As ssam already mentioned, Conduit has been discussed by the actual projects (don't have the link on hand right now, though) -- I can also think of other useful apps like Miro or Elisa that would benefit from having access to a transcoder. But, to answer the question, "just call Gstreamer" won't actually do anything; for you to perform the transcoding _using_ GStreamer you'll have to duplicate all of the steps that Arista abstracts; eliminating the need to do that is exactly the point.