Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual page 41

After Effects on the Mac OS X operating system can use up to 3.5 GB of RAM. After Effects on 32-bit Windows
operating systems can use up to 3 GB of RAM; however, to use more than 2 GB in After Effects, you must configure
Windows appropriately. (See the Microsoft website for details.) After Effects on 64-bit Windows operating systems
can use up to 4 GB of RAM with no special configuration.
Note: These numbers are for each After Effects process. The background processes used to render multiple frames simul-
taneously can each use the amount of RAM mentioned above. (See "Render multiple frames simultaneously" on
page 36.)
Because video is typically compressed during encoding when you render to final output, you can't just multiply the
amount of memory required for a single frame by the frame rate and composition duration to determine the amount
of disk space needed to store your final output movie. However, such a calculation can give you a rough idea of the
maximum storage space you might need. For example, one second of uncompressed standard-definition 8-bpc video
requires approximately 40 megabytes (MB). A feature-length movie at that data rate would require more than 200
GB to store. Even with DV compression, which reduces file size to 3.6 MB per second of video, this translates to more
than 20 GB for a typical feature-length movie. It is not unusual for a feature-film project—with its higher color bit
depth and greater frame size—to require terabytes of storage for footage and rendered output movies.
RAM and disk caches
As you work on a composition, After Effects temporarily stores some rendered frames and source images in RAM,
so that previewing and editing can occur more quickly. After Effects does not cache frames that require little time to
render. Frames remain uncompressed in the cache. You can control how After Effects stores images by setting image-
caching preferences.
After Effects also caches at the footage and layer level for faster previews; layers that have been modified are rendered
during the preview, and unmodified layers are displayed from the cache.
Blue bars in the Timeline panel mark frames that are cached to disk. Green bars mark frames that are cached to RAM.
Choose Show Cache Indicators from the Timeline panel menu to turn the cache indicators on and off.
When the cache is full, any new frame added to the cache replaces a frame cached earlier. When you compile frames
for RAM previews, After Effects stops adding frames to the cache when the cache is full and begins playing only the
frames that could fit in the cache. The disk cache is not used for RAM previews. If disk caching is enabled, After
Effects can store rendered items to your hard disk when the RAM cache is full during standard previews.
The RAM cache and disk cache are automatically purged when you quit After Effects.
To purge the RAM cache and disk cache, choose Edit > Purge > Image Caches.
Memory & Cache preferences
Set memory and caching preferences by choosing Edit > Preferences > Memory & Cache (Windows) or After
Effects > Preferences > Memory & Cache (Mac OS).
Maximum Memory Usage
100% (where 100% equals the amount of physical RAM you have installed) because virtual memory uses hard-disk
space. Values over 200% are not recommended. The default value is 120%.
Maximum RAM Cache Size
value to greater than the default value of 60%, you may encounter problems such as decreased performance when
switching from one application to another or increased frequency of errors that say that After Effects is unable to
Sets the maximum amount of memory to use for any purpose. You can specify values over
Sets the maximum amount of installed RAM to use for cached frames. If you set this
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