[feat] implementation for qos module

src/channel/rtp_channel/rtp_video_receiver.cpp

@@ -5,10 +5,18 @@
 #define NV12_BUFFER_SIZE (1280 * 720 * 3 / 2)
 #define RTCP_RR_INTERVAL 1000
 
-RtpVideoReceiver::RtpVideoReceiver() {}
+RtpVideoReceiver::RtpVideoReceiver()
+    : receive_side_congestion_controller_(
+          [this](std::vector<std::unique_ptr<RtcpPacket>> packets) {
+            SendCombinedRtcpPacket(std::move(packets));
+          }) {}
 
 RtpVideoReceiver::RtpVideoReceiver(std::shared_ptr<IOStatistics> io_statistics)
-    : io_statistics_(io_statistics) {
+    : io_statistics_(io_statistics),
+      receive_side_congestion_controller_(
+          [this](std::vector<std::unique_ptr<RtcpPacket>> packets) {
+            SendCombinedRtcpPacket(std::move(packets));
+          }) {
   rtcp_thread_ = std::thread(&RtpVideoReceiver::RtcpThread, this);
 }
 
@@ -31,6 +39,16 @@ void RtpVideoReceiver::InsertRtpPacket(RtpPacket& rtp_packet) {
     rtp_statistics_->Start();
   }
 
+  RtpPacketReceived* rtp_packet_received;
+  rtp_packet_received = dynamic_cast<RtpPacketReceived*>(&rtp_packet);
+  rtp_packet_received->set_arrival_time(
+      std::chrono::system_clock::now().time_since_epoch().count());
+  rtp_packet_received->set_ecn(EcnMarking::kEct0);
+  rtp_packet_received->set_recovered(false);
+  rtp_packet_received->set_payload_type_frequency(0);
+  receive_side_congestion_controller_.OnReceivedPacket(
+      *rtp_packet_received, ReceiveSideCongestionController::MediaType::VIDEO);
+
   last_recv_bytes_ = (uint32_t)rtp_packet.PayloadSize();
   total_rtp_payload_recv_ += (uint32_t)rtp_packet.PayloadSize();
   total_rtp_packets_recv_++;
@@ -327,6 +345,9 @@ int RtpVideoReceiver::SendRtcpRR(RtcpReceiverReport& rtcp_rr) {
   return 0;
 }
 
+void RtpVideoReceiver::SendCombinedRtcpPacket(
+    std::vector<std::unique_ptr<RtcpPacket>> packets) {}
+
 bool RtpVideoReceiver::CheckIsTimeSendRR() {
   uint32_t now_ts = static_cast<uint32_t>(
       std::chrono::duration_cast<std::chrono::milliseconds>(

src/channel/rtp_channel/rtp_video_receiver.h

@@ -44,6 +44,8 @@ class RtpVideoReceiver : public ThreadBase {
   bool CheckIsTimeSendRR();
   int SendRtcpRR(RtcpReceiverReport& rtcp_rr);
 
+  void SendCombinedRtcpPacket(std::vector<std::unique_ptr<RtcpPacket>> packets);
+
  private:
   bool Process() override;
   void RtcpThread();
@@ -86,7 +88,7 @@ class RtpVideoReceiver : public ThreadBase {
   int rtcp_tcc_interval_ms_ = 200;
 
  private:
-  ReceiveSideCongestionController congestion_controller_;
+  ReceiveSideCongestionController receive_side_congestion_controller_;
 };
 
 #endif

src/common/array_view.h

@@ -90,10 +90,10 @@ class ArrayView final : public array_view_internal::ArrayViewBase<T, Size> {
   template <typename U>
   ArrayView(U* data, size_t size)
       : array_view_internal::ArrayViewBase<T, Size>::ArrayViewBase(data, size) {
-    RTC_DCHECK_EQ(size == 0 ? nullptr : data, this->data());
+    // RTC_DCHECK_EQ(size == 0 ? nullptr : data, this->data());
-    RTC_DCHECK_EQ(size, this->size());
+    // RTC_DCHECK_EQ(size, this->size());
-    RTC_DCHECK_EQ(!this->data(),
+    // RTC_DCHECK_EQ(!this->data(),
-                  this->size() == 0);  // data is null iff size == 0.
+    //               this->size() == 0);  // data is null iff size == 0.
   }
 
   // Construct an empty ArrayView. Note that fixed-size ArrayViews of size > 0
@@ -105,7 +105,7 @@ class ArrayView final : public array_view_internal::ArrayViewBase<T, Size> {
       : ArrayView(static_cast<T*>(nullptr), size) {
     static_assert(Size == 0 || Size == array_view_internal::kArrayViewVarSize,
                   "");
-    RTC_DCHECK_EQ(0, size);
+    // RTC_DCHECK_EQ(0, size);
   }
 
   // Construct an ArrayView from a C-style array.
@@ -182,8 +182,8 @@ class ArrayView final : public array_view_internal::ArrayViewBase<T, Size> {
   // const, because the ArrayView doesn't own the array. (To prevent mutation,
   // use a const element type.)
   T& operator[](size_t idx) const {
-    RTC_DCHECK_LT(idx, this->size());
+    // RTC_DCHECK_LT(idx, this->size());
-    RTC_DCHECK(this->data());
+    // RTC_DCHECK(this->data());
     return this->data()[idx];
   }
   T* begin() const { return this->data(); }

src/common/enc_mark.h

@@ -0,0 +1,31 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2025-01-08
+ * Copyright (c) 2025 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _ENC_MARK_H_
+#define _ENC_MARK_H_
+
+// L4S Explicit Congestion Notification (ECN) .
+// https://www.rfc-editor.org/rfc/rfc9331.html ECT stands for ECN-Capable
+// Transport and CE stands for Congestion Experienced.
+
+// RFC-3168, Section 5
+// +-----+-----+
+// | ECN FIELD |
+// +-----+-----+
+//   ECT   CE         [Obsolete] RFC 2481 names for the ECN bits.
+//    0     0         Not-ECT
+//    0     1         ECT(1)
+//    1     0         ECT(0)
+//    1     1         CE
+
+enum class EcnMarking {
+  kNotEct = 0,  // Not ECN-Capable Transport
+  kEct1 = 1,    // ECN-Capable Transport
+  kEct0 = 2,    // Not used by L4s (or webrtc.)
+  kCe = 3,      // Congestion experienced
+};
+
+#endif

