modules/rtp_rtcp/source/rtp_fec_unittest.cc

/*
 *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include <list>
#include <memory>

#include "absl/algorithm/container.h"
#include "modules/rtp_rtcp/source/byte_io.h"
#include "modules/rtp_rtcp/source/fec_test_helper.h"
#include "modules/rtp_rtcp/source/flexfec_03_header_reader_writer.h"
#include "modules/rtp_rtcp/source/forward_error_correction.h"
#include "modules/rtp_rtcp/source/ulpfec_header_reader_writer.h"
#include "rtc_base/random.h"
#include "test/gtest.h"

namespace webrtc {

namespace {

// Transport header size in bytes. Assume UDP/IPv4 as a reasonable minimum.
constexpr size_t kTransportOverhead = 28;

constexpr uint32_t kMediaSsrc = 83542;
constexpr uint32_t kFlexfecSsrc = 43245;

constexpr size_t kMaxMediaPackets = 48;

// Deep copies `src` to `dst`, but only keeps every Nth packet.
void DeepCopyEveryNthPacket(const ForwardErrorCorrection::PacketList& src,
                            int n,
                            ForwardErrorCorrection::PacketList* dst) {
  RTC_DCHECK_GT(n, 0);
  int i = 0;
  for (const auto& packet : src) {
    if (i % n == 0) {
      dst->emplace_back(new ForwardErrorCorrection::Packet(*packet));
    }
    ++i;
  }
}

}  // namespace

using ::testing::Types;

template <typename ForwardErrorCorrectionType>
class RtpFecTest : public ::testing::Test {
 protected:
  RtpFecTest()
      : random_(0xabcdef123456),
        media_packet_generator_(
            kRtpHeaderSize,  // Minimum packet size.
            IP_PACKET_SIZE - kRtpHeaderSize - kTransportOverhead -
                fec_.MaxPacketOverhead(),  // Maximum packet size.
            kMediaSsrc,
            &random_) {}

  // Construct `received_packets_`: a subset of the media and FEC packets.
  //
  // Media packet "i" is lost if media_loss_mask_[i] = 1, received if
  // media_loss_mask_[i] = 0.
  // FEC packet "i" is lost if fec_loss_mask_[i] = 1, received if
  // fec_loss_mask_[i] = 0.
  void NetworkReceivedPackets(int* media_loss_mask, int* fec_loss_mask);

  // Add packet from `packet_list` to list of received packets, using the
  // `loss_mask`.
  // The `packet_list` may be a media packet list (is_fec = false), or a
  // FEC packet list (is_fec = true).
  template <typename T>
  void ReceivedPackets(const T& packet_list, int* loss_mask, bool is_fec);

  // Check for complete recovery after FEC decoding.
  bool IsRecoveryComplete();

  ForwardErrorCorrectionType fec_;

  Random random_;
  test::fec::MediaPacketGenerator media_packet_generator_;

  ForwardErrorCorrection::PacketList media_packets_;
  std::list<ForwardErrorCorrection::Packet*> generated_fec_packets_;
  std::vector<std::unique_ptr<ForwardErrorCorrection::ReceivedPacket>>
      received_packets_;
  ForwardErrorCorrection::RecoveredPacketList recovered_packets_;

  int media_loss_mask_[kUlpfecMaxMediaPackets];
  int fec_loss_mask_[kUlpfecMaxMediaPackets];
};

template <typename ForwardErrorCorrectionType>
void RtpFecTest<ForwardErrorCorrectionType>::NetworkReceivedPackets(
    int* media_loss_mask,
    int* fec_loss_mask) {
  constexpr bool kFecPacket = true;
  this->received_packets_.clear();
  ReceivedPackets(media_packets_, media_loss_mask, !kFecPacket);
  ReceivedPackets(generated_fec_packets_, fec_loss_mask, kFecPacket);
}

template <typename ForwardErrorCorrectionType>
template <typename PacketListType>
void RtpFecTest<ForwardErrorCorrectionType>::ReceivedPackets(
    const PacketListType& packet_list,
    int* loss_mask,
    bool is_fec) {
  uint16_t fec_seq_num = ForwardErrorCorrectionType::GetFirstFecSeqNum(
      media_packet_generator_.GetNextSeqNum());
  int packet_idx = 0;

