Join Todd Kopriva for an in-depth discussion in this video Using Render Multiple Frames Simultaneously, part of After Effects and Premiere Pro: Optimizing Performance (2011).
When you start a RAM preview or when you render for final export, After Effects can use multiple background processes, multiple instances of itself, to render multiple frames simultaneously. Let's look in the Preferences, Edit > Preferences > Memory and Multiprocessing. Whenever render multiple frames simultaneously is checked, whenever you begin RAM Preview or begin the process of rendering for final export, After Effects will start up background processes. Let's Click the details button to see more about those background processes. The foreground process, the process that actually collects all of the rendered frames together, and the process that also shows the graphical user interface is called After Effects.
The background processes are called ae self link. In here, we can see how much memory they need and how much memory they're currently using. Now because we're not currently rendering anything, ae self link is not using very much. By the way, if you ever need help troubleshooting Render Multiple Frames Simultaneously, you can Click copy and then paste the result into a Forum post on the Adobe After effects user-to-user forum, and we'll be able to help you more easily, because we'll know what your settings are.
I'll Click Ok to get out of this. Now let's look at some of these settings. Here, under Render Multiple Frames Simultaneously, we see that this computer has eight processor cores. Actually it has four physical cores, but with hyper threading each one of them appears as two to the operating system, for a total of eight. I reserved two CPU's for other applications, so that such things as my web browser and the recorder that I am using for recording this training don't have to compete with After Effects for resources.
I've said that each background CPU needs to have at least 2GB of RAM. I made this any smaller than if I used high definition or digital cinema sized frames, each of the processes wouldn't have enough memory to process the frames, so it would just shut down and not do anything at all. So, to prevent that from happening, make sure that you have this set to a high enough value for whatever you're working in. 0.75 is really only appropriate for web video size. 1GB for standard definition. 1.5 or 2GB for high definition, depending on such things as what kind of effects you're using.
And 3GB or even more for digital cinema. You can actually increase the values that are available in this menu, by changing a preference setting in a text preference file. I'll leave this at 2GB. So, with these settings the actual number of CPU's that will be used is 3. That's because I'm starting, as you can see here, with 9GB's available to After Effects. And I have 2GB's required for each of my processes. The foreground process actually takes slightly more than this. So, with the foreground process taking a little bit more than 2GB's, that leaves approximately 7GB's, and with 7GB's, with 2GB's divided into it, that leaves 3, 3 CPUs that can be used for the background rendering.
Note, this number right here does not refer to the total number or CPU's that will be used for after effects, just to the number of CPU's that will house their own background process each. By the way I recommend not make RAM reserved for other applications, any lower than about one quarter of you total installed RAM. The reason is that other software on your system, including the operating system itself needs RAM to work. So if you make this small, such as 1 or 2GB's, then whenever that other software needs RAM to work, you'll end up taking it away from After Effects, causing the contents of RAM that After Effects had been using to be swapped to disk.
Swapping to disk is a certain way to impair performance. You want to avoid that at all costs. So, having the set to 3GB prevents that from happening for me. If I were running something like Photoshop or other memory intensive programs, I'd set this to more like 4GB or 5GB. Let's Click OK to accept these settings. Then when I initiate a RAM preview, the first thing that happens is that the background processes start up, and load the projects. And because this is a somewhat large project, this takes a while.
And as soon as these projects have been loaded to into the background processes, the background processes will begin their rendering. And we'll see that in the intro panel, number of frames rendered at a time isn't 1 but is 3. So we go from 12 to 15 to 18 because we have 3 rendering processes going all at once. So, even though it took a little while for those processes to start up and load their projects, now that they're all working in paralell, the overall speed up is considerable. This is esspecially noticable when rendering for final export. And I'll just preview that little loop, and stop the preview. The key things to keep in mind when using Render Multiple Frames Simultaneously Multiprocessing is to make sure that you are leaving plenty of RAM for other applications, so that you don't end up with after effects and other applications fighting over the RAM and causing swapping to disk. And also that you make sure that you're giving each of your background processes enough RAM to work.
So that they don't start up, see that they don't have enough RAM to render a large frame, and they'll just shut back down without doing anything. There's not one set of settings that works for everyone or every composition and every computer system. Start with the defaults, and then experiment. Run a few tests on your own, and see what settings work best for you.
- Planning your work, updating, and auto-saving
- Learning and customizing keyboard shortcuts
- Optimizing hard disks and CPUs
- GPU: CUDA and OpenGL
- Using "Render Multiple Frames Simultaneously" multiprocessing
- Pre-rendering and proxies in After Effects
- Lowering resolution for previews