MKV files with embedded VTT subtitles can't be played

General Discussions
1

It makes the transcoder fails with this error

[Transcoder] Decoder (codec none) not found for input stream #0:3

My plex version is Version 1.11.1.4760

Text #2
ID                                       : 5
Format                                   : S_TEXT/WEBVTT
Codec ID                                 : S_TEXT/WEBVTT
Duration                                 : 2h 43mn
Bit rate                                 : 55 bps
Count of elements                        : 2311
Stream size                              : 66.5 KiB (0%)
Language                                 : English
Default                                  : No
Forced                                   : No
2

How odd Plex detects the language of the subtitle but shows none for the format of said subtitle…

3

What client are you using?

I ran a quick test, here’s what I found:

  • Plex Media Player on Windows correctly plays both embedded and external webvtt subtitles.
  • Plex Web (Chrome/Windows) correctly plays external webvtt subtitles. It will not play a movie with embedded webvtt subtitles.

Plex Media Player for Windows Direct Plays a movie with embedded and external webvtt subtitles. The external subtitles are correctly identified. The embedded subtitles show up as “English-NONE” but they still play correctly.

Plex Web (Chrome, Windows 10), will not play the movie, even if subtitles = none. Just having the webvtt subs embedded in the MKV will make it fail. I eventually receive the “Conversion failed. The transcoder crashed or refused to start up.” message.

External webvtt subtitles are OK. I muxed out the embedded webvtt subtitles, left the embedded PGS subtitles and the external .vtt file and the movie played correctly in both PMP and Plex Web.

PMS 1.12.0.4829
PMP 2.5.0
Plex Web 3.37.2
All on the same Windows 10 system.

Text #1
ID                                       : 4
Format                                   : PGS
Codec ID                                 : S_HDMV/PGS
Codec ID/Info                            : Picture based subtitle format used on BDs/HD-DVDs
Duration                                 : 1 h 57 min
Bit rate                                 : 52.6 kb/s
Count of elements                        : 3914
Stream size                              : 44.3 MiB (0%)
Language                                 : English
Default                                  : Yes
Forced                                   : No

Text #2
ID                                       : 5
Format                                   : S_TEXT/WEBVTT
Codec ID                                 : S_TEXT/WEBVTT
Duration                                 : 1 h 57 min
Bit rate                                 : 74 b/s
Count of elements                        : 1960
Stream size                              : 64.2 KiB (0%)
Language                                 : English
Default                                  : No
Forced                                   : No
4

To further complicate… The Video Stream is VC-1 and that’s a single threaded operation and almost a guaranteed transcode on just about everything (PMP ‘may’ Direct Play it).

The subs can be converted to UTF-8 (probably) easily, but the only way to deal with that VC-1 video track is with a transcode or a re-encode.

5

PMP (Win10) direct plays VC1 video and dts audio. Plex Web (Chrome, Win10) transcodes VC1 to H264, dts to AAC.

To convert subtitles, check out Subtitle Edit, http://www.nikse.dk/SubtitleEdit/. Very easy to convert between subtitle formats. It will read directly from a MKV file, then save converted subtitles in appropriate file - .srt, .ssa, etc.

To mux converted subs back into the MKV file, check out MKVToolNix, https://mkvtoolnix.download/. It also has capability to edit headers and chapters.

6

Xmedia Recode can remux video streams while converting/remuxing audio streams and converting sub tracks in one pass to save time.

https://www.xmedia-recode.de/en/download.html

7

This is a ffmpeg issue…They didn’t implement VTT subtitles in MKV correctly