Add thread/sequence checks to ModuleRtpRtcpImpl.

This ended up with needing to fork the current implementation
in order to not break downstream projects that were inheriting
from it. While those get updated, we'll move on with the forked
class.

Bug: webrtc:11581,b/8278269
Change-Id: I05b596cbda71aa5b72894c31a7119d17d4761883
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/175500
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31334}
diff --git a/modules/rtp_rtcp/BUILD.gn b/modules/rtp_rtcp/BUILD.gn
index c9a3161..eda27ba 100644
--- a/modules/rtp_rtcp/BUILD.gn
+++ b/modules/rtp_rtcp/BUILD.gn
@@ -186,6 +186,8 @@
     "source/rtp_rtcp_config.h",
     "source/rtp_rtcp_impl.cc",
     "source/rtp_rtcp_impl.h",
+    "source/rtp_rtcp_impl2.cc",
+    "source/rtp_rtcp_impl2.h",
     "source/rtp_sender.cc",
     "source/rtp_sender.h",
     "source/rtp_sender_audio.cc",
@@ -478,6 +480,7 @@
       "source/rtp_packet_history_unittest.cc",
       "source/rtp_packet_unittest.cc",
       "source/rtp_packetizer_av1_unittest.cc",
+      "source/rtp_rtcp_impl2_unittest.cc",
       "source/rtp_rtcp_impl_unittest.cc",
       "source/rtp_sender_audio_unittest.cc",
       "source/rtp_sender_unittest.cc",
diff --git a/modules/rtp_rtcp/include/rtp_rtcp.h b/modules/rtp_rtcp/include/rtp_rtcp.h
index f91f0d1..2db523c 100644
--- a/modules/rtp_rtcp/include/rtp_rtcp.h
+++ b/modules/rtp_rtcp/include/rtp_rtcp.h
@@ -53,8 +53,8 @@
 class RtpRtcp : public Module, public RtcpFeedbackSenderInterface {
  public:
   struct Configuration {
-    Configuration();
-    Configuration(Configuration&& rhs);
+    Configuration() = default;
+    Configuration(Configuration&& rhs) = default;
 
     // True for a audio version of the RTP/RTCP module object false will create
     // a video version.
diff --git a/modules/rtp_rtcp/source/rtcp_sender.cc b/modules/rtp_rtcp/source/rtcp_sender.cc
index 269a735..c12fb68 100644
--- a/modules/rtp_rtcp/source/rtcp_sender.cc
+++ b/modules/rtp_rtcp/source/rtcp_sender.cc
@@ -33,7 +33,7 @@
 #include "modules/rtp_rtcp/source/rtcp_packet/tmmbn.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/tmmbr.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/transport_feedback.h"
-#include "modules/rtp_rtcp/source/rtp_rtcp_impl.h"
+#include "modules/rtp_rtcp/source/rtp_rtcp_impl2.h"
 #include "modules/rtp_rtcp/source/time_util.h"
 #include "modules/rtp_rtcp/source/tmmbr_help.h"
 #include "rtc_base/checks.h"
@@ -123,7 +123,7 @@
       last_rr_ntp_secs(0),
       last_rr_ntp_frac(0),
       remote_sr(0),
-      module(nullptr) {}
+      receiver(nullptr) {}
 
 RTCPSender::FeedbackState::FeedbackState(const FeedbackState&) = default;
 
@@ -544,7 +544,7 @@
 
 std::unique_ptr<rtcp::RtcpPacket> RTCPSender::BuildTMMBR(
     const RtcpContext& ctx) {
-  if (ctx.feedback_state_.module == nullptr)
+  if (ctx.feedback_state_.receiver == nullptr)
     return nullptr;
   // Before sending the TMMBR check the received TMMBN, only an owner is
   // allowed to raise the bitrate:
@@ -558,7 +558,7 @@
   // will accuire criticalSectionRTCPReceiver_ is a potental deadlock but
   // since RTCPreceiver is not doing the reverse we should be fine
   std::vector<rtcp::TmmbItem> candidates =
-      ctx.feedback_state_.module->BoundingSet(&tmmbr_owner);
+      ctx.feedback_state_.receiver->BoundingSet(&tmmbr_owner);
 
   if (!candidates.empty()) {
     for (const auto& candidate : candidates) {
diff --git a/modules/rtp_rtcp/source/rtcp_sender.h b/modules/rtp_rtcp/source/rtcp_sender.h
index 7da2546..61081d4 100644
--- a/modules/rtp_rtcp/source/rtcp_sender.h
+++ b/modules/rtp_rtcp/source/rtcp_sender.h
@@ -38,10 +38,10 @@
 
 namespace webrtc {
 
-class ModuleRtpRtcpImpl;
+class RTCPReceiver;
 class RtcEventLog;
 
-class RTCPSender {
+class RTCPSender final {
  public:
   struct FeedbackState {
     FeedbackState();
@@ -61,7 +61,7 @@
     std::vector<rtcp::ReceiveTimeInfo> last_xr_rtis;
 
     // Used when generating TMMBR.
-    ModuleRtpRtcpImpl* module;
+    RTCPReceiver* receiver;
   };
 
   explicit RTCPSender(const RtpRtcp::Configuration& config);
diff --git a/modules/rtp_rtcp/source/rtcp_sender_unittest.cc b/modules/rtp_rtcp/source/rtcp_sender_unittest.cc
index 754ad89..d187b16 100644
--- a/modules/rtp_rtcp/source/rtcp_sender_unittest.cc
+++ b/modules/rtp_rtcp/source/rtcp_sender_unittest.cc
@@ -18,7 +18,7 @@
 #include "modules/rtp_rtcp/source/rtcp_packet/bye.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/common_header.h"
 #include "modules/rtp_rtcp/source/rtp_packet_received.h"
-#include "modules/rtp_rtcp/source/rtp_rtcp_impl.h"
+#include "modules/rtp_rtcp/source/rtp_rtcp_impl2.h"
 #include "modules/rtp_rtcp/source/time_util.h"
 #include "rtc_base/rate_limiter.h"
 #include "test/gmock.h"
@@ -77,7 +77,7 @@
         receive_statistics_(ReceiveStatistics::Create(&clock_)),
         retransmission_rate_limiter_(&clock_, 1000) {
     RtpRtcp::Configuration configuration = GetDefaultConfig();
-    rtp_rtcp_impl_.reset(new ModuleRtpRtcpImpl(configuration));
+    rtp_rtcp_impl_.reset(new ModuleRtpRtcpImpl2(configuration));
     rtcp_sender_.reset(new RTCPSender(configuration));
     rtcp_sender_->SetRemoteSSRC(kRemoteSsrc);
     rtcp_sender_->SetTimestampOffset(kStartRtpTimestamp);
@@ -115,7 +115,7 @@
   SimulatedClock clock_;
   TestTransport test_transport_;
   std::unique_ptr<ReceiveStatistics> receive_statistics_;
-  std::unique_ptr<ModuleRtpRtcpImpl> rtp_rtcp_impl_;
+  std::unique_ptr<ModuleRtpRtcpImpl2> rtp_rtcp_impl_;
   std::unique_ptr<RTCPSender> rtcp_sender_;
   RateLimiter retransmission_rate_limiter_;
 };
diff --git a/modules/rtp_rtcp/source/rtp_rtcp_impl.cc b/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
index 07a0485..0bd37eb 100644
--- a/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
+++ b/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
@@ -48,14 +48,6 @@
           &packet_history,
           config.paced_sender ? config.paced_sender : &non_paced_sender) {}
 
-RtpRtcp::Configuration::Configuration() = default;
-RtpRtcp::Configuration::Configuration(Configuration&& rhs) = default;
-
-std::unique_ptr<RtpRtcp> RtpRtcp::Create(const Configuration& configuration) {
-  RTC_DCHECK(configuration.clock);
-  return std::make_unique<ModuleRtpRtcpImpl>(configuration);
-}
-
 ModuleRtpRtcpImpl::ModuleRtpRtcpImpl(const Configuration& configuration)
     : rtcp_sender_(configuration),
       rtcp_receiver_(configuration, this),
@@ -312,7 +304,7 @@
     state.send_bitrate =
         rtp_sender_->packet_sender.GetSendRates().Sum().bps<uint32_t>();
   }
-  state.module = this;
+  state.receiver = &rtcp_receiver_;
 
   LastReceivedNTP(&state.last_rr_ntp_secs, &state.last_rr_ntp_frac,
                   &state.remote_sr);
@@ -793,11 +785,6 @@
   return true;
 }
 
-// Called from RTCPsender.
-std::vector<rtcp::TmmbItem> ModuleRtpRtcpImpl::BoundingSet(bool* tmmbr_owner) {
-  return rtcp_receiver_.BoundingSet(tmmbr_owner);
-}
-
 void ModuleRtpRtcpImpl::set_rtt_ms(int64_t rtt_ms) {
   {
     rtc::CritScope cs(&critical_section_rtt_);
diff --git a/modules/rtp_rtcp/source/rtp_rtcp_impl.h b/modules/rtp_rtcp/source/rtp_rtcp_impl.h
index debb433..2d07060 100644
--- a/modules/rtp_rtcp/source/rtp_rtcp_impl.h
+++ b/modules/rtp_rtcp/source/rtp_rtcp_impl.h
@@ -42,6 +42,7 @@
 struct PacedPacketInfo;
 struct RTPVideoHeader;
 
+// DEPRECATED.
 class ModuleRtpRtcpImpl : public RtpRtcp, public RTCPReceiver::ModuleRtpRtcp {
  public:
   explicit ModuleRtpRtcpImpl(const RtpRtcp::Configuration& configuration);
@@ -257,8 +258,6 @@
                        uint32_t* NTPfrac,
                        uint32_t* remote_sr) const;
 
