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

Lisa Brenneis

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  • Mixing and Finishing Audio

    This section covers all the ways you can adjust your audio clips' volume (levels), stereo pan position, and sound quality. You'll get a few tips on mixing and learn how to apply and tweak FCE's audio filters.

    Setting audio levels

    A sequence clip's levels and pan position are adjustable from several locations (Figure 12.37 ):

    Remember: Adjusting a sequence clip's levels or pan position in

    any of these locations will be reflected in the other locations.

    FCE Protocol: Measuring Digital Audio in Decibels (dB)

    Decibels (dB) is a unit of measurement for audio levels. Several decibel scales are used in the audio/video world (and some excellent technical articles on the Web explain them in detail). All of these scales describe amplitude as perceived by the human ear, but they measure different amplitude-tracking indicators. The scales all express amplitude in relationship to a fixed reference point, but different scales use different reference points. Professional analog audio uses a reference point of 0 dBVU and expresses dynamic range by adding

    headroom (range above 0 dBVU) plus

    signal to noise (the range from 0 dBVU down to the device's

    noise floor ). For instance, an analog audio device with a "signal-to-noise ratio" of 76 dB and 22 dB of headroom has a total dynamic range of 98 dB.

    Digital audio behaves differently and therefore requires a different structure for expressing dynamic range.

    There's no such thing as headroom in audio that's stored as binary numbers. Digital audio signal quality improves as levels approach 0 dBfs, but exceed the maximum level allowed by even a hair, and the audio levels are clipped.

    That's why the

    dBfs

    scale, the standard decibel scale used for digital audio, uses a reference point that corresponds to the

    highest value that can be expressed in a particular bit depth and calls that value 0 dBfs. The amplitude measurement of dBfs scales down from 0 dBfs to the lowest level that can be expressed at that bit depth. For example, 16-bit digital audio has a dynamic range of 0 dBfs (the maximum) to 96 dBfs (the smallest value). Greater bit depth increases digital signal processing resolution; FCE uses 32-bit floating-point resolution to compute audio mixes. Even with this increased accuracy, the dBfs scale still maintains the same maximum allowable level; the extra dynamic resolution accommodates the intermediate bit values generated by blending and processing multiple digital audio streams during the mixing process. The extended dynamic range (177 dBfs) of 32-bit resolution seems enormous, but it's necessary for accurate processing of 24-bit digital audio.

    Monitor levels and mixing

    It's important to keep your speaker levels constant when you adjust audio levels for a sequence. There's more than one place to adjust your monitoring level. Take a moment before you start working to set up everything, and note your settings so that you can recalibrate if necessary.

    If you'll be recording out to an external video deck or camera, check the audio output levels on the recording device's meters. Play the loudest section of your program. If your recording device has no meters, record a test of the loudest section and review the audio quality.

    Check your Macintosh's Sound preferences pane to make sure your computer's sound output level is set high enough (Figure 12.38 ). Next, set a comfortable listening level on the amplifier that drives your external speakers. Now you are in a position to make consistent volume adjustments to the audio in your sequence.

    Figure 12.38. The Macintosh's Sound preferences pane.

    [View full size image]

    Tip

    • There's no way to adjust computer audio levels within Final Cut Express. Instead, adjust your levels from your Mac's Sound preferences pane (see Figure 12.38).

    Adjusting levels and pan on the Audio tab

    The Audio tab is a good place to make fine level and pan adjustments, but you must open and adjust each clip separately. To make multiclip level and pan adjustments, use the Timeline level line overlays.

    To set audio clip levels on the Audio tab:

    1.

    Start with an open clip and the Viewer window selected.

    2.

    Do one of the following:

    • Drag the Level slider to the right to increase clip volume, or to the left to decrease clip volume (Figure 12.39 ).

      Figure 12.39. Dragging the Level slider to the right increases the clip volume.

    • Drag the pink Level line graph displayed over the audio waveform: dragging higher increases volume; dragging lower decreases volume (Figure 12.40 ).

      Figure 12.40. Dragging the Level line higher increases the volume.

    • Press Control-+ (plus) or Control- (minus) to adjust audio levels by single-decibel increments.

    • Choose Modify > Audio and make a gain selection from the submenu (Figure 12.41 ). Note that the submenu lists keyboard shortcuts for nudging audio levels.

      Figure 12.41. Choose Modify > Audio and make a gain selection from the submenu. Note the keyboard shortcuts listed to the right of the submenu choices.

    To create dynamic level changes within a clip:

    1.

    Start with an open clip and the Viewer window selected.

    2.

    Park the playhead where you want to start the level change (Figure 12.42 ).

    Figure 12.42. Move the playhead to the location where you want the level change to start.

    3.

    Adjust the level using the Level slider.

    4.

    Select the Pen tool from the Tool palette; then set a keyframe by clicking the level line with the Pen tool (Figure 12.43 ).

    Figure 12.43. Adjust the level with the Level slider and click the level line with the Pen tool to set a keyframe.

    5.

    Move the playhead to the next location where you want a change in the level.

    6.

