diff --git a/src/qos/prioritized_packet_queue.cc b/src/qos/prioritized_packet_queue.cc
index 18b2cfa..e7abfb5 100644
--- a/src/qos/prioritized_packet_queue.cc
+++ b/src/qos/prioritized_packet_queue.cc
@@ -100,9 +100,14 @@ PrioritizedPacketQueue::QueuedPacket
 PrioritizedPacketQueue::StreamQueue::DequeuePacket(int priority_level) {
   QueuedPacket packet = std::move(packets_[priority_level].front());
   packets_[priority_level].pop_front();
-  if (packet.packet->is_key_frame()) {
-    --num_keyframe_packets_;
+  if (!packet.packet) {
+    LOG_WARN("Packet is null");
+  } else {
+    if (packet.packet->is_key_frame()) {
+      --num_keyframe_packets_;
+    }
   }
+
   return packet;
 }
 
@@ -368,6 +373,12 @@ bool PrioritizedPacketQueue::HasKeyframePackets(uint32_t ssrc) const {
 
 void PrioritizedPacketQueue::DequeuePacketInternal(QueuedPacket& packet) {
   --size_packets_;
+
+  if (!packet.packet) {
+    LOG_WARN("Packet is null");
+    return;
+  }
+
   RtpPacketMediaType packet_type = packet.packet->packet_type().value();
   --size_packets_per_media_type_[static_cast<size_t>(packet_type)];
   size_payload_ -= packet.PacketSize();
diff --git a/src/rtp/rtp_packet/rtp_packet_history.cpp b/src/rtp/rtp_packet/rtp_packet_history.cpp
index df48ae4..b355943 100644
--- a/src/rtp/rtp_packet/rtp_packet_history.cpp
+++ b/src/rtp/rtp_packet/rtp_packet_history.cpp
@@ -3,10 +3,28 @@
 #include "log.h"
 #include "sequence_number_compare.h"
 
-RtpPacketHistory::RtpPacketHistory(std::shared_ptr<webrtc::Clock> clock)
-    : clock_(clock),
+RtpPacketHistory::StoredPacket::StoredPacket(
+    std::unique_ptr<webrtc::RtpPacketToSend> packet,
+    webrtc::Timestamp send_time, uint64_t insert_order)
+    : packet_(std::move(packet)),
+      pending_transmission_(false),
+      send_time_(send_time),
+      insert_order_(insert_order),
+      times_retransmitted_(0) {}
+
+RtpPacketHistory::StoredPacket::StoredPacket(StoredPacket&&) = default;
+RtpPacketHistory::StoredPacket& RtpPacketHistory::StoredPacket::operator=(
+    RtpPacketHistory::StoredPacket&&) = default;
+RtpPacketHistory::StoredPacket::~StoredPacket() = default;
+
+void RtpPacketHistory::StoredPacket::IncrementTimesRetransmitted() {
+  ++times_retransmitted_;
+}
+
+RtpPacketHistory::RtpPacketHistory(std::shared_ptr<SystemClock> clock)
+    : clock_(webrtc::Clock::GetWebrtcClockShared(clock)),
       rtt_(webrtc::TimeDelta::MinusInfinity()),
-      number_to_store_(0),
+      number_to_store_(kMaxCapacity),
       packets_inserted_(0) {}
 
 RtpPacketHistory::~RtpPacketHistory() {}
@@ -16,15 +34,14 @@ void RtpPacketHistory::SetRtt(webrtc::TimeDelta rtt) {
   RemoveDeadPackets();
 }
 
-void RtpPacketHistory::AddPacket(
-    std::unique_ptr<webrtc::RtpPacketToSend> rtp_packet,
-    webrtc::Timestamp send_time) {
+void RtpPacketHistory::PutRtpPacket(
+    std::unique_ptr<webrtc::RtpPacketToSend> rtp_packet, int64_t send_time) {
   RemoveDeadPackets();
   const uint16_t rtp_seq_no = rtp_packet->SequenceNumber();
   int packet_index = GetPacketIndex(rtp_packet->SequenceNumber());
   if (packet_index >= 0 &&
-      static_cast<size_t>(packet_index) < rtp_packet_history_.size() &&
-      rtp_packet_history_[packet_index].rtp_packet != nullptr) {
+      static_cast<size_t>(packet_index) < packet_history_.size() &&
+      packet_history_[packet_index].packet_ != nullptr) {
     LOG_WARN("Duplicate packet inserted: {}", rtp_seq_no);
     // Remove previous packet to avoid inconsistent state.
     RemovePacket(packet_index);
@@ -33,15 +50,16 @@ void RtpPacketHistory::AddPacket(
 
   // Packet to be inserted ahead of first packet, expand front.
   for (; packet_index < 0; ++packet_index) {
-    rtp_packet_history_.emplace_front();
+    packet_history_.emplace_front();
   }
   // Packet to be inserted behind last packet, expand back.
-  while (static_cast<int>(rtp_packet_history_.size()) <= packet_index) {
-    rtp_packet_history_.emplace_back();
+  while (static_cast<int>(packet_history_.size()) <= packet_index) {
+    packet_history_.emplace_back();
   }
 
-  rtp_packet_history_[packet_index] = {std::move(rtp_packet), send_time,
-                                       packets_inserted_++};
+  packet_history_[packet_index] = {std::move(rtp_packet),
+                                   webrtc::Timestamp::Micros(send_time),
+                                   packets_inserted_++};
 }
 
 void RtpPacketHistory::RemoveDeadPackets() {
@@ -50,23 +68,27 @@ void RtpPacketHistory::RemoveDeadPackets() {
       rtt_.IsFinite()
           ? (std::max)(kMinPacketDurationRtt * rtt_, kMinPacketDuration)
           : kMinPacketDuration;
-  while (!rtp_packet_history_.empty()) {
-    if (rtp_packet_history_.size() >= kMaxCapacity) {
+  while (!packet_history_.empty()) {
+    if (packet_history_.size() >= kMaxCapacity) {
       // We have reached the absolute max capacity, remove one packet
       // unconditionally.
       RemovePacket(0);
       continue;
     }
 
-    const RtpPacketToSendInfo& stored_packet = rtp_packet_history_.front();
+    const StoredPacket& stored_packet = packet_history_.front();
+    if (stored_packet.pending_transmission_) {
+      // Don't remove packets in the pacer queue, pending tranmission.
+      return;
+    }
 
