Plex starts to transcodes in case of adding subtitles on large file, high bitrates. Bug?

Server Version#: 1.30.0.6486 - on ubuntu
Player Version#: Plex for LG, Client Version 5.52.3, Platform Version 7.20.0
Env#: An old notebook that hosts the server and a TV connected via ethernet.

I just understood why I cannot play UHD with high bitrates AND subtitles on the TV LG C2.

it seems it loads the CPU upto 100% when playing on the LG TV. When video is streamed to Chrome on Mac it is fine here is a screenshot of the load:
1st part is streaming on Chrome
2nd part when CPU starts peaking is when playing the same content but on the TV
3rd part removed the subtitles from and continuing streaming to the TV - load went down.

Can’t it stream any kind of subtitles locally, onlyyy :frowning: ?
Also smells like a bug inside the client, the app on the LG TV…

Thank you in advance,
Kaloyan

After further testing
Installed Plex Server on Windows
File: Black Adam 46GB file

Add subtitles from Plex option to search online - Plex Server starts to Transcode
Add subtitles .srt file in the same folder afterwards chosen from the menu - Plex Server starts to Transcode

Plex documentation say that SRT and few others are not burn in ( i.e. needs transcoding )

Supported Subtitle Formats

The following formats are fully supported either as embedded tracks or external subtitle files. Full support means they are compatible with all Plex Apps, including clients that require transcoded media.

  • SRT (.srt)
  • SMI (.smi)
  • SSA (or ASS) (.ssa or .ass)
  • WebVTT (.vtt)

Other formats such as VOBSUB, PGS, etc. may work on some Plex apps but not all. For the majority of apps, both VOBSUB and PGS subtitles will require the video to be transcoded to “burn in” the subtitles for streaming.

Now I see this as real bug, so please take a look at it.

Kaloyan

Plex server version: 1.30.2.6563 on Omen17 laptop
LG WebOs version: 03.34.55
Plex for LG version: 5.53.5 platform version: 6.3.2

The same for me.
If the media is 4K HDR and subtitles are external .ASS buffering takes place every 30 seconds making the video unwatchable.

If I convert the video from 10bit to 8bit by deleting HDR the same .SSA subtitles magically work again.

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