Unit test for media packet reordering in ForwardErrorCorrection.

webrtc/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 <algorithm>
 #include <list>
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "webrtc/base/random.h"
 #include "webrtc/modules/rtp_rtcp/source/byte_io.h"
 #include "webrtc/modules/rtp_rtcp/source/forward_error_correction.h"
 
 using webrtc::ForwardErrorCorrection;
 
 // Minimum RTP header size in bytes.
-const uint8_t kRtpHeaderSize = 12;
+constexpr uint8_t kRtpHeaderSize = 12;
 
 // Transport header size in bytes. Assume UDP/IPv4 as a reasonable minimum.
-const uint8_t kTransportOverhead = 28;
+constexpr uint8_t kTransportOverhead = 28;
 
 // Maximum number of media packets used in the FEC (RFC 5109).
-const uint8_t kMaxNumberMediaPackets = ForwardErrorCorrection::kMaxMediaPackets;
+constexpr uint8_t kMaxNumberMediaPackets =
+    ForwardErrorCorrection::kMaxMediaPackets;
 
 using PacketList = ForwardErrorCorrection::PacketList;
 using ReceivedPacketList = ForwardErrorCorrection::ReceivedPacketList;
 using RecoveredPacketList = ForwardErrorCorrection::RecoveredPacketList;
 
 class RtpFecTest : public ::testing::Test {
  protected:
   RtpFecTest()
       : random_(0xfec133700742),
         fec_(new ForwardErrorCorrection()),
@@ skipping 38 matching lines @@
   void ReceivedPackets(const T& packet_list, int* loss_mask, bool is_fec);
 
   // Check for complete recovery after FEC decoding.
   bool IsRecoveryComplete();
 
   // Delete the media and FEC packets.
   void TearDown();
 };
 
 TEST_F(RtpFecTest, FecRecoveryNoLoss) {
-  const int kNumImportantPackets = 0;
-  const bool kUseUnequalProtection = false;
-  const int kNumMediaPackets = 4;
-  uint8_t kProtectionFactor = 60;
+  constexpr int kNumImportantPackets = 0;
+  constexpr bool kUseUnequalProtection = false;
+  constexpr int kNumMediaPackets = 4;
+  constexpr uint8_t kProtectionFactor = 60;
 
   fec_seq_num_ = ConstructMediaPackets(kNumMediaPackets);
 
   EXPECT_EQ(0, fec_->GenerateFec(media_packet_list_, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskBursty, &fec_packet_list_));
 
   // Expect 1 FEC packet.
-  EXPECT_EQ(1, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(1u, fec_packet_list_.size());
 
   // No packets lost.
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   NetworkReceivedPackets();
 
   EXPECT_EQ(0, fec_->DecodeFec(&received_packet_list_,
                                &recovered_packet_list_));
 
   // No packets lost, expect complete recovery.
   EXPECT_TRUE(IsRecoveryComplete());
 }
 
 TEST_F(RtpFecTest, FecRecoveryWithLoss) {
-  const int kNumImportantPackets = 0;
-  const bool kUseUnequalProtection = false;
-  const int kNumMediaPackets = 4;
-  uint8_t kProtectionFactor = 60;
+  constexpr int kNumImportantPackets = 0;
+  constexpr bool kUseUnequalProtection = false;
+  constexpr int kNumMediaPackets = 4;
+  constexpr uint8_t kProtectionFactor = 60;
 
   fec_seq_num_ = ConstructMediaPackets(kNumMediaPackets);
 
   EXPECT_EQ(0, fec_->GenerateFec(media_packet_list_, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskBursty, &fec_packet_list_));
 
   // Expect 1 FEC packet.
-  EXPECT_EQ(1, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(1u, fec_packet_list_.size());
 
   // 1 media packet lost
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   media_loss_mask_[3] = 1;
   NetworkReceivedPackets();
 
   EXPECT_EQ(0,
             fec_->DecodeFec(&received_packet_list_, &recovered_packet_list_));
 