  for (const auto& packet : packet_list) {
    if (loss_mask[packet_idx] == 0) {
      std::unique_ptr<ForwardErrorCorrection::ReceivedPacket> received_packet(
          new ForwardErrorCorrection::ReceivedPacket());
      received_packet->pkt = new ForwardErrorCorrection::Packet();
      received_packet->pkt->data = packet->data;
      received_packet->is_fec = is_fec;
      if (!is_fec) {
        received_packet->ssrc = kMediaSsrc;
        // For media packets, the sequence number is obtained from the
        // RTP header as written by MediaPacketGenerator::ConstructMediaPackets.
        received_packet->seq_num =
            ByteReader<uint16_t>::ReadBigEndian(packet->data.data() + 2);
      } else {
        received_packet->ssrc = ForwardErrorCorrectionType::kFecSsrc;
        // For FEC packets, we simulate the sequence numbers differently
        // depending on if ULPFEC or FlexFEC is used. See the definition of
        // ForwardErrorCorrectionType::GetFirstFecSeqNum.
        received_packet->seq_num = fec_seq_num;
      }
      received_packets_.push_back(std::move(received_packet));
    }
    packet_idx++;
    // Sequence number of FEC packets are defined as increment by 1 from
    // last media packet in frame.
    if (is_fec)
      fec_seq_num++;
  }
}

template <typename ForwardErrorCorrectionType>
bool RtpFecTest<ForwardErrorCorrectionType>::IsRecoveryComplete() {
  // We must have equally many recovered packets as original packets and all
  // recovered packets must be identical to the corresponding original packets.
  return absl::c_equal(
      media_packets_, recovered_packets_,
      [](const std::unique_ptr<ForwardErrorCorrection::Packet>& media_packet,
         const std::unique_ptr<ForwardErrorCorrection::RecoveredPacket>&
             recovered_packet) {
        if (media_packet->data.size() != recovered_packet->pkt->data.size()) {
          return false;
        }
        if (memcmp(media_packet->data.cdata(),
                   recovered_packet->pkt->data.cdata(),
                   media_packet->data.size()) != 0) {
          return false;
        }
        return true;
      });
}

// Define gTest typed test to loop over both ULPFEC and FlexFEC.
// Since the tests now are parameterized, we need to access
// member variables using `this`, thereby enforcing runtime
// resolution.

class FlexfecForwardErrorCorrection : public ForwardErrorCorrection {
 public:
  static constexpr uint32_t kFecSsrc = kFlexfecSsrc;

  FlexfecForwardErrorCorrection()
      : ForwardErrorCorrection(
            std::unique_ptr<FecHeaderReader>(new Flexfec03HeaderReader()),
            std::unique_ptr<FecHeaderWriter>(new Flexfec03HeaderWriter()),
            kFecSsrc,
            kMediaSsrc) {}

  // For FlexFEC we let the FEC packet sequence numbers be independent of
  // the media packet sequence numbers.
  static uint16_t GetFirstFecSeqNum(uint16_t next_media_seq_num) {
    Random random(0xbe110);
    return random.Rand<uint16_t>();
  }
};

class UlpfecForwardErrorCorrection : public ForwardErrorCorrection {
 public:
  static constexpr uint32_t kFecSsrc = kMediaSsrc;

  UlpfecForwardErrorCorrection()
      : ForwardErrorCorrection(
            std::unique_ptr<FecHeaderReader>(new UlpfecHeaderReader()),
            std::unique_ptr<FecHeaderWriter>(new UlpfecHeaderWriter()),
            kFecSsrc,
            kMediaSsrc) {}

  // For ULPFEC we assume that the FEC packets are subsequent to the media
  // packets in terms of sequence number.
  static uint16_t GetFirstFecSeqNum(uint16_t next_media_seq_num) {
    return next_media_seq_num;
  }
};

using FecTypes =
    Types<FlexfecForwardErrorCorrection, UlpfecForwardErrorCorrection>;
TYPED_TEST_SUITE(RtpFecTest, FecTypes);

TYPED_TEST(RtpFecTest, WillProtectMediaPacketsWithLargeSequenceNumberGap) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr int kNumMediaPackets = 2;
  constexpr uint8_t kProtectionFactor = 127;

