Panasonic TV not displaying subtitles from USB stick

[millsy5]

Hi. I bought a Panasonic TX-55FX700B (4K LED display) TV little over a year ago so the TV is quite new. The TV inputs I use are a Sky box or USB. The TV displays the subtitles correctly when watching content from the Sky box (the subtitles are enabled on the Sky box via the Sky remote).

However my problem is with the USB. I'm watching avi files with hardcoded subtitles on a USB stick through one of the USB ports. But the subtitles are not displaying. I also have an LG TV and the subtitles display correctly using the same USB stick and avi videos. I wonder if there is a separate setting on my Panasonic TV to enable subtitles on the USB? Or maybe this is not supported? There is a subtitle button on the Panasonic remote but that does not help.

[usually_quiet]

Hi. I bought a Panasonic TX-55FX700B (4K LED display) TV little over a year ago so the TV is quite new. The TV inputs I use are a Sky box or USB. The TV displays the subtitles correctly when watching content from the Sky box (the subtitles are enabled on the Sky box via the Sky remote).

However my problem is with the USB. I'm watching avi files with hardcoded subtitles on a USB stick through one of the USB ports. But the subtitles are not displaying. I also have an LG TV and the subtitles display correctly using the same USB stick and avi videos. I wonder if there is a separate setting on my Panasonic TV to enable subtitles on the USB? Or maybe this is not supported? There is a subtitle button on the Panasonic remote but that does not help.

Are you sure that you have hardcoded subtitles? Hardcoded subtitles are a permanent part of the picture and cannot be turned off. If the section of the picture where they appear hasn't been cut off by zooming in using the TV's aspect ratio control, then they will always be visible. Soft subtitles or selectable subtitles can be turned on or off.

Your TV's manual states that only three soft subtitle formats are supported. These are MicroDVD (.srt), SubRip (.sub) or TMPlayer (.txt). The subtitle file must be in the same folder as the video file and have the same name as the video file. For example, a file called "myvideo.avi" would have a subtitle file called "myvideo.srt". If there is more than one type of subtitle file in the folder, the order of priority is .srt, .sub, and .txt.

[millsy5]

Sorry I must have my terminology incorrect when I said the subtitles are hardcoded. These avi video files do not have a separate srt file but 'encoded' into the avi. That's why I incorrect referred to them as hardcoded.

On the LG TV I can toggle the subtitles on and off. But on the Panasonic they are always off. Sounds like the Panasonic TV does not support subtitles 'encoded' into the file.

I understand srt files and the naming convention. Used them plenty of times watching videos on my laptop. I never got the subtitles to work on my LG TV on files that have the separate srt file. So I assumed they wouldn't work either on the Panasonic. I'll try that next time I have an avi which has a separate subtitle file.

[orsetto]

Interesting issue: I don't think I've ever encountered an AVI file with embedded optional (vs hardcoded) subs. Occasionally I come across files with incorrect file type extensions (.avi thats actually .mp4 or .mkv), with those changing the extension sometimes "activates" previously-invisible subs.

I've also noticed some TVs and BluRay players won't pick up and display the subs from freshly downloaded subtitle files on a USB stick, even if the same name as the video file and in the same folder. Very often this is caused by some random defect in the text formatting: if I open the problem sub in an editor like Subtitle Workshop and do a simple "Save As..." in the same format, the editor cleans the file of whatever problem prevents the TV or BD player from displaying it.

[aedipuss]

the avi spec doesn't have an option for encoding soft subs. some programs will put them in there anyway. not much if anything will play them though.

[millsy5]

I've also noticed some TVs and BluRay players won't pick up and display the subs from freshly downloaded subtitle files on a USB stick, even if the same name as the video file and in the same folder. Very often this is caused by some random defect in the text formatting: if I open the problem sub in an editor like Subtitle Workshop and do a simple "Save As..." in the same format, the editor cleans the file of whatever problem prevents the TV or BD player from displaying it.