@@ skipping 10 matching lines @@
 
   EXPECT_EQ(0, fec_->DecodeFec(&received_packet_list_,
                                &recovered_packet_list_));
 
   // 2 packets lost, one FEC packet, cannot get complete recovery.
   EXPECT_FALSE(IsRecoveryComplete());
 }
 
 // Verify that we don't use an old FEC packet for FEC decoding.
 TEST_F(RtpFecTest, FecRecoveryWithSeqNumGapTwoFrames) {
-  const int kNumImportantPackets = 0;
-  const bool kUseUnequalProtection = false;
-  uint8_t kProtectionFactor = 20;
+  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.
   // Second frame (new) with 3 media packets, and no FEC packets.
   //       ---Frame 1----                     ----Frame 2------
   //  #0(media) #1(media) #2(FEC)     #65535(media) #0(media) #1(media).
   // If we lose either packet 0 or 1 of second frame, FEC decoding should not
   // try to decode using "old" FEC packet #2.
 
   // Construct media packets for first frame, starting at sequence number 0.
   fec_seq_num_ = ConstructMediaPacketsSeqNum(2, 0);
 
   EXPECT_EQ(0, fec_->GenerateFec(media_packet_list_, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskBursty, &fec_packet_list_));
   // Expect 1 FEC packet.
-  EXPECT_EQ(1, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(1u, fec_packet_list_.size());
   // Add FEC packet (seq#2) of this first frame to received list (i.e., assume
   // the two media packet were lost).
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   ReceivedPackets(fec_packet_list_, fec_loss_mask_, true);
 
   // Construct media packets for second frame, with sequence number wrap.
   media_packet_list_.clear();
   fec_seq_num_ = ConstructMediaPacketsSeqNum(3, 65535);
 
   // Expect 3 media packets for this frame.
-  EXPECT_EQ(3, static_cast<int>(media_packet_list_.size()));
+  EXPECT_EQ(3u, media_packet_list_.size());
 
   // Second media packet lost (seq#0).
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   media_loss_mask_[1] = 1;
   // Add packets #65535, and #1 to received list.
   ReceivedPackets(media_packet_list_, media_loss_mask_, false);
 
   EXPECT_EQ(0,
             fec_->DecodeFec(&received_packet_list_, &recovered_packet_list_));
 
   // Expect that no decoding is done to get missing packet (seq#0) of second
   // frame, using old FEC packet (seq#2) from first (old) frame. So number of
   // recovered packets is 2, and not equal to number of media packets (=3).
-  EXPECT_EQ(2, static_cast<int>(recovered_packet_list_.size()));
+  EXPECT_EQ(2u, recovered_packet_list_.size());
   EXPECT_TRUE(recovered_packet_list_.size() != media_packet_list_.size());
 }
 
-// Verify we can still recovery frame if sequence number wrap occurs within
+// Verify we can still recover frame if sequence number wrap occurs within
 // the frame and FEC packet following wrap is received after media packets.
 TEST_F(RtpFecTest, FecRecoveryWithSeqNumGapOneFrameRecovery) {
-  const int kNumImportantPackets = 0;
-  const bool kUseUnequalProtection = false;
-  uint8_t kProtectionFactor = 20;
+  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).
   fec_seq_num_ = ConstructMediaPacketsSeqNum(3, 65534);
 
   EXPECT_EQ(0, fec_->GenerateFec(media_packet_list_, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskBursty, &fec_packet_list_));
 
   // Expect 1 FEC packet.
-  EXPECT_EQ(1, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(1u, fec_packet_list_.size());
 
   // Lose one media packet (seq# 65535).
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   media_loss_mask_[1] = 1;
   ReceivedPackets(media_packet_list_, media_loss_mask_, false);
   // Add FEC packet to received list following the media packets.
   ReceivedPackets(fec_packet_list_, fec_loss_mask_, true);
 
   EXPECT_EQ(0,
             fec_->DecodeFec(&received_packet_list_, &recovered_packet_list_));
 