-    if (stored_packet.send_time + packet_duration > now) {
+    if (stored_packet.send_time() + packet_duration > now) {
       // Don't cull packets too early to avoid failed retransmission requests.
       return;
     }
 
-    if (rtp_packet_history_.size() >= number_to_store_ ||
-        stored_packet.send_time +
+    if (packet_history_.size() >= number_to_store_ ||
+        stored_packet.send_time() +
                 (packet_duration * kPacketCullingDelayFactor) <=
             now) {
       // Too many packets in history, or this packet has timed out. Remove it
@@ -79,15 +101,80 @@ void RtpPacketHistory::RemoveDeadPackets() {
   }
 }
 
+std::unique_ptr<webrtc::RtpPacketToSend>
+RtpPacketHistory::GetPacketAndMarkAsPending(uint16_t sequence_number) {
+  return GetPacketAndMarkAsPending(
+      sequence_number, [](const webrtc::RtpPacketToSend& packet) {
+        return std::make_unique<webrtc::RtpPacketToSend>(packet);
+      });
+}
+
+std::unique_ptr<webrtc::RtpPacketToSend>
+RtpPacketHistory::GetPacketAndMarkAsPending(
+    uint16_t sequence_number,
+    std::function<std::unique_ptr<webrtc::RtpPacketToSend>(
+        const webrtc::RtpPacketToSend&)>
+        encapsulate) {
+  StoredPacket* packet = GetStoredPacket(sequence_number);
+  if (packet == nullptr) {
+    return nullptr;
+  }
+
+  if (packet->pending_transmission_) {
+    // Packet already in pacer queue, ignore this request.
+    return nullptr;
+  }
+
+  if (!VerifyRtt(*packet)) {
+    // Packet already resent within too short a time window, ignore.
+    return nullptr;
+  }
+
+  // Copy and/or encapsulate packet.
+  std::unique_ptr<webrtc::RtpPacketToSend> encapsulated_packet =
+      encapsulate(*packet->packet_);
+  if (encapsulated_packet) {
+    packet->pending_transmission_ = true;
+  }
+
+  return encapsulated_packet;
+}
+
+void RtpPacketHistory::MarkPacketAsSent(uint16_t sequence_number) {
+  StoredPacket* packet = GetStoredPacket(sequence_number);
+  if (packet == nullptr) {
+    return;
+  }
+
+  // Update send-time, mark as no longer in pacer queue, and increment
+  // transmission count.
+  packet->set_send_time(clock_->CurrentTime());
+  packet->pending_transmission_ = false;
+  packet->IncrementTimesRetransmitted();
+}
+
+bool RtpPacketHistory::VerifyRtt(
+    const RtpPacketHistory::StoredPacket& packet) const {
+  if (packet.times_retransmitted() > 0 &&
+      clock_->CurrentTime() - packet.send_time() < rtt_) {
+    // This packet has already been retransmitted once, and the time since
+    // that even is lower than on RTT. Ignore request as this packet is
+    // likely already in the network pipe.
+    return false;
+  }
+
+  return true;
+}
+
 std::unique_ptr<webrtc::RtpPacketToSend> RtpPacketHistory::RemovePacket(
     int packet_index) {
   // Move the packet out from the StoredPacket container.
   std::unique_ptr<webrtc::RtpPacketToSend> rtp_packet =
-      std::move(rtp_packet_history_[packet_index].rtp_packet);
+      std::move(packet_history_[packet_index].packet_);
   if (packet_index == 0) {
-    while (!rtp_packet_history_.empty() &&
-           rtp_packet_history_.front().rtp_packet == nullptr) {
-      rtp_packet_history_.pop_front();
+    while (!packet_history_.empty() &&
+           packet_history_.front().packet_ == nullptr) {
+      packet_history_.pop_front();
     }
   }
 
@@ -95,11 +182,11 @@ std::unique_ptr<webrtc::RtpPacketToSend> RtpPacketHistory::RemovePacket(
 }
 
 int RtpPacketHistory::GetPacketIndex(uint16_t sequence_number) const {
-  if (rtp_packet_history_.empty()) {
+  if (packet_history_.empty()) {
     return 0;
   }
 
-  int first_seq = rtp_packet_history_.front().rtp_packet->SequenceNumber();
+  int first_seq = packet_history_.front().packet_->SequenceNumber();
   if (first_seq == sequence_number) {
     return 0;
   }
@@ -118,4 +205,14 @@ int RtpPacketHistory::GetPacketIndex(uint16_t sequence_number) const {
   }
 
   return packet_index;
+}
+
+RtpPacketHistory::StoredPacket* RtpPacketHistory::GetStoredPacket(
+    uint16_t sequence_number) {
+  int index = GetPacketIndex(sequence_number);
+  if (index < 0 || static_cast<size_t>(index) >= packet_history_.size() ||
+      packet_history_[index].packet_ == nullptr) {
+    return nullptr;
+  }
+  return &packet_history_[index];
 }
\ No newline at end of file
diff --git a/src/rtp/rtp_packet/rtp_packet_history.h b/src/rtp/rtp_packet/rtp_packet_history.h
index 9537693..578ce8c 100644
--- a/src/rtp/rtp_packet/rtp_packet_history.h
+++ b/src/rtp/rtp_packet/rtp_packet_history.h
@@ -11,6 +11,7 @@
 #include <memory>
 
 #include "api/clock/clock.h"
+#include "clock/system_clock.h"
 #include "rtp_packet_to_send.h"
 
 class RtpPacketHistory {
@@ -26,39 +27,70 @@ class RtpPacketHistory {
   static constexpr int kPacketCullingDelayFactor = 3;
 
  public:
-  RtpPacketHistory(std::shared_ptr<webrtc::Clock> clock);
+  RtpPacketHistory(std::shared_ptr<SystemClock> clock);
   ~RtpPacketHistory();
 
  public:
   void SetRtt(webrtc::TimeDelta rtt);
-  void AddPacket(std::unique_ptr<webrtc::RtpPacketToSend> rtp_packet,
-                 webrtc::Timestamp send_time);
-  void RemoveDeadPackets();
+  void PutRtpPacket(std::unique_ptr<webrtc::RtpPacketToSend> rtp_packet,
+                    int64_t send_time);
+  void MarkPacketAsSent(uint16_t sequence_number);
+
+  std::unique_ptr<webrtc::RtpPacketToSend> GetPacketAndMarkAsPending(
+      uint16_t sequence_number);
+
+  std::unique_ptr<webrtc::RtpPacketToSend> GetPacketAndMarkAsPending(
+      uint16_t sequence_number,
+      std::function<std::unique_ptr<webrtc::RtpPacketToSend>(
+          const webrtc::RtpPacketToSend&)>
+          encapsulate);
 