-  std::vector<rtcp::TmmbItem> BoundingSet(bool* tmmbr_owner);
-
   void BitrateSent(uint32_t* total_rate,
                    uint32_t* video_rate,
                    uint32_t* fec_rate,
diff --git a/modules/rtp_rtcp/source/rtp_rtcp_impl2.cc b/modules/rtp_rtcp/source/rtp_rtcp_impl2.cc
new file mode 100644
index 0000000..c8f10ac
--- /dev/null
+++ b/modules/rtp_rtcp/source/rtp_rtcp_impl2.cc
@@ -0,0 +1,837 @@
+/*
+ *  Copyright (c) 2012 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.
+ */
+
+#include "modules/rtp_rtcp/source/rtp_rtcp_impl2.h"
+
+#include <string.h>
+
+#include <algorithm>
+#include <cstdint>
+#include <memory>
+#include <set>
+#include <string>
+#include <utility>
+
+#include "api/transport/field_trial_based_config.h"
+#include "modules/rtp_rtcp/source/rtcp_packet/dlrr.h"
+#include "modules/rtp_rtcp/source/rtp_rtcp_config.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
+
+#ifdef _WIN32
+// Disable warning C4355: 'this' : used in base member initializer list.
+#pragma warning(disable : 4355)
+#endif
+
+namespace webrtc {
+namespace {
+const int64_t kRtpRtcpMaxIdleTimeProcessMs = 5;
+const int64_t kRtpRtcpRttProcessTimeMs = 1000;
+const int64_t kRtpRtcpBitrateProcessTimeMs = 10;
+const int64_t kDefaultExpectedRetransmissionTimeMs = 125;
+}  // namespace
+
+ModuleRtpRtcpImpl2::RtpSenderContext::RtpSenderContext(
+    const RtpRtcp::Configuration& config)
+    : packet_history(config.clock, config.enable_rtx_padding_prioritization),
+      packet_sender(config, &packet_history),
+      non_paced_sender(&packet_sender),
+      packet_generator(
+          config,
+          &packet_history,
+          config.paced_sender ? config.paced_sender : &non_paced_sender) {}
+
+std::unique_ptr<RtpRtcp> RtpRtcp::Create(const Configuration& configuration) {
+  RTC_DCHECK(configuration.clock);
+  return std::make_unique<ModuleRtpRtcpImpl2>(configuration);
+}
+
+ModuleRtpRtcpImpl2::ModuleRtpRtcpImpl2(const Configuration& configuration)
+    : rtcp_sender_(configuration),
+      rtcp_receiver_(configuration, this),
+      clock_(configuration.clock),
+      last_bitrate_process_time_(clock_->TimeInMilliseconds()),
+      last_rtt_process_time_(clock_->TimeInMilliseconds()),
+      next_process_time_(clock_->TimeInMilliseconds() +
+                         kRtpRtcpMaxIdleTimeProcessMs),
+      packet_overhead_(28),  // IPV4 UDP.
+      nack_last_time_sent_full_ms_(0),
+      nack_last_seq_number_sent_(0),
+      remote_bitrate_(configuration.remote_bitrate_estimator),
+      rtt_stats_(configuration.rtt_stats),
+      rtt_ms_(0) {
+  process_thread_checker_.Detach();
+  if (!configuration.receiver_only) {
+    rtp_sender_ = std::make_unique<RtpSenderContext>(configuration);
+    // Make sure rtcp sender use same timestamp offset as rtp sender.
+    rtcp_sender_.SetTimestampOffset(
+        rtp_sender_->packet_generator.TimestampOffset());
+  }
+
+  // Set default packet size limit.
+  // TODO(nisse): Kind-of duplicates
+  // webrtc::VideoSendStream::Config::Rtp::kDefaultMaxPacketSize.
+  const size_t kTcpOverIpv4HeaderSize = 40;
+  SetMaxRtpPacketSize(IP_PACKET_SIZE - kTcpOverIpv4HeaderSize);
+}
+
+ModuleRtpRtcpImpl2::~ModuleRtpRtcpImpl2() {
+  RTC_DCHECK_RUN_ON(&construction_thread_checker_);
+}
+
+// Returns the number of milliseconds until the module want a worker thread
+// to call Process.
+int64_t ModuleRtpRtcpImpl2::TimeUntilNextProcess() {
+  RTC_DCHECK_RUN_ON(&process_thread_checker_);
+  return std::max<int64_t>(0,
+                           next_process_time_ - clock_->TimeInMilliseconds());
+}
+
+// Process any pending tasks such as timeouts (non time critical events).
+void ModuleRtpRtcpImpl2::Process() {
+  RTC_DCHECK_RUN_ON(&process_thread_checker_);
+  const int64_t now = clock_->TimeInMilliseconds();
+  // TODO(bugs.webrtc.org/11581): Figure out why we need to call Process() 200
+  // times a second.
+  next_process_time_ = now + kRtpRtcpMaxIdleTimeProcessMs;
+
+  if (rtp_sender_) {
+    if (now >= last_bitrate_process_time_ + kRtpRtcpBitrateProcessTimeMs) {
+      rtp_sender_->packet_sender.ProcessBitrateAndNotifyObservers();
+      last_bitrate_process_time_ = now;
+      // TODO(bugs.webrtc.org/11581): Is this a bug? At the top of the function,
+      // next_process_time_ is incremented by 5ms, here we effectively do a
+      // std::min() of (now + 5ms, now + 10ms). Seems like this is a no-op?
+      next_process_time_ =
+          std::min(next_process_time_, now + kRtpRtcpBitrateProcessTimeMs);
+    }
+  }
+
+  // TODO(bugs.webrtc.org/11581): We update the RTT once a second, whereas other
+  // things that run in this method are updated much more frequently. Move the
+  // RTT checking over to the worker thread, which matches better with where the
+  // stats are maintained.
+  bool process_rtt = now >= last_rtt_process_time_ + kRtpRtcpRttProcessTimeMs;
+  if (rtcp_sender_.Sending()) {
+    // Process RTT if we have received a report block and we haven't
+    // processed RTT for at least |kRtpRtcpRttProcessTimeMs| milliseconds.
+    // Note that LastReceivedReportBlockMs() grabs a lock, so check
+    // |process_rtt| first.
+    if (process_rtt &&
+        rtcp_receiver_.LastReceivedReportBlockMs() > last_rtt_process_time_) {
+      std::vector<RTCPReportBlock> receive_blocks;
+      rtcp_receiver_.StatisticsReceived(&receive_blocks);
+      int64_t max_rtt = 0;
+      for (std::vector<RTCPReportBlock>::iterator it = receive_blocks.begin();
+           it != receive_blocks.end(); ++it) {
+        int64_t rtt = 0;
+        rtcp_receiver_.RTT(it->sender_ssrc, &rtt, NULL, NULL, NULL);
+        max_rtt = (rtt > max_rtt) ? rtt : max_rtt;
+      }
+      // Report the rtt.
+      if (rtt_stats_ && max_rtt != 0)
+        rtt_stats_->OnRttUpdate(max_rtt);
+    }
+
+    // Verify receiver reports are delivered and the reported sequence number
+    // is increasing.
+    // TODO(bugs.webrtc.org/11581): The timeout value needs to be checked every
+    // few seconds (see internals of RtcpRrTimeout). Here, we may be polling it
+    // a couple of hundred times a second, which isn't great since it grabs a
+    // lock. Note also that LastReceivedReportBlockMs() (called above) and
+    // RtcpRrTimeout() both grab the same lock and check the same timer, so
+    // it should be possible to consolidate that work somehow.
+    if (rtcp_receiver_.RtcpRrTimeout()) {
+      RTC_LOG_F(LS_WARNING) << "Timeout: No RTCP RR received.";
+    } else if (rtcp_receiver_.RtcpRrSequenceNumberTimeout()) {
+      RTC_LOG_F(LS_WARNING) << "Timeout: No increase in RTCP RR extended "
+                               "highest sequence number.";
+    }
+
+    if (remote_bitrate_ && rtcp_sender_.TMMBR()) {
+      unsigned int target_bitrate = 0;
+      std::vector<unsigned int> ssrcs;
+      if (remote_bitrate_->LatestEstimate(&ssrcs, &target_bitrate)) {
+        if (!ssrcs.empty()) {
+          target_bitrate = target_bitrate / ssrcs.size();
+        }
+        rtcp_sender_.SetTargetBitrate(target_bitrate);
+      }
+    }
+  } else {
+    // Report rtt from receiver.
+    if (process_rtt) {
+      int64_t rtt_ms;
+      if (rtt_stats_ && rtcp_receiver_.GetAndResetXrRrRtt(&rtt_ms)) {
+        rtt_stats_->OnRttUpdate(rtt_ms);
+      }
+    }
+  }
+
+  // Get processed rtt.
+  if (process_rtt) {
+    last_rtt_process_time_ = now;
+    // TODO(bugs.webrtc.org/11581): Is this a bug? At the top of the function,
+    // next_process_time_ is incremented by 5ms, here we effectively do a
+    // std::min() of (now + 5ms, now + 1000ms). Seems like this is a no-op?
+    next_process_time_ = std::min(
+        next_process_time_, last_rtt_process_time_ + kRtpRtcpRttProcessTimeMs);
+    if (rtt_stats_) {
+      // Make sure we have a valid RTT before setting.
+      int64_t last_rtt = rtt_stats_->LastProcessedRtt();
+      if (last_rtt >= 0)
+        set_rtt_ms(last_rtt);
+    }
+  }
+
+  if (rtcp_sender_.TimeToSendRTCPReport())
+    rtcp_sender_.SendRTCP(GetFeedbackState(), kRtcpReport);
+
+  if (TMMBR() && rtcp_receiver_.UpdateTmmbrTimers()) {
+    rtcp_receiver_.NotifyTmmbrUpdated();
+  }
+}
+
+void ModuleRtpRtcpImpl2::SetRtxSendStatus(int mode) {
+  rtp_sender_->packet_generator.SetRtxStatus(mode);
+}
+
+int ModuleRtpRtcpImpl2::RtxSendStatus() const {
+  return rtp_sender_ ? rtp_sender_->packet_generator.RtxStatus() : kRtxOff;
+}
+
+void ModuleRtpRtcpImpl2::SetRtxSendPayloadType(int payload_type,
+                                               int associated_payload_type) {
+  rtp_sender_->packet_generator.SetRtxPayloadType(payload_type,
+                                                  associated_payload_type);
+}
+
+absl::optional<uint32_t> ModuleRtpRtcpImpl2::RtxSsrc() const {
+  return rtp_sender_ ? rtp_sender_->packet_generator.RtxSsrc() : absl::nullopt;
+}
+
+absl::optional<uint32_t> ModuleRtpRtcpImpl2::FlexfecSsrc() const {
+  if (rtp_sender_) {
+    return rtp_sender_->packet_generator.FlexfecSsrc();
+  }
+  return absl::nullopt;
+}
+
+void ModuleRtpRtcpImpl2::IncomingRtcpPacket(const uint8_t* rtcp_packet,
+                                            const size_t length) {
+  rtcp_receiver_.IncomingPacket(rtcp_packet, length);
+}
+
+void ModuleRtpRtcpImpl2::RegisterSendPayloadFrequency(int payload_type,
+                                                      int payload_frequency) {
+  rtcp_sender_.SetRtpClockRate(payload_type, payload_frequency);
+}
+
+int32_t ModuleRtpRtcpImpl2::DeRegisterSendPayload(const int8_t payload_type) {
+  return 0;
+}
+
+uint32_t ModuleRtpRtcpImpl2::StartTimestamp() const {
+  return rtp_sender_->packet_generator.TimestampOffset();
+}
+
+// Configure start timestamp, default is a random number.
+void ModuleRtpRtcpImpl2::SetStartTimestamp(const uint32_t timestamp) {
+  rtcp_sender_.SetTimestampOffset(timestamp);
+  rtp_sender_->packet_generator.SetTimestampOffset(timestamp);
+  rtp_sender_->packet_sender.SetTimestampOffset(timestamp);
+}
+
+uint16_t ModuleRtpRtcpImpl2::SequenceNumber() const {
+  return rtp_sender_->packet_generator.SequenceNumber();
+}
+
+// Set SequenceNumber, default is a random number.
+void ModuleRtpRtcpImpl2::SetSequenceNumber(const uint16_t seq_num) {
+  rtp_sender_->packet_generator.SetSequenceNumber(seq_num);
+}
+
+void ModuleRtpRtcpImpl2::SetRtpState(const RtpState& rtp_state) {
+  rtp_sender_->packet_generator.SetRtpState(rtp_state);
+  rtp_sender_->packet_sender.SetMediaHasBeenSent(rtp_state.media_has_been_sent);
+  rtcp_sender_.SetTimestampOffset(rtp_state.start_timestamp);
+}
+
+void ModuleRtpRtcpImpl2::SetRtxState(const RtpState& rtp_state) {
+  rtp_sender_->packet_generator.SetRtxRtpState(rtp_state);
+}
+
+RtpState ModuleRtpRtcpImpl2::GetRtpState() const {
+  RtpState state = rtp_sender_->packet_generator.GetRtpState();
+  state.media_has_been_sent = rtp_sender_->packet_sender.MediaHasBeenSent();
+  return state;
+}
+
+RtpState ModuleRtpRtcpImpl2::GetRtxState() const {
+  return rtp_sender_->packet_generator.GetRtxRtpState();
+}
+
+void ModuleRtpRtcpImpl2::SetRid(const std::string& rid) {
+  if (rtp_sender_) {
+    rtp_sender_->packet_generator.SetRid(rid);
+  }
+}
+
+void ModuleRtpRtcpImpl2::SetMid(const std::string& mid) {