   // Expect 3 media packets in recovered list, and complete recovery.
   // Wrap-around won't remove FEC packet, as it follows the wrap.
-  EXPECT_EQ(3, static_cast<int>(recovered_packet_list_.size()));
+  EXPECT_EQ(3u, recovered_packet_list_.size());
   EXPECT_TRUE(IsRecoveryComplete());
 }
 
 // Sequence number wrap occurs within the FEC packets for the frame.
 // In this case we will discard FEC packet and full recovery is not expected.
 // Same problem will occur if wrap is within media packets but FEC packet is
 // received before the media packets. This may be improved if timing information
 // is used to detect old FEC packets.
 // TODO(marpan): Update test if wrap-around handling changes in FEC decoding.
 TEST_F(RtpFecTest, FecRecoveryWithSeqNumGapOneFrameNoRecovery) {
-  const int kNumImportantPackets = 0;
-  const bool kUseUnequalProtection = false;
-  uint8_t kProtectionFactor = 200;
+  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).
   fec_seq_num_ = ConstructMediaPacketsSeqNum(3, 65532);
 
   EXPECT_EQ(0, fec_->GenerateFec(media_packet_list_, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskBursty, &fec_packet_list_));
 
   // Expect 2 FEC packets.
-  EXPECT_EQ(2, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(2u, fec_packet_list_.size());
 
   // Lose the last two media packets (seq# 65533, 65534).
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   media_loss_mask_[1] = 1;
   media_loss_mask_[2] = 1;
   ReceivedPackets(media_packet_list_, media_loss_mask_, false);
   ReceivedPackets(fec_packet_list_, fec_loss_mask_, true);
 
   EXPECT_EQ(0,
             fec_->DecodeFec(&received_packet_list_, &recovered_packet_list_));
 
   // The two FEC packets are received and should allow for complete recovery,
   // but because of the wrap the second FEC packet will be discarded, and only
   // one media packet is recoverable. So exepct 2 media packets on recovered
   // list and no complete recovery.
-  EXPECT_EQ(2, static_cast<int>(recovered_packet_list_.size()));
+  EXPECT_EQ(2u, recovered_packet_list_.size());
   EXPECT_TRUE(recovered_packet_list_.size() != media_packet_list_.size());
   EXPECT_FALSE(IsRecoveryComplete());
 }
 
-// Verify we can still recovery frame if FEC is received before media packets.
-TEST_F(RtpFecTest, FecRecoveryWithFecOutOfOrder) {
-  const int kNumImportantPackets = 0;
-  const bool kUseUnequalProtection = false;
-  uint8_t kProtectionFactor = 20;
+// Verify we can still recover frame if media packets are reordered.
+TEST_F(RtpFecTest, FecRecoveryWithMediaReordering) {
+  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).
+  fec_seq_num_ = ConstructMediaPacketsSeqNum(3, 0);
+
+  EXPECT_EQ(0, fec_->GenerateFec(media_packet_list_, kProtectionFactor,
+                                 kNumImportantPackets, kUseUnequalProtection,
+                                 webrtc::kFecMaskBursty, &fec_packet_list_));
+
+  // Expect 1 FEC packet.
+  EXPECT_EQ(1u, fec_packet_list_.size());
+
+  // Lose one media packet (seq# 1).
+  memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
+  memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
+  media_loss_mask_[1] = 1;
+  NetworkReceivedPackets();

[stefan-webrtc, 2016/07/05 17:26:49]

I think it would have been nicer to pass media_loss_mask into this method
instead.

[brandtr, 2016/07/07 14:59:12]

Done.

+
+  // Reorder received media packets.
+  auto it0 = received_packet_list_.begin();
+  auto it2 = received_packet_list_.begin();
+  it2++;
+  std::swap(*it0, *it2);
+
+  EXPECT_EQ(0,
+            fec_->DecodeFec(&received_packet_list_, &recovered_packet_list_));
+
+  // Expect 3 media packets in recovered list, and complete recovery.
+  EXPECT_EQ(3u, recovered_packet_list_.size());
+  EXPECT_TRUE(IsRecoveryComplete());
+}
+
+// Verify we can still recover frame if FEC is received before media packets.
+TEST_F(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).
   fec_seq_num_ = ConstructMediaPacketsSeqNum(3, 0);
 
