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Strange horizontal glitches when rendering from After Effects

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Stephen DeLorme
Strange horizontal glitches when rendering from After Effects
on Jun 21, 2017 at 9:30:58 pm

One of the computers in my office is producing strange, horizontal artifacts when rendering from After Effects. They are usually only a couple of frames long but are nonetheless distracting, unexpected, and unacceptable.


Computer
MacPro (Mid 2010)
2 x 2.66 GHz 6-Core Intel Xeon
32GB 1333 MHz DDR3 ECC
AMD Radeon HD 7950 3072 MB
After Effects CC 2017


Render Location
The file is being rendered to a network drive on a robust NAS that we use to store our files. Both PCs and other Macs on the network successfully read from and write to this NAS on a daily basis, using After Effects as well as the rest of the Adobe creative suite. These glitches are ALSO apparent when rendering to a local SSD on this particular Mac, which is why I believe that the location being rendered to is NOT the issue.


Render Method
Glitches are apparent when rendering from AfterEffects. Formats and codecs tried include:
Quicktime ProRes422HQ
Quicktime Animation
Quicktime H.264

Problems also occur when rendering the AE composition through Adobe Media Encoder. The glitches are similar, but with the addition on even more artifacts in large, solid color areas. The format being used out of AME is H.264 in MP4 container with the High Bitrate preset.


Troubleshooting
Clearing the cache seems to have no effect. Also, I have run MemTest86+ in an overnight pass. This test came back with no errors, leading me to believe that the computer's RAM is OK.


Here is a link where one can view samples of what the glitch artifacts look like.
https://drive.google.com/drive/folders/0B4InlER4OhO-SlBnanJiZXNFM1k?usp=sha...

Sample from After Effects
The black bar at the top is a glitch -- it's something that happens elsewhere in he timeline.


Sample from Adobe Media Encoder
Similar to AE glitch, but also notice the artifacts in the solid blue areas in the bottom 2 images. I do not regard this as H.264 noises, as it moves very erratically. Also, in my experience, H.264 noise tends to be most evident in areas that have a lot of motion and not solid color areas.

I have submitted a bug report to Adobe, but the problem wastes a lot of time around the office. Any thoughts would be appreciated.

Thanks!


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Walter Soyka
Re: Strange horizontal glitches when rendering from After Effects
on Jun 22, 2017 at 10:08:31 am

Try this:

Open your Project Settings (Cmd+Opt+Shift+K). Under Video Rendering and Effects, choose Mercury Software Only. Click OK. Now go to Edit > Purge > All Memory & Disk Cache. Re-render. Do the glitches persist?

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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Stephen DeLorme
Re: Strange horizontal glitches when rendering from After Effects
on Jun 22, 2017 at 2:13:43 pm

I did check the project settings -- the renderer was already set to "Mercury Software Only" (as opposed to OpenCL). Just for the sake of trying, I did re-select it from the dropdown and click "OK". I then purged all Memory and Disk Cache.

This did fix the problem.

I am curious as to what would cause this sort of problem to spring up consistently. These sorts of glitches have been happening on this Mac in multiple After Effects projects for a variety of different clients. The user reports he has to clear the cache at least twice a week due to glitches like this. Funny thing is, After Effects CC 2014 on this same Mac runs without incident.

Any thoughts on what would cause this to happen so frequently?

Thanks for your time, Walter!


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Walter Soyka
Re: Strange horizontal glitches when rendering from After Effects
on Jun 22, 2017 at 2:30:23 pm

I can't see the videos or frame grabs you posted -- they require permission to view -- but your description of the artifacts was consistent with errors in GPU-based renders that I've seen in other applications.

After Effects has added GPU acceleration to select effects, starting in Ae CC 2015. My theory is that you're using a GPU-accelerated effect, and there's an issue with the GPU on that machine. (And perhaps the project had been previously set to OpenCL and still had cached frames saved?)

I haven't seen any issues with GPU-based rendering prior to yours, so I'm inclined to think it's something specific to that computer. This could be as simple as the card overheating. Open up the Mac and give it a good dusting (including the fans/heatsinks on that GPU). No tools other than a can of compressed air are required. Alternately, keep your projects in Software Only mode for that machine.

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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Stephen DeLorme
Re: Strange horizontal glitches when rendering from After Effects
on Jun 22, 2017 at 2:46:14 pm

Woops, sorry, didn't realize I had the security cranked up to high on that share link. It should be publicly accessible through this link now:
https://drive.google.com/drive/folders/0B4InlER4OhO-SlBnanJiZXNFM1k?usp=sha...

The project was definitely set to Mercury Software when I checked this morning. It's not a killer GPU, so we usually rely more on the CPU with this Mac.

That's interesting about the GPU accelerated effects though -- I will go through the effected project and take a tally of what effects are being used later today.

Thanks!


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