webrtc: Configure transportsendbin latency internally

Add latency configuration logic to transportsendbin to
isolate it from the overall pipeline latency. That means that
it configures minimum latency internally based on the
latency query, and sends a latency event upstream that
matches.

Fixes https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/issues/1209

diff --git a/ext/webrtc/transportsendbin.c b/ext/webrtc/transportsendbin.c
index 727506ab6ea3ce8eeecab9627968ef7c65117be2..dc5c1ff0e2c682a839c841a6f1361317144f8c36 100644 (file)
--- a/ext/webrtc/transportsendbin.c
+++ b/ext/webrtc/transportsendbin.c
@@ -511,6 +511,85 @@ transport_send_bin_finalize (GObject * object)
   G_OBJECT_CLASS (parent_class)->finalize (object);
 }
 
+static gboolean
+gst_transport_send_bin_element_query (GstElement * element, GstQuery * query)
+{
+  gboolean ret = TRUE;
+  GstClockTime min_latency;
+
+  GST_LOG_OBJECT (element, "got query %s", GST_QUERY_TYPE_NAME (query));
+
+  switch (GST_QUERY_TYPE (query)) {
+    case GST_QUERY_LATENCY:
+      /* when latency is queried, use the result to configure our
+       * own latency internally, piggybacking off the global
+       * latency configuration sequence. */
+      GST_DEBUG_OBJECT (element, "handling latency query");
+
+      /* Call the parent query handler to actually get the query
+       * sent upstream */
+      ret =
+          GST_ELEMENT_CLASS (transport_send_bin_parent_class)->query
+          (GST_ELEMENT (element), query);
+      if (!ret)
+        break;
+
+      gst_query_parse_latency (query, NULL, &min_latency, NULL);
+
+      GST_DEBUG_OBJECT (element,
+          "got min latency %" GST_TIME_FORMAT, GST_TIME_ARGS (min_latency));
+
+      /* configure latency on elements */
+      /* Call the parent event handler, because our sub-class handler
+       * will drop the LATENCY event. We also don't need to that
+       * the latency configuration is valid (min < max), because
+       * the pipeline will do it when checking the query results */
+      if (GST_ELEMENT_CLASS (transport_send_bin_parent_class)->send_event
+          (GST_ELEMENT (element), gst_event_new_latency (min_latency))) {
+        GST_INFO_OBJECT (element, "configured latency of %" GST_TIME_FORMAT,
+            GST_TIME_ARGS (min_latency));
+      } else {
+        GST_WARNING_OBJECT (element,
+            "did not really configure latency of %" GST_TIME_FORMAT,
+            GST_TIME_ARGS (min_latency));
+      }
+
+      break;
+    default:
+      ret =
+          GST_ELEMENT_CLASS (transport_send_bin_parent_class)->query
+          (GST_ELEMENT (element), query);
+      break;
+  }
+
+  return ret;
+}
+
+static gboolean
+gst_transport_send_bin_element_event (GstElement * element, GstEvent * event)
+{
+  gboolean ret = TRUE;
+
+  GST_LOG_OBJECT (element, "got event %s", GST_EVENT_TYPE_NAME (event));
+
+  switch (GST_EVENT_TYPE (event)) {
+    case GST_EVENT_LATENCY:
+      /* Ignore the pipeline configured latency, we choose our own
+       * instead when the latency query happens, so that sending
+       * isn't affected by other parts of the pipeline */
+      GST_DEBUG_OBJECT (element, "Ignoring latency event from parent");
+      gst_event_unref (event);
+      break;
+    default:
+      ret =
+          GST_ELEMENT_CLASS (transport_send_bin_parent_class)->send_event
+          (GST_ELEMENT (element), event);
+      break;
+  }
+
+  return ret;
+}
+
 static void
 transport_send_bin_class_init (TransportSendBinClass * klass)
 {
@@ -535,6 +614,9 @@ transport_send_bin_class_init (TransportSendBinClass * klass)
   gobject_class->set_property = transport_send_bin_set_property;
   gobject_class->finalize = transport_send_bin_finalize;
 
+  element_class->send_event = gst_transport_send_bin_element_event;
+  element_class->query = gst_transport_send_bin_element_query;
+
   g_object_class_install_property (gobject_class,
       PROP_STREAM,
       g_param_spec_object ("stream", "Stream",