Capturing Multiple Audio Channels

Whether you are capturing audio only or video and audio together, you need to choose which audio channels are captured and how they are grouped together. Final Cut Pro can simultaneously capture up to 24 audio channels to a QuickTime media file, from any of the available input channels of a single audio interface.

Setting Up for Capturing Multiple Audio Channels

Before you capture, you need to set up your audio interface with Final Cut Pro.

To select an audio interface for capturing audio
  1. Choose File > Log and Capture (or press Command-8).

  2. Click the Capture Settings tab.

  3. From the Capture/Input pop-up menu, choose a capture preset that contains the audio interface you want to use.

    If you have a third-party audio interface, you may need to create your own capture preset, or modify an existing one. For more information about customizing capture presets, see Capture Settings and Presets.

Multichannel Audio Channel Selection

The audio area of the Clip Settings tab allows you to select which audio channels you want to capture, and whether each channel is grouped in a stereo pair or treated as an independent mono channel. Each audio input control corresponds to an input on the audio device or interface determined by your current capture preset. If you are using a third-party audio interface, it is important that you know which output channels of your deck are connected to the input channels of your interface.

Video and Audio Channel Options

The Settings tab has the following options.

Figure. Clip Settings tab showing audio channel options.
  • Audio capture checkbox: Select this option to turn on audio capture for the current clip.
  • Preview: Select this option to listen to the incoming signal on the audio output selected in the Sound pane of System Preferences. Each audio channel you enable for capture is routed to a corresponding output on your audio interface, while disabled channels are not heard. If your audio interface has fewer audio outputs than the number of channels you are capturing, the audio is downmixed to two channels (mono channels are panned to the center and stereo pairs are previewed in stereo). This does not affect your captured media files; only the preview of audio during logging and capturing is affected.
  • Master Gain: This slider allows you to adjust the gain on all audio channels simultaneously. You can also enter a gain or attenuation value in decibels in the corresponding field.

    Note: Not all devices support a master gain control from Final Cut Pro.

Audio Options in the Clip Settings tab

The Clips Settings tab has the following audio options.

Figure. Clips Settings tab showing audio channel options.
  • Stereo/Mono control: Turning on this control tells Final Cut Pro to capture the two corresponding audio channels as a stereo pair. When this control is turned off, you can select one or both audio channels for capture. In this case, each channel is captured and handled as a discrete mono channel.
  • Capture Audio Channel control: Turning on this control tells Final Cut Pro to capture the corresponding audio channel.
  • Individual channel meter: Each audio channel meter shows the current level of the audio entering your audio interface.

    Note: If the Preview option is turned on, and an audio channel is disabled for capture, then the audio meter does not display levels.

  • Clipping indicator: Each audio channel meter has a clipping indicator that lights up when audio levels above 0 dBFS are encountered. This indicator stays lit until you stop and start playback again.

Choosing the Audio Channels to Capture

The following section describes how to choose the audio channels to capture.

To choose which audio channels to capture
  1. Make sure your audio interface is connected and selected in your current capture preset.

  2. Choose File > Log and Capture (or press Command-8).

  3. Click the Clip Settings tab.

  4. Check that the number of input audio channels in the Input Channels pop-up menu matches the number of channels available on your audio interface.

    Note: The audio interface used for capturing is determined by the currently selected capture preset. For more information about capture presets, see Capture Settings and Presets.

  5. Select which channels from your audio interface you want to capture.

    Important: When you select channels in the Clip Settings tab, you are selecting input channels on the audio interface, not on the video or audio deck itself. For easy and consistent audio capturing, you should connect the audio outputs on your deck to the input channels with the same numbers. For example, if you are capturing from a Digital Betacam deck, you should connect output channels 1–4 of the deck to input channels 1–4 of your audio interface.

  6. Click the Stereo/Mono control next to any pair of audio channels that you want to capture as a stereo pair, so it’s darkened.