+  if (rtp_sender_) {
+    rtp_sender_->packet_generator.SetMid(mid);
+  }
+  // TODO(bugs.webrtc.org/4050): If we end up supporting the MID SDES item for
+  // RTCP, this will need to be passed down to the RTCPSender also.
+}
+
+void ModuleRtpRtcpImpl2::SetCsrcs(const std::vector<uint32_t>& csrcs) {
+  rtcp_sender_.SetCsrcs(csrcs);
+  rtp_sender_->packet_generator.SetCsrcs(csrcs);
+}
+
+// TODO(pbos): Handle media and RTX streams separately (separate RTCP
+// feedbacks).
+RTCPSender::FeedbackState ModuleRtpRtcpImpl2::GetFeedbackState() {
+  RTCPSender::FeedbackState state;
+  // This is called also when receiver_only is true. Hence below
+  // checks that rtp_sender_ exists.
+  if (rtp_sender_) {
+    StreamDataCounters rtp_stats;
+    StreamDataCounters rtx_stats;
+    rtp_sender_->packet_sender.GetDataCounters(&rtp_stats, &rtx_stats);
+    state.packets_sent =
+        rtp_stats.transmitted.packets + rtx_stats.transmitted.packets;
+    state.media_bytes_sent = rtp_stats.transmitted.payload_bytes +
+                             rtx_stats.transmitted.payload_bytes;
+    state.send_bitrate =
+        rtp_sender_->packet_sender.GetSendRates().Sum().bps<uint32_t>();
+  }
+  state.receiver = &rtcp_receiver_;
+
+  LastReceivedNTP(&state.last_rr_ntp_secs, &state.last_rr_ntp_frac,
+                  &state.remote_sr);
+
+  state.last_xr_rtis = rtcp_receiver_.ConsumeReceivedXrReferenceTimeInfo();
+
+  return state;
+}
+
+// TODO(nisse): This method shouldn't be called for a receive-only
+// stream. Delete rtp_sender_ check as soon as all applications are
+// updated.
+int32_t ModuleRtpRtcpImpl2::SetSendingStatus(const bool sending) {
+  if (rtcp_sender_.Sending() != sending) {
+    // Sends RTCP BYE when going from true to false
+    if (rtcp_sender_.SetSendingStatus(GetFeedbackState(), sending) != 0) {
+      RTC_LOG(LS_WARNING) << "Failed to send RTCP BYE";
+    }
+  }
+  return 0;
+}
+
+bool ModuleRtpRtcpImpl2::Sending() const {
+  return rtcp_sender_.Sending();
+}
+
+// TODO(nisse): This method shouldn't be called for a receive-only
+// stream. Delete rtp_sender_ check as soon as all applications are
+// updated.
+void ModuleRtpRtcpImpl2::SetSendingMediaStatus(const bool sending) {
+  if (rtp_sender_) {
+    rtp_sender_->packet_generator.SetSendingMediaStatus(sending);
+  } else {
+    RTC_DCHECK(!sending);
+  }
+}
+
+bool ModuleRtpRtcpImpl2::SendingMedia() const {
+  return rtp_sender_ ? rtp_sender_->packet_generator.SendingMedia() : false;
+}
+
+bool ModuleRtpRtcpImpl2::IsAudioConfigured() const {
+  return rtp_sender_ ? rtp_sender_->packet_generator.IsAudioConfigured()
+                     : false;
+}
+
+void ModuleRtpRtcpImpl2::SetAsPartOfAllocation(bool part_of_allocation) {
+  RTC_CHECK(rtp_sender_);
+  rtp_sender_->packet_sender.ForceIncludeSendPacketsInAllocation(
+      part_of_allocation);
+}
+
+bool ModuleRtpRtcpImpl2::OnSendingRtpFrame(uint32_t timestamp,
+                                           int64_t capture_time_ms,
+                                           int payload_type,
+                                           bool force_sender_report) {
+  if (!Sending())
+    return false;
+
+  rtcp_sender_.SetLastRtpTime(timestamp, capture_time_ms, payload_type);
+  // Make sure an RTCP report isn't queued behind a key frame.
+  if (rtcp_sender_.TimeToSendRTCPReport(force_sender_report))
+    rtcp_sender_.SendRTCP(GetFeedbackState(), kRtcpReport);
+
+  return true;
+}
+
+bool ModuleRtpRtcpImpl2::TrySendPacket(RtpPacketToSend* packet,
+                                       const PacedPacketInfo& pacing_info) {
+  RTC_DCHECK(rtp_sender_);
+  // TODO(sprang): Consider if we can remove this check.
+  if (!rtp_sender_->packet_generator.SendingMedia()) {
+    return false;
+  }
+  rtp_sender_->packet_sender.SendPacket(packet, pacing_info);
+  return true;
+}
+
+void ModuleRtpRtcpImpl2::OnPacketsAcknowledged(
+    rtc::ArrayView<const uint16_t> sequence_numbers) {
+  RTC_DCHECK(rtp_sender_);
+  rtp_sender_->packet_history.CullAcknowledgedPackets(sequence_numbers);
+}
+
+bool ModuleRtpRtcpImpl2::SupportsPadding() const {
+  RTC_DCHECK(rtp_sender_);
+  return rtp_sender_->packet_generator.SupportsPadding();
+}
+
+bool ModuleRtpRtcpImpl2::SupportsRtxPayloadPadding() const {
+  RTC_DCHECK(rtp_sender_);
+  return rtp_sender_->packet_generator.SupportsRtxPayloadPadding();
+}
+
+std::vector<std::unique_ptr<RtpPacketToSend>>
+ModuleRtpRtcpImpl2::GeneratePadding(size_t target_size_bytes) {
+  RTC_DCHECK(rtp_sender_);
+  return rtp_sender_->packet_generator.GeneratePadding(
+      target_size_bytes, rtp_sender_->packet_sender.MediaHasBeenSent());
+}
+
+std::vector<RtpSequenceNumberMap::Info>
+ModuleRtpRtcpImpl2::GetSentRtpPacketInfos(
+    rtc::ArrayView<const uint16_t> sequence_numbers) const {
+  RTC_DCHECK(rtp_sender_);
+  return rtp_sender_->packet_sender.GetSentRtpPacketInfos(sequence_numbers);
+}
+
+size_t ModuleRtpRtcpImpl2::ExpectedPerPacketOverhead() const {
+  if (!rtp_sender_) {
+    return 0;
+  }
+  return rtp_sender_->packet_generator.ExpectedPerPacketOverhead();
+}
+
+size_t ModuleRtpRtcpImpl2::MaxRtpPacketSize() const {
+  RTC_DCHECK(rtp_sender_);
+  return rtp_sender_->packet_generator.MaxRtpPacketSize();
+}
+
+void ModuleRtpRtcpImpl2::SetMaxRtpPacketSize(size_t rtp_packet_size) {
+  RTC_DCHECK_LE(rtp_packet_size, IP_PACKET_SIZE)
+      << "rtp packet size too large: " << rtp_packet_size;
+  RTC_DCHECK_GT(rtp_packet_size, packet_overhead_)
+      << "rtp packet size too small: " << rtp_packet_size;
+
+  rtcp_sender_.SetMaxRtpPacketSize(rtp_packet_size);
+  if (rtp_sender_) {
+    rtp_sender_->packet_generator.SetMaxRtpPacketSize(rtp_packet_size);
+  }
+}
+
+RtcpMode ModuleRtpRtcpImpl2::RTCP() const {
+  return rtcp_sender_.Status();
+}
+
+// Configure RTCP status i.e on/off.
+void ModuleRtpRtcpImpl2::SetRTCPStatus(const RtcpMode method) {
+  rtcp_sender_.SetRTCPStatus(method);
+}
+
+int32_t ModuleRtpRtcpImpl2::SetCNAME(const char* c_name) {
+  return rtcp_sender_.SetCNAME(c_name);
+}
+
+int32_t ModuleRtpRtcpImpl2::AddMixedCNAME(uint32_t ssrc, const char* c_name) {
+  return rtcp_sender_.AddMixedCNAME(ssrc, c_name);
+}
+
+int32_t ModuleRtpRtcpImpl2::RemoveMixedCNAME(const uint32_t ssrc) {
+  return rtcp_sender_.RemoveMixedCNAME(ssrc);
+}
+
+int32_t ModuleRtpRtcpImpl2::RemoteCNAME(const uint32_t remote_ssrc,
+                                        char c_name[RTCP_CNAME_SIZE]) const {
+  return rtcp_receiver_.CNAME(remote_ssrc, c_name);
+}
+
+int32_t ModuleRtpRtcpImpl2::RemoteNTP(uint32_t* received_ntpsecs,
+                                      uint32_t* received_ntpfrac,
+                                      uint32_t* rtcp_arrival_time_secs,
+                                      uint32_t* rtcp_arrival_time_frac,
+                                      uint32_t* rtcp_timestamp) const {
+  return rtcp_receiver_.NTP(received_ntpsecs, received_ntpfrac,
+                            rtcp_arrival_time_secs, rtcp_arrival_time_frac,
+                            rtcp_timestamp)
+             ? 0
+             : -1;
+}
+
+// Get RoundTripTime.
+int32_t ModuleRtpRtcpImpl2::RTT(const uint32_t remote_ssrc,
+                                int64_t* rtt,
+                                int64_t* avg_rtt,
+                                int64_t* min_rtt,
+                                int64_t* max_rtt) const {
+  int32_t ret = rtcp_receiver_.RTT(remote_ssrc, rtt, avg_rtt, min_rtt, max_rtt);
+  if (rtt && *rtt == 0) {
+    // Try to get RTT from RtcpRttStats class.
+    *rtt = rtt_ms();
+  }
+  return ret;
+}
+
+int64_t ModuleRtpRtcpImpl2::ExpectedRetransmissionTimeMs() const {
+  int64_t expected_retransmission_time_ms = rtt_ms();
+  if (expected_retransmission_time_ms > 0) {
+    return expected_retransmission_time_ms;
+  }
+  // No rtt available (|kRtpRtcpRttProcessTimeMs| not yet passed?), so try to
+  // poll avg_rtt_ms directly from rtcp receiver.
+  if (rtcp_receiver_.RTT(rtcp_receiver_.RemoteSSRC(), nullptr,
+                         &expected_retransmission_time_ms, nullptr,
+                         nullptr) == 0) {
+    return expected_retransmission_time_ms;
+  }
+  return kDefaultExpectedRetransmissionTimeMs;
+}
+
+// Force a send of an RTCP packet.
+// Normal SR and RR are triggered via the process function.
+int32_t ModuleRtpRtcpImpl2::SendRTCP(RTCPPacketType packet_type) {
+  return rtcp_sender_.SendRTCP(GetFeedbackState(), packet_type);
+}
+
+int32_t ModuleRtpRtcpImpl2::SetRTCPApplicationSpecificData(
+    const uint8_t sub_type,
+    const uint32_t name,
+    const uint8_t* data,
+    const uint16_t length) {
+  return rtcp_sender_.SetApplicationSpecificData(sub_type, name, data, length);
+}
+
+void ModuleRtpRtcpImpl2::SetRtcpXrRrtrStatus(bool enable) {
+  rtcp_receiver_.SetRtcpXrRrtrStatus(enable);
+  rtcp_sender_.SendRtcpXrReceiverReferenceTime(enable);
+}
+
+bool ModuleRtpRtcpImpl2::RtcpXrRrtrStatus() const {
+  return rtcp_sender_.RtcpXrReceiverReferenceTime();
+}
+
+// TODO(asapersson): Replace this method with the one below.
+int32_t ModuleRtpRtcpImpl2::DataCountersRTP(size_t* bytes_sent,
+                                            uint32_t* packets_sent) const {
+  StreamDataCounters rtp_stats;
+  StreamDataCounters rtx_stats;
+  rtp_sender_->packet_sender.GetDataCounters(&rtp_stats, &rtx_stats);
+
+  if (bytes_sent) {
+    // TODO(http://crbug.com/webrtc/10525): Bytes sent should only include
+    // payload bytes, not header and padding bytes.
+    *bytes_sent = rtp_stats.transmitted.payload_bytes +
+                  rtp_stats.transmitted.padding_bytes +
+                  rtp_stats.transmitted.header_bytes +
+                  rtx_stats.transmitted.payload_bytes +
+                  rtx_stats.transmitted.padding_bytes +
+                  rtx_stats.transmitted.header_bytes;
+  }
+  if (packets_sent) {
+    *packets_sent =
+        rtp_stats.transmitted.packets + rtx_stats.transmitted.packets;
+  }
+  return 0;
+}
+
+void ModuleRtpRtcpImpl2::GetSendStreamDataCounters(
+    StreamDataCounters* rtp_counters,
+    StreamDataCounters* rtx_counters) const {
+  rtp_sender_->packet_sender.GetDataCounters(rtp_counters, rtx_counters);
+}
+
+// Received RTCP report.
+int32_t ModuleRtpRtcpImpl2::RemoteRTCPStat(
+    std::vector<RTCPReportBlock>* receive_blocks) const {
+  return rtcp_receiver_.StatisticsReceived(receive_blocks);
+}
+
+std::vector<ReportBlockData> ModuleRtpRtcpImpl2::GetLatestReportBlockData()
+    const {
+  return rtcp_receiver_.GetLatestReportBlockData();
+}
+
+// (REMB) Receiver Estimated Max Bitrate.
+void ModuleRtpRtcpImpl2::SetRemb(int64_t bitrate_bps,
+                                 std::vector<uint32_t> ssrcs) {
+  rtcp_sender_.SetRemb(bitrate_bps, std::move(ssrcs));
+}
+
+void ModuleRtpRtcpImpl2::UnsetRemb() {
+  rtcp_sender_.UnsetRemb();
+}
+
+void ModuleRtpRtcpImpl2::SetExtmapAllowMixed(bool extmap_allow_mixed) {
+  rtp_sender_->packet_generator.SetExtmapAllowMixed(extmap_allow_mixed);
+}
+
+int32_t ModuleRtpRtcpImpl2::RegisterSendRtpHeaderExtension(
+    const RTPExtensionType type,
+    const uint8_t id) {
+  return rtp_sender_->packet_generator.RegisterRtpHeaderExtension(type, id);
+}
+
