Video preview thumbnail extraction issue

[Sitehand 1]

Hi 

I am not sure if this is the correct section to post this, but I have an issue with the Video Preview Thumbnail Extraction schedule task. I have just moved over to Emby and I have a library of movies and tv shows that I have turned on the thumbnail extraction on for. It has taken several days to extract the thumbnails using the default schedule task running to 4 hours a day.

But the issues I have run into, is that after the 4 hours that the schedule tasks runs for, it will cancel the current file that it is processing. I can see that in the log file

2025-08-21 06:00:00.096 Error ChapterImagesTask: Error creating thumbnails for /tvshows/Law & Order - Organized Crime/Season 04/Law & Order - Organized Crime - S04E08 - Sins of Our Fathers.mkv
	*** Error Report ***
	Version: 4.8.11.0
	Command line: /system/EmbyServer.dll -programdata /config -ffdetect /bin/ffdetect -ffmpeg /bin/ffmpeg -ffprobe /bin/ffprobe -ignore_vaapi_enabled_flag -restartexitcode 3
	Operating system: Linux version 3.10.108 (root@build6) (gcc version 12.2.0 (GCC) ) #69057 SMP Mon Jul 21 23:25:00 CST 2025
	Framework: .NET 6.0.36
	OS/Process: x64/x64
	Runtime: system/System.Private.CoreLib.dll
	Processor count: 4
	Data path: /config
	Application path: /system
	System.Threading.Tasks.TaskCanceledException: System.Threading.Tasks.TaskCanceledException: A task was canceled.
	   at Emby.ProcessRun.CoreProcess.CoreProcessLocal.WaitForExitAsync(CancellationToken cancellationToken)
	   at Emby.ProcessRun.Runners.ProcessRunnerBase.WaitForExitAsync(Int32 timeoutMs, CancellationToken cancellationToken)
	   at Emby.Server.MediaEncoding.ImageExtraction.ImageExtractorBase.RunExtraction(String inputPath, Nullable`1 container, MediaStream videoStream, Nullable`1 protocol, Nullable`1 streamIndex, Nullable`1 threedFormat, Nullable`1 startOffset, Nullable`1 interval, String targetDirectory, String targetFilename, Nullable`1 maxWidth, Boolean enableThumbnailFilter, CancellationToken cancellationToken)
	   at Emby.Providers.MediaInfo.ThumbnailGenerator.CreateThumbnailSet(Video item, MediaStream videoStream, LibraryOptions libraryOptions, Int32 width, CancellationToken cancellationToken)
	   at Emby.Providers.MediaInfo.ThumbnailGenerator.CreateThumbnailSets(Video item, MediaStream videoStream, LibraryOptions libraryOptions, CancellationToken cancellationToken)
	   at Emby.Providers.MediaInfo.ThumbnailGenerator.RefreshThumbnailImages(Video item, MediaStream videoStream, LibraryOptions libraryOptions, IDirectoryService directoryService, List`1 chapters, Boolean extractImages, Boolean saveChapters, CancellationToken cancellationToken)
	Source: System.Private.CoreLib
	TargetSite: Void ThrowForNonSuccess(System.Threading.Tasks.Task)

The next day it will start on the next movie or episode. Emby has now completed creating all the thumbnails. But the files that were being processed when the task was canceled are missing.

I have manually run the schedule task but it finishes without processing anything. I did see in another post that you are suppose to refresh the metadata on the item and it should create it. But the problem is how do you find all the files that are missing?

I understand that if there is error during the thumbnail extraction process that it emby wont want to try to endless reprocess the same video, but maybe if the task was cancelled the system to keep it in the list for the next schedule task to process it.

[Abobader 3464]

Hello Sitehand,

** This is an auto reply **

Please wait for someone from staff support or our members to reply to you.

It's recommended to provide more info, as it explain in this thread:

Thank you.

Emby Team

[Luke 42077]

Hi, yes I see the issue. It is interpreting the cancellation as failure, and therefore will not retry them. We'll resolve this for the next release.

Your workaround for now is to manually refresh metadata on impacted titles. Then the next time the task runs, it will try them again.

[Sitehand 1]

Thanks Luke

Is there a way to like when titles have been impacted or is only stored in the logs?

[Luke 42077]

Unfortunately no. One thing you could do temporarily is remove the time limit from the scheduled task and just let it go and get them all done.

[Sitehand 1]

It has actually already completed all that was left. I was hoping once it finished it would go back and get the ones it had skipped. I just dont know how many were skipped in the days before I realised that is was skipping them.

I guess I should be able to write a script of some sort outside emby to run over every video file and check if a bif files exists for it to get a list of missing ones.