diff --git a/modules/rtp_rtcp/include/rtp_rtcp_defines.h b/modules/rtp_rtcp/include/rtp_rtcp_defines.h
index 7d54ea4..8add0a6 100644
--- a/modules/rtp_rtcp/include/rtp_rtcp_defines.h
+++ b/modules/rtp_rtcp/include/rtp_rtcp_defines.h
@@ -113,11 +113,16 @@
 
 enum RtpRtcpPacketType { kPacketRtp = 0, kPacketKeepAlive = 1 };
 
+// kConditionallyRetransmitHigherLayers allows retransmission of video frames
+// in higher layers if either the last frame in that layer was too far back in
+// time, or if we estimate that a new frame will be available in a lower layer
+// in a shorter time than it would take to request and receive a retransmission.
 enum RetransmissionMode : uint8_t {
   kRetransmitOff = 0x0,
   kRetransmitFECPackets = 0x1,
   kRetransmitBaseLayer = 0x2,
   kRetransmitHigherLayers = 0x4,
+  kConditionallyRetransmitHigherLayers = 0x8,
   kRetransmitAllPackets = 0xFF
 };
 
diff --git a/modules/rtp_rtcp/source/rtp_format.h b/modules/rtp_rtcp/source/rtp_format.h
index 378f38a..7b47921 100644
--- a/modules/rtp_rtcp/source/rtp_format.h
+++ b/modules/rtp_rtcp/source/rtp_format.h
@@ -41,10 +41,6 @@
   // Returns true on success, false otherwise.
   virtual bool NextPacket(RtpPacketToSend* packet) = 0;
 
-  virtual ProtectionType GetProtectionType() = 0;
-
-  virtual StorageType GetStorageType(uint32_t retransmission_settings) = 0;
-
   virtual std::string ToString() = 0;
 };
 
diff --git a/modules/rtp_rtcp/source/rtp_format_h264.cc b/modules/rtp_rtcp/source/rtp_format_h264.cc
index 092ac1c..5aa7e27 100644
--- a/modules/rtp_rtcp/source/rtp_format_h264.cc
+++ b/modules/rtp_rtcp/source/rtp_format_h264.cc
@@ -389,15 +389,6 @@
   packets_.pop();
 }
 
-ProtectionType RtpPacketizerH264::GetProtectionType() {
-  return kProtectedPacket;
-}
-
-StorageType RtpPacketizerH264::GetStorageType(
-    uint32_t retransmission_settings) {
-  return kAllowRetransmission;
-}
-
 std::string RtpPacketizerH264::ToString() {
   return "RtpPacketizerH264";
 }
diff --git a/modules/rtp_rtcp/source/rtp_format_h264.h b/modules/rtp_rtcp/source/rtp_format_h264.h
index 3742ec5..efa9b97 100644
--- a/modules/rtp_rtcp/source/rtp_format_h264.h
+++ b/modules/rtp_rtcp/source/rtp_format_h264.h
@@ -41,10 +41,6 @@
   // Returns true on success, false otherwise.
   bool NextPacket(RtpPacketToSend* rtp_packet) override;
 
-  ProtectionType GetProtectionType() override;
-
-  StorageType GetStorageType(uint32_t retransmission_settings) override;
-
   std::string ToString() override;
 
  private:
diff --git a/modules/rtp_rtcp/source/rtp_format_video_generic.cc b/modules/rtp_rtcp/source/rtp_format_video_generic.cc
index 696dc2b..ffb5f77 100644
--- a/modules/rtp_rtcp/source/rtp_format_video_generic.cc
+++ b/modules/rtp_rtcp/source/rtp_format_video_generic.cc
@@ -108,15 +108,6 @@
   return true;
 }
 
-ProtectionType RtpPacketizerGeneric::GetProtectionType() {
-  return kProtectedPacket;
-}
-
-StorageType RtpPacketizerGeneric::GetStorageType(
-    uint32_t retransmission_settings) {
-  return kAllowRetransmission;
-}
-
 std::string RtpPacketizerGeneric::ToString() {
   return "RtpPacketizerGeneric";
 }
diff --git a/modules/rtp_rtcp/source/rtp_format_video_generic.h b/modules/rtp_rtcp/source/rtp_format_video_generic.h
index 16d92e7..9fa3cce 100644
--- a/modules/rtp_rtcp/source/rtp_format_video_generic.h
+++ b/modules/rtp_rtcp/source/rtp_format_video_generic.h
@@ -43,10 +43,6 @@
   // Returns true on success, false otherwise.
   bool NextPacket(RtpPacketToSend* packet) override;
 
-  ProtectionType GetProtectionType() override;
-
-  StorageType GetStorageType(uint32_t retransmission_settings) override;
-
   std::string ToString() override;
 
  private:
diff --git a/modules/rtp_rtcp/source/rtp_format_vp8.cc b/modules/rtp_rtcp/source/rtp_format_vp8.cc
index b31de93..e56a977 100644
--- a/modules/rtp_rtcp/source/rtp_format_vp8.cc
+++ b/modules/rtp_rtcp/source/rtp_format_vp8.cc
@@ -211,25 +211,6 @@
   return true;
 }
 
-ProtectionType RtpPacketizerVp8::GetProtectionType() {
-  bool protect =
-      hdr_info_.temporalIdx == 0 || hdr_info_.temporalIdx == kNoTemporalIdx;
-  return protect ? kProtectedPacket : kUnprotectedPacket;
-}
-
-StorageType RtpPacketizerVp8::GetStorageType(uint32_t retransmission_settings) {
-  if (hdr_info_.temporalIdx == 0 &&
-      !(retransmission_settings & kRetransmitBaseLayer)) {
-    return kDontRetransmit;
-  }
-  if (hdr_info_.temporalIdx != kNoTemporalIdx &&
-             hdr_info_.temporalIdx > 0 &&
-             !(retransmission_settings & kRetransmitHigherLayers)) {
-    return kDontRetransmit;
-  }
-  return kAllowRetransmission;
-}
-
 std::string RtpPacketizerVp8::ToString() {
   return "RtpPacketizerVp8";
 }
diff --git a/modules/rtp_rtcp/source/rtp_format_vp8.h b/modules/rtp_rtcp/source/rtp_format_vp8.h
index edb3d4d..f8b7c2f 100644
--- a/modules/rtp_rtcp/source/rtp_format_vp8.h
+++ b/modules/rtp_rtcp/source/rtp_format_vp8.h
@@ -72,10 +72,6 @@
   // Returns true on success, false otherwise.
   bool NextPacket(RtpPacketToSend* packet) override;
 
-  ProtectionType GetProtectionType() override;
-
-  StorageType GetStorageType(uint32_t retransmission_settings) override;
-
   std::string ToString() override;
 
  private:
diff --git a/modules/rtp_rtcp/source/rtp_format_vp9.cc b/modules/rtp_rtcp/source/rtp_format_vp9.cc
index 6f02010..b08ec8b 100644
--- a/modules/rtp_rtcp/source/rtp_format_vp9.cc
+++ b/modules/rtp_rtcp/source/rtp_format_vp9.cc
@@ -472,24 +472,6 @@
 RtpPacketizerVp9::~RtpPacketizerVp9() {
 }
 