+void ModuleRtpRtcpImpl2::RegisterRtpHeaderExtension(absl::string_view uri,
+                                                    int id) {
+  bool registered =
+      rtp_sender_->packet_generator.RegisterRtpHeaderExtension(uri, id);
+  RTC_CHECK(registered);
+}
+
+int32_t ModuleRtpRtcpImpl2::DeregisterSendRtpHeaderExtension(
+    const RTPExtensionType type) {
+  return rtp_sender_->packet_generator.DeregisterRtpHeaderExtension(type);
+}
+void ModuleRtpRtcpImpl2::DeregisterSendRtpHeaderExtension(
+    absl::string_view uri) {
+  rtp_sender_->packet_generator.DeregisterRtpHeaderExtension(uri);
+}
+
+// (TMMBR) Temporary Max Media Bit Rate.
+bool ModuleRtpRtcpImpl2::TMMBR() const {
+  return rtcp_sender_.TMMBR();
+}
+
+void ModuleRtpRtcpImpl2::SetTMMBRStatus(const bool enable) {
+  rtcp_sender_.SetTMMBRStatus(enable);
+}
+
+void ModuleRtpRtcpImpl2::SetTmmbn(std::vector<rtcp::TmmbItem> bounding_set) {
+  rtcp_sender_.SetTmmbn(std::move(bounding_set));
+}
+
+// Send a Negative acknowledgment packet.
+int32_t ModuleRtpRtcpImpl2::SendNACK(const uint16_t* nack_list,
+                                     const uint16_t size) {
+  uint16_t nack_length = size;
+  uint16_t start_id = 0;
+  int64_t now_ms = clock_->TimeInMilliseconds();
+  if (TimeToSendFullNackList(now_ms)) {
+    nack_last_time_sent_full_ms_ = now_ms;
+  } else {
+    // Only send extended list.
+    if (nack_last_seq_number_sent_ == nack_list[size - 1]) {
+      // Last sequence number is the same, do not send list.
+      return 0;
+    }
+    // Send new sequence numbers.
+    for (int i = 0; i < size; ++i) {
+      if (nack_last_seq_number_sent_ == nack_list[i]) {
+        start_id = i + 1;
+        break;
+      }
+    }
+    nack_length = size - start_id;
+  }
+
+  // Our RTCP NACK implementation is limited to kRtcpMaxNackFields sequence
+  // numbers per RTCP packet.
+  if (nack_length > kRtcpMaxNackFields) {
+    nack_length = kRtcpMaxNackFields;
+  }
+  nack_last_seq_number_sent_ = nack_list[start_id + nack_length - 1];
+
+  return rtcp_sender_.SendRTCP(GetFeedbackState(), kRtcpNack, nack_length,
+                               &nack_list[start_id]);
+}
+
+void ModuleRtpRtcpImpl2::SendNack(
+    const std::vector<uint16_t>& sequence_numbers) {
+  rtcp_sender_.SendRTCP(GetFeedbackState(), kRtcpNack, sequence_numbers.size(),
+                        sequence_numbers.data());
+}
+
+bool ModuleRtpRtcpImpl2::TimeToSendFullNackList(int64_t now) const {
+  // Use RTT from RtcpRttStats class if provided.
+  int64_t rtt = rtt_ms();
+  if (rtt == 0) {
+    rtcp_receiver_.RTT(rtcp_receiver_.RemoteSSRC(), NULL, &rtt, NULL, NULL);
+  }
+
+  const int64_t kStartUpRttMs = 100;
+  int64_t wait_time = 5 + ((rtt * 3) >> 1);  // 5 + RTT * 1.5.
+  if (rtt == 0) {
+    wait_time = kStartUpRttMs;
+  }
+
+  // Send a full NACK list once within every |wait_time|.
+  return now - nack_last_time_sent_full_ms_ > wait_time;
+}
+
+// Store the sent packets, needed to answer to Negative acknowledgment requests.
+void ModuleRtpRtcpImpl2::SetStorePacketsStatus(const bool enable,
+                                               const uint16_t number_to_store) {
+  rtp_sender_->packet_history.SetStorePacketsStatus(
+      enable ? RtpPacketHistory::StorageMode::kStoreAndCull
+             : RtpPacketHistory::StorageMode::kDisabled,
+      number_to_store);
+}
+
+bool ModuleRtpRtcpImpl2::StorePackets() const {
+  return rtp_sender_->packet_history.GetStorageMode() !=
+         RtpPacketHistory::StorageMode::kDisabled;
+}
+
+void ModuleRtpRtcpImpl2::SendCombinedRtcpPacket(
+    std::vector<std::unique_ptr<rtcp::RtcpPacket>> rtcp_packets) {
+  rtcp_sender_.SendCombinedRtcpPacket(std::move(rtcp_packets));
+}
+
+int32_t ModuleRtpRtcpImpl2::SendLossNotification(uint16_t last_decoded_seq_num,
+                                                 uint16_t last_received_seq_num,
+                                                 bool decodability_flag,
+                                                 bool buffering_allowed) {
+  return rtcp_sender_.SendLossNotification(
+      GetFeedbackState(), last_decoded_seq_num, last_received_seq_num,
+      decodability_flag, buffering_allowed);
+}
+
+void ModuleRtpRtcpImpl2::SetRemoteSSRC(const uint32_t ssrc) {
+  // Inform about the incoming SSRC.
+  rtcp_sender_.SetRemoteSSRC(ssrc);
+  rtcp_receiver_.SetRemoteSSRC(ssrc);
+}
+
+// TODO(nisse): Delete video_rate amd fec_rate arguments.
+void ModuleRtpRtcpImpl2::BitrateSent(uint32_t* total_rate,
+                                     uint32_t* video_rate,
+                                     uint32_t* fec_rate,
+                                     uint32_t* nack_rate) const {
+  RtpSendRates send_rates = rtp_sender_->packet_sender.GetSendRates();
+  *total_rate = send_rates.Sum().bps<uint32_t>();
+  if (video_rate)
+    *video_rate = 0;
+  if (fec_rate)
+    *fec_rate = 0;
+  *nack_rate = send_rates[RtpPacketMediaType::kRetransmission].bps<uint32_t>();
+}
+
+RtpSendRates ModuleRtpRtcpImpl2::GetSendRates() const {
+  return rtp_sender_->packet_sender.GetSendRates();
+}
+
+void ModuleRtpRtcpImpl2::OnRequestSendReport() {
+  SendRTCP(kRtcpSr);
+}
+
+void ModuleRtpRtcpImpl2::OnReceivedNack(
+    const std::vector<uint16_t>& nack_sequence_numbers) {
+  if (!rtp_sender_)
+    return;
+
+  if (!StorePackets() || nack_sequence_numbers.empty()) {
+    return;
+  }
+  // Use RTT from RtcpRttStats class if provided.
+  int64_t rtt = rtt_ms();
+  if (rtt == 0) {
+    rtcp_receiver_.RTT(rtcp_receiver_.RemoteSSRC(), NULL, &rtt, NULL, NULL);
+  }
+  rtp_sender_->packet_generator.OnReceivedNack(nack_sequence_numbers, rtt);
+}
+
+void ModuleRtpRtcpImpl2::OnReceivedRtcpReportBlocks(
+    const ReportBlockList& report_blocks) {
+  if (rtp_sender_) {
+    uint32_t ssrc = SSRC();
+    absl::optional<uint32_t> rtx_ssrc;
+    if (rtp_sender_->packet_generator.RtxStatus() != kRtxOff) {
+      rtx_ssrc = rtp_sender_->packet_generator.RtxSsrc();
+    }
+
+    for (const RTCPReportBlock& report_block : report_blocks) {
+      if (ssrc == report_block.source_ssrc) {
+        rtp_sender_->packet_generator.OnReceivedAckOnSsrc(
+            report_block.extended_highest_sequence_number);
+      } else if (rtx_ssrc && *rtx_ssrc == report_block.source_ssrc) {
+        rtp_sender_->packet_generator.OnReceivedAckOnRtxSsrc(
+            report_block.extended_highest_sequence_number);
+      }
+    }
+  }
+}
+
+bool ModuleRtpRtcpImpl2::LastReceivedNTP(
+    uint32_t* rtcp_arrival_time_secs,  // When we got the last report.
+    uint32_t* rtcp_arrival_time_frac,
+    uint32_t* remote_sr) const {
+  // Remote SR: NTP inside the last received (mid 16 bits from sec and frac).
+  uint32_t ntp_secs = 0;
+  uint32_t ntp_frac = 0;
+
+  if (!rtcp_receiver_.NTP(&ntp_secs, &ntp_frac, rtcp_arrival_time_secs,
+                          rtcp_arrival_time_frac, NULL)) {
+    return false;
+  }
+  *remote_sr =
+      ((ntp_secs & 0x0000ffff) << 16) + ((ntp_frac & 0xffff0000) >> 16);
+  return true;
+}
+
+void ModuleRtpRtcpImpl2::set_rtt_ms(int64_t rtt_ms) {
+  {
+    rtc::CritScope cs(&critical_section_rtt_);
+    rtt_ms_ = rtt_ms;
+  }
+  if (rtp_sender_) {
+    rtp_sender_->packet_history.SetRtt(rtt_ms);
+  }
+}
+
+int64_t ModuleRtpRtcpImpl2::rtt_ms() const {
+  rtc::CritScope cs(&critical_section_rtt_);
+  return rtt_ms_;
+}
+
+void ModuleRtpRtcpImpl2::SetVideoBitrateAllocation(
+    const VideoBitrateAllocation& bitrate) {
+  rtcp_sender_.SetVideoBitrateAllocation(bitrate);
+}
+
+RTPSender* ModuleRtpRtcpImpl2::RtpSender() {
+  return rtp_sender_ ? &rtp_sender_->packet_generator : nullptr;
+}
+
+const RTPSender* ModuleRtpRtcpImpl2::RtpSender() const {
+  return rtp_sender_ ? &rtp_sender_->packet_generator : nullptr;
+}
+
+DataRate ModuleRtpRtcpImpl2::SendRate() const {
+  RTC_DCHECK(rtp_sender_);
+  return rtp_sender_->packet_sender.GetSendRates().Sum();
+}
+
+DataRate ModuleRtpRtcpImpl2::NackOverheadRate() const {
+  RTC_DCHECK(rtp_sender_);
+  return rtp_sender_->packet_sender
+      .GetSendRates()[RtpPacketMediaType::kRetransmission];
+}
+
+}  // namespace webrtc
diff --git a/modules/rtp_rtcp/source/rtp_rtcp_impl2.h b/modules/rtp_rtcp/source/rtp_rtcp_impl2.h
new file mode 100644
index 0000000..67409c0
--- /dev/null
+++ b/modules/rtp_rtcp/source/rtp_rtcp_impl2.h
@@ -0,0 +1,355 @@
+/*
+ *  Copyright (c) 2012 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.
+ */
+
+#ifndef MODULES_RTP_RTCP_SOURCE_RTP_RTCP_IMPL2_H_
+#define MODULES_RTP_RTCP_SOURCE_RTP_RTCP_IMPL2_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <memory>
+#include <set>
+#include <string>
+#include <vector>
+
+#include "absl/types/optional.h"
+#include "api/rtp_headers.h"
+#include "api/video/video_bitrate_allocation.h"
+#include "modules/include/module_fec_types.h"
+#include "modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h"
+#include "modules/rtp_rtcp/include/rtp_rtcp.h"
+#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"  // RTCPPacketType
+#include "modules/rtp_rtcp/source/rtcp_packet/tmmb_item.h"
+#include "modules/rtp_rtcp/source/rtcp_receiver.h"
+#include "modules/rtp_rtcp/source/rtcp_sender.h"
+#include "modules/rtp_rtcp/source/rtp_packet_history.h"
+#include "modules/rtp_rtcp/source/rtp_packet_to_send.h"
+#include "modules/rtp_rtcp/source/rtp_sender.h"
+#include "modules/rtp_rtcp/source/rtp_sender_egress.h"
+#include "rtc_base/critical_section.h"
+#include "rtc_base/gtest_prod_util.h"
+#include "rtc_base/synchronization/sequence_checker.h"
+
+namespace webrtc {
+
+class Clock;
+struct PacedPacketInfo;
+struct RTPVideoHeader;
+
+class ModuleRtpRtcpImpl2 final : public RtpRtcp,
+                                 public RTCPReceiver::ModuleRtpRtcp {
+ public:
+  explicit ModuleRtpRtcpImpl2(const RtpRtcp::Configuration& configuration);
+  ~ModuleRtpRtcpImpl2() override;
+
+  // Returns the number of milliseconds until the module want a worker thread to
+  // call Process.
+  int64_t TimeUntilNextProcess() override;
+
+  // Process any pending tasks such as timeouts.
+  void Process() override;
+
+  // Receiver part.
+
+  // Called when we receive an RTCP packet.
+  void IncomingRtcpPacket(const uint8_t* incoming_packet,
+                          size_t incoming_packet_length) override;
+
+  void SetRemoteSSRC(uint32_t ssrc) override;
+
+  // Sender part.
+  void RegisterSendPayloadFrequency(int payload_type,
+                                    int payload_frequency) override;
+
+  int32_t DeRegisterSendPayload(int8_t payload_type) override;
+
+  void SetExtmapAllowMixed(bool extmap_allow_mixed) override;
+
+  // Register RTP header extension.
+  int32_t RegisterSendRtpHeaderExtension(RTPExtensionType type,
+                                         uint8_t id) override;
+  void RegisterRtpHeaderExtension(absl::string_view uri, int id) override;
+  int32_t DeregisterSendRtpHeaderExtension(RTPExtensionType type) override;
+  void DeregisterSendRtpHeaderExtension(absl::string_view uri) override;
+
+  bool SupportsPadding() const override;
+  bool SupportsRtxPayloadPadding() const override;
+
+  // Get start timestamp.
+  uint32_t StartTimestamp() const override;
+
+  // Configure start timestamp, default is a random number.
