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Dragging playhead or clip introduces spurious frames into preview

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Joseph Francis
Dragging playhead or clip introduces spurious frames into preview
on Mar 24, 2019 at 1:08:48 am

Hi, I don't use AE very much, so this is sort of a newbie question, but

when I drag the play head around, or when I drag the clip itself around, I see a lot of single green dots get introduced to the cached fame green line, and when I play the clip, it seems to randomly display the beginning of the clip for a random length of time, as f inserted into the middle. Sometimes it just inserts the first frame from the clip. The scene is simple, just a minute long clip layer and a minute long audio VO narration track layer, and I'm sliding the clip against the audio to see what sync I want. When I see the weird bad frames, the audio marches forward undisturbed, so it's not like the whole thing is repeating. The clip seems to get mangled. If I step slowly through the clip the bad frames are still there. If I clear and rebuild the preview the problem persists.

Old computer core i7 PC from 2010 with 6 cores, 24 GB ram. I've triedpurging memory and cache and setting up cache on a new external Samsung T5 SSD. The footage is a .MOV from my iPhone, but I've tried replacing it with an equivalent sequence of individually number tiffs.

Everything starts out fine, but after a few minutes of basic sliding the clip forward or backward in time the trouble begins.


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Steve Bentley
Re: Dragging playhead or clip introduces spurious frames into preview
on Mar 24, 2019 at 8:27:46 pm

You didn't mention (unless i missed it) what codec the movies were in. If its something like H264 you might be hitting the "made up" frames that are inherently part of most types of compressed footage. Because you have skipped over the frames leading up to one of the made up frames, AE can have trouble resolving what that frame should look like.



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Joseph Francis
Re: Dragging playhead or clip introduces spurious frames into preview
on Mar 24, 2019 at 9:12:53 pm

The footage starts with a closeup of a wall and a hand enters frame holding an iPhone. The flash frames or repeated sequences consist of AE inserting that wall closeup into the middle of the clip several times over. Then the clip continues normally until the next random insertion. Sometimes a half second of hand entering frame gets randomly inserted. The more I move the play head or clip around, the more instances of seeing the blank wall or the hand entering frame occur. Even when the hand reenters frame, the audio (separate layer) proceeds normally. If I play the footage itself within AE (not the composition, but the footage itself) it’s garbled. If I play the footage outside of AE, using Windows media player, it’s normal, so AE is not changing the source footage, only it’s internal representation of it. If I reload the clip the problem persists.

I’m using this problem as a reason to buy a new computer. I hope my problem is old, inadequate hardware.


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Dave LaRonde
Re: Dragging playhead or clip introduces spurious frames into preview
on Mar 25, 2019 at 3:04:00 pm

A nine-year-old machine might no be up to the task, but before you give up on it, try transcoding the clip to a good intermediate codec like Quicktime Animation or a Cineform variety.

Sure, the file sizes will be bigger, but you have to remember that the original clip very probably has the bejeezus compressed out it and could be causing the problems in the first place.

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


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Joseph Francis
Re: Dragging playhead or clip introduces spurious frames into preview
on Mar 25, 2019 at 3:30:45 pm

I’ll give it a try. Thank you.

I did try converting the clip to a sequence of image.####.tif files and that didn’t improve the situation. The image sequence seemed to be less responsive to work with and also ended up being garbled with use. I think I’m asking too much if the single, old, slow HDD in which everything resides. I did try adding an external SSD into the mix but to not much help.


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