Been using Plex for ages 2012 LG model with MediaLink and external .srt files for .mkv always worked.
After upgrading past 0.9.1116.958 (Plex Server) they stopped showing the external subs.
Option one: revert to 0.9.1116.958 and it will work.
Option two: install latest and go through the tedious task of making sure a few requirements are met. (Medialink will NOT show embedded subtitles)
Requirements:
* NO embedded subtitles allowed in the mkv file, as MediaLink seems to ignore external .srt files if embedded is present.
* Follow subtitle naming conventions. [filename].srt or [filename].[country ISO code].srt - I'd recommend the latter, as your subs will show up with correct language naming.
WhateverTheMovie.en.srt Will show as "English (SRT)"
WhateverTheMovie.srt will show as "Unknown (SRT)"
General tips:
Issue:
DTS, atleast for the 2012 LG models will not allow DTS (They claim a DTS license is needed, also for DTS passthrough) or rather it will make the PC transcode to downmixed stereo on-the-fly... assuming your PC/Nas is fast enough, you may not care. Still it's stereo, not surround.
Workaround:
Make sure you only have a AC3 (Dolby Digital) source in your .mkv file, as MediaLink cannot switch sound-stream and the DTS transcoding will likely end with jerky playback.
It's rather easy and quick to remux (make a new mkv container file with less items) hey, you are already trying to remove any embedded subtitles anyway, get rid of the DTS tracks and save some space. Win-Win.
MKV toolnix is the tool for you. https://www.bunkus.org/videotools/mkvtoolnix/
Bonus:
So you got a mkv and only got the DTS track in it? I got hold of a file where you can simply drag-and-drop your .mkv file and it will extract the .dts track, convert it to .ac3 and remux to a new mkv-file. (Your original file will remain unchanged, it will only convert the soundtrack, so video is unchanged aswell in the new file) this can be shared on request. (It consist of components from various open source tools ffmpeg etc and is fully automatic)
Note that it will only work for files with a single DTS track, remux it with mkvtoolnix to only include the sound track you need before handing it to the converter.
Bonus:
Which sub will MediaLink use when multiple files are present?
It does not care what preferred language you have defined on the server or which sub is actually chosen on a specific movie in Plex. Made some tests and it looks like it will use the first it finds alphabetically ordered.
Issue:
I remuxed/converted my file or added an external .srt - but it does not work.
Workaround:
Every single change you make to your file or external files will only get picked up by Plex when you choose your movie and via the "..." menu choose "Analyze" (You can however also find this when inside a plex library, the coq-wheel on the right, choose Analyse, note that "update library" button will do nothing is this regard)
Issue:
When you start a movie, it takes a while before it loads and most likely your TV will restart and the "signal strengt" icon does never reach "full".
Workaround:
Seen it quite a few times if your movies are on a drive that spins down. eg Green series disks, they take a while to spin-up. (You might actually hear it from your PC) and if its not ready within a specific time, MediaLink will timeout and TV will reboot. Usually it will work the 2nd time as the disk is now spinning.
I moved my content to a red series disk. (usually NAS disk, that never really spin down to idle) and the issue is as good as gone.
Feel free to correct me where I'm wrong.