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Longer RAM Preview or Faster Rendering

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Sean WorsellLonger RAM Preview or Faster Rendering
by on Apr 22, 2009 at 6:46:37 pm

What are the implications of setting Longer RAM Preview versus Faster Rendering?

You'd think that the captions alone would be self-explanatory. A simple trade off between render times and playback duration within a composition. But I'm actually a bit confounded.

I've read over Adobe's explanation of these program preferences a few times. And it just makes it more confusing. Can anyone run down the basics for me? Because When I opt for "Longer RAM Preview" I see that the "System" specs change (watch the Tiotal After Effects memory usage change when you slide the Multiprocessing slider from Faster Rendering to Longer RAM Preview). Longer RAM Preview INCREASES the Total After Effects Memory Usage. But Faster Rendering decreases it.

This is worrisome, especially since sliding the lever towards Faster Rendering seems to SLOW down my render time in the Render Queue. If Total After Effects memory usage "decreases" with Faster Rendering options, this can't be a good thing can it?

Maybe I'm making too much of it. But I want to improve my rendering performance. I was getting errors until I increased the Minimum allocation per CPU up to the maximum. Now I just don't know what to do a bout the Longer RAM Preview versus Faster Rendering.


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Todd KoprivaRe: Longer RAM Preview or Faster Rendering
by on Apr 22, 2009 at 8:57:20 pm

I think that the part that you're missing is this:

When you are using Render Multiple Frames Simultaneously, the foreground instance of the application is _not_ involved in rendering. All that it's doing is collecting the rendered frames handed to it by the multiple background processes.

By sliding the Longer RAM Preview / Faster Rendering slider, you are either giving or taking away RAM for the foreground instance of the application. More RAM for that instance means that it can hold more frames for RAM preview; less RAM for that instance means that there's more RAM for the background instances that are actually doing the rendering, so they can actually do it faster. (Actually, the main reason that giving more RAM to the background processes tends to speed things up is that you're allocating enough RAM for more of those background processes to start and run.)

All systems and compositions are different, so there's no single right answer about these settings. If you're rendering something with huge frames and few effects, then you're going to make different decisions than if you're rendering small frames with lots of CPU-intensive effects. And so on. Experiment with the settings and use what works for your system and your current composition.

from the "Memory & Multiprocessing preferences" section of After Effects Help
"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.
...
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."

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Todd Kopriva, Adobe Systems Incorporated
putting the 'T' back in 'RTFM' : After Effects Help on the Web
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Sean WorsellRe: Longer RAM Preview or Faster Rendering
by on Apr 22, 2009 at 10:14:43 pm

Thank you. When you reveal that the foreground processes are NOT involved in rendering, that begins to help my understanding greatly. Rendering = background RAM.

So which direction on the slider allocates the most RAM to background processes?


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Todd KoprivaRe: Longer RAM Preview or Faster Rendering
by on Apr 23, 2009 at 2:30:01 am

> So which direction on the slider allocates the most RAM to background processes?

Faster Rendering

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Todd Kopriva, Adobe Systems Incorporated
putting the 'T' back in 'RTFM' : After Effects Help on the Web
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Sean WorsellRe: Longer RAM Preview or Faster Rendering
by on Apr 23, 2009 at 3:40:24 am

Thank you for clearing this up for me! I now have a much better understanding of what that slider does and why.


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Sean WorsellRe: Longer RAM Preview or Faster Rendering
by on Apr 23, 2009 at 6:11:30 pm

I was thinking more about this, and it struck me that the preference for Longer RAM Preview versus Faster Rendering is something you are going to then tweak a lot. Maybe even on the fly. Because you're tweaking it it adjust to specific compositions. Or when dealing with parts of compositions containing different effects. Or when you're rendering out a comp entirely, versus working on the comp. So it seems that this slider could be a window like "Audio" or "Tracker" that you can keep open and tweak as you like. Because putting it in Preferences like that suggests it's sort of a global preference that you leave alone once you've set it. Just a thought.


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