Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 552 insertions, 0 deletions

diff --git a/third_party/libwebrtc/modules/audio_coding/neteq/nack_tracker_unittest.cc b/third_party/libwebrtc/modules/audio_coding/neteq/nack_tracker_unittest.cc
new file mode 100644
index 0000000000..a843425b78
--- /dev/null
+++ b/third_party/libwebrtc/modules/audio_coding/neteq/nack_tracker_unittest.cc
@@ -0,0 +1,552 @@
+/*
+ *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "modules/audio_coding/neteq/nack_tracker.h"
+
+#include <stdint.h>
+
+#include <algorithm>
+#include <memory>
+
+#include "modules/audio_coding/include/audio_coding_module_typedefs.h"
+#include "test/field_trial.h"
+#include "test/gtest.h"
+
+namespace webrtc {
+namespace {
+
+const int kSampleRateHz = 16000;
+const int kPacketSizeMs = 30;
+const uint32_t kTimestampIncrement = 480;  // 30 ms.
+const int64_t kShortRoundTripTimeMs = 1;
+
+bool IsNackListCorrect(const std::vector<uint16_t>& nack_list,
+                       const uint16_t* lost_sequence_numbers,
+                       size_t num_lost_packets) {
+  if (nack_list.size() != num_lost_packets)
+    return false;
+
+  if (num_lost_packets == 0)
+    return true;
+
+  for (size_t k = 0; k < nack_list.size(); ++k) {
+    int seq_num = nack_list[k];
+    bool seq_num_matched = false;
+    for (size_t n = 0; n < num_lost_packets; ++n) {
+      if (seq_num == lost_sequence_numbers[n]) {
+        seq_num_matched = true;
+        break;
+      }
+    }
+    if (!seq_num_matched)
+      return false;
+  }
+  return true;
+}
+
+}  // namespace
+
+TEST(NackTrackerTest, EmptyListWhenNoPacketLoss) {
+  NackTracker nack;
+  nack.UpdateSampleRate(kSampleRateHz);
+
+  int seq_num = 1;
+  uint32_t timestamp = 0;
+
+  std::vector<uint16_t> nack_list;
+  for (int n = 0; n < 100; n++) {
+    nack.UpdateLastReceivedPacket(seq_num, timestamp);
+    nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+    seq_num++;
+    timestamp += kTimestampIncrement;
+    nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+    EXPECT_TRUE(nack_list.empty());
+  }
+}
+
+TEST(NackTrackerTest, LatePacketsMovedToNackThenNackListDoesNotChange) {
+  const uint16_t kSequenceNumberLostPackets[] = {2, 3, 4, 5, 6, 7, 8, 9};
+  static const int kNumAllLostPackets = sizeof(kSequenceNumberLostPackets) /
+                                        sizeof(kSequenceNumberLostPackets[0]);
+
+  for (int k = 0; k < 2; k++) {  // Two iteration with/without wrap around.
+    NackTracker nack;
+    nack.UpdateSampleRate(kSampleRateHz);
+
+    uint16_t sequence_num_lost_packets[kNumAllLostPackets];
+    for (int n = 0; n < kNumAllLostPackets; n++) {
+      sequence_num_lost_packets[n] =
+          kSequenceNumberLostPackets[n] +
+          k * 65531;  // Have wrap around in sequence numbers for |k == 1|.