src/common/mod_ops.h

@@ -0,0 +1,130 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2025-01-08
+ * Copyright (c) 2025 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _MOD_OPS_H_
+#define _MOD_OPS_H_
+
+#include <algorithm>
+#include <type_traits>
+
+template <unsigned long M>                                    // NOLINT
+inline unsigned long Add(unsigned long a, unsigned long b) {  // NOLINT
+  // RTC_DCHECK_LT(a, M);
+  unsigned long t = M - b % M;  // NOLINT
+  unsigned long res = a - t;    // NOLINT
+  if (t > a) return res + M;
+  return res;
+}
+
+template <unsigned long M>                                         // NOLINT
+inline unsigned long Subtract(unsigned long a, unsigned long b) {  // NOLINT
+  // RTC_DCHECK_LT(a, M);
+  unsigned long sub = b % M;  // NOLINT
+  if (a < sub) return M - (sub - a);
+  return a - sub;
+}
+
+// Calculates the forward difference between two wrapping numbers.
+//
+// Example:
+// uint8_t x = 253;
+// uint8_t y = 2;
+//
+// ForwardDiff(x, y) == 5
+//
+//   252   253   254   255    0     1     2     3
+// #################################################
+// |     |  x  |     |     |     |     |  y  |     |
+// #################################################
+//          |----->----->----->----->----->
+//
+// ForwardDiff(y, x) == 251
+//
+//   252   253   254   255    0     1     2     3
+// #################################################
+// |     |  x  |     |     |     |     |  y  |     |
+// #################################################
+// -->----->                              |----->---
+//
+// If M > 0 then wrapping occurs at M, if M == 0 then wrapping occurs at the
+// largest value representable by T.
+template <typename T, T M>
+inline typename std::enable_if<(M > 0), T>::type ForwardDiff(T a, T b) {
+  static_assert(std::is_unsigned<T>::value,
+                "Type must be an unsigned integer.");
+  // RTC_DCHECK_LT(a, M);
+  // RTC_DCHECK_LT(b, M);
+  return a <= b ? b - a : M - (a - b);
+}
+
+template <typename T, T M>
+inline typename std::enable_if<(M == 0), T>::type ForwardDiff(T a, T b) {
+  static_assert(std::is_unsigned<T>::value,
+                "Type must be an unsigned integer.");
+  return b - a;
+}
+
+template <typename T>
+inline T ForwardDiff(T a, T b) {
+  return ForwardDiff<T, 0>(a, b);
+}
+
+// Calculates the reverse difference between two wrapping numbers.
+//
+// Example:
+// uint8_t x = 253;
+// uint8_t y = 2;
+//
+// ReverseDiff(y, x) == 5
+//
+//   252   253   254   255    0     1     2     3
+// #################################################
+// |     |  x  |     |     |     |     |  y  |     |
+// #################################################
+//          <-----<-----<-----<-----<-----|
+//
+// ReverseDiff(x, y) == 251
+//
+//   252   253   254   255    0     1     2     3
+// #################################################
+// |     |  x  |     |     |     |     |  y  |     |
+// #################################################
+// ---<-----|                             |<-----<--
+//
+// If M > 0 then wrapping occurs at M, if M == 0 then wrapping occurs at the
+// largest value representable by T.
+template <typename T, T M>
+inline typename std::enable_if<(M > 0), T>::type ReverseDiff(T a, T b) {
+  static_assert(std::is_unsigned<T>::value,
+                "Type must be an unsigned integer.");
+  // RTC_DCHECK_LT(a, M);
+  // RTC_DCHECK_LT(b, M);
+  return b <= a ? a - b : M - (b - a);
+}
+
+template <typename T, T M>
+inline typename std::enable_if<(M == 0), T>::type ReverseDiff(T a, T b) {
+  static_assert(std::is_unsigned<T>::value,
+                "Type must be an unsigned integer.");
+  return a - b;
+}
+
+template <typename T>
+inline T ReverseDiff(T a, T b) {
+  return ReverseDiff<T, 0>(a, b);
+}
+
+// Calculates the minimum distance between to wrapping numbers.
+//
+// The minimum distance is defined as min(ForwardDiff(a, b), ReverseDiff(a, b))
+template <typename T, T M = 0>
+inline T MinDiff(T a, T b) {
+  static_assert(std::is_unsigned<T>::value,
+                "Type must be an unsigned integer.");
+  return (std::min)(ForwardDiff<T, M>(a, b), ReverseDiff<T, M>(a, b));
+}
+
+#endif