I must try that. Never heard of Subtitle Workshop but I'll give it a go.

the avi spec doesn't have an option for encoding soft subs. some programs will put them in there anyway. not much if anything will play them though.

VLC player on my laptop and my LG TV play them fine. I wonder if there is a way to extract these encoded soft subs from the avi and save as a separate srt file, to later use with that avi on a TV that support srt files?

[orsetto]

I must try that. Never heard of Subtitle Workshop but I'll give it a go.

I should have been more clear: when attempting this solution, theres a bit more to it than just "Open" and "Save As".

Open the problem subtitle (CTRL+O or "Load Title" under File Menu), then tell Subtitle Workshop to find and repair all issues. Do this by invoking the "Information & Errors" function (CNTRL+I, or under "Tools" menu). A window will open with a list of issues the app thinks are wrong with the file: don't be alarmed if there are hundreds or even over 1000. Press the "Fix" button to repair all these issues. It might take two or three presses, with the list growing shorter each time. Usually by the third press the list shows 0 issues remaining, but one or two may persist like "line length too long": you can ignore those and press "OK" to exit the Errors display.

Proceed to "Save As..." (CNTRL+SHIFT+S) or under File Menu), a list with many format choices appears. Choose "SubRip" and the sub will be saved in the plain .srt format preferred by most TVs and some players for external sub files. Be sure to choose "Save As" so the app either overwrites the original file or creates a new one: if you just do a normal "Save" some hidden errors might remain that prevent the TV from recognizing it. The app is extremely quick: this whole process takes about 10 seconds from start to finish.

BTW, by default Subtitle Workshop flags Hearing Impaired info as errors and removes them (character [NAMES] and descriptors like [EERIE MUSIC PLAYING]. If you want to retain hearing impaired info, before pressing the "Fix" button press the "Settings" button, under the "Fix" tab deselect the "Hearing Impaired" checkbox.

VLC player on my laptop and my LG TV play them fine. I wonder if there is a way to extract these encoded soft subs from the avi and save as a separate srt file, to later use with that avi on a TV that support srt files?

From years-long habit, most of my downloads are done to an old Apple Macintosh that acts as an additional firewall of sorts. Then usually I transfer them to Windows PC for any cleanups or editing. I do keep some useful tools on the old Mac for pre-editing: on that platform I use the old MKVtools app to easily extract embedded subs from a video file. The app is cross platform but was long since updated into MKVToolNix for modern Windows 7 & 10 PCs. Despite the name, it opens .avi, .mp4 and .m4v along with .mkv files (at least the old MKVtools does). Additional similar extraction tools are available from the VideoHelp software library: search for "subtitle extraction" suggestions.

the avi spec doesn't have an option for encoding soft subs. some programs will put them in there anyway. not much if anything will play them though.

I've never encountered a .avi file with selectable subs, AFAIK it wasn't even possible until I saw this thread. Out of curiosity I just searched the topic ".avi with soft-coded subs" and got a couple ancient hits from the VH archives: seems it was a known hack during the divx era. Tho even back then, they were problematic and definitely not standard: no surprise most TVs and standalone hardware players today won't recognize internal soft subs in .avi files, only coordinating external sub files.

https://forum.videohelp.com/threads/328425-How-to-Get-an-avi-file-with-Soft-Coded-%28O...f%29-Subtitles

[jagabo]

First, use MediaInfo to verify the container (likely MP4 or MKV). It's probably not AVI. Change the extension to match the true container. MediaInfo will also identify the subtitle type. You will need to know that in order to deal with them. Put MediaInto into View -> Text mode. Copy the text and paste it in a post here.

The media players built into TVs usually can't handle embedded soft subs.

[millsy5]

First, use MediaInfo to verify the container (likely MP4 or MKV). It's probably not AVI. Change the extension to match the true container. MediaInfo will also identify the subtitle type. You will need to know that in order to deal with them. Put MediaInto into View -> Text mode. Copy the text and paste it in a post here.

The media players built into TVs usually can't handle embedded soft subs.

