I need to retrieve non-video, non-audio application data which is embedded in an MP4 file. The data consists of measurements taken at the same time as the MP4 was recorded, which need to be rendered as charts in sync with the video & audio. The charts won’t be rendered using DirectShow.
The data can be written into the MP4 file in one of three ways:
1. as multiple top-level mdat boxes
2. as multiple top-level boxes with proprietary FourCC
3. as a third track.
Which of the above methods of embedding the data would be most appropriate for DirectShow? What would the steps be to retrieve the data?
I have sample MP4 files in all of the three above formats and I can play the video and audio using Haali splitter. Does it come down to whether the MP4 source filter supports the reading of data? I would like to avoid having to write my own MP4 source filter if possible!
Many thanks
As you might have known, there is no stock filter for MP4. And your best way is to see what exactly is supported on the filter that you are going to use. For example, it is highly unlikely that these filters are going to make custom format data available.
The good news is that decent multiplexer/demultiplexer MP4 filters are available in source http://www.gdcl.co.uk/mpeg4/ If the measurements are timestamped, then additional track looks best to me. You can always put extra data into track description box. Source code availability enables you to add reasonable support for your custom format without much of a trouble.