diff --git a/media/BUILD.gn b/media/BUILD.gn
index 55fc59c..84f938b 100644
--- a/media/BUILD.gn
+++ b/media/BUILD.gn
@@ -332,6 +332,8 @@
     "../rtc_base/experiments:rate_control_settings",
     "../rtc_base/synchronization:mutex",
     "../rtc_base/system:rtc_export",
+    "../rtc_base/task_utils:pending_task_safety_flag",
+    "../rtc_base/task_utils:to_queued_task",
     "../rtc_base/third_party/base64",
     "../system_wrappers",
     "../system_wrappers:metrics",
diff --git a/media/base/media_channel.h b/media/base/media_channel.h
index a947b47..95e4cc7 100644
--- a/media/base/media_channel.h
+++ b/media/base/media_channel.h
@@ -179,7 +179,7 @@
   // Sets the abstract interface class for sending RTP/RTCP data.
   virtual void SetInterface(NetworkInterface* iface)
       RTC_LOCKS_EXCLUDED(network_interface_mutex_);
-  // Called when a RTP packet is received.
+  // Called on the network when an RTP packet is received.
   virtual void OnPacketReceived(rtc::CopyOnWriteBuffer packet,
                                 int64_t packet_time_us) = 0;
   // Called when the socket's ability to send has changed.
diff --git a/media/engine/webrtc_video_engine.cc b/media/engine/webrtc_video_engine.cc
index 758e495..161c075 100644
--- a/media/engine/webrtc_video_engine.cc
+++ b/media/engine/webrtc_video_engine.cc
@@ -716,7 +716,8 @@
                     "WebRTC-Video-BufferPacketsWithUnknownSsrc")
               ? new UnhandledPacketsBuffer()
               : nullptr) {
-  RTC_DCHECK(thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+  network_thread_checker_.Detach();
 
   rtcp_receiver_report_ssrc_ = kDefaultRtcpReceiverReportSsrc;
   sending_ = false;
@@ -1684,67 +1685,75 @@
 
 void WebRtcVideoChannel::OnPacketReceived(rtc::CopyOnWriteBuffer packet,
                                           int64_t packet_time_us) {
-  RTC_DCHECK_RUN_ON(&thread_checker_);
-  const webrtc::PacketReceiver::DeliveryStatus delivery_result =
-      call_->Receiver()->DeliverPacket(webrtc::MediaType::VIDEO, packet,
-                                       packet_time_us);
-  switch (delivery_result) {
-    case webrtc::PacketReceiver::DELIVERY_OK:
-      return;
-    case webrtc::PacketReceiver::DELIVERY_PACKET_ERROR:
-      return;
-    case webrtc::PacketReceiver::DELIVERY_UNKNOWN_SSRC:
-      break;
-  }
+  RTC_DCHECK_RUN_ON(&network_thread_checker_);
+  // TODO(bugs.webrtc.org/11993): This code is very similar to what
+  // WebRtcVoiceMediaChannel::OnPacketReceived does. For maintainability and
+  // consistency it would be good to move the interaction with call_->Receiver()
+  // to a common implementation and provide a callback on the worker thread
+  // for the exception case (DELIVERY_UNKNOWN_SSRC) and how retry is attempted.
+  worker_thread_->PostTask(
+      ToQueuedTask(task_safety_, [this, packet, packet_time_us] {
+        RTC_DCHECK_RUN_ON(&thread_checker_);
+        const webrtc::PacketReceiver::DeliveryStatus delivery_result =
+            call_->Receiver()->DeliverPacket(webrtc::MediaType::VIDEO, packet,
+                                             packet_time_us);
+        switch (delivery_result) {
+          case webrtc::PacketReceiver::DELIVERY_OK:
+            return;
+          case webrtc::PacketReceiver::DELIVERY_PACKET_ERROR:
+            return;
+          case webrtc::PacketReceiver::DELIVERY_UNKNOWN_SSRC:
+            break;
+        }
 
-  uint32_t ssrc = 0;
-  if (!GetRtpSsrc(packet.cdata(), packet.size(), &ssrc)) {
-    return;
-  }
+        uint32_t ssrc = 0;
+        if (!GetRtpSsrc(packet.cdata(), packet.size(), &ssrc)) {
+          return;
+        }
 
-  if (unknown_ssrc_packet_buffer_) {
-    unknown_ssrc_packet_buffer_->AddPacket(ssrc, packet_time_us, packet);
-    return;
-  }
+        if (unknown_ssrc_packet_buffer_) {
+          unknown_ssrc_packet_buffer_->AddPacket(ssrc, packet_time_us, packet);
+          return;
+        }
 
-  if (discard_unknown_ssrc_packets_) {
-    return;
-  }
+        if (discard_unknown_ssrc_packets_) {
+          return;
+        }
 
-  int payload_type = 0;
-  if (!GetRtpPayloadType(packet.cdata(), packet.size(), &payload_type)) {
-    return;
-  }
+        int payload_type = 0;
+        if (!GetRtpPayloadType(packet.cdata(), packet.size(), &payload_type)) {
+          return;
+        }
 
-  // See if this payload_type is registered as one that usually gets its own
-  // SSRC (RTX) or at least is safe to drop either way (FEC). If it is, and
-  // it wasn't handled above by DeliverPacket, that means we don't know what
-  // stream it associates with, and we shouldn't ever create an implicit channel
-  // for these.
-  for (auto& codec : recv_codecs_) {
-    if (payload_type == codec.rtx_payload_type ||
-        payload_type == codec.ulpfec.red_rtx_payload_type ||
-        payload_type == codec.ulpfec.ulpfec_payload_type) {
-      return;
-    }
-  }
-  if (payload_type == recv_flexfec_payload_type_) {
-    return;
-  }
+        // See if this payload_type is registered as one that usually gets its
+        // own SSRC (RTX) or at least is safe to drop either way (FEC). If it
+        // is, and it wasn't handled above by DeliverPacket, that means we don't
+        // know what stream it associates with, and we shouldn't ever create an
+        // implicit channel for these.
+        for (auto& codec : recv_codecs_) {
+          if (payload_type == codec.rtx_payload_type ||
+              payload_type == codec.ulpfec.red_rtx_payload_type ||
+              payload_type == codec.ulpfec.ulpfec_payload_type) {
+            return;
+          }
+        }
+        if (payload_type == recv_flexfec_payload_type_) {
+          return;
+        }
 
