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Subtitles and mp4 metadata

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Mark Van den Borre edited this page Dec 28, 2017 · 11 revisions

Mp4 metadata? AtomicParsley or mp4tags

To embed non-subtitle metadata (like the title, penta id, ...) into an mp4 file:

apt-get install atomicparsley
AtomicParsley test.mp4 --TVShowName "FOSDEM" --TVEpisodeNum 1234 --TVSeason 18 --overWrite

Or use mp4v2-utils:

apt-get install mp4v2-utils
mp4tags -album 'FOSDEM 2018' -song 'Embedding mp4 tags in blah using llvm' -season 18 -episode 1234 -year 2018 -longdesc 'Ik heb eerbied voor jouw grijze haaaaareeeeen. Ze beschermen je lieve geziiiiiicht.' test.mp4

Then check if metadata have been recorded into the mp4 correctly:

AtomicParsley test.mp4 -t

Web based playback with subtitles? vtt format

Vtt is the w3c standard format for web based subtitle playback.

  • One can export subtitles in .vtt directly from amara.org.
  • Ffmpeg can convert existing subtitles to .vtt:
ffmpeg -i test.srt test.vtt

Web based playback with subtitles? Use javascript

In theory, html5 should support subtitle track playback without any javascript. In practice, there are still a few rough edges.

We use the clappr java script based player for streaming. Clappr has quite good builtin support for subtitle playback. An example:

<html>
<head>
  <script type="text/javascript" src="https://cdn.jsdelivr.net/npm/clappr@latest/dist/clappr.min.js"></script>
</head>

<body>
  <div id="player"></div>
  <script>
var player = new Clappr.Player({
  parentId: '#player',
  source: 'http://clappr.io/highline.mp4',
  poster: 'http://clappr.io/poster.png',
  height: 360,
  width: 640,
  playback: {
    crossOrigin: 'anonymous', // Required if track loaded from another domain
    externalTracks: [
      {lang: 'en', label: 'English', src: 'https://static.playmedia-cdn.net/clappr/en.vtt'},
    ],
  },
});
  </script>
</body>


</html>

Offline playback with subtitles? Embed the subtitle track in the mp4

Embedding a subtitle track into an mp4 file is easy.

...or more explicitly:

ffmpeg -i infile.mp4 -i infile.srt -c:v copy -c:a copy -c:s mov_text outfile.mp4

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