General
Unique ID : 14144656942011774401815292333548383259 (0xAA4296E11ADBC1BF1B452CEAFA42C1B)
Complete name : C:\Users\a1\Downloads\Movie.mkv
Format : Matroska
Format version : Version 4
File size : 276 MiB
Duration : 51 min 48 s
Overall bit rate : 744 kb/s
Movie name : Movie
Writing application : Lavf58.20.100
Writing library : Lavf58.20.100
Comment : MiNX - Small HD episodes
ErrorDetectionType : Per level 1
ANYWAY : enjoy your star trek kids
GREETZ_TO : BHD staff for being amazing uwu
HI : pls let me (impragma) back on BTN, I miss it :'(

Video
ID : 1
Format : HEVC
Format/Info : High Efficiency Video Coding
Format profile : Main@L3.1@Main
Codec ID : V_MPEGH/ISO/HEVC
Duration : 51 min 48 s
Bit rate : 8 489 kb/s
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Variable
Frame rate : 23.976 FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Bits/(Pixel*Frame) : 0.384
Stream size : 3.07 GiB
Title : MiNX - Small HD episodes
Writing library : x265 3.1.2+1-76650bab70f9:[Linux][GCC 8.3.0][64 bit] 8bit+10bit+12bit
Encoding settings : cpuid=1049583 / frame-threads=2 / wpp / no-pmode / no-pme / no-psnr / no-ssim / log-level=2 / input-csp=1 / input-res=1280x720 / interlace=0 / total-frames=0 / level-idc=0 / high-tier=1 / uhd-bd=0 / ref=2 / no-allow-non-conformance / no-repeat-headers / annexb / no-aud / no-hrd / info / hash=0 / no-temporal-layers / open-gop / min-keyint=23 / keyint=250 / gop-lookahead=0 / bframes=4 / b-adapt=0 / b-pyramid / bframe-bias=0 / rc-lookahead=15 / lookahead-slices=4 / scenecut=40 / radl=0 / no-splice / no-intra-refresh / ctu=64 / min-cu-size=8 / no-rect / no-amp / max-tu-size=32 / tu-inter-depth=1 / tu-intra-depth=1 / limit-tu=0 / rdoq-level=0 / dynamic-rd=0.00 / no-ssim-rd / signhide / no-tskip / nr-intra=0 / nr-inter=0 / no-constrained-intra / strong-intra-smoothing / max-merge=2 / limit-refs=3 / no-limit-modes / me=1 / subme=2 / merange=57 / temporal-mvp / weightp / no-weightb / no-analyze-src-pics / deblock=0:0 / sao / no-sao-non-deblock / rd=2 / early-skip / rskip / fast-intra / no-tskip-fast / no-cu-lossless / no-b-intra / no-splitrd-skip / rdpenalty=0 / psy-rd=2.00 / psy-rdoq=0.00 / no-rd-refine / no-lossless / cbqpoffs=0 / crqpoffs=0 / rc=crf / crf=24.1 / qcomp=0.60 / qpstep=4 / stats-write=0 / stats-read=0 / ipratio=1.40 / pbratio=1.30 / aq-mode=2 / aq-strength=1.00 / cutree / zone-count=0 / no-strict-cbr / qg-size=32 / no-rc-grain / qpmax=69 / qpmin=0 / no-const-vbv / sar=1 / overscan=0 / videoformat=5 / range=0 / colorprim=2 / transfer=2 / colormatrix=2 / chromaloc=0 / display-window=0cll=0,0 / min-luma=0 / max-luma=255 / log2-max-poc-lsb=8 / vui-timing-info / vui-hrd-info / slices=1 / no-opt-qp-pps / no-opt-ref-list-length-pps / no-multi-pass-opt-rps / scenecut-bias=0.05 / no-opt-cu-delta-qp / no-aq-motion / no-hdr / no-hdr-opt / no-dhdr10-opt / no-idr-recovery-sei / analysis-reuse-level=5 / scale-factor=0 / refine-intra=0 / refine-inter=0 / refine-mv=0 / refine-ctu-distortion=0 / no-limit-sao / ctu-info=0 / no-lowpass-dct / refine-analysis-type=0 / copy-pic=1 / max-ausize-factor=1.0 / no-dynamic-refine / no-single-sei / no-hevc-aq / no-svt / no-field / qp-adaptation-range=1.00
Language : English
Default : Yes
Forced : No