-  switch (unsignalled_ssrc_handler_->OnUnsignalledSsrc(this, ssrc)) {
-    case UnsignalledSsrcHandler::kDropPacket:
-      return;
-    case UnsignalledSsrcHandler::kDeliverPacket:
-      break;
-  }
+        switch (unsignalled_ssrc_handler_->OnUnsignalledSsrc(this, ssrc)) {
+          case UnsignalledSsrcHandler::kDropPacket:
+            return;
+          case UnsignalledSsrcHandler::kDeliverPacket:
+            break;
+        }
 
-  if (call_->Receiver()->DeliverPacket(webrtc::MediaType::VIDEO, packet,
-                                       packet_time_us) !=
-      webrtc::PacketReceiver::DELIVERY_OK) {
-    RTC_LOG(LS_WARNING) << "Failed to deliver RTP packet on re-delivery.";
-    return;
-  }
+        if (call_->Receiver()->DeliverPacket(webrtc::MediaType::VIDEO, packet,
+                                             packet_time_us) !=
+            webrtc::PacketReceiver::DELIVERY_OK) {
+          RTC_LOG(LS_WARNING) << "Failed to deliver RTP packet on re-delivery.";
+        }
+      }));
 }
 
 void WebRtcVideoChannel::BackfillBufferedPackets(
diff --git a/media/engine/webrtc_video_engine.h b/media/engine/webrtc_video_engine.h
index 321a5a8..327c4e7 100644
--- a/media/engine/webrtc_video_engine.h
+++ b/media/engine/webrtc_video_engine.h
@@ -34,6 +34,7 @@
 #include "media/engine/unhandled_packets_buffer.h"
 #include "rtc_base/network_route.h"
 #include "rtc_base/synchronization/mutex.h"
+#include "rtc_base/task_utils/pending_task_safety_flag.h"
 #include "rtc_base/thread_annotations.h"
 #include "rtc_base/thread_checker.h"
 
@@ -554,11 +555,13 @@
       RTC_EXCLUSIVE_LOCKS_REQUIRED(thread_checker_);
 
   rtc::Thread* const worker_thread_;
+  webrtc::ScopedTaskSafety task_safety_;
+  rtc::ThreadChecker network_thread_checker_;
   rtc::ThreadChecker thread_checker_;
 
   uint32_t rtcp_receiver_report_ssrc_ RTC_GUARDED_BY(thread_checker_);
   bool sending_ RTC_GUARDED_BY(thread_checker_);
-  webrtc::Call* const call_ RTC_GUARDED_BY(thread_checker_);
+  webrtc::Call* const call_;
 
   DefaultUnsignalledSsrcHandler default_unsignalled_ssrc_handler_
       RTC_GUARDED_BY(thread_checker_);
diff --git a/media/engine/webrtc_video_engine_unittest.cc b/media/engine/webrtc_video_engine_unittest.cc
index 72fbc56..21d1160 100644
--- a/media/engine/webrtc_video_engine_unittest.cc
+++ b/media/engine/webrtc_video_engine_unittest.cc
@@ -6134,6 +6134,7 @@
   rtc::SetBE32(&data[8], ssrcs[0]);
   rtc::CopyOnWriteBuffer packet(data, kDataLength);
   channel_->OnPacketReceived(packet, /* packet_time_us */ -1);
+  rtc::Thread::Current()->ProcessMessages(0);
 
   ASSERT_EQ(1u, fake_call_->GetVideoReceiveStreams().size())
       << "No default receive stream created.";
@@ -6292,6 +6293,7 @@
   rtc::SetBE32(&data[8], kIncomingUnsignalledSsrc);
   rtc::CopyOnWriteBuffer packet(data, kDataLength);
   channel_->OnPacketReceived(packet, /* packet_time_us */ -1);
+  rtc::Thread::Current()->ProcessMessages(0);
 
   // The stream should now be created with the appropriate sync label.
   EXPECT_EQ(1u, fake_call_->GetVideoReceiveStreams().size());
@@ -6304,6 +6306,7 @@
   EXPECT_EQ(0u, fake_call_->GetVideoReceiveStreams().size());
 
   channel_->OnPacketReceived(packet, /* packet_time_us */ -1);
+  rtc::Thread::Current()->ProcessMessages(0);
   EXPECT_EQ(1u, fake_call_->GetVideoReceiveStreams().size());
   EXPECT_TRUE(
       fake_call_->GetVideoReceiveStreams()[0]->GetConfig().sync_group.empty());
@@ -6321,6 +6324,7 @@
   rtc::SetBE32(&data[8], kIncomingUnsignalledSsrc);
   rtc::CopyOnWriteBuffer packet(data, kDataLength);
   channel_->OnPacketReceived(packet, /* packet_time_us */ -1);
+  rtc::Thread::Current()->ProcessMessages(0);
 
   // Default receive stream created.
   const auto& receivers1 = fake_call_->GetVideoReceiveStreams();
@@ -6374,6 +6378,7 @@
   rtc::SetBE32(&data[8], kIncomingUnsignalledSsrc);
   rtc::CopyOnWriteBuffer packet(data, kDataLength);
   channel_->OnPacketReceived(packet, /* packet_time_us */ -1);
+  rtc::Thread::Current()->ProcessMessages(0);
 
   recv_stream = fake_call_->GetVideoReceiveStream(kIncomingUnsignalledSsrc);
   EXPECT_EQ(recv_stream->base_mininum_playout_delay_ms(), 200);
@@ -6411,6 +6416,7 @@
   rtc::SetBE32(&data[8], kIncomingUnsignalledSsrc);
   rtc::CopyOnWriteBuffer packet(data, kDataLength);
   channel_->OnPacketReceived(packet, /* packet_time_us */ -1);
+  rtc::Thread::Current()->ProcessMessages(0);
 