src/common/sequence_number_unwrapper.h

@@ -0,0 +1,73 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2025-01-08
+ * Copyright (c) 2025 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _SEQUENCE_NUMBER_UNWRAPPER_H_
+#define _SEQUENCE_NUMBER_UNWRAPPER_H_
+
+#include <stdint.h>
+
+#include <limits>
+#include <optional>
+#include <type_traits>
+
+#include "sequence_number_util.h"
+
+// A sequence number unwrapper where the first unwrapped value equals the
+// first value being unwrapped.
+template <typename T, T M = 0>
+class SeqNumUnwrapper {
+  static_assert(
+      std::is_unsigned<T>::value &&
+          std::numeric_limits<T>::max() < std::numeric_limits<int64_t>::max(),
+      "Type unwrapped must be an unsigned integer smaller than int64_t.");
+
+ public:
+  // Unwraps `value` and updates the internal state of the unwrapper.
+  int64_t Unwrap(T value) {
+    if (!last_value_) {
+      last_unwrapped_ = {value};
+    } else {
+      last_unwrapped_ += Delta(*last_value_, value);
+    }
+
+    last_value_ = value;
+    return last_unwrapped_;
+  }
+
+  // Returns the `value` without updating the internal state of the unwrapper.
+  int64_t PeekUnwrap(T value) const {
+    if (!last_value_) {
+      return value;
+    }
+    return last_unwrapped_ + Delta(*last_value_, value);
+  }
+
+  // Resets the unwrapper to its initial state. Unwrapped sequence numbers will
+  // being at 0 after resetting.
+  void Reset() {
+    last_unwrapped_ = 0;
+    last_value_.reset();
+  }
+
+ private:
+  static int64_t Delta(T last_value, T new_value) {
+    constexpr int64_t kBackwardAdjustment =
+        M == 0 ? int64_t{std::numeric_limits<T>::max()} + 1 : M;
+    int64_t result = ForwardDiff<T, M>(last_value, new_value);
+    if (!AheadOrAt<T, M>(new_value, last_value)) {
+      result -= kBackwardAdjustment;
+    }
+    return result;
+  }
+
+  int64_t last_unwrapped_ = 0;
+  std::optional<T> last_value_;
+};
+
+using RtpTimestampUnwrapper = SeqNumUnwrapper<uint32_t>;
+using RtpSequenceNumberUnwrapper = SeqNumUnwrapper<uint16_t>;
+
+#endif

src/common/sequence_number_util.h

@@ -0,0 +1,73 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2025-01-08
+ * Copyright (c) 2025 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _SEQUENCE_NUMBER_UTIL_H_
+#define _SEQUENCE_NUMBER_UTIL_H_
+
+#include <limits>
+#include <type_traits>
+
+#include "mod_ops.h"
+
+// Test if the sequence number `a` is ahead or at sequence number `b`.
+//
+// If `M` is an even number and the two sequence numbers are at max distance
+// from each other, then the sequence number with the highest value is
+// considered to be ahead.
+template <typename T, T M>
+inline typename std::enable_if<(M > 0), bool>::type AheadOrAt(T a, T b) {
+  static_assert(std::is_unsigned<T>::value,
+                "Type must be an unsigned integer.");
+  const T maxDist = M / 2;
+  if (!(M & 1) && MinDiff<T, M>(a, b) == maxDist) return b < a;
+  return ForwardDiff<T, M>(b, a) <= maxDist;
+}
+
+template <typename T, T M>
+inline typename std::enable_if<(M == 0), bool>::type AheadOrAt(T a, T b) {
+  static_assert(std::is_unsigned<T>::value,
+                "Type must be an unsigned integer.");
+  const T maxDist = std::numeric_limits<T>::max() / 2 + T(1);
+  if (a - b == maxDist) return b < a;
+  return ForwardDiff(b, a) < maxDist;
+}
+
+template <typename T>
+inline bool AheadOrAt(T a, T b) {
+  return AheadOrAt<T, 0>(a, b);
+}
+
+// Test if the sequence number `a` is ahead of sequence number `b`.
+//
+// If `M` is an even number and the two sequence numbers are at max distance
+// from each other, then the sequence number with the highest value is
+// considered to be ahead.
+template <typename T, T M = 0>
+inline bool AheadOf(T a, T b) {
+  static_assert(std::is_unsigned<T>::value,
+                "Type must be an unsigned integer.");
+  return a != b && AheadOrAt<T, M>(a, b);
+}
+
+// Comparator used to compare sequence numbers in a continuous fashion.
+//
+// WARNING! If used to sort sequence numbers of length M then the interval
+//          covered by the sequence numbers may not be larger than floor(M/2).
+template <typename T, T M = 0>
+struct AscendingSeqNumComp {
+  bool operator()(T a, T b) const { return AheadOf<T, M>(a, b); }
+};
+
+// Comparator used to compare sequence numbers in a continuous fashion.
+//
+// WARNING! If used to sort sequence numbers of length M then the interval
+//          covered by the sequence numbers may not be larger than floor(M/2).
+template <typename T, T M = 0>
+struct DescendingSeqNumComp {
+  bool operator()(T a, T b) const { return AheadOf<T, M>(b, a); }
+};
+
+#endif

src/qos/congestion_control_feedback.cpp

@@ -96,6 +96,10 @@ uint16_t To2BitEcn(EcnMarking ecn_marking) {
       return kEcnEct0 << 13;
     case EcnMarking::kCe:
       return kEcnCe << 13;
+    default: {
+      LOG_FATAL("Unexpected ecn marking: {}", static_cast<int>(ecn_marking));
+      return 0;
+    }
   }
 }
 
@@ -193,6 +197,8 @@ bool CongestionControlFeedback::Create(uint8_t* buffer, size_t* position,
       ByteWriter<uint16_t>::WriteBigEndian(&buffer[*position], 0);
       *position += 2;
     }
+
+    return true;
   };
 
   ArrayView<const PacketInfo> remaining(packets_);
@@ -255,7 +261,7 @@ size_t CongestionControlFeedback::BlockLength() const {
   return total_size;
 }
 
-bool CongestionControlFeedback::Parse(const rtcp::CommonHeader& packet) {
+bool CongestionControlFeedback::Parse(const RtcpCommonHeader& packet) {
   const uint8_t* payload = packet.payload();
   const uint8_t* payload_end = packet.payload() + packet.payload_size_bytes();
 
@@ -291,12 +297,11 @@ bool CongestionControlFeedback::Parse(const rtcp::CommonHeader& packet) {
 
       uint16_t seq_no = base_seqno + i;
       bool received = (packet_info & 0x8000);
-      packets_.push_back(
+      packets_.push_back(PacketInfo{ssrc, seq_no,
-          {.ssrc = ssrc,
+                                    received
-           .sequence_number = seq_no,
+                                        ? AtoToTimeDelta(packet_info)
-           .arrival_time_offset = received ? AtoToTimeDelta(packet_info)
+                                        : std::numeric_limits<int64_t>::min(),
-                                           : TimeDelta::MinusInfinity(),
+                                    ToEcnMarking(packet_info)});
-           .ecn = ToEcnMarking(packet_info)});
     }
     if (num_reports % 2) {
       // 2 bytes padding

src/qos/congestion_control_feedback.h

@@ -13,29 +13,9 @@
 #include <vector>
 
 #include "array_view.h"
+#include "enc_mark.h"
 #include "rtp_feedback.h"
 
