when playing back media on mac, make sure you are using a terminal associated with the currently logged in user!!
using a different user will allow the video to show up

avbin is used by default in pyglet
some discussion about the use of gstreamer in pyglet
http://code.google.com/p/pyglet/wiki/MediaOnLinux
http://www.mechanicalcat.net/richard/log/Python/Say_hello_to_pyglet

gstreamer interface reported to be complex.