[rygel] server: Add AudioItem documentation

[Jens Georg <jensgeorg src gnome org>]

commit 8360c5bf5fb794de12689c1b0cc0445ddf70dc2e
Author: Craig Pratt <craig ecaspia com>
Date:   Sat Jun 21 22:13:35 2014 +0200

    server: Add AudioItem documentation
    
    Signed-off-by: Jens Georg <mail jensge org>

 src/librygel-server/rygel-audio-item.vala |   32 ++++++++++++++++++++++++++--
 1 files changed, 29 insertions(+), 3 deletions(-)
---
diff --git a/src/librygel-server/rygel-audio-item.vala b/src/librygel-server/rygel-audio-item.vala
index 5882ea5..eff94a3 100644
--- a/src/librygel-server/rygel-audio-item.vala
+++ b/src/librygel-server/rygel-audio-item.vala
@@ -1,9 +1,12 @@
 /*
  * Copyright (C) 2008 Zeeshan Ali <zeenix gmail com>.
  * Copyright (C) 2010 Nokia Corporation.
+ * Copyright (C) 2013 Cable Television Laboratories, Inc.
  *
  * Author: Zeeshan Ali (Khattak) <zeeshanak gnome org>
  *                               <zeeshan ali nokia com>
+ *         Doug Galligan <doug sentosatech com>
+ *         Craig Pratt <craig ecaspia com>
  *
  * This file is part of Rygel.
  *
@@ -25,16 +28,39 @@
 using GUPnP;
 
 /**
- * Represents an audio item.
+ * Represents an audio item contained in a file.
  */
 public class Rygel.AudioItem : MediaItem {
     public new const string UPNP_CLASS = "object.item.audioItem";
 
-    public long duration { get; set; default = -1; }  // Duration in seconds
-    public int bitrate { get; set; default = -1; }    // Bytes/second
+    /**
+     * The duration of the source content (this.uri) in seconds.
+     * A value of -1 means the duration is unknown
+     */
+    public long duration { get; set; default = -1; }
 
+    /**
+     * The bitrate of the source content (this.uri) in bytes/second.
+     * A value of -1 means the bitrate is unknown
+     */
+    public int bitrate { get; set; default = -1; }
+
+    /**
+     * The sample frequency of the source content (this.uri) in Hz.
+     * A value of -1 means the sample frequency is unknown
+     */
     public int sample_freq { get; set; default = -1; }
+
+    /**
+     * The bits per sample of the source content (this.uri).
+     * A value of -1 means the bits per sample is unknown
+     */
     public int bits_per_sample { get; set; default = -1; }
+
+    /**
+     * The number of audio channels in the source content (this.uri).
+     * A value of -1 means the number of channels is unknown
+     */
     public int channels { get; set; default = -1; }
 
     public AudioItem (string         id,