decodebin2: Forward event/queries for unlinked groups

When upstream events/queries reach sinkpads of unlinked groups (i.e.
no longer linked to the upstream demuxer), this patch attempts to find
the linked group and forward it upstream of that group.

This is done by adding upstream event/query probes on new group sinkpads
and then:
* Checking if the pad is linked or not (has a peer or not)
* If there is a peer, just let the event/query follow through normally
* If there is no peer, we find a pad to which to proxy it and return
  GST_PROBE_HANDLED if it succeeded (allowing the event/query to be properly
  returned to the initial called)

Note that this is definitely not thread-safe for the time being

https://bugzilla.gnome.org/show_bug.cgi?id=606382

1 files changed, 80 insertions, 0 deletions

diff --git a/gst/playback/gstdecodebin2.c b/gst/playback/gstdecodebin2.c
index 0cf65e6dc..bb1909570 100644
--- a/gst/playback/gstdecodebin2.c
+++ b/gst/playback/gstdecodebin2.c
@@ -2853,6 +2853,81 @@ pad_added_cb (GstElement * element, GstPad * pad, GstDecodeChain * chain)
   EXPOSE_UNLOCK (dbin);
 }
 
+static GstPadProbeReturn
+sink_pad_event_probe (GstPad * pad, GstPadProbeInfo * info, gpointer user_data)
+{
+  GstDecodeGroup *group = (GstDecodeGroup *) user_data;
+  GstEvent *event = GST_PAD_PROBE_INFO_EVENT (info);
+  GstPad *peer = gst_pad_get_peer (pad);
+  GstPadProbeReturn proberet = GST_PAD_PROBE_OK;
+
+  GST_DEBUG_OBJECT (pad, "Got upstream event %s", GST_EVENT_TYPE_NAME (event));
+
+  if (peer == NULL) {
+    GST_DEBUG_OBJECT (pad, "We are unlinked !");
+    if (group->parent && group->parent->next_groups) {
+      GstDecodeGroup *last_group =
+          g_list_last (group->parent->next_groups)->data;
+      GST_DEBUG_OBJECT (pad, "We could send the event to another group (%p)",
+          last_group);
+      /* Grab another sinkpad for that last group through which we will forward this event */
+      if (last_group->reqpads) {
+        GstPad *sinkpad = (GstPad *) last_group->reqpads->data;
+        GstPad *otherpeer = gst_pad_get_peer (sinkpad);
+        if (otherpeer) {
+          GST_DEBUG_OBJECT (otherpeer, "Attempting to forward event");
+          if (gst_pad_send_event (otherpeer, gst_event_ref (event))) {
+            proberet = GST_PAD_PROBE_HANDLED;
+          }
+          gst_object_unref (otherpeer);
+        }
+      } else
+        GST_DEBUG_OBJECT (pad, "No request pads, can't forward event");
+    }
+  } else
+    gst_object_unref (peer);
+
+  return proberet;
+}
+
+static GstPadProbeReturn
+sink_pad_query_probe (GstPad * pad, GstPadProbeInfo * info, gpointer user_data)
+{
+  GstDecodeGroup *group = (GstDecodeGroup *) user_data;
+  GstPad *peer = gst_pad_get_peer (pad);
+  GstQuery *query = GST_PAD_PROBE_INFO_QUERY (info);
+  GstPadProbeReturn proberet = GST_PAD_PROBE_OK;
+
+  GST_DEBUG_OBJECT (pad, "Got upstream query %s", GST_QUERY_TYPE_NAME (query));
+
+  if (peer == NULL) {
+    GST_DEBUG_OBJECT (pad, "We are unlinked !");
+    if (group->parent && group->parent->next_groups) {
+      GstDecodeGroup *last_group =
+          g_list_last (group->parent->next_groups)->data;
+      GST_DEBUG_OBJECT (pad, "We could send the query to another group");
+      /* Grab another sinkpad for that last group through which we will forward this event */
+      if (last_group->reqpads) {
+        GstPad *sinkpad = (GstPad *) last_group->reqpads->data;
+        GstPad *otherpeer = gst_pad_get_peer (sinkpad);
+        if (otherpeer) {
+          GST_DEBUG_OBJECT (otherpeer, "Attempting to forward query");
+          if (gst_pad_query (otherpeer, query)) {
+            proberet = GST_PAD_PROBE_HANDLED;
+          } else
+            GST_DEBUG ("FAILURE");
+          gst_object_unref (otherpeer);
+        } else
+          GST_DEBUG_OBJECT (sinkpad, "request pad not connected ??");
+      } else
+        GST_DEBUG_OBJECT (pad, "No request pads ???");
+    }
+  } else
+    gst_object_unref (peer);
+
+  return proberet;
+}
+
 static void
 pad_removed_cb (GstElement * element, GstPad * pad, GstDecodeChain * chain)
 {
@@ -3675,6 +3750,11 @@ gst_decode_group_control_demuxer_pad (GstDecodeGroup * group, GstPad * pad)
         sinkpad);
     goto error;
   }
+  gst_pad_add_probe (sinkpad, GST_PAD_PROBE_TYPE_EVENT_UPSTREAM,
+      sink_pad_event_probe, group, NULL);
+  gst_pad_add_probe (sinkpad, GST_PAD_PROBE_TYPE_QUERY_UPSTREAM,
+      sink_pad_query_probe, group, NULL);
+
   CHAIN_MUTEX_LOCK (group->parent);
   group->reqpads = g_list_prepend (group->reqpads, gst_object_ref (sinkpad));
   CHAIN_MUTEX_UNLOCK (group->parent);