    Figure. Clip Settings tab showing stereo and mono controls enabled and disabled.

Dual Mono Versus Stereo Audio

If you’re using a DV camcorder, you typically record two channels of audio during production. By default, DV camcorders use a built-in stereo microphone, with the left side recorded on audio channel 1 and the right side recorded on audio channel 2 of the tape. This is a stereo grouping, where channel 1 represents the sounds on the left side and channel 2 represents sounds on the right side.

Throughout the editing process, you edit both the left and right sides of a stereo sound at the same time. In this case, channels 1 and 2 are grouped together as a single stereo pair.

However, if you use separate microphones to record independent sounds, such as dialogue from two actors, you can capture each audio track so that it is independent (discrete) from the other. These are called dual mono tracks.

How Multichannel Audio Files Are Stored on Disk

Final Cut Pro stores multichannel audio media as QuickTime media files. Each audio channel captured is stored in its own track within a single QuickTime media file:

  • Mono grouping: Each mono channel is captured to its own track in the QuickTime media file.
  • Stereo grouping: Each stereo channel is captured to a single interleaved track in the QuickTime media file. A stereo interleaved audio track contains both left and right audio samples.

For example, suppose you are capturing from an eight-channel audio device. The way the audio is stored in QuickTime tracks depends on which channels you group as mono or stereo. Here is just one example of a track layout within a multichannel QuickTime media file:

Audio device channels
Audio grouping chosen in Clip Settings tab
QuickTime media file track
Channels 1 and 2
Stereo pair
1 (Stereo)
Channel 3
Mono
2 (Mono)
Channel 4
Mono
3 (Mono)
Channels 5 and 6
Stereo pair
4 (Stereo)
Channel 7
Mono
5 (Mono)
Channel 8
Mono
6 (Mono)

How Multichannel Audio Clips Appear in the Viewer

The order in which channels are grouped in the Viewer depends on the type of clip. A master clip displays audio channel groupings in the same order they are stored in the clip’s media file (unless the master clip was created from a sequence clip). Sequence clips’ audio channels display stereo pairs followed by mono channels, regardless of their order in the original media file or their order in the sequence.

For example, suppose you have a surround sound multichannel audio file that contains the following channel ordering: stereo, mono, mono, and stereo. When you import this audio file into Final Cut Pro, the master clip’s audio channels appear in the same order as the audio file. However, if you edit this clip into a sequence and then open the sequence clip in the Viewer, the channels will appear as stereo, stereo, mono, and mono because the stereo pairs are displayed first.

The Viewer has a separate tab for each stereo pair or mono clip item. The example below shows an eight-channel sequence clip open in the Viewer. The stereo pair is displayed first, followed by the mono clip items.

Figure. Viewer window showing multiple tabs for stereo pairs and mono clip items.

About Capturing Multiple Audio Channels from DV Devices

DV video devices can record up to four tracks of audio, depending on the sample rate and bit depth chosen on the camcorder. However, Final Cut Pro can only capture two audio channels via the FireWire port of a device at a time. You need to choose or create a capture preset that captures the DV audio channels you want. For more information about creating or modifying a capture preset, see Capture Settings and Presets.

To choose which DV audio channels to capture via FireWire
  1. Choose Final Cut Pro > Audio/Video Settings, then click the Capture Presets tab.

  2. Click a preset you want to modify, then click Edit or Duplicate.

  3. In QuickTime Audio Settings, choose DV Audio from the Device pop-up menu.

  4. Choose one of the following options from the Input pop-up menu:

    • If your DV tape sample rate is 48 kHz and 16 bit: First 2 channels
    • If your DV tape sample rate is 32 kHz and 12 bit: Choose either First 2 channels, Second 2 channels, or Mix 4 channels.

      The Mix 4 channels option mixes all four audio tracks into a single stereo pair.

  5. Click OK, then click OK again.

Important: Before you begin shooting, always set your DV camcorder to record with a sample rate of 48 kHz and a bit depth of 16.