Memory & Multiprocessing preferences



Set memory and multiprocessing preferences by choosing Edit > Preferences > Memory & Multiprocessing (Windows) or After Effects > Preferences > Memory & Multiprocessing (Mac OS).

As you modify settings in the Memory & Multiprocessing dialog box, After Effects dynamically updates helpful text in the dialog box that reports how it will allocate and use memory and CPUs.

The RAM To Leave For Other Applications and Prevent DLL Address Space Fragmentation (Windows only) preferences are relevant whether or not Render Multiple Frames Simultaneously is selected. The settings in the Multiprocessing category are relevant only if Render Multiple Frames Simultaneously is selected.

RAM To Leave For Other Applications
Increase this value to leave more RAM available for applications other than After Effects. If you know that you will be using a specific application along with After Effects, check its system requirements and set this value to at least the minimum amount of RAM required for that application.

Prevent DLL Address Space Fragmentation
(Windows only) Select this option to give After Effects access to more contiguous memory on a computer with a large amount of RAM. This option may be incompatible with some display card (OpenGL) drivers, which can cause a crash when the application starts. If such a crash occurs, the option becomes unchecked automatically to prevent further crashes when you start After Effects.

Render multiple frames simultaneously

After Effects can start additional processes of the After Effects application to run in the background to assist the main foreground application with the rendering of frames for RAM previews or final output. These background processes have the name AfterFX.exe (Windows) or aeselflink (Mac OS).

In this form of multiprocessing, each background process renders its own frame and runs on a separate processor core (CPU). The number of processes used to render multiple frames simultaneously is never more than the number of processors. The number of background processes that can run on your computer also depends on the total amount of installed system RAM and the amount of RAM that is assigned to the After Effects application. The amount of RAM required for each background process varies depending on your system configuration; at least 1 GB per process is recommended. Optimum performance is achieved with computer systems with at least 2 GB of installed RAM per processor core.

If background processes are used for rendering, then the main foreground application is not used for rendering. Therefore, creating background processes only adds to the total number of processes used for rendering if enough resources are available for at least two background processes to run.

The background processes start when you close the Preferences dialog box after selecting the Render Multiple Frames Simultaneously option. The background processes continue running until the option is deselected.

Important: You may experience a small delay when the background processes start for the first time. A message in the Info panel indicates when the background processes are initializing. Deselecting Render Multiple Frame Simultaneously stops the background processes; reselecting the option causes the same delay when you close the dialog box.

Using the Render Multiple Frames Simultaneously multiprocessing feature does not speed up the rendering of all compositions. The rendering of some compositions is memory-intensive, such as when you are working with very large background plates that are several thousands of pixels tall and wide. The rendering of some compositions is bandwidth-intensive (I/O-intensive), such as when you are working with many source files, especially if they are not served by a fast, local, dedicated disk drive. The Render Multiple Frames Simultaneously multiprocessing feature works best at improving performance when the resource that is most exercised by the composition is CPU processing power, such as when applying a processor-intensive effect like a glow or blur.

Because antivirus software operates by monitoring every read and write operation, such software can decrease rendering speed, especially with the Render Multiple Frames Simultaneously preference selected.

Minimum Allocation Per CPU
Specifies the minimum amount of RAM that will be allocated to each background process, each of which runs on its own CPU (processor core). Setting this value lower can allow more CPUs to be used simultaneously with a limited amount of RAM. However, if you set this value too low for the kinds of frames that you are rendering, then the background processes will fail to render frames at all, and only the foreground process will be used to render frames. For example, you should not set this value to 0.5 GB if you are rendering frames with the pixel dimensions of high-definition television or digital cinema.
The optimum amount of RAM to allocate for each of the background processes varies according to project settings (such as color bit depth), composition settings (such as pixel dimensions of the composition frame), and what effects are applied. For a typical 8-bpc project with HDTV-sized compositions, at least 1 GB per background process is recommended. For a 32-bpc digital cinema project, at least 2 GB per background process is recommended. Start with these settings, but run some tests with your own computer systems and projects to determine the best settings for your specific needs.

Longer RAM Preview / Faster Rendering
The length of a RAM preview is determined by the number of frames that can be stored in the RAM cache. The RAM cache exists in the address space of the foreground After Effects process. By allocating more memory to the foreground After Effects process, less memory is allocated to the background processes. This allocation of memory to the foreground process can cause fewer background processes to be used to render multiple frames simultaneously, so there is a tradeoff between faster rendering and longer RAM previews. Drag the slider to adjust the memory allocation to a balance that suits your work and computer system.

CPUs To Leave For Other Applications
Set this value to a number other than 0 to prevent After Effects from using all of the CPUs (processor cores) in your computer system. For example, if you have a computer with 8 CPUs, setting this value to 2 leaves 6 CPUs for After Effects.

When After Effects temporarily disables multiprocessing with Render Multiple Frames Simultaneously

If After Effects can’t use background processes to render multiple frames simultaneously, a message appears in the Info panel and After Effects uses only the main foreground process to render all frames. These messages include the following:

  • “Incompatible composition. Multiprocessing is off.”

  • “Incompatible effect. Multiprocessing is off.”

  • “Incompatible preview mode. Multiprocessing is off.”

In general, the reasons for After Effects temporarily disabling the Render Multiple Frames Simultaneously multiprocessing feature fall into these categories:

  • The rendering of a single frame requires more RAM than is available to the individual background processes.

  • The project uses OpenGL for rendering of previews or final output. The Render Multiple Frames Simultaneously multiprocessing feature works by using background processes on multiple CPU processor cores to render frames, whereas rendering with OpenGL works by moving processing to the GPU. (See Render with OpenGL.)

  • The composition uses an effect that relies on GPU processing. These effects are generally effects implemented with Pixel Bender.

  • The composition contains a live Photoshop 3D layer. (See 3D object layers from Photoshop.)

  • The composition uses an effect with a temporal component that renders much more quickly when the rendering process has access to a cache of previous frames. These effects include some effects with a Temporal Smoothing option.

  • The composition uses an effect with a temporal component that requires frames to be rendered in strictly sequential order.

If a composition uses any of the following effects, the composition will not be rendered with the Render Multiple Frames Simultaneously multiprocessing feature:

  • Auto Color

  • Auto Contrast

  • Auto Levels

  • Cartoon

  • Lens Blur

  • Particle Playground

  • Shadow/Highlight

Note: Some third-party effects—such as CC Time Blend and RE:Vision Effects Video Gogh—are also incompatible with the Render Multiple Frames Simultaneously multiprocessing feature.