Editing : Fades and Crossfades : Fades Dialog : Fade-In Shape Settings

Fade-In Shape Settings
The In Shape setting lets you define the shape of the fade-in to a clip for a fade, or to clip 2 for a crossfade.
Standard
Selects a single continuous fade curve. This creates a general-purpose fade that can be edited by dragging the curve itself.
S-Curve
Selects an S-shaped curve, which inverts its beginning and end characteristics. This makes it possible to fade in faster at the start of the curve, and slower at the end. S-shaped curves are useful with material that is difficult to fade effectively. S-curves can be edited by dragging the curve in the curve editor.
Preset Curves
Seven commonly used preset curves are provided for fast creation. These can be edited by dragging the end points of the curve in the curve editor portion of this dialog. The seven presets are as follows:
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Preset Curve 1 fades in at full volume immediately at the beginning of the fade and keeps it there throughout the fade.
 
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Preset Curve 2 fades in quickly in the beginning, reaching full amplitude fairly early in the fade.
 
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Preset Curve 4 fades in with a linear fade curve. This is the default curve.
 
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