playbin: filter out buffering messages when switching uri

When switching URI from about-to-finish, playbin starts decoding the new
URI and the queue2 inside uridecodebin starts emitting buffering messages
immediately. However, the queue(s) inside playsink still have buffers to
play and the pipeline doesn't need to pause for buffering, so we should
not send those buffering messages up to the application, otherwise there
is an audible glitch caused by pausing the pipeline for a very short time.

https://bugzilla.gnome.org/show_bug.cgi?id=727255

diff --git a/gst/playback/gstplaybin2.c b/gst/playback/gstplaybin2.c
index 7b2c8cb..03e20df 100644 (file)
--- a/gst/playback/gstplaybin2.c
+++ b/gst/playback/gstplaybin2.c
@@ -367,6 +367,9 @@ struct _GstSourceGroup
   GMutex suburi_flushes_to_drop_lock;
   GSList *suburi_flushes_to_drop;
 
+  /* buffering message stored for after switching */
+  GstMessage *pending_buffering_msg;
+
   /* combiners for different streams */
   GstSourceCombine combiner[PLAYBIN_STREAM_LAST];
 };
@@ -1367,6 +1370,10 @@ free_group (GstPlayBin * playbin, GstSourceGroup * group)
   if (group->suburi_flushes_to_drop_lock.p)
     g_mutex_clear (&group->suburi_flushes_to_drop_lock);
   group->suburi_flushes_to_drop_lock.p = NULL;
+
+  if (group->pending_buffering_msg)
+    gst_message_unref (group->pending_buffering_msg);
+  group->pending_buffering_msg = NULL;
 }
 
 static void
@@ -2772,8 +2779,43 @@ gst_play_bin_handle_message (GstBin * bin, GstMessage * msg)
     }
   } else if (GST_MESSAGE_TYPE (msg) == GST_MESSAGE_STREAM_START) {
     GstSourceGroup *new_group = playbin->curr_group;
+    GstMessage *buffering_msg = NULL;
 
+    GST_SOURCE_GROUP_LOCK (new_group);
     new_group->stream_changed_pending = FALSE;
+    if (new_group->pending_buffering_msg) {
+      buffering_msg = new_group->pending_buffering_msg;
+      new_group->pending_buffering_msg = NULL;
+    }
+    GST_SOURCE_GROUP_UNLOCK (new_group);
+
+    GST_DEBUG_OBJECT (playbin, "Stream start from new group %p", new_group);
+
+    if (buffering_msg) {
+      GST_DEBUG_OBJECT (playbin, "Posting pending buffering message: %"
+          GST_PTR_FORMAT, buffering_msg);
+      GST_BIN_CLASS (parent_class)->handle_message (bin, buffering_msg);
+    }
+
+  } else if (GST_MESSAGE_TYPE (msg) == GST_MESSAGE_BUFFERING) {
+    GstSourceGroup *group = playbin->curr_group;
+    gboolean pending;
+
+    /* drop buffering messages from child queues while we are switching
+     * groups (because the application set a new uri in about-to-finish)
+     * if the playsink queue still has buffers to play */
+
+    GST_SOURCE_GROUP_LOCK (group);
+    pending = group->stream_changed_pending;
+
+    if (pending) {
+      GST_DEBUG_OBJECT (playbin, "Storing buffering message from pending group "
+          "%p %" GST_PTR_FORMAT, group, msg);
+      gst_message_replace (&group->pending_buffering_msg, msg);
+      gst_message_unref (msg);
+      msg = NULL;
+    }
+    GST_SOURCE_GROUP_UNLOCK (group);
   } 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 */
@@ -5383,11 +5425,11 @@ setup_next_source (GstPlayBin * playbin, GstState target)
   if (!new_group || !new_group->valid)
     goto no_next_group;
 
-  new_group->stream_changed_pending = TRUE;
-
   /* first unlink the current source, if any */
   old_group = playbin->curr_group;
   if (old_group && old_group->valid && old_group->active) {
+    new_group->stream_changed_pending = TRUE;
+
     gst_play_bin_update_cached_duration (playbin);
     /* unlink our pads with the sink */
     deactivate_group (playbin, old_group);