Visual QuickStart Guide [Electronic resources] : Final Cut Express HD for Mac OS X نسخه متنی

FCE's Audio Formats

In the audio world,

format has entirely too many meanings.

There are media formats, such as DV, CD, and DAT, which describe the media used to record the original audio. There are also digital audio file formats, such as AIF, MP3, and WAV.

And then there are the audio formats discussed here, which describe the structure of multiple-channel audio recordings such as stereo or mono. These audio formats apply to audio captured with video, as well as to imported clips or audio-only clips captured with the Voice Over tool.

• Stereo: Both channels have been captured as a stereo pair. Stereo pairs are always linked, so anything applied to one track applies to both. Waveforms for the two channels that make up the stereo pair appear on a single Audio tab (Figure 12.1 ).

  
  

  Figure 12.1. The two audio channels that make up a stereo pair appear on a single Audio tab. Any adjustments made to one channel are automatically applied to both channels.

  
  

  
  

• Ch 1 + Ch 2: Both channels have been captured but are distinct and can be adjusted independently of one another. Two Mono Audio tabs appear in the Viewer (Figure 12.2 ).

  
  

  Figure 12.2. Ch 1 + Ch 2 audio format appears in the Viewer with two Audio tabs. Each channel is distinct and can be adjusted independently.

  
  

  
  

• Mono: The audio consists of a single mono channel, or both channels from the tape mixed into a single track. A single Audio tab appears in the Viewer. The source track designation (a1, a2, and so on) refers to the audio format of these tracks' source media at the time of capture.

Modifying audio channel formats

Two linked audio clips behave differently than two linked audio clips defined as a stereo pair.

• Two linked audio clips will be selected together, but their levels and filters must be controlled separately. Two linked audio clips can appear in two separate Audio tabs in the Viewer.

• Two audio clips defined as a stereo pair share everything except their audio content and their Timeline tracks. The two stereo channels appear on a single Audio tab in the Viewer, and they are always selected together. Any filter, panning, or level modification applied to one stereo channel is automatically applied to the other.

You can modify the audio format of captured audio using the Modify > Stereo Pair and Modify > Link commands. For example, toggling Stereo Pair off will convert a pair of clips captured as a stereo pair to two linked clips in A1 + A2 (Ch 1 + Ch 2) format.

Tip

Converting two single audio clips to form a stereo pair is a quick way to apply identical level changes to a couple of clips. You can always toggle stereo off after you have made your level adjustments.

To convert a stereo pair to A1 + A2 format:

Figure 12.3 ); then choose Modify > Stereo Pair to toggle stereo off.



Figure 12.3. Select the stereo audio clip in the Timeline; then choose Modify > Stereo Pair (or press Option-L) to toggle stereo off.







The stereo audio clip is converted to dual mono (Ch 1 + Ch 2) format, but the two audio channels remain linked (Figure 12.4 ). If you want to convert these to two completely independent audio clips, select the linked audio clips in the Timeline; then choose Modify > Link to toggle linking off.




Figure 12.4. The stereo audio clip converted to Ch 1 + Ch 2 format. Note that the small triangles indicating a stereo pair are gone, but the clip names remain underlined because the two audio channels remained linked.

Tips

Toggling stereo off will automatically unlink audio-only clips. FCE's Capture window captures only video+audio clips, and it always formats audio channels as a stereo pair. If you want your clip's audio to be formatted as A1 + A2 format, you'll need to select the two channels of your audio clip in the Timeline and then choose Modify > Stereo Pair to toggle stereo off.

To convert two audio clips to stereo pair format:

The Browser's audio format columns




You'll find four Browser columns devoted to information about the formatting of your audio clips (Figure 12.5 ); this summary will help you decode what each column tells you about your audio files.

• Tracks: The number of audio and video tracks used in a clip or sequence. Note the higher total number of tracks in the sequences.

• Audio: The audio clip's format as defined inside FCE. "A1 + A2" indicates the dual mono format.

• Aud Format: The audio format of the audio's source media file. The number (8, 12, 16, or 24) indicates the audio's bit depth. Note the 32-bit floating-point bit depth listed for sequences.

• Aud Rate: The sample rate of the audio's source media file.






Figure 12.5. Audio format information columns displayed in the Browser.




Chapter 19.

What's Bit Depth and Sampling Rate Got to Do with My Audio Quality?

FCE Protocol: Measuring Digital Audio in Decibels (dB)" later in this chapter.