This is the default media player on the laptops, via Browse. See also GStreamer#Totem plugin. For testing, versioning, and inclusion purposes, this should be treated like an activity. Other activities and bundles will depend specifically on this subpart of Browse, and not necessarily Browse itself.
One, possibly inaccurate, way to see what mime types and codecs Totem/Gnash thinks it can support is to enter about:plugins in the Browse location field.
Adding MP3 capabilities
- Multimedia - introduction to multimedia on the XO