Audio
ID : 2
Format : AAC LC
Format/Info : Advanced Audio Codec Low Complexity
Codec ID : A_AAC-2
Duration : 51 min 48 s
Bit rate : 768 kb/s
Channel(s) : 2 channels
Channel layout : L R
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 SPF)
Compression mode : Lossy
Stream size : 285 MiB
Title : MiNX - Small HD episodes
Writing library : Lavc58.35.100 aac
Language : English
Default : Yes
Forced : No

Text
ID : 3
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Duration : 48 min 32 s
Bit rate : 43 b/s
Count of elements : 481
Stream size : 15.4 KiB (0%)
Title : MiNX - Small HD episodes
Language : English
Default : Yes
Forced : No

[jagabo]

As suspected, your video is not AVI, it's MKV. Try extracting the subs with MkvExtractGUI.

[ProWo]

Remux the whole avi to mkv with Mkvtoolnix. Then play this mkv on your TV.

[millsy5]

As suspected, your video is not AVI, it's MKV. Try extracting the subs with MkvExtractGUI.

I'll install MkvExtractGUI and see how that goes. I'll let you know if I get it working.

In the meantime, I downloaded a movie that has .sub files, to see if the subtitles work on my Panasonic TV. An earlier reply stated that my TV supports .sub files. For this movie there were 5 files that I downloaded - the movie itself and 4 English subtitle files.

1. mp4 video file (for this post I'll call it 'Movie-file')
2. Movie-file_track4_eng (PC says it's ManageSoft Download Staging Index)
3. Movie-file_track4_eng.sub
4. Movie-file_track5_eng (PC says it's ManageSoft Download Staging Index)
5. Movie-file_track5_eng.sub

I've no idea what track4 or track5 refers. I played the movie on my PC using VLC and the subtitles worked, even though the filenames are different i.e the .mp4 and .sub filename are not identical.
I tried it again with the track5 ones in the folder and it worked.
I tried it again without the ManageSoft file and it did not work. It looks like this ManageSoft Download Staging Index is required.

Next I tried it on my TV. I put all 5 on the USB and played the movie. The subtitles did not display.
I then renamed the subtitle files to match the filename of the movie and it still did not work.
Any idea what I'm doing wrong?

[jagabo]

First of all, turn off Explorer's Hide Extensions For Known File Types option. That will let you see the extensions.

SubRip .SUB include and index file, .IDX. You need that too.

Do you have any reason to believe your TV supports multiple sub files? Try the obvious first. Use only one sub with the exact same filename, just a different extension:

Movie-file.mkv
Movie-file.sub
Movie-file.idx

If that works then try renaming the subs:

Movie-file.mkv
Movie-file.en.sub
Movie-file.en.idx

If that works then try multiple sub files:

Movie-file.mkv
Movie-file.en.sub
Movie-file.en.idx
Movie-file.fr.sub
Movie-file.fr.idx

See if you can switch between the different subs.

[millsy5]

First of all, turn off Explorer's Hide Extensions For Known File Types option. That will let you see the extensions.

It's only the English sub that I want. I turned on the extensions and the files are exactly as you have i.e. .mp4, .idx and .sub.

Movie-file.mp4
Movie-file_track4_eng.sub
Movie-file_track4_eng.idx
Movie-file_track5_eng.sub
Movie-file_track5_eng.idx

I renamed the .sub and .idx files to match the .mp4 filename but it did not work on the TV i.e.

Movie-file.mp4
Movie-file.sub
Movie-file.idx

[jagabo]

Note that the extension .SUB is used for more than one type of subtitles. Mabye your TV doesn't support SUB/IDX. You may have to convert to SRT.