  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(kNumMediaPackets);

  // Create |kMaxMediaPackets - 1| sequence number difference.
  ByteWriter<uint16_t>::WriteBigEndian(
      this->media_packets_.front()->data.MutableData() + 2, 1);
  ByteWriter<uint16_t>::WriteBigEndian(
      this->media_packets_.back()->data.MutableData() + 2, kMaxMediaPackets);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));
  EXPECT_EQ(1u, this->generated_fec_packets_.size());
}

TYPED_TEST(RtpFecTest,
           WillNotProtectMediaPacketsWithTooLargeSequenceNumberGap) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr int kNumMediaPackets = 2;
  constexpr uint8_t kProtectionFactor = 127;

  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(kNumMediaPackets);

  // Create `kMaxMediaPackets` sequence number difference.
  ByteWriter<uint16_t>::WriteBigEndian(
      this->media_packets_.front()->data.MutableData() + 2, 1);
  ByteWriter<uint16_t>::WriteBigEndian(
      this->media_packets_.back()->data.MutableData() + 2,
      kMaxMediaPackets + 1);

  EXPECT_EQ(
      -1, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                               kNumImportantPackets, kUseUnequalProtection,
                               kFecMaskBursty, &this->generated_fec_packets_));
  EXPECT_TRUE(this->generated_fec_packets_.empty());
}

TYPED_TEST(RtpFecTest, FecRecoveryNoLoss) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr int kNumMediaPackets = 4;
  constexpr uint8_t kProtectionFactor = 60;

  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(kNumMediaPackets);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));

  // Expect 1 FEC packet.
  EXPECT_EQ(1u, this->generated_fec_packets_.size());

  // No packets lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // No packets lost, expect complete recovery.
  EXPECT_TRUE(this->IsRecoveryComplete());
}

TYPED_TEST(RtpFecTest, FecRecoveryWithLoss) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr int kNumMediaPackets = 4;
  constexpr uint8_t kProtectionFactor = 60;

  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(kNumMediaPackets);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));

  // Expect 1 FEC packet.
  EXPECT_EQ(1u, this->generated_fec_packets_.size());

  // 1 media packet lost
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[3] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // One packet lost, one FEC packet, expect complete recovery.
  EXPECT_TRUE(this->IsRecoveryComplete());
  this->recovered_packets_.clear();

  // 2 media packets lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[1] = 1;
  this->media_loss_mask_[3] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // 2 packets lost, one FEC packet, cannot get complete recovery.
  EXPECT_FALSE(this->IsRecoveryComplete());
}

// Verify that we don't use an old FEC packet for FEC decoding.
TYPED_TEST(RtpFecTest, NoFecRecoveryWithOldFecPacket) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr uint8_t kProtectionFactor = 20;

  // Two frames: first frame (old) with two media packets and 1 FEC packet.
  // Third frame (new) with 3 media packets, and no FEC packets.
  //
  //  #0(media) #1(media) #2(FEC)              ----Frame 1-----
  //  #32767(media) 32768(media) 32769(media)  ----Frame 2-----
  //  #65535(media) #0(media) #1(media).       ----Frame 3-----
  // If we lose either packet 0 or 1 of third frame, FEC decoding should not
  // try to decode using "old" FEC packet #2.

  // Construct media packets for first frame, starting at sequence number 0.
  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(2, 0);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));
  // Expect 1 FEC packet.
  EXPECT_EQ(1u, this->generated_fec_packets_.size());
  // Add FEC packet (seq#2) of this first frame to received list (i.e., assume
  // the two media packet were lost).
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->ReceivedPackets(this->generated_fec_packets_, this->fec_loss_mask_,
                        true);

  // Construct media packets for second frame, with sequence number wrap.
  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(3, 32767);

  // Expect 3 media packets for this frame.
  EXPECT_EQ(3u, this->media_packets_.size());

  // No packets lost
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  this->ReceivedPackets(this->media_packets_, this->media_loss_mask_, false);

  // Construct media packets for third frame, with sequence number wrap.
  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(3, 65535);

  // Expect 3 media packets for this frame.
  EXPECT_EQ(3u, this->media_packets_.size());