-// L4S Explicit Congestion Notification (ECN) .
-// https://www.rfc-editor.org/rfc/rfc9331.html ECT stands for ECN-Capable
-// Transport and CE stands for Congestion Experienced.
-
-// RFC-3168, Section 5
-// +-----+-----+
-// | ECN FIELD |
-// +-----+-----+
-//   ECT   CE         [Obsolete] RFC 2481 names for the ECN bits.
-//    0     0         Not-ECT
-//    0     1         ECT(1)
-//    1     0         ECT(0)
-//    1     1         CE
-
-enum class EcnMarking {
-  kNotEct = 0,  // Not ECN-Capable Transport
-  kEct1 = 1,    // ECN-Capable Transport
-  kEct0 = 2,    // Not used by L4s (or webrtc.)
-  kCe = 3,      // Congestion experienced
-};
-
 // Congestion control feedback message as specified in
 // https://www.rfc-editor.org/rfc/rfc8888.html
 class CongestionControlFeedback : public RtpFeedback {
@@ -58,7 +38,7 @@ class CongestionControlFeedback : public RtpFeedback {
                             uint32_t report_timestamp_compact_ntp);
   CongestionControlFeedback() = default;
 
-  bool Parse(const CommonHeader& packet);
+  bool Parse(const RtcpCommonHeader& packet);
 
   ArrayView<const PacketInfo> packets() const { return packets_; }
 

src/qos/congestion_control_feedback_generator.cpp

@@ -21,7 +21,7 @@ CongestionControlFeedbackGenerator::CongestionControlFeedbackGenerator(
     : rtcp_sender_(std::move(rtcp_sender)) {}
 
 void CongestionControlFeedbackGenerator::OnReceivedPacket(
-    const RtpPacketReceived& packet) {
+    RtpPacketReceived& packet) {
   marker_bit_seen_ |= packet.Marker();
   if (!first_arrival_time_since_feedback_) {
     first_arrival_time_since_feedback_ = packet.arrival_time();
@@ -63,19 +63,19 @@ int64_t CongestionControlFeedbackGenerator::Process(int64_t now_ms) {
 }
 
 void CongestionControlFeedbackGenerator::OnSendBandwidthEstimateChanged(
-    DataRate estimate) {
+    int64_t estimate) {
   // Feedback reports should max occupy 5% of total bandwidth.
   max_feedback_rate_ = estimate * 0.05;
 }
 
 void CongestionControlFeedbackGenerator::SetTransportOverhead(
-    DataSize overhead_per_packet) {
+    int64_t overhead_per_packet) {
   packet_overhead_ = overhead_per_packet;
 }
 
 void CongestionControlFeedbackGenerator::SendFeedback(int64_t now_ms) {
   uint32_t compact_ntp = ConvertToCompactNtp(now_ms);
-  std::vector<rtcp::CongestionControlFeedback::PacketInfo> rtcp_packet_info;
+  std::vector<CongestionControlFeedback::PacketInfo> rtcp_packet_info;
   for (auto& [unused, tracker] : feedback_trackers_) {
     tracker.AddPacketsToFeedback(now_ms, rtcp_packet_info);
   }
@@ -83,18 +83,18 @@ void CongestionControlFeedbackGenerator::SendFeedback(int64_t now_ms) {
   marker_bit_seen_ = false;
   first_arrival_time_since_feedback_ = std::nullopt;
 
-  auto feedback = std::make_unique<rtcp::CongestionControlFeedback>(
+  auto feedback = std::make_unique<CongestionControlFeedback>(
       std::move(rtcp_packet_info), compact_ntp);
   CalculateNextPossibleSendTime(feedback->BlockLength(), now_ms);
 
-  std::vector<std::unique_ptr<rtcp::RtcpPacket>> rtcp_packets;
+  std::vector<std::unique_ptr<RtcpPacket>> rtcp_packets;
   rtcp_packets.push_back(std::move(feedback));
   rtcp_sender_(std::move(rtcp_packets));
 }
 
 void CongestionControlFeedbackGenerator::CalculateNextPossibleSendTime(
     int64_t feedback_size, int64_t now_ms) {
-  int64_t time_since_last_sent = now - last_feedback_sent_time_;
+  int64_t time_since_last_sent = now_ms - last_feedback_sent_time_;
   size_t debt_payed = time_since_last_sent * max_feedback_rate_;
   send_rate_debt_ =
       debt_payed > send_rate_debt_ ? 0 : send_rate_debt_ - debt_payed;

src/qos/congestion_control_feedback_generator.h

@@ -10,43 +10,22 @@
 #include <optional>
 #include <vector>
 
+#include "congestion_control_feedback_tracker.h"
 #include "rtcp_packet.h"
 #include "rtp_packet_received.h"
 
-class RtpTransportFeedbackGenerator {
+class CongestionControlFeedbackGenerator {
  public:
-  // Function intented to be used for sending RTCP messages generated by an
+  CongestionControlFeedbackGenerator(RtcpSender feedback_sender);
-  // implementation of this class.
-  using RtcpSender =
-      std::function<void(std::vector<std::unique_ptr<RtcpPacket>> packets)>;
-  virtual ~RtpTransportFeedbackGenerator() = default;
-
-  virtual void OnReceivedPacket(const RtpPacketReceived& packet) = 0;
-
-  // Sends periodic feedback if it is time to send it.
-  // Returns time until next call to Process should be made.
-  virtual int64_t Process(int64_t now) = 0;
-
-  virtual void OnSendBandwidthEstimateChanged(int64_t estimate) = 0;
-
-  // Overhead from transport layers below RTP. Ie, IP, SRTP.
-  virtual void SetTransportOverhead(DataSize overhead_per_packet) = 0;
-};
-
-class CongestionControlFeedbackGenerator
-    : public RtpTransportFeedbackGenerator {
- public:
-  CongestionControlFeedbackGenerator(
-      RtpTransportFeedbackGenerator::RtcpSender feedback_sender);
   ~CongestionControlFeedbackGenerator() = default;
 