-ProtectionType RtpPacketizerVp9::GetProtectionType() {
-  bool protect =
-      hdr_.temporal_idx == 0 || hdr_.temporal_idx == kNoTemporalIdx;
-  return protect ? kProtectedPacket : kUnprotectedPacket;
-}
-
-StorageType RtpPacketizerVp9::GetStorageType(uint32_t retransmission_settings) {
-  StorageType storage = kAllowRetransmission;
-  if (hdr_.temporal_idx == 0 &&
-      !(retransmission_settings & kRetransmitBaseLayer)) {
-    storage = kDontRetransmit;
-  } else if (hdr_.temporal_idx != kNoTemporalIdx && hdr_.temporal_idx > 0 &&
-             !(retransmission_settings & kRetransmitHigherLayers)) {
-    storage = kDontRetransmit;
-  }
-  return storage;
-}
-
 std::string RtpPacketizerVp9::ToString() {
   return "RtpPacketizerVp9";
 }
diff --git a/modules/rtp_rtcp/source/rtp_format_vp9.h b/modules/rtp_rtcp/source/rtp_format_vp9.h
index 7b0b06c..cf911a3 100644
--- a/modules/rtp_rtcp/source/rtp_format_vp9.h
+++ b/modules/rtp_rtcp/source/rtp_format_vp9.h
@@ -39,10 +39,6 @@
 
   virtual ~RtpPacketizerVp9();
 
-  ProtectionType GetProtectionType() override;
-
-  StorageType GetStorageType(uint32_t retransmission_settings) override;
-
   std::string ToString() override;
 
   // The payload data must be one encoded VP9 layer frame.
diff --git a/modules/rtp_rtcp/source/rtp_format_vp9_unittest.cc b/modules/rtp_rtcp/source/rtp_format_vp9_unittest.cc
index 40d25d0..49ded07 100644
--- a/modules/rtp_rtcp/source/rtp_format_vp9_unittest.cc
+++ b/modules/rtp_rtcp/source/rtp_format_vp9_unittest.cc
@@ -580,37 +580,6 @@
   EXPECT_TRUE(packet.Marker());
 }
 
-TEST_F(RtpPacketizerVp9Test, TestBaseLayerProtectionAndStorageType) {
-  const size_t kFrameSize = 10;
-  const size_t kPacketSize = 12;
-
-  // I:0, P:0, L:1, F:1, B:1, E:1, V:0 (2hdr + 10 payload)
-  // L:   T:0, U:0, S:0, D:0
-  expected_.flexible_mode = true;
-  expected_.temporal_idx = 0;
-  Init(kFrameSize, kPacketSize);
-  EXPECT_EQ(kProtectedPacket, packetizer_->GetProtectionType());
-  EXPECT_EQ(kAllowRetransmission,
-            packetizer_->GetStorageType(kRetransmitBaseLayer));
-  EXPECT_EQ(kDontRetransmit, packetizer_->GetStorageType(kRetransmitOff));
-}
-
-TEST_F(RtpPacketizerVp9Test, TestHigherLayerProtectionAndStorageType) {
-  const size_t kFrameSize = 10;
-  const size_t kPacketSize = 12;
-
-  // I:0, P:0, L:1, F:1, B:1, E:1, V:0 (2hdr + 10 payload)
-  // L:   T:1, U:0, S:0, D:0
-  expected_.flexible_mode = true;
-  expected_.temporal_idx = 1;
-  Init(kFrameSize, kPacketSize);
-  EXPECT_EQ(kUnprotectedPacket, packetizer_->GetProtectionType());
-  EXPECT_EQ(kDontRetransmit, packetizer_->GetStorageType(kRetransmitBaseLayer));
-  EXPECT_EQ(kAllowRetransmission,
-            packetizer_->GetStorageType(kRetransmitHigherLayers));
-}
-
-
 class RtpDepacketizerVp9Test : public ::testing::Test {
  protected:
   RtpDepacketizerVp9Test()
diff --git a/modules/rtp_rtcp/source/rtp_rtcp_impl.cc b/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
index 31d1b0e..6167b44 100644
--- a/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
+++ b/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
@@ -31,6 +31,7 @@
 const int64_t kRtpRtcpMaxIdleTimeProcessMs = 5;
 const int64_t kRtpRtcpRttProcessTimeMs = 1000;
 const int64_t kRtpRtcpBitrateProcessTimeMs = 10;
+const int64_t kDefaultExpectedRetransmissionTimeMs = 125;
 }  // namespace
 
 RTPExtensionType StringToRtpExtensionType(const std::string& extension) {
@@ -430,9 +431,20 @@
   if (rtcp_sender_.TimeToSendRTCPReport(kVideoFrameKey == frame_type)) {
       rtcp_sender_.SendRTCP(GetFeedbackState(), kRtcpReport);
   }
+  int64_t expected_retransmission_time_ms = rtt_ms();
+  if (expected_retransmission_time_ms == 0) {
+    // 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) == -1) {
+      expected_retransmission_time_ms = kDefaultExpectedRetransmissionTimeMs;
+    }
+  }
   return rtp_sender_->SendOutgoingData(
       frame_type, payload_type, time_stamp, capture_time_ms, payload_data,
-      payload_size, fragmentation, rtp_video_header, transport_frame_id_out);
+      payload_size, fragmentation, rtp_video_header, transport_frame_id_out,
+      expected_retransmission_time_ms);
 }
 
 bool ModuleRtpRtcpImpl::TimeToSendPacket(uint32_t ssrc,
diff --git a/modules/rtp_rtcp/source/rtp_sender.cc b/modules/rtp_rtcp/source/rtp_sender.cc
index 89e7735..8608759 100644
--- a/modules/rtp_rtcp/source/rtp_sender.cc
+++ b/modules/rtp_rtcp/source/rtp_sender.cc
@@ -232,7 +232,7 @@
   if (payload_type_map_.end() != it) {
     // We already use this payload type.
     RtpUtility::Payload* payload = it->second;
-    assert(payload);
+    RTC_DCHECK(payload);
 
     // Check if it's the same as we already have.
     if (RtpUtility::StringCompare(
@@ -355,7 +355,7 @@
   }
   SetSendPayloadType(payload_type);
   RtpUtility::Payload* payload = it->second;
-  assert(payload);
+  RTC_DCHECK(payload);
   if (!payload->audio && !audio_configured_) {
     video_->SetVideoCodecType(payload->typeSpecific.Video.videoCodecType);
     *video_type = payload->typeSpecific.Video.videoCodecType;
@@ -371,7 +371,8 @@
                                  size_t payload_size,
                                  const RTPFragmentationHeader* fragmentation,
                                  const RTPVideoHeader* rtp_header,
-                                 uint32_t* transport_frame_id_out) {
+                                 uint32_t* transport_frame_id_out,
+                                 int64_t expected_retransmission_time_ms) {
   uint32_t ssrc;
   uint16_t sequence_number;
   uint32_t rtp_timestamp;
@@ -395,20 +396,29 @@
     return false;
   }
 