  // Second media packet lost (seq#0).
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  this->media_loss_mask_[1] = 1;
  // Add packets #65535, and #1 to received list.
  this->ReceivedPackets(this->media_packets_, this->media_loss_mask_, false);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // Expect that no decoding is done to get missing packet (seq#0) of third
  // frame, using old FEC packet (seq#2) from first (old) frame. So number of
  // recovered packets is 5 (0 from first frame, three from second frame, and 2
  // for the third frame, with no packets recovered via FEC).
  EXPECT_EQ(5u, this->recovered_packets_.size());
  EXPECT_TRUE(this->recovered_packets_.size() != this->media_packets_.size());
}

// Verify we can still recover frame if sequence number wrap occurs within
// the frame and FEC packet following wrap is received after media packets.
TYPED_TEST(RtpFecTest, FecRecoveryWithSeqNumGapOneFrameRecovery) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr uint8_t kProtectionFactor = 20;

  // One frame, with sequence number wrap in media packets.
  //         -----Frame 1----
  //  #65534(media) #65535(media) #0(media) #1(FEC).
  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(3, 65534);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));

  // Expect 1 FEC packet.
  EXPECT_EQ(1u, this->generated_fec_packets_.size());

  // Lose one media packet (seq# 65535).
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[1] = 1;
  this->ReceivedPackets(this->media_packets_, this->media_loss_mask_, false);
  // Add FEC packet to received list following the media packets.
  this->ReceivedPackets(this->generated_fec_packets_, this->fec_loss_mask_,
                        true);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // Expect 3 media packets in recovered list, and complete recovery.
  // Wrap-around won't remove FEC packet, as it follows the wrap.
  EXPECT_EQ(3u, this->recovered_packets_.size());
  EXPECT_TRUE(this->IsRecoveryComplete());
}

// Sequence number wrap occurs within the ULPFEC packets for the frame.
// Same problem will occur if wrap is within media packets but ULPFEC packet is
// received before the media packets. This may be improved if timing information
// is used to detect old ULPFEC packets.

// TODO(nisse): There's some logic to discard ULPFEC packets at wrap-around,
// however, that is not actually exercised by this test: When the first FEC
// packet is processed, it results in full recovery of one media packet and the
// FEC packet is forgotten. And then the wraparound isn't noticed when the next
// FEC packet is received. We should fix wraparound handling, which currently
// appears broken, and then figure out how to test it properly.
using RtpFecTestUlpfecOnly = RtpFecTest<UlpfecForwardErrorCorrection>;
TEST_F(RtpFecTestUlpfecOnly, FecRecoveryWithSeqNumGapOneFrameRecovery) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr uint8_t kProtectionFactor = 200;

  // 1 frame: 3 media packets and 2 FEC packets.
  // Sequence number wrap in FEC packets.
  //           -----Frame 1----
  // #65532(media) #65533(media) #65534(media) #65535(FEC) #0(FEC).
  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(3, 65532);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));

  // Expect 2 FEC packets.
  EXPECT_EQ(2u, this->generated_fec_packets_.size());

  // Lose the last two media packets (seq# 65533, 65534).
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[1] = 1;
  this->media_loss_mask_[2] = 1;
  this->ReceivedPackets(this->media_packets_, this->media_loss_mask_, false);
  this->ReceivedPackets(this->generated_fec_packets_, this->fec_loss_mask_,
                        true);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // The two FEC packets are received and should allow for complete recovery,
  // but because of the wrap the first FEC packet will be discarded, and only
  // one media packet is recoverable. So expect 2 media packets on recovered
  // list and no complete recovery.
  EXPECT_EQ(3u, this->recovered_packets_.size());
  EXPECT_EQ(this->recovered_packets_.size(), this->media_packets_.size());
  EXPECT_TRUE(this->IsRecoveryComplete());
}

// TODO(brandtr): This test mimics the one above, ensuring that the recovery
// strategy of FlexFEC matches the recovery strategy of ULPFEC. Since FlexFEC
// does not share the sequence number space with the media, however, having a
// matching recovery strategy may be suboptimal. Study this further.
// TODO(nisse): In this test, recovery based on the first FEC packet fails with
// the log message "The recovered packet had a length larger than a typical IP
// packet, and is thus dropped." This is probably not intended, and needs
// investigation.
using RtpFecTestFlexfecOnly = RtpFecTest<FlexfecForwardErrorCorrection>;
TEST_F(RtpFecTestFlexfecOnly, FecRecoveryWithSeqNumGapOneFrameNoRecovery) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr uint8_t kProtectionFactor = 200;

