Sound for picture IV: The audio post-production process

Contrary to popular belief, audio post-production should be a consideration long before the first scenes of a film are even shot. That is, choosing the best Production Sound Mixer you can afford within your budget will save you a small fortune in post-production once the locked cut has been produced. The Production Sound Mixer will head up the production mix team, who will be responsible for recording the live dialogue and will be your most important ally at this stage in the film’s production. The Production Sound Mixer will fulfil a variety of duties during the shoot and will be responsible for choosing the correct microphones for any given take, operating the sound recorder, maintaining the sound report, notifying the director of any sound-related problems, ensuring professional-quality recordings, watching for boom shadows, determining sound perspective and recording “room tone”, or ambient sound, with the sole objective of providing a clean, intelligible, professional sound track.

While the role of the Sound Production Mixer has remained largely unchanged as technology has developed, the delivery methods for audio recorded on location have advanced considerably. Before digital recording became as accessible as it is now, production sound reels would be sent to an audio post house every day for transfer into “dailies”, where that day’s select film takes would be synced with the audio track that corresponded to them.

More recently, productions are typically edited using digital production systems such as Apple’s Final Cut Pro or Avid’s Media Composer software and, as such, procedures have changed somewhat to accommodate this movement to a new technology. For example, it’s not unusual to find a video post house involved during shooting to Telecine selected takes if the production is being shot on film, allowing producers to use video production equipment to complete their film projects (the process at its most basic simply allows captured content to be viewed with standard video equipment or computers). In addition, dailies will be synced from the production medium – DAT, for example – onto some form of videotape for later digitising. By logging time code correctly from the production source recordings at this stage, the Edit Decision List (EDL) can accurately reflect the time code that was shot with the respective picture and allow automated reloading of production dailies.

Of course, if your production is being shot digitally, production audio will be loaded directly into a non-linear editing system (NLE) such as Final Cut Pro, Avid, Premiere and various others. Rather than a real-time transfer, this process is simply a matter of copying audio files (typically stereo WAV format) from a recording drive or DVD provided by the Production Sound Mixer to the NLE, where they can then be synced by the editing team.

In many cases, production sound is just one or two tracks, although many more tracks become available once working within the NLE. While this allows additional sound and mixing to occur in the NLE, many professional producers will opt to work with a dedicated audio production system such as Pro Tools|HD. The decision to utilise a dedicated Digital Audio Workstation (DAW) will largely be determined by the type of project – documentaries and less-complicated projects are typically prepared in the NLE by the picture editor, while narrative features, movies and projects requiring more advanced dialogue, music and effects work will be edited separately in a DAW such as Pro Tools.

Once the editor has synced the production audio in the NLE and the formal editing process has been carried out, the first full assembly of the picture is almost complete. Although small edits may happen here or there, the film is essentially arranged in its final format and is known as a ‘locked cut’. It is at this stage that the bulk of audio post-production begins – the film can be spotted for Foley effects and music, dialogue problems can be identified so that an ADR cue can be recorded, and the need for special effects can be determined.

It may be that your production audio, synced to picture within the NLE, contains several tracks of audio already – this can range from multiple tracks of dialogue arranged by the type and location of microphone used to ambient sound and spot mic-ing audio. Having looked at microphone types and applications in previous articles, it’s easy to see how an editor can quickly run out of audio tracks in the NLE. At this stage, many editors will opt to transfer their project to a dedicated audio environment so that it can be perfected by an audio post-production specialist.

The easiest way to transfer audio between applications is by means of an OMF export (picture and effects are not included in the export). This is the simplest, fastest and most efficient means of getting your audio into a DAW and ensures that your audio tracks are transferred accurately between the NLE and DAW. Unless you’re using Final Cut Pro or Avid systems for your picture editing, you’ll need to make sure that OMF Export is an inclusive feature of your NLE. It’s also worth noting that whilst Logic Pro supports OMF export straight out of the box, Pro Tools will require you to purchase an additional piece of software called DigiTranslator. As far as OMF Export options go, the following considerations should be made:

–   If you are able to select the type of OMF export, choose OMF Type 2.
–   Exports should be embedded so that the audio gets rendered into one large file.
–   The sample rate of your OMF export should match the sample rate of the NLE. This will typically be 48kHz.
–   When specifying handles for audio, values in the range of 300 frames should help to smooth everything out in the mix.
–   Remember that any effects (unless bounced down to the audio file) won’t be included in the export, so it’s best to leave this sort of processing to the DAW.

Since transferring OMF files to an audio post-production engineer is simply a matter of providing the resulting export file on a hard drive or DVD, post-production can happen at any location that meets the requirements of the project. Work can be carried out in a Pro Tools|HD facility for sample-accurate editing, ADR and Foley work, or at a Logic Pro facility, for example, if more creative soundscapes and soundtracks are required. It is during this session that premixing of audio recorded on location, in post-production, and material delivered by composers will take place. Depending on the project, premixing can take hours, days, weeks or even months for films intended for the big screen. Only once the audio elements are equalised and balanced in volume will effects such as reverb be added and the final output format be set – whether this is mono, stereo, 5.1 or 7.1. On large productions, various mixing tasks can be handled by a number of mixing engineers; for example, the lead mixer will handle dialogue and ADR, an effects mixer will take care of sound effects and Foley, and a third mixer will oversee music.

After the final mix has been approved, the resulting audio will be mixed with the correct number of channels, but it will not yet exist on the finished master tape or print. It is at this stage that the majority of projects will require a final step called Printmastering that combines several stems (or groups of submixes such as dialogue, effects, etc.) into a final composite soundtrack. This composite soundtrack is used to create an optical or digital sound track for feature film release print. For most television applications, a printmaster is typically not required and instead there must be a “layback” where the sound is recorded onto master tape.

At this stage, it is also common for a Music and Effects (M&E) track to be created. The M&E track includes all of the audio with the exception of any dialogue in the English language, so that foreign language versions of the project can be dubbed at a later date. In instances where English dialogue is recorded as part of the same audio waveform as ambient sounds, further Foley recording may be required to bring these sounds back into the mix.

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