   if (expect_created_receive_stream) {
     EXPECT_EQ(1u, fake_call_->GetVideoReceiveStreams().size())
@@ -6498,6 +6504,7 @@
   cricket::SetRtpHeader(data, sizeof(data), rtpHeader);
   rtc::CopyOnWriteBuffer packet(data, sizeof(data));
   channel_->OnPacketReceived(packet, /* packet_time_us */ -1);
+  rtc::Thread::Current()->ProcessMessages(0);
   // VP8 packet should create default receive stream.
   ASSERT_EQ(1u, fake_call_->GetVideoReceiveStreams().size());
   FakeVideoReceiveStream* recv_stream = fake_call_->GetVideoReceiveStreams()[0];
@@ -6519,6 +6526,7 @@
   cricket::SetRtpHeader(data, sizeof(data), rtpHeader);
   rtc::CopyOnWriteBuffer packet2(data, sizeof(data));
   channel_->OnPacketReceived(packet2, /* packet_time_us */ -1);
+  rtc::Thread::Current()->ProcessMessages(0);
   // VP9 packet should replace the default receive SSRC.
   ASSERT_EQ(1u, fake_call_->GetVideoReceiveStreams().size());
   recv_stream = fake_call_->GetVideoReceiveStreams()[0];
@@ -6541,6 +6549,7 @@
   cricket::SetRtpHeader(data, sizeof(data), rtpHeader);
   rtc::CopyOnWriteBuffer packet3(data, sizeof(data));
   channel_->OnPacketReceived(packet3, /* packet_time_us */ -1);
+  rtc::Thread::Current()->ProcessMessages(0);
   // H264 packet should replace the default receive SSRC.
   ASSERT_EQ(1u, fake_call_->GetVideoReceiveStreams().size());
   recv_stream = fake_call_->GetVideoReceiveStreams()[0];
@@ -6580,6 +6589,7 @@
   cricket::SetRtpHeader(data, sizeof(data), rtp_header);
   rtc::CopyOnWriteBuffer packet(data, sizeof(data));
   channel_->OnPacketReceived(packet, /* packet_time_us */ -1);
+  rtc::Thread::Current()->ProcessMessages(0);
   // Default receive stream should be created.
   ASSERT_EQ(1u, fake_call_->GetVideoReceiveStreams().size());
   FakeVideoReceiveStream* recv_stream0 =
@@ -6598,6 +6608,7 @@
   cricket::SetRtpHeader(data, sizeof(data), rtp_header);
   packet.SetData(data, sizeof(data));
   channel_->OnPacketReceived(packet, /* packet_time_us */ -1);
+  rtc::Thread::Current()->ProcessMessages(0);
   // New default receive stream should be created, but old stream should remain.
   ASSERT_EQ(2u, fake_call_->GetVideoReceiveStreams().size());
   EXPECT_EQ(recv_stream0, fake_call_->GetVideoReceiveStreams()[0]);
@@ -8211,6 +8222,7 @@
   cricket::SetRtpHeader(data, sizeof(data), rtpHeader);
   rtc::CopyOnWriteBuffer packet(data, sizeof(data));
   channel_->OnPacketReceived(packet, /* packet_time_us */ -1);
+  rtc::Thread::Current()->ProcessMessages(0);
 
   // The |ssrc| member should still be unset.
   rtp_parameters = channel_->GetDefaultRtpReceiveParameters();
diff --git a/media/engine/webrtc_voice_engine.cc b/media/engine/webrtc_voice_engine.cc
index 72871d2..f6b4236 100644
--- a/media/engine/webrtc_voice_engine.cc
+++ b/media/engine/webrtc_voice_engine.cc
@@ -46,7 +46,10 @@
 #include "rtc_base/strings/audio_format_to_string.h"
 #include "rtc_base/strings/string_builder.h"
 #include "rtc_base/strings/string_format.h"
+#include "rtc_base/task_utils/pending_task_safety_flag.h"
+#include "rtc_base/task_utils/to_queued_task.h"
 #include "rtc_base/third_party/base64/base64.h"
+#include "rtc_base/thread.h"
 #include "rtc_base/trace_event.h"
 #include "system_wrappers/include/metrics.h"
 
@@ -267,7 +270,7 @@
 }
 
 WebRtcVoiceEngine::~WebRtcVoiceEngine() {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&worker_thread_checker_);
   RTC_LOG(LS_INFO) << "WebRtcVoiceEngine::~WebRtcVoiceEngine";
   if (initialized_) {
     StopAecDump();
@@ -281,7 +284,7 @@
 }
 
 void WebRtcVoiceEngine::Init() {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&worker_thread_checker_);
   RTC_LOG(LS_INFO) << "WebRtcVoiceEngine::Init";
 
   // TaskQueue expects to be created/destroyed on the same thread.
@@ -362,7 +365,7 @@
 
 rtc::scoped_refptr<webrtc::AudioState> WebRtcVoiceEngine::GetAudioState()
     const {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&worker_thread_checker_);
   return audio_state_;
 }
 
@@ -371,13 +374,13 @@
     const MediaConfig& config,
     const AudioOptions& options,
     const webrtc::CryptoOptions& crypto_options) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&worker_thread_checker_);
   return new WebRtcVoiceMediaChannel(this, config, options, crypto_options,
                                      call);
 }
 
 bool WebRtcVoiceEngine::ApplyOptions(const AudioOptions& options_in) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&worker_thread_checker_);
   RTC_LOG(LS_INFO) << "WebRtcVoiceEngine::ApplyOptions: "
                    << options_in.ToString();
   AudioOptions options = options_in;  // The options are modified below.
@@ -621,13 +624,13 @@
 }
 
 void WebRtcVoiceEngine::RegisterChannel(WebRtcVoiceMediaChannel* channel) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&worker_thread_checker_);
   RTC_DCHECK(channel);
   channels_.push_back(channel);
 }
 
 void WebRtcVoiceEngine::UnregisterChannel(WebRtcVoiceMediaChannel* channel) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&worker_thread_checker_);
   auto it = absl::c_find(channels_, channel);
   RTC_DCHECK(it != channels_.end());
   channels_.erase(it);
@@ -635,7 +638,7 @@
 
 bool WebRtcVoiceEngine::StartAecDump(webrtc::FileWrapper file,
                                      int64_t max_size_bytes) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&worker_thread_checker_);
 
   webrtc::AudioProcessing* ap = apm();
   if (!ap) {
@@ -650,7 +653,7 @@
 }
 
 void WebRtcVoiceEngine::StopAecDump() {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&worker_thread_checker_);
   webrtc::AudioProcessing* ap = apm();
   if (ap) {
     ap->DetachAecDump();
@@ -661,18 +664,18 @@
 }
 
 webrtc::AudioDeviceModule* WebRtcVoiceEngine::adm() {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&worker_thread_checker_);
   RTC_DCHECK(adm_);
   return adm_.get();
 }
 
 webrtc::AudioProcessing* WebRtcVoiceEngine::apm() const {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&worker_thread_checker_);
   return apm_.get();
 }
 
 webrtc::AudioState* WebRtcVoiceEngine::audio_state() {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&worker_thread_checker_);
   RTC_DCHECK(audio_state_);
   return audio_state_.get();
 }
@@ -814,7 +817,7 @@
   WebRtcAudioSendStream& operator=(const WebRtcAudioSendStream&) = delete;
 
