diff --git a/call/video_receive_stream.h b/call/video_receive_stream.h
index 395a3d2673..b5c1649aa9 100644
--- a/call/video_receive_stream.h
+++ b/call/video_receive_stream.h
@@ -19,6 +19,7 @@
 #include "api/call/transport.h"
 #include "api/rtp_headers.h"
 #include "api/rtpparameters.h"
+#include "api/rtpreceiverinterface.h"
 #include "api/video/video_content_type.h"
 #include "api/video/video_sink_interface.h"
 #include "api/video/video_timing.h"
@@ -239,6 +240,8 @@ class VideoReceiveStream {
   virtual void AddSecondarySink(RtpPacketSinkInterface* sink) = 0;
   virtual void RemoveSecondarySink(const RtpPacketSinkInterface* sink) = 0;
 
+  virtual std::vector<RtpSource> GetSources() const = 0;
+
  protected:
   virtual ~VideoReceiveStream() {}
 };
diff --git a/media/BUILD.gn b/media/BUILD.gn
index 241856f48e..8b6de8dcfb 100644
--- a/media/BUILD.gn
+++ b/media/BUILD.gn
@@ -487,6 +487,7 @@ if (rtc_include_tests) {
       ":rtc_audio_video",
       ":rtc_constants",
       ":rtc_data",
+      "../api/units:time_delta",
       "../api/video:video_frame_i420",
       "../modules/audio_processing:mocks",
       "../modules/rtp_rtcp",
diff --git a/media/base/fakemediaengine.h b/media/base/fakemediaengine.h
index 5d381f7b41..cdea187bf5 100644
--- a/media/base/fakemediaengine.h
+++ b/media/base/fakemediaengine.h
@@ -601,6 +601,10 @@ class FakeVideoMediaChannel : public RtpHelper<VideoMediaChannel> {
   void FillBitrateInfo(BandwidthEstimationInfo* bwe_info) override {}
   bool GetStats(VideoMediaInfo* info) override { return false; }
 
+  std::vector<webrtc::RtpSource> GetSources(uint32_t ssrc) const override {
+    return {};
+  }
+
  private:
   bool SetRecvCodecs(const std::vector<VideoCodec>& codecs) {
     if (fail_set_recv_codecs()) {
diff --git a/media/base/mediachannel.h b/media/base/mediachannel.h
index c7d8580dbc..44beb8fcf2 100644
--- a/media/base/mediachannel.h
+++ b/media/base/mediachannel.h
@@ -784,6 +784,8 @@ class VideoMediaChannel : public MediaChannel {
   virtual void FillBitrateInfo(BandwidthEstimationInfo* bwe_info) = 0;
   // Gets quality stats for the channel.
   virtual bool GetStats(VideoMediaInfo* info) = 0;
+
+  virtual std::vector<webrtc::RtpSource> GetSources(uint32_t ssrc) const = 0;
 };
 
 enum DataMessageType {
diff --git a/media/engine/fakewebrtccall.h b/media/engine/fakewebrtccall.h
index 8420f864ab..5bd335b949 100644
--- a/media/engine/fakewebrtccall.h
+++ b/media/engine/fakewebrtccall.h
@@ -210,6 +210,10 @@ class FakeVideoReceiveStream final : public webrtc::VideoReceiveStream {
   int GetNumAddedSecondarySinks() const;
   int GetNumRemovedSecondarySinks() const;
 
+  std::vector<webrtc::RtpSource> GetSources() const override {
+    return std::vector<webrtc::RtpSource>();
+  }
+
  private:
   // webrtc::VideoReceiveStream implementation.
   void Start() override;
diff --git a/media/engine/webrtcvideoengine.cc b/media/engine/webrtcvideoengine.cc
index 29b0eb9194..501f5de89d 100644
--- a/media/engine/webrtcvideoengine.cc
+++ b/media/engine/webrtcvideoengine.cc
@@ -1480,6 +1480,20 @@ absl::optional<uint32_t> WebRtcVideoChannel::GetDefaultReceiveStreamSsrc() {
   return ssrc;
 }
 