+    }
+    uint16_t seq_num = sequence_num_lost_packets[0] - 1;
+
+    uint32_t timestamp = 0;
+    std::vector<uint16_t> nack_list;
+
+    nack.UpdateLastReceivedPacket(seq_num, timestamp);
+    nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+    EXPECT_TRUE(nack_list.empty());
+
+    seq_num = sequence_num_lost_packets[kNumAllLostPackets - 1] + 1;
+    timestamp += kTimestampIncrement * (kNumAllLostPackets + 1);
+    int num_lost_packets = std::max(0, kNumAllLostPackets);
+
+    nack.UpdateLastReceivedPacket(seq_num, timestamp);
+    nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+    EXPECT_TRUE(IsNackListCorrect(nack_list, sequence_num_lost_packets,
+                                  num_lost_packets));
+    seq_num++;
+    timestamp += kTimestampIncrement;
+    num_lost_packets++;
+
+    for (int n = 0; n < 100; ++n) {
+      nack.UpdateLastReceivedPacket(seq_num, timestamp);
+      nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+      EXPECT_TRUE(IsNackListCorrect(nack_list, sequence_num_lost_packets,
+                                    kNumAllLostPackets));
+      seq_num++;
+      timestamp += kTimestampIncrement;
+    }
+  }
+}
+
+TEST(NackTrackerTest, ArrivedPacketsAreRemovedFromNackList) {
+  const uint16_t kSequenceNumberLostPackets[] = {2, 3, 4, 5, 6, 7, 8, 9};
+  static const int kNumAllLostPackets = sizeof(kSequenceNumberLostPackets) /
+                                        sizeof(kSequenceNumberLostPackets[0]);
+
+  for (int k = 0; k < 2; ++k) {  // Two iteration with/without wrap around.
+    NackTracker nack;
+    nack.UpdateSampleRate(kSampleRateHz);
+
+    uint16_t sequence_num_lost_packets[kNumAllLostPackets];
+    for (int n = 0; n < kNumAllLostPackets; ++n) {
+      sequence_num_lost_packets[n] = kSequenceNumberLostPackets[n] +
+                                     k * 65531;  // Wrap around for |k == 1|.
+    }
+
+    uint16_t seq_num = sequence_num_lost_packets[0] - 1;
+    uint32_t timestamp = 0;
+
+    nack.UpdateLastReceivedPacket(seq_num, timestamp);
+    std::vector<uint16_t> nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+    EXPECT_TRUE(nack_list.empty());
+
+    size_t index_retransmitted_rtp = 0;
+    uint32_t timestamp_retransmitted_rtp = timestamp + kTimestampIncrement;
+
+    seq_num = sequence_num_lost_packets[kNumAllLostPackets - 1] + 1;
+    timestamp += kTimestampIncrement * (kNumAllLostPackets + 1);
+    size_t num_lost_packets = kNumAllLostPackets;
+    for (int n = 0; n < kNumAllLostPackets; ++n) {
+      // Number of lost packets does not change for the first
+      // |kNackThreshold + 1| packets, one is added to the list and one is
+      // removed. Thereafter, the list shrinks every iteration.
+      if (n >= 1)
+        num_lost_packets--;
+
+      nack.UpdateLastReceivedPacket(seq_num, timestamp);
+      nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+      EXPECT_TRUE(IsNackListCorrect(
+          nack_list, &sequence_num_lost_packets[index_retransmitted_rtp],
+          num_lost_packets));
+      seq_num++;
+      timestamp += kTimestampIncrement;
+
+      // Retransmission of a lost RTP.
+      nack.UpdateLastReceivedPacket(
+          sequence_num_lost_packets[index_retransmitted_rtp],
+          timestamp_retransmitted_rtp);
+      index_retransmitted_rtp++;
+      timestamp_retransmitted_rtp += kTimestampIncrement;
+
+      nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+      EXPECT_TRUE(IsNackListCorrect(
+          nack_list, &sequence_num_lost_packets[index_retransmitted_rtp],
+          num_lost_packets - 1));  // One less lost packet in the list.
+    }
+    ASSERT_TRUE(nack_list.empty());
+  }
+}
+
+// Assess if estimation of timestamps and time-to-play is correct. Introduce all
+// combinations that timestamps and sequence numbers might have wrap around.
+TEST(NackTrackerTest, EstimateTimestampAndTimeToPlay) {
+  const uint16_t kLostPackets[] = {2, 3,  4,  5,  6,  7,  8,
+                                   9, 10, 11, 12, 13, 14, 15};
+  static const int kNumAllLostPackets =
+      sizeof(kLostPackets) / sizeof(kLostPackets[0]);
+
+  for (int k = 0; k < 4; ++k) {
+    NackTracker nack;
+    nack.UpdateSampleRate(kSampleRateHz);
+
+    // Sequence number wrap around if `k` is 2 or 3;
+    int seq_num_offset = (k < 2) ? 0 : 65531;
+
+    // Timestamp wrap around if `k` is 1 or 3.
