Allow default audio receive channel to receive on any unsignalled SSRC.

talk/media/webrtc/webrtcvoiceengine.cc

 /*
  * libjingle
  * Copyright 2004 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 2427 matching lines @@
 
 void WebRtcVoiceMediaChannel::OnPacketReceived(
     rtc::Buffer* packet, const rtc::PacketTime& packet_time) {
   RTC_DCHECK(worker_thread_checker_.CalledOnValidThread());
 
   uint32_t ssrc = 0;
   if (!GetRtpSsrc(packet->data(), packet->size(), &ssrc)) {
     return;
   }
 
-  if (receive_channels_.empty()) {
-    // Create new channel, which will be the default receive channel.
+  // If we don't have a default channel, and the SSRC is unknown, create a
+  // default channel.
+  if (default_recv_ssrc_ == -1 && GetReceiveChannelId(ssrc) == -1) {
     StreamParams sp;
     sp.ssrcs.push_back(ssrc);
     LOG(LS_INFO) << "Creating default receive stream for SSRC=" << ssrc << ".";
     if (!AddRecvStream(sp)) {
       LOG(LS_WARNING) << "Could not create default receive stream.";
       return;
     }
     default_recv_ssrc_ = ssrc;
     SetOutputVolume(default_recv_ssrc_, default_recv_volume_);
   }
 
   // Forward packet to Call. If the SSRC is unknown we'll return after this.
   const webrtc::PacketTime webrtc_packet_time(packet_time.timestamp,
                                               packet_time.not_before);
   webrtc::PacketReceiver::DeliveryStatus delivery_result =
       call_->Receiver()->DeliverPacket(webrtc::MediaType::AUDIO,
           reinterpret_cast<const uint8_t*>(packet->data()), packet->size(),
           webrtc_packet_time);
   if (webrtc::PacketReceiver::DELIVERY_OK != delivery_result) {
-    return;
+    // If the SSRC is unknown here, route it to the default channel, if we have
+    // one. See: https://bugs.chromium.org/p/webrtc/issues/detail?id=5208
+    if (default_recv_ssrc_ == -1) {
+      return;
+    } else {
+      ssrc = default_recv_ssrc_;
+    }
   }
 
   // Find the channel to send this packet to. It must exist since webrtc::Call
   // was able to demux the packet.
   int channel = GetReceiveChannelId(ssrc);
   RTC_DCHECK(channel != -1);
 
   // Pass it off to the decoder.
   engine()->voe()->network()->ReceivedRTPPacket(
       channel, packet->data(), packet->size(), webrtc_packet_time);
@@ skipping 349 matching lines @@
       LOG(LS_WARNING) << "Unknown codec " << ToString(codec);
       return false;
     }
   }
   return true;
 }
 
 }  // namespace cricket
 
 #endif  // HAVE_WEBRTC_VOICE