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I can't work out why some renders take longer than others?

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Benny StraceyI can't work out why some renders take longer than others?
by on Nov 22, 2009 at 10:31:19 am

Im running AE cs4 with a dual core Pentium 4, 512MB dedicated RAM and 3GB RAM

Ive configured the memory and multiprocessing section to allow multiprocessing to the maximum fast rendering setting.

On a quick side note, i have also configured my windows BOOT file to look like this:

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /NoExecute=OptIn /3GB

Adding the 3GB on the end allows AE to use the full 3GB rather than the standard 2GB even if you have 3GB of ram installed.

As you might be able to tell, i am after fast rendering times. I render out a lot of 3-6 min FLV videos.

Now last night after setting 14 comps in the render queue each of 6 mins length some took 10 mins and others took up to an hour!

settings were at the preset FLV -web medium which is at 600kbps and codec On2 VP6

I cant work out why some renders took a long time while others didn't. They were also all converted into the same file type and codec before importing into AE.


I have a feeling it could be because AE is not able to purge during the rendering, which sometimes lead to AE crashing for me when i do lots of renders.

I got this reply to another one of my posts just a few days ago, perhaps i could try this. But this seems a bit weird to me, having an "Easter egg" type option for a program ive paid hundreds for.

"Try this...

Enable "Secret" settings under EDIT/PREFERENCES. To do this:
- Hold down ALT+SHIFT while opening EDIT?PREFERENCES, select "General"
- In preferences dropdown, select "Secret"
- Check Disable Layer Cache and set to purge every 60 fames.

What this will do is purge the layer cache while rendering, not allowing you to overtax your system on multiple renders. I used to have the same issue as you and this resolved my problems.

Cheers, hope that helps!"

I have not been able to get this to work with cs4 tho.

I have also tried enabling the disk cache, but found that this slowed down rendering times. Maybe someone can also explain to me about the disk cache also.

Thank you, i hope i have provided too much info here lol.


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David JohnsonRe: I can't work out why some renders take longer than others?
by on Nov 22, 2009 at 2:05:55 pm

I'm not an IT guy so I won't get into system specs, but based on your core question, that is beside the point anyway. Simply put, renders take significantly different amounts of time becuase they're rendering different things. The length of a comp is in fact one of the factors that determines total render time, but it is only one of many factors ... and sometimes even one of the least significant.

It's important understand what rendering is doing ... it is creating entirely new images for every frame of a composition so the amount of time it takes is very dependent upon what each frame consists of.

In other words, if a 15 minute comp is comprised of only 360x240 raw video with only a couple text layers added in AE, it could conceivably render in a few seconds, but if a 15 second comp is comprised of 1080p raw video with numerous complex 3D layers, lights, masks, motion blur, effects/transitions, time-remapping, and/or keyed images, it could conceivably take many, many hours to render.

Similarly, two comps could have all of the same exact things listed above applied with the same exact settings, but if the images they are applied to are significantly different, the two comps could take drastically different amounts of time to render.

You might want to take a look at the "improving performance" section of the AE help for some tips to speed renders like reading from and writing to different drives and making sure those drives are of adequate I/O speed for your needs.


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Benny StraceyRe: I can't work out why some renders take longer than others?
by on Nov 23, 2009 at 6:43:27 am

No, there is something very wrong with AE.

Ive been doing some reading and tried everything.

The comps are exactly the same with the same raw video at 360x240 with only one text layer and that is it. The raw video is all imported into AE with the codec MPEG4 at 192kbps

I have watched the render take place and the first quarter of the comp goes very quickly and the estimated remaining time is around 3-5 mins, then it hits a point where every thing slows down a great deal and takes around 30 mins.

At this point in the comp there are no extra layers or complexed things going on in the raw video.

At first some comps took 10 mins then it went up to an hour, now my comps are going fast at first and then slowing down heaps.

I have the disk cache enabled with up to 3GB of storage space, AE memory usage is at 1.79GB while the RAM to leave for other programs is set at .25GB and i run AE with no other programs at the time.

I have found that when i turned on the multiprocessing that the render is slowed down from the very start.(so i have had this turned off) Prevent DLL address space fragmentation is also turned on.