   EXPECT_EQ(0, fec_->GenerateFec(media_packet_list_, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskBursty, &fec_packet_list_));
 
   // Expect 1 FEC packet.
-  EXPECT_EQ(1, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(1u, fec_packet_list_.size());
 
   // Lose one media packet (seq# 1).
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   media_loss_mask_[1] = 1;
   // Add FEC packet to received list before the media packets.
   ReceivedPackets(fec_packet_list_, fec_loss_mask_, true);
   // Add media packets to received list.
   ReceivedPackets(media_packet_list_, media_loss_mask_, false);
 
   EXPECT_EQ(0,
             fec_->DecodeFec(&received_packet_list_, &recovered_packet_list_));
 
   // Expect 3 media packets in recovered list, and complete recovery.
-  EXPECT_EQ(3, static_cast<int>(recovered_packet_list_.size()));
+  EXPECT_EQ(3u, recovered_packet_list_.size());
   EXPECT_TRUE(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.
 TEST_F(RtpFecTest, FecRecoveryWithLoss50percRandomMask) {
-  const int kNumImportantPackets = 0;
-  const bool kUseUnequalProtection = false;
-  const int kNumMediaPackets = 4;
-  const uint8_t kProtectionFactor = 255;
+  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
   //
 
   fec_seq_num_ = ConstructMediaPackets(kNumMediaPackets);
 
   EXPECT_EQ(0, fec_->GenerateFec(media_packet_list_, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskRandom, &fec_packet_list_));
 
   // Expect 4 FEC packets.
-  EXPECT_EQ(4, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(4u, fec_packet_list_.size());
 
   // 4 packets lost: 3 media packets (0, 2, 3), and one FEC packet (0) lost.
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   fec_loss_mask_[0] = 1;
   media_loss_mask_[0] = 1;
   media_loss_mask_[2] = 1;
   media_loss_mask_[3] = 1;
   NetworkReceivedPackets();
 
@@ skipping 17 matching lines @@
                                &recovered_packet_list_));
 
   // Cannot get complete recovery for this loss configuration with random mask.
   EXPECT_FALSE(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.
 TEST_F(RtpFecTest, FecRecoveryWithLoss50percBurstyMask) {
-  const int kNumImportantPackets = 0;
-  const bool kUseUnequalProtection = false;
-  const int kNumMediaPackets = 4;
-  const uint8_t kProtectionFactor = 255;
+  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
   //
 
   fec_seq_num_ = ConstructMediaPackets(kNumMediaPackets);
 
   EXPECT_EQ(0, fec_->GenerateFec(media_packet_list_, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskBursty, &fec_packet_list_));
 
   // Expect 4 FEC packets.
-  EXPECT_EQ(4, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(4u, fec_packet_list_.size());
 
   // 4 consecutive packets lost: media packets 0,1,2,3.
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   media_loss_mask_[0] = 1;
   media_loss_mask_[1] = 1;
   media_loss_mask_[2] = 1;
   media_loss_mask_[3] = 1;
   NetworkReceivedPackets();
 
@@ skipping 30 matching lines @@
   NetworkReceivedPackets();
 
   EXPECT_EQ(0, fec_->DecodeFec(&received_packet_list_,
                                &recovered_packet_list_));
 
   // Cannot get complete recovery for this loss configuration.
   EXPECT_FALSE(IsRecoveryComplete());
 }
 
 TEST_F(RtpFecTest, FecRecoveryNoLossUep) {
-  const int kNumImportantPackets = 2;
-  const bool kUseUnequalProtection = true;
-  const int kNumMediaPackets = 4;
-  const uint8_t kProtectionFactor = 60;
+  constexpr int kNumImportantPackets = 2;
+  constexpr bool kUseUnequalProtection = true;
+  constexpr int kNumMediaPackets = 4;
+  constexpr uint8_t kProtectionFactor = 60;
 
   fec_seq_num_ = ConstructMediaPackets(kNumMediaPackets);
 