+std::vector<webrtc::RtpSource> WebRtcVideoChannel::GetSources(
+    uint32_t ssrc) const {
+  rtc::CritScope stream_lock(&stream_crit_);
+  auto it = receive_streams_.find(ssrc);
+  if (it == receive_streams_.end()) {
+    // TODO(bugs.webrtc.org/9781): Investigate standard compliance
+    // with sources for streams that has been removed.
+    RTC_LOG(LS_ERROR) << "Attempting to get contributing sources for SSRC:"
+                      << ssrc << " which doesn't exist.";
+    return {};
+  }
+  return it->second->GetSources();
+}
+
 bool WebRtcVideoChannel::SendRtp(const uint8_t* data,
                                  size_t len,
                                  const webrtc::PacketOptions& options) {
@@ -2202,6 +2216,12 @@ WebRtcVideoChannel::WebRtcVideoReceiveStream::GetSsrcs() const {
   return stream_params_.ssrcs;
 }
 
+std::vector<webrtc::RtpSource>
+WebRtcVideoChannel::WebRtcVideoReceiveStream::GetSources() {
+  RTC_DCHECK(stream_);
+  return stream_->GetSources();
+}
+
 absl::optional<uint32_t>
 WebRtcVideoChannel::WebRtcVideoReceiveStream::GetFirstPrimarySsrc() const {
   std::vector<uint32_t> primary_ssrcs;
diff --git a/media/engine/webrtcvideoengine.h b/media/engine/webrtcvideoengine.h
index 49ac1002bd..d949d786b7 100644
--- a/media/engine/webrtcvideoengine.h
+++ b/media/engine/webrtcvideoengine.h
@@ -175,6 +175,8 @@ class WebRtcVideoChannel : public VideoMediaChannel, public webrtc::Transport {
 
   static constexpr int kDefaultQpMax = 56;
 
+  std::vector<webrtc::RtpSource> GetSources(uint32_t ssrc) const override;
+
  private:
   class WebRtcVideoReceiveStream;
   struct VideoCodecSettings {
@@ -357,6 +359,8 @@ class WebRtcVideoChannel : public VideoMediaChannel, public webrtc::Transport {
 
     const std::vector<uint32_t>& GetSsrcs() const;
 
+    std::vector<webrtc::RtpSource> GetSources();
+
     // Does not return codecs, they are filled by the owning WebRtcVideoChannel.
     webrtc::RtpParameters GetRtpParameters() const;
 
diff --git a/media/engine/webrtcvideoengine_unittest.cc b/media/engine/webrtcvideoengine_unittest.cc
index a5a4f98a74..af4413871c 100644
--- a/media/engine/webrtcvideoengine_unittest.cc
+++ b/media/engine/webrtcvideoengine_unittest.cc
@@ -17,6 +17,7 @@
 #include "api/rtpparameters.h"
 #include "api/test/mock_video_decoder_factory.h"
 #include "api/test/mock_video_encoder_factory.h"
+#include "api/units/time_delta.h"
 #include "api/video_codecs/builtin_video_decoder_factory.h"
 #include "api/video_codecs/builtin_video_encoder_factory.h"
 #include "api/video_codecs/sdp_video_format.h"
@@ -965,6 +966,25 @@ TEST_F(WebRtcVideoEngineTest, RegisterH264DecoderIfSupported) {
   ASSERT_EQ(1u, decoder_factory_->decoders().size());
 }
 
