[malch]

Primary environment is Kodi 18.4 on Manjaro Linux. However, I have also reproduced the problem with Kodi 18.5 on Windows 10.

I have recently re-encoded a bunch of videos using Handbrake with:
* Container: MP4
* Video: 1080p HEVC
* Audio: AAC Stereo
* Subs: One tx3g English Subtitle

The videos reside on my NAS connected via Gigabit Ethernet.

Kodi plays the videos fine. It recognizes the subtitle and says it's displayed, but it isn't. Disabling and re-enabling subtitle display doesn't help.

HOWEVER, if I skip back through the video 10 seconds, Kodi immediately starts displaying the subtitles (and they are in sync) for a minute or two. Then it seems to lose the subtitle stream again. Skip back 10 seconds, and the subtitles are restored for a while. Rinse and repeat.

The videos and subs play fine on VLC. I have extracted the sub stream and eyeballed it. No weird characters or other junk.

If I export the sub stream as a .srt and place it next to the .mp4, Kodi does display the subs fine.

I will also note that Kodi played the original (H.264) videos with internal subs just fine.

I will post a log if requested but I have examined several (with debug on) and see no errors or other clues (although, Kodi obviously does recognize the sub stream).

Seems like an issue with the demux and/or buffering and it appears to be HEVC specific.

Any thoughts or suggestions?

[Klojum]

To receive meaningful assistance you will need to provide a full debug log.

The instructions are here... debug log (wiki)

If you are using the Basic Method, then ensure the following is applied...
1.Enable debugging in Settings>System Settings>Logging,
2.Restart Kodi
3.Replicate the problem.
4.Upload the log to Kodi Paste Site manually or use the Kodi Logfile Uploader. (wiki) With either method post the link to the log back here.

If you are using the Advanced Method ensure you have correctly created and applied the advancedsettings.xml file (wiki)

In both instances, you should see the word DEBUG throughout the log.

Note: Full logs only. No partial or redacted logs
Do NOT post your logs directly into the forum. Use the Kodi Paste Site. Post the link to your pasted log in the forum

[malch]

Okay, here's a debug log from Kodi 18.5 on Windows:

https://paste.kodi.tv/casebizici.kodi

I played the video for a few seconds and subtitles were not displayed. I skipped back 10 seconds. Subtitles were displayed for a while. Once the subs stopped displaying again, I stopped the video and exited Kodi.

[DaVu]

Probably an issue at the tx3g implementation. Please feel free to open a bug report at: https://github.com/xbmc/xbmc/issues

If possible, it would be nice if you could share a snippet of that file in question. Make sure it's long enough so that one is able to play around with it (2 minutes should be enough I guess)

[malch]

Thanks for that. I have subsequently discovered:

1. Some other files that were identically re-encoded do NOT suffer from the problem

2. I can fix the problem by demuxing the sub to a separate .srt file and then re-muxing the .srt back into the mp4.

I'll mess around a little more and see what other clues I can find. If appropriate, I'll submit a bug report and try to include a 2 minute snip that demonstrates the problem.

It may turn out the problem lies strictly in the encoding of the mp4, but even in that event, it would be cool if Kodi was a little more forgiving (VLC doesn't have any problem).

[Stan Pulsar]

Hello there,

for the records, I get almost the same issue (but subtitles don't disapper, they just move around), and IMHO there must be some kind of link.
I filled a bug report here