+  switch (frame_type) {
+    case kAudioFrameSpeech:
+    case kAudioFrameCN:
+      RTC_CHECK(audio_configured_);
+      break;
+    case kVideoFrameKey:
+    case kVideoFrameDelta:
+      RTC_CHECK(!audio_configured_);
+      break;
+    case kEmptyFrame:
+      break;
+  }
+
   bool result;
   if (audio_configured_) {
     TRACE_EVENT_ASYNC_STEP1("webrtc", "Audio", rtp_timestamp, "Send", "type",
                             FrameTypeToString(frame_type));
-    assert(frame_type == kAudioFrameSpeech || frame_type == kAudioFrameCN ||
-           frame_type == kEmptyFrame);
 
     result = audio_->SendAudio(frame_type, payload_type, rtp_timestamp,
                                payload_data, payload_size, fragmentation);
   } else {
     TRACE_EVENT_ASYNC_STEP1("webrtc", "Video", capture_time_ms,
                             "Send", "type", FrameTypeToString(frame_type));
-    assert(frame_type != kAudioFrameSpeech && frame_type != kAudioFrameCN);
-
     if (frame_type == kEmptyFrame)
       return true;
 
@@ -419,7 +429,8 @@
 
     result = video_->SendVideo(video_type, frame_type, payload_type,
                                rtp_timestamp, capture_time_ms, payload_data,
-                               payload_size, fragmentation, rtp_header);
+                               payload_size, fragmentation, rtp_header,
+                               expected_retransmission_time_ms);
   }
 
   rtc::CritScope cs(&statistics_crit_);
@@ -1105,7 +1116,7 @@
 }
 
 void RTPSender::SetCsrcs(const std::vector<uint32_t>& csrcs) {
-  assert(csrcs.size() <= kRtpCsrcSize);
+  RTC_DCHECK_LE(csrcs.size(), kRtpCsrcSize);
   rtc::CritScope lock(&send_critsect_);
   csrcs_ = csrcs;
 }
@@ -1136,7 +1147,7 @@
 }
 
 RtpVideoCodecTypes RTPSender::VideoCodecType() const {
-  assert(!audio_configured_ && "Sender is an audio stream!");
+  RTC_DCHECK(!audio_configured_) << "Sender is an audio stream!";
   return video_->VideoCodecType();
 }
 
diff --git a/modules/rtp_rtcp/source/rtp_sender.h b/modules/rtp_rtcp/source/rtp_sender.h
index 069357f..9c4fdc1 100644
--- a/modules/rtp_rtcp/source/rtp_sender.h
+++ b/modules/rtp_rtcp/source/rtp_sender.h
@@ -108,7 +108,8 @@
                         size_t payload_size,
                         const RTPFragmentationHeader* fragmentation,
                         const RTPVideoHeader* rtp_header,
-                        uint32_t* transport_frame_id_out);
+                        uint32_t* transport_frame_id_out,
+                        int64_t expected_retransmission_time_ms);
 
   // RTP header extension
   int32_t RegisterRtpHeaderExtension(RTPExtensionType type, uint8_t id);
diff --git a/modules/rtp_rtcp/source/rtp_sender_unittest.cc b/modules/rtp_rtcp/source/rtp_sender_unittest.cc
index 14bbff7..5a47759 100644
--- a/modules/rtp_rtcp/source/rtp_sender_unittest.cc
+++ b/modules/rtp_rtcp/source/rtp_sender_unittest.cc
@@ -25,7 +25,9 @@
 #include "webrtc/modules/rtp_rtcp/source/rtp_sender.h"
 #include "webrtc/modules/rtp_rtcp/source/rtp_sender_video.h"
 #include "webrtc/modules/rtp_rtcp/source/rtp_utility.h"
+#include "webrtc/rtc_base/arraysize.h"
 #include "webrtc/rtc_base/buffer.h"
+#include "webrtc/rtc_base/ptr_util.h"
 #include "webrtc/rtc_base/rate_limiter.h"
 #include "webrtc/test/field_trial.h"
 #include "webrtc/test/gmock.h"
@@ -55,6 +57,7 @@
 const int kVideoRotationExtensionId = 5;
 const size_t kGenericHeaderLength = 1;
 const uint8_t kPayloadData[] = {47, 11, 32, 93, 89};
+const int64_t kDefaultExpectedRetransmissionTimeMs = 125;
 
 using ::testing::_;
 using ::testing::ElementsAreArray;
@@ -238,7 +241,8 @@
 
     EXPECT_TRUE(rtp_sender_->SendOutgoingData(
         kVideoFrameKey, kPayloadType, kTimestamp, kCaptureTimeMs, kPayloadData,
-        sizeof(kPayloadData), nullptr, nullptr, nullptr));
+        sizeof(kPayloadData), nullptr, nullptr, nullptr,
+        kDefaultExpectedRetransmissionTimeMs));
   }
 };
 
@@ -249,15 +253,32 @@
   void SetUp() override { SetUpRtpSender(false); }
 };
 
+class TestRtpSenderVideo : public RTPSenderVideo {
+ public:
+  TestRtpSenderVideo(Clock* clock,
+                     RTPSender* rtp_sender,
+                     FlexfecSender* flexfec_sender)
+      : RTPSenderVideo(clock, rtp_sender, flexfec_sender) {}
+  ~TestRtpSenderVideo() override {}
+
+  StorageType GetStorageType(const RTPVideoHeader& header,
+                             int32_t retransmission_settings,
+                             int64_t expected_retransmission_time_ms) {
+    return RTPSenderVideo::GetStorageType(GetTemporalId(header),
+                                          retransmission_settings,
+                                          expected_retransmission_time_ms);
+  }
+};
+
 class RtpSenderVideoTest : public RtpSenderTest {
  protected:
   void SetUp() override {
     // TODO(pbos): Set up to use pacer.
     SetUpRtpSender(false);
     rtp_sender_video_.reset(
-        new RTPSenderVideo(&fake_clock_, rtp_sender_.get(), nullptr));
+        new TestRtpSenderVideo(&fake_clock_, rtp_sender_.get(), nullptr));
   }
-  std::unique_ptr<RTPSenderVideo> rtp_sender_video_;
+  std::unique_ptr<TestRtpSenderVideo> rtp_sender_video_;
 };
 
 TEST_P(RtpSenderTestWithoutPacer, AllocatePacketSetCsrc) {
@@ -861,9 +882,9 @@
   uint8_t payload[] = {47, 11, 32, 93, 89};
 