   ~WebRtcAudioSendStream() override {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     ClearSource();
     call_->DestroyAudioSendStream(stream_);
   }
@@ -826,7 +829,7 @@
   }
 
   void SetRtpExtensions(const std::vector<webrtc::RtpExtension>& extensions) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     config_.rtp.extensions = extensions;
     rtp_parameters_.header_extensions = extensions;
     ReconfigureAudioSendStream();
@@ -838,7 +841,7 @@
   }
 
   void SetMid(const std::string& mid) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     if (config_.rtp.mid == mid) {
       return;
     }
@@ -848,14 +851,14 @@
 
   void SetFrameEncryptor(
       rtc::scoped_refptr<webrtc::FrameEncryptorInterface> frame_encryptor) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     config_.frame_encryptor = frame_encryptor;
     ReconfigureAudioSendStream();
   }
 
   void SetAudioNetworkAdaptorConfig(
       const absl::optional<std::string>& audio_network_adaptor_config) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     if (audio_network_adaptor_config_from_options_ ==
         audio_network_adaptor_config) {
       return;
@@ -867,7 +870,7 @@
   }
 
   bool SetMaxSendBitrate(int bps) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     RTC_DCHECK(config_.send_codec_spec);
     RTC_DCHECK(audio_codec_spec_);
     auto send_rate = ComputeSendBitrate(
@@ -890,32 +893,32 @@
                           int payload_freq,
                           int event,
                           int duration_ms) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     RTC_DCHECK(stream_);
     return stream_->SendTelephoneEvent(payload_type, payload_freq, event,
                                        duration_ms);
   }
 
   void SetSend(bool send) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     send_ = send;
     UpdateSendState();
   }
 
   void SetMuted(bool muted) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     RTC_DCHECK(stream_);
     stream_->SetMuted(muted);
     muted_ = muted;
   }
 
   bool muted() const {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     return muted_;
   }
 
   webrtc::AudioSendStream::Stats GetStats(bool has_remote_tracks) const {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     RTC_DCHECK(stream_);
     return stream_->GetStats(has_remote_tracks);
   }
@@ -925,7 +928,7 @@
   // This method is called on the libjingle worker thread.
   // TODO(xians): Make sure Start() is called only once.
   void SetSource(AudioSource* source) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     RTC_DCHECK(source);
     if (source_) {
       RTC_DCHECK(source_ == source);
@@ -940,7 +943,7 @@
   // callback will be received after this method.
   // This method is called on the libjingle worker thread.
   void ClearSource() {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     if (source_) {
       source_->SetSink(nullptr);
       source_ = nullptr;
@@ -976,7 +979,7 @@
   // Callback from the |source_| when it is going away. In case Start() has
   // never been called, this callback won't be triggered.
   void OnClose() override {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     // Set |source_| to nullptr to make sure no more callback will get into
     // the source.
     source_ = nullptr;
@@ -1043,14 +1046,14 @@
 
   void SetEncoderToPacketizerFrameTransformer(
       rtc::scoped_refptr<webrtc::FrameTransformerInterface> frame_transformer) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     config_.frame_transformer = std::move(frame_transformer);
     ReconfigureAudioSendStream();
   }
 
  private:
   void UpdateSendState() {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     RTC_DCHECK(stream_);
     RTC_DCHECK_EQ(1UL, rtp_parameters_.encodings.size());
     if (send_ && source_ != nullptr && rtp_parameters_.encodings[0].active) {
@@ -1061,7 +1064,7 @@
   }
 
   void UpdateAllowedBitrateRange() {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     // The order of precedence, from lowest to highest is:
     // - a reasonable default of 32kbps min/max
     // - fixed target bitrate from codec spec
@@ -1093,7 +1096,7 @@
 
   void UpdateSendCodecSpec(
       const webrtc::AudioSendStream::Config::SendCodecSpec& send_codec_spec) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     config_.send_codec_spec = send_codec_spec;
     auto info =
         config_.encoder_factory->QueryAudioEncoder(send_codec_spec.format);
@@ -1136,7 +1139,7 @@
   }
 
   void ReconfigureAudioSendStream() {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     RTC_DCHECK(stream_);
     stream_->Reconfigure(config_);
   }
@@ -1218,19 +1221,19 @@
   WebRtcAudioReceiveStream& operator=(const WebRtcAudioReceiveStream&) = delete;
 
   ~WebRtcAudioReceiveStream() {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     call_->DestroyAudioReceiveStream(stream_);
   }
 
   void SetFrameDecryptor(
       rtc::scoped_refptr<webrtc::FrameDecryptorInterface> frame_decryptor) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     config_.frame_decryptor = frame_decryptor;
     RecreateAudioReceiveStream();
   }
 
   void SetLocalSsrc(uint32_t local_ssrc) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     if (local_ssrc != config_.rtp.local_ssrc) {
       config_.rtp.local_ssrc = local_ssrc;
       RecreateAudioReceiveStream();
@@ -1239,7 +1242,7 @@
 
   void SetUseTransportCcAndRecreateStream(bool use_transport_cc,
                                           bool use_nack) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     config_.rtp.transport_cc = use_transport_cc;
     config_.rtp.nack.rtp_history_ms = use_nack ? kNackRtpHistoryMs : 0;
     ReconfigureAudioReceiveStream();
@@ -1247,21 +1250,21 @@
 
   void SetRtpExtensionsAndRecreateStream(
       const std::vector<webrtc::RtpExtension>& extensions) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     config_.rtp.extensions = extensions;
     RecreateAudioReceiveStream();
   }
 