+// Tests when GetSources is called with non-existing ssrc, it will return an
+// empty list of RtpSource without crashing.
+TEST_F(WebRtcVideoEngineTest, GetSourcesWithNonExistingSsrc) {
+  // Setup an recv stream with |kSsrc|.
+  encoder_factory_->AddSupportedVideoCodecType("VP8");
+  decoder_factory_->AddSupportedVideoCodecType(webrtc::SdpVideoFormat("VP8"));
+  cricket::VideoRecvParameters parameters;
+  parameters.codecs.push_back(GetEngineCodec("VP8"));
+  std::unique_ptr<VideoMediaChannel> channel(
+      SetRecvParamsWithSupportedCodecs(parameters.codecs));
+
+  EXPECT_TRUE(
+      channel->AddRecvStream(cricket::StreamParams::CreateLegacy(kSsrc)));
+
+  // Call GetSources with |kSsrc + 1| which doesn't exist.
+  std::vector<webrtc::RtpSource> sources = channel->GetSources(kSsrc + 1);
+  EXPECT_EQ(0u, sources.size());
+}
+
 TEST(WebRtcVideoEngineNewVideoCodecFactoryTest, NullFactories) {
   std::unique_ptr<webrtc::VideoEncoderFactory> encoder_factory;
   std::unique_ptr<webrtc::VideoDecoderFactory> decoder_factory;
@@ -1201,11 +1221,14 @@ TEST_F(WebRtcVideoEngineTest, DISABLED_RecreatesEncoderOnContentTypeChange) {
 class WebRtcVideoChannelBaseTest : public testing::Test {
  protected:
   WebRtcVideoChannelBaseTest()
-      : call_(webrtc::Call::Create(webrtc::Call::Config(&event_log_))),
-        engine_(webrtc::CreateBuiltinVideoEncoderFactory(),
+      : engine_(webrtc::CreateBuiltinVideoEncoderFactory(),
                 webrtc::CreateBuiltinVideoDecoderFactory()) {}
 
   virtual void SetUp() {
+    // One testcase calls SetUp in a loop, only create call_ once.
+    if (!call_) {
+      call_.reset(webrtc::Call::Create(webrtc::Call::Config(&event_log_)));
+    }
     cricket::MediaConfig media_config;
     // Disabling cpu overuse detection actually disables quality scaling too; it
     // implies DegradationPreference kMaintainResolution. Automatic scaling
@@ -1402,7 +1425,7 @@ class WebRtcVideoChannelBaseTest : public testing::Test {
   }
 
   webrtc::RtcEventLogNullImpl event_log_;
-  const std::unique_ptr<webrtc::Call> call_;
+  std::unique_ptr<webrtc::Call> call_;
   WebRtcVideoEngine engine_;
   std::unique_ptr<cricket::FakeVideoCapturerWithTaskQueue> video_capturer_;
   std::unique_ptr<cricket::FakeVideoCapturerWithTaskQueue> video_capturer_2_;
@@ -6696,4 +6719,145 @@ TEST_F(WebRtcVideoChannelSimulcastTest,
                           false);
 }
 
