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Rendering at Half Resolution causes memory errors more than Full Resolution!

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Nicholas SheraRendering at Half Resolution causes memory errors more than Full Resolution!
by on Nov 25, 2009 at 11:48:04 pm

I am trying to render out HD, virtual dolly shots which incorporate a lot of bluescreen footage. I have used Keylight for this.

I have an 8-core Mac Pro with 16 GB of ram. In the multiprocessor settings, I have specified that 4 GB should be left for other applications. This has worked well when rendering at Full Resolution -- that is, Activity Monitor shows the amount of Active Ram increasing until it stops when there's about 4 GB of unused ram remaining (including wired and inactive). Rendering continues without any problems for as long as I require.

However, keeping all multiprocessor settings identical, when rendering the exact same composition at Half Resolution, the Active Ram keeps on increasing until suddenly it drops right back to about 2 GB of usage and then the rendering becomes extremely slow. And then soon after that, an out-of-memory error message appears, sometimes in reference to Keylight. I tried using the secret preference, to purge after so many frames, but that doesn't seem to work.

So why are my memory settings being totally disregarded when I render at Half Resolution???


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Dave LaRondeRe: Rendering at Half Resolution causes memory errors more than Full Resolution!
by on Nov 25, 2009 at 11:57:22 pm

[Nicholas Shera] "So why are my memory settings being totally disregarded when I render at Half Resolution???"

There are two common culprits:
  • You have Open GL enabled for rendering. Turn it off. Turn it off NOW. It's useless.
  • The footage you used is giving AE fits. Read on:

Dave's Stock Answer #1:

If the footage you imported into AE is any kind of the following -- footage in an HDV acquisition codec, MPEG1, MPEG2, mp4, m2t, H.261 or H.264 -- you need to convert it to a different codec.

These kinds of footage use temporal, or interframe compression. They have keyframes at regular intervals, containing complete frame information. However, the frames in between do NOT have complete information. Interframe codecs toss out duplicated information.

In order to maintain peak rendering efficiency, AE needs complete information for each and every frame. But because these kinds of footage contain only partial information, AE freaks out, resulting in a wide variety of problems.


Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Nicholas SheraRe: Rendering at Half Resolution causes memory errors more than Full Resolution!
by on Nov 26, 2009 at 12:08:22 am

Wow, thanks for the quick reply!

Since I have OpenGL turned off, the problem must be because of the kind of footage I am using. It was recorded using the Sony XDCAM EX format, 1080p, 25p. What's more, I first used Premiere Pro to work out what clips I needed and trimmed them in there, before copying and pasting those clips directly into AE.



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