Carriage of synchronized graphics and text in MP4 files

Following my previous post on the synchronization of HTML 5 video and SVG content, we are now proposing a contribution to MPEG, for the upcoming meeting in Stockholm. This work is part of the activity on timed text (subtitling, caption …). We propose to store frame-based SVG, WebVTT, HTML … content as a particular timed metadata track. We take special care of secondary resources, i.e. resources pointed to by the SVG, HTML … The goal is to be able to use SVG, WebVTT or HTML timed tracks in Dynamic Adaptive Streaming over HTTP.

See our contribution here:


and the presentation:

[slideshare id=13692930&doc=m25978-120719055432-phpapp01]

Update 19/7/2012

You can find at the following location:
the following files:

  • webvtt.mp4 : an example of carriage of WebVTT subtitles in MP4 following our proposal.
  • ttml.mp4: an example of carriage of TTML in MP4 following our proposal.
  • ttml_with_images.mp4: an example of carriage of TTML with images, following SMPTE-TT.

The files *_info.xml are MP4Box dumps (in an XML form) of the box structure if you want to check the internals of the MP4 files.

I’d like to emphasize that these examples do not use non-standard boxes. These files are compatible with ISO/IEC 14996-12 4th edition. I just used the non standard ‘subm’ handler value for the tracks (as requested by the MPEG File Format group) and ‘subr’ for the meta box.

Comments/Questions are welcome.

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