   // Set a new payload type -> decoder map.
   void SetDecoderMap(const std::map<int, webrtc::SdpAudioFormat>& decoder_map) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     config_.decoder_map = decoder_map;
     ReconfigureAudioReceiveStream();
   }
 
   void MaybeRecreateAudioReceiveStream(
       const std::vector<std::string>& stream_ids) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     std::string sync_group;
     if (!stream_ids.empty()) {
       sync_group = stream_ids[0];
@@ -1277,13 +1280,13 @@
 
   webrtc::AudioReceiveStream::Stats GetStats(
       bool get_and_clear_legacy_stats) const {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     RTC_DCHECK(stream_);
     return stream_->GetStats(get_and_clear_legacy_stats);
   }
 
   void SetRawAudioSink(std::unique_ptr<webrtc::AudioSinkInterface> sink) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     // Need to update the stream's sink first; once raw_audio_sink_ is
     // reassigned, whatever was in there before is destroyed.
     stream_->SetSink(sink.get());
@@ -1291,13 +1294,13 @@
   }
 
   void SetOutputVolume(double volume) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     output_volume_ = volume;
     stream_->SetGain(volume);
   }
 
   void SetPlayout(bool playout) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     RTC_DCHECK(stream_);
     if (playout) {
       stream_->Start();
@@ -1307,7 +1310,7 @@
   }
 
   bool SetBaseMinimumPlayoutDelayMs(int delay_ms) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     RTC_DCHECK(stream_);
     if (stream_->SetBaseMinimumPlayoutDelayMs(delay_ms)) {
       // Memorize only valid delay because during stream recreation it will be
@@ -1324,13 +1327,13 @@
   }
 
   int GetBaseMinimumPlayoutDelayMs() const {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     RTC_DCHECK(stream_);
     return stream_->GetBaseMinimumPlayoutDelayMs();
   }
 
   std::vector<webrtc::RtpSource> GetSources() {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     RTC_DCHECK(stream_);
     return stream_->GetSources();
   }
@@ -1346,14 +1349,14 @@
 
   void SetDepacketizerToDecoderFrameTransformer(
       rtc::scoped_refptr<webrtc::FrameTransformerInterface> frame_transformer) {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     config_.frame_transformer = std::move(frame_transformer);
     ReconfigureAudioReceiveStream();
   }
 
  private:
   void RecreateAudioReceiveStream() {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     bool was_running = false;
     if (stream_) {
       was_running = stream_->IsRunning();
@@ -1368,7 +1371,7 @@
   }
 
   void ReconfigureAudioReceiveStream() {
-    RTC_DCHECK(worker_thread_checker_.IsCurrent());
+    RTC_DCHECK_RUN_ON(&worker_thread_checker_);
     RTC_DCHECK(stream_);
     stream_->Reconfigure(config_);
   }
@@ -1390,12 +1393,15 @@
     const webrtc::CryptoOptions& crypto_options,
     webrtc::Call* call)
     : VoiceMediaChannel(config),
+      worker_thread_(rtc::Thread::Current()),
       engine_(engine),
       call_(call),
       audio_config_(config.audio),
       crypto_options_(crypto_options),
       audio_red_for_opus_trial_enabled_(
           IsEnabled(call->trials(), "WebRTC-Audio-Red-For-Opus")) {
+  RTC_DCHECK_RUN_ON(worker_thread_);
+  network_thread_checker_.Detach();
   RTC_LOG(LS_VERBOSE) << "WebRtcVoiceMediaChannel::WebRtcVoiceMediaChannel";
   RTC_DCHECK(call);
   engine->RegisterChannel(this);
@@ -1403,7 +1409,7 @@
 }
 
 WebRtcVoiceMediaChannel::~WebRtcVoiceMediaChannel() {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_VERBOSE) << "WebRtcVoiceMediaChannel::~WebRtcVoiceMediaChannel";
   // TODO(solenberg): Should be able to delete the streams directly, without
   //                  going through RemoveNnStream(), once stream objects handle
@@ -1420,7 +1426,7 @@
 bool WebRtcVoiceMediaChannel::SetSendParameters(
     const AudioSendParameters& params) {
   TRACE_EVENT0("webrtc", "WebRtcVoiceMediaChannel::SetSendParameters");
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_INFO) << "WebRtcVoiceMediaChannel::SetSendParameters: "
                    << params.ToString();
   // TODO(pthatcher): Refactor this to be more clean now that we have
@@ -1466,7 +1472,7 @@
 bool WebRtcVoiceMediaChannel::SetRecvParameters(
     const AudioRecvParameters& params) {
   TRACE_EVENT0("webrtc", "WebRtcVoiceMediaChannel::SetRecvParameters");
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_INFO) << "WebRtcVoiceMediaChannel::SetRecvParameters: "
                    << params.ToString();
   // TODO(pthatcher): Refactor this to be more clean now that we have
@@ -1493,7 +1499,7 @@
 
 webrtc::RtpParameters WebRtcVoiceMediaChannel::GetRtpSendParameters(
     uint32_t ssrc) const {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   auto it = send_streams_.find(ssrc);
   if (it == send_streams_.end()) {
     RTC_LOG(LS_WARNING) << "Attempting to get RTP send parameters for stream "
@@ -1514,7 +1520,7 @@
 webrtc::RTCError WebRtcVoiceMediaChannel::SetRtpSendParameters(
     uint32_t ssrc,
     const webrtc::RtpParameters& parameters) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   auto it = send_streams_.find(ssrc);
   if (it == send_streams_.end()) {
     RTC_LOG(LS_WARNING) << "Attempting to set RTP send parameters for stream "
@@ -1569,7 +1575,7 @@
 
 webrtc::RtpParameters WebRtcVoiceMediaChannel::GetRtpReceiveParameters(
     uint32_t ssrc) const {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   webrtc::RtpParameters rtp_params;
   auto it = recv_streams_.find(ssrc);
   if (it == recv_streams_.end()) {
@@ -1589,7 +1595,7 @@
 
 webrtc::RtpParameters WebRtcVoiceMediaChannel::GetDefaultRtpReceiveParameters()
     const {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   webrtc::RtpParameters rtp_params;
   if (!default_sink_) {
     RTC_LOG(LS_WARNING) << "Attempting to get RTP parameters for the default, "
@@ -1606,7 +1612,7 @@
 }
 
 bool WebRtcVoiceMediaChannel::SetOptions(const AudioOptions& options) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_INFO) << "Setting voice channel options: " << options.ToString();
 
   // We retain all of the existing options, and apply the given ones
@@ -1632,7 +1638,7 @@
 
 bool WebRtcVoiceMediaChannel::SetRecvCodecs(
     const std::vector<AudioCodec>& codecs) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
 
   // Set the payload types to be used for incoming media.
   RTC_LOG(LS_INFO) << "Setting receive voice codecs.";
@@ -1714,7 +1720,7 @@
 // and receive streams may be reconfigured based on the new settings.
 bool WebRtcVoiceMediaChannel::SetSendCodecs(
     const std::vector<AudioCodec>& codecs) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   dtmf_payload_type_ = absl::nullopt;
   dtmf_payload_freq_ = -1;
 