  // 1 frame: 3 media packets and 2 FEC packets.
  // Sequence number wrap in FEC packets.
  //           -----Frame 1----
  // #65532(media) #65533(media) #65534(media) #65535(FEC) #0(FEC).
  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(3, 65532);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));

  // Expect 2 FEC packets.
  EXPECT_EQ(2u, this->generated_fec_packets_.size());

  // Overwrite the sequence numbers generated by ConstructMediaPackets,
  // to make sure that we do have a wrap.
  auto it = this->generated_fec_packets_.begin();
  ByteWriter<uint16_t>::WriteBigEndian(&(*it)->data.MutableData()[2], 65535);
  ++it;
  ByteWriter<uint16_t>::WriteBigEndian(&(*it)->data.MutableData()[2], 0);

  // Lose the last two media packets (seq# 65533, 65534).
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[1] = 1;
  this->media_loss_mask_[2] = 1;
  this->ReceivedPackets(this->media_packets_, this->media_loss_mask_, false);
  this->ReceivedPackets(this->generated_fec_packets_, this->fec_loss_mask_,
                        true);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // The two FEC packets are received and should allow for complete recovery,
  // but because of the wrap the first FEC packet will be discarded, and only
  // one media packet is recoverable. So expect 2 media packets on recovered
  // list and no complete recovery.
  EXPECT_EQ(2u, this->recovered_packets_.size());
  EXPECT_TRUE(this->recovered_packets_.size() != this->media_packets_.size());
  EXPECT_FALSE(this->IsRecoveryComplete());
}

// Verify we can still recover frame if media packets are reordered.
TYPED_TEST(RtpFecTest, FecRecoveryWithMediaOutOfOrder) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr uint8_t kProtectionFactor = 20;

  // One frame: 3 media packets, 1 FEC packet.
  //         -----Frame 1----
  //  #0(media) #1(media) #2(media) #3(FEC).
  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(3, 0);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));

  // Expect 1 FEC packet.
  EXPECT_EQ(1u, this->generated_fec_packets_.size());

  // Lose one media packet (seq# 1).
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[1] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  // Reorder received media packets.
  auto it0 = this->received_packets_.begin();
  auto it1 = this->received_packets_.begin();
  it1++;
  std::swap(*it0, *it1);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // Expect 3 media packets in recovered list, and complete recovery.
  EXPECT_EQ(3u, this->recovered_packets_.size());
  EXPECT_TRUE(this->IsRecoveryComplete());
}

// Verify we can still recover frame if FEC is received before media packets.
TYPED_TEST(RtpFecTest, FecRecoveryWithFecOutOfOrder) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr uint8_t kProtectionFactor = 20;

  // One frame: 3 media packets, 1 FEC packet.
  //         -----Frame 1----
  //  #0(media) #1(media) #2(media) #3(FEC).
  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(3, 0);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));

  // Expect 1 FEC packet.
  EXPECT_EQ(1u, this->generated_fec_packets_.size());

  // Lose one media packet (seq# 1).
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[1] = 1;
  // Add FEC packet to received list before the media packets.
  this->ReceivedPackets(this->generated_fec_packets_, this->fec_loss_mask_,
                        true);
  // Add media packets to received list.
  this->ReceivedPackets(this->media_packets_, this->media_loss_mask_, false);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // Expect 3 media packets in recovered list, and complete recovery.
  EXPECT_EQ(3u, this->recovered_packets_.size());
  EXPECT_TRUE(this->IsRecoveryComplete());
}

// Test 50% protection with random mask type: Two cases are considered:
// a 50% non-consecutive loss which can be fully recovered, and a 50%
// consecutive loss which cannot be fully recovered.
TYPED_TEST(RtpFecTest, FecRecoveryWithLoss50percRandomMask) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr int kNumMediaPackets = 4;
  constexpr uint8_t kProtectionFactor = 255;