+// The fake clock needs to be initialize before the call.
+// So defer creating call in base class.
+class WebRtcVideoChannelTestWithClock : public WebRtcVideoChannelBaseTest {
+ public:
+  WebRtcVideoChannelTestWithClock() {
+    fake_clock_.AdvanceTime(webrtc::TimeDelta::ms(1));  // avoid time=0
+  }
+  rtc::ScopedFakeClock fake_clock_;
+};
+
+TEST_F(WebRtcVideoChannelTestWithClock, GetSources) {
+  uint8_t data1[] = {0x80, 0x00, 0x00, 0x00, 0x00, 0x00,
+                     0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+
+  EXPECT_EQ(0u, channel_->GetSources(kSsrc).size());
+
+  rtc::CopyOnWriteBuffer packet1(data1, sizeof(data1));
+  rtc::SetBE32(packet1.data() + 8, kSsrc);
+  channel_->SetSink(kDefaultReceiveSsrc, NULL);
+  EXPECT_TRUE(SetDefaultCodec());
+  EXPECT_TRUE(SetSend(true));
+  EXPECT_EQ(0, renderer_.num_rendered_frames());
+  channel_->OnPacketReceived(&packet1, rtc::PacketTime());
+
+  std::vector<webrtc::RtpSource> sources = channel_->GetSources(kSsrc);
+  EXPECT_EQ(1u, sources.size());
+  EXPECT_EQ(webrtc::RtpSourceType::SSRC, sources[0].source_type());
+  int64_t timestamp1 = sources[0].timestamp_ms();
+
+  // a new packet.
+  int64_t timeDeltaMs = 1;
+  fake_clock_.AdvanceTime(webrtc::TimeDelta::ms(timeDeltaMs));
+  channel_->OnPacketReceived(&packet1, rtc::PacketTime());
+  int64_t timestamp2 = channel_->GetSources(kSsrc)[0].timestamp_ms();
+  EXPECT_EQ(timestamp2, timestamp1 + timeDeltaMs);
+
+  // It only keeps 10s of history.
+  fake_clock_.AdvanceTime(webrtc::TimeDelta::seconds(10));
+  fake_clock_.AdvanceTime(webrtc::TimeDelta::ms(1));
+  EXPECT_EQ(0u, channel_->GetSources(kSsrc).size());
+}
+
+TEST_F(WebRtcVideoChannelTestWithClock, GetContributingSources) {
+  uint8_t data1[] = {0x81, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+
+  uint32_t kCsrc = 4321u;
+  EXPECT_EQ(0u, channel_->GetSources(kSsrc).size());
+  EXPECT_EQ(0u, channel_->GetSources(kCsrc).size());
+
+  rtc::CopyOnWriteBuffer packet1(data1, sizeof(data1));
+  rtc::SetBE32(packet1.data() + 8, kSsrc);
+  rtc::SetBE32(packet1.data() + 12, kCsrc);
+  channel_->SetSink(kDefaultReceiveSsrc, NULL);
+  EXPECT_TRUE(SetDefaultCodec());
+  EXPECT_TRUE(SetSend(true));
+  EXPECT_EQ(0, renderer_.num_rendered_frames());
+  channel_->OnPacketReceived(&packet1, rtc::PacketTime());
+
+  {
+    ASSERT_EQ(2u, channel_->GetSources(kSsrc).size());
+    EXPECT_EQ(0u, channel_->GetSources(kCsrc).size());
+    std::vector<webrtc::RtpSource> sources = channel_->GetSources(kSsrc);
+    EXPECT_EQ(sources[0].timestamp_ms(), sources[1].timestamp_ms());
+    // 1 SSRC and 1 CSRC.
+    EXPECT_EQ(1, std::count_if(sources.begin(), sources.end(),
+                               [](const webrtc::RtpSource& source) {
+                                 return source.source_type() ==
+                                        webrtc::RtpSourceType::SSRC;
+                               }));
+    EXPECT_EQ(1, std::count_if(sources.begin(), sources.end(),
+                               [](const webrtc::RtpSource& source) {
+                                 return source.source_type() ==
+                                        webrtc::RtpSourceType::CSRC;
+                               }));
+  }
+  int64_t timestamp1 = channel_->GetSources(kSsrc)[0].timestamp_ms();
+
+  // a new packet with only ssrc (i.e no csrc).
+  uint8_t data2[] = {0x80, 0x00, 0x00, 0x00, 0x00, 0x00,
+                     0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+  rtc::CopyOnWriteBuffer packet2(data2, sizeof(data2));
+  rtc::SetBE32(packet2.data() + 8, kSsrc);
+
+  int64_t timeDeltaMs = 1;
+  fake_clock_.AdvanceTime(webrtc::TimeDelta::ms(timeDeltaMs));
+  channel_->OnPacketReceived(&packet2, rtc::PacketTime());
+
+  {
+    ASSERT_EQ(2u, channel_->GetSources(kSsrc).size());
+    EXPECT_EQ(0u, channel_->GetSources(kCsrc).size());
+    std::vector<webrtc::RtpSource> sources = channel_->GetSources(kSsrc);
+    EXPECT_NE(sources[0].timestamp_ms(), sources[1].timestamp_ms());
+    // 1 SSRC and 1 CSRC.
+    EXPECT_EQ(1, std::count_if(sources.begin(), sources.end(),
+                               [](const webrtc::RtpSource& source) {
+                                 return source.source_type() ==
+                                        webrtc::RtpSourceType::SSRC;
+                               }));
+    EXPECT_EQ(1, std::count_if(sources.begin(), sources.end(),
+                               [](const webrtc::RtpSource& source) {
+                                 return source.source_type() ==
+                                        webrtc::RtpSourceType::CSRC;
+                               }));
+    auto ssrcSource = std::find_if(
+        sources.begin(), sources.end(), [](const webrtc::RtpSource& source) {
+          return source.source_type() == webrtc::RtpSourceType::SSRC;
+        });
+    auto csrcSource = std::find_if(
+        sources.begin(), sources.end(), [](const webrtc::RtpSource& source) {
+          return source.source_type() == webrtc::RtpSourceType::CSRC;
+        });
+
+    EXPECT_EQ(ssrcSource->timestamp_ms(), timestamp1 + timeDeltaMs);
+    EXPECT_EQ(csrcSource->timestamp_ms(), timestamp1);
+  }
+
+  // It only keeps 10s of history.
+  fake_clock_.AdvanceTime(webrtc::TimeDelta::seconds(10));
+
+  {
+    ASSERT_EQ(1u, channel_->GetSources(kSsrc).size());
+    EXPECT_EQ(0u, channel_->GetSources(kCsrc).size());
+    std::vector<webrtc::RtpSource> sources = channel_->GetSources(kSsrc);
+    EXPECT_EQ(1, std::count_if(sources.begin(), sources.end(),
+                               [](const webrtc::RtpSource& source) {
+                                 return source.source_type() ==
+                                        webrtc::RtpSourceType::SSRC;
+                               }));
+    EXPECT_EQ(0, std::count_if(sources.begin(), sources.end(),
+                               [](const webrtc::RtpSource& source) {
+                                 return source.source_type() ==
+                                        webrtc::RtpSourceType::CSRC;
+                               }));
+  }
+
+  fake_clock_.AdvanceTime(webrtc::TimeDelta::ms(1));
+  EXPECT_EQ(0u, channel_->GetSources(kSsrc).size());
+  EXPECT_EQ(0u, channel_->GetSources(kCsrc).size());
+}
+
 }  // namespace cricket
diff --git a/pc/peerconnection_integrationtest.cc b/pc/peerconnection_integrationtest.cc
index dd977b4d3f..3cf3e58407 100644
--- a/pc/peerconnection_integrationtest.cc
+++ b/pc/peerconnection_integrationtest.cc
@@ -4308,7 +4308,7 @@ TEST_P(PeerConnectionIntegrationTest, CodecNamesAreCaseInsensitive) {
   ASSERT_TRUE(ExpectNewFrames(media_expectations));
 }
 