  private:
   std::unique_ptr<webrtc::RtpPacketToSend> RemovePacket(int packet_index);
   int GetPacketIndex(uint16_t sequence_number) const;
 
  private:
-  struct RtpPacketToSendInfo {
-    RtpPacketToSendInfo() = default;
-    RtpPacketToSendInfo(std::unique_ptr<webrtc::RtpPacketToSend> rtp_packet,
-                        webrtc::Timestamp send_time, uint64_t index)
-        : rtp_packet(std::move(rtp_packet)),
-          send_time(send_time),
-          index(index) {}
-    RtpPacketToSendInfo(RtpPacketToSendInfo&&) = default;
-    RtpPacketToSendInfo& operator=(RtpPacketToSendInfo&&) = default;
-    ~RtpPacketToSendInfo() = default;
+  class StoredPacket {
+   public:
+    StoredPacket() = default;
+    StoredPacket(std::unique_ptr<webrtc::RtpPacketToSend> packet,
+                 webrtc::Timestamp send_time, uint64_t insert_order);
+    StoredPacket(StoredPacket&&);
+    StoredPacket& operator=(StoredPacket&&);
+    ~StoredPacket();
 
-    std::unique_ptr<webrtc::RtpPacketToSend> rtp_packet;
-    webrtc::Timestamp send_time = webrtc::Timestamp::Zero();
-    uint64_t index;
+    uint64_t insert_order() const { return insert_order_; }
+    size_t times_retransmitted() const { return times_retransmitted_; }
+    void IncrementTimesRetransmitted();
+
+    // The time of last transmission, including retransmissions.
+    webrtc::Timestamp send_time() const { return send_time_; }
+    void set_send_time(webrtc::Timestamp value) { send_time_ = value; }
+
+    // The actual packet.
+    std::unique_ptr<webrtc::RtpPacketToSend> packet_;
+
+    // True if the packet is currently in the pacer queue pending transmission.
+    bool pending_transmission_;
+
+   private:
+    webrtc::Timestamp send_time_ = webrtc::Timestamp::Zero();
+
+    // Unique number per StoredPacket, incremented by one for each added
+    // packet. Used to sort on insert order.
+    uint64_t insert_order_;
+
+    // Number of times RE-transmitted, ie excluding the first transmission.
+    size_t times_retransmitted_;
   };
 
+  void RemoveDeadPackets();
+  bool VerifyRtt(const StoredPacket& packet) const;
+  StoredPacket* GetStoredPacket(uint16_t sequence_number);
+
  private:
   std::shared_ptr<webrtc::Clock> clock_;
-  std::deque<RtpPacketToSendInfo> rtp_packet_history_;
+  std::deque<StoredPacket> packet_history_;
   uint64_t packets_inserted_;
   webrtc::TimeDelta rtt_;
   size_t number_to_store_;
diff --git a/src/transport/channel/rtp_video_receiver.cpp b/src/transport/channel/rtp_video_receiver.cpp
index 6a683d4..0d6f0b2 100644
--- a/src/transport/channel/rtp_video_receiver.cpp
+++ b/src/transport/channel/rtp_video_receiver.cpp
@@ -11,6 +11,7 @@
 
 #define NV12_BUFFER_SIZE (1280 * 720 * 3 / 2)
 #define RTCP_RR_INTERVAL 1000
+#define MAX_WAIT_TIME_MS 20  // 20ms
 
 RtpVideoReceiver::RtpVideoReceiver(std::shared_ptr<SystemClock> clock)
     : ssrc_(GenerateUniqueSsrc()),
@@ -231,8 +232,23 @@ void RtpVideoReceiver::ProcessH264RtpPacket(RtpPacketH264& rtp_packet_h264) {
       } else if (rtp::NAL_UNIT_TYPE::FU_A == nalu_type) {
         incomplete_h264_frame_list_[rtp_packet_h264.SequenceNumber()] =
             rtp_packet_h264;
-        bool complete = CheckIsH264FrameCompleted(rtp_packet_h264);
-        if (!complete) {
+        if (incomplete_h264_frame_list_.find(
+                rtp_packet_h264.SequenceNumber()) ==
+            incomplete_h264_frame_list_.end()) {
+          LOG_ERROR("missing seq {}", rtp_packet_h264.SequenceNumber());
+        }
+        if (rtp_packet_h264.FuAEnd()) {
+          CheckIsH264FrameCompletedFuaEndReceived(rtp_packet_h264);
+        } else {
+          auto missing_seqs_iter =
+              missing_sequence_numbers_.find(rtp_packet_h264.Timestamp());
+          if (missing_seqs_iter != missing_sequence_numbers_.end()) {
+            auto missing_seqs = missing_seqs_iter->second;
+            if (missing_seqs.find(rtp_packet_h264.SequenceNumber()) !=
+                missing_seqs.end()) {
+              CheckIsH264FrameCompletedMissSeqReceived(rtp_packet_h264);
+            }
+          }
         }
       }
     } else if (rtp::PAYLOAD_TYPE::H264 - 1 == rtp_packet_h264.PayloadType()) {
@@ -366,78 +382,181 @@ void RtpVideoReceiver::ProcessAv1RtpPacket(RtpPacketAv1& rtp_packet_av1) {
   // }
 }
 
-bool RtpVideoReceiver::CheckIsH264FrameCompleted(
+bool RtpVideoReceiver::CheckIsH264FrameCompletedFuaEndReceived(
     RtpPacketH264& rtp_packet_h264) {
-  if (rtp_packet_h264.FuAEnd()) {
-    uint16_t end_seq = rtp_packet_h264.SequenceNumber();
-    while (end_seq--) {
-      auto it = incomplete_h264_frame_list_.find(end_seq);
-      if (it == incomplete_h264_frame_list_.end()) {
-        if (padding_sequence_numbers_.find(end_seq) ==
-            padding_sequence_numbers_.end()) {
-          return false;
-        } else {
-          continue;
-        }
-      } else if (!it->second.FuAStart()) {
-        continue;
-      } else if (it->second.FuAStart()) {
-        if (!nv12_data_) {
-          nv12_data_ = new uint8_t[NV12_BUFFER_SIZE];
-        }
+  uint64_t timestamp = rtp_packet_h264.Timestamp();
+  uint16_t end_seq = rtp_packet_h264.SequenceNumber();
+  fua_end_sequence_numbers_[timestamp] = end_seq;
+  uint16_t start_seq = 0;
+  bool has_start = false;
+  bool has_missing = false;
+  missing_sequence_numbers_wait_time_[timestamp] = clock_->CurrentTime().ms();
 