  // Packet Mask for (4,4,0) code, from random mask table.
  // (kNumMediaPackets = 4; num_fec_packets = 4, kNumImportantPackets = 0)

  //         media#0   media#1  media#2    media#3
  // fec#0:    1          1        0          0
  // fec#1:    1          0        1          0
  // fec#2:    0          0        1          1
  // fec#3:    0          1        0          1
  //

  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(kNumMediaPackets);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskRandom, &this->generated_fec_packets_));

  // Expect 4 FEC packets.
  EXPECT_EQ(4u, this->generated_fec_packets_.size());

  // 4 packets lost: 3 media packets (0, 2, 3), and one FEC packet (0) lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->fec_loss_mask_[0] = 1;
  this->media_loss_mask_[0] = 1;
  this->media_loss_mask_[2] = 1;
  this->media_loss_mask_[3] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // With media packet#1 and FEC packets #1, #2, #3, expect complete recovery.
  EXPECT_TRUE(this->IsRecoveryComplete());
  this->recovered_packets_.clear();

  // 4 consecutive packets lost: media packets 0, 1, 2, 3.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[0] = 1;
  this->media_loss_mask_[1] = 1;
  this->media_loss_mask_[2] = 1;
  this->media_loss_mask_[3] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // Cannot get complete recovery for this loss configuration with random mask.
  EXPECT_FALSE(this->IsRecoveryComplete());
}

// Test 50% protection with bursty type: Three cases are considered:
// two 50% consecutive losses which can be fully recovered, and one
// non-consecutive which cannot be fully recovered.
TYPED_TEST(RtpFecTest, FecRecoveryWithLoss50percBurstyMask) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr int kNumMediaPackets = 4;
  constexpr uint8_t kProtectionFactor = 255;

  // Packet Mask for (4,4,0) code, from bursty mask table.
  // (kNumMediaPackets = 4; num_fec_packets = 4, kNumImportantPackets = 0)

  //         media#0   media#1  media#2    media#3
  // fec#0:    1          0        0          0
  // fec#1:    1          1        0          0
  // fec#2:    0          1        1          0
  // fec#3:    0          0        1          1
  //

  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(kNumMediaPackets);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));

  // Expect 4 FEC packets.
  EXPECT_EQ(4u, this->generated_fec_packets_.size());

  // 4 consecutive packets lost: media packets 0,1,2,3.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[0] = 1;
  this->media_loss_mask_[1] = 1;
  this->media_loss_mask_[2] = 1;
  this->media_loss_mask_[3] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // Expect complete recovery for consecutive packet loss <= 50%.
  EXPECT_TRUE(this->IsRecoveryComplete());
  this->recovered_packets_.clear();

  // 4 consecutive packets lost: media packets 1,2, 3, and FEC packet 0.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->fec_loss_mask_[0] = 1;
  this->media_loss_mask_[1] = 1;
  this->media_loss_mask_[2] = 1;
  this->media_loss_mask_[3] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // Expect complete recovery for consecutive packet loss <= 50%.
  EXPECT_TRUE(this->IsRecoveryComplete());
  this->recovered_packets_.clear();

  // 4 packets lost (non-consecutive loss): media packets 0, 3, and FEC# 0, 3.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->fec_loss_mask_[0] = 1;
  this->fec_loss_mask_[3] = 1;
  this->media_loss_mask_[0] = 1;
  this->media_loss_mask_[3] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // Cannot get complete recovery for this loss configuration.
  EXPECT_FALSE(this->IsRecoveryComplete());
}

TYPED_TEST(RtpFecTest, FecRecoveryNoLossUep) {
  constexpr int kNumImportantPackets = 2;
  constexpr bool kUseUnequalProtection = true;
  constexpr int kNumMediaPackets = 4;
  constexpr uint8_t kProtectionFactor = 60;

  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(kNumMediaPackets);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));

  // Expect 1 FEC packet.
  EXPECT_EQ(1u, this->generated_fec_packets_.size());

  // No packets lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // No packets lost, expect complete recovery.
  EXPECT_TRUE(this->IsRecoveryComplete());
}

TYPED_TEST(RtpFecTest, FecRecoveryWithLossUep) {
  constexpr int kNumImportantPackets = 2;
  constexpr bool kUseUnequalProtection = true;
  constexpr int kNumMediaPackets = 4;
  constexpr uint8_t kProtectionFactor = 60;

