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Really slow render for time displacement filter

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John Hsu
Really slow render for time displacement filter
on Feb 3, 2013 at 5:38:36 pm

I'm getting really poor render times trying to output a video clip that has only one time displacement filter on it.

Originally I had multiprocessing on and the render time was 24 hours! A friend suggested taking off multiprocessing and it went down to 4 hours. I had to shut down the machine over night and when I came back and restarted the render it jumped back up to 46 hours to render 3 minutes of video as shown in the screen shot.

Here are my system specs:

Intel i7-3770 3.40GHz
16 MB RAM
120 GB Operating System Disk (C:)
1 TB Data Disk (D:)

The video is stuck at 3 minutes left and it's just an SD 640 x 480 clip.



I came across this thread:
http://forums.creativecow.net/thread/2/994293

And as I understand it the reason multiprocessing was running so slow was because there was a bottleneck at the hard disk trying to read and write at the same time. When I turned off multiprocessing the render time greatly improved, but now after restarting, the render time is even worse!

Any help would be greatly appreciated.

5367_screenshot232013120229pm.jpg.zip
5368_screenshot232013120340pm.jpg.zip
5369_screenshot232013120403pm.jpg.zip


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John Hsu
Re: Really slow render for time displacement filter
on Feb 3, 2013 at 6:37:05 pm

Perhaps I should add for the time displacement settings I have the offset set at 120 seconds and the resolution at 80 fps.


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Roland R. Kahlenberg
Re: Really slow render for time displacement filter
on Feb 3, 2013 at 7:29:41 pm

Your FPS resolution should be identical to your footage's FPS. Anything more will just add to the render time. A high Max Displacement value increases render time. The higher this value, the more frames AE has to calculate to get to the result. And this is for each frame that has to be rendered. So, do you really need to reach back or forward 120 seconds?

If you want to exaggerate the results without using high Max Displacement values then you should increase the contrast of your displacement layer.

HTH
RoRK

Intensive mocha & AE Training in Singapore and Other Dangerous Locations

Imagineer Systems (mocha) Certified Instructor
& Adobe After Effects ACE/ACI (version 7)


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John Hsu
Re: Really slow render for time displacement filter
on Feb 3, 2013 at 7:31:16 pm

Oops, uploaded the images as files by accident. Here they are as image links.





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John Hsu
Re: Really slow render for time displacement filter
on Feb 3, 2013 at 7:54:04 pm

Well, I stopped the render, and am ramping down the effect resolution to 30fps and the time displacement to 70 sec, I guess I'll see in 60 frames if that makes a difference or not.

Meanwhile I am a little foggy on understanding where the cache should be stored. Should I put it on my operating disk or data disk if I only have 2 disks.

Also, would getting a third drive to write output files to allow me to use multiprocessing?


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Roland R. Kahlenberg
Re: Really slow render for time displacement filter
on Feb 3, 2013 at 8:40:06 pm

[John Hsu] "Well, I stopped the render, and am ramping down the effect resolution to 30fps and the time displacement to 70 sec, I guess I'll see in 60 frames if that makes a difference or not."

I would further reduce the Max Displacement Time if it doesn't impinge on your design/expectations. A single frame preview should allow you to have a good idea of the displacement results.

I should add that setting the project to 16bpc or 32bpc will result in smoother displacements but with a longer render time.

[John Hsu] "Meanwhile I am a little foggy on understanding where the cache should be stored. Should I put it on my operating disk or data disk if I only have 2 disks."

In an ideal situation, your cache should be placed (a) on your fastest disk (b) at a physical location that is different from your source footage. The idea here is to not have a single disk perform read and write instructions as this will slow performance, greatly.

I have no idea which of your two disks is faster. Having said that, in your specific situation, where there is only one source footage and a lot of writing from RAM to disk cache (due to the Time DIsplacement effect having to read a lot of before and after frames, which I safely assume will very quickly max out your RAM), it may be a good idea to place the disk cache onto the same disk as the source footage IF the source footage is currently on your fastest drive.

[John Hsu] "Also, would getting a third drive to write output files to allow me to use multiprocessing?
"


AE is multi-threaded regardless if you have switched on Render Multiple Frames Simultaneously. IOW, multiple processors will be enabled regardless if RMFS is on/off. Further, there is a disconnect in your Q as you are addressing two separate issues.

Lots more info here.

HTH
RoRK

Intensive mocha & AE Training in Singapore and Other Dangerous Locations

Imagineer Systems (mocha) Certified Instructor
& Adobe After Effects ACE/ACI (version 7)


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John Hsu
Re: Really slow render for time displacement filter
on Feb 3, 2013 at 9:40:35 pm

Well it looks like ramping the effect down seems to have a good effect. At 70 sec displacement the render time dropped to 9 hours, and now I just turned it down even further to 40 sec and the render time has dropped to 2 hours!

Luckily this is just an experiment and I put an ease on the changes so the transitions look pretty good.

I had actually read through that page earlier, I guess I should be more specific by asking why does the render times take such a huge hit when turning on Render Multiple Frames Simultaneously. I assumed from thread that my problem might be that the disk drive was not reading & writing fast enough:
http://forums.creativecow.net/thread/2/994293#994301

I also forgot to mention that when I had RMFS on, in the rendering panel information drop down it would appear to hang up on the 'reading&writing' stage.

Maybe I should start a separate thread for this question?


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Roland R. Kahlenberg
Re: Really slow render for time displacement filter
on Feb 3, 2013 at 10:04:52 pm

[John Hsu] "I had actually read through that page earlier, I guess I should be more specific by asking why does the render times take such a huge hit when turning on Render Multiple Frames Simultaneously."

Your specific instance requires lots of caching to disk, as explained earlier. With RMFS switched on, you have multiple processors waiting in line to write and read to disk. IOW, with RMFS, you're creating a line of cars to pass through a single lane where traffic is frequently halted (due to caching to disk). In this case, switching off RMFS allows AE to handle the multiprocessing in a way where it doesn't overuse/abuse CPUs by having them wait for their turn to write/read cache files.

[John Hsu] "Maybe I should start a separate thread for this question?
"


One thread should be fine. By now you should have a better grasp with using the Time Displacement effect and how to optimize the settings for performance and temporal quality. You should also have a better idea of how multi-processing works and how to optimize your system under different project types.

HTH
RoRK

Intensive mocha & AE Training in Singapore and Other Dangerous Locations

Imagineer Systems (mocha) Certified Instructor
& Adobe After Effects ACE/ACI (version 7)


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John Hsu
Re: Really slow render for time displacement filter
on Feb 3, 2013 at 11:29:34 pm

Thanks for the help!


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Roland R. Kahlenberg
Re: Really slow render for time displacement filter
on Feb 4, 2013 at 1:50:24 am

You're most welcome John.

Cheers
RoRK

Intensive mocha & AE Training in Singapore and Other Dangerous Locations

Imagineer Systems (mocha) Certified Instructor
& Adobe After Effects ACE/ACI (version 7)


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