-        size_t complete_frame_size = 0;
-        int frame_fragment_count = 0;
-        uint16_t start = it->first;
-        uint16_t end = rtp_packet_h264.SequenceNumber();
-        for (uint16_t seq = start; seq <= end; seq++) {
-          if (padding_sequence_numbers_.find(seq) ==
-              padding_sequence_numbers_.end()) {
-            complete_frame_size +=
-                incomplete_h264_frame_list_[seq].PayloadSize();
-          } else {
-            padding_sequence_numbers_.erase(seq);
-          }
-        }
+  for (uint16_t seq = end_seq; seq > 0; --seq) {
+    auto it = incomplete_h264_frame_list_.find(seq);
+    if (it == incomplete_h264_frame_list_.end()) {
+      if (padding_sequence_numbers_.find(seq) ==
+          padding_sequence_numbers_.end()) {
+        missing_sequence_numbers_[timestamp].insert(seq);
+        LOG_WARN("missing {}", seq);
+      }
+    } else if (it->second.FuAStart()) {
+      start_seq = seq;
+      has_start = true;
+      break;
+    }
+  }
 
-        if (!nv12_data_) {
-          nv12_data_ = new uint8_t[NV12_BUFFER_SIZE];
-        } else if (complete_frame_size > NV12_BUFFER_SIZE) {
-          delete[] nv12_data_;
-          nv12_data_ = new uint8_t[complete_frame_size];
-        }
+  if (!has_start) {
+    return false;
+  }
 
-        uint8_t* dest = nv12_data_;
-        for (uint16_t seq = start; seq <= end; seq++) {
-          size_t payload_size = incomplete_h264_frame_list_[seq].PayloadSize();
-          if (payload_size) {
-            memcpy(dest, incomplete_h264_frame_list_[seq].Payload(),
-                   payload_size);
-          }
-          dest += payload_size;
-          incomplete_h264_frame_list_.erase(seq);
-          frame_fragment_count++;
-        }
+  if (missing_sequence_numbers_.find(timestamp) !=
+      missing_sequence_numbers_.end()) {
+    if (!missing_sequence_numbers_[timestamp].empty()) {
+      return false;
+    }
+  }
 
-        ReceivedFrame received_frame(nv12_data_, complete_frame_size);
-        received_frame.SetReceivedTimestamp(clock_->CurrentTime().us());
-        received_frame.SetCapturedTimestamp(
-            (static_cast<int64_t>(rtp_packet_h264.Timestamp()) /
-                 rtp::kMsToRtpTimestamp -
-             delta_ntp_internal_ms_) *
-            1000);
-        compelete_video_frame_queue_.push(received_frame);
+  size_t complete_frame_size = 0;
+  int frame_fragment_count = 0;
 
-        return true;
-      } else {
-        LOG_WARN("What happened?");
+  for (uint16_t seq = start_seq; seq <= end_seq; ++seq) {
+    if (padding_sequence_numbers_.find(seq) !=
+        padding_sequence_numbers_.end()) {
+      padding_sequence_numbers_.erase(seq);
+      continue;
+    }
+    if (incomplete_h264_frame_list_.find(seq) !=
+        incomplete_h264_frame_list_.end()) {
+      complete_frame_size += incomplete_h264_frame_list_[seq].PayloadSize();
+    }
+  }
+
+  if (!nv12_data_) {
+    nv12_data_ = new uint8_t[NV12_BUFFER_SIZE];
+  } else if (complete_frame_size > NV12_BUFFER_SIZE) {
+    delete[] nv12_data_;
+    nv12_data_ = new uint8_t[complete_frame_size];
+  }
+
+  uint8_t* dest = nv12_data_;
+  for (uint16_t seq = start_seq; seq <= end_seq; ++seq) {
+    if (incomplete_h264_frame_list_.find(seq) !=
+        incomplete_h264_frame_list_.end()) {
+      size_t payload_size = incomplete_h264_frame_list_[seq].PayloadSize();
+      memcpy(dest, incomplete_h264_frame_list_[seq].Payload(), payload_size);
+      dest += payload_size;
+      incomplete_h264_frame_list_.erase(seq);
+      frame_fragment_count++;
+    }
+  }
+
+  ReceivedFrame received_frame(nv12_data_, complete_frame_size);
+  received_frame.SetReceivedTimestamp(clock_->CurrentTime().us());
+  received_frame.SetCapturedTimestamp(
+      (static_cast<int64_t>(timestamp) / rtp::kMsToRtpTimestamp -
+       delta_ntp_internal_ms_) *
+      1000);
+
+  fua_end_sequence_numbers_.erase(timestamp);
+  missing_sequence_numbers_wait_time_.erase(timestamp);
+  missing_sequence_numbers_.erase(timestamp);
+  compelete_video_frame_queue_.push(received_frame);
+
+  return true;
+}
+
+bool RtpVideoReceiver::CheckIsH264FrameCompletedMissSeqReceived(
+    RtpPacketH264& rtp_packet_h264) {
+  if (fua_end_sequence_numbers_.find(rtp_packet_h264.Timestamp()) ==
+      fua_end_sequence_numbers_.end()) {
+    return false;
+  }
+
+  uint64_t timestamp = rtp_packet_h264.Timestamp();
+  uint16_t end_seq = fua_end_sequence_numbers_[timestamp];
+  uint16_t start_seq = 0;
+  bool has_start = false;
+  bool has_missing = false;
+
+  for (uint16_t seq = end_seq; seq > 0; --seq) {
+    auto it = incomplete_h264_frame_list_.find(seq);
+    if (it == incomplete_h264_frame_list_.end()) {
+      if (padding_sequence_numbers_.find(seq) ==
+          padding_sequence_numbers_.end()) {
+        return false;
+      }
+    } else if (it->second.FuAStart()) {
+      start_seq = seq;
+      has_start = true;
+      break;
+    }
+  }
+
+  if (!has_start) {
+    return false;
+  }
+
+  if (missing_sequence_numbers_.find(timestamp) !=
+          missing_sequence_numbers_.end() &&
+      missing_sequence_numbers_wait_time_.find(timestamp) !=
+          missing_sequence_numbers_wait_time_.end()) {
+    if (!missing_sequence_numbers_[timestamp].empty()) {
+      int64_t wait_time = clock_->CurrentTime().us() -
+                          missing_sequence_numbers_wait_time_[timestamp];
+      if (wait_time < MAX_WAIT_TIME_MS) {
         return false;
       }
     }
-
-    return true;
   }
-  return false;
+
+  size_t complete_frame_size = 0;
+  int frame_fragment_count = 0;
+
+  for (uint16_t seq = start_seq; seq <= end_seq; ++seq) {
+    if (padding_sequence_numbers_.find(seq) !=
+        padding_sequence_numbers_.end()) {
+      padding_sequence_numbers_.erase(seq);
+      continue;
+    }
+    if (incomplete_h264_frame_list_.find(seq) !=
+        incomplete_h264_frame_list_.end()) {
+      complete_frame_size += incomplete_h264_frame_list_[seq].PayloadSize();
+    }
+  }
+
+  if (!nv12_data_) {
+    nv12_data_ = new uint8_t[NV12_BUFFER_SIZE];
+  } else if (complete_frame_size > NV12_BUFFER_SIZE) {
+    delete[] nv12_data_;
+    nv12_data_ = new uint8_t[complete_frame_size];
+  }
+
+  uint8_t* dest = nv12_data_;
+  for (uint16_t seq = start_seq; seq <= end_seq; ++seq) {
+    if (incomplete_h264_frame_list_.find(seq) !=
+        incomplete_h264_frame_list_.end()) {
+      size_t payload_size = incomplete_h264_frame_list_[seq].PayloadSize();
+      memcpy(dest, incomplete_h264_frame_list_[seq].Payload(), payload_size);
+      dest += payload_size;
+      incomplete_h264_frame_list_.erase(seq);
+      frame_fragment_count++;
+    }
+  }
+
+  ReceivedFrame received_frame(nv12_data_, complete_frame_size);
+  received_frame.SetReceivedTimestamp(clock_->CurrentTime().us());
+  received_frame.SetCapturedTimestamp(
+      (static_cast<int64_t>(timestamp) / rtp::kMsToRtpTimestamp -
+       delta_ntp_internal_ms_) *
+      1000);
+
+  missing_sequence_numbers_.erase(timestamp);
+  missing_sequence_numbers_wait_time_.erase(timestamp);
+  compelete_video_frame_queue_.push(received_frame);
+
+  return true;
 }
 