+    uint32_t timestamp_offset =
+        (k & 0x1) ? static_cast<uint32_t>(0xffffffff) - 6 : 0;
+
+    uint32_t timestamp_lost_packets[kNumAllLostPackets];
+    uint16_t seq_num_lost_packets[kNumAllLostPackets];
+    for (int n = 0; n < kNumAllLostPackets; ++n) {
+      timestamp_lost_packets[n] =
+          timestamp_offset + kLostPackets[n] * kTimestampIncrement;
+      seq_num_lost_packets[n] = seq_num_offset + kLostPackets[n];
+    }
+
+    // We and to push two packets before lost burst starts.
+    uint16_t seq_num = seq_num_lost_packets[0] - 2;
+    uint32_t timestamp = timestamp_lost_packets[0] - 2 * kTimestampIncrement;
+
+    const uint16_t first_seq_num = seq_num;
+    const uint32_t first_timestamp = timestamp;
+
+    // Two consecutive packets to have a correct estimate of timestamp increase.
+    nack.UpdateLastReceivedPacket(seq_num, timestamp);
+    seq_num++;
+    timestamp += kTimestampIncrement;
+    nack.UpdateLastReceivedPacket(seq_num, timestamp);
+
+    // A packet after the last one which is supposed to be lost.
+    seq_num = seq_num_lost_packets[kNumAllLostPackets - 1] + 1;
+    timestamp =
+        timestamp_lost_packets[kNumAllLostPackets - 1] + kTimestampIncrement;
+    nack.UpdateLastReceivedPacket(seq_num, timestamp);
+
+    NackTracker::NackList nack_list = nack.GetNackList();
+    EXPECT_EQ(static_cast<size_t>(kNumAllLostPackets), nack_list.size());
+
+    // Pretend the first packet is decoded.
+    nack.UpdateLastDecodedPacket(first_seq_num, first_timestamp);
+    nack_list = nack.GetNackList();
+
+    NackTracker::NackList::iterator it = nack_list.begin();
+    while (it != nack_list.end()) {
+      seq_num = it->first - seq_num_offset;
+      int index = seq_num - kLostPackets[0];
+      EXPECT_EQ(timestamp_lost_packets[index], it->second.estimated_timestamp);
+      EXPECT_EQ((index + 2) * kPacketSizeMs, it->second.time_to_play_ms);
+      ++it;
+    }
+  }
+}
+
+TEST(NackTrackerTest,
+     MissingPacketsPriorToLastDecodedRtpShouldNotBeInNackList) {
+  for (int m = 0; m < 2; ++m) {
+    uint16_t seq_num_offset = (m == 0) ? 0 : 65531;  // Wrap around if `m` is 1.
+    NackTracker nack;
+    nack.UpdateSampleRate(kSampleRateHz);
+
+    // Two consecutive packets to have a correct estimate of timestamp increase.
+    uint16_t seq_num = 0;
+    nack.UpdateLastReceivedPacket(seq_num_offset + seq_num,
+                                  seq_num * kTimestampIncrement);
+    seq_num++;
+    nack.UpdateLastReceivedPacket(seq_num_offset + seq_num,
+                                  seq_num * kTimestampIncrement);
+
+    // Skip 10 packets (larger than NACK threshold).
+    const int kNumLostPackets = 10;
+    seq_num += kNumLostPackets + 1;
+    nack.UpdateLastReceivedPacket(seq_num_offset + seq_num,
+                                  seq_num * kTimestampIncrement);
+
+    const size_t kExpectedListSize = kNumLostPackets;
+    std::vector<uint16_t> nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+    EXPECT_EQ(kExpectedListSize, nack_list.size());
+
+    for (int k = 0; k < 2; ++k) {
+      // Decoding of the first and the second arrived packets.
+      for (int n = 0; n < kPacketSizeMs / 10; ++n) {
+        nack.UpdateLastDecodedPacket(seq_num_offset + k,
+                                     k * kTimestampIncrement);
+        nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+        EXPECT_EQ(kExpectedListSize, nack_list.size());
+      }
+    }
+
+    // Decoding of the last received packet.