[orsetto]

The problem stems partially from initial confusion about the file type, now clarified.

The MINX file isn't AVI, its not even the typical h264/x264 MP4 or MKV that most TVs can read. This file is in the still-widely-incompatible "new" x265 or HEVC format, which pretty much nothing plays except VLC and other PC-based media players. Most TVs and other non-PC hardware can't even recognize HEVC x265 video on a USB stick, much less the subtitles: if you can actually play the MINX video directly from USB on your Panasonic and LG TVs, thats a pretty cool feature.

As far as subs go, the most compatible format is .srt. Unfortunately more and more videos are circulating with embedded or bundled sub/idx format instead, the subtitle standard for BluRay discs. Most TVs and hardware media players have trouble with sub/idx, and it isn't easy to DIY convert properly to srt format. Your best bet in such cases is simply look for a standard SRT version that matches the video file name on srt subtitle archive sites like Addic7ed and SubScene. This would apply to both video examples you've asked about so far, the mkv and the mp4: each has the near-useless sub/idx format. Get .srt replacements and your problem goes away.

HEVC/x265 with sub/idx subs is great if you want smallish HDTV file sizes for PC playback with VLC etc, but unless one owns the latest cutting-edge gear it remains problematic for viewing methods that don't involve a PC. For widest compatibility with direct USB>TV play, avoid videos with x265 or HEVC in the name. Stick with the larger x264-spec versions, and fetch matching separate SRT format subtitles if/when necessary.

[millsy5]

Note that the extension .SUB is used for more than one type of subtitles. Mabye your TV doesn't support SUB/IDX. You may have to convert to SRT.

Directly from the TV manual:

Supported Subtitle Formats

- MicroDVD, SubRip, TM player (.srt, .sub, .txt)
- The video file and subtitles text file are inside the same folder, and the file names are the same except for the file extensions
- If there are more than one subtitles text files inside the same folder, they are displayed in the following order of priority: ".srt", ".sub", ".txt".

[millsy5]

Your best bet in such cases is simply look for a standard SRT version that matches the video file name on srt subtitle archive sites like Addic7ed and SubScene. This would apply to both video examples you've asked about so far, the mkv and the mp4: each has the near-useless sub/idx format. Get .srt replacements and your problem goes away.

HEVC/x265 with sub/idx subs is great if you want smallish HDTV file sizes for PC playback with VLC etc, but unless one owns the latest cutting-edge gear it remains problematic for viewing methods that don't involve a PC. For widest compatibility with direct USB>TV play, avoid videos with x265 or HEVC in the name. Stick with the larger x264-spec versions, and fetch matching separate SRT format subtitles if/when necessary.

Thanks. I'll check out those subtitle archive sites.

I'll see if I can find a video with x264 codec and .srt subtitle file and post my results here.

[jagabo]

Here's an AVC+AAC MKV file with embedded SRT subs. Note that many players will not respond to many of the property tags. Or they may display them as part of the subtitle text. A separate SRT file is included too (same subs)

[ProWo]

You can also convert the sub/idx to srt with Subtitle-Edit.

[orsetto]

Note that the extension .SUB is used for more than one type of subtitles. Mabye your TV doesn't support SUB/IDX. You may have to convert to SRT.

Directly from the TV manual:

Supported Subtitle Formats

- MicroDVD, SubRip, TM player (.srt, .sub, .txt)
- The video file and subtitles text file are inside the same folder, and the file names are the same except for the file extensions
- If there are more than one subtitles text files inside the same folder, they are displayed in the following order of priority: ".srt", ".sub", ".txt".

What jagabo said: as confusing and totally stupid as it seems, for whatever idiotic reason Sony chose to re-use the tag SUB as part of the goofy blu-ray spec. So you always need to think twice when a TV or other device manual says it can read "sub" files: usually they're referring to the older definition, which is just another name for "srt" format. The way you identify them is bluray "sub" usually comes with a supplemental "idx" file: these are in weird non-text format. A lone "sub" is usually an old srt, but honestly I can't remember the last time I saw one of those. Almost all standard text subs of the past decade are tagged with the extension "srt" (which is all you'll find on subtitle sites, nobody but commercial disc mfrs wants anything else).

