From ea1b10e4cacfdb3f9205a4a849bdbf6653ece92e Mon Sep 17 00:00:00 2001
From: Matt Staples <staples255@gmail.com>
Date: Wed, 1 Nov 2017 08:21:37 -0600
Subject: [PATCH] rtspsrc: Add a signal to allow outgoing messages to be
 modified or dropped

This feature allows applications to implement extensions to the RTSP
protocol, such as those defined in the ONVIF Streaming Specification.

https://bugzilla.gnome.org/show_bug.cgi?id=762884
---
 gst/rtsp/gstrtspsrc.c | 52 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/gst/rtsp/gstrtspsrc.c b/gst/rtsp/gstrtspsrc.c
index 086e2ea27d..7acb2cd052 100644
--- a/gst/rtsp/gstrtspsrc.c
+++ b/gst/rtsp/gstrtspsrc.c
@@ -125,6 +125,7 @@ enum
   SIGNAL_NEW_MANAGER,
   SIGNAL_REQUEST_RTCP_KEY,
   SIGNAL_ACCEPT_CERTIFICATE,
+  SIGNAL_BEFORE_SEND,
   LAST_SIGNAL
 };
 
@@ -437,6 +438,26 @@ select_stream_accum (GSignalInvocationHint * ihint,
   return myboolean;
 }
 
+static gboolean
+default_before_send (GstRTSPSrc * src, GstRTSPMessage * msg)
+{
+  GST_DEBUG_OBJECT (src, "default handler");
+  return TRUE;
+}
+
+static gboolean
+before_send_accum (GSignalInvocationHint * ihint,
+    GValue * return_accu, const GValue * handler_return, gpointer data)
+{
+  gboolean myboolean;
+
+  myboolean = g_value_get_boolean (handler_return);
+  g_value_set_boolean (return_accu, myboolean);
+
+  /* prevent send if FALSE */
+  return myboolean;
+}
+
 static void
 gst_rtspsrc_class_init (GstRTSPSrcClass * klass)
 {
@@ -921,6 +942,29 @@ gst_rtspsrc_class_init (GstRTSPSrcClass * klass)
       G_TYPE_BOOLEAN, 3, G_TYPE_TLS_CONNECTION, G_TYPE_TLS_CERTIFICATE,
       G_TYPE_TLS_CERTIFICATE_FLAGS);
 
+  /*
+   * GstRTSPSrc::before-send
+   * @rtspsrc: a #GstRTSPSrc
+   * @num: the stream number
+   *
+   * Emitted before each RTSP request is sent, in order to allow
+   * the application to modify send parameters or to skip the message entirely.
+   * This can be used, for example, to work with ONVIF Profile G servers,
+   * which need a different/additional range, rate-control, and intra/x
+   * parameters.
+   *
+   * Returns: %TRUE when the command should be sent, %FALSE when the
+   * command should be dropped.
+   *
+   * Since: 1.14
+   */
+  gst_rtspsrc_signals[SIGNAL_BEFORE_SEND] =
+      g_signal_new_class_handler ("before-send", G_TYPE_FROM_CLASS (klass),
+      G_SIGNAL_RUN_FIRST | G_SIGNAL_RUN_CLEANUP,
+      (GCallback) default_before_send, before_send_accum, NULL,
+      g_cclosure_marshal_generic, G_TYPE_BOOLEAN,
+      1, GST_TYPE_RTSP_MESSAGE | G_SIGNAL_TYPE_STATIC_SCOPE);
+
   gstelement_class->send_event = gst_rtspsrc_send_event;
   gstelement_class->provide_clock = gst_rtspsrc_provide_clock;
   gstelement_class->change_state = gst_rtspsrc_change_state;
@@ -5697,11 +5741,19 @@ gst_rtspsrc_try_send (GstRTSPSrc * src, GstRTSPConnInfo * conninfo,
 {
   GstRTSPResult res;
   gint try = 0;
+  gboolean allow_send = TRUE;
 
 again:
   if (!src->short_header)
     gst_rtsp_ext_list_before_send (src->extensions, request);
 
+  g_signal_emit (src, gst_rtspsrc_signals[SIGNAL_BEFORE_SEND], 0,
+      request, &allow_send);
+  if (!allow_send) {
+    GST_DEBUG_OBJECT (src, "skipping message, disabled by signal");
+    return GST_RTSP_OK;
+  }
+
   GST_DEBUG_OBJECT (src, "sending message");
 
   DEBUG_RTSP (src, request);