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.