+    nack.UpdateLastDecodedPacket(seq_num + seq_num_offset,
+                                 seq_num * kTimestampIncrement);
+    nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+    EXPECT_TRUE(nack_list.empty());
+
+    // Make sure list of late packets is also empty. To check that, push few
+    // packets, if the late list is not empty its content will pop up in NACK
+    // list.
+    for (int n = 0; n < 10; ++n) {
+      seq_num++;
+      nack.UpdateLastReceivedPacket(seq_num_offset + seq_num,
+                                    seq_num * kTimestampIncrement);
+      nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+      EXPECT_TRUE(nack_list.empty());
+    }
+  }
+}
+
+TEST(NackTrackerTest, Reset) {
+  NackTracker nack;
+  nack.UpdateSampleRate(kSampleRateHz);
+
+  // Two consecutive packets to have a correct estimate of timestamp increase.
+  uint16_t seq_num = 0;
+  nack.UpdateLastReceivedPacket(seq_num, seq_num * kTimestampIncrement);
+  seq_num++;
+  nack.UpdateLastReceivedPacket(seq_num, seq_num * kTimestampIncrement);
+
+  // Skip 10 packets (larger than NACK threshold).
+  const int kNumLostPackets = 10;
+  seq_num += kNumLostPackets + 1;
+  nack.UpdateLastReceivedPacket(seq_num, seq_num * kTimestampIncrement);
+
+  const size_t kExpectedListSize = kNumLostPackets;
+  std::vector<uint16_t> nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+  EXPECT_EQ(kExpectedListSize, nack_list.size());
+
+  nack.Reset();
+  nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+  EXPECT_TRUE(nack_list.empty());
+}
+
+TEST(NackTrackerTest, ListSizeAppliedFromBeginning) {
+  const size_t kNackListSize = 10;
+  for (int m = 0; m < 2; ++m) {
+    uint16_t seq_num_offset = (m == 0) ? 0 : 65525;  // Wrap around if `m` is 1.
+    NackTracker nack;
+    nack.UpdateSampleRate(kSampleRateHz);
+    nack.SetMaxNackListSize(kNackListSize);
+
+    uint16_t seq_num = seq_num_offset;
+    uint32_t timestamp = 0x12345678;
+    nack.UpdateLastReceivedPacket(seq_num, timestamp);
+
+    // Packet lost more than NACK-list size limit.
+    uint16_t num_lost_packets = kNackListSize + 5;
+
+    seq_num += num_lost_packets + 1;
+    timestamp += (num_lost_packets + 1) * kTimestampIncrement;
+    nack.UpdateLastReceivedPacket(seq_num, timestamp);
+
+    std::vector<uint16_t> nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+    EXPECT_EQ(kNackListSize, nack_list.size());
+  }
+}
+
+TEST(NackTrackerTest, ChangeOfListSizeAppliedAndOldElementsRemoved) {
+  const size_t kNackListSize = 10;
+  for (int m = 0; m < 2; ++m) {
+    uint16_t seq_num_offset = (m == 0) ? 0 : 65525;  // Wrap around if `m` is 1.
+    NackTracker nack;
+    nack.UpdateSampleRate(kSampleRateHz);
+
+    uint16_t seq_num = seq_num_offset;
+    uint32_t timestamp = 0x87654321;
+    nack.UpdateLastReceivedPacket(seq_num, timestamp);
+
+    // Packet lost more than NACK-list size limit.
+    uint16_t num_lost_packets = kNackListSize + 5;
+
+    std::unique_ptr<uint16_t[]> seq_num_lost(new uint16_t[num_lost_packets]);
+    for (int n = 0; n < num_lost_packets; ++n) {
+      seq_num_lost[n] = ++seq_num;
+    }
+
+    ++seq_num;
+    timestamp += (num_lost_packets + 1) * kTimestampIncrement;
+    nack.UpdateLastReceivedPacket(seq_num, timestamp);
+    size_t expected_size = num_lost_packets;
+
+    std::vector<uint16_t> nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+    EXPECT_EQ(expected_size, nack_list.size());
+
+    nack.SetMaxNackListSize(kNackListSize);
+    expected_size = kNackListSize;
+    nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+    EXPECT_TRUE(IsNackListCorrect(
+        nack_list, &seq_num_lost[num_lost_packets - kNackListSize],
+        expected_size));
+
+    // NACK list should shrink.