-  void OnReceivedPacket(const RtpPacketReceived& packet) override;
+  void OnReceivedPacket(RtpPacketReceived& packet);
 
-  void OnSendBandwidthEstimateChanged(int64_t estimate) override;
+  void OnSendBandwidthEstimateChanged(int64_t estimate);
 
-  int64_t Process(int64_t now_ms) override;
+  int64_t Process(int64_t now_ms);
 
-  void SetTransportOverhead(DataSize overhead_per_packet) override;
+  void SetTransportOverhead(int64_t overhead_per_packet);
 
  private:
   int64_t NextFeedbackTime() const;
@@ -55,6 +34,8 @@ class CongestionControlFeedbackGenerator
 
   void CalculateNextPossibleSendTime(int64_t feedback_size, int64_t now_ms);
 
+  const RtcpSender rtcp_sender_;
+
  private:
   // Feedback should not use more than 5% of the configured send bandwidth
   // estimate. Min and max duration between feedback is configurable using field
@@ -73,6 +54,9 @@ class CongestionControlFeedbackGenerator
   int64_t packet_overhead_ = 0;
   int64_t send_rate_debt_ = 0;
 
+  std::map</*ssrc=*/uint32_t, CongestionControlFeedbackTracker>
+      feedback_trackers_;
+
   std::optional<int64_t> first_arrival_time_since_feedback_;
   int64_t next_possible_feedback_send_time_ = 0;
   int64_t last_feedback_sent_time_ = 0;

src/qos/congestion_control_feedback_tracker.cpp

@@ -1,5 +1,6 @@
 #include "congestion_control_feedback_tracker.h"
 
+#include <algorithm>
 #include <cstdint>
 #include <tuple>
 #include <vector>
@@ -7,7 +8,7 @@
 #include "log.h"
 
 void CongestionControlFeedbackTracker::ReceivedPacket(
-    const RtpPacketReceived& packet) {
+    RtpPacketReceived& packet) {
   int64_t unwrapped_sequence_number =
       unwrapper_.Unwrap(packet.SequenceNumber());
   if (last_sequence_number_in_feedback_ &&
@@ -25,10 +26,8 @@ void CongestionControlFeedbackTracker::ReceivedPacket(
     // received.
     last_sequence_number_in_feedback_ = unwrapped_sequence_number - 1;
   }
-  packets_.push_back({.ssrc = packet.Ssrc(),
+  packets_.push_back({packet.Ssrc(), unwrapped_sequence_number,
-                      .unwrapped_sequence_number = unwrapped_sequence_number,
+                      packet.arrival_time(), packet.ecn()});
-                      .arrival_time = packet.arrival_time(),
-                      .ecn = packet.ecn()});
 }
 
 void CongestionControlFeedbackTracker::AddPacketsToFeedback(
@@ -37,10 +36,11 @@ void CongestionControlFeedbackTracker::AddPacketsToFeedback(
   if (packets_.empty()) {
     return;
   }
-  absl::c_sort(packets_, [](const PacketInfo& a, const PacketInfo& b) {
+  std::sort(packets_.begin(), packets_.end(),
-    return std::tie(a.unwrapped_sequence_number, a.arrival_time) <
+            [](const PacketInfo& a, const PacketInfo& b) {
-           std::tie(b.unwrapped_sequence_number, b.arrival_time);
+              return std::tie(a.unwrapped_sequence_number, a.arrival_time) <
-  });
+                     std::tie(b.unwrapped_sequence_number, b.arrival_time);
+            });
   if (!last_sequence_number_in_feedback_) {
     last_sequence_number_in_feedback_ =
         packets_.front().unwrapped_sequence_number - 1;
@@ -61,7 +61,7 @@ void CongestionControlFeedbackTracker::AddPacketsToFeedback(
     }
 
     EcnMarking ecn = EcnMarking::kNotEct;
-    TimeDelta arrival_time_offset = TimeDelta::MinusInfinity();
+    int64_t arrival_time_offset = std::numeric_limits<int64_t>::min();
 
     if (sequence_number == packet_it->unwrapped_sequence_number) {
       arrival_time_offset = feedback_time - packet_it->arrival_time;
@@ -83,11 +83,8 @@ void CongestionControlFeedbackTracker::AddPacketsToFeedback(
         ++packet_it;
       }
     }  // else - the packet has not been received yet.
-    packet_feedback.push_back(
+    packet_feedback.push_back({ssrc, static_cast<uint16_t>(sequence_number),
-        {.ssrc = ssrc,
+                               arrival_time_offset, ecn});
-         .sequence_number = static_cast<uint16_t>(sequence_number),
-         .arrival_time_offset = arrival_time_offset,
-         .ecn = ecn});
   }
   last_sequence_number_in_feedback_ = packets_.back().unwrapped_sequence_number;
   packets_.clear();

src/qos/congestion_control_feedback_tracker.h

@@ -11,13 +11,15 @@
 #include <vector>
 
 #include "congestion_control_feedback.h"
+#include "enc_mark.h"
 #include "rtp_packet_received.h"
+#include "sequence_number_unwrapper.h"
 
 class CongestionControlFeedbackTracker {
  public:
   CongestionControlFeedbackTracker() = default;
 
-  void ReceivedPacket(const RtpPacketReceived& packet);
+  void ReceivedPacket(RtpPacketReceived& packet);
 
   // Adds received packets to `packet_feedback`
   // RTP sequence numbers are continous from the last created feedback unless

src/qos/receive_side_congestion_controller.cpp

@@ -11,6 +11,7 @@
 #include "receive_side_congestion_controller.h"
 
 #include <algorithm>
+#include <chrono>
 #include <memory>
 #include <utility>
 
@@ -18,99 +19,33 @@ namespace {
 static const uint32_t kTimeOffsetSwitchThreshold = 30;
 }  // namespace
 
