Delivering Audio

Because of the variety of ways that audio can be mixed into various multichannel configurations, there are numerous methods for delivering your program’s audio to the distributor or broadcaster. Programs that will be aired internationally have additional deliverables that must be taken into account. For more information, see:

What Type of Audio Mix Is Required?

There are several kinds of audio mixes you might produce for your program. Each type of mix must be output to tape differently, which means you’ll have different delivery requirements from various broadcasters depending on how your mix was done. Before you master your final tape, make sure to find out how your distributor wants the audio channels packaged.

The following sections describe typical mixes you might encounter.

Stereo

A stereo mix uses two channels (left and right) to create a directional sound field that can place audio cues anywhere along a virtual plane to the front of the listener. All Final Cut Studio applications that support audio mixing are capable of accommodating stereo audio, and virtually every program produced for television, theatrical distribution, and radio is delivered with at least a stereo soundtrack, even if the directionality of the sound field is not aggressively used.

Stereo mixes can be created easily in both Final Cut Pro and Soundtrack Pro and can be output to any tape format currently in use, encoded on a DVD, or included with a movie being delivered to the web.

5.1 Surround

Surround sound is a considerably more deluxe treatment for your program’s audio. The name 5.1 surround refers to the five audio channels (left, right, center, left surround, and right surround) that create a directional sound field in which audio cues may be spatially placed anywhere around the listener; the .1 refers to the low-frequency effects (LFE) channel that’s dedicated to the kind of sternum-vibrating rumbles frequently employed by explosions and other percussive sounds in action movies.

When appropriately mixed, surround sound is useful for more than creating dazzling audio effects sequences. Surround sound can open up the listener’s sound field to provide an immersive listening environment, even if the soundtrack consists of simple ambience, dialogue, and subtle sound design.

The most common surround sound formats are described below.

  • Dolby Digital (also called AC-3): A surround encoding format developed by Dolby Laboratories that contains up to six discrete audio channels. Although typically used to encode every channel of 5.1 surround, it can also be used to encode any subset of these channels. Compressor is capable of encoding any combination of up to five appropriately mixed audio channels plus a sixth LFE channel into a Dolby Digital audio file that you can use for authoring DVD Studio Pro projects. For more information, see the Compressor and DVD Studio Pro documentation.
  • Dolby EX: Another surround encoding format, designed to accommodate 5.1, 6.1, or 7.1 channels within the same bandwidth. Encoding any channels above 5.1 requires matrixing to fit an additional center channel and/or rear surround channel into the same data space. As a result, the additional channels are not discrete channels, and additional decoding hardware and speakers are required to make use of them.
  • Dolby E: A surround format that allows up to eight audio channels to be encoded as a digital stream that can be recorded onto an ordinary pair of audio tracks, enabling 5.1 surround mixes to be output to nearly any tape format capable of recording at least 16-bit audio. (6.1 and 7.1 mixes require the tape format to be capable of 20-bit recording.) Dolby E should not be played without being routed through an encoder. The encoded digital signal is not intelligible (at least, not to human ears) and may damage your audio equipment. Dolby E requires special equipment for encoding. However, once encoded, Dolby E audio tracks may be output to tape using Final Cut Studio the same as any other pair of audio tracks.
  • Digital Theater System (DTS): Another family of digital surround formats that compete with Dolby Digital. DTS requires third-party software for encoding (a Mac OS X–compatible encoder is available from DTS Digital Entertainment). Once encoded, DTS audio files can be imported by DVD Studio Pro (up to 6.1-channel surround sound is compatible) and used for DVD authoring. For more information, see the DVD Studio Pro documentation.

If you’re providing a surround mix for your program, there are a variety of ways that distributors may ask for it to be delivered.

  • Many broadcasters request that all of your surround channels be output discretely to a digital multitrack tape format. For example, DTRS-format decks are often recommended, including the Tascam DA-88 and DA-98, each of which records eight channels of audio with device controllable timecode that you can synchronize to your master videotape. Typically, a pair of synchronized stereo downmix channels is also output. When you provide the individual surround mix channels, the audio can be encoded into any format necessary.

  • If you’re delivering your video master on an HDCAM SR or D-5 tape, you may be requested to output all six discrete surround channels, plus stereo downmix channels, onto the tape master itself. HDCAM SR supports 12 audio channels, and D-5 supports 8 channels.

  • If you’re providing a Dolby E mix, distributors often ask for both stereo and surround mixes output to the same videotape master, because most professional videotape formats support at least four tracks of audio. For example, channels 1 and 2 would contain stereo left and right, and channels 3 and 4 would contain a pair of Dolby E–encoded surround tracks. A properly mixed surround mix can be downmixed easily into a stereo mix.

Left/Center/Right

This option can serve as a “poor filmmaker’s surround mix.” With proper mixing, the audible results of using three front channels (left, center, and right) can open up the listener’s sound field and provide a more immersive experience than stereo, without the extra work involved in creating a full-blown 5.1 surround mix. Using Compressor, you can easily encode a left/center/right mix into a Dolby Digital audio file for DVD authoring. If the three channels are properly mixed, you can use Final Cut Pro to downmix them into a stereo mix for tape output, using the audio outputs that can be assigned in the Timeline. For more information, see the Final Cut Pro documentation.

Alternative Audio Mixes for International Distribution

If you’re delivering a program for international distribution, there are several standard audio mix deliverables that will probably be requested.

  • Stems and music and effects mixes: Film distributors often require you to provide stems, or dialogue, effects, and music submixes output to separate stereo pairs of tracks. Television broadcasters usually ask for the original mix and a separate music and effects (M & E) mix without dialogue. (One exception is that documentary programs often leave the original interview dialogue in an M & E mix but omit voiceover.) For stereo or Dolby E–encoded programs being output to videotape, the original mix is usually recorded to audio tape channels 1 and 2, and the M & E mix is usually recorded to channels 3 and 4. These requests are to accommodate the overdubbing of dialogue into the native language of distribution territories for which dubbing is the norm. Ask the distributor or broadcaster how the various audio tracks should be mixed and organized, as delivery specifications vary.
  • Optional tracks: Some distributors also request optional tracks, to hold specific aural elements such as nonverbal vocalizations by the original actors that an international sound engineer may or may not want to use. Ask ahead for specific instructions, as delivery specifications vary.
  • Fully filled international tracks: Often, key production sound effects (for example, a door slamming or footsteps) occur underneath sections of dialogue. If you’re asked to provide “fully filled international tracks,” that means all sound effects lost when the dialogue tracks are isolated need to be re-created by recording Foley effects and doing additional sound design to “fill in the holes.”

Creating stems, M&E mixes, and fully filled international tracks generally involves good organization and some additional sound design. There are two specific features in Soundtrack Pro that can help you facilitate this process.

  • Submixes: Soundtrack Pro supports routing audio tracks to submixes. It’s a common practice to create separate submixes for dialogue, effects, and music, in order to simplify the final mixing process. Fortunately, this also makes it quite easy to output stems and M & E mixes.
  • Ambient noise addition and replacement: This feature helps you to fill in the “holes” created when you move dialogue into a separate set of tracks, by sampling sections of ambient noise from a scene (sometimes called room tone) that can then be used to automatically replace the missing audio. This is usually a first step that precedes additional sound design to place (or spot) sound effects and Foley sound over whatever was removed.

For more information about these features, see the Soundtrack Pro documentation.