   // Send keyframe
-  ASSERT_TRUE(rtp_sender_->SendOutgoingData(kVideoFrameKey, payload_type, 1234,
-                                            4321, payload, sizeof(payload),
-                                            nullptr, nullptr, nullptr));
+  ASSERT_TRUE(rtp_sender_->SendOutgoingData(
+      kVideoFrameKey, payload_type, 1234, 4321, payload, sizeof(payload),
+      nullptr, nullptr, nullptr, kDefaultExpectedRetransmissionTimeMs));
 
   auto sent_payload = transport_.last_sent_packet().payload();
   uint8_t generic_header = sent_payload[0];
@@ -878,7 +899,7 @@
 
   ASSERT_TRUE(rtp_sender_->SendOutgoingData(
       kVideoFrameDelta, payload_type, 1234, 4321, payload, sizeof(payload),
-      nullptr, nullptr, nullptr));
+      nullptr, nullptr, nullptr, kDefaultExpectedRetransmissionTimeMs));
 
   sent_payload = transport_.last_sent_packet().payload();
   generic_header = sent_payload[0];
@@ -998,7 +1019,8 @@
   video_header.video_timing.flags = TimingFrameFlags::kTriggeredByTimer;
   EXPECT_TRUE(rtp_sender_->SendOutgoingData(
       kVideoFrameKey, kPayloadType, kTimestamp, kCaptureTimeMs, kPayloadData,
-      sizeof(kPayloadData), nullptr, &video_header, nullptr));
+      sizeof(kPayloadData), nullptr, &video_header, nullptr,
+      kDefaultExpectedRetransmissionTimeMs));
 
   EXPECT_CALL(mock_rtc_event_log_,
               LogRtpHeader(PacketDirection::kOutgoingPacket, _, _, _))
@@ -1023,7 +1045,8 @@
   video_header.video_timing.flags = TimingFrameFlags::kInvalid;
   EXPECT_TRUE(rtp_sender_->SendOutgoingData(
       kVideoFrameKey, kPayloadType, kTimestamp + 1, kCaptureTimeMs + 1,
-      kPayloadData, sizeof(kPayloadData), nullptr, &video_header, nullptr));
+      kPayloadData, sizeof(kPayloadData), nullptr, &video_header, nullptr,
+      kDefaultExpectedRetransmissionTimeMs));
 
   EXPECT_CALL(mock_rtc_event_log_,
               LogRtpHeader(PacketDirection::kOutgoingPacket, _, _, _))
@@ -1168,9 +1191,9 @@
   EXPECT_CALL(mock_paced_sender_, InsertPacket(_, _, _, _, _, _))
       .Times(::testing::AtLeast(2));
 
-  ASSERT_TRUE(rtp_sender_->SendOutgoingData(kVideoFrameKey, payload_type, 1234,
-                                            4321, payload, sizeof(payload),
-                                            nullptr, nullptr, nullptr));
+  ASSERT_TRUE(rtp_sender_->SendOutgoingData(
+      kVideoFrameKey, payload_type, 1234, 4321, payload, sizeof(payload),
+      nullptr, nullptr, nullptr, kDefaultExpectedRetransmissionTimeMs));
 
   EXPECT_EQ(1U, callback.num_calls_);
   EXPECT_EQ(ssrc, callback.ssrc_);
@@ -1179,7 +1202,7 @@
 
   ASSERT_TRUE(rtp_sender_->SendOutgoingData(
       kVideoFrameDelta, payload_type, 1234, 4321, payload, sizeof(payload),
-      nullptr, nullptr, nullptr));
+      nullptr, nullptr, nullptr, kDefaultExpectedRetransmissionTimeMs));
 
   EXPECT_EQ(2U, callback.num_calls_);
   EXPECT_EQ(ssrc, callback.ssrc_);
@@ -1245,7 +1268,7 @@
   for (uint32_t i = 0; i < kNumPackets; ++i) {
     ASSERT_TRUE(rtp_sender_->SendOutgoingData(
         kVideoFrameKey, payload_type, 1234, 4321, payload, sizeof(payload),
-        nullptr, nullptr, nullptr));
+        nullptr, nullptr, nullptr, kDefaultExpectedRetransmissionTimeMs));
     fake_clock_.AdvanceTimeMilliseconds(kPacketInterval);
   }
 
@@ -1327,8 +1350,8 @@
 
   // Send a frame.
   ASSERT_TRUE(rtp_sender_->SendOutgoingData(
-                      kVideoFrameKey, payload_type, 1234, 4321, payload,
-                      sizeof(payload), nullptr, nullptr, nullptr));
+      kVideoFrameKey, payload_type, 1234, 4321, payload, sizeof(payload),
+      nullptr, nullptr, nullptr, kDefaultExpectedRetransmissionTimeMs));
   StreamDataCounters expected;
   expected.transmitted.payload_bytes = 6;
   expected.transmitted.header_bytes = 12;
@@ -1369,8 +1392,8 @@
   fec_params.max_fec_frames = 1;
   rtp_sender_->SetFecParameters(fec_params, fec_params);
   ASSERT_TRUE(rtp_sender_->SendOutgoingData(
-                      kVideoFrameDelta, payload_type, 1234, 4321, payload,
-                      sizeof(payload), nullptr, nullptr, nullptr));
+      kVideoFrameDelta, payload_type, 1234, 4321, payload, sizeof(payload),
+      nullptr, nullptr, nullptr, kDefaultExpectedRetransmissionTimeMs));
   expected.transmitted.payload_bytes = 40;
   expected.transmitted.header_bytes = 60;
   expected.transmitted.packets = 5;
@@ -1388,8 +1411,8 @@
   uint8_t payload[] = {47, 11, 32, 93, 89};
 
   ASSERT_TRUE(rtp_sender_->SendOutgoingData(
-                      kAudioFrameCN, payload_type, 1234, 4321, payload,
-                      sizeof(payload), nullptr, nullptr, nullptr));
+      kAudioFrameCN, payload_type, 1234, 4321, payload, sizeof(payload),
+      nullptr, nullptr, nullptr, kDefaultExpectedRetransmissionTimeMs));
 
   auto sent_payload = transport_.last_sent_packet().payload();
   EXPECT_THAT(sent_payload, ElementsAreArray(payload));
@@ -1407,8 +1430,8 @@
   uint8_t payload[] = {47, 11, 32, 93, 89};
 