 bool RtpVideoReceiver::CheckIsAv1FrameCompleted(RtpPacketAv1& rtp_packet_av1) {
diff --git a/src/transport/channel/rtp_video_receiver.h b/src/transport/channel/rtp_video_receiver.h
index 394fdc5..ff2c954 100644
--- a/src/transport/channel/rtp_video_receiver.h
+++ b/src/transport/channel/rtp_video_receiver.h
@@ -5,6 +5,7 @@
 #include <map>
 #include <queue>
 #include <set>
+#include <unordered_map>
 #include <unordered_set>
 
 #include "api/clock/clock.h"
@@ -55,7 +56,8 @@ class RtpVideoReceiver : public ThreadBase,
 
  private:
   void ProcessH264RtpPacket(RtpPacketH264& rtp_packet_h264);
-  bool CheckIsH264FrameCompleted(RtpPacketH264& rtp_packet_h264);
+  bool CheckIsH264FrameCompletedFuaEndReceived(RtpPacketH264& rtp_packet_h264);
+  bool CheckIsH264FrameCompletedMissSeqReceived(RtpPacketH264& rtp_packet_h264);
 
  private:
   bool CheckIsTimeSendRR();
@@ -113,7 +115,11 @@ class RtpVideoReceiver : public ThreadBase,
   // std::map<uint32_t, std::map<uint16_t, RtpPacket>> fec_repair_symbol_list_;
   std::set<uint64_t> incomplete_fec_frame_list_;
   std::map<uint64_t, std::map<uint16_t, RtpPacket>> incomplete_fec_packet_list_;
-  std::unordered_set<int> padding_sequence_numbers_;
+  std::unordered_set<uint16_t> padding_sequence_numbers_;
+  std::unordered_map<uint64_t, std::unordered_set<uint16_t>>
+      missing_sequence_numbers_;
+  std::unordered_map<uint64_t, uint16_t> fua_end_sequence_numbers_;
+  std::unordered_map<uint64_t, int64_t> missing_sequence_numbers_wait_time_;
 
  private:
   std::thread rtcp_thread_;
diff --git a/src/transport/channel/rtp_video_sender.cpp b/src/transport/channel/rtp_video_sender.cpp
index f5c26f0..a766846 100644
--- a/src/transport/channel/rtp_video_sender.cpp
+++ b/src/transport/channel/rtp_video_sender.cpp
@@ -16,7 +16,6 @@ RtpVideoSender::RtpVideoSender(std::shared_ptr<SystemClock> clock,
                                std::shared_ptr<IOStatistics> io_statistics)
     : ssrc_(GenerateUniqueSsrc()),
       io_statistics_(io_statistics),
-      rtp_packet_history_(std::make_unique<RtpPacketHistory>(clock_)),
       clock_(webrtc::Clock::GetWebrtcClockShared(clock)) {
   SetPeriod(std::chrono::milliseconds(5));
 #ifdef SAVE_RTP_SENT_STREAM
@@ -130,8 +129,6 @@ int RtpVideoSender::SendRtpPacket(
 
   if (on_sent_packet_func_) {
     on_sent_packet_func_(*rtp_packet_to_send);
-    rtp_packet_history_->AddPacket(std::move(rtp_packet_to_send),
-                                   clock_->CurrentTime());
   }
 