+    for (size_t n = 1; n < kNackListSize; ++n) {
+      ++seq_num;
+      timestamp += kTimestampIncrement;
+      nack.UpdateLastReceivedPacket(seq_num, timestamp);
+      --expected_size;
+      nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+      EXPECT_TRUE(IsNackListCorrect(
+          nack_list, &seq_num_lost[num_lost_packets - kNackListSize + n],
+          expected_size));
+    }
+
+    // After this packet, NACK list should be empty.
+    ++seq_num;
+    timestamp += kTimestampIncrement;
+    nack.UpdateLastReceivedPacket(seq_num, timestamp);
+    nack_list = nack.GetNackList(kShortRoundTripTimeMs);
+    EXPECT_TRUE(nack_list.empty());
+  }
+}
+
+TEST(NackTrackerTest, RoudTripTimeIsApplied) {
+  const int kNackListSize = 200;
+  NackTracker nack;
+  nack.UpdateSampleRate(kSampleRateHz);
+  nack.SetMaxNackListSize(kNackListSize);
+
+  uint16_t seq_num = 0;
+  uint32_t timestamp = 0x87654321;
+  nack.UpdateLastReceivedPacket(seq_num, timestamp);
+
+  // Packet lost more than NACK-list size limit.
+  uint16_t kNumLostPackets = 5;
+
+  seq_num += (1 + kNumLostPackets);
+  timestamp += (1 + kNumLostPackets) * kTimestampIncrement;
+  nack.UpdateLastReceivedPacket(seq_num, timestamp);
+
+  // Expected time-to-play are:
+  // kPacketSizeMs - 10, 2*kPacketSizeMs - 10, 3*kPacketSizeMs - 10, ...
+  //
+  // sequence number:  1,  2,  3,   4,   5
+  // time-to-play:    20, 50, 80, 110, 140
+  //
+  std::vector<uint16_t> nack_list = nack.GetNackList(100);
+  ASSERT_EQ(2u, nack_list.size());
+  EXPECT_EQ(4, nack_list[0]);
+  EXPECT_EQ(5, nack_list[1]);
+}
+
+// Set never_nack_multiple_times to true with a field trial and verify that
+// packets are not nacked multiple times.
+TEST(NackTrackerTest, DoNotNackMultipleTimes) {
+  test::ScopedFieldTrials field_trials(
+      "WebRTC-Audio-NetEqNackTrackerConfig/"
+      "packet_loss_forget_factor:0.996,ms_per_loss_percent:20,"
+      "never_nack_multiple_times:true/");
+  const int kNackListSize = 200;
+  NackTracker nack;
+  nack.UpdateSampleRate(kSampleRateHz);
+  nack.SetMaxNackListSize(kNackListSize);
+
+  uint16_t seq_num = 0;
+  uint32_t timestamp = 0x87654321;
+  nack.UpdateLastReceivedPacket(seq_num, timestamp);
+
+  uint16_t kNumLostPackets = 3;
+
+  seq_num += (1 + kNumLostPackets);
+  timestamp += (1 + kNumLostPackets) * kTimestampIncrement;
+  nack.UpdateLastReceivedPacket(seq_num, timestamp);
+
+  std::vector<uint16_t> nack_list = nack.GetNackList(10);
+  ASSERT_EQ(3u, nack_list.size());
+  EXPECT_EQ(1, nack_list[0]);
+  EXPECT_EQ(2, nack_list[1]);
+  EXPECT_EQ(3, nack_list[2]);
+  // When we get the nack list again, it should be empty.
+  std::vector<uint16_t> nack_list2 = nack.GetNackList(10);
+  EXPECT_TRUE(nack_list2.empty());
+}
+
+// Test if estimated packet loss rate is correct.
