Hi,
I just checked a new Moodle 2.5 videofile add-on at https://moodle.org/plugins/view.php?plugin=mod_videofile and I verified (first in a local server, and later in a production server) that it can display captions in many languages for mp4 video files that work in several Windows browsers (firefox, chrome, safari, IE10), Mac browsers (firefox, chrome, safari) and Ubuntu Linux (firefox).
This seems to be a very good and simple way to upload video files with text subtitles in several languages in a Moodle server.
There is documentation about it in English (and a link to Spanish doc) at http://docs.moodle.org/25/en/mod/videofile/view .
Maybe some readers of this forum would like to translate the documentation into other languages.