Adobe After Effects CS4 - Manual (Page 675)

669 USING AFTER EFFECTS CS4
Expressions
Last updated 12/21/2009
Returns the width of the footage item, in pixels.
height Return type: Number.
Returns the height of the footage item, in pixels.
duration Return type: Number.
Returns the duration of the footage item, in seconds.
frameDuration Return type: Number.
Returns the duration of a frame in the footage item, in seconds.
pixelAspect Return type: Number.
Returns the pixel aspect ratio of the footage item.
name Return type: String.
Returns the name of the footage item as shown in the Project panel.
Layer Sub-objects attributes and methods (expression reference)
source Return type: Comp or Footage.
Returns the source Comp or source Footage object for the layer. Default time is adjusted to the time in the source.
Example:
source.layer(1).position
effect(name) Return type: Effect.
Argument type: name is a String.
After Effects finds the effect by its name in the Effect Controls panel. The name can be the default name or a user-
defined name. If multiple effects have the same name, the effect closest to the top of the Effect Controls panel is used.
Example:
effect("Fast Blur")("Blurriness")
effect(index) Return type: Effect.
Argument type: index is a Number.
After Effects finds the effect by its index in the Effect Controls panel, starting at 1 and counting from the top.
mask(name) Return type: Mask.
Argument type: name is a String.
The name can be the default name or a user-defined name. If multiple masks have the same name, the first (topmost)
mask is used. Example:
mask("Mask 1")
mask(index) Return type: Mask.
Argument type: index is a Number.
After Effects finds the mask by its index in the Timeline panel, starting at 1 and counting from the top.
Layer General attributes and methods (expression reference)
width Return type: Number.