rtpbasepayload: add auto-header-extension property

Using RTP header extensions is currently not convenient. Users have to
handle signals from the RTP payloader and instantiate the extension
element themselves, making it impossible to use with gst-launch.

Adding a property allowing the payloader to automatically try creating
extensions. This should help simple use cases and testing using
gst-launch.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/1022>

gst-libs/gst/rtp/gstrtpbasepayload.c

@@ -56,6 +56,7 @@ struct _GstRTPBasePayloadPrivate
   guint64 base_rtime_hz;
   guint64 running_time;
   gboolean scale_rtptime;
+  gboolean auto_hdr_ext;
 
   gint64 prop_max_ptime;
   gint64 caps_max_ptime;
@@ -105,6 +106,7 @@ static guint gst_rtp_base_payload_signals[LAST_SIGNAL] = { 0 };
 #define DEFAULT_SOURCE_INFO             FALSE
 #define DEFAULT_ONVIF_NO_RATE_CONTROL   FALSE
 #define DEFAULT_SCALE_RTPTIME           TRUE
+#define DEFAULT_AUTO_HEADER_EXTENSION   TRUE
 
 #define RTP_HEADER_EXT_ONE_BYTE_MAX_SIZE 16
 #define RTP_HEADER_EXT_TWO_BYTE_MAX_SIZE 256
@@ -129,6 +131,7 @@ enum
   PROP_SOURCE_INFO,
   PROP_ONVIF_NO_RATE_CONTROL,
   PROP_SCALE_RTPTIME,
+  PROP_AUTO_HEADER_EXTENSION,
   PROP_LAST
 };
 
@@ -208,6 +211,45 @@ gst_rtp_base_payload_get_instance_private (GstRTPBasePayload * self)
   return (G_STRUCT_MEMBER_P (self, private_offset));
 }
 
+static GstRTPHeaderExtension *
+gst_rtp_base_payload_request_extension_default (GstRTPBasePayload * payload,
+    guint ext_id, const gchar * uri)
+{
+  GstRTPHeaderExtension *ext = NULL;
+
+  if (!payload->priv->auto_hdr_ext)
+    return NULL;
+
+  ext = gst_rtp_header_extension_create_from_uri (uri);
+  if (ext) {
+    GST_DEBUG_OBJECT (payload,
+        "Automatically enabled extension %s for uri \'%s\'",
+        GST_ELEMENT_NAME (ext), uri);
+
+    gst_rtp_header_extension_set_id (ext, ext_id);
+  } else {
+    GST_DEBUG_OBJECT (payload,
+        "Didn't find any extension implementing uri \'%s\'", uri);
+  }
+
+  return ext;
+}
+
+static gboolean
+extension_accumulator (GSignalInvocationHint * ihint,
+    GValue * return_accu, const GValue * handler_return, gpointer data)
+{
+  gpointer ext;
+
+  /* Call default handler if user callback didn't create the extension */
+  ext = g_value_get_object (handler_return);
+  if (!ext)
+    return TRUE;
+
+  g_value_set_object (return_accu, ext);
+  return FALSE;
+}
+
 static void
 gst_rtp_base_payload_class_init (GstRTPBasePayloadClass * klass)
 {
@@ -381,6 +423,23 @@ gst_rtp_base_payload_class_init (GstRTPBasePayloadClass * klass)
           "Whether the RTP timestamp should be scaled with the rate (speed)",
           DEFAULT_SCALE_RTPTIME, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
+  /**
+   * GstRTPBasePayload:auto-header-extension:
+   *
+   * If enabled, the payloader will automatically try to enable all the
+   * RTP header extensions provided in the src caps, saving the application
+   * the need to handle these extensions manually using the
+   * GstRTPBasePayload::request-extension: signal.
+   *
+   * Since: 1.20
+   */
+  g_object_class_install_property (G_OBJECT_CLASS (klass),
+      PROP_AUTO_HEADER_EXTENSION, g_param_spec_boolean ("auto-header-extension",
+          "Automatic RTP header extension",
+          "Whether RTP header extensions should be automatically enabled, if an implementation is available",
+          DEFAULT_AUTO_HEADER_EXTENSION,
+          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
   /**
    * GstRTPBasePayload::add-extension:
    * @object: the #GstRTPBasePayload
@@ -412,7 +471,9 @@ gst_rtp_base_payload_class_init (GstRTPBasePayloadClass * klass)
    */
   gst_rtp_base_payload_signals[SIGNAL_REQUEST_EXTENSION] =
       g_signal_new_class_handler ("request-extension",
-      G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST, NULL, NULL, NULL, NULL,
+      G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
+      G_CALLBACK (gst_rtp_base_payload_request_extension_default),
+      extension_accumulator, NULL, NULL,
       GST_TYPE_RTP_HEADER_EXTENSION, 2, G_TYPE_UINT, G_TYPE_STRING);
 
   /**
@@ -491,6 +552,7 @@ gst_rtp_base_payload_init (GstRTPBasePayload * rtpbasepayload, gpointer g_class)
   rtpbasepayload->priv->base_rtime_hz = GST_BUFFER_OFFSET_NONE;
   rtpbasepayload->priv->onvif_no_rate_control = DEFAULT_ONVIF_NO_RATE_CONTROL;
   rtpbasepayload->priv->scale_rtptime = DEFAULT_SCALE_RTPTIME;
+  rtpbasepayload->priv->auto_hdr_ext = DEFAULT_AUTO_HEADER_EXTENSION;
 
   rtpbasepayload->media = NULL;
   rtpbasepayload->encoding_name = NULL;
@@ -1382,6 +1444,7 @@ gst_rtp_base_payload_negotiate (GstRTPBasePayload * payload)
               "for id %" G_GUINT64_FORMAT " and uri %s", ext,
               ext ? GST_OBJECT_NAME (ext) : "", ext_id, uri);
 
+          /* We require caller to set the appropriate extension if it's required */
           if (ext && gst_rtp_header_extension_get_id (ext) != ext_id) {
             g_warning ("\'request-extension\' signal provided an rtp header "
                 "extension for uri \'%s\' that does not match the requested "
@@ -1400,8 +1463,6 @@ gst_rtp_base_payload_negotiate (GstRTPBasePayload * payload)
             goto ext_out;
           }
 
-          /* We don't create an extension implementation by default and require
-           * the caller to set the appropriate extension if it's required */
           if (ext) {
             g_ptr_array_add (to_add, ext);
           }
@@ -2072,6 +2133,9 @@ gst_rtp_base_payload_set_property (GObject * object, guint prop_id,
     case PROP_SCALE_RTPTIME:
       priv->scale_rtptime = g_value_get_boolean (value);
       break;
+    case PROP_AUTO_HEADER_EXTENSION:
+      priv->auto_hdr_ext = g_value_get_boolean (value);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -2145,6 +2209,9 @@ gst_rtp_base_payload_get_property (GObject * object, guint prop_id,
     case PROP_SCALE_RTPTIME:
       g_value_set_boolean (value, priv->scale_rtptime);
       break;
+    case PROP_AUTO_HEADER_EXTENSION:
+      g_value_set_boolean (value, priv->auto_hdr_ext);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;