   ASSERT_TRUE(rtp_sender_->SendOutgoingData(
-                      kAudioFrameCN, payload_type, 1234, 4321, payload,
-                      sizeof(payload), nullptr, nullptr, nullptr));
+      kAudioFrameCN, payload_type, 1234, 4321, payload, sizeof(payload),
+      nullptr, nullptr, nullptr, kDefaultExpectedRetransmissionTimeMs));
 
   auto sent_payload = transport_.last_sent_packet().payload();
   EXPECT_THAT(sent_payload, ElementsAreArray(payload));
@@ -1445,22 +1468,22 @@
   // During start, it takes the starting timestamp as last sent timestamp.
   // The duration is calculated as the difference of current and last sent
   // timestamp. So for first call it will skip since the duration is zero.
-  ASSERT_TRUE(rtp_sender_->SendOutgoingData(kEmptyFrame, kPayloadType,
-                                            capture_time_ms, 0, nullptr, 0,
-                                            nullptr, nullptr, nullptr));
+  ASSERT_TRUE(rtp_sender_->SendOutgoingData(
+      kEmptyFrame, kPayloadType, capture_time_ms, 0, nullptr, 0, nullptr,
+      nullptr, nullptr, kDefaultExpectedRetransmissionTimeMs));
   // DTMF Sample Length is (Frequency/1000) * Duration.
   // So in this case, it is (8000/1000) * 500 = 4000.
   // Sending it as two packets.
   ASSERT_TRUE(rtp_sender_->SendOutgoingData(
-                      kEmptyFrame, kPayloadType, capture_time_ms + 2000, 0,
-                      nullptr, 0, nullptr, nullptr, nullptr));
+      kEmptyFrame, kPayloadType, capture_time_ms + 2000, 0, nullptr, 0, nullptr,
+      nullptr, nullptr, kDefaultExpectedRetransmissionTimeMs));
 
   // Marker Bit should be set to 1 for first packet.
   EXPECT_TRUE(transport_.last_sent_packet().Marker());
 
   ASSERT_TRUE(rtp_sender_->SendOutgoingData(
-                      kEmptyFrame, kPayloadType, capture_time_ms + 4000, 0,
-                      nullptr, 0, nullptr, nullptr, nullptr));
+      kEmptyFrame, kPayloadType, capture_time_ms + 4000, 0, nullptr, 0, nullptr,
+      nullptr, nullptr, kDefaultExpectedRetransmissionTimeMs));
   // Marker Bit should be set to 0 for rest of the packets.
   EXPECT_FALSE(transport_.last_sent_packet().Marker());
 }
@@ -1478,8 +1501,8 @@
   uint8_t payload[] = {47, 11, 32, 93, 89};
 
   ASSERT_TRUE(rtp_sender_->SendOutgoingData(
-                      kVideoFrameKey, kPayloadType, 1234, 4321, payload,
-                      sizeof(payload), nullptr, nullptr, nullptr));
+      kVideoFrameKey, kPayloadType, 1234, 4321, payload, sizeof(payload),
+      nullptr, nullptr, nullptr, kDefaultExpectedRetransmissionTimeMs));
 
   // Will send 2 full-size padding packets.
   rtp_sender_->TimeToSendPadding(1, PacedPacketInfo());
@@ -1553,7 +1576,7 @@
   hdr.rotation = kVideoRotation_0;
   rtp_sender_video_->SendVideo(kRtpVideoGeneric, kVideoFrameKey, kPayload,
                                kTimestamp, 0, kFrame, sizeof(kFrame), nullptr,
-                               &hdr);
+                               &hdr, kDefaultExpectedRetransmissionTimeMs);
 
   VideoRotation rotation;
   EXPECT_TRUE(
@@ -1579,7 +1602,8 @@
   fake_clock_.AdvanceTimeMilliseconds(kPacketizationTimeMs);
   rtp_sender_video_->SendVideo(kRtpVideoGeneric, kVideoFrameKey, kPayload,
                                kTimestamp, kCaptureTimestamp, kFrame,
-                               sizeof(kFrame), nullptr, &hdr);
+                               sizeof(kFrame), nullptr, &hdr,
+                               kDefaultExpectedRetransmissionTimeMs);
   VideoSendTiming timing;
   EXPECT_TRUE(transport_.last_sent_packet().GetExtension<VideoTimingExtension>(
       &timing));
@@ -1595,14 +1619,14 @@
 
   RTPVideoHeader hdr = {0};
   hdr.rotation = kVideoRotation_90;
-  EXPECT_TRUE(rtp_sender_video_->SendVideo(kRtpVideoGeneric, kVideoFrameKey,
-                                           kPayload, kTimestamp, 0, kFrame,
-                                           sizeof(kFrame), nullptr, &hdr));
+  EXPECT_TRUE(rtp_sender_video_->SendVideo(
+      kRtpVideoGeneric, kVideoFrameKey, kPayload, kTimestamp, 0, kFrame,
+      sizeof(kFrame), nullptr, &hdr, kDefaultExpectedRetransmissionTimeMs));
 
   hdr.rotation = kVideoRotation_0;
-  EXPECT_TRUE(rtp_sender_video_->SendVideo(kRtpVideoGeneric, kVideoFrameDelta,
-                                           kPayload, kTimestamp + 1, 0, kFrame,
-                                           sizeof(kFrame), nullptr, &hdr));
+  EXPECT_TRUE(rtp_sender_video_->SendVideo(
+      kRtpVideoGeneric, kVideoFrameDelta, kPayload, kTimestamp + 1, 0, kFrame,
+      sizeof(kFrame), nullptr, &hdr, kDefaultExpectedRetransmissionTimeMs));
 
   VideoRotation rotation;
   EXPECT_TRUE(
@@ -1617,13 +1641,13 @@
 
   RTPVideoHeader hdr = {0};
   hdr.rotation = kVideoRotation_90;
-  EXPECT_TRUE(rtp_sender_video_->SendVideo(kRtpVideoGeneric, kVideoFrameKey,
-                                           kPayload, kTimestamp, 0, kFrame,
-                                           sizeof(kFrame), nullptr, &hdr));
+  EXPECT_TRUE(rtp_sender_video_->SendVideo(
+      kRtpVideoGeneric, kVideoFrameKey, kPayload, kTimestamp, 0, kFrame,
+      sizeof(kFrame), nullptr, &hdr, kDefaultExpectedRetransmissionTimeMs));
 
-  EXPECT_TRUE(rtp_sender_video_->SendVideo(kRtpVideoGeneric, kVideoFrameDelta,
-                                           kPayload, kTimestamp + 1, 0, kFrame,
-                                           sizeof(kFrame), nullptr, &hdr));
+  EXPECT_TRUE(rtp_sender_video_->SendVideo(
+      kRtpVideoGeneric, kVideoFrameDelta, kPayload, kTimestamp + 1, 0, kFrame,
+      sizeof(kFrame), nullptr, &hdr, kDefaultExpectedRetransmissionTimeMs));
 
   VideoRotation rotation;
   EXPECT_TRUE(
@@ -1652,6 +1676,224 @@
             ConvertCVOByteToVideoRotation(flip_bit | camera_bit | 3));
 }
 