-void ReceiveSideCongestionController::OnRttUpdate(int64_t avg_rtt_ms,
-                                                  int64_t max_rtt_ms) {
-  std::lock_guard<std::mutex> guard(mutex_);
-  rbe_->OnRttUpdate(avg_rtt_ms, max_rtt_ms);
-}
-
-void ReceiveSideCongestionController::RemoveStream(uint32_t ssrc) {
-  std::lock_guard<std::mutex> guard(mutex_);
-  rbe_->RemoveStream(ssrc);
-}
-
-int64_t ReceiveSideCongestionController::LatestReceiveSideEstimate() const {
-  std::lock_guard<std::mutex> guard(mutex_);
-  return rbe_->LatestEstimate();
-}
-
-void ReceiveSideCongestionController::PickEstimator(
-    bool has_absolute_send_time) {
-  if (has_absolute_send_time) {
-    // If we see AST in header, switch RBE strategy immediately.
-    if (!using_absolute_send_time_) {
-      RTC_LOG(LS_INFO)
-          << "WrappingBitrateEstimator: Switching to absolute send time RBE.";
-      using_absolute_send_time_ = true;
-      // rbe_ = std::make_unique<RemoteBitrateEstimatorAbsSendTime>(
-      //     env_, &remb_throttler_);
-    }
-    packets_since_absolute_send_time_ = 0;
-  } else {
-    // When we don't see AST, wait for a few packets before going back to TOF.
-    if (using_absolute_send_time_) {
-      ++packets_since_absolute_send_time_;
-      if (packets_since_absolute_send_time_ >= kTimeOffsetSwitchThreshold) {
-        RTC_LOG(LS_INFO)
-            << "WrappingBitrateEstimator: Switching to transmission "
-               "time offset RBE.";
-        using_absolute_send_time_ = false;
-        // rbe_ = std::make_unique<RemoteBitrateEstimatorSingleStream>(
-        //     env_, &remb_throttler_);
-      }
-    }
-  }
-}
-
 ReceiveSideCongestionController::ReceiveSideCongestionController(
-    const Environment& env,
+    RtcpSender feedback_sender)
-    TransportSequenceNumberFeedbackGenenerator::RtcpSender feedback_sender,
+    : congestion_control_feedback_generator_(feedback_sender),
-    RembThrottler::RembSender remb_sender,
-    absl::Nullable<NetworkStateEstimator*> network_state_estimator)
-    : env_(env),
-      // remb_throttler_(std::move(remb_sender), &env_.clock()),,
-      congestion_control_feedback_generator_(env, feedback_sender),
-      // rbe_(std::make_unique<RemoteBitrateEstimatorSingleStream>(
-      //     env_, &remb_throttler_)),
       using_absolute_send_time_(false),
-      packets_since_absolute_send_time_(0) {
+      packets_since_absolute_send_time_(0) {}
-  FieldTrialParameter<bool> force_send_rfc8888_feedback("force_send", false);
-  ParseFieldTrial(
-      {&force_send_rfc8888_feedback},
-      env.field_trials().Lookup("WebRTC-RFC8888CongestionControlFeedback"));
-  if (force_send_rfc8888_feedback) {
-    EnablSendCongestionControlFeedbackAccordingToRfc8888();
-  }
-}
-
-void ReceiveSideCongestionController::
-    EnablSendCongestionControlFeedbackAccordingToRfc8888() {
-  // RTC_DCHECK_RUN_ON(&sequence_checker_);
-  send_rfc8888_congestion_feedback_ = true;
-}
 
 void ReceiveSideCongestionController::OnReceivedPacket(
-    const RtpPacketReceived& packet, MediaType media_type) {
+    RtpPacketReceived& packet, MediaType media_type) {
-  if (send_rfc8888_congestion_feedback_) {
+  // RTC_DCHECK_RUN_ON(&sequence_checker_);
-    // RTC_DCHECK_RUN_ON(&sequence_checker_);
+  congestion_control_feedback_generator_.OnReceivedPacket(packet);
-    congestion_control_feedback_generator_.OnReceivedPacket(packet);
+  return;
-    return;
-  }
 }
 
 void ReceiveSideCongestionController::OnBitrateChanged(int bitrate_bps) {
   // RTC_DCHECK_RUN_ON(&sequence_checker_);
-  int64_t send_bandwidth_estimate = int64_t::BitsPerSec(bitrate_bps);
+  int64_t send_bandwidth_estimate = bitrate_bps;
   congestion_control_feedback_generator_.OnSendBandwidthEstimateChanged(
       send_bandwidth_estimate);
 }
 
 int64_t ReceiveSideCongestionController::MaybeProcess() {
-  int64_t now = env_.clock().CurrentTime();
+  auto now = std::chrono::system_clock::now();
-  if (send_rfc8888_congestion_feedback_) {
+  int64_t now_ms = std::chrono::duration_cast<std::chrono::milliseconds>(
-    // RTC_DCHECK_RUN_ON(&sequence_checker_);
+                       now.time_since_epoch())
-    return congestion_control_feedback_generator_.Process(now);
+                       .count();
-  }
+  // RTC_DCHECK_RUN_ON(&sequence_checker_);
+  return congestion_control_feedback_generator_.Process(now_ms);
 }
 
 void ReceiveSideCongestionController::SetMaxDesiredReceiveBitrate(

src/qos/receive_side_congestion_controller.h

@@ -17,14 +17,11 @@ class ReceiveSideCongestionController {
   enum MediaType { VIDEO, AUDIO, DATA };
 
  public:
-  ReceiveSideCongestionController();
+  ReceiveSideCongestionController(RtcpSender feedback_sender);
-  ~ReceiveSideCongestionController() override = default;
+  ~ReceiveSideCongestionController() = default;
 
  public:
-  void OnReceivedPacket(const RtpPacketReceived& packet, MediaType media_type);
+  void OnReceivedPacket(RtpPacketReceived& packet, MediaType media_type);
-
-  // Implements CallStatsObserver.
-  void OnRttUpdate(int64_t avg_rtt_ms, int64_t max_rtt_ms) override;
 
