[rygel] docs: RygelMediaEngine: More description

[Murray Cumming <murrayc src gnome org>]

commit 94c5ae3e4f742dcc65f0fbd36d5fb0b96bac07e6
Author: Murray Cumming <murrayc murrayc com>
Date:   Mon Feb 11 11:40:36 2013 +0100

    docs: RygelMediaEngine: More description
    
    More text from Mark Ryan

 src/librygel-server/rygel-media-engine.vala |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)
---
diff --git a/src/librygel-server/rygel-media-engine.vala b/src/librygel-server/rygel-media-engine.vala
index 3c55cd6..a3de9c8 100644
--- a/src/librygel-server/rygel-media-engine.vala
+++ b/src/librygel-server/rygel-media-engine.vala
@@ -27,7 +27,9 @@ public errordomain Rygel.MediaEngineError {
 /**
  * This is the base class for media engines that contain knowledge about 
  * the streaming and (optionally) the transcoding and seeking capabilites
- * of the media library in use.
+ * of the media library in use. Derived classes also instantiate any
+ * transcoding objects supported by the media engine and specify the list
+ * of media formats the engine is capable of playing.
  *
  * See, for instance, Rygel's built-in "gstreamer" and "simple" media engines,
  * or the external rygel-gst-0-10-media-engine module.
@@ -88,6 +90,10 @@ public abstract class Rygel.MediaEngine : GLib.Object {
      * Other DLNA profiles may be supported as transcoding targets -
      * @see rygel_media_engine_get_transcoders().
      *
+     * This information is needed to implement DLNA's
+     * ConnectionManager.GetProtocolInfo call and to determine whether Rygel
+     * can accept an uploaded file.
+     *
      * @return A list of #RygelDLNAProfile<!-- -->s
      */
     public abstract unowned List<DLNAProfile> get_dlna_profiles ();