   return 0;
diff --git a/src/transport/channel/rtp_video_sender.h b/src/transport/channel/rtp_video_sender.h
index e043ce0..847140c 100644
--- a/src/transport/channel/rtp_video_sender.h
+++ b/src/transport/channel/rtp_video_sender.h
@@ -9,7 +9,6 @@
 #include "receiver_report.h"
 #include "ringbuffer.h"
 #include "rtp_packet.h"
-#include "rtp_packet_history.h"
 #include "rtp_packet_to_send.h"
 #include "rtp_statistics.h"
 #include "sender_report.h"
@@ -62,7 +61,6 @@ class RtpVideoSender : public ThreadBase {
   std::shared_ptr<webrtc::Clock> clock_ = nullptr;
   std::unique_ptr<RtpStatistics> rtp_statistics_ = nullptr;
   std::shared_ptr<IOStatistics> io_statistics_ = nullptr;
-  std::unique_ptr<RtpPacketHistory> rtp_packet_history_ = nullptr;
   uint32_t last_send_bytes_ = 0;
   uint32_t last_send_rtcp_sr_packet_ts_ = 0;
   uint32_t total_rtp_payload_sent_ = 0;
diff --git a/src/transport/channel/video_channel_send.cpp b/src/transport/channel/video_channel_send.cpp
index 80ecffc..ef9cd5e 100644
--- a/src/transport/channel/video_channel_send.cpp
+++ b/src/transport/channel/video_channel_send.cpp
@@ -3,10 +3,6 @@
 #include "log.h"
 #include "rtc_base/network/sent_packet.h"
 
-VideoChannelSend::VideoChannelSend() {}
-
-VideoChannelSend::~VideoChannelSend() {}
-
 VideoChannelSend::VideoChannelSend(
     std::shared_ptr<SystemClock> clock, std::shared_ptr<IceAgent> ice_agent,
     std::shared_ptr<PacketSender> packet_sender,
@@ -19,8 +15,11 @@ VideoChannelSend::VideoChannelSend(
       on_sent_packet_func_(on_sent_packet_func),
       delta_ntp_internal_ms_(clock->CurrentNtpInMilliseconds() -
                              clock->CurrentTimeMs()),
+      rtp_packet_history_(clock),
       clock_(clock){};
 
+VideoChannelSend::~VideoChannelSend() {}
+
 void VideoChannelSend::Initialize(rtp::PAYLOAD_TYPE payload_type) {
   rtp_video_sender_ =
       std::make_unique<RtpVideoSender>(clock_, ice_io_statistics_);
@@ -58,6 +57,39 @@ void VideoChannelSend::SetEnqueuePacketsFunc(
   rtp_video_sender_->SetEnqueuePacketsFunc(enqueue_packets_func);
 }
 
+void VideoChannelSend::OnSentRtpPacket(
+    std::unique_ptr<webrtc::RtpPacketToSend> packet) {
+  if (packet->retransmitted_sequence_number()) {
+    rtp_packet_history_.MarkPacketAsSent(
+        *packet->retransmitted_sequence_number());
+  } else if (packet->PayloadType() != rtp::PAYLOAD_TYPE::H264 - 1) {
+    rtp_packet_history_.PutRtpPacket(std::move(packet), clock_->CurrentTime());
+  }
+}
+
+void VideoChannelSend::OnReceiveNack(
+    const std::vector<uint16_t>& nack_sequence_numbers) {
+  // int64_t rtt = rtt_ms();
+  // if (rtt == 0) {
+  //   if (std::optional<webrtc::TimeDelta> average_rtt =
+  //           rtcp_receiver_.AverageRtt()) {
+  //     rtt = average_rtt->ms();
+  //   }
+  // }
+
+  int64_t avg_rtt = 10;
+  rtp_packet_history_.SetRtt(TimeDelta::Millis(5 + avg_rtt));
+  for (uint16_t seq_no : nack_sequence_numbers) {
+    const int32_t bytes_sent = ReSendPacket(seq_no);
+    if (bytes_sent < 0) {
+      // Failed to send one Sequence number. Give up the rest in this nack.
+      LOG_WARN("Failed resending RTP packet {}, Discard rest of packets",
+               seq_no);
+      break;
+    }
+  }
+}
+
 std::vector<std::unique_ptr<RtpPacket>> VideoChannelSend::GeneratePadding(
     uint32_t payload_size, int64_t captured_timestamp_us) {
   if (rtp_packetizer_) {
@@ -87,3 +119,46 @@ int VideoChannelSend::SendVideo(std::shared_ptr<EncodedFrame> encoded_frame) {
 
   return 0;
 }
+
+int32_t VideoChannelSend::ReSendPacket(uint16_t packet_id) {
+  int32_t packet_size = 0;
+
+  std::unique_ptr<webrtc::RtpPacketToSend> packet =
+      rtp_packet_history_.GetPacketAndMarkAsPending(
+          packet_id, [&](const webrtc::RtpPacketToSend& stored_packet) {
+            // Check if we're overusing retransmission bitrate.
+            // TODO(sprang): Add histograms for nack success or failure
+            // reasons.
+            packet_size = stored_packet.size();
+            std::unique_ptr<webrtc::RtpPacketToSend> retransmit_packet;
+
+            retransmit_packet =
+                std::make_unique<webrtc::RtpPacketToSend>(stored_packet);
+
+            if (retransmit_packet) {
+              retransmit_packet->set_retransmitted_sequence_number(
+                  stored_packet.SequenceNumber());
+              retransmit_packet->set_original_ssrc(stored_packet.Ssrc());
+            }
+            return retransmit_packet;
+          });
+  if (packet_size == 0) {
+    // Packet not found or already queued for retransmission, ignore.
+    return 0;
+  }
+  if (!packet) {
+    // Packet was found, but lambda helper above chose not to create
+    // `retransmit_packet` out of it.
+    LOG_WARN("packet not found");
+    return -1;
+  }
+
+  packet->set_packet_type(webrtc::RtpPacketMediaType::kRetransmission);
+  packet->set_fec_protect_packet(false);
+  std::vector<std::unique_ptr<webrtc::RtpPacketToSend>> packets;
+  packets.emplace_back(std::move(packet));
+
+  packet_sender_->EnqueueRtpPacket(std::move(packets));
+
+  return packet_size;
+}
\ No newline at end of file
diff --git a/src/transport/channel/video_channel_send.h b/src/transport/channel/video_channel_send.h
index 5f035d3..d0f69dd 100644
--- a/src/transport/channel/video_channel_send.h
+++ b/src/transport/channel/video_channel_send.h
@@ -15,13 +15,13 @@
 #include "encoded_frame.h"
 #include "ice_agent.h"
 #include "packet_sender.h"
+#include "rtp_packet_history.h"
 #include "rtp_packetizer.h"
 #include "rtp_video_sender.h"
 #include "transport_feedback_adapter.h"
 
 class VideoChannelSend {
  public:
-  VideoChannelSend();
   VideoChannelSend(std::shared_ptr<SystemClock> clock,
                    std::shared_ptr<IceAgent> ice_agent,
                    std::shared_ptr<PacketSender> packet_sender,
@@ -35,15 +35,13 @@ class VideoChannelSend {
           void(std::vector<std::unique_ptr<webrtc::RtpPacketToSend>>&)>
           enqueue_packets_func);
 
