Adding Subtitles is not part of the MP4 standard. Ahead thought this was a nice feature, so we provided a solution to incorporate subtitles into an MP4 Video format. When others eventually come around to supporting the MP4 video format, and they are all working on it
, they will need to find their own solution for supporting subtitles.
The plugin we provide for WMP9 only allows it to play MP4, it does not include a solution to play the subtitles.