Timed Text as subtitles within MPEG-4 video

Posted on January 16, 2007

I have been looking around for a way to easily incorporate video and an external subtitles file into a single file that will allow me to simply use a video player to view the video with the option to turn the subtitles on.

After some researching, it appears that there is a standard for including subtitles within MPEG-4 video files called MPEG-4 Part 17, or MPEG-4 Timed Text.

If you use software such as MP4Box, you can import DivX/XviD encoded video along with an external subtitle file such as SRT into a single MP4 container file.  Note: importing a video at it’s original quality level is not the same as re-encoding it into MPEG which would lead to some visual quality loss.

Now the trick is finding a video player that will be able to allow me to turn on the subtitles which watching the video.  The VLC media player (available for just about every platform out there), which can play just about anything you can throw at it, should be able to display the subtitles.

*** Update 1/17/06 ***
MP4Box did produce a MP4 file that was playable by VLC player and shows the subtitles, however, this same MP4 file didn’t work at all within QuickTime 7.1 (even after accounting for the bug that the MP4 file should be renamed with an .3GP extension so that QuickTime can show the subtitles).  Windows Media Player was able to play the video but was unable to show the subtitles.

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  • I didn’t get one when I was born.

    Jared – any solution that requires an external/separate file to contain subtitles/captions during playback is going to ultimately fail.

    I feel that the best solution is to use a container format that holds everything that a video needs which would be audio, video, subtitles, and any other metadata (like links).

    As you discovered, there are standards to implement subtitling in videos. MPEG2 has one, MPEG4 has another. Until video players implement them, it’s moot. Nobody is really using them. There needs to be a dominant standard that video players will adopt and implement. It doesn’t help that Quicktime has its own standard for subtitling, Real Player has its own, and Windows Media player has yet another standard.

    To compound things, have you noticed that GoogleVideo and YouTube’s “video players” for browers are different? A bunch of video websites have their own proprietary video players. What video standards are these players going to use? The first thing that needs to be done is to accept a SINGLE standard so that it is universal and is supported across multiple platforms. As you found out, you might’ve been able to play your clip in VLC (which I might add is NOT user friendly – at all) and you found you couldn’t do play your clip with CC in Quicktime.

  • Mark Schwartrz

    Hi Jared – Good infos about closed captioning. Have you looked into McPoodle’s work? He developed extraction tools that works with Scenarist DVD authoring. -M

  • rmpsl

    MPEG-4 Timed Text is a standard, but nobody uses it.

    The good thing about separate subtitles is that you can edit, correct, translate, resynch them whenever you want with a subtitle editor/text editor, without touching the video file. You can burn the video to CD and keep the subtitles on your hard disk.

    If you want a single file, for the time being you’re safer muxing SRT streams into MP4 (or plain old AVI) files. That’s a de facto standard. You don’t need VLC player, installing the right codec (e.g. VSFilter) is sufficient.