Strange artifacts in green screen render.

[georgeisgettinupset]

Hello all,

I am having trouble identifying the source of some strange visual artifacts in a video I'm putting together with After Effects CS6 Ver 11.0.0.378.

For an example of the artifacts please skip to 29:22: cut-draft2.mov - Google Drive . See how the border around the video footage twitches?

At first I thought I did a poor job keying out the green screen. So I rendered a short clip to see if that was the case:  exampleclip.mov - Google Drive

... but the artifacts disappeared. No glitches to be seen.

So what is going on here? It seems like the long length of my video is causing After Effects to introduce the visual artifacts.

[Roei Tzoref]

CS6 Ver 11.0.0.378.

you are using a buggy version of this release. update to 11.0.4 - this could be or could not be related to your problem.

For an example of the artifacts please skip to 29:22: cut-draft2.mov - Google Drive . See how the border around the video footage twitches?

I am not seeing any problem at 29:22 maybe you can post a screenshot where to look.

[georgeisgettinupset]

Thanks Roei. I will upgrade, but I suspect that isn't the issue. Might as well try. Meanwhile, here are some screenshots. Going frame-by-frame through the video it looks like the glitches I noticed are actually the border of the keylight matte changing dimensions.

1. At 29:25 the matte shrinks for one frame:

You can see this if you compare it with the next frame:

Here's a video of example #1 where I overlay the two frames and toggle their visibility so you can see exactly how the matte changes: 2016-12-08_16-46-29.mp4 - Google Drive

2. At 29:36 the keylight matte border expands slighty for just one frame. You can see the grey halo around they guy's head:

And it's gone the next frame:

Here's a zoomed-in version of the glitchy frame from example #2:

Notice the grey border peeking out around his head and shoulders. That's my green screen after post-processing.

This glitch is occurring all over my 30 minute video. I wonder if it's the Quicktime file format?

[georgeisgettinupset]

I want to emphasize that this issue does not occur at all when I render out a short clip, and also add that locations of the glitchy frames change from video to video when I render out the full 30 minute version.

[Dave_LaRonde]

I doubt you do the whole thing in AE -- that would be a right royal pain.  What is your workflow like?  How are you getting your chroma key shots into an editing application?

If it's via Dynamic Link, you might try rendering out the clip in AE using a good codec, then importing into PP.

[georgeisgettinupset]

Hey Dave,

My workflow is: Premiere Pro --> After Effects

I first edited the audio, synced it to my video footage, and edited the best video clips in the correct order. The whole video is borken up into 12 sequences in Premiere. I then imported each sequence into After Effects--not vie Dynamic Link, but an actual import (perhaps the wrong way to do it). After that, I dropped all 12 sequences into one "key" composition.  I then keyed all 30 minutes of footage at once. Finally, I dropped the key composition into a "main" composition, in which I created all the motion graphics for the video.

I should add that I created a "final" composition too, and dropped the main composition into is. I had to cut a few sections out of the main composition and it was easier to just create yet another composition in After Effects and cut the main composition up, rather than make a cunt inside the main composition and resync all the motion graphics after the cut to the video footage.

Hope this makes sense. I know it's not a great workflow cause it is giving me headaches.

[Roei Tzoref]

how are you rendering this? try this - render a lossless version first - QT Animation. this is a long video so prepare ahead of time for a large enough disk space. 1 min of full frame video+graphics  = on average 5GB

now import your video file to Ae and see if you can recognize parts that are messy. if not - drag this footage to AME and render your encoded file.

[georgeisgettinupset]

Hello Roei,

That's a good idea. I'm rendering a plain h264 version this evening, but I may try rendering a lossless version if the codec change doesn't work...

But I'm now thinking it may be a problem with my workflow, not codec. Hopefully it isn't, because that means I may have to restructure my project. Ouch.

My old render settings were: Quicktime h264 at 75% quality.

This is the tutorial I used to create my key matte, fwiw: Advanced Green Screen Keying [After Effects Tutorial] - YouTube

[Roei Tzoref]

My old render settings were: Quicktime h264 at 75% quality.

Oh boy. you don't mean you render out of Ae in the Quicktime format and H.264 Format options do you? this is a buggy, poor quality codec you should NEVER use.

because you are using CS6 you chould use the H.264 Format right from After Effects. since you already had problems, I would skip this step and render a lossless version first because it will render much faster and you could test it before doing a long encoding process. in any case if you do want to encode directly from Ae cs6 you should do it through the H.264 Format like so:

but don't use this:

or use AME cs6- lauch it and add your Composition to it by opening the project file from AME

but as I said, to be on the safe side, you should render lossless and follow this rendering workflow:

1. render a lossless version in Ae: QT Animation

2. to test it, import it to AE, run through sections that were problematic.

3. if all is good - drag this footage to AME and encode your lossless through AME to an mp4 video file.

[Kevin-Monahan]

Hi georgeisgettinupset,

Did you solve this issue by following Roei's steps?

Thanks!
Kevin