  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(kNumMediaPackets);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));

  // Expect 1 FEC packet.
  EXPECT_EQ(1u, this->generated_fec_packets_.size());

  // 1 media packet lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[3] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // One packet lost, one FEC packet, expect complete recovery.
  EXPECT_TRUE(this->IsRecoveryComplete());
  this->recovered_packets_.clear();

  // 2 media packets lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[1] = 1;
  this->media_loss_mask_[3] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // 2 packets lost, one FEC packet, cannot get complete recovery.
  EXPECT_FALSE(this->IsRecoveryComplete());
}

// Test 50% protection with random mask type for UEP on.
TYPED_TEST(RtpFecTest, FecRecoveryWithLoss50percUepRandomMask) {
  constexpr int kNumImportantPackets = 1;
  constexpr bool kUseUnequalProtection = true;
  constexpr int kNumMediaPackets = 4;
  constexpr uint8_t kProtectionFactor = 255;

  // Packet Mask for (4,4,1) code, from random mask table.
  // (kNumMediaPackets = 4; num_fec_packets = 4, kNumImportantPackets = 1)

  //         media#0   media#1  media#2    media#3
  // fec#0:    1          0        0          0
  // fec#1:    1          1        0          0
  // fec#2:    1          0        1          1
  // fec#3:    0          1        1          0
  //

  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(kNumMediaPackets);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(this->media_packets_, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskRandom, &this->generated_fec_packets_));

  // Expect 4 FEC packets.
  EXPECT_EQ(4u, this->generated_fec_packets_.size());

  // 4 packets lost: 3 media packets and FEC packet#1 lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->fec_loss_mask_[1] = 1;
  this->media_loss_mask_[0] = 1;
  this->media_loss_mask_[2] = 1;
  this->media_loss_mask_[3] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // With media packet#3 and FEC packets #0, #1, #3, expect complete recovery.
  EXPECT_TRUE(this->IsRecoveryComplete());
  this->recovered_packets_.clear();

  // 5 packets lost: 4 media packets and one FEC packet#2 lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->fec_loss_mask_[2] = 1;
  this->media_loss_mask_[0] = 1;
  this->media_loss_mask_[1] = 1;
  this->media_loss_mask_[2] = 1;
  this->media_loss_mask_[3] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // Cannot get complete recovery for this loss configuration.
  EXPECT_FALSE(this->IsRecoveryComplete());
}

TYPED_TEST(RtpFecTest, FecRecoveryNonConsecutivePackets) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr int kNumMediaPackets = 5;
  constexpr uint8_t kProtectionFactor = 60;

  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(kNumMediaPackets);

  // Create a new temporary packet list for generating FEC packets.
  // This list should have every other packet removed.
  ForwardErrorCorrection::PacketList protected_media_packets;
  DeepCopyEveryNthPacket(this->media_packets_, 2, &protected_media_packets);

  EXPECT_EQ(
      0, this->fec_.EncodeFec(protected_media_packets, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));

  // Expect 1 FEC packet.
  EXPECT_EQ(1u, this->generated_fec_packets_.size());

  // 1 protected media packet lost
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[2] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // One packet lost, one FEC packet, expect complete recovery.
  EXPECT_TRUE(this->IsRecoveryComplete());
  this->recovered_packets_.clear();

  // Unprotected packet lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[1] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // Unprotected packet lost. Recovery not possible.
  EXPECT_FALSE(this->IsRecoveryComplete());
  this->recovered_packets_.clear();

  // 2 media packets lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[0] = 1;
  this->media_loss_mask_[2] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // 2 protected packets lost, one FEC packet, cannot get complete recovery.
  EXPECT_FALSE(this->IsRecoveryComplete());
}

TYPED_TEST(RtpFecTest, FecRecoveryNonConsecutivePacketsExtension) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr int kNumMediaPackets = 21;
  uint8_t kProtectionFactor = 127;

  this->media_packets_ =
      this->media_packet_generator_.ConstructMediaPackets(kNumMediaPackets);

