gstreamer/gst-libs/gst/media-info

* media-info is a library to collect metadata and streaminfo from media
  files

* the current implementation is idler-based.

* you create a new media_info object
* you set the string name of a source element to use using g_object_set or
  gst_media_info_set_source
* you declare you'll read a given file by using gst_media_info_read_with_idler
* you loop gst_media_info_read_idler (info, &stream) as long as it returns TRUE
  and as long as stream is still NULL


* INTERNALS:
  - instance_init sets up the media info reader, its elements, and connects
    the deep_notify callback
  - read_with_idler resets the media info reader object,
    and sets location and flags

  - read_idler runs through a state machine:
    NULL - TYPEFIND - STREAM - METADATA - STREAMINFO - FORMAT

  - NULL: just returns find_type_pre, which moves state to TYPEFIND
  - TYPEFIND:
    - iterates as long as it can until it has priv->type 
    - find_type_post
    - call gmi_set_mime which creates a pipeline to decode stuff
    - move to STREAM

  - STREAM