-TEST_P(PeerConnectionIntegrationTest, GetSources) {
+TEST_P(PeerConnectionIntegrationTest, GetSourcesAudio) {
   ASSERT_TRUE(CreatePeerConnectionWrappers());
   ConnectFakeSignaling();
   caller()->AddAudioTrack();
@@ -4318,14 +4318,34 @@ TEST_P(PeerConnectionIntegrationTest, GetSources) {
   MediaExpectations media_expectations;
   media_expectations.CalleeExpectsSomeAudio(1);
   ASSERT_TRUE(ExpectNewFrames(media_expectations));
-  ASSERT_GT(callee()->pc()->GetReceivers().size(), 0u);
+  ASSERT_EQ(callee()->pc()->GetReceivers().size(), 1u);
   auto receiver = callee()->pc()->GetReceivers()[0];
   ASSERT_EQ(receiver->media_type(), cricket::MEDIA_TYPE_AUDIO);
-
-  auto contributing_sources = receiver->GetSources();
+  auto sources = receiver->GetSources();
   ASSERT_GT(receiver->GetParameters().encodings.size(), 0u);
   EXPECT_EQ(receiver->GetParameters().encodings[0].ssrc,
-            contributing_sources[0].source_id());
+            sources[0].source_id());
+  EXPECT_EQ(webrtc::RtpSourceType::SSRC, sources[0].source_type());
+}
+
+TEST_P(PeerConnectionIntegrationTest, GetSourcesVideo) {
+  ASSERT_TRUE(CreatePeerConnectionWrappers());
+  ConnectFakeSignaling();
+  caller()->AddVideoTrack();
+  caller()->CreateAndSetAndSignalOffer();
+  ASSERT_TRUE_WAIT(SignalingStateStable(), kDefaultTimeout);
+  // Wait for one video frame to be received by the callee.
+  MediaExpectations media_expectations;
+  media_expectations.CalleeExpectsSomeVideo(1);
+  ASSERT_TRUE(ExpectNewFrames(media_expectations));
+  ASSERT_EQ(callee()->pc()->GetReceivers().size(), 1u);
+  auto receiver = callee()->pc()->GetReceivers()[0];
+  ASSERT_EQ(receiver->media_type(), cricket::MEDIA_TYPE_VIDEO);
+  auto sources = receiver->GetSources();
+  ASSERT_GT(receiver->GetParameters().encodings.size(), 0u);
+  EXPECT_EQ(receiver->GetParameters().encodings[0].ssrc,
+            sources[0].source_id());
+  EXPECT_EQ(webrtc::RtpSourceType::SSRC, sources[0].source_type());
 }
 