+TEST_P(RtpSenderVideoTest, RetransmissionTypesGeneric) {
+  RTPVideoHeader header;
+  header.codec = kRtpVideoGeneric;
+
+  EXPECT_EQ(kDontRetransmit,
+            rtp_sender_video_->GetStorageType(
+                header, kRetransmitOff, kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(kAllowRetransmission, rtp_sender_video_->GetStorageType(
+                                      header, kRetransmitBaseLayer,
+                                      kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(kAllowRetransmission, rtp_sender_video_->GetStorageType(
+                                      header, kRetransmitHigherLayers,
+                                      kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(kAllowRetransmission,
+            rtp_sender_video_->GetStorageType(
+                header, kConditionallyRetransmitHigherLayers,
+                kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(kAllowRetransmission, rtp_sender_video_->GetStorageType(
+                                      header, kRetransmitAllPackets,
+                                      kDefaultExpectedRetransmissionTimeMs));
+}
+
+TEST_P(RtpSenderVideoTest, RetransmissionTypesH264) {
+  RTPVideoHeader header;
+  header.codec = kRtpVideoH264;
+  header.codecHeader.H264.packetization_mode =
+      H264PacketizationMode::NonInterleaved;
+
+  EXPECT_EQ(kDontRetransmit,
+            rtp_sender_video_->GetStorageType(
+                header, kRetransmitOff, kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(kAllowRetransmission, rtp_sender_video_->GetStorageType(
+                                      header, kRetransmitBaseLayer,
+                                      kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(kAllowRetransmission, rtp_sender_video_->GetStorageType(
+                                      header, kRetransmitHigherLayers,
+                                      kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(kAllowRetransmission,
+            rtp_sender_video_->GetStorageType(
+                header, kConditionallyRetransmitHigherLayers,
+                kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(kAllowRetransmission, rtp_sender_video_->GetStorageType(
+                                      header, kRetransmitAllPackets,
+                                      kDefaultExpectedRetransmissionTimeMs));
+}
+
+TEST_P(RtpSenderVideoTest, RetransmissionTypesVP8BaseLayer) {
+  RTPVideoHeader header;
+  header.codec = kRtpVideoVp8;
+  header.codecHeader.VP8.temporalIdx = 0;
+
+  EXPECT_EQ(kDontRetransmit,
+            rtp_sender_video_->GetStorageType(
+                header, kRetransmitOff, kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(kAllowRetransmission, rtp_sender_video_->GetStorageType(
+                                      header, kRetransmitBaseLayer,
+                                      kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(kDontRetransmit, rtp_sender_video_->GetStorageType(
+                                 header, kRetransmitHigherLayers,
+                                 kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(kAllowRetransmission,
+            rtp_sender_video_->GetStorageType(
+                header, kRetransmitHigherLayers | kRetransmitBaseLayer,
+                kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(kDontRetransmit, rtp_sender_video_->GetStorageType(
+                                 header, kConditionallyRetransmitHigherLayers,
+                                 kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(
+      kAllowRetransmission,
+      rtp_sender_video_->GetStorageType(
+          header, kRetransmitBaseLayer | kConditionallyRetransmitHigherLayers,
+          kDefaultExpectedRetransmissionTimeMs));
+  EXPECT_EQ(kAllowRetransmission, rtp_sender_video_->GetStorageType(
+                                      header, kRetransmitAllPackets,
+                                      kDefaultExpectedRetransmissionTimeMs));
+}
+
+TEST_P(RtpSenderVideoTest, RetransmissionTypesVP8HigherLayers) {
+  RTPVideoHeader header;
+  header.codec = kRtpVideoVp8;
+
+  for (int tid = 1; tid <= kMaxTemporalStreams; ++tid) {
+    header.codecHeader.VP8.temporalIdx = tid;
+
+    EXPECT_EQ(kDontRetransmit, rtp_sender_video_->GetStorageType(
+                                   header, kRetransmitOff,
+                                   kDefaultExpectedRetransmissionTimeMs));
+    EXPECT_EQ(kDontRetransmit, rtp_sender_video_->GetStorageType(
+                                   header, kRetransmitBaseLayer,
+                                   kDefaultExpectedRetransmissionTimeMs));
+    EXPECT_EQ(kAllowRetransmission, rtp_sender_video_->GetStorageType(
+                                        header, kRetransmitHigherLayers,
+                                        kDefaultExpectedRetransmissionTimeMs));
+    EXPECT_EQ(kAllowRetransmission,
+              rtp_sender_video_->GetStorageType(
+                  header, kRetransmitHigherLayers | kRetransmitBaseLayer,
+                  kDefaultExpectedRetransmissionTimeMs));
+    EXPECT_EQ(kAllowRetransmission, rtp_sender_video_->GetStorageType(
+                                        header, kRetransmitAllPackets,
+                                        kDefaultExpectedRetransmissionTimeMs));
+  }
+}
+
+TEST_P(RtpSenderVideoTest, RetransmissionTypesVP9) {
+  RTPVideoHeader header;
+  header.codec = kRtpVideoVp9;
+
+  for (int tid = 1; tid <= kMaxTemporalStreams; ++tid) {
+    header.codecHeader.VP9.temporal_idx = tid;
+
+    EXPECT_EQ(kDontRetransmit, rtp_sender_video_->GetStorageType(
+                                   header, kRetransmitOff,
+                                   kDefaultExpectedRetransmissionTimeMs));
+    EXPECT_EQ(kDontRetransmit, rtp_sender_video_->GetStorageType(
+                                   header, kRetransmitBaseLayer,
+                                   kDefaultExpectedRetransmissionTimeMs));
+    EXPECT_EQ(kAllowRetransmission, rtp_sender_video_->GetStorageType(
+                                        header, kRetransmitHigherLayers,
+                                        kDefaultExpectedRetransmissionTimeMs));
+    EXPECT_EQ(kAllowRetransmission,
+              rtp_sender_video_->GetStorageType(
+                  header, kRetransmitHigherLayers | kRetransmitBaseLayer,
+                  kDefaultExpectedRetransmissionTimeMs));
+    EXPECT_EQ(kAllowRetransmission, rtp_sender_video_->GetStorageType(
+                                        header, kRetransmitAllPackets,
+                                        kDefaultExpectedRetransmissionTimeMs));
+  }
+}
+
+TEST_P(RtpSenderVideoTest, ConditionalRetransmit) {
+  const int64_t kFrameIntervalMs = 33;
+  const int64_t kRttMs = (kFrameIntervalMs * 3) / 2;
+  const uint8_t kSettings =
+      kRetransmitBaseLayer | kConditionallyRetransmitHigherLayers;
+
+  // Insert VP8 frames for all temporal layers, but stop before the final index.
+  RTPVideoHeader header;
+  header.codec = kRtpVideoVp8;
+
+  // Fill averaging window to prevent rounding errors.
+  constexpr int kNumRepetitions =
+      (RTPSenderVideo::kTLRateWindowSizeMs + (kFrameIntervalMs / 2)) /
+      kFrameIntervalMs;
+  constexpr int kPattern[] = {0, 2, 1, 2};
+  for (size_t i = 0; i < arraysize(kPattern) * kNumRepetitions; ++i) {
+    header.codecHeader.VP8.temporalIdx = kPattern[i % arraysize(kPattern)];
+    rtp_sender_video_->GetStorageType(header, kSettings, kRttMs);
+    fake_clock_.AdvanceTimeMilliseconds(kFrameIntervalMs);
+  }
+
+  // Since we're at the start of the pattern, the next expected frame in TL0 is
+  // right now. We will wait at most one expected retransmission time before
+  // acknowledging that it did not arrive, which means this frame and the next
+  // will not be retransmitted.
+  header.codecHeader.VP8.temporalIdx = 1;
+  EXPECT_EQ(StorageType::kDontRetransmit,
+            rtp_sender_video_->GetStorageType(header, kSettings, kRttMs));
+  fake_clock_.AdvanceTimeMilliseconds(kFrameIntervalMs);
+  EXPECT_EQ(StorageType::kDontRetransmit,
+            rtp_sender_video_->GetStorageType(header, kSettings, kRttMs));
+  fake_clock_.AdvanceTimeMilliseconds(kFrameIntervalMs);
+
+  // The TL0 frame did not arrive. So allow retransmission.
+  EXPECT_EQ(StorageType::kAllowRetransmission,
+            rtp_sender_video_->GetStorageType(header, kSettings, kRttMs));
+  fake_clock_.AdvanceTimeMilliseconds(kFrameIntervalMs);
+
+  // Insert a frame for TL2. We just had frame in TL1, so the next one there is
+  // in three frames away. TL0 is still too far in the past. So, allow
+  // retransmission.
+  header.codecHeader.VP8.temporalIdx = 2;
+  EXPECT_EQ(StorageType::kAllowRetransmission,
+            rtp_sender_video_->GetStorageType(header, kSettings, kRttMs));
+  fake_clock_.AdvanceTimeMilliseconds(kFrameIntervalMs);
+
+  // Another TL2, next in TL1 is two frames away. Allow again.
+  EXPECT_EQ(StorageType::kAllowRetransmission,
+            rtp_sender_video_->GetStorageType(header, kSettings, kRttMs));
+  fake_clock_.AdvanceTimeMilliseconds(kFrameIntervalMs);
+
+  // Yet another TL2, next in TL1 is now only one frame away, so don't store
+  // for retransmission.
+  EXPECT_EQ(StorageType::kDontRetransmit,
+            rtp_sender_video_->GetStorageType(header, kSettings, kRttMs));
+}
+
+TEST_P(RtpSenderVideoTest, ConditionalRetransmitLimit) {
+  const int64_t kFrameIntervalMs = 200;
+  const int64_t kRttMs = (kFrameIntervalMs * 3) / 2;
+  const int32_t kSettings =
+      kRetransmitBaseLayer | kConditionallyRetransmitHigherLayers;
+
+  // Insert VP8 frames for all temporal layers, but stop before the final index.
+  RTPVideoHeader header;
+  header.codec = kRtpVideoVp8;
+
+  // Fill averaging window to prevent rounding errors.
+  constexpr int kNumRepetitions =
+      (RTPSenderVideo::kTLRateWindowSizeMs + (kFrameIntervalMs / 2)) /
+      kFrameIntervalMs;
+  constexpr int kPattern[] = {0, 2, 2, 2};
+  for (size_t i = 0; i < arraysize(kPattern) * kNumRepetitions; ++i) {
+    header.codecHeader.VP8.temporalIdx = kPattern[i % arraysize(kPattern)];
+
+    rtp_sender_video_->GetStorageType(header, kSettings, kRttMs);
+    fake_clock_.AdvanceTimeMilliseconds(kFrameIntervalMs);
+  }
+
+  // Since we're at the start of the pattern, the next expected frame will be
+  // right now in TL0. Put it in TL1 instead. Regular rules would dictate that
+  // we don't store for retransmission because we expect a frame in a lower
+  // layer, but that last frame in TL1 was a long time ago in absolute terms,
+  // so allow retransmission anyway.
+  header.codecHeader.VP8.temporalIdx = 1;
+  EXPECT_EQ(StorageType::kAllowRetransmission,
+            rtp_sender_video_->GetStorageType(header, kSettings, kRttMs));
+}
+
 TEST_P(RtpSenderTest, OnOverheadChanged) {
   MockOverheadObserver mock_overhead_observer;
   rtp_sender_.reset(
diff --git a/modules/rtp_rtcp/source/rtp_sender_video.cc b/modules/rtp_rtcp/source/rtp_sender_video.cc
index 3845074..4e46b78 100644
--- a/modules/rtp_rtcp/source/rtp_sender_video.cc
+++ b/modules/rtp_rtcp/source/rtp_sender_video.cc
@@ -13,9 +13,10 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <limits>
 #include <memory>
-#include <vector>
 #include <utility>
+#include <vector>
 
