This is mostly a note pad for myself with quick instructions about how to add subtitles streams to an existent video.

Although I’m personally more in favor of using Ogg, reality is that Matroska is the one that is getting the biggest support among the Open Source container formats and it also has a great deal of features.

Also, because of widespread adoption, in spite of not having a really formal syntax and many features, SubRip is my chosen format for subtitles.

Now, I’m the owner of a Samsung 3D SmartTV which allows external SubRip .srt files. However, it also supports Matroska files with embedded subtitles and having the subtitles in the same container than the audio and video streams have some advantages. The main one is that I would be able to play such file through UPnP, with subtitles included, meanwhile that’s not possible with some UPnP servers if the subtitles are in a different file than the video. That’s the case, for example, with BubbleUPnP for Android, which I use from a tablet.

Anyway, enough introduction.

For creating a Matroska file from an existing video and a SubRip file I would use the MKVToolNix package. In a Debian based system you can install it with the following command:

root$ apt-get install mkvtoolnix

In order to merge video and a subtitles (actually, many multiple streams), the proper command for this would be mkvmerge. Its usage is quite straight forward:

$ mkvmerge -o el_ministerio_del_tiempo_-_s01e01_-_el_ministerio_del_tiempo_-_with-lang-codes.mkv el_ministerio_del_tiempo_-_s01e01_-_el_ministerio_del_tiempo.mp4 --language 0:spa el_ministerio_del_tiempo_-_s01e01_-_el_ministerio_del_tiempo.srt --default-track 0
mkvmerge v7.1.0 ('Good Love') 64bit built on Jul 28 2014 11:58:03
'el_ministerio_del_tiempo_-_s01e01_-_el_ministerio_del_tiempo.srt': Using the demultiplexer for the format 'SRT subtitles'.
'el_ministerio_del_tiempo_-_s01e01_-_el_ministerio_del_tiempo.mp4' track 0: Using the output module for the format 'AVC/h.264'.
'el_ministerio_del_tiempo_-_s01e01_-_el_ministerio_del_tiempo.mp4' track 1: Using the output module for the format 'AAC'.
'el_ministerio_del_tiempo_-_s01e01_-_el_ministerio_del_tiempo.srt' track 0: Using the output module for the format 'text subtitles'.
The file 'el_ministerio_del_tiempo_-_s01e01_-_el_ministerio_del_tiempo_-_with-lang-codes.mkv' has been opened for writing.
'el_ministerio_del_tiempo_-_s01e01_-_el_ministerio_del_tiempo.mp4' track 0: Extracted the aspect ratio information from the MPEG-4 layer 10 (AVC) video data and set the display dimensions to 1024/576.
Progress: 100%
The cue entries (the index) are being written...
Muxing took 42 seconds.

That’s basically it. With this command we will get, from a .mp4 and a .srt file, a .mkv file with both merged together. Now, if we would be wanting to add more languages we could have done something like this:

$ mkvmerge -o el_ministerio_del_tiempo_-_s01e01_-_el_ministerio_del_tiempo_-_with-lang-codes.mkv el_ministerio_del_tiempo_-_s01e01_-_el_ministerio_del_tiempo.mp4 --language 0:spa el_ministerio_del_tiempo_-_s01e01_-_el_ministerio_del_tiempo-es.srt --language 1:eng el_ministerio_del_tiempo_-_s01e01_-_el_ministerio_del_tiempo-en.srt --default-track 0
...

This way we would be having Spanish and English subtitles, and the former would be the default one.

For more information, just check mkvmerge’s manual.