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abnormally long render-times when using render multiple frames simultaneously on short sequence

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Xav VonLabnormally long render-times when using render multiple frames simultaneously on short sequence
by on Aug 27, 2014 at 12:26:33 pm

Hi,
I'm stuck with a painful AE behaviour, perhaps you guys will now a way out of this :

using render with multiple frames is MUCH slower than "normal" render or ram preview, regardless to the actual number of used CPUs/ram per CPU ratio.

I have a pretty heavy and complex AE 1080p project with multiple compositions in it (a 5-minuts-ish music video with approx 200 shots).

Working through the project is relatively smooth despite the couple of 8k environment maps and the gigs of rush but the final output takes AGES while the ram preview is pretty fast though.....

Heres' my rig :

cc 2014
hexa i7 OC'ed to 4.7 Ghz
64Gb Ram
1ssd for system, 1 ssd for project, 1 ssd for cache files

tests with different settings in the render multiple frames simultaneously pannel with this particular comp seem to have proven that ce cpus are not choking on a lack of available ram causing swap/time-loss (monitoring the RAM shows it never tops to 100% used)

So I took a 25 frames test sequence; most of the compositions in it have been pre-rendered to save processing time.

When I do a RAM preview in full resolution, final quality, it takes 5min10 to complete it (I'm not using render multiple frames simultaneously for ram preview).

When I do a render without multiple frames AE starts rendering right away and finishes in 4min40

When I launch a render with multiple frames activated using 12 cpus for the exact same sequence, things get stuck for about 22minutes with AE reading "saving project, 6%done....."
When he is done with this and actually starts rendering, he rushes towards the end in 2 minutes only.

forcing AE to use 6 cpus only : 14min40
forcing AE to use 2 cpus only : 12min44


The actual render time is obviously lower when more cpus are used but the "saving project part" is much longer, resulting in a crappy total render-time, as if the "saving part" was actually a phase when AE would try to find out wich cpu is supposed to do what : the more cpus the longer the process....
I wouldn't mind if I had to render one single long sequence, but I have 200+ short shots .... :/

Is there any way of optimizing this ?


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Dave LaRondeRe: abnormally long render-times when using render multiple frames simultaneously on short sequence
by on Aug 27, 2014 at 4:34:50 pm

Multiprocessing in AE has always been tricky to use, and the demands of the project may be better seved by turning it off entirely. That said, there are a few effects in AE that don't use multiprocessing AT ALL; sorry, but I don't have the list. That could be one of the problems.

But I have to tell you -- taking 5 minutes to render a 5-minute comp in AE is pretty darned fast! You should be happy!

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Xav VonLRe: abnormally long render-times when using render multiple frames simultaneously on short sequence
by on Aug 28, 2014 at 9:13:58 am

I must have been unclear :

my 5 to 22 minutes render-times are NOT for the whole 5min comp but for a 25 frames-long test-shot in which I have hidden most of the layers just to use it as a quick test.


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Kevin CampRe: abnormally long render-times when using render multiple frames simultaneously on short sequence
by on Aug 28, 2014 at 4:34:31 pm

you'll get long save times in projects that have lots of footage or image layers, and that can be a really killer for ae's 'render multiple frames simultaneously' option.

you may be able to reduce the project size by choosing file>remove unused footage, which will remove any files that are not used in any comps within the project.

or you can get more extreme by selecting the comp that you need to render, and choose file>reduce project, which will remove all comps and files that are used in the selected comp(s). obviously, you may want to save that off as a separate project after reducing it.

if you are using layered photoshop files with lots of layers, but only use a few of those layers, then you may still experience long save times, as it seems like ae still has to load the entire photoshop file just to get a few layers... i can't say this is true, but i have notice that projects that have used large photoshop files have often exhibited longer save times.

Kevin Camp
Art Director
KCPQ, KZJO & KRCW


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Lance MoodyRe: abnormally long render-times when using render multiple frames simultaneously on short sequence
by on Aug 29, 2014 at 1:32:02 am

What sort of footage?



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Walter SoykaRe: abnormally long render-times when using render multiple frames simultaneously on short sequence
by on Aug 29, 2014 at 1:29:16 pm

Quick note on how Ae's multiprocessing works: it saves a copy of your project, then multiple instances of the Ae renderer open that project, each within its own RAM space, and thus render multiple frames simultaneously.

As you note, there is a lot of overhead for starting up multiprocessing: saving the project, launching the background renderers, and then each instance opening the project -- all before a single frame is rendered.

For short renders, this overhead is not always worth it; it may be faster just to render a single frame at a time because this incurs no overhead.

For longer renders, though, the ability to render multiple frames at the same time usually eventually pays back the overhead of starting the multiprocessing render in the first place.

In other words, a 25 second render will probably not benefit from multiprocessing (especially if your apps and projects are not stored on SSD drives), but a 5 minute render will.

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


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Xav VonLRe: abnormally long render-times when using render multiple frames simultaneously on short sequence
by on Aug 31, 2014 at 4:21:46 pm

Thank you all for your inputs.

@ Lance : footages are mainly h0264 mov sequences from canon dslr's and 16bpc TIFF image sequences, no photoshop files in there as I already broke them down to separate TIFF's to avoid un-necessary layers.

@Walter, thanks for these details, this is how I feared it all worked so the "savin project" readings are a bit misleading as AE is doing more than that..... And I was hoping that there was a means to run through this overhead process only once and then keep on working more smoothly inside the same project once all the instances of AE.exe are launched etc but...no :(

So it's seems like I'm bound to render my collection of 200+ short shots on one single thread, not cool ! Especially as I don't have enough Vram for opening a secondary AE to keep wotking with the threads I have left while the single one is running.....


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Walter SoykaRe: abnormally long render-times when using render multiple frames simultaneously on short sequence
by on Aug 31, 2014 at 4:53:13 pm

[Xav VonL] "@Walter, thanks for these details, this is how I feared it all worked so the "savin project" readings are a bit misleading as AE is doing more than that....."

Hmm... the Info panel should show "Initializing background instances" separately from "Saving project."

How large is your AEP? Can you reduce it for render? What about splitting it up, maybe in quarters, to get AEP file size/save time down?


[Xav VonL] "Especially as I don't have enough Vram for opening a secondary AE to keep wotking with the threads I have left while the single one is running....."

You should check out Lloyd Alvarez's BG Renderer [link].

You could also use Ae's native Cache Work Area in Background feature [link] to render and cache comps (in a single thread) while you are working on other comps. Then your final outputs will be very speedy, even from a single threaded render, because Ae can grab the frames from the cache on your SSD instead of re-rendering them.

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


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