Some recent MKV files have embedded "ass" format subs. These are usually readable from USB by a TV or BluRay player: if not, the ".ass" is easily extracted and converted to"srt" by any subtitle editing app.

Converting sub/idx to srt is possible but a PITA, often with not-great results. Most of us prefer to exhaust every other possible source for an existing srt replacement, conversion being a last resort. There are srt versions of almost anything floating around if you patiently search.

https://forum.videohelp.com/threads/167667-Convert-sub-idx-to-srt-subtitles

[jagabo]

Yes, SUB/IDX are bitmap images and timing/placement instructions -- ie pictures of text, not text as you would find in a Notepad file. To convert SUB/IDX to SRT requires optical character recognition.

[millsy5]

Here's an AVC+AAC MKV file with embedded SRT subs. Note that many players will not respond to many of the property tags. Or they may display them as part of the subtitle text. A separate SRT file is included too (same subs)

I tried your files and tested them on PC with VLC, old LG TV, and new Panasonic TV.

- VLC: worked as expected

- LG TV: subtitles displayed but the font stayed the same i.e. no bold, italic, etc.

- Panasonic TV: subtitles did not display

[jagabo]

Here's an AVC+AAC MKV file with embedded SRT subs. Note that many players will not respond to many of the property tags. Or they may display them as part of the subtitle text. A separate SRT file is included too (same subs)

I tried your files and tested them on PC with VLC, old LG TV, and new Panasonic TV.

Did you try just the MKV file? Or the MKV and the SRT? The MVK file has the SRT subs embeded. Any player that supports embeded SRT subs will be able to display them -- no need for the separate SRT file. Players that don't support embeded subs, but do support separate SRT files, should be able to display the subs if you included the SRT file. Be sure subs are enabled in the player/TV.

[millsy5]

Did you try just the MKV file? Or the MKV and the SRT? The MVK file has the SRT subs embeded. Any player that supports embeded SRT subs will be able to display them -- no need for the separate SRT file. Players that don't support embeded subs, but do support separate SRT files, should be able to display the subs if you included the SRT file. Be sure subs are enabled in the player/TV.

I tried both i.e. the MKV on its own and also with the SRT in the same folder. Neither worked.

I'm convinced at this stage that my TV does not support subtitles. The TV manual states 2 ways to display/hide the subtitles.

1. Using the STTL on the remote
2. Navigate to Menu->Setup->Display Settings -> Preferred Subtitle type.

For number 2, when I go to 'Display Settings' there is no 'Preferred Subtitle type' option.

[millsy5]

The TV manual states 2 ways to display/hide the subtitles.

1. Using the STTL on the remote
2. Navigate to Menu->Setup->Display Settings -> Preferred Subtitle type.

For number 2, when I go to 'Display Settings' there is no 'Preferred Subtitle type' option.

BTW the TV manual is a generic one that has multiple TV models which is why my TV settings doesn't need to match the manual.

[jagabo]

It might support embedded subs in a different container. MP4 "Timed Text" subtitles are a little different than SRT subs (just an extra header element). I used Handbrake to quickly convert the SRT from the MKV to Timed Text in MP4. All the property tags were lost so don't expect those to work.

[orsetto]

I tried both i.e. the MKV on its own and also with the SRT in the same folder. Neither worked.

I'm convinced at this stage that my TV does not support subtitles.

Yes, I agree: perhaps give this up and consider other playback options for your Panasonic display.

After doing cursory research on recent Panasonic TVs this morning, I found loads of plaintive posts all over the web regarding this subtitle from USB video files issue. The consensus seems to be: Panasonic has no idea what their TVs actually can and cannot do, so the manual is gibberish not to be trusted. Panasonic does not sell TVs in North America anymore, which tells you something of how they view the market. Ten years ago they mfd their own very nice sets using top quality LCD panels (mine still works great), nowadays they seem to subcontract most of their EU TV production to third party mfrs (unprecedented for Matsushita).