 // Test that if a track is removed and added again with a different stream ID,
diff --git a/pc/rtpreceiver.cc b/pc/rtpreceiver.cc
index ae31f843d1..8ab08bf8f2 100644
--- a/pc/rtpreceiver.cc
+++ b/pc/rtpreceiver.cc
@@ -440,4 +440,12 @@ void VideoRtpReceiver::NotifyFirstPacketReceived() {
   received_first_packet_ = true;
 }
 
+std::vector<RtpSource> VideoRtpReceiver::GetSources() const {
+  if (!media_channel_ || !ssrc_ || stopped_) {
+    return {};
+  }
+  return worker_thread_->Invoke<std::vector<RtpSource>>(
+      RTC_FROM_HERE, [&] { return media_channel_->GetSources(*ssrc_); });
+}
+
 }  // namespace webrtc
diff --git a/pc/rtpreceiver.h b/pc/rtpreceiver.h
index 7f77d85bcd..85be8c258b 100644
--- a/pc/rtpreceiver.h
+++ b/pc/rtpreceiver.h
@@ -227,6 +227,8 @@ class VideoRtpReceiver : public rtc::RefCountedObject<RtpReceiverInternal> {
 
   int AttachmentId() const override { return attachment_id_; }
 
+  std::vector<RtpSource> GetSources() const override;
+
  private:
   class VideoRtpTrackSource : public VideoTrackSource {
    public:
diff --git a/video/rtp_video_stream_receiver.cc b/video/rtp_video_stream_receiver.cc
index 5939b524df..ecd62ae082 100644
--- a/video/rtp_video_stream_receiver.cc
+++ b/video/rtp_video_stream_receiver.cc
@@ -185,7 +185,7 @@ absl::optional<Syncable::Info> RtpVideoStreamReceiver::GetSyncInfo() const {
     return absl::nullopt;
   }
   {
-    rtc::CritScope lock(&last_seq_num_cs_);
+    rtc::CritScope lock(&rtp_sources_lock_);
     if (!last_received_rtp_timestamp_ || !last_received_rtp_system_time_ms_) {
       return absl::nullopt;
     }
@@ -283,13 +283,15 @@ void RtpVideoStreamReceiver::OnRtpPacket(const RtpPacketReceived& packet) {
   }
 
   if (!packet.recovered()) {
+    // TODO(nisse): Exclude out-of-order packets?
     int64_t now_ms = clock_->TimeInMilliseconds();
     {
-      rtc::CritScope lock(&last_seq_num_cs_);
-
-      // TODO(nisse): Exclude out-of-order packets?
+      rtc::CritScope cs(&rtp_sources_lock_);
       last_received_rtp_timestamp_ = packet.Timestamp();
       last_received_rtp_system_time_ms_ = now_ms;
+
+      std::vector<uint32_t> csrcs = packet.Csrcs();
+      contributing_sources_.Update(now_ms, csrcs);
     }
     // Periodically log the RTP header of incoming packets.
     if (now_ms - last_packet_log_ms_ > kPacketLogIntervalMs) {
@@ -671,4 +673,19 @@ void RtpVideoStreamReceiver::InsertSpsPpsIntoTracker(uint8_t payload_type) {
                              sprop_decoder.pps_nalu());
 }
 