@@ -1861,7 +1867,7 @@
 
 void WebRtcVoiceMediaChannel::SetPlayout(bool playout) {
   TRACE_EVENT0("webrtc", "WebRtcVoiceMediaChannel::SetPlayout");
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   if (playout_ == playout) {
     return;
   }
@@ -1904,7 +1910,7 @@
                                            bool enable,
                                            const AudioOptions* options,
                                            AudioSource* source) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   // TODO(solenberg): The state change should be fully rolled back if any one of
   //                  these calls fail.
   if (!SetLocalSource(ssrc, source)) {
@@ -1921,7 +1927,7 @@
 
 bool WebRtcVoiceMediaChannel::AddSendStream(const StreamParams& sp) {
   TRACE_EVENT0("webrtc", "WebRtcVoiceMediaChannel::AddSendStream");
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_INFO) << "AddSendStream: " << sp.ToString();
 
   uint32_t ssrc = sp.first_ssrc();
@@ -1960,7 +1966,7 @@
 
 bool WebRtcVoiceMediaChannel::RemoveSendStream(uint32_t ssrc) {
   TRACE_EVENT0("webrtc", "WebRtcVoiceMediaChannel::RemoveSendStream");
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_INFO) << "RemoveSendStream: " << ssrc;
 
   auto it = send_streams_.find(ssrc);
@@ -1986,7 +1992,7 @@
 
 bool WebRtcVoiceMediaChannel::AddRecvStream(const StreamParams& sp) {
   TRACE_EVENT0("webrtc", "WebRtcVoiceMediaChannel::AddRecvStream");
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_INFO) << "AddRecvStream: " << sp.ToString();
 
   if (!sp.has_ssrcs()) {
@@ -2032,7 +2038,7 @@
 
 bool WebRtcVoiceMediaChannel::RemoveRecvStream(uint32_t ssrc) {
   TRACE_EVENT0("webrtc", "WebRtcVoiceMediaChannel::RemoveRecvStream");
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_INFO) << "RemoveRecvStream: " << ssrc;
 
   const auto it = recv_streams_.find(ssrc);
@@ -2051,7 +2057,7 @@
 }
 
 void WebRtcVoiceMediaChannel::ResetUnsignaledRecvStream() {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_INFO) << "ResetUnsignaledRecvStream.";
   unsignaled_stream_params_ = StreamParams();
   // Create a copy since RemoveRecvStream will modify |unsignaled_recv_ssrcs_|.
@@ -2085,7 +2091,7 @@
 }
 
 bool WebRtcVoiceMediaChannel::SetOutputVolume(uint32_t ssrc, double volume) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_INFO) << rtc::StringFormat("WRVMC::%s({ssrc=%u}, {volume=%.2f})",
                                         __func__, ssrc, volume);
   const auto it = recv_streams_.find(ssrc);
@@ -2103,7 +2109,7 @@
 }
 
 bool WebRtcVoiceMediaChannel::SetDefaultOutputVolume(double volume) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   default_recv_volume_ = volume;
   for (uint32_t ssrc : unsignaled_recv_ssrcs_) {
     const auto it = recv_streams_.find(ssrc);
@@ -2120,7 +2126,7 @@
 
 bool WebRtcVoiceMediaChannel::SetBaseMinimumPlayoutDelayMs(uint32_t ssrc,
                                                            int delay_ms) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   std::vector<uint32_t> ssrcs(1, ssrc);
   // SSRC of 0 represents the default receive stream.
   if (ssrc == 0) {
@@ -2163,7 +2169,7 @@
 void WebRtcVoiceMediaChannel::SetFrameDecryptor(
     uint32_t ssrc,
     rtc::scoped_refptr<webrtc::FrameDecryptorInterface> frame_decryptor) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   auto matching_stream = recv_streams_.find(ssrc);
   if (matching_stream != recv_streams_.end()) {
     matching_stream->second->SetFrameDecryptor(frame_decryptor);
@@ -2177,7 +2183,7 @@
 void WebRtcVoiceMediaChannel::SetFrameEncryptor(
     uint32_t ssrc,
     rtc::scoped_refptr<webrtc::FrameEncryptorInterface> frame_encryptor) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   auto matching_stream = send_streams_.find(ssrc);
   if (matching_stream != send_streams_.end()) {
     matching_stream->second->SetFrameEncryptor(frame_encryptor);
@@ -2187,7 +2193,7 @@
 bool WebRtcVoiceMediaChannel::InsertDtmf(uint32_t ssrc,
                                          int event,
                                          int duration) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_INFO) << "WebRtcVoiceMediaChannel::InsertDtmf";
   if (!CanInsertDtmf()) {
     return false;
@@ -2210,78 +2216,88 @@
 
 void WebRtcVoiceMediaChannel::OnPacketReceived(rtc::CopyOnWriteBuffer packet,
                                                int64_t packet_time_us) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&network_thread_checker_);
+  // TODO(bugs.webrtc.org/11993): This code is very similar to what
+  // WebRtcVideoChannel::OnPacketReceived does. For maintainability and
+  // consistency it would be good to move the interaction with call_->Receiver()
+  // to a common implementation and provide a callback on the worker thread
+  // for the exception case (DELIVERY_UNKNOWN_SSRC) and how retry is attempted.
+  worker_thread_->PostTask(ToQueuedTask(task_safety_, [this, packet,
+                                                       packet_time_us] {
+    RTC_DCHECK_RUN_ON(worker_thread_);
 
-  webrtc::PacketReceiver::DeliveryStatus delivery_result =
-      call_->Receiver()->DeliverPacket(webrtc::MediaType::AUDIO, packet,
-                                       packet_time_us);
+    webrtc::PacketReceiver::DeliveryStatus delivery_result =
+        call_->Receiver()->DeliverPacket(webrtc::MediaType::AUDIO, packet,
+                                         packet_time_us);
 
