alass VS jellyfin-plugin-opensubtitles

Try alass or ffsubsync.

I use https://github.com/kaegi/alass to retime subtitles automatically. I've never worked with a file that has the issue you're describing but it does claim to fix frame rate issues.

You need an english softsubbed source, JP subs (kitsuneko), sync them with https://github.com/kaegi/alass, then set up POTPlayer for multiple subtitle files.

Check this project here: https://github.com/kaegi/alass

If you want subtitles for anime, kitsunekko usually has subtitles (and Netflix also usually has native subtitles and you can download them using subadub). The downside with using subtitles from a different source is you need to re-time them but tools like alass make this basically painless in most cases. For movies, Netflix or the DVD version of movies usually have subtitles.

I've used https://github.com/kaegi/alass and sometimes it works, sometimes it doesn't. It's not an easy problem to address automatically...

Video players wouldn't want that in their codebase, maybe if it was available as a C library.

With tools like alass[1] (using it to synchronise against the original language subtitles) it is about as close to solved you can get.

All of the attempts I've seen of using audio information to synchronise subtitles have been awful (some languages subtitle everything, even screams and incoherent shouts -- such as Japanese -- while others only subtitle dialogue and often rework dialogue for the purposes of making the subtitles short enough to be readable easily).

[1]: https://github.com/kaegi/alass

There is a fix for this here in this commit

When trying to download subtitles with the open subtitles plugin: https://github.com/jellyfin/jellyfin-plugin-opensubtitles

I use the opensubtitles plugin for anything that doesn't come with subs, mainly my blu-ray and dvd rips since converting the built-in subs to text based formats is so janky. Opensubtitles works great and always downloads in .srt format, which is the only format my Rokus support.

Jellyfin uses a C# plugin to download from open-subtitles and it seems to work very well.

So it will be mentioned in the release notes for each version, what the changes are. Ideally before you update, you should check the notes to see if there is any breaking changes to your setup. Or spend a bunch of time finding errors. The release notes will be found on: https://github.com/jellyfin/jellyfin-plugin-opensubtitles/releases (For this perticular one, it's mentioned in V11)

So appearently, the issue is solved in a newer version of the plugin only available to jellyfin version 10.8 (which is still in beta). See this GitHub Issue

Other notable changes can be found in the GitHub Release Changelog.

There's a PR open for a switch to their new API: https://github.com/jellyfin/jellyfin-plugin-opensubtitles/pull/54