 #include "webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h"
 #include "webrtc/modules/rtp_rtcp/source/byte_io.h"
@@ -33,6 +34,7 @@
 
 namespace {
 constexpr size_t kRedForFecHeaderLength = 1;
+constexpr int64_t kMaxUnretransmittableFrameIntervalMs = 33 * 4;
 
 void BuildRedPayload(const RtpPacketToSend& media_packet,
                      RtpPacketToSend* red_packet) {
@@ -53,7 +55,8 @@
     : rtp_sender_(rtp_sender),
       clock_(clock),
       video_type_(kRtpVideoGeneric),
-      retransmission_settings_(kRetransmitBaseLayer),
+      retransmission_settings_(kRetransmitBaseLayer |
+                               kConditionallyRetransmitHigherLayers),
       last_rotation_(kVideoRotation_0),
       red_payload_type_(-1),
       ulpfec_payload_type_(-1),
@@ -292,7 +295,8 @@
                                const uint8_t* payload_data,
                                size_t payload_size,
                                const RTPFragmentationHeader* fragmentation,
-                               const RTPVideoHeader* video_header) {
+                               const RTPVideoHeader* video_header,
+                               int64_t expected_retransmission_time_ms) {
   if (payload_size == 0)
     return false;
 
@@ -365,8 +369,11 @@
   std::unique_ptr<RtpPacketizer> packetizer(RtpPacketizer::Create(
       video_type, max_data_payload_length, last_packet_reduction_len,
       video_header ? &(video_header->codecHeader) : nullptr, frame_type));
-  // Media packet storage.
-  StorageType storage = packetizer->GetStorageType(retransmission_settings);
+
+  const uint8_t temporal_id =
+      video_header ? GetTemporalId(*video_header) : kNoTemporalIdx;
+  StorageType storage = GetStorageType(temporal_id, retransmission_settings,
+                                       expected_retransmission_time_ms);
 
   // TODO(changbin): we currently don't support to configure the codec to
   // output multiple partitions for VP8. Should remove below check after the
@@ -392,7 +399,9 @@
     if (!rtp_sender_->AssignSequenceNumber(packet.get()))
       return false;
 
-    bool protect_packet = (packetizer->GetProtectionType() == kProtectedPacket);
+    // No FEC protection for upper temporal layers, if used.
+    bool protect_packet = temporal_id == 0 || temporal_id == kNoTemporalIdx;
+
     // Put packetization finish timestamp into extension.
     if (packet->HasExtension<VideoTimingExtension>()) {
       packet->set_packetization_finish_time_ms(clock_->TimeInMilliseconds());
@@ -453,4 +462,90 @@
   retransmission_settings_ = settings;
 }
 