-  if (delivery_result != webrtc::PacketReceiver::DELIVERY_UNKNOWN_SSRC) {
-    return;
-  }
-
-  // Create an unsignaled receive stream for this previously not received ssrc.
-  // If there already is N unsignaled receive streams, delete the oldest.
-  // See: https://bugs.chromium.org/p/webrtc/issues/detail?id=5208
-  uint32_t ssrc = 0;
-  if (!GetRtpSsrc(packet.cdata(), packet.size(), &ssrc)) {
-    return;
-  }
-  RTC_DCHECK(!absl::c_linear_search(unsignaled_recv_ssrcs_, ssrc));
-
-  // Add new stream.
-  StreamParams sp = unsignaled_stream_params_;
-  sp.ssrcs.push_back(ssrc);
-  RTC_LOG(LS_INFO) << "Creating unsignaled receive stream for SSRC=" << ssrc;
-  if (!AddRecvStream(sp)) {
-    RTC_LOG(LS_WARNING) << "Could not create unsignaled receive stream.";
-    return;
-  }
-  unsignaled_recv_ssrcs_.push_back(ssrc);
-  RTC_HISTOGRAM_COUNTS_LINEAR("WebRTC.Audio.NumOfUnsignaledStreams",
-                              unsignaled_recv_ssrcs_.size(), 1, 100, 101);
-
-  // Remove oldest unsignaled stream, if we have too many.
-  if (unsignaled_recv_ssrcs_.size() > kMaxUnsignaledRecvStreams) {
-    uint32_t remove_ssrc = unsignaled_recv_ssrcs_.front();
-    RTC_DLOG(LS_INFO) << "Removing unsignaled receive stream with SSRC="
-                      << remove_ssrc;
-    RemoveRecvStream(remove_ssrc);
-  }
-  RTC_DCHECK_GE(kMaxUnsignaledRecvStreams, unsignaled_recv_ssrcs_.size());
-
-  SetOutputVolume(ssrc, default_recv_volume_);
-  SetBaseMinimumPlayoutDelayMs(ssrc, default_recv_base_minimum_delay_ms_);
-
-  // The default sink can only be attached to one stream at a time, so we hook
-  // it up to the *latest* unsignaled stream we've seen, in order to support the
-  // case where the SSRC of one unsignaled stream changes.
-  if (default_sink_) {
-    for (uint32_t drop_ssrc : unsignaled_recv_ssrcs_) {
-      auto it = recv_streams_.find(drop_ssrc);
-      it->second->SetRawAudioSink(nullptr);
+    if (delivery_result != webrtc::PacketReceiver::DELIVERY_UNKNOWN_SSRC) {
+      return;
     }
-    std::unique_ptr<webrtc::AudioSinkInterface> proxy_sink(
-        new ProxySink(default_sink_.get()));
-    SetRawAudioSink(ssrc, std::move(proxy_sink));
-  }
 
-  delivery_result = call_->Receiver()->DeliverPacket(webrtc::MediaType::AUDIO,
-                                                     packet, packet_time_us);
-  RTC_DCHECK_NE(webrtc::PacketReceiver::DELIVERY_UNKNOWN_SSRC, delivery_result);
+    // Create an unsignaled receive stream for this previously not received
+    // ssrc. If there already is N unsignaled receive streams, delete the
+    // oldest. See: https://bugs.chromium.org/p/webrtc/issues/detail?id=5208
+    uint32_t ssrc = 0;
+    if (!GetRtpSsrc(packet.cdata(), packet.size(), &ssrc)) {
+      return;
+    }
+    RTC_DCHECK(!absl::c_linear_search(unsignaled_recv_ssrcs_, ssrc));
+
+    // Add new stream.
+    StreamParams sp = unsignaled_stream_params_;
+    sp.ssrcs.push_back(ssrc);
+    RTC_LOG(LS_INFO) << "Creating unsignaled receive stream for SSRC=" << ssrc;
+    if (!AddRecvStream(sp)) {
+      RTC_LOG(LS_WARNING) << "Could not create unsignaled receive stream.";
+      return;
+    }
+    unsignaled_recv_ssrcs_.push_back(ssrc);
+    RTC_HISTOGRAM_COUNTS_LINEAR("WebRTC.Audio.NumOfUnsignaledStreams",
+                                unsignaled_recv_ssrcs_.size(), 1, 100, 101);
+
+    // Remove oldest unsignaled stream, if we have too many.
+    if (unsignaled_recv_ssrcs_.size() > kMaxUnsignaledRecvStreams) {
+      uint32_t remove_ssrc = unsignaled_recv_ssrcs_.front();
+      RTC_DLOG(LS_INFO) << "Removing unsignaled receive stream with SSRC="
+                        << remove_ssrc;
+      RemoveRecvStream(remove_ssrc);
+    }
+    RTC_DCHECK_GE(kMaxUnsignaledRecvStreams, unsignaled_recv_ssrcs_.size());
+
+    SetOutputVolume(ssrc, default_recv_volume_);
+    SetBaseMinimumPlayoutDelayMs(ssrc, default_recv_base_minimum_delay_ms_);
+
+    // The default sink can only be attached to one stream at a time, so we hook
+    // it up to the *latest* unsignaled stream we've seen, in order to support
+    // the case where the SSRC of one unsignaled stream changes.
+    if (default_sink_) {
+      for (uint32_t drop_ssrc : unsignaled_recv_ssrcs_) {
+        auto it = recv_streams_.find(drop_ssrc);
+        it->second->SetRawAudioSink(nullptr);
+      }
+      std::unique_ptr<webrtc::AudioSinkInterface> proxy_sink(
+          new ProxySink(default_sink_.get()));
+      SetRawAudioSink(ssrc, std::move(proxy_sink));
+    }
+
+    delivery_result = call_->Receiver()->DeliverPacket(webrtc::MediaType::AUDIO,
+                                                       packet, packet_time_us);
+    RTC_DCHECK_NE(webrtc::PacketReceiver::DELIVERY_UNKNOWN_SSRC,
+                  delivery_result);
+  }));
 }
 
 void WebRtcVoiceMediaChannel::OnNetworkRouteChanged(
     const std::string& transport_name,
     const rtc::NetworkRoute& network_route) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   call_->GetTransportControllerSend()->OnNetworkRouteChanged(transport_name,
                                                              network_route);
   call_->OnAudioTransportOverheadChanged(network_route.packet_overhead);
 }
 
 bool WebRtcVoiceMediaChannel::MuteStream(uint32_t ssrc, bool muted) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   const auto it = send_streams_.find(ssrc);
   if (it == send_streams_.end()) {
     RTC_LOG(LS_WARNING) << "The specified ssrc " << ssrc << " is not in use.";
@@ -2319,7 +2335,7 @@
 }
 
 void WebRtcVoiceMediaChannel::OnReadyToSend(bool ready) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_VERBOSE) << "OnReadyToSend: " << (ready ? "Ready." : "Not ready.");
   call_->SignalChannelNetworkState(
       webrtc::MediaType::AUDIO,
@@ -2329,7 +2345,7 @@
 bool WebRtcVoiceMediaChannel::GetStats(VoiceMediaInfo* info,
                                        bool get_and_clear_legacy_stats) {
   TRACE_EVENT0("webrtc", "WebRtcVoiceMediaChannel::GetStats");
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_DCHECK(info);
 