   // This is send bitrate, used to control the rate of feedback messages.
   void OnBitrateChanged(int bitrate_bps);
@@ -35,21 +32,11 @@ class ReceiveSideCongestionController {
 
   void SetTransportOverhead(int64_t overhead_per_packet);
 
-  // Returns latest receive side bandwidth estimation.
-  // Returns zero if receive side bandwidth estimation is unavailable.
-  int64_t LatestReceiveSideEstimate() const;
-
-  // Removes stream from receive side bandwidth estimation.
-  // Noop if receive side bwe is not used or stream doesn't participate in it.
-  void RemoveStream(uint32_t ssrc);
-
   // Runs periodic tasks if it is time to run them, returns time until next
   // call to `MaybeProcess` should be non idle.
   int64_t MaybeProcess();
 
  private:
-  void PickEstimator(bool has_absolute_send_time);
-
   //   RembThrottler remb_throttler_;
 
   // TODO: bugs.webrtc.org/42224904 - Use sequence checker for all usage of
@@ -58,13 +45,11 @@ class ReceiveSideCongestionController {
   // arbitrary thread by external projects.
   //   SequenceChecker sequence_checker_;
 
-  bool send_rfc8888_congestion_feedback_ = false;
   CongestionControlFeedbackGenerator congestion_control_feedback_generator_;
 
   std::mutex mutex_;
-  std::unique_ptr<RemoteBitrateEstimator> rbe_;
   bool using_absolute_send_time_;
-  uint32_t packets_since_absolute_send_time_ RTC_GUARDED_BY(mutex_);
+  uint32_t packets_since_absolute_send_time_;
 };
 
 #endif

src/rtcp/rtcp_packet/common_header.cpp

@@ -24,7 +24,7 @@
 //   --------------------------------+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //
 // Common header for all RTCP packets, 4 octets.
-bool CommonHeader::Parse(const uint8_t* buffer, size_t size_bytes) {
+bool RtcpCommonHeader::Parse(const uint8_t* buffer, size_t size_bytes) {
   const uint8_t kVersion = 2;
 
   if (size_bytes < kHeaderSizeBytes) {

src/rtcp/rtcp_packet/common_header.h

@@ -13,13 +13,13 @@
 #include <stddef.h>
 #include <stdint.h>
 
-class CommonHeader {
+class RtcpCommonHeader {
  public:
   static constexpr size_t kHeaderSizeBytes = 4;
 
-  CommonHeader() {}
+  RtcpCommonHeader() {}
-  CommonHeader(const CommonHeader&) = default;
+  RtcpCommonHeader(const RtcpCommonHeader&) = default;
-  CommonHeader& operator=(const CommonHeader&) = default;
+  RtcpCommonHeader& operator=(const RtcpCommonHeader&) = default;
 
   bool Parse(const uint8_t* buffer, size_t size_bytes);
 

src/rtcp/rtcp_packet/rtcp_packet.h

@@ -11,6 +11,7 @@
 #include <stdint.h>
 
 #include <functional>
+#include <memory>
 #include <vector>
 
 class RtcpPacket {
@@ -59,4 +60,7 @@ class RtcpPacket {
   uint32_t sender_ssrc_ = 0;
 };
 
+using RtcpSender =
+    std::function<void(std::vector<std::unique_ptr<RtcpPacket>> packets)>;
+
 #endif

src/rtp/rtp_packet/rtp_packet.h

@@ -190,7 +190,7 @@ class RtpPacket {
   RtpPacket &operator=(const RtpPacket &rtp_packet);
   RtpPacket &operator=(RtpPacket &&rtp_packet);
 
-  ~RtpPacket();
+  virtual ~RtpPacket();
 
  public:
   // Set Header

src/rtp/rtp_packet/rtp_packet_received.cpp

@@ -1,8 +1,6 @@
 #include "rtp_packet_received.h"
 
 RtpPacketReceived::RtpPacketReceived() = default;
-RtpPacketReceived::RtpPacketReceived(int64_t arrival_time)
-    : arrival_time_(arrival_time) {}
 RtpPacketReceived::RtpPacketReceived(const RtpPacketReceived& packet) = default;
 RtpPacketReceived::RtpPacketReceived(RtpPacketReceived&& packet) = default;
 

src/rtp/rtp_packet/rtp_packet_received.h

@@ -9,13 +9,12 @@
 
 #include <limits>
 
+#include "enc_mark.h"
 #include "rtp_packet.h"
 
 class RtpPacketReceived : public RtpPacket {
  public:
   RtpPacketReceived();
-  explicit RtpPacketReceived(
-      int64_t arrival_time = (std::numeric_limits<int64_t>::min)());
   RtpPacketReceived(const RtpPacketReceived& packet);
   RtpPacketReceived(RtpPacketReceived&& packet);
 
@@ -24,8 +23,29 @@ class RtpPacketReceived : public RtpPacket {
 
   ~RtpPacketReceived();
 
+ public:
+  int64_t arrival_time() const { return arrival_time_; }
+  void set_arrival_time(int64_t time) { arrival_time_ = time; }
+
+  // Explicit Congestion Notification (ECN), RFC-3168, Section 5.
+  // Used by L4S: https://www.rfc-editor.org/rfc/rfc9331.html
+  EcnMarking ecn() const { return ecn_; }
+  void set_ecn(EcnMarking ecn) { ecn_ = ecn; }
+
+  // Flag if packet was recovered via RTX or FEC.
+  bool recovered() const { return recovered_; }
+  void set_recovered(bool value) { recovered_ = value; }
+
+  int payload_type_frequency() const { return payload_type_frequency_; }
+  void set_payload_type_frequency(int value) {
+    payload_type_frequency_ = value;
+  }
+
  private:
-  int64_t arrival_time_ = (std::numeric_limits<int64_t>::min)();
+  int64_t arrival_time_ = std::numeric_limits<int64_t>::min();
+  EcnMarking ecn_ = EcnMarking::kNotEct;
+  int payload_type_frequency_ = 0;
+  bool recovered_ = false;
 };
 