Something very wrong is going on here and its very frustrating!


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Benny StraceyRe: I can't work out why some renders take longer than others?
by on Nov 23, 2009 at 9:51:03 am

Just to add more information to this, I have gone back to all the default settings that AE started with and i have also set my boot file back to 2GB instead of making it read 3GB of RAM for AE.

Im still getting the same results. I tested with 2 imported raw videos files, both with the codec MPEG4 320 X 240

I tried to render out the middle part of the video (the part at which AE slowed down) it was a minute in length. AE started to render very slowly right from the beginning. This took 9 mins to complete.

Next it went to the next comp that was next in the render queue. This comp was the full 6 min raw video file which was the exact same codec and size as the previous comp. This render completed in 12 mins.

A large difference considering the length of the comp, and still remember that these two videos consisted of the same type of raw video with no extra 3d layers or anything.

Ive done some reading on this and i have read a few times on from different sources about these type of codecs: Native HDV, MPEG1, MPEG2, mp4, H.261 or H.264 not being suitable for a consistent render in AE

But im using MPEG4, so unless im mistaken and MPEG4 is the same as mp4 i cannot work out what is going on with this issue.

While typing up this post, AE if now on the final comp in the render queue that i set up, this comp is still the same type and length raw file as the others and it is not even half way finished and has taken 12 mins already!!

i dont understand....


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Dave JohnsonRe: I can't work out why some renders take longer than others?
by on Nov 23, 2009 at 5:20:44 pm

I misunderstood your question since you never mentioned that you're rendering 14 identical comps and I thought 'why would someone render the same exact comp 14 times?' so I figured they must be different.

Yes, MP4 is one of the file extensions used for MPEG-4 encoded video so my guess is that the issues result from using MPEG encoded video as source material (see Dave LaRonde's stock answer #1).

BTW, just to clarify what I meant by this part ...

"Similarly, two comps could have all of the same exact things listed above applied with the same exact settings, but if the images they are applied to are significantly different, the two comps could take drastically different amounts of time to render."

I wasn't talking about video with different codecs or other tech specs ... I was reminding that even two videos with exactly the same codecs/specs won't necessarily render in the same amount of time since the images are different at every frame throughout and, therefore, the amount of time those images take to render will vary even with the same effects, etc. An extreme to make the point is applying all the same exact effects, masks, etc. to two source videos of identical lengths, codecs and all other specs with the only difference being that one video is of a colorful nature scene with lots of movement and the other is a static shot of a grey wall.


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Benny StraceyRe: I can't work out why some renders take longer than others?
by on Nov 24, 2009 at 3:30:12 am

Yes sorry, i guess i have made things a little confusing here in my last few posts. These videos weren't EXACTLY the same, but they were very close. And yes i can understand that with the different scenes and images between the two comps that would make a difference in rendering times, but im pretty sure it would not cause the significant slow down in render time i have been seeing.


Thank you for your help, i have been able to fix this issue by changing the video codec, however MPEG4 seemed to give me the best quality video output to import into AE. But this is whats causing all the slow down in render times!

I am using AVS video converter 6 and i changed all my files from FLV to H.263 MOV which actually made the quality worse.

These videos are for web videos and while the quality in the very end will come out a bit less, it can still come out a lot better than these videos encoded with H.263 will.

Can you recommend a codec that will be suitable with AE and for web videos and at least the same quality as MPEG4?

Or unless i can just convert the FLV videos i have back into FLV again, the FLVs that i am getting are not reading in AE CS4 due to not having these little pieces of video information at regular intervals, if i have described that correctly :)


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David JohnsonRe: I can't work out why some renders take longer than others?
by on Nov 24, 2009 at 12:35:23 pm

Personally, I never work with compressed video in AE and consider all of H263, H264, MP4, MP2, MP1, FLV, etc. to be output codecs. Now that I understand the issue your having clearly, I would say that using web-compressed video as your sources is what is causing the issues (see Dave LaRonde's "Stock Answer #1", which is available in many posts here and has a more detailed explanation as to why).

I typically work with QucikTime movies in AE ... either with any of the Uncompressed codecs or DV, although there are plenty of other suitable codecs for source material (AVI, etc.).


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