   // Get SSRC and stats for each sender.
@@ -2460,7 +2476,7 @@
 void WebRtcVoiceMediaChannel::SetRawAudioSink(
     uint32_t ssrc,
     std::unique_ptr<webrtc::AudioSinkInterface> sink) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_VERBOSE) << "WebRtcVoiceMediaChannel::SetRawAudioSink: ssrc:"
                       << ssrc << " " << (sink ? "(ptr)" : "NULL");
   const auto it = recv_streams_.find(ssrc);
@@ -2473,7 +2489,7 @@
 
 void WebRtcVoiceMediaChannel::SetDefaultRawAudioSink(
     std::unique_ptr<webrtc::AudioSinkInterface> sink) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_LOG(LS_VERBOSE) << "WebRtcVoiceMediaChannel::SetDefaultRawAudioSink:";
   if (!unsignaled_recv_ssrcs_.empty()) {
     std::unique_ptr<webrtc::AudioSinkInterface> proxy_sink(
@@ -2497,7 +2513,7 @@
 void WebRtcVoiceMediaChannel::SetEncoderToPacketizerFrameTransformer(
     uint32_t ssrc,
     rtc::scoped_refptr<webrtc::FrameTransformerInterface> frame_transformer) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   auto matching_stream = send_streams_.find(ssrc);
   if (matching_stream == send_streams_.end()) {
     RTC_LOG(LS_INFO) << "Attempting to set frame transformer for SSRC:" << ssrc
@@ -2511,7 +2527,7 @@
 void WebRtcVoiceMediaChannel::SetDepacketizerToDecoderFrameTransformer(
     uint32_t ssrc,
     rtc::scoped_refptr<webrtc::FrameTransformerInterface> frame_transformer) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   auto matching_stream = recv_streams_.find(ssrc);
   if (matching_stream == recv_streams_.end()) {
     RTC_LOG(LS_INFO) << "Attempting to set frame transformer for SSRC:" << ssrc
@@ -2524,7 +2540,7 @@
 
 bool WebRtcVoiceMediaChannel::MaybeDeregisterUnsignaledRecvStream(
     uint32_t ssrc) {
-  RTC_DCHECK(worker_thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(worker_thread_);
   auto it = absl::c_find(unsignaled_recv_ssrcs_, ssrc);
   if (it != unsignaled_recv_ssrcs_.end()) {
     unsignaled_recv_ssrcs_.erase(it);
diff --git a/media/engine/webrtc_voice_engine.h b/media/engine/webrtc_voice_engine.h
index 81254e3..7cf184c 100644
--- a/media/engine/webrtc_voice_engine.h
+++ b/media/engine/webrtc_voice_engine.h
@@ -29,6 +29,7 @@
 #include "rtc_base/buffer.h"
 #include "rtc_base/network_route.h"
 #include "rtc_base/task_queue.h"
+#include "rtc_base/task_utils/pending_task_safety_flag.h"
 #include "rtc_base/thread_checker.h"
 
 namespace webrtc {
@@ -284,7 +285,9 @@
   // unsignaled anymore (i.e. it is now removed, or signaled), and return true.
   bool MaybeDeregisterUnsignaledRecvStream(uint32_t ssrc);
 
-  rtc::ThreadChecker worker_thread_checker_;
+  webrtc::TaskQueueBase* const worker_thread_;
+  webrtc::ScopedTaskSafety task_safety_;
+  rtc::ThreadChecker network_thread_checker_;
 
   WebRtcVoiceEngine* const engine_ = nullptr;
   std::vector<AudioCodec> send_codecs_;
diff --git a/media/engine/webrtc_voice_engine_unittest.cc b/media/engine/webrtc_voice_engine_unittest.cc
index 87678be..7fd1387 100644
--- a/media/engine/webrtc_voice_engine_unittest.cc
+++ b/media/engine/webrtc_voice_engine_unittest.cc
@@ -277,6 +277,7 @@
   void DeliverPacket(const void* data, int len) {
     rtc::CopyOnWriteBuffer packet(reinterpret_cast<const uint8_t*>(data), len);
     channel_->OnPacketReceived(packet, /* packet_time_us */ -1);
+    rtc::Thread::Current()->ProcessMessages(0);
   }
 
   void TearDown() override { delete channel_; }
@@ -3443,6 +3444,8 @@
       call_.GetAudioReceiveStream(kAudioSsrc);
   EXPECT_EQ(0, s->received_packets());
   channel_->OnPacketReceived(kPcmuPacket, /* packet_time_us */ -1);
+  rtc::Thread::Current()->ProcessMessages(0);
+
   EXPECT_EQ(1, s->received_packets());
 }
 
diff --git a/pc/channel.cc b/pc/channel.cc
index ff983d1..4368be3 100644
--- a/pc/channel.cc
+++ b/pc/channel.cc
@@ -155,7 +155,7 @@
 
   // Eats any outstanding messages or packets.
   alive_->SetNotAlive();
-  worker_thread_->Clear(this);
+  signaling_thread_->Clear(this);
   // The media channel is destroyed at the end of the destructor, since it
   // is a std::unique_ptr. The transport channel (rtp_transport) must outlive
   // the media channel.
@@ -534,13 +534,7 @@
     return;
   }
 
-  auto packet_buffer = parsed_packet.Buffer();
-
-  worker_thread_->PostTask(
-      ToQueuedTask(alive_, [this, packet_buffer, packet_time_us] {
-        RTC_DCHECK_RUN_ON(worker_thread());
-        media_channel_->OnPacketReceived(packet_buffer, packet_time_us);
-      }));
+  media_channel_->OnPacketReceived(parsed_packet.Buffer(), packet_time_us);
 }
 
 void BaseChannel::EnableMedia_w() {
diff --git a/pc/channel.h b/pc/channel.h
index 8240582..3d2d67f 100644
--- a/pc/channel.h
+++ b/pc/channel.h
@@ -314,8 +314,6 @@
   // ChannelInterface overrides
   RtpHeaderExtensions GetNegotiatedRtpHeaderExtensions() const override;
 
-  bool has_received_packet_ = false;
-
  private:
   bool ConnectToRtpTransport();
   void DisconnectFromRtpTransport();
@@ -333,6 +331,8 @@
 
   const std::string content_name_;
 
+  bool has_received_packet_ = false;
+
   // Won't be set when using raw packet transports. SDP-specific thing.
   // TODO(bugs.webrtc.org/12230): Written on network thread, read on
   // worker thread (at least).