From a2779ef36607c3f28e6903b5ed509e3db431b59b Mon Sep 17 00:00:00 2001
From: Mathieu Duponchelle <mathieu@centricular.com>
Date: Fri, 15 Mar 2019 16:47:35 +0100
Subject: [PATCH] webrtcbin: fix pt selection for FEC and RTX when BUNDLE

When we offer bundled media, payload types must be unique
across all bundled media, as they will be multiplexed in the
same session.
---
 ext/webrtc/gstwebrtcbin.c | 52 +++++++++++++++++++++++++++++++++++----
 1 file changed, 47 insertions(+), 5 deletions(-)

diff --git a/ext/webrtc/gstwebrtcbin.c b/ext/webrtc/gstwebrtcbin.c
index 76c99edf0d..9236753d1d 100644
--- a/ext/webrtc/gstwebrtcbin.c
+++ b/ext/webrtc/gstwebrtcbin.c
@@ -1946,7 +1946,8 @@ _add_fingerprint_to_media (GstWebRTCDTLSTransport * transport,
 static gboolean
 sdp_media_from_transceiver (GstWebRTCBin * webrtc, GstSDPMedia * media,
     GstWebRTCRTPTransceiver * trans, GstWebRTCSDPType type, guint media_idx,
-    GString * bundled_mids, guint bundle_idx, gboolean bundle_only)
+    GString * bundled_mids, guint bundle_idx, gboolean bundle_only,
+    GArray * reserved_pts)
 {
   /* TODO:
    * rtp header extensions
@@ -2028,14 +2029,14 @@ sdp_media_from_transceiver (GstWebRTCBin * webrtc, GstSDPMedia * media,
   }
 
   if (type == GST_WEBRTC_SDP_TYPE_OFFER) {
-    GArray *reserved_pts = g_array_new (FALSE, FALSE, sizeof (guint));
     const GstStructure *s = gst_caps_get_structure (caps, 0);
     gint clockrate = -1;
     gint rtx_target_pt;
     gint original_rtx_target_pt;        /* Workaround chrome bug: https://bugs.chromium.org/p/webrtc/issues/detail?id=6196 */
     guint rtx_target_ssrc = -1;
 
-    if (gst_structure_get_int (s, "payload", &rtx_target_pt))
+    if (gst_structure_get_int (s, "payload", &rtx_target_pt) &&
+        webrtc->bundle_policy == GST_WEBRTC_BUNDLE_POLICY_NONE)
       g_array_append_val (reserved_pts, rtx_target_pt);
 
     original_rtx_target_pt = rtx_target_pt;
@@ -2054,7 +2055,6 @@ sdp_media_from_transceiver (GstWebRTCBin * webrtc, GstSDPMedia * media,
     if (original_rtx_target_pt != rtx_target_pt)
       _pick_rtx_payload_types (webrtc, WEBRTC_TRANSCEIVER (trans), reserved_pts,
           clockrate, original_rtx_target_pt, rtx_target_ssrc, media);
-    g_array_free (reserved_pts, TRUE);
   }
 
   _media_add_ssrcs (media, caps, webrtc, WEBRTC_TRANSCEIVER (trans));
@@ -2084,6 +2084,34 @@ sdp_media_from_transceiver (GstWebRTCBin * webrtc, GstSDPMedia * media,
   return TRUE;
 }
 
+static void
+gather_pad_pt (GstWebRTCBinPad * pad, GArray * reserved_pts)
+{
+  if (pad->received_caps) {
+    GstStructure *s = gst_caps_get_structure (pad->received_caps, 0);
+    gint pt;
+
+    if (gst_structure_get_int (s, "payload", &pt)) {
+      g_array_append_val (reserved_pts, pt);
+    }
+  }
+}
+
+static GArray *
+gather_reserved_pts (GstWebRTCBin * webrtc)
+{
+  GstElement *element = GST_ELEMENT (webrtc);
+  GArray *reserved_pts = g_array_new (FALSE, FALSE, sizeof (guint));
+
+  GST_OBJECT_LOCK (webrtc);
+  g_list_foreach (element->sinkpads, (GFunc) gather_pad_pt, reserved_pts);
+  g_list_foreach (webrtc->priv->pending_pads, (GFunc) gather_pad_pt,
+      reserved_pts);
+  GST_OBJECT_UNLOCK (webrtc);
+
+  return reserved_pts;
+}
+
 /* TODO: use the options argument */
 static GstSDPMessage *
 _create_offer_task (GstWebRTCBin * webrtc, const GstStructure * options)
@@ -2093,6 +2121,7 @@ _create_offer_task (GstWebRTCBin * webrtc, const GstStructure * options)
   GString *bundled_mids = NULL;
   gchar *bundle_ufrag = NULL;
   gchar *bundle_pwd = NULL;
+  GArray *reserved_pts = NULL;
 
   gst_sdp_message_new (&ret);
 
@@ -2115,6 +2144,7 @@ _create_offer_task (GstWebRTCBin * webrtc, const GstStructure * options)
 
   if (webrtc->bundle_policy != GST_WEBRTC_BUNDLE_POLICY_NONE) {
     _generate_ice_credentials (&bundle_ufrag, &bundle_pwd);
+    reserved_pts = gather_reserved_pts (webrtc);
   }
 
   /* for each rtp transceiver */
@@ -2136,6 +2166,7 @@ _create_offer_task (GstWebRTCBin * webrtc, const GstStructure * options)
 
     /* FIXME: only needed when restarting ICE */
     if (webrtc->bundle_policy == GST_WEBRTC_BUNDLE_POLICY_NONE) {
+      reserved_pts = g_array_new (FALSE, FALSE, sizeof (guint));
       _generate_ice_credentials (&ufrag, &pwd);
     } else {
       ufrag = g_strdup (bundle_ufrag);
@@ -2147,8 +2178,11 @@ _create_offer_task (GstWebRTCBin * webrtc, const GstStructure * options)
     g_free (ufrag);
     g_free (pwd);
 
+    g_assert (reserved_pts != NULL);
+
     if (sdp_media_from_transceiver (webrtc, &media, trans,
-            GST_WEBRTC_SDP_TYPE_OFFER, i, bundled_mids, 0, bundle_only)) {
+            GST_WEBRTC_SDP_TYPE_OFFER, i, bundled_mids, 0, bundle_only,
+            reserved_pts)) {
       if (bundled_mids) {
         const gchar *mid = gst_sdp_media_get_attribute_val (&media, "mid");
 
@@ -2159,6 +2193,14 @@ _create_offer_task (GstWebRTCBin * webrtc, const GstStructure * options)
     } else {
       gst_sdp_media_uninit (&media);
     }
+
+    if (webrtc->bundle_policy == GST_WEBRTC_BUNDLE_POLICY_NONE) {
+      g_array_free (reserved_pts, TRUE);
+    }
+  }
+
+  if (webrtc->bundle_policy != GST_WEBRTC_BUNDLE_POLICY_NONE) {
+    g_array_free (reserved_pts, TRUE);
   }
 
   /* add data channel support */