While disappointing, it isn't entirely unexpected: consumers haven't yet realized that electronics mfrs no longer keep to a consistent thru line of performance and features from year to year. One should not assume "of course all modern TVs play all standard video formats and subtitles perfectly via USB stick" just because one or two brand/models of TV do so flawlessly. Unfortunately, USB video playback is not a bog-standard, defined, guaranteed feature for every TV on the market: most just pay lip service to the idea. I've lost count of how many premium TVs (cough, Sony, cough) make you jump thru ridiculous hoops to operate USB video playback, and if you have the temerity to solve that riddle, reward you by completely corrupting and trashing every file on a USB stick as you remove it from the TV. Lovely.

Rather than pull your hair out trying to solve the insoluble, perhaps just buy a supplemental second-hand (or new) compact BluRay player dedicated to playing USB sticks for your Panasonic TV. BD players are usually great at automatically picking up and displaying subs embedded in mkv files, and recognizing/displaying separate srt subtitle files. Since you aren't buying the thing for its interactive disc playing abilities, it can be an old obsolete cheap model: all it needs is a USB port in front (and of course make sure the remote is included). I rely on the old LG BP240 and BP340 models for this USB player task with my TVs: in my experience a BD player makes a far higher quality USB media player than any generic small USB-only media device.

[millsy5]

It might support embedded subs in a different container. MP4 "Timed Text" subtitles are a little different than SRT subs (just an extra header element). I used Handbrake to quickly convert the SRT from the MKV to Timed Text in MP4. All the property tags were lost so don't expect those to work.

That didn't work either, both with VLC or my Panasonic TV. I'm familiar with Handbrake. I've used it a few times to convert x265 to x264. With Handbrake there is a subtitle option to 'Burn In' the subtitles. If this is what you used to embed the subs then I would have thought it would work.

I tried both i.e. the MKV on its own and also with the SRT in the same folder. Neither worked.

I'm convinced at this stage that my TV does not support subtitles.

Yes, I agree: perhaps give this up and consider other playback options for your Panasonic display.

After doing cursory research on recent Panasonic TVs this morning, I found loads of plaintive posts all over the web regarding this subtitle from USB video files issue. The consensus seems to be: Panasonic has no idea what their TVs actually can and cannot do, so the manual is gibberish not to be trusted. Panasonic does not sell TVs in North America anymore, which tells you something of how they view the market.
[...]
Rather than pull your hair out trying to solve the insoluble, perhaps just buy a supplemental second-hand (or new) compact BluRay player dedicated to playing USB sticks for your Panasonic TV. BD players are usually great at automatically picking up and displaying subs embedded in mkv files, and recognizing/displaying separate srt subtitle files. Since you aren't buying the thing for its interactive disc playing abilities, it can be an old obsolete cheap model: all it needs is a USB port in front (and of course make sure the remote is included). I rely on the old LG BP240 and BP340 models for this USB player task with my TVs: in my experience a BD player makes a far higher quality USB media player than any generic small USB-only media device.

Thanks for the advice and research. The BD player sounds like a good idea, assuming it will work for my TV. I'll definitely consider looking into this as an option.

[jagabo]

It might support embedded subs in a different container. MP4 "Timed Text" subtitles are a little different than SRT subs (just an extra header element). I used Handbrake to quickly convert the SRT from the MKV to Timed Text in MP4. All the property tags were lost so don't expect those to work.

That didn't work either, both with VLC or my Panasonic TV. I'm familiar with Handbrake. I've used it a few times to convert x265 to x264. With Handbrake there is a subtitle option to 'Burn In' the subtitles. If this is what you used to embed the subs then I would have thought it would work.

The mp4 file I uploaded works in VLC. You may have to manually enable the subs with Subtitle -> Sub Track -> Track1. And obvious, I didn't burn the subs in if you didn't see them.