Voice activity analysis (for Auto Sync Subtitles) not working

Plex Media Server Desktops & Laptops
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1

Server Version#: 1.41.8.9834
Player Version#: 1.109.0.329-ea562b95

My subtitles aren’t auto-syncing. It used to work a long time ago, but now it’s not. Doing “Analyze” on any episode/movie finishes very quickly (under a second) and voice analysis doesn’t seem to work. All players have “Auto Sync Subtitles” checkbox grayed out.

If I go to “More Info” on any item that’ supposed to have it on, the “Has Voice Activity” field that’s supposed to be at the bottom is not there:

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Plex Dash shows it but as a blank box:

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I have the “Generate voice activity” setting enabled in the server settings and in the individual library advanced settings:
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Manually doing “Analyze” on items does nothing. I am using SRT files, downloaded through Plex from OpenSubtitles. Here are the debug logs when I do “Analyze” on any episode/movie:

Jun 03, 2025 16:13:20.139 [139894986742584] DEBUG - [Req#5d07] LongRunningJobManager [VoiceActivityDetection]: scheduling job for item 22954, 0 pending.
Jun 03, 2025 16:13:20.140 [139895045167928] DEBUG - Completed: [127.0.0.1:41102] 202 PUT /library/metadata/22954/voiceActivity?force=0&manual=1 (5 live) #5d07 GZIP 3ms 377 bytes (pipelined: 11)
Jun 03, 2025 16:13:20.142 [139894888332088] DEBUG - [Req#5d07/VoiceActivityDetectionManager] Running voice activity detection for 'The XXXX S01 E11' (id: 22954)
Jun 03, 2025 16:13:20.143 [139894888332088] DEBUG - [Req#5d07/VoiceActivityDetectionManager] Activity: registered new activity 36694eae-8943-466a-97d8-ab2259f953a5 - "Detecting Voice Activity"
Jun 03, 2025 16:13:20.143 [139894888332088] DEBUG - [Req#5d07/VoiceActivityDetectionManager] Activity: updated activity 36694eae-8943-466a-97d8-ab2259f953a5 - completed 99.0% - Detecting Voice Activity
Jun 03, 2025 16:13:20.143 [139894888332088] DEBUG - [Req#5d07/VoiceActivityDetectionManager] Activity: Ended activity 36694eae-8943-466a-97d8-ab2259f953a5.
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I’ve found that only media I’ve added to my server after turning on the option gets analyzed even though I have the setting turned on to “as a scheduled task and when new media is added”. Any media I have from before I turned it on is not analyzed.

3

Have exactly the same issue. If i manually analyze an item, I can see it complete in the logs, but it never actually does anything. Tried on several different files I have with the same result every time. I do not get any errors, but it just doesn’t work and all the files have hasVoiceActivity=“0” in the xml.

Has there been any solution to this?

4

An error related to this was fixed in the server 1.43.x branch.
Though it is not recommended to switch to this just yet, because it also brings a transcoder update which still needs a few wrinkles to be ironed out. Wait until the 1.43.x server is available in the public release channel.

I’ve found that the voice activity detection has problems in general recognizing Japanese in Anime.

1 Like
5

Thanks for the info. I gave the beta a quick spin but unfortunately it still doesn’t work even on version 1.43.0.10231. My media has audio tracks in either german, english or both and it doesn’t work on any of them.