+std::vector<webrtc::RtpSource> RtpVideoStreamReceiver::GetSources() const {
+  int64_t now_ms = rtc::TimeMillis();
+  std::vector<RtpSource> sources;
+  {
+    rtc::CritScope cs(&rtp_sources_lock_);
+    sources = contributing_sources_.GetSources(now_ms);
+    if (last_received_rtp_system_time_ms_ >=
+        now_ms - ContributingSources::kHistoryMs) {
+      sources.emplace_back(*last_received_rtp_system_time_ms_,
+                           config_.rtp.remote_ssrc, RtpSourceType::SSRC);
+    }
+  }
+  return sources;
+}
+
 }  // namespace webrtc
diff --git a/video/rtp_video_stream_receiver.h b/video/rtp_video_stream_receiver.h
index e67d66389e..54398871a8 100644
--- a/video/rtp_video_stream_receiver.h
+++ b/video/rtp_video_stream_receiver.h
@@ -29,6 +29,7 @@
 #include "modules/rtp_rtcp/include/rtp_header_extension_map.h"
 #include "modules/rtp_rtcp/include/rtp_rtcp.h"
 #include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
+#include "modules/rtp_rtcp/source/contributing_sources.h"
 #include "modules/video_coding/h264_sps_pps_tracker.h"
 #include "modules/video_coding/include/video_coding_defines.h"
 #include "modules/video_coding/packet_buffer.h"
@@ -134,6 +135,8 @@ class RtpVideoStreamReceiver : public RtpData,
   void AddSecondarySink(RtpPacketSinkInterface* sink);
   void RemoveSecondarySink(const RtpPacketSinkInterface* sink);
 
+  std::vector<webrtc::RtpSource> GetSources() const;
+
  private:
   // Entry point doing non-stats work for a received packet. Called
   // for the same packet both before and after RED decapsulation.
@@ -177,10 +180,6 @@ class RtpVideoStreamReceiver : public RtpData,
       RTC_GUARDED_BY(last_seq_num_cs_);
   video_coding::H264SpsPpsTracker tracker_;
 
-  absl::optional<uint32_t> last_received_rtp_timestamp_
-      RTC_GUARDED_BY(last_seq_num_cs_);
-  absl::optional<int64_t> last_received_rtp_system_time_ms_
-      RTC_GUARDED_BY(last_seq_num_cs_);
   std::map<uint8_t, VideoCodecType> pt_codec_type_;
   // TODO(johan): Remove pt_codec_params_ once
   // https://bugs.chromium.org/p/webrtc/issues/detail?id=6883 is resolved.
@@ -192,6 +191,15 @@ class RtpVideoStreamReceiver : public RtpData,
 
   std::vector<RtpPacketSinkInterface*> secondary_sinks_
       RTC_GUARDED_BY(worker_task_checker_);
+
+  // Info for GetSources and GetSyncInfo is updated on network or worker thread,
+  // queried on the worker thread.
+  rtc::CriticalSection rtp_sources_lock_;
+  ContributingSources contributing_sources_ RTC_GUARDED_BY(&rtp_sources_lock_);
+  absl::optional<uint32_t> last_received_rtp_timestamp_
+      RTC_GUARDED_BY(rtp_sources_lock_);
+  absl::optional<int64_t> last_received_rtp_system_time_ms_
+      RTC_GUARDED_BY(rtp_sources_lock_);
 };
 
 }  // namespace webrtc
diff --git a/video/video_receive_stream.cc b/video/video_receive_stream.cc
index b8f28963ea..7facf85dda 100644
--- a/video/video_receive_stream.cc
+++ b/video/video_receive_stream.cc
@@ -459,5 +459,10 @@ bool VideoReceiveStream::Decode() {
   }
   return true;
 }
+
+std::vector<webrtc::RtpSource> VideoReceiveStream::GetSources() const {
+  return rtp_video_stream_receiver_.GetSources();
+}
+
 }  // namespace internal
 }  // namespace webrtc
diff --git a/video/video_receive_stream.h b/video/video_receive_stream.h
index 5b1289443b..76ee2ed0fd 100644
--- a/video/video_receive_stream.h
+++ b/video/video_receive_stream.h
@@ -112,6 +112,8 @@ class VideoReceiveStream : public webrtc::VideoReceiveStream,
   uint32_t GetPlayoutTimestamp() const override;
   void SetMinimumPlayoutDelay(int delay_ms) override;
 
+  std::vector<webrtc::RtpSource> GetSources() const override;
+
  private:
   static void DecodeThreadFunction(void* ptr);
   bool Decode();