+StorageType RTPSenderVideo::GetStorageType(
+    uint8_t temporal_id,
+    int32_t retransmission_settings,
+    int64_t expected_retransmission_time_ms) {
+  if (retransmission_settings == kRetransmitOff)
+    return StorageType::kDontRetransmit;
+  if (retransmission_settings == kRetransmitAllPackets)
+    return StorageType::kAllowRetransmission;
+
+  rtc::CritScope cs(&stats_crit_);
+  // Media packet storage.
+  if ((retransmission_settings & kConditionallyRetransmitHigherLayers) &&
+      UpdateConditionalRetransmit(temporal_id,
+                                  expected_retransmission_time_ms)) {
+    retransmission_settings |= kRetransmitHigherLayers;
+  }
+
+  if (temporal_id == kNoTemporalIdx)
+    return kAllowRetransmission;
+
+  if ((retransmission_settings & kRetransmitBaseLayer) && temporal_id == 0)
+    return kAllowRetransmission;
+
+  if ((retransmission_settings & kRetransmitHigherLayers) && temporal_id > 0)
+    return kAllowRetransmission;
+
+  return kDontRetransmit;
+}
+
+uint8_t RTPSenderVideo::GetTemporalId(const RTPVideoHeader& header) {
+  switch (header.codec) {
+    case kRtpVideoVp8:
+      return header.codecHeader.VP8.temporalIdx;
+    case kRtpVideoVp9:
+      return header.codecHeader.VP9.temporal_idx;
+    default:
+      return kNoTemporalIdx;
+  }
+}
+
+bool RTPSenderVideo::UpdateConditionalRetransmit(
+    uint8_t temporal_id,
+    int64_t expected_retransmission_time_ms) {
+  int64_t now_ms = clock_->TimeInMilliseconds();
+  // Update stats for any temporal layer.
+  TemporalLayerStats* current_layer_stats =
+      &frame_stats_by_temporal_layer_[temporal_id];
+  current_layer_stats->frame_rate_fp1000s.Update(1, now_ms);
+  int64_t tl_frame_interval = now_ms - current_layer_stats->last_frame_time_ms;
+  current_layer_stats->last_frame_time_ms = now_ms;
+
+  // Conditional retransmit only applies to upper layers.
+  if (temporal_id != kNoTemporalIdx && temporal_id > 0) {
+    if (tl_frame_interval >= kMaxUnretransmittableFrameIntervalMs) {
+      // Too long since a retransmittable frame in this layer, enable NACK
+      // protection.
+      return true;
+    } else {
+      // Estimate when the next frame of any lower layer will be sent.
+      const int64_t kUndefined = std::numeric_limits<int64_t>::max();
+      int64_t expected_next_frame_time = kUndefined;
+      for (int i = temporal_id - 1; i >= 0; --i) {
+        TemporalLayerStats* stats = &frame_stats_by_temporal_layer_[i];
+        rtc::Optional<uint32_t> rate = stats->frame_rate_fp1000s.Rate(now_ms);
+        if (rate) {
+          int64_t tl_next = stats->last_frame_time_ms + 1000000 / *rate;
+          if (tl_next - now_ms > -expected_retransmission_time_ms &&
+              tl_next < expected_next_frame_time) {
+            expected_next_frame_time = tl_next;
+          }
+        }
+      }
+
+      if (expected_next_frame_time == kUndefined ||
+          expected_next_frame_time - now_ms > expected_retransmission_time_ms) {
+        // The next frame in a lower layer is expected at a later time (or
+        // unable to tell due to lack of data) than a retransmission is
+        // estimated to be able to arrive, so allow this packet to be nacked.
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
 }  // namespace webrtc
diff --git a/modules/rtp_rtcp/source/rtp_sender_video.h b/modules/rtp_rtcp/source/rtp_sender_video.h
index 9fb4648..e4a2405 100644
--- a/modules/rtp_rtcp/source/rtp_sender_video.h
+++ b/modules/rtp_rtcp/source/rtp_sender_video.h
@@ -11,9 +11,8 @@
 #ifndef WEBRTC_MODULES_RTP_RTCP_SOURCE_RTP_SENDER_VIDEO_H_
 #define WEBRTC_MODULES_RTP_RTCP_SOURCE_RTP_SENDER_VIDEO_H_
 
-#include <list>
+#include <map>
 #include <memory>
-#include <vector>
 
 #include "webrtc/common_types.h"
 #include "webrtc/modules/rtp_rtcp/include/flexfec_sender.h"
@@ -32,10 +31,13 @@
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
+class RtpPacketizer;
 class RtpPacketToSend;
 
 class RTPSenderVideo {
  public:
+  static constexpr int64_t kTLRateWindowSizeMs = 2500;
+
   RTPSenderVideo(Clock* clock,
                  RTPSender* rtpSender,
                  FlexfecSender* flexfec_sender);
@@ -55,7 +57,8 @@
                  const uint8_t* payload_data,
                  size_t payload_size,
                  const RTPFragmentationHeader* fragmentation,
-                 const RTPVideoHeader* video_header);
+                 const RTPVideoHeader* video_header,
+                 int64_t expected_retransmission_time_ms);
 
   void SetVideoCodecType(RtpVideoCodecTypes type);
 
@@ -76,7 +79,24 @@
   int SelectiveRetransmissions() const;
   void SetSelectiveRetransmissions(uint8_t settings);
 
+ protected:
+  static uint8_t GetTemporalId(const RTPVideoHeader& header);
+  StorageType GetStorageType(uint8_t temporal_id,
+                             int32_t retransmission_settings,
+                             int64_t expected_retransmission_time_ms);
+
  private:
+  struct TemporalLayerStats {
+    TemporalLayerStats()
+        : frame_rate_fp1000s(kTLRateWindowSizeMs, 1000 * 1000),
+          last_frame_time_ms(0) {}
+    // Frame rate, in frames per 1000 seconds. This essentially turns the fps
+    // value into a fixed point value with three decimals. Improves precision at
+    // low frame rates.
+    RateStatistics frame_rate_fp1000s;
+    int64_t last_frame_time_ms;
+  };
+
   size_t CalculateFecPacketOverhead() const EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   void SendVideoPacket(std::unique_ptr<RtpPacketToSend> packet,
@@ -103,6 +123,10 @@
 
   bool flexfec_enabled() const { return flexfec_sender_ != nullptr; }
 
+  bool UpdateConditionalRetransmit(uint8_t temporal_id,
+                                   int64_t expected_retransmission_time_ms)
+      EXCLUSIVE_LOCKS_REQUIRED(stats_crit_);
+
   RTPSender* const rtp_sender_;
   Clock* const clock_;
 
@@ -131,6 +155,10 @@
   RateStatistics fec_bitrate_ GUARDED_BY(stats_crit_);
   // Bitrate used for video payload and RTP headers.
   RateStatistics video_bitrate_ GUARDED_BY(stats_crit_);
+
+  std::map<int, TemporalLayerStats> frame_stats_by_temporal_layer_
+      GUARDED_BY(stats_crit_);
+
   OneTimeEvent first_frame_sent_;
 };