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+--- Thread: Performance issue with subtitles (/t-performance-issue-with-subtitles)
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Performance issue with subtitles - ElFeo - 2025-04-10
So I just updated to the latest version of jellyfin - running on a Rpi 5. I hade no performance issues running movies/series including subs before the upgrade but now enabling subs makes the CPU go from 5-30% up to 100%. Setting subs to off and the CPU goes down to 5-30%. Are there any settings around subs I can try?
RE: Performance issue with subtitles - TheDreadPirate - 2025-04-10
What kind of subs and on which type of client?
RE: Performance issue with subtitles - ElFeo - 2025-04-11
Its the web client. The subs are "included" in the mkv-file (or is there some pluging to jellyfin finding subs?)
Edit: The client is a Macbook but the performance issue is on the Rpi 5 server
Edit2:
Server version 10.10.7
Web version 10.10.7
Build version 10.10.7
RE: Performance issue with subtitles - TheDreadPirate - 2025-04-11
But are the subs SRT subs or ASS? PGS?
Can you share your jellyfin log via privatebin.net?
RE: Performance issue with subtitles - ElFeo - 2025-04-11
The subs are "embedded" in the mkv file. So not sure what they are, it's not a separate file.
Which logs are you looking for? Seems like its one per day and then a bunch called FFmpeg in the beginning.
RE: Performance issue with subtitles - TheDreadPirate - 2025-04-11
log_20250411.log and any one of the logs named FFmpeg.Transcode at the beginning.
RE: Performance issue with subtitles - ElFeo - 2025-04-11
https://privatebin.net/?a0d809c9c4893b77#7FnzP5niBcxN19sQDHeboch77UGXciEP38kocQDF1ebD
https://privatebin.net/?d27f79c710265991#By2KMsfePwcbecLXbqVSjYmSdK7we4Fo2kL4ULqxL2B1
RE: Performance issue with subtitles - TheDreadPirate - 2025-04-12
They are PGS subs and they are being burned in, which requires transcoding. And the transcoding is being done on the CPU.
Code:
Stream mapping:
Stream #0:0 (h264) -> setparams:default (graph 0)
Stream #0:2 (pgssub) -> scale:default (graph 0)
overlay:default (graph 0) -> Stream #0:0 (libx264)
Stream #0:1 -> #0:1 (dts (dca) -> aac (libfdk_aac))There is an experimental setting in jellyfin-web to direct play PGS subs. Settings > Subtitles. Check "Experimental PGS subtitle rendering". From my experience with direct PGS rendering in a browser, the subs will sometimes de-sync briefly.
Your other option is to use Jellyfin Media Player, which has a much better playback engine.
RE: Performance issue with subtitles - ElFeo - 2025-04-12
Ok, thanks for figuring stuff out! Ill try the setting...
RE: Performance issue with subtitles - ElFeo - 2025-04-14
Interesting, just tried the client for Mac and that gives me the same amount of CPU-% as without subs. Maybe a bug in the web-client?