  // Create a new temporary packet list for generating FEC packets.
  // This list should have every other packet removed.
  ForwardErrorCorrection::PacketList protected_media_packets;
  DeepCopyEveryNthPacket(this->media_packets_, 2, &protected_media_packets);

  // Zero column insertion will have to extend the size of the packet
  // mask since the number of actual packets are 21, while the number
  // of protected packets are 11.
  EXPECT_EQ(
      0, this->fec_.EncodeFec(protected_media_packets, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));

  // Expect 5 FEC packet.
  EXPECT_EQ(5u, this->generated_fec_packets_.size());

  // Last protected media packet lost
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[kNumMediaPackets - 1] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // One packet lost, one FEC packet, expect complete recovery.
  EXPECT_TRUE(this->IsRecoveryComplete());
  this->recovered_packets_.clear();

  // Last unprotected packet lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[kNumMediaPackets - 2] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // Unprotected packet lost. Recovery not possible.
  EXPECT_FALSE(this->IsRecoveryComplete());
  this->recovered_packets_.clear();

  // 6 media packets lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[kNumMediaPackets - 11] = 1;
  this->media_loss_mask_[kNumMediaPackets - 9] = 1;
  this->media_loss_mask_[kNumMediaPackets - 7] = 1;
  this->media_loss_mask_[kNumMediaPackets - 5] = 1;
  this->media_loss_mask_[kNumMediaPackets - 3] = 1;
  this->media_loss_mask_[kNumMediaPackets - 1] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // 5 protected packets lost, one FEC packet, cannot get complete recovery.
  EXPECT_FALSE(this->IsRecoveryComplete());
}

TYPED_TEST(RtpFecTest, FecRecoveryNonConsecutivePacketsWrap) {
  constexpr int kNumImportantPackets = 0;
  constexpr bool kUseUnequalProtection = false;
  constexpr int kNumMediaPackets = 21;
  uint8_t kProtectionFactor = 127;

  this->media_packets_ = this->media_packet_generator_.ConstructMediaPackets(
      kNumMediaPackets, 0xFFFF - 5);

  // Create a new temporary packet list for generating FEC packets.
  // This list should have every other packet removed.
  ForwardErrorCorrection::PacketList protected_media_packets;
  DeepCopyEveryNthPacket(this->media_packets_, 2, &protected_media_packets);

  // Zero column insertion will have to extend the size of the packet
  // mask since the number of actual packets are 21, while the number
  // of protected packets are 11.
  EXPECT_EQ(
      0, this->fec_.EncodeFec(protected_media_packets, kProtectionFactor,
                              kNumImportantPackets, kUseUnequalProtection,
                              kFecMaskBursty, &this->generated_fec_packets_));

  // Expect 5 FEC packet.
  EXPECT_EQ(5u, this->generated_fec_packets_.size());

  // Last protected media packet lost
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[kNumMediaPackets - 1] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // One packet lost, one FEC packet, expect complete recovery.
  EXPECT_TRUE(this->IsRecoveryComplete());
  this->recovered_packets_.clear();

  // Last unprotected packet lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[kNumMediaPackets - 2] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // Unprotected packet lost. Recovery not possible.
  EXPECT_FALSE(this->IsRecoveryComplete());
  this->recovered_packets_.clear();

  // 6 media packets lost.
  memset(this->media_loss_mask_, 0, sizeof(this->media_loss_mask_));
  memset(this->fec_loss_mask_, 0, sizeof(this->fec_loss_mask_));
  this->media_loss_mask_[kNumMediaPackets - 11] = 1;
  this->media_loss_mask_[kNumMediaPackets - 9] = 1;
  this->media_loss_mask_[kNumMediaPackets - 7] = 1;
  this->media_loss_mask_[kNumMediaPackets - 5] = 1;
  this->media_loss_mask_[kNumMediaPackets - 3] = 1;
  this->media_loss_mask_[kNumMediaPackets - 1] = 1;
  this->NetworkReceivedPackets(this->media_loss_mask_, this->fec_loss_mask_);

  for (const auto& received_packet : this->received_packets_) {
    this->fec_.DecodeFec(*received_packet, &this->recovered_packets_);
  }

  // 5 protected packets lost, one FEC packet, cannot get complete recovery.
  EXPECT_FALSE(this->IsRecoveryComplete());
}

}  // namespace webrtc