+  void SetStartTimestamp(uint32_t timestamp) override;
+
+  uint16_t SequenceNumber() const override;
+
+  // Set SequenceNumber, default is a random number.
+  void SetSequenceNumber(uint16_t seq) override;
+
+  void SetRtpState(const RtpState& rtp_state) override;
+  void SetRtxState(const RtpState& rtp_state) override;
+  RtpState GetRtpState() const override;
+  RtpState GetRtxState() const override;
+
+  uint32_t SSRC() const override { return rtcp_sender_.SSRC(); }
+
+  void SetRid(const std::string& rid) override;
+
+  void SetMid(const std::string& mid) override;
+
+  void SetCsrcs(const std::vector<uint32_t>& csrcs) override;
+
+  RTCPSender::FeedbackState GetFeedbackState();
+
+  void SetRtxSendStatus(int mode) override;
+  int RtxSendStatus() const override;
+  absl::optional<uint32_t> RtxSsrc() const override;
+
+  void SetRtxSendPayloadType(int payload_type,
+                             int associated_payload_type) override;
+
+  absl::optional<uint32_t> FlexfecSsrc() const override;
+
+  // Sends kRtcpByeCode when going from true to false.
+  int32_t SetSendingStatus(bool sending) override;
+
+  bool Sending() const override;
+
+  // Drops or relays media packets.
+  void SetSendingMediaStatus(bool sending) override;
+
+  bool SendingMedia() const override;
+
+  bool IsAudioConfigured() const override;
+
+  void SetAsPartOfAllocation(bool part_of_allocation) override;
+
+  bool OnSendingRtpFrame(uint32_t timestamp,
+                         int64_t capture_time_ms,
+                         int payload_type,
+                         bool force_sender_report) override;
+
+  bool TrySendPacket(RtpPacketToSend* packet,
+                     const PacedPacketInfo& pacing_info) override;
+
+  void OnPacketsAcknowledged(
+      rtc::ArrayView<const uint16_t> sequence_numbers) override;
+
+  std::vector<std::unique_ptr<RtpPacketToSend>> GeneratePadding(
+      size_t target_size_bytes) override;
+
+  std::vector<RtpSequenceNumberMap::Info> GetSentRtpPacketInfos(
+      rtc::ArrayView<const uint16_t> sequence_numbers) const override;
+
+  size_t ExpectedPerPacketOverhead() const override;
+
+  // RTCP part.
+
+  // Get RTCP status.
+  RtcpMode RTCP() const override;
+
+  // Configure RTCP status i.e on/off.
+  void SetRTCPStatus(RtcpMode method) override;
+
+  // Set RTCP CName.
+  int32_t SetCNAME(const char* c_name) override;
+
+  // Get remote CName.
+  int32_t RemoteCNAME(uint32_t remote_ssrc,
+                      char c_name[RTCP_CNAME_SIZE]) const override;
+
+  // Get remote NTP.
+  int32_t RemoteNTP(uint32_t* received_ntp_secs,
+                    uint32_t* received_ntp_frac,
+                    uint32_t* rtcp_arrival_time_secs,
+                    uint32_t* rtcp_arrival_time_frac,
+                    uint32_t* rtcp_timestamp) const override;
+
+  int32_t AddMixedCNAME(uint32_t ssrc, const char* c_name) override;
+
+  int32_t RemoveMixedCNAME(uint32_t ssrc) override;
+
+  // Get RoundTripTime.
+  int32_t RTT(uint32_t remote_ssrc,
+              int64_t* rtt,
+              int64_t* avg_rtt,
+              int64_t* min_rtt,
+              int64_t* max_rtt) const override;
+
+  int64_t ExpectedRetransmissionTimeMs() const override;
+
+  // Force a send of an RTCP packet.
+  // Normal SR and RR are triggered via the process function.
+  int32_t SendRTCP(RTCPPacketType rtcpPacketType) override;
+
+  // Statistics of the amount of data sent and received.
+  int32_t DataCountersRTP(size_t* bytes_sent,
+                          uint32_t* packets_sent) const override;
+
+  void GetSendStreamDataCounters(
+      StreamDataCounters* rtp_counters,
+      StreamDataCounters* rtx_counters) const override;
+
+  // Get received RTCP report, report block.
+  int32_t RemoteRTCPStat(
+      std::vector<RTCPReportBlock>* receive_blocks) const override;
+  // A snapshot of the most recent Report Block with additional data of
+  // interest to statistics. Used to implement RTCRemoteInboundRtpStreamStats.
+  // Within this list, the ReportBlockData::RTCPReportBlock::source_ssrc(),
+  // which is the SSRC of the corresponding outbound RTP stream, is unique.
+  std::vector<ReportBlockData> GetLatestReportBlockData() const override;
+
+  // (REMB) Receiver Estimated Max Bitrate.
+  void SetRemb(int64_t bitrate_bps, std::vector<uint32_t> ssrcs) override;
+  void UnsetRemb() override;
+
+  // (TMMBR) Temporary Max Media Bit Rate.
+  bool TMMBR() const override;
+
+  void SetTMMBRStatus(bool enable) override;
+
+  void SetTmmbn(std::vector<rtcp::TmmbItem> bounding_set) override;
+
+  size_t MaxRtpPacketSize() const override;
+
+  void SetMaxRtpPacketSize(size_t max_packet_size) override;
+
+  // (NACK) Negative acknowledgment part.
+
+  // Send a Negative acknowledgment packet.
+  // TODO(philipel): Deprecate SendNACK and use SendNack instead.
+  int32_t SendNACK(const uint16_t* nack_list, uint16_t size) override;
+
+  void SendNack(const std::vector<uint16_t>& sequence_numbers) override;
+
+  // Store the sent packets, needed to answer to a negative acknowledgment
+  // requests.
+  void SetStorePacketsStatus(bool enable, uint16_t number_to_store) override;
+
+  bool StorePackets() const override;
+
+  void SendCombinedRtcpPacket(
+      std::vector<std::unique_ptr<rtcp::RtcpPacket>> rtcp_packets) override;
+
+  // (APP) Application specific data.
+  int32_t SetRTCPApplicationSpecificData(uint8_t sub_type,
+                                         uint32_t name,
+                                         const uint8_t* data,
+                                         uint16_t length) override;
+
+  // (XR) Receiver reference time report.
+  void SetRtcpXrRrtrStatus(bool enable) override;
+
+  bool RtcpXrRrtrStatus() const override;
+
+  // Video part.
+  int32_t SendLossNotification(uint16_t last_decoded_seq_num,
+                               uint16_t last_received_seq_num,
+                               bool decodability_flag,
+                               bool buffering_allowed) override;
+
+  bool LastReceivedNTP(uint32_t* NTPsecs,
+                       uint32_t* NTPfrac,
+                       uint32_t* remote_sr) const;
+
+  void BitrateSent(uint32_t* total_rate,
+                   uint32_t* video_rate,
+                   uint32_t* fec_rate,
+                   uint32_t* nackRate) const override;
+
+  RtpSendRates GetSendRates() const override;
+
+  void OnReceivedNack(
+      const std::vector<uint16_t>& nack_sequence_numbers) override;
+  void OnReceivedRtcpReportBlocks(
+      const ReportBlockList& report_blocks) override;
+  void OnRequestSendReport() override;
+
+  void SetVideoBitrateAllocation(
+      const VideoBitrateAllocation& bitrate) override;
+
+  RTPSender* RtpSender() override;
+  const RTPSender* RtpSender() const override;
+
+ protected:
+  bool UpdateRTCPReceiveInformationTimers();
+
+  RTPSender* rtp_sender() {
+    return rtp_sender_ ? &rtp_sender_->packet_generator : nullptr;
+  }
+  const RTPSender* rtp_sender() const {
+    return rtp_sender_ ? &rtp_sender_->packet_generator : nullptr;
+  }
+
+  RTCPSender* rtcp_sender() { return &rtcp_sender_; }
+  const RTCPSender* rtcp_sender() const { return &rtcp_sender_; }
+
+  RTCPReceiver* rtcp_receiver() { return &rtcp_receiver_; }
+  const RTCPReceiver* rtcp_receiver() const { return &rtcp_receiver_; }
+
+  Clock* clock() const { return clock_; }
+
+  // TODO(sprang): Remove when usage is gone.
+  DataRate SendRate() const;
+  DataRate NackOverheadRate() const;
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(RtpRtcpImpl2Test, Rtt);
+  FRIEND_TEST_ALL_PREFIXES(RtpRtcpImpl2Test, RttForReceiverOnly);
+
+  struct RtpSenderContext {
+    explicit RtpSenderContext(const RtpRtcp::Configuration& config);
+    // Storage of packets, for retransmissions and padding, if applicable.
+    RtpPacketHistory packet_history;
+    // Handles final time timestamping/stats/etc and handover to Transport.
+    RtpSenderEgress packet_sender;
+    // If no paced sender configured, this class will be used to pass packets
+    // from |packet_generator_| to |packet_sender_|.
+    RtpSenderEgress::NonPacedPacketSender non_paced_sender;
+    // Handles creation of RTP packets to be sent.
+    RTPSender packet_generator;
+  };
+
+  void set_rtt_ms(int64_t rtt_ms);
+  int64_t rtt_ms() const;
+
+  bool TimeToSendFullNackList(int64_t now) const;
+
+  SequenceChecker construction_thread_checker_;
+  SequenceChecker process_thread_checker_;
+
+  std::unique_ptr<RtpSenderContext> rtp_sender_;
+
+  RTCPSender rtcp_sender_;
+  RTCPReceiver rtcp_receiver_;
+
+  Clock* const clock_;
+
+  int64_t last_bitrate_process_time_;
+  int64_t last_rtt_process_time_;
+  int64_t next_process_time_;
+  uint16_t packet_overhead_;
+
+  // Send side
+  int64_t nack_last_time_sent_full_ms_;
+  uint16_t nack_last_seq_number_sent_;
+
+  RemoteBitrateEstimator* const remote_bitrate_;
+
+  RtcpRttStats* const rtt_stats_;
+
+  // The processed RTT from RtcpRttStats.
+  rtc::CriticalSection critical_section_rtt_;
+  int64_t rtt_ms_;
+};
+
+}  // namespace webrtc
+
+#endif  // MODULES_RTP_RTCP_SOURCE_RTP_RTCP_IMPL2_H_
diff --git a/modules/rtp_rtcp/source/rtp_rtcp_impl2_unittest.cc b/modules/rtp_rtcp/source/rtp_rtcp_impl2_unittest.cc
new file mode 100644
index 0000000..7627283
--- /dev/null
+++ b/modules/rtp_rtcp/source/rtp_rtcp_impl2_unittest.cc
@@ -0,0 +1,630 @@
+/*
+ *  Copyright (c) 2013 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.
+ */
+
+#include "modules/rtp_rtcp/source/rtp_rtcp_impl2.h"
+
+#include <map>
+#include <memory>
+#include <set>
+
+#include "api/transport/field_trial_based_config.h"
+#include "api/video_codecs/video_codec.h"
+#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
+#include "modules/rtp_rtcp/source/rtcp_packet.h"
+#include "modules/rtp_rtcp/source/rtcp_packet/nack.h"
+#include "modules/rtp_rtcp/source/rtp_packet_received.h"
+#include "modules/rtp_rtcp/source/rtp_sender_video.h"
+#include "rtc_base/rate_limiter.h"
+#include "test/gmock.h"
+#include "test/gtest.h"
+#include "test/rtcp_packet_parser.h"
+#include "test/rtp_header_parser.h"
+
+using ::testing::ElementsAre;
+
+namespace webrtc {
+namespace {
+const uint32_t kSenderSsrc = 0x12345;
+const uint32_t kReceiverSsrc = 0x23456;
+const int64_t kOneWayNetworkDelayMs = 100;
+const uint8_t kBaseLayerTid = 0;
+const uint8_t kHigherLayerTid = 1;
+const uint16_t kSequenceNumber = 100;
+
+class RtcpRttStatsTestImpl : public RtcpRttStats {
+ public:
+  RtcpRttStatsTestImpl() : rtt_ms_(0) {}
+  ~RtcpRttStatsTestImpl() override = default;
+
+  void OnRttUpdate(int64_t rtt_ms) override { rtt_ms_ = rtt_ms; }
+  int64_t LastProcessedRtt() const override { return rtt_ms_; }
+  int64_t rtt_ms_;
+};
+
+class SendTransport : public Transport {
+ public:
+  SendTransport()
+      : receiver_(nullptr),
+        clock_(nullptr),
+        delay_ms_(0),
+        rtp_packets_sent_(0),
+        rtcp_packets_sent_(0) {}
+
+  void SetRtpRtcpModule(ModuleRtpRtcpImpl2* receiver) { receiver_ = receiver; }
+  void SimulateNetworkDelay(int64_t delay_ms, SimulatedClock* clock) {
+    clock_ = clock;
+    delay_ms_ = delay_ms;
+  }
+  bool SendRtp(const uint8_t* data,
+               size_t len,