+  void OnSentRtpPacket(std::unique_ptr<webrtc::RtpPacketToSend> packet);
+
+  void OnReceiveNack(const std::vector<uint16_t>& nack_sequence_numbers);
+
   std::vector<std::unique_ptr<RtpPacket>> GeneratePadding(
       uint32_t payload_size, int64_t captured_timestamp_us);
 
-  int64_t GetTransportSeqAndIncrement() {
-    int64_t transport_seq = rtp_video_sender_->GetTransportSequenceNumber();
-    rtp_video_sender_->IncrementTransportSequenceNumber();
-    return transport_seq;
-  }
-
  public:
   void Initialize(rtp::PAYLOAD_TYPE payload_type);
   void Destroy();
@@ -57,10 +55,6 @@ class VideoChannelSend {
 
   int SendVideo(std::shared_ptr<EncodedFrame> encoded_frame);
 
-  void OnCongestionControlFeedback(
-      Timestamp recv_ts,
-      const webrtc::rtcp::CongestionControlFeedback& feedback);
-
   void OnReceiverReport(const ReceiverReport& receiver_report) {
     if (rtp_video_sender_) {
       rtp_video_sender_->OnReceiverReport(receiver_report);
@@ -68,9 +62,7 @@ class VideoChannelSend {
   }
 
  private:
-  void PostUpdates(webrtc::NetworkControlUpdate update);
-  void UpdateControlState();
-  void UpdateCongestedState();
+  int32_t ReSendPacket(uint16_t packet_id);
 
  private:
   std::shared_ptr<PacketSender> packet_sender_ = nullptr;
@@ -84,6 +76,7 @@ class VideoChannelSend {
 
  private:
   std::shared_ptr<SystemClock> clock_;
+  RtpPacketHistory rtp_packet_history_;
   int64_t delta_ntp_internal_ms_;
 };
 
diff --git a/src/transport/ice_transport.cpp b/src/transport/ice_transport.cpp
index 18ac745..b40102d 100644
--- a/src/transport/ice_transport.cpp
+++ b/src/transport/ice_transport.cpp
@@ -399,20 +399,12 @@ bool IceTransport::HandleNack(const RtcpCommonHeader &rtcp_block,
     return false;
   }
 
-  // uint32_t first_media_source_ssrc = nack.ssrc();
-  // if (first_media_source_ssrc == local_media_ssrc() ||
-  //     registered_ssrcs_.contains(first_media_source_ssrc)) {
-  //   rtcp_packet_info->nack.emplace(std::move(nack));
-  // }
+  if (ice_transport_controller_) {
+    ice_transport_controller_->OnReceiveNack(nack.packet_ids());
+    return true;
+  }
 
-  // int64_t rtt = rtt_ms();
-  // if (rtt == 0) {
-  //   if (std::optional<TimeDelta> average_rtt = rtcp_receiver_.AverageRtt()) {
-  //     rtt = average_rtt->ms();
-  //   }
-  // }
-
-  return true;
+  return false;
 }
 
 bool IceTransport::HandleFir(const RtcpCommonHeader &rtcp_block,
diff --git a/src/transport/ice_transport_controller.cpp b/src/transport/ice_transport_controller.cpp
index e0fe46d..c2cc7dc 100644
--- a/src/transport/ice_transport_controller.cpp
+++ b/src/transport/ice_transport_controller.cpp
@@ -10,16 +10,16 @@
 
 IceTransportController::IceTransportController(
     std::shared_ptr<SystemClock> clock)
-    : last_report_block_time_(
+    : clock_(clock),
+      webrtc_clock_(webrtc::Clock::GetWebrtcClockShared(clock)),
+      last_report_block_time_(
           webrtc::Timestamp::Millis(webrtc_clock_->TimeInMilliseconds())),
       b_force_i_frame_(true),
       video_codec_inited_(false),
       audio_codec_inited_(false),
       load_nvcodec_dll_success_(false),
       hardware_acceleration_(false),
-      congestion_window_size_(DataSize::PlusInfinity()),
-      clock_(clock),
-      webrtc_clock_(webrtc::Clock::GetWebrtcClockShared(clock)) {
+      congestion_window_size_(DataSize::PlusInfinity()) {
   SetPeriod(std::chrono::milliseconds(25));
 }
 
@@ -60,10 +60,25 @@ void IceTransportController::Create(
   packet_sender_->SetSendBurstInterval(TimeDelta::Millis(40));
   packet_sender_->SetQueueTimeLimit(TimeDelta::Millis(2000));
   packet_sender_->SetOnSentPacketFunc(
-      [this](const webrtc::RtpPacketToSend& packet) {
+      [this](std::unique_ptr<webrtc::RtpPacketToSend> packet) {
         if (ice_agent_) {
-          ice_agent_->Send((const char*)packet.Buffer().data(), packet.Size());
-          OnSentRtpPacket(packet);
+          webrtc::Timestamp now = webrtc_clock_->CurrentTime();
+          ice_agent_->Send((const char*)packet->Buffer().data(),
+                           packet->Size());
+          OnSentRtpPacket(*packet);
+
+          if (packet->packet_type().has_value()) {
+            switch (packet->packet_type().value()) {
+              case webrtc::RtpPacketMediaType::kVideo:
+              case webrtc::RtpPacketMediaType::kRetransmission:
+                if (video_channel_send_) {
+                  video_channel_send_->OnSentRtpPacket(std::move(packet));
+                }
+                break;
+              default:
+                break;
+            }
+          }
         }
       });
 
