Audio Parameter Behavior

Motion provides an easy and automated way for you to generate audio-driven animations in your projects, using the Audio Parameter behavior. Whereas other behaviors are applied to an object as a whole (usually modifying multiple parameters at once), a Parameter behavior is applied to an individual parameter of an object. The Audio Parameter behavior—available in the Parameter category in the Behaviors Library (and via the Add Behavior icon in the Toolbar)—lets you make a particle system pulse to the beat of music, or have an audio track’s bass amplitude affect an object’s opacity.

To apply an audio parameter behavior via the Add Behavior icon
  1. In the Audio tab or Media tab of the Project pane, select the track.

  2. In the Toolbar, click the Add Behavior icon, then choose Parameter > Audio from the pop-up menu.

    The Audio parameter behavior is added to the project. No Source Audio is yet applied, however.

  3. Do one of the following:

    • In the Behaviors tab in the Inspector, click the To pop-up menu (in the Source Audio row) and choose a source audio track.

    • Drag the audio clip (or video clip with audio) from the Media tab (in the Project pane) to the Source Audio well in the Behaviors tab of the Inspector.

To apply an audio parameter behavior via the shortcut menu
  1. In the Audio tab, select the track.

  2. In the Audio Track tab in the Inspector, control–click one of the audio parameters (such as Level), and choose Audio from the shortcut menu.

    The Audio parameter behavior is added to the project. No Source Audio is yet applied, however.

  3. Do one of the following:

    • In the Behaviors tab in the Inspector, click the To pop-up menu (in the Source Audio row) and choose a source audio track.

    • Drag the audio clip (or video clip with audio) from the Media tab (in the Project pane) to the Source Audio well in the Behaviors tab of the Inspector.

    For more information on applying parameter behaviors, see Applying Parameter Behaviors.

Audio

The Audio Parameter behavior performs an analysis of a specific property of an audio track, then applies an animation curve to a parameter based on that analysis.

Parameters in the Inspector
  • Source Audio: Sets the audio track from which to read audio data. Can be set to any single audio track in the project, or the Master track. Either drag an audio clip or a video clip with audio into the Source Audio well, or use the pop-up menu to choose a source for audio analysis.

    Note: In order for the Audio Parameter behavior to have an effect on an object, audio must be present in the Timeline at the position of the behavior.

  • Audio Graph: Displays a visual representation of the Source Audio data analyzed by the behavior per frame.
    Figure. Inspector tab showing Audio Graph.

    During playback initiated by the Play button beneath the Audio Graph, the selected Source Audio data is displayed. If audio analysis is being performed, progress is displayed in the Audio Graph area as shown below.

    Figure. Inspector tab showing Audio Graph being analyzed.

    The values of Low Frequency, High Frequency, Floor, and Ceiling can be set by dragging the small triangles along the bottom or right side of the graph, or set numerically using the four sliders underneath the graph to isolate certain frequencies and values for analysis.

  • Low Frequency: Sets the low frequency threshold of audio analysis. Only audio frequencies above this value will be analyzed. Values range from 1 Hz to 22,050 Hz.
  • High Frequency: Sets the high frequency threshold of audio analysis. Only audio frequencies below this value will be analyzed. Values range from 1 Hz to 22,050 Hz.
  • Floor: Sets the minimum value of audio input, below which results are ignored. Values range from 0 to 1.
  • Ceiling: Sets the maximum value of audio input, above which results are ignored. Values range from 0 to 1.
  • Smoothness: Sets the window size to smooth the result curve. Any value other than 0 triggers a keyframe reduction with an error tolerance of 1%. Values range from 0 to 10. This parameter is only available if Respond To is set to Amplitude.

    Note: Depending on your audio file, Smoothness values greater than 7 may result in audio playing out of sync.

  • Sensitivity: Sets the sensitivity of the transient detection. Values range from 0% to 100%. This parameter is only available if Respond To is set to Transients.
  • Attack: The amount of the offset in frames between the first keyframe of the curve and the peak of the curve generated by the Audio behavior. The number of frames that the curve takes to reach its peak from its initial value is called the Attack. This parameter is only available if Respond To is set to Transients.
    Figure. Keygrame graph showing the attack side of the curve.
  • Release: The amount of the offset in frames between the peak of the curve generated by the Audio behavior and the last keyframe of the curve. The number of frames that the curve takes to reach its final value from its peak is called the Release. This parameter is only available if Respond To is set to Transient.
  • Delay: Sets a delay in frames to offset the resulting keyframes.
  • Scale: Sets the scale factor to affect the result of the audio analysis.
HUD Controls

The HUD contains the Source Audio, Respond To, Graph Range, Audio Graph, Scale, and Apply To controls.