Apologies for a VERY noob question. Subtitles not shown.

[Yoji]

As I say in title, apologies for a very basic question.
How do subtitles actually work? which device is responsible for adding them to the picture?
The reason I ask, I have some downloaded videos, and they have embeded subtitles (I know this as I can select them and they work if I use VLC player)
If I look at the codecs of the file.. I can see the details e.g.
Stream 2
Codec: BD PGS subtitles (bdpg)
Language: English
Type: Subtitle
So if I watch the file on my PC, via the VLC player, I can select the subtitles, they show and all is good.
HOWEVER, I cant get the subtitles to play if I :
1. Play directly from my Synology NAS DS223 with "media server" to my old Samsung TV (UE50HU6900 ) - no subtitle options shown
2. Play via my NAS, through my Playstation 4 ... to the Samsung TV, on playstation the subtitle option is "off" with no alternative.
3. Play from my PC, via UMS to my Samsung TV
4. Play from my PC via UMS web player on my PC. (I expected this to work.. but could not find any subtitle options in the web player, they only show if it can find subtitles?)
I expect I could get it to work by using a fire stick into Samsung TV and using VLC app on the fire stick.. but not tested it.

I guess its the TV thats the problem.. but point 2 above, made me think its the playstation responsible for inserting the subtitles into the stream and the tv just shows what its told to show by the playstation?
So for point 4 above I was surprised... as I expected UMS to be fully up to date with latest subtitle techs, but that didnt work either (though I am no expert of the web player interface.. I could not find a subtitle option)
I using UMS 14.13..

As you can tell.. I am a complete noob on the details of how this actually works..
So could some kind soul elighten me... am I being totally unrealistic in my hopes that with all these options, I might get the subtitles to display?

Thanks in advance for your sage guidance.

[mik_s]

It depends on the device but if it supports subtitles and the video can be streamed it will display them and you will have an option to enable them on that device.

If the device does not support subs (or they are in an unsupported format) these have to be burned into the video by transcoding.
If the video format is not supported then will need transcoding anyway so the subs will have to be burned in.

There is an option in the conf to stream supported subs when transcoding so they can be enabled on the device instead of burning them in but might not work for many renderers.
This works on the PS4 for external text sub files but I had to add that setting myself.

PGS subtitles are very rarely supported on TVs so will most likely need to be burned in. This is because they are image based and usually for DVD or Blu-ray players.
If your video has these you can use an external subrip sub file which is text based and this will be sent to the device as an alternative.
You can get them from sites like opensubtitles.

It also depends on your setting when subtitles are used.
If they have the FORCED tag, usually for foreign language/alien parts, it should automatically enable them as long as that sub format is supported.
If not supported and the conf is correct UMS should be transcoding to burn them in.

You can choose what subs (and audio track) to use by playing from the #--TRANSCODE--# folder if you have it enabled.

For the web player I'm not sure if PGS subs will work and neither are external subs for technical reasons with the hls format it uses.
If you have videos that use this and want them playable with subs in the web player you may have to remux the file to add the text subs.
There are programs that can quickly do this without needing to transcode the whole video again. I think one was called MKVtools.

[Yoji]

Thanks,

Your description is a bit fuzzy, as you mention "It depends on the device", which device (in my scenario 2)? the NAS? the PS4? or the TV?
I thought I got it clear in my head by relating to (in UMS terms), the "device" = "renderer", but UMS shows my TV, PS4 and my NAS as renderers..so still not totally clear whats doing what.
But thinking about it.. and from your description of the "TRANSCODE" directory I guess it really does depend..
Using the TRANSCODE directory (as seen via the PS4) did work, I was able to select the VLC transcode stream, and subtitles appeared..
SO I guess selecting the stream in that directory was in effect telling UMS how to transcode the stream (I assume its not the PS4 doing the work?) . It was not perfect, as I just wanted subtitles, but it also included audio descriptions (e.g. things like "thunder in background") which I didnt really need, and could not find how to turn off so I ONLY got subtitles, but it small point, overall it works fine.
I dont seem to see the TRANSCODE directory in scenario 3 of my original post.. so not sure why that only appears for PS4 and not my TV, but may be a config file tweak needed there..
UPDATE: TRANSCODE directory IS there.. in UMS--> TV directly, and using one of the optional transcodes.. Subtitles work fine (not sure about audio description.. need do fuller test).

So I still have lots to learn... but will do some more tests and play around with it a bit more... see if I can improve/solidify my understanding.
Thanks again for your help..

[mik_s]

By device I mean the thing the video is playing on.
For example My F series Samsung TV and my PS4 don't support PGS subtitles so these need to be burned in.
If it had subrip subtitles they both support this so can be enabled directly on the renderer.

If subtitles are not supported and need to be burned in it is your computer running UMS doing the work.
As there is no way for the renderer to tell what subtitle to use UMS makes that decision depending on your settings or you have to pick the subtitles you want at the start from the transcode folder if not done automatically and cannot be changed half way though without restarting the video.
You will also need to pick the right audio track too as it could have many. All combinations of subs, audio, and transcoding engine should be available.

If you cannot see the #--TRANSCODE--# folder you can enable it in the settings. It should appear on all renderers.

Screenshot 2025-08-19 131921.png (22.55 KiB) Viewed 323067 times

If you always want subtitles on you can change the Audio/subtitles language priority: option.
The default is set depending on your system language but you could remove the eng,off; part so it is just "*,eng:eng,und" for example

Screenshot 2025-08-19 132803.png (14.25 KiB) Viewed 323067 times

[Yoji]

Thanks again...
I updated my post just as you posted your reply.
I updated my post to confirm that the TRANSCODE folder and options WERE available when going UMS -> Samsung TV directly..
Selecting the VLC option (same as I did with the PS4).. resulted in no compatible video at all.. which I thought strange since it did work with the PS4..
Selecting the FFmpeg option did produce a nice video stream with subtitles (not sure about audio descriptions.. will need recheck)..

My tests were not exhaustive, so I may have missed details, so I will recheck and be more thorough.
But I have a much improved understanding now, and am on the right track.
So wont take any more of your time with further silly questions.

Thanks again for your help.

[dylanfane8]

No worries, that’s actually a really good question — subtitles can be confusing!

So here’s the simple version: subtitles are just extra data stored inside the video file (like a text or image track). The player — not the TV or the NAS — is what reads that subtitle track and adds it to the picture before showing it on your screen. VLC does this perfectly because it knows how to decode and overlay almost any kind of subtitle, including PGS (Blu-ray style) ones.

Your other devices (the TV, PS4, and UMS web player) probably don’t support PGS subtitles. That format isn’t text-based — it’s actually little images — and many built-in players only support simpler formats like SRT. That’s why you see no subtitle option in those setups.

You’re right that using something like a Fire Stick running VLC or Kodi would fix it, because those apps handle PGS just like your computer does. Otherwise, you’d need to convert the PGS subtitles to SRT using a tool like Subtitle Edit or MKVToolNix (extract them, then OCR to text). After that, you could play the same file on pretty much any device and have subtitles show up fine.

So yeah, you’re not doing anything wrong — it’s just that most of your devices can’t handle that specific subtitle format.

[mik_s]

Sounds like another AI Bot account. Best to ignore it.