@@ -448,12 +463,13 @@ void IceTransportController::OnReceiverReport(
         report_block.ExtendedHighSeqNum();
     last_loss_report.cumulative_lost = report_block.CumulativeLost();
   }
-  // Can only compute delta if there has been previous blocks to compare to. If
-  // not, total_packets_delta will be unchanged and there's nothing more to do.
+  // Can only compute delta if there has been previous blocks to compare to.
+  // If not, total_packets_delta will be unchanged and there's nothing more to
+  // do.
   if (!total_packets_delta) return;
   int packets_received_delta = total_packets_delta - total_packets_lost_delta;
-  // To detect lost packets, at least one packet has to be received. This check
-  // is needed to avoid bandwith detection update in
+  // To detect lost packets, at least one packet has to be received. This
+  // check is needed to avoid bandwith detection update in
   // VideoSendStreamTest.SuspendBelowMinBitrate
 
   if (packets_received_delta < 1) {
@@ -489,6 +505,13 @@ void IceTransportController::HandleTransportPacketsFeedback(
   UpdateCongestedState();
 }
 
+void IceTransportController::OnReceiveNack(
+    const std::vector<uint16_t>& nack_sequence_numbers) {
+  if (video_channel_send_) {
+    video_channel_send_->OnReceiveNack(nack_sequence_numbers);
+  }
+}
+
 void IceTransportController::UpdateControllerWithTimeInterval() {
   ProcessInterval msg;
   msg.at_time = Timestamp::Millis(webrtc_clock_->TimeInMilliseconds());
diff --git a/src/transport/ice_transport_controller.h b/src/transport/ice_transport_controller.h
index ed18011..a482f22 100644
--- a/src/transport/ice_transport_controller.h
+++ b/src/transport/ice_transport_controller.h
@@ -74,6 +74,7 @@ class IceTransportController
   void OnReceiverReport(const std::vector<RtcpReportBlock> &report_block_datas);
   void OnCongestionControlFeedback(
       const webrtc::rtcp::CongestionControlFeedback &feedback);
+  void OnReceiveNack(const std::vector<uint16_t> &nack_sequence_numbers);
 
  private:
   int CreateVideoCodec(std::shared_ptr<SystemClock> clock,
diff --git a/src/transport/packet_sender/packet_sender.h b/src/transport/packet_sender/packet_sender.h
index d5f4442..a780971 100644
--- a/src/transport/packet_sender/packet_sender.h
+++ b/src/transport/packet_sender/packet_sender.h
@@ -11,6 +11,7 @@
 #include <vector>
 
 #include "rtp_packet.h"
+#include "rtp_packet_to_send.h"
 
 class PacketSender {
  public:
@@ -19,8 +20,12 @@ class PacketSender {
 
   virtual int Send() = 0;
   virtual int EnqueueRtpPacket(
-      std::vector<std::unique_ptr<RtpPacket>> &rtp_packets,
+      std::vector<std::unique_ptr<RtpPacket>>& rtp_packets,
       int64_t captured_timestamp_us) = 0;
+
+  virtual int EnqueueRtpPacket(
+      std::vector<std::unique_ptr<webrtc::RtpPacketToSend>>& rtp_packets) = 0;
+  ;
 };
 
 #endif
\ No newline at end of file
diff --git a/src/transport/packet_sender/packet_sender_imp.cpp b/src/transport/packet_sender/packet_sender_imp.cpp
index ae42ba3..e376b9f 100644
--- a/src/transport/packet_sender/packet_sender_imp.cpp
+++ b/src/transport/packet_sender/packet_sender_imp.cpp
@@ -290,4 +290,10 @@ int PacketSenderImp::EnqueueRtpPacket(
 
   EnqueuePackets(std::move(to_send_rtp_packets));
   return 0;
+}
+
+int PacketSenderImp::EnqueueRtpPacket(
+    std::vector<std::unique_ptr<webrtc::RtpPacketToSend>> &rtp_packets) {
+  EnqueuePackets(std::move(rtp_packets));
+  return 0;
 }
\ No newline at end of file
diff --git a/src/transport/packet_sender/packet_sender_imp.h b/src/transport/packet_sender/packet_sender_imp.h
index 05564fd..a6d6bf6 100644
--- a/src/transport/packet_sender/packet_sender_imp.h
+++ b/src/transport/packet_sender/packet_sender_imp.h
@@ -35,13 +35,18 @@ class PacketSenderImp : public PacketSender,
   ~PacketSenderImp();
 
  public:
-  int Send() { return 0; }
+  int Send() override { return 0; }
 
   int EnqueueRtpPacket(std::vector<std::unique_ptr<RtpPacket>>& rtp_packets,
-                       int64_t captured_timestamp_us);
+                       int64_t captured_timestamp_us) override;
 
+  int EnqueueRtpPacket(std::vector<std::unique_ptr<webrtc::RtpPacketToSend>>&
+                           rtp_packets) override;
+
+ public:
   void SetOnSentPacketFunc(
-      std::function<void(const webrtc::RtpPacketToSend&)> on_sent_packet_func) {
+      std::function<void(std::unique_ptr<webrtc::RtpPacketToSend>)>
+          on_sent_packet_func) {
     on_sent_packet_func_ = on_sent_packet_func;
   }
 
@@ -59,8 +64,12 @@ class PacketSenderImp : public PacketSender,
         ssrc_seq_[packet->Ssrc()] = 1;
       }
 
-      packet->UpdateSequenceNumber(ssrc_seq_[packet->Ssrc()]++);
-      on_sent_packet_func_(*packet);
+      if (packet->packet_type() !=
+          webrtc::RtpPacketMediaType::kRetransmission) {
+        packet->UpdateSequenceNumber(ssrc_seq_[packet->Ssrc()]++);
+      }
+
+      on_sent_packet_func_(std::move(packet));
     }
   }
   // Should be called after each call to SendPacket().
@@ -176,8 +185,8 @@ class PacketSenderImp : public PacketSender,
  private:
   std::shared_ptr<IceAgent> ice_agent_ = nullptr;
   webrtc::PacingController pacing_controller_;
-  std::function<void(const webrtc::RtpPacketToSend&)> on_sent_packet_func_ =
-      nullptr;
+  std::function<void(std::unique_ptr<webrtc::RtpPacketToSend>)>
+      on_sent_packet_func_ = nullptr;
 
   std::function<std::vector<std::unique_ptr<RtpPacket>>(uint32_t, int64_t)>
       generat_padding_func_ = nullptr;