playbin2: Post a stream-changed message after activating a group

This is useful to detect when playbin2 has really switched to the next
group after about-to-finish for example.

Fixes bug #584987.

gst/playback/gstplaybin2.c

@@ -316,6 +316,8 @@ struct _GstSourceGroup
   gulong sub_no_more_pads_id;
   gulong sub_autoplug_continue_id;
 
+  gint stream_changed_pending;
+
   /* selectors for different streams */
   GstSourceSelect selector[GST_PLAY_SINK_TYPE_LAST];
 };
@@ -1997,17 +1999,26 @@ gst_play_bin_handle_message (GstBin * bin, GstMessage * msg)
       }
     }
     g_free (detail);
-  }
+  } else if (GST_MESSAGE_TYPE (msg) == GST_MESSAGE_ELEMENT) {
+    const GstStructure *s = gst_message_get_structure (msg);
 
+    /* Drop all stream-changed messages except the last one */
+    if (strcmp ("playbin2-stream-changed", gst_structure_get_name (s)) == 0) {
       group = playbin->curr_group;
+      if (!g_atomic_int_dec_and_test (&group->stream_changed_pending)) {
+        gst_message_unref (msg);
+        msg = NULL;
+      }
+    }
+  } else if (GST_MESSAGE_TYPE (msg) == GST_MESSAGE_ERROR) {
     /* If we get an error of the subtitle uridecodebin transform
      * them into warnings and disable the subtitles */
+    group = playbin->curr_group;
     if (group && group->suburidecodebin) {
-    GstObject *srcparent = gst_object_get_parent (GST_OBJECT_CAST (msg->src));
 
+      GstObject *srcparent = gst_object_get_parent (GST_OBJECT_CAST (msg->src));
       if (G_UNLIKELY (gst_object_has_ancestor (msg->src, GST_OBJECT_CAST
-                (group->suburidecodebin))
+                  (group->suburidecodebin)))) {
-            && GST_MESSAGE_TYPE (msg) == GST_MESSAGE_ERROR)) {
         GError *err;
         gchar *debug = NULL;
         GstMessage *new_msg;
@@ -2067,7 +2078,9 @@ gst_play_bin_handle_message (GstBin * bin, GstMessage * msg)
       if (srcparent)
         gst_object_unref (srcparent);
     }
+  }
 
+  if (msg)
     GST_BIN_CLASS (parent_class)->handle_message (bin, msg);
 }
 
@@ -2549,6 +2562,25 @@ no_more_pads_cb (GstElement * decodebin, GstSourceGroup * group)
     for (i = 0; i < GST_PLAY_SINK_TYPE_LAST; i++) {
       GstSourceSelect *select = &group->selector[i];
 
+      /* Wait for stream-changed messages on all selectors except
+       * the text selector because of the sparse nature of text streams.
+       */
+      if (select->sinkpad && select->type != GST_PLAY_SINK_TYPE_TEXT) {
+        GstStructure *s;
+        GstMessage *msg;
+        GstEvent *event;
+
+        s = gst_structure_new ("playbin2-stream-changed", "uri", G_TYPE_STRING,
+            group->uri, NULL);
+        if (group->suburi)
+          gst_structure_set (s, "suburi", G_TYPE_STRING, group->suburi, NULL);
+        msg = gst_message_new_element (GST_OBJECT_CAST (playbin), s);
+        event = gst_event_new_sink_message (msg);
+        g_atomic_int_inc (&group->stream_changed_pending);
+        gst_pad_send_event (select->sinkpad, event);
+        gst_message_unref (msg);
+      }
+
       if (select->srcpad) {
         GST_DEBUG_OBJECT (playbin, "unblocking %" GST_PTR_FORMAT,
             select->srcpad);
@@ -2820,6 +2852,8 @@ activate_group (GstPlayBin * playbin, GstSourceGroup * group, GstState target)
   GST_DEBUG_OBJECT (playbin, "activating group %p", group);
 
   GST_SOURCE_GROUP_LOCK (group);
+  group->stream_changed_pending = 0;
+
   if (group->uridecodebin) {
     GST_DEBUG_OBJECT (playbin, "reusing existing uridecodebin");
     uridecodebin = group->uridecodebin;