Adobe AFTER EFFECTS 5.5 Help Manual page 27

Adobe After Effects Help
Using Help | Contents
Changing the default duration of still images
When you add a still image to a composition, its default duration is the duration of the
composition. You can manually trim the duration of a still image and change the default
duration of still footage in the Import Preferences dialog box. See "Understanding
trimming" on page 81.
To change the default duration of still footage:
1 Choose Edit > Preferences > Import.
2 Under Still Footage, do one of the following, and then click OK:
Select Length of Composition: sets the same duration for the still image as the compo-
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sition into which it is placed.
Type numbers in the text box for the duration you want to use.
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Specifying interpretation rules
The Interpretation Rules.txt file describes how After Effects interprets field order, alpha
channel, frame rate, and pixel aspect ratio when importing footage. You can customize
this file in any text editor and add or delete entries, to save time. When you import, After
Effects reads the file and follows any applicable rules, as long as Interpretation Rules.txt is
stored in the same folder as the After Effects application. You can always override these
interpretations after importing. For more information, see "Using interpretation rules" on
page 27.
Using interpretation rules
You can automate how After Effects interprets different types of imported footage. For
example, each time you import a clip with unlabeled fields, you must specify the field
separation order. When you import dozens of clips, you can save time by using the Inter-
pretation Rules.txt file, which handles this for you.
The Interpretation Rules.txt file defines how After Effects identifies and matches footage
using parameters for frame dimensions, frame rates, file type, and codec. If it finds a match
for the footage you're importing, it then automatically sets the field order, frame rate,
alpha channel interpretation, and pixel aspect ratio.
Ordinarily, the After Effects Interpretation Rules.txt file is stored in the same location as the
application. You can modify this file to produce the custom rules file you need. Editing this
file is straightforward if you follow the samples listed in the file. However, the more
experience you have with scripting or related tasks, the more comfortable you'll feel
editing this file. You might make a backup copy of the file before changing the original as a
precaution.
When you edit the Interpretation Rules.txt file, you must supply a four-character file-type
code for each footage type or codec. If you don't know the file-type code for a file or codec
in a project, press Alt (Windows) or Option (Mac OS) as you select the file in the Project
window. The file's file-type code and codec code (if compressed) appear in the last line of
the file description at the top of the Project window.
Note: Any changes to the Interpretation Rules.txt file take effect the next time you open
After Effects. If After Effects is already open when you edit the rules, you must exit and
reopen the application to activate the new rules.
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