    With the Pen tool, drag the level line to the new audio level (Figure 12.44 ).

    Figure 12.44. At the next location where you want a level change, use the Pen tool to drag the level line to the new level setting.

    Another keyframe is set automatically as you drag the level line with the Pen tool.

    Making multiclip adjustments" in Chapter 10.

  • Click the Set Keyframe button in the lower part of the window to set a keyframe on both the Level and Pan line graphs at the current playhead position.

    • Adjusting the pan position

    The pan position is the left/right placement of sound for single audio channels. Clips with one or two channels of discrete audio will initially open with pan set to the center.

    To set a pan position:

    1.

    Start with an open clip and the Viewer window selected.

    2.

    Do one of the following:

    • Drag the Pan slider to the right to pan toward the right; drag the slider to the left to pan toward the left (Figure 12.45 ).

      Figure 12.45. Dragging the Pan slider to the left pans your track toward the left channel.

    • Drag the purple Pan line graph displayed over the audio waveform. Drag higher to pan right; drag lower to pan left (Figure 12.46 ).

      Figure 12.46. Dragging the Pan line graph lower pans your track toward the left channel.

    • Choose Modify > Audio and make a pan selection from the submenu.

    Adjusting stereo spread

    On stereo audio clips, the Pan control adjusts the

    spread (the degree of stereo separation), and it adjusts left and right channels simultaneously and equally.

    You can use the Pan slider or line graph to adjust the stereo spread. The setting options on the Pan slider are as follows:

    • The base setting of 1 outputs the left audio channel to the left and the right audio channel to the right. This setting accurately reproduces the stereo mix of a track from a music CD.

    • A setting of 0 outputs the left and right audio channels equally to both sides.

    • A setting of +1 swaps the channels, outputting the left audio channel to the right and the right audio channel to the left.

    To adjust the pan on a stereo audio clip:

    1.

    Start with an open clip and the Viewer window selected.

    2.

    Do one of the following:

    • Drag the Pan slider to adjust the stereo pan positioning (Figure 12.47 ).

      Figure 12.47. The Pan slider at its base setting of 1. This setting replicates the original mix of a stereo source track.

    • Drag the purple Pan level line graph displayed over the audio waveform at the center line between the two stereo channels. Drag away from the center line for a +1 setting; drag toward the center for a 1 setting.

    Real-time audio level and pan adjustment

    Final Cut Express can record audio level and pan adjustments in real time.

    You perform keyframe recording on the Audio tab. Each individual clip must be opened on the Audio tab first, so real-time level and pan adjustment must be performed one clip at a time.

    You can freely mix and match real-time level adjustment on the Audio tab with manual tweaking of level and pan keyframes in the Timeline or on the Audio tab; they're just two means of achieving the same end: fine-tuning the dynamic level and pan information stored with each individual clip.

    To record audio level or pan keyframes in real time:

    1.

    Open the audio clip on the Viewer's Audio tab.

    2.

    Locate the point where you want to start recording audio keyframes and position the playhead a few seconds before your first planned move (Figure 12.48 ). You might want to loop playback of the section you're working on.

    Figure 12.48. Position the Timeline playhead a few seconds before your first planned fader move.

    3.

    Start playback.

    4.

    Position the pointer over the Level or Pan slider control and then press the mouse button to start recording keyframes (Figure 12.49 ). Drag the slider to the desired level, keeping the mouse button held down until you've completed your move; then release the mouse to stop recording keyframes.

    Figure 12.49. Drag the slider to the desired level, holding down the mouse button until you complete your move. If you want to maintain a steady audio level at the end of a move, release the mouse at the end of the move and then press, hold, and drag the mouse again when you want to perform your next move.

    Final Cut Express sets audio level keyframes that track your moves. These keyframed audio levels appear in the clip's audio level overlays in the Timeline and on the Audio tab of the Viewer (Figure 12.50 ).

    Figure 12.50. Audio level keyframes that track your mixer moves appear on the clip's audio level overlays in the Timeline.

    Tip

    • If you have already applied keyframes to sculpt a clip's audio levels, the new keyframes you just recorded will overwrite any previously applied keyframes.

    To delete all audio keyframes from a clip:

    1.

    In the Timeline, select the clip.

    2.

    Choose Edit > Remove Attributes; or press Command-Option-V.

    3.

    In the Remove Attributes dialog box, check Levels and/or Pan; then click OK.

    Or do this:

    1.

    In the Timeline, select the clip.

    2.

    Choose Modify > Levels; or press Command-Option-L.

    3.

    In the Gain Adjust dialog box, choose Absolute from the pop-up menu; then use the slider to set a clip volume, or enter a dB value indicated next to the slider (Figure 12.51 ).

    Figure 12.51. Use the Modify > Levels command to reset all selected clip levels to a specific decibel level in a single operation.

    The clip's level is set to the dB value you entered, and all level keyframes are removed from the clip.

    Tip

    • Both of these methods for resetting audio clip levels can be used on multiclip selections. Quick level resetting will surely save your sanity as you're trying to master the art of real-time audio mixing.