+TEST(NackTrackerTest, PacketLossRateCorrect) {
+  const int kNackListSize = 200;
+  NackTracker nack;
+  nack.UpdateSampleRate(kSampleRateHz);
+  nack.SetMaxNackListSize(kNackListSize);
+  uint16_t seq_num = 0;
+  uint32_t timestamp = 0x87654321;
+  auto add_packet = [&nack, &seq_num, &timestamp](bool received) {
+    if (received) {
+      nack.UpdateLastReceivedPacket(seq_num, timestamp);
+    }
+    seq_num++;
+    timestamp += kTimestampIncrement;
+  };
+  // Add some packets, but every fourth packet is lost.
+  for (int i = 0; i < 300; i++) {
+    add_packet(true);
+    add_packet(true);
+    add_packet(true);
+    add_packet(false);
+  }
+  // 1 << 28 is 0.25 in Q30. We expect the packet loss estimate to be within
+  // 0.01 of that.
+  EXPECT_NEAR(nack.GetPacketLossRateForTest(), 1 << 28, (1 << 30) / 100);
+}
+
+TEST(NackTrackerTest, DoNotNackAfterDtx) {
+  const int kNackListSize = 200;
+  NackTracker nack;
+  nack.UpdateSampleRate(kSampleRateHz);
+  nack.SetMaxNackListSize(kNackListSize);
+  uint16_t seq_num = 0;
+  uint32_t timestamp = 0x87654321;
+  nack.UpdateLastReceivedPacket(seq_num, timestamp);
+  EXPECT_TRUE(nack.GetNackList(0).empty());
+  constexpr int kDtxPeriod = 400;
+  nack.UpdateLastReceivedPacket(seq_num + 2,
+                                timestamp + kDtxPeriod * kSampleRateHz / 1000);
+  EXPECT_TRUE(nack.GetNackList(0).empty());
+}
+
+TEST(NackTrackerTest, DoNotNackIfLossRateIsTooHigh) {
+  test::ScopedFieldTrials field_trials(
+      "WebRTC-Audio-NetEqNackTrackerConfig/max_loss_rate:0.4/");
+  const int kNackListSize = 200;
+  NackTracker nack;
+  nack.UpdateSampleRate(kSampleRateHz);
+  nack.SetMaxNackListSize(kNackListSize);
+  uint16_t seq_num = 0;
+  uint32_t timestamp = 0x87654321;
+  auto add_packet = [&nack, &seq_num, &timestamp](bool received) {
+    if (received) {
+      nack.UpdateLastReceivedPacket(seq_num, timestamp);
+    }
+    seq_num++;
+    timestamp += kTimestampIncrement;
+  };
+  for (int i = 0; i < 500; i++) {
+    add_packet(true);
+    add_packet(false);
+  }
+  // Expect 50% loss rate which is higher that the configured maximum 40%.
+  EXPECT_NEAR(nack.GetPacketLossRateForTest(), 1 << 29, (1 << 30) / 100);
+  EXPECT_TRUE(nack.GetNackList(0).empty());
+}
+
+TEST(NackTrackerTest, OnlyNackIfRttIsValid) {
+  test::ScopedFieldTrials field_trials(
+      "WebRTC-Audio-NetEqNackTrackerConfig/require_valid_rtt:true/");
+  const int kNackListSize = 200;
+  NackTracker nack;
+  nack.UpdateSampleRate(kSampleRateHz);
+  nack.SetMaxNackListSize(kNackListSize);
+  uint16_t seq_num = 0;
+  uint32_t timestamp = 0x87654321;
+  auto add_packet = [&nack, &seq_num, &timestamp](bool received) {
+    if (received) {
+      nack.UpdateLastReceivedPacket(seq_num, timestamp);
+    }
+    seq_num++;
+    timestamp += kTimestampIncrement;
+  };
+  add_packet(true);
+  add_packet(false);
+  add_packet(true);
+  EXPECT_TRUE(nack.GetNackList(0).empty());
+  EXPECT_FALSE(nack.GetNackList(10).empty());
+}
+
+}  // namespace webrtc