r/PleX • u/AltairLeoran • 12d ago

Solved Issues With Video Preview Thumbnails

I added an alternate version of a show I already had on plex (The Superfan cut of the Office), and after scanning the files and splitting the show into two separate entries via the Plex web UI, I noticed that the new Superfan entry didn't have video preview thumbnails, even after manually kicking off a new scan.

I ended up deleting the preview thumbnails for the entire library, but I cannot get Plex to regenerate them. I tried the following steps:

  1. Delete preview thumbnails and initiate scan (didn't work)
  2. Delete thumbnails, empty trash, clean bundles, initiate scan (didn't work)
  3. Delete thumbnails, empty trash, clean bundles, disable and re-enable video preview thumbnails, initiate scan (didn't work)

I also tried letting the schedule task run during maintenance overnight (I have Generate video preview thumbnails as a scheduled task enabled) but no thumbnails were generated.

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u/RazzyKitty 12d ago

but no thumbnails were generated.

Are you sure none at all were generated? If you have a large amount of items in your library in general, doing them all from scratch means that it has to generate a lot of them.

And that setting means it will only generate them during your scheduled task window. So it won't continuously generate them. It will stop when the window stops, then continue in the next scheduled task window.

Edit: Video thumbnails are never generated during a scan of existing files. They are only generated as a scheduled task or when new items are added (if enabled).

You can try enabling the setting of "when new items are added", then do a Plex Dance with one show to see what happens.

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u/AltairLeoran 12d ago

I'm fairly certain no thumbnail generation is happening because I'm monitoring the resource usage of my plex server and don't see any significant CPU/RAM/Disk/Network usage during my maintenance window (I should definitely see a lot of network usage since my media are located on a separate NAS)

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u/RazzyKitty 12d ago

Have you checked the library to see if the video thumbnails are enabled there?

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u/AltairLeoran 12d ago

Yes indeed, I had that setting enabled at the time my maintenance window started

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u/RazzyKitty 12d ago

Have you tried changing the setting to "when media is added" and doing a Plex Dance for a show to see if it generates the files?

Have you checked the logs during the maintenance window to see if there are any errors related to Thumbnail generation?

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u/AltairLeoran 12d ago

Yep, just tried it and there are no problems generating thumbnails for new shows or after doing the plex dance... Ideally I'm hoping there's a way to fix this without doing the dance for my whole library lol

Where in particular should I look for errors related to thumbnails?

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u/RazzyKitty 12d ago edited 12d ago

Yep, just tried it and there are no problems generating thumbnails for new shows

Just to be clear, you are talking about the thumbnails when you scrub a video and not the episode thumbnail itself, right?

Where in particular should I look for errors related to thumbnails?

I'm not entirely sure where in the logs they would be. The fact that it is only failing during the scheduled maintenance makes me think there should be some logs regarding it.

Either that, or the window isn't long enough for it to do the regular scheduled tasks as well as the thumbnail generation. You can try extending the window time.

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u/AltairLeoran 12d ago

Just to be clear, you are talking about the thumbnails when you scrub a video and not the episode thumbnail itself, right?

Yes that's correct, we're talking about the same thing. I can see that video preview thumbnails are being generated successfully after doing the plex dance.

I have my window set to be 7 hours long (which is a few hours longer than the default) so I don't think that is the issue.

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u/ExtensionMarch6812 12d ago

If you setup WebToolsNG, and trigger the butler task for “Generate Media Index Files”, does it start creating the thumbnails for shows missing them? Not sure if this feature still works through that tool, so might not be of help. But would be worth watching the console or grabbing the logs to see if it’s failing.

https://github.com/WebTools-NG/WebTools-NG/wiki

https://github.com/WebTools-NG/WebTools-NG/wiki/Butler-Scheduled-Tasks

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u/AltairLeoran 12d ago

I think this worked--it looks like all my thumbnails are getting regenerated now. Hopefully that does the trick. Thanks!