 #endif

xmake.lua

@@ -10,7 +10,8 @@ set_installdir("$(projectdir)/out")
 
 add_defines("ASIO_STANDALONE", "ASIO_HAS_STD_TYPE_TRAITS", "ASIO_HAS_STD_SHARED_PTR", 
     "ASIO_HAS_STD_ADDRESSOF", "ASIO_HAS_STD_ATOMIC", "ASIO_HAS_STD_CHRONO", 
-    "ASIO_HAS_CSTDINT", "ASIO_HAS_STD_ARRAY",  "ASIO_HAS_STD_SYSTEM_ERROR")
+    "ASIO_HAS_CSTDINT", "ASIO_HAS_STD_ARRAY",  "ASIO_HAS_STD_SYSTEM_ERROR",
+    "NOMINMAX")
 
 add_requires("asio 1.24.0", "nlohmann_json 3.11.3", "spdlog 1.14.1", "openfec 1.4.2", "libopus 1.5.1", "openh264 2.4.1", "dav1d 1.4.3", "libyuv 2024.5.21", "aom 3.9.0", {system = false}, {configs = {shared = false}})
 add_packages("asio", "nlohmann_json", "spdlog", "openfec", "libopus", "openh264", "dav1d", "libyuv", "aom")
@@ -76,27 +77,6 @@ target("statistics")
     add_files("src/statistics/*.cpp")
     add_includedirs("src/statistics", {public = true})
 
-target("rtcp")
-    set_kind("object")
-    add_deps("log", "common")
-    add_files("src/rtcp/*.cpp",
-    "src/rtcp/rtcp_packet/*.cpp",
-    "src/rtcp/rtp_feedback/*.cpp")
-    add_includedirs("src/rtcp",
-    "src/rtcp/rtcp_packet",
-    "src/rtcp/rtp_feedback", {public = true})
-
-target("rtp", "qos")
-    set_kind("object")
-    add_deps("log", "frame", "ringbuffer", "thread", "rtcp", "fec", "statistics")
-    add_files("src/rtp/*.cpp", 
-    "src/rtp/rtp_endpoint/*.cpp", 
-    "src/rtp/rtp_packet/*.cpp")
-    add_includedirs("src/rtp", 
-    "src/rtp/rtp_endpoint", 
-    "src/rtp/rtp_packet",
-    "src/qos", {public = true})
-
 target("ice")
     set_kind("object")
     add_deps("log", "common", "ws")
@@ -115,7 +95,44 @@ target("ws")
     set_kind("object")
     add_deps("log")
     add_files("src/ws/*.cpp")
-    add_includedirs("thirdparty/websocketpp/include", {public = true})
+    add_includedirs("src/ws", 
+    "thirdparty/websocketpp/include", {public = true})
+
+target("rtp")
+    set_kind("object")
+    add_deps("log", "frame", "ringbuffer", "thread", "rtcp", "fec", "statistics")
+    add_files("src/rtp/*.cpp", 
+    "src/rtp/rtp_packet/*.cpp")
+    add_includedirs("src/rtp", 
+    "src/rtp/rtp_packet", {public = true})
+
+target("rtcp")
+    set_kind("object")
+    add_deps("log", "common")
+    add_files("src/rtcp/*.cpp",
+    "src/rtcp/rtcp_packet/*.cpp",
+    "src/rtcp/rtp_feedback/*.cpp")
+    add_includedirs("src/rtcp",
+    "src/rtcp/rtcp_packet",
+    "src/rtcp/rtp_feedback", {public = true})
+
+target("qos")
+    set_kind("object")
+    add_deps("log", "rtp")
+    add_files("src/qos/*.cpp")
+    add_includedirs("src/qos", {public = true})
+
+target("channel")
+    set_kind("object")
+    add_deps("log", "rtp", "rtcp", "ice", "qos")
+    add_files("src/channel/*.cpp", "src/channel/rtp_channel/*.cpp")
+    add_includedirs("src/channel", "src/channel/rtp_channel", {public = true})
+
+target("transport")
+    set_kind("object")
+    add_deps("log", "ws", "ice", "channel", "rtp", "rtcp", "statistics", "media")
+    add_files("src/transport/*.cpp")
+    add_includedirs("src/transport", {public = true})
 
 target("media")
     set_kind("object")
@@ -187,41 +204,17 @@ target("media")
     add_includedirs("src/media/audio/encode",
         "src/media/audio/decode", "src/interface", {public = true})
 
-target("qos")
-    set_kind("object")
-    add_deps("log", "rtp")
-    add_files("src/qos/*.cpp")
-    add_includedirs("src/qos", {public = true})
-
--- target("transport")
---     set_kind("object")
---     add_deps("log", "ws", "ice", "qos", "rtp", "rtcp", "statistics", "media")
---     add_files("src/transport/*.cpp")
---     add_includedirs("src/ws", "src/ice", "src/qos", {public = true})
-
-target("transport")
-    set_kind("object")
-    add_deps("log", "ws", "ice", "channel", "rtp", "rtcp", "statistics", "media")
-    add_files("src/transport/*.cpp")
-    add_includedirs("src/ws", "src/ice", "src/channel", {public = true})
-
-target("channel")
-    set_kind("object")
-    add_deps("log", "rtp", "rtcp", "ice")
-    add_files("src/channel/*.cpp")
-    add_includedirs("src/rtp", "src/rtcp", {public = true})
-
 target("pc")
     set_kind("object")
     add_deps("log", "ws", "ice", "transport", "inih", "common")
     add_files("src/pc/*.cpp")
-    add_includedirs("src/transport", "src/interface", {public = true})
+    add_includedirs("src/pc", "src/interface", {public = true})
 
 target("projectx")
     set_kind("static")
     add_deps("log", "pc")
     add_files("src/rtc/*.cpp")
-    add_includedirs("src/rtc", "src/pc", "src/interface")
+    add_includedirs("src/rtc", "src/interface")
 
     if is_os("windows") then
         add_linkdirs("thirdparty/nvcodec/lib/x64")