So for a long time this has always been an issue, the only player that actually can handle DVB Subtitles correct is VLC player.
To give an example.
Animal Planet Nordic sends out subtitles via DVB/TeleText
Selecting the subtitles will make plex liveTV crash/stop instantly.
If for some reason video says No video with supported format and MIME type found
Take url and remove space after .com https://streamable.com /5urcf
The problem is that the entire string from the variable is not split into piece before being served.
So it tries to show ,danish,swedish,norwegian,finnish at the same time which some players can handle and show it all at once giving a mess and hard time reading while other players like plex exoplayer(mod) crashes.
I reached out to exoplayer dev team, they do not seem to have enough devs to take care of this issue, I also gave them ideas from what VLC has created to fine polish subtitles after they are served, since they are showing up in big txt format, more that on the github link I provided.
I recorded a .ts stream from Animal planet that gives all info in the file to work with, I also extracted the media info for any plex dev to look at.
This is the media file (50mb which any can play via example vlc player)
Extracted via mediainfo
General
ID : 13 (0xD)
Complete name : C:\Users\Desktop\vlc-record-2020-06-02-15h46m05s-v50-.ts
Format : MPEG-TS
File size : 48.1 MiB
Duration : 25 s 662 ms
Overall bit rate mode : Variable
Overall bit rate : 15.6 Mb/s
Video
ID : 111 (0x6F)
Menu ID : 10101 (0x2775)
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4
Format settings : CABAC / 4 Ref Frames
Format settings, CABAC : Yes
Format settings, Reference frames : 4 frames
Codec ID : 27
Duration : 25 s 600 ms
Bit rate : 14.5 Mb/s
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate : 25.000 FPS
Standard : Component
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : MBAFF
Scan type, store method : Interleaved fields
Scan order : Top Field First
Bits/(Pixel*Frame) : 0.279
Stream size : 44.2 MiB (92%)
Language : English
Color range : Limited
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709
Audio
ID : 121 (0x79)
Menu ID : 10101 (0x2775)
Format : AC-3
Format/Info : Audio Coding 3
Commercial name : Dolby Digital
Codec ID : 6
Duration : 25 s 600 ms
Bit rate mode : Constant
Bit rate : 384 kb/s
Channel(s) : 6 channels
Channel layout : L R C LFE Ls Rs
Sampling rate : 48.0 kHz
Frame rate : 31.250 FPS (1536 SPF)
Compression mode : Lossy
Delay relative to video : -173 ms
Stream size : 1.17 MiB (2%)
Language : English
Service kind : Complete Main
Text #1
ID : 131 (0x83)-691
Menu ID : 10101 (0x2775)
Format : Teletext Subtitle
Language : Swedish
Text #2
ID : 131 (0x83)-692
Menu ID : 10101 (0x2775)
Format : Teletext Subtitle
Language : Norwegian
Text #3
ID : 131 (0x83)-693
Menu ID : 10101 (0x2775)
Format : Teletext Subtitle
Language : Danish
Text #4
ID : 131 (0x83)-694
Menu ID : 10101 (0x2775)
Format : Teletext Subtitle
Language : Finnish