+               const PacketOptions& options) override {
+    RTPHeader header;
+    std::unique_ptr<RtpHeaderParser> parser(RtpHeaderParser::CreateForTest());
+    EXPECT_TRUE(parser->Parse(static_cast<const uint8_t*>(data), len, &header));
+    ++rtp_packets_sent_;
+    last_rtp_header_ = header;
+    return true;
+  }
+  bool SendRtcp(const uint8_t* data, size_t len) override {
+    test::RtcpPacketParser parser;
+    parser.Parse(data, len);
+    last_nack_list_ = parser.nack()->packet_ids();
+
+    if (clock_) {
+      clock_->AdvanceTimeMilliseconds(delay_ms_);
+    }
+    EXPECT_TRUE(receiver_);
+    receiver_->IncomingRtcpPacket(data, len);
+    ++rtcp_packets_sent_;
+    return true;
+  }
+  size_t NumRtcpSent() { return rtcp_packets_sent_; }
+  ModuleRtpRtcpImpl2* receiver_;
+  SimulatedClock* clock_;
+  int64_t delay_ms_;
+  int rtp_packets_sent_;
+  size_t rtcp_packets_sent_;
+  RTPHeader last_rtp_header_;
+  std::vector<uint16_t> last_nack_list_;
+};
+
+class RtpRtcpModule : public RtcpPacketTypeCounterObserver {
+ public:
+  RtpRtcpModule(SimulatedClock* clock, bool is_sender)
+      : is_sender_(is_sender),
+        receive_statistics_(ReceiveStatistics::Create(clock)),
+        clock_(clock) {
+    CreateModuleImpl();
+    transport_.SimulateNetworkDelay(kOneWayNetworkDelayMs, clock);
+  }
+
+  const bool is_sender_;
+  RtcpPacketTypeCounter packets_sent_;
+  RtcpPacketTypeCounter packets_received_;
+  std::unique_ptr<ReceiveStatistics> receive_statistics_;
+  SendTransport transport_;
+  RtcpRttStatsTestImpl rtt_stats_;
+  std::unique_ptr<ModuleRtpRtcpImpl2> impl_;
+  int rtcp_report_interval_ms_ = 0;
+
+  void RtcpPacketTypesCounterUpdated(
+      uint32_t ssrc,
+      const RtcpPacketTypeCounter& packet_counter) override {
+    counter_map_[ssrc] = packet_counter;
+  }
+
+  RtcpPacketTypeCounter RtcpSent() {
+    // RTCP counters for remote SSRC.
+    return counter_map_[is_sender_ ? kReceiverSsrc : kSenderSsrc];
+  }
+
+  RtcpPacketTypeCounter RtcpReceived() {
+    // Received RTCP stats for (own) local SSRC.
+    return counter_map_[impl_->SSRC()];
+  }
+  int RtpSent() { return transport_.rtp_packets_sent_; }
+  uint16_t LastRtpSequenceNumber() {
+    return transport_.last_rtp_header_.sequenceNumber;
+  }
+  std::vector<uint16_t> LastNackListSent() {
+    return transport_.last_nack_list_;
+  }
+  void SetRtcpReportIntervalAndReset(int rtcp_report_interval_ms) {
+    rtcp_report_interval_ms_ = rtcp_report_interval_ms;
+    CreateModuleImpl();
+  }
+
+ private:
+  void CreateModuleImpl() {
+    RtpRtcp::Configuration config;
+    config.audio = false;
+    config.clock = clock_;
+    config.outgoing_transport = &transport_;
+    config.receive_statistics = receive_statistics_.get();
+    config.rtcp_packet_type_counter_observer = this;
+    config.rtt_stats = &rtt_stats_;
+    config.rtcp_report_interval_ms = rtcp_report_interval_ms_;
+    config.local_media_ssrc = is_sender_ ? kSenderSsrc : kReceiverSsrc;
+    config.need_rtp_packet_infos = true;
+
+    impl_.reset(new ModuleRtpRtcpImpl2(config));
+    impl_->SetRemoteSSRC(is_sender_ ? kReceiverSsrc : kSenderSsrc);
+    impl_->SetRTCPStatus(RtcpMode::kCompound);
+  }
+
+  SimulatedClock* const clock_;
+  std::map<uint32_t, RtcpPacketTypeCounter> counter_map_;
+};
+}  // namespace
+
+class RtpRtcpImpl2Test : public ::testing::Test {
+ protected:
+  RtpRtcpImpl2Test()
+      : clock_(133590000000000),
+        sender_(&clock_, /*is_sender=*/true),
+        receiver_(&clock_, /*is_sender=*/false) {}
+
+  void SetUp() override {
+    // Send module.
+    EXPECT_EQ(0, sender_.impl_->SetSendingStatus(true));
+    sender_.impl_->SetSendingMediaStatus(true);
+    sender_.impl_->SetSequenceNumber(kSequenceNumber);
+    sender_.impl_->SetStorePacketsStatus(true, 100);
+
+    FieldTrialBasedConfig field_trials;
+    RTPSenderVideo::Config video_config;
+    video_config.clock = &clock_;
+    video_config.rtp_sender = sender_.impl_->RtpSender();
+    video_config.field_trials = &field_trials;
+    sender_video_ = std::make_unique<RTPSenderVideo>(video_config);
+
+    memset(&codec_, 0, sizeof(VideoCodec));
+    codec_.plType = 100;
+    codec_.width = 320;
+    codec_.height = 180;
+
+    // Receive module.
+    EXPECT_EQ(0, receiver_.impl_->SetSendingStatus(false));
+    receiver_.impl_->SetSendingMediaStatus(false);
+    // Transport settings.
+    sender_.transport_.SetRtpRtcpModule(receiver_.impl_.get());
+    receiver_.transport_.SetRtpRtcpModule(sender_.impl_.get());
+  }
+
+  SimulatedClock clock_;
+  RtpRtcpModule sender_;
+  std::unique_ptr<RTPSenderVideo> sender_video_;
+  RtpRtcpModule receiver_;
+  VideoCodec codec_;
+
+  void SendFrame(const RtpRtcpModule* module,
+                 RTPSenderVideo* sender,
+                 uint8_t tid) {
+    RTPVideoHeaderVP8 vp8_header = {};
+    vp8_header.temporalIdx = tid;
+    RTPVideoHeader rtp_video_header;
+    rtp_video_header.frame_type = VideoFrameType::kVideoFrameKey;
+    rtp_video_header.width = codec_.width;
+    rtp_video_header.height = codec_.height;
+    rtp_video_header.rotation = kVideoRotation_0;
+    rtp_video_header.content_type = VideoContentType::UNSPECIFIED;
+    rtp_video_header.playout_delay = {-1, -1};
+    rtp_video_header.is_first_packet_in_frame = true;
+    rtp_video_header.simulcastIdx = 0;
+    rtp_video_header.codec = kVideoCodecVP8;
+    rtp_video_header.video_type_header = vp8_header;
+    rtp_video_header.video_timing = {0u, 0u, 0u, 0u, 0u, 0u, false};
+
+    const uint8_t payload[100] = {0};
+    EXPECT_TRUE(module->impl_->OnSendingRtpFrame(0, 0, codec_.plType, true));
+    EXPECT_TRUE(sender->SendVideo(codec_.plType, VideoCodecType::kVideoCodecVP8,
+                                  0, 0, payload, nullptr, rtp_video_header, 0));
+  }
+
+  void IncomingRtcpNack(const RtpRtcpModule* module, uint16_t sequence_number) {
+    bool sender = module->impl_->SSRC() == kSenderSsrc;
+    rtcp::Nack nack;
+    uint16_t list[1];
+    list[0] = sequence_number;
+    const uint16_t kListLength = sizeof(list) / sizeof(list[0]);
+    nack.SetSenderSsrc(sender ? kReceiverSsrc : kSenderSsrc);
+    nack.SetMediaSsrc(sender ? kSenderSsrc : kReceiverSsrc);
+    nack.SetPacketIds(list, kListLength);
+    rtc::Buffer packet = nack.Build();
+    module->impl_->IncomingRtcpPacket(packet.data(), packet.size());
+  }
+};
+
+TEST_F(RtpRtcpImpl2Test, RetransmitsAllLayers) {
+  // Send frames.
+  EXPECT_EQ(0, sender_.RtpSent());
+  SendFrame(&sender_, sender_video_.get(), kBaseLayerTid);  // kSequenceNumber
+  SendFrame(&sender_, sender_video_.get(),
+            kHigherLayerTid);  // kSequenceNumber + 1
+  SendFrame(&sender_, sender_video_.get(),
+            kNoTemporalIdx);  // kSequenceNumber + 2
+  EXPECT_EQ(3, sender_.RtpSent());
+  EXPECT_EQ(kSequenceNumber + 2, sender_.LastRtpSequenceNumber());
+
+  // Min required delay until retransmit = 5 + RTT ms (RTT = 0).
+  clock_.AdvanceTimeMilliseconds(5);
+
+  // Frame with kBaseLayerTid re-sent.
+  IncomingRtcpNack(&sender_, kSequenceNumber);
+  EXPECT_EQ(4, sender_.RtpSent());
+  EXPECT_EQ(kSequenceNumber, sender_.LastRtpSequenceNumber());
+  // Frame with kHigherLayerTid re-sent.
+  IncomingRtcpNack(&sender_, kSequenceNumber + 1);
+  EXPECT_EQ(5, sender_.RtpSent());
+  EXPECT_EQ(kSequenceNumber + 1, sender_.LastRtpSequenceNumber());
+  // Frame with kNoTemporalIdx re-sent.
+  IncomingRtcpNack(&sender_, kSequenceNumber + 2);
+  EXPECT_EQ(6, sender_.RtpSent());
+  EXPECT_EQ(kSequenceNumber + 2, sender_.LastRtpSequenceNumber());
+}
+
+TEST_F(RtpRtcpImpl2Test, Rtt) {
+  RtpPacketReceived packet;
+  packet.SetTimestamp(1);
+  packet.SetSequenceNumber(123);
+  packet.SetSsrc(kSenderSsrc);
+  packet.AllocatePayload(100 - 12);
+  receiver_.receive_statistics_->OnRtpPacket(packet);
+
+  // Send Frame before sending an SR.
+  SendFrame(&sender_, sender_video_.get(), kBaseLayerTid);
+  // Sender module should send an SR.
+  EXPECT_EQ(0, sender_.impl_->SendRTCP(kRtcpReport));
+
+  // Receiver module should send a RR with a response to the last received SR.
+  clock_.AdvanceTimeMilliseconds(1000);
+  EXPECT_EQ(0, receiver_.impl_->SendRTCP(kRtcpReport));
+
+  // Verify RTT.
+  int64_t rtt;
+  int64_t avg_rtt;
+  int64_t min_rtt;
+  int64_t max_rtt;
+  EXPECT_EQ(
+      0, sender_.impl_->RTT(kReceiverSsrc, &rtt, &avg_rtt, &min_rtt, &max_rtt));
+  EXPECT_NEAR(2 * kOneWayNetworkDelayMs, rtt, 1);
+  EXPECT_NEAR(2 * kOneWayNetworkDelayMs, avg_rtt, 1);
+  EXPECT_NEAR(2 * kOneWayNetworkDelayMs, min_rtt, 1);
+  EXPECT_NEAR(2 * kOneWayNetworkDelayMs, max_rtt, 1);
+
+  // No RTT from other ssrc.
+  EXPECT_EQ(-1, sender_.impl_->RTT(kReceiverSsrc + 1, &rtt, &avg_rtt, &min_rtt,
+                                   &max_rtt));
+
+  // Verify RTT from rtt_stats config.
+  EXPECT_EQ(0, sender_.rtt_stats_.LastProcessedRtt());
+  EXPECT_EQ(0, sender_.impl_->rtt_ms());
+  sender_.impl_->Process();
+  EXPECT_NEAR(2 * kOneWayNetworkDelayMs, sender_.rtt_stats_.LastProcessedRtt(),
+              1);
+  EXPECT_NEAR(2 * kOneWayNetworkDelayMs, sender_.impl_->rtt_ms(), 1);
+}
+
+TEST_F(RtpRtcpImpl2Test, SetRtcpXrRrtrStatus) {
+  EXPECT_FALSE(receiver_.impl_->RtcpXrRrtrStatus());
+  receiver_.impl_->SetRtcpXrRrtrStatus(true);
+  EXPECT_TRUE(receiver_.impl_->RtcpXrRrtrStatus());
+}
+
+TEST_F(RtpRtcpImpl2Test, RttForReceiverOnly) {
+  receiver_.impl_->SetRtcpXrRrtrStatus(true);
+
+  // Receiver module should send a Receiver time reference report (RTRR).
+  EXPECT_EQ(0, receiver_.impl_->SendRTCP(kRtcpReport));
+
+  // Sender module should send a response to the last received RTRR (DLRR).
+  clock_.AdvanceTimeMilliseconds(1000);
+  // Send Frame before sending a SR.
+  SendFrame(&sender_, sender_video_.get(), kBaseLayerTid);
+  EXPECT_EQ(0, sender_.impl_->SendRTCP(kRtcpReport));
+
+  // Verify RTT.
+  EXPECT_EQ(0, receiver_.rtt_stats_.LastProcessedRtt());
+  EXPECT_EQ(0, receiver_.impl_->rtt_ms());
+  receiver_.impl_->Process();
+  EXPECT_NEAR(2 * kOneWayNetworkDelayMs,
+              receiver_.rtt_stats_.LastProcessedRtt(), 1);
+  EXPECT_NEAR(2 * kOneWayNetworkDelayMs, receiver_.impl_->rtt_ms(), 1);
+}
+
+TEST_F(RtpRtcpImpl2Test, NoSrBeforeMedia) {
+  // Ignore fake transport delays in this test.
+  sender_.transport_.SimulateNetworkDelay(0, &clock_);
+  receiver_.transport_.SimulateNetworkDelay(0, &clock_);
+
+  sender_.impl_->Process();
+  EXPECT_EQ(-1, sender_.RtcpSent().first_packet_time_ms);
+
+  // Verify no SR is sent before media has been sent, RR should still be sent
+  // from the receiving module though.
+  clock_.AdvanceTimeMilliseconds(2000);
+  int64_t current_time = clock_.TimeInMilliseconds();
+  sender_.impl_->Process();
+  receiver_.impl_->Process();
+  EXPECT_EQ(-1, sender_.RtcpSent().first_packet_time_ms);
+  EXPECT_EQ(receiver_.RtcpSent().first_packet_time_ms, current_time);
+
+  SendFrame(&sender_, sender_video_.get(), kBaseLayerTid);
+  EXPECT_EQ(sender_.RtcpSent().first_packet_time_ms, current_time);
+}
+
+TEST_F(RtpRtcpImpl2Test, RtcpPacketTypeCounter_Nack) {
+  EXPECT_EQ(-1, receiver_.RtcpSent().first_packet_time_ms);
+  EXPECT_EQ(-1, sender_.RtcpReceived().first_packet_time_ms);
+  EXPECT_EQ(0U, sender_.RtcpReceived().nack_packets);
