not to paint yourself into a corner by limiting your ability to make changes in the final mix. The director might want to make changes to elements that you have already pre-mixed. In this case, you will have to return to the original tracks to address this issue. Try to anticipate items that might change in the final mix and leave those isolated on their own tracks.

Mixing Foley

Foley tracks are tied to the screen. Wherever the action goes, there goes the foley panning. Pre-mixes destined for a 5.1 mix should be made in 5.1 Surround. You might have a separate pre-mix for moves, footsteps, and specifics in order to allow more control in the final dub.

The better the foley sounds and mixing are, the less they will be noticed, adding to the feel and vibe of the scene. Foley sounds should make the audience believe they're actually watching the scene unfolding before their eyes. It should help to suspend disbelief, allowing the audience to feel as if they are actually there. Crazy panning moves (footsteps coming from behind and panning across to the front, for example) can distract from the visual and should be used only when they serve the story or visual.

While most foley sounds will be confined to the front three speakers, effects applied to them to create ambience and space, such as reverb, can find their way into the surround speakers as well. Someone walking through a large space, such as train station, would create reverb that could envelop the listener using the surround channels if this was the desired effect.

NOTE

"MONSTERS, INC." FOLEY TRACK

This movie contains a fabulous example of top- notch foley recording available on the DVD release. Under the options, there is a choice to listen to the 5.1 sound effects and foley track by itself without any music or dialog. This is a fascinating exercise in perceiving the subtleties involved in creating a truly impressive foley track, and well worth the purchase.

Mixing Effects

Effects offer the greatest opportunity for creative panning in surround. As is typical of sci-fi movies these days, sound effects such as fly-bys, robots, lasers, and spaceships provide an opportunity for the sound designer to use the full palette of surround speakers to create enveloping and surreal soundscapes.

When used for dramatic effect, the surround channels can provide an unprecedented degree of envelopment when panning an object from behind the listener across the sound field to the front. This type of hard panning, however, should be used in moderation because overuse can become distracting and often exhausting for the listener. Audiences typically prefer a natural sound field.

Hard Effects

Hard effects, such car crashes, airplanes, explosions, and other singular sound events, benefit from a 5.1 Surround mix. As they are not occurring all the time, they can take advantage of the added dramatic effect of the surround channels.

Effects that have a large low-frequency content can be directed to the LFE channel to enhance their impact. For example, an explosion can have its low-frequency content directed to the subwoofer , where it will certainly be felt by the audience as well as heard. As the LFE channel in a theater (and in your mix room) is calibrated +10dBC higher than the others channels, sounds in the LFE channel have a large amount of headroom relative to the other channels. Using the available headroom will not affect the other channels in the system. This allows for a greater "punch" factor when sounds are directed to the LFE channel.

Ambience

Ambience elements, such as crickets , wind noise, rain, walla (background crowd noises, mumbling, etc.), traffic noises, and so on can take full advantage of the surround speakers. The subtlety of ambient sounds allow them to be used in surround speakers because they are not distracting and merely provide a sense of envelopment to the mix. Most ambient pre-dubs are 5.0, as they do not usually require the LFE channel.

Mixing Music

Music comes in several forms within a film or video production. Depending on its use, it can be mixed in a variety of ways. Sometimes music will transition from one form to another. For example, many times a soundtrack song will start off as an environmental sound within the scene, such as a jukebox or clock radio. Then, as the scene progresses, the music evolves into a full-blown soundtrack piece that is no longer a part of the scene and is mixed at full volume stereo, becoming the focus of the soundtrack. The transition from environmental to soundtrack can be a tricky one.

The Score

The score typically is mixed in one environment and does not transition. Usually, the score will be mixed to the left and right speakers in stereo. Sometimes composers will provide a 5.1 Surround mix of their music that has certain elements or ambience directed to the surround speakers in order to create a more enveloped musical texture.

The score's level may need to be automated so that when other elements that have priority are present, the score does not overshadow them. Conversely, when the emotional impact of the piece is served best by the score, its level might need to be raised to heighten that impact. Most composers will compose their music to function this way by design. When mixing, you might have to augment this design with subtle amounts of automation and fader moves.

Environmental, or Source, Music

Environmental music will always require processing in order to make it sound as if it is within the filmed scene. Typically, this requires band -passed filtering of a full-fidelity mix to mimic the response of a small speaker system such as a car radio or boom box. Additionally, reverb and a short delay might need to be added to position that sound within the space of the scene.

For instance, a live rock band playing inside a large club will require some amount of slap-back echo and reverb to make an audience believe that the music is being played inside a large room and over a large P. A. system. A typical studio recording of music is far too pristine to be believable in this context.

When small radios, car stereos, or even walkman-style personal music players are used within a scene, the sound coming from them will most likely need to be panned in order to follow the device onscreen. Usually, a mono source is preferable in these situations.

Most source music will be separated in the mix and on the music stem in case of last-minute changes due to artistic decisions or publishing rights problems. If a song needs to be replacedeven after the mix is completedyou can return to the stems and just replace that one song without much trouble.

Soundtrack Songs

Soundtrack songs should be heard in their full studio quality sound without any alteration of EQ, dynamics, or ambience. The classic example of this is the music used in the closing credits of a film. The only adjustment that should be made in this case is level. Dialog and other sounds might be present while a soundtrack song is playing, requiring adjustment. Those sounds still need to be heard above the song. It's all a judgment call by the mixer.

LFE Channel

The LFE channel is a powerful tool in the surround mixer's palette. Due to its +10dB calibration, a large amount of headroom is available for very dynamic and high-energy, low-frequency sounds. Most often this channel is used for hard effects such as airplanes, explosions, car crashes, earthquakes, space ships, and other such massive sounds. Typically, dialog, ambience, and music will not be routed to the LFE channel.

Keep in mind that when downmixing a 5.1 Surround mix to either Dolby Surround (Pro Logic) or stereo, the LFE channel is optional, and discarded by the downmixers in DVD players. This means that on certain systems, signals sent to the LFE channel will not be heard during playback when downmixing to other formats. Any "story vital " element sent to the LFE channel should be duplicated in one or more of the other speakers. This way, the essential aspects of the sounds will still be heard when downmixing, resulting in a pleasing mix. It is always advisable to preview downmixes in order to make any adjustments necessary. You may even manually create your own downmix and choose whether or not to include the LFE channel and to what degree.

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