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Slow Render + Enormous File Size with Keylight
Slow Render + Enormous File Size with Keylight
by Alex Sedgwick on Aug 29, 2018 at 10:07:15 pm

Hey everyone,

I'm trying to render out a 30 minute green-screen scene with a small handful of effects applied (Keylight, Lumetri, Key Cleaner). Not only does After Effects spend days trying to render (about 80 hours estimated), but the output file is enormous. I've tried to remove all effects but Keylight, but this does not change anything.

Is there any way to render this in a shorter timeframe with a more reasonable file size?

Thanks in advance.

Re: Slow Render + Enormous File Size with Keylight
by Walter Soyka on Aug 30, 2018 at 9:49:52 am

[Alex Sedgwick] "Is there any way to render this in a shorter timeframe..."

Keylight can get pretty heavy. It'd be great to get a sense of your footage and computer specs for more understanding about the speed. A faster option might be to use the Ultra Key in Premiere Pro.

[Alex Sedgwick] "... with a more reasonable file size?"

Ae's default output module, Lossless, is totally uncompressed. To save disk space, you should use a compressed format. Personally, I'd recommend rendering to a high-quality "mezzanine codec" like ProRes, CineForm, or DNxHD/DNxHR.

For a few more details, see "Why is my output file huge, and why doesn't it play back smoothly in a media player?" here:

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]

Re: Slow Render + Enormous File Size with Keylight
by Andrew Somers on Aug 30, 2018 at 3:24:11 pm

Hi Alex,

Well this works out to be 6.6 seconds a frame, which for a green screen key doesn't sound too out of the ordinary if you are rendering one frame at a time and you have a lot of things going on in the comp.

But you haven';t told us *anything* about your project. Resolution? Bit depth? Colorspace? Output codec? Your system setup (number of cores, RAM, AE version, drive type, source file type).

All of these things have a huge affect on the render time.

THAT SAID, in a thread last week I was talking about how the newest versions of AE have a render speed issue due to the fact that they don't render multiple frames at the same time, If you have a big multi-core computer, you might notice that when rendering using the most recent versions of AE that your total CPU load is low.

Two ways around this: 1) get rendergarden which enables rendering multiple frames at a time. OR 2) download an easier version of AE such as 2014 which allows for multi frame render.

To handle rendering multiple frames at once, your system needs many cores and tons of RAM.

Output file: What do you mean by "enormous" ??? Without knowing your resolution, frame rate, bit depth, output codec, AND the size of the file you are seeing, I can't tell you if the size is reasonable or not.

How about you tell us some specifics??

Andrew Somers
VFX & Title Supervisor