+  EXPECT_EQ(0U, receiver_.RtcpSent().nack_packets);
+
+  // Receive module sends a NACK.
+  const uint16_t kNackLength = 1;
+  uint16_t nack_list[kNackLength] = {123};
+  EXPECT_EQ(0, receiver_.impl_->SendNACK(nack_list, kNackLength));
+  EXPECT_EQ(1U, receiver_.RtcpSent().nack_packets);
+  EXPECT_GT(receiver_.RtcpSent().first_packet_time_ms, -1);
+
+  // Send module receives the NACK.
+  EXPECT_EQ(1U, sender_.RtcpReceived().nack_packets);
+  EXPECT_GT(sender_.RtcpReceived().first_packet_time_ms, -1);
+}
+
+TEST_F(RtpRtcpImpl2Test, AddStreamDataCounters) {
+  StreamDataCounters rtp;
+  const int64_t kStartTimeMs = 1;
+  rtp.first_packet_time_ms = kStartTimeMs;
+  rtp.transmitted.packets = 1;
+  rtp.transmitted.payload_bytes = 1;
+  rtp.transmitted.header_bytes = 2;
+  rtp.transmitted.padding_bytes = 3;
+  EXPECT_EQ(rtp.transmitted.TotalBytes(), rtp.transmitted.payload_bytes +
+                                              rtp.transmitted.header_bytes +
+                                              rtp.transmitted.padding_bytes);
+
+  StreamDataCounters rtp2;
+  rtp2.first_packet_time_ms = -1;
+  rtp2.transmitted.packets = 10;
+  rtp2.transmitted.payload_bytes = 10;
+  rtp2.retransmitted.header_bytes = 4;
+  rtp2.retransmitted.payload_bytes = 5;
+  rtp2.retransmitted.padding_bytes = 6;
+  rtp2.retransmitted.packets = 7;
+  rtp2.fec.packets = 8;
+
+  StreamDataCounters sum = rtp;
+  sum.Add(rtp2);
+  EXPECT_EQ(kStartTimeMs, sum.first_packet_time_ms);
+  EXPECT_EQ(11U, sum.transmitted.packets);
+  EXPECT_EQ(11U, sum.transmitted.payload_bytes);
+  EXPECT_EQ(2U, sum.transmitted.header_bytes);
+  EXPECT_EQ(3U, sum.transmitted.padding_bytes);
+  EXPECT_EQ(4U, sum.retransmitted.header_bytes);
+  EXPECT_EQ(5U, sum.retransmitted.payload_bytes);
+  EXPECT_EQ(6U, sum.retransmitted.padding_bytes);
+  EXPECT_EQ(7U, sum.retransmitted.packets);
+  EXPECT_EQ(8U, sum.fec.packets);
+  EXPECT_EQ(sum.transmitted.TotalBytes(),
+            rtp.transmitted.TotalBytes() + rtp2.transmitted.TotalBytes());
+
+  StreamDataCounters rtp3;
+  rtp3.first_packet_time_ms = kStartTimeMs + 10;
+  sum.Add(rtp3);
+  EXPECT_EQ(kStartTimeMs, sum.first_packet_time_ms);  // Holds oldest time.
+}
+
+TEST_F(RtpRtcpImpl2Test, SendsInitialNackList) {
+  // Send module sends a NACK.
+  const uint16_t kNackLength = 1;
+  uint16_t nack_list[kNackLength] = {123};
+  EXPECT_EQ(0U, sender_.RtcpSent().nack_packets);
+  // Send Frame before sending a compound RTCP that starts with SR.
+  SendFrame(&sender_, sender_video_.get(), kBaseLayerTid);
+  EXPECT_EQ(0, sender_.impl_->SendNACK(nack_list, kNackLength));
+  EXPECT_EQ(1U, sender_.RtcpSent().nack_packets);
+  EXPECT_THAT(sender_.LastNackListSent(), ElementsAre(123));
+}
+
+TEST_F(RtpRtcpImpl2Test, SendsExtendedNackList) {
+  // Send module sends a NACK.
+  const uint16_t kNackLength = 1;
+  uint16_t nack_list[kNackLength] = {123};
+  EXPECT_EQ(0U, sender_.RtcpSent().nack_packets);
+  // Send Frame before sending a compound RTCP that starts with SR.
+  SendFrame(&sender_, sender_video_.get(), kBaseLayerTid);
+  EXPECT_EQ(0, sender_.impl_->SendNACK(nack_list, kNackLength));
+  EXPECT_EQ(1U, sender_.RtcpSent().nack_packets);
+  EXPECT_THAT(sender_.LastNackListSent(), ElementsAre(123));
+
+  // Same list not re-send.
+  EXPECT_EQ(0, sender_.impl_->SendNACK(nack_list, kNackLength));
+  EXPECT_EQ(1U, sender_.RtcpSent().nack_packets);
+  EXPECT_THAT(sender_.LastNackListSent(), ElementsAre(123));
+
+  // Only extended list sent.
+  const uint16_t kNackExtLength = 2;
+  uint16_t nack_list_ext[kNackExtLength] = {123, 124};
+  EXPECT_EQ(0, sender_.impl_->SendNACK(nack_list_ext, kNackExtLength));
+  EXPECT_EQ(2U, sender_.RtcpSent().nack_packets);
+  EXPECT_THAT(sender_.LastNackListSent(), ElementsAre(124));
+}
+
+TEST_F(RtpRtcpImpl2Test, ReSendsNackListAfterRttMs) {
+  sender_.transport_.SimulateNetworkDelay(0, &clock_);
+  // Send module sends a NACK.
+  const uint16_t kNackLength = 2;
+  uint16_t nack_list[kNackLength] = {123, 125};
+  EXPECT_EQ(0U, sender_.RtcpSent().nack_packets);
+  // Send Frame before sending a compound RTCP that starts with SR.
+  SendFrame(&sender_, sender_video_.get(), kBaseLayerTid);
+  EXPECT_EQ(0, sender_.impl_->SendNACK(nack_list, kNackLength));
+  EXPECT_EQ(1U, sender_.RtcpSent().nack_packets);
+  EXPECT_THAT(sender_.LastNackListSent(), ElementsAre(123, 125));
+
+  // Same list not re-send, rtt interval has not passed.
+  const int kStartupRttMs = 100;
+  clock_.AdvanceTimeMilliseconds(kStartupRttMs);
+  EXPECT_EQ(0, sender_.impl_->SendNACK(nack_list, kNackLength));
+  EXPECT_EQ(1U, sender_.RtcpSent().nack_packets);
+
+  // Rtt interval passed, full list sent.
+  clock_.AdvanceTimeMilliseconds(1);
+  EXPECT_EQ(0, sender_.impl_->SendNACK(nack_list, kNackLength));
+  EXPECT_EQ(2U, sender_.RtcpSent().nack_packets);
+  EXPECT_THAT(sender_.LastNackListSent(), ElementsAre(123, 125));
+}
+
+TEST_F(RtpRtcpImpl2Test, UniqueNackRequests) {
+  receiver_.transport_.SimulateNetworkDelay(0, &clock_);
+  EXPECT_EQ(0U, receiver_.RtcpSent().nack_packets);
+  EXPECT_EQ(0U, receiver_.RtcpSent().nack_requests);
+  EXPECT_EQ(0U, receiver_.RtcpSent().unique_nack_requests);
+  EXPECT_EQ(0, receiver_.RtcpSent().UniqueNackRequestsInPercent());
+
+  // Receive module sends NACK request.
+  const uint16_t kNackLength = 4;
+  uint16_t nack_list[kNackLength] = {10, 11, 13, 18};
+  EXPECT_EQ(0, receiver_.impl_->SendNACK(nack_list, kNackLength));
+  EXPECT_EQ(1U, receiver_.RtcpSent().nack_packets);
+  EXPECT_EQ(4U, receiver_.RtcpSent().nack_requests);
+  EXPECT_EQ(4U, receiver_.RtcpSent().unique_nack_requests);
+  EXPECT_THAT(receiver_.LastNackListSent(), ElementsAre(10, 11, 13, 18));
+
+  // Send module receives the request.
+  EXPECT_EQ(1U, sender_.RtcpReceived().nack_packets);
+  EXPECT_EQ(4U, sender_.RtcpReceived().nack_requests);
+  EXPECT_EQ(4U, sender_.RtcpReceived().unique_nack_requests);
+  EXPECT_EQ(100, sender_.RtcpReceived().UniqueNackRequestsInPercent());
+
+  // Receive module sends new request with duplicated packets.
+  const int kStartupRttMs = 100;
+  clock_.AdvanceTimeMilliseconds(kStartupRttMs + 1);
+  const uint16_t kNackLength2 = 4;
+  uint16_t nack_list2[kNackLength2] = {11, 18, 20, 21};
+  EXPECT_EQ(0, receiver_.impl_->SendNACK(nack_list2, kNackLength2));
+  EXPECT_EQ(2U, receiver_.RtcpSent().nack_packets);
+  EXPECT_EQ(8U, receiver_.RtcpSent().nack_requests);
+  EXPECT_EQ(6U, receiver_.RtcpSent().unique_nack_requests);
+  EXPECT_THAT(receiver_.LastNackListSent(), ElementsAre(11, 18, 20, 21));
+
+  // Send module receives the request.
+  EXPECT_EQ(2U, sender_.RtcpReceived().nack_packets);
+  EXPECT_EQ(8U, sender_.RtcpReceived().nack_requests);
+  EXPECT_EQ(6U, sender_.RtcpReceived().unique_nack_requests);
+  EXPECT_EQ(75, sender_.RtcpReceived().UniqueNackRequestsInPercent());
+}
+
+TEST_F(RtpRtcpImpl2Test, ConfigurableRtcpReportInterval) {
+  const int kVideoReportInterval = 3000;
+
+  // Recreate sender impl with new configuration, and redo setup.
+  sender_.SetRtcpReportIntervalAndReset(kVideoReportInterval);
+  SetUp();
+
+  SendFrame(&sender_, sender_video_.get(), kBaseLayerTid);
+
+  // Initial state
+  sender_.impl_->Process();
+  EXPECT_EQ(sender_.RtcpSent().first_packet_time_ms, -1);
+  EXPECT_EQ(0u, sender_.transport_.NumRtcpSent());
+
+  // Move ahead to the last ms before a rtcp is expected, no action.
+  clock_.AdvanceTimeMilliseconds(kVideoReportInterval / 2 - 1);
+  sender_.impl_->Process();
+  EXPECT_EQ(sender_.RtcpSent().first_packet_time_ms, -1);
+  EXPECT_EQ(sender_.transport_.NumRtcpSent(), 0u);
+
+  // Move ahead to the first rtcp. Send RTCP.
+  clock_.AdvanceTimeMilliseconds(1);
+  sender_.impl_->Process();
+  EXPECT_GT(sender_.RtcpSent().first_packet_time_ms, -1);
+  EXPECT_EQ(sender_.transport_.NumRtcpSent(), 1u);
+
+  SendFrame(&sender_, sender_video_.get(), kBaseLayerTid);
+
+  // Move ahead to the last possible second before second rtcp is expected.
+  clock_.AdvanceTimeMilliseconds(kVideoReportInterval * 1 / 2 - 1);
+  sender_.impl_->Process();
+  EXPECT_EQ(sender_.transport_.NumRtcpSent(), 1u);
+
+  // Move ahead into the range of second rtcp, the second rtcp may be sent.
+  clock_.AdvanceTimeMilliseconds(1);
+  sender_.impl_->Process();
+  EXPECT_GE(sender_.transport_.NumRtcpSent(), 1u);
+
+  clock_.AdvanceTimeMilliseconds(kVideoReportInterval / 2);
+  sender_.impl_->Process();
+  EXPECT_GE(sender_.transport_.NumRtcpSent(), 1u);
+
+  // Move out the range of second rtcp, the second rtcp must have been sent.
+  clock_.AdvanceTimeMilliseconds(kVideoReportInterval / 2);
+  sender_.impl_->Process();
+  EXPECT_EQ(sender_.transport_.NumRtcpSent(), 2u);
+}
+
+TEST_F(RtpRtcpImpl2Test, StoresPacketInfoForSentPackets) {
+  const uint32_t kStartTimestamp = 1u;
+  SetUp();
+  sender_.impl_->SetStartTimestamp(kStartTimestamp);
+
+  PacedPacketInfo pacing_info;
+  RtpPacketToSend packet(nullptr);
+  packet.set_packet_type(RtpPacketToSend::Type::kVideo);
+  packet.SetSsrc(kSenderSsrc);
+
+  // Single-packet frame.
+  packet.SetTimestamp(1);
+  packet.SetSequenceNumber(1);
+  packet.set_first_packet_of_frame(true);
+  packet.SetMarker(true);
+  sender_.impl_->TrySendPacket(&packet, pacing_info);
+
+  std::vector<RtpSequenceNumberMap::Info> seqno_info =
+      sender_.impl_->GetSentRtpPacketInfos(std::vector<uint16_t>{1});
+
+  EXPECT_THAT(seqno_info, ElementsAre(RtpSequenceNumberMap::Info(
+                              /*timestamp=*/1 - kStartTimestamp,
+                              /*is_first=*/1,
+                              /*is_last=*/1)));
+
+  // Three-packet frame.
+  packet.SetTimestamp(2);
+  packet.SetSequenceNumber(2);
+  packet.set_first_packet_of_frame(true);
+  packet.SetMarker(false);
+  sender_.impl_->TrySendPacket(&packet, pacing_info);
+
+  packet.SetSequenceNumber(3);
+  packet.set_first_packet_of_frame(false);
+  sender_.impl_->TrySendPacket(&packet, pacing_info);
+
+  packet.SetSequenceNumber(4);
+  packet.SetMarker(true);
+  sender_.impl_->TrySendPacket(&packet, pacing_info);
+
+  seqno_info =
+      sender_.impl_->GetSentRtpPacketInfos(std::vector<uint16_t>{2, 3, 4});
+
+  EXPECT_THAT(seqno_info, ElementsAre(RtpSequenceNumberMap::Info(
+                                          /*timestamp=*/2 - kStartTimestamp,
+                                          /*is_first=*/1,
+                                          /*is_last=*/0),
+                                      RtpSequenceNumberMap::Info(
+                                          /*timestamp=*/2 - kStartTimestamp,
+                                          /*is_first=*/0,
+                                          /*is_last=*/0),
+                                      RtpSequenceNumberMap::Info(
+                                          /*timestamp=*/2 - kStartTimestamp,
+                                          /*is_first=*/0,
+                                          /*is_last=*/1)));
+}
+
+}  // namespace webrtc
diff --git a/video/end_to_end_tests/bandwidth_tests.cc b/video/end_to_end_tests/bandwidth_tests.cc
index 16b35d6..6e8e11d 100644
--- a/video/end_to_end_tests/bandwidth_tests.cc
+++ b/video/end_to_end_tests/bandwidth_tests.cc
@@ -205,8 +205,9 @@
 
