Avoid toggling default receive streams in WebRtcVideoChannel2.

webrtc/media/engine/webrtcvideoengine2.cc

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 410 matching lines @@
     // VP9 denoising is disabled by default.
     vp9_settings.denoisingOn = codec_default_denoising ? true : denoising;
     vp9_settings.frameDroppingOn = frame_dropping;
     return new rtc::RefCountedObject<
         webrtc::VideoEncoderConfig::Vp9EncoderSpecificSettings>(vp9_settings);
   }
   return nullptr;
 }
 
 DefaultUnsignalledSsrcHandler::DefaultUnsignalledSsrcHandler()
-    : default_recv_ssrc_(0), default_sink_(NULL) {}
+    : default_sink_(nullptr) {}
 
 UnsignalledSsrcHandler::Action DefaultUnsignalledSsrcHandler::OnUnsignalledSsrc(
     WebRtcVideoChannel2* channel,
     uint32_t ssrc) {
-  if (default_recv_ssrc_ != 0) {  // Already one default stream, so replace it.
-    channel->RemoveRecvStream(default_recv_ssrc_);
-    default_recv_ssrc_ = 0;
+  rtc::Optional<uint32_t> default_recv_ssrc =
+      channel->GetDefaultReceiveStreamSsrc();
+
+  if (default_recv_ssrc) {
+    LOG(LS_INFO) << "Destroying old default receive stream for SSRC=" << ssrc
+                 << ".";
+    channel->RemoveRecvStream(*default_recv_ssrc);
   }
 
   StreamParams sp;
   sp.ssrcs.push_back(ssrc);
   LOG(LS_INFO) << "Creating default receive stream for SSRC=" << ssrc << ".";
   if (!channel->AddRecvStream(sp, true)) {
     LOG(LS_WARNING) << "Could not create default receive stream.";
   }
 
   channel->SetSink(ssrc, default_sink_);
-  default_recv_ssrc_ = ssrc;
   return kDeliverPacket;
 }
 
 rtc::VideoSinkInterface<webrtc::VideoFrame>*
 DefaultUnsignalledSsrcHandler::GetDefaultSink() const {
   return default_sink_;
 }
 
 void DefaultUnsignalledSsrcHandler::SetDefaultSink(
-    VideoMediaChannel* channel,
+    WebRtcVideoChannel2* channel,
     rtc::VideoSinkInterface<webrtc::VideoFrame>* sink) {
   default_sink_ = sink;
-  if (default_recv_ssrc_ != 0) {
-    channel->SetSink(default_recv_ssrc_, default_sink_);
+  rtc::Optional<uint32_t> default_recv_ssrc =
+      channel->GetDefaultReceiveStreamSsrc();
+  if (default_recv_ssrc) {
+    channel->SetSink(*default_recv_ssrc, default_sink_);
   }
 }
 
 WebRtcVideoEngine2::WebRtcVideoEngine2()
     : initialized_(false),
       external_decoder_factory_(NULL),
       external_encoder_factory_(NULL) {
   LOG(LS_INFO) << "WebRtcVideoEngine2::WebRtcVideoEngine2()";
 }
 
@@ skipping 840 matching lines @@
 
   return true;
 }
 
 bool WebRtcVideoChannel2::SetSink(
     uint32_t ssrc,
     rtc::VideoSinkInterface<webrtc::VideoFrame>* sink) {
   LOG(LS_INFO) << "SetSink: ssrc:" << ssrc << " "
                << (sink ? "(ptr)" : "nullptr");
   if (ssrc == 0) {
+    // Do not hold |stream_crit_| here, since SetDefaultSink will call
+    // WebRtcVideoChannel2::GetDefaultReceiveStreamSsrc().
     default_unsignalled_ssrc_handler_.SetDefaultSink(this, sink);
     return true;
   }
 
   rtc::CritScope stream_lock(&stream_crit_);
   std::map<uint32_t, WebRtcVideoReceiveStream*>::iterator it =
       receive_streams_.find(ssrc);
   if (it == receive_streams_.end()) {
     return false;
   }
@@ skipping 188 matching lines @@
 
   // Speculative change to increase the outbound socket buffer size.
   // In b/15152257, we are seeing a significant number of packets discarded
   // due to lack of socket buffer space, although it's not yet clear what the
   // ideal value should be.
   MediaChannel::SetOption(NetworkInterface::ST_RTP,
                           rtc::Socket::OPT_SNDBUF,
                           kVideoRtpBufferSize);
 }
 
+rtc::Optional<uint32_t> WebRtcVideoChannel2::GetDefaultReceiveStreamSsrc() {
+  rtc::CritScope stream_lock(&stream_crit_);
+  rtc::Optional<uint32_t> ssrc;
+  for (auto it = receive_streams_.begin(); it != receive_streams_.end(); ++it) {
+    if (it->second->IsDefaultStream()) {
+      ssrc.emplace(it->first);
+      break;
+    }
+  }
+  return ssrc;
+}
+
 bool WebRtcVideoChannel2::SendRtp(const uint8_t* data,
                                   size_t len,
                                   const webrtc::PacketOptions& options) {
   rtc::CopyOnWriteBuffer packet(data, len, kMaxRtpPacketLen);
   rtc::PacketOptions rtc_options;
   rtc_options.packet_id = options.packet_id;
   return MediaChannel::SendPacket(&packet, rtc_options);
 }
 
 bool WebRtcVideoChannel2::SendRtcp(const uint8_t* data, size_t len) {
@@ skipping 1065 matching lines @@
         rtx_mapping[video_codecs[i].codec.id] !=
             ulpfec_config.red_payload_type) {
       video_codecs[i].rtx_payload_type = rtx_mapping[video_codecs[i].codec.id];
     }
   }
 
   return video_codecs;
 }
 
 }  // namespace cricket