     ~BweObserver() override {
       // Block until all already posted tasks run to avoid races when such task
-      // accesses |this|.
-      SendTask(RTC_FROM_HERE, task_queue_, [] {});
+      // accesses |this|. Also make sure we free |rtp_rtcp_| on the correct
+      // thread/task queue.
+      SendTask(RTC_FROM_HERE, task_queue_, [this]() { rtp_rtcp_ = nullptr; });
     }
 
     std::unique_ptr<test::PacketTransport> CreateReceiveTransport(
diff --git a/video/video_send_stream_tests.cc b/video/video_send_stream_tests.cc
index e386538..63acb80 100644
--- a/video/video_send_stream_tests.cc
+++ b/video/video_send_stream_tests.cc
@@ -1627,12 +1627,18 @@
   static const int kRembRespectedBitrateBps = 100000;
   class BitrateObserver : public test::SendTest {
    public:
-    BitrateObserver()
+    explicit BitrateObserver(TaskQueueBase* task_queue)
         : SendTest(kDefaultTimeoutMs),
+          task_queue_(task_queue),
           retranmission_rate_limiter_(Clock::GetRealTimeClock(), 1000),
           stream_(nullptr),
           bitrate_capped_(false) {}
 
+    ~BitrateObserver() override {
+      // Make sure we free |rtp_rtcp_| in the same context as we constructed it.
+      SendTask(RTC_FROM_HERE, task_queue_, [this]() { rtp_rtcp_ = nullptr; });
+    }
+
    private:
     Action OnSendRtp(const uint8_t* packet, size_t length) override {
       if (RtpHeaderParser::IsRtcp(packet, length))
@@ -1690,12 +1696,13 @@
           << "Timeout while waiting for low bitrate stats after REMB.";
     }
 
+    TaskQueueBase* const task_queue_;
     std::unique_ptr<RtpRtcp> rtp_rtcp_;
     std::unique_ptr<internal::TransportAdapter> feedback_transport_;
     RateLimiter retranmission_rate_limiter_;
     VideoSendStream* stream_;
     bool bitrate_capped_;
-  } test;
+  } test(task_queue());
 
   RunBaseTest(&test);
 }