   EXPECT_EQ(0, fec_->GenerateFec(media_packet_list_, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskBursty, &fec_packet_list_));
 
   // Expect 1 FEC packet.
-  EXPECT_EQ(1, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(1u, fec_packet_list_.size());
 
   // No packets lost.
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   NetworkReceivedPackets();
 
   EXPECT_EQ(0,
             fec_->DecodeFec(&received_packet_list_, &recovered_packet_list_));
 
   // No packets lost, expect complete recovery.
   EXPECT_TRUE(IsRecoveryComplete());
 }
 
 TEST_F(RtpFecTest, FecRecoveryWithLossUep) {
-  const int kNumImportantPackets = 2;
-  const bool kUseUnequalProtection = true;
-  const int kNumMediaPackets = 4;
-  const uint8_t kProtectionFactor = 60;
+  constexpr int kNumImportantPackets = 2;
+  constexpr bool kUseUnequalProtection = true;
+  constexpr int kNumMediaPackets = 4;
+  constexpr uint8_t kProtectionFactor = 60;
 
   fec_seq_num_ = ConstructMediaPackets(kNumMediaPackets);
 
   EXPECT_EQ(0, fec_->GenerateFec(media_packet_list_, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskBursty, &fec_packet_list_));
 
   // Expect 1 FEC packet.
-  EXPECT_EQ(1, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(1u, fec_packet_list_.size());
 
   // 1 media packet lost.
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   media_loss_mask_[3] = 1;
   NetworkReceivedPackets();
 
   EXPECT_EQ(0, fec_->DecodeFec(&received_packet_list_,
                                &recovered_packet_list_));
 
@@ skipping 10 matching lines @@
 
   EXPECT_EQ(0, fec_->DecodeFec(&received_packet_list_,
                                &recovered_packet_list_));
 
   // 2 packets lost, one FEC packet, cannot get complete recovery.
   EXPECT_FALSE(IsRecoveryComplete());
 }
 
 // Test 50% protection with random mask type for UEP on.
 TEST_F(RtpFecTest, FecRecoveryWithLoss50percUepRandomMask) {
-  const int kNumImportantPackets = 1;
-  const bool kUseUnequalProtection = true;
-  const int kNumMediaPackets = 4;
-  const uint8_t kProtectionFactor = 255;
+  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
   //
 
   fec_seq_num_ = ConstructMediaPackets(kNumMediaPackets);
 
   EXPECT_EQ(0, fec_->GenerateFec(media_packet_list_, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskRandom, &fec_packet_list_));
 
   // Expect 4 FEC packets.
-  EXPECT_EQ(4, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(4u, fec_packet_list_.size());
 
   // 4 packets lost: 3 media packets and FEC packet#1 lost.
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   fec_loss_mask_[1] = 1;
   media_loss_mask_[0] = 1;
   media_loss_mask_[2] = 1;
   media_loss_mask_[3] = 1;
   NetworkReceivedPackets();
 
@@ skipping 15 matching lines @@
   NetworkReceivedPackets();
 
   EXPECT_EQ(0, fec_->DecodeFec(&received_packet_list_,
                                &recovered_packet_list_));
 
   // Cannot get complete recovery for this loss configuration.
   EXPECT_FALSE(IsRecoveryComplete());
 }
 
 TEST_F(RtpFecTest, FecRecoveryNonConsecutivePackets) {
-  const int kNumImportantPackets = 0;
-  const bool kUseUnequalProtection = false;
-  const int kNumMediaPackets = 5;
-  uint8_t kProtectionFactor = 60;
+  constexpr int kNumImportantPackets = 0;
+  constexpr bool kUseUnequalProtection = false;
+  constexpr int kNumMediaPackets = 5;
+  constexpr uint8_t kProtectionFactor = 60;
 
   fec_seq_num_ = ConstructMediaPackets(kNumMediaPackets);
 
   // Create a new temporary packet list for generating FEC packets.
   // This list should have every other packet removed.
   PacketList protected_media_packets;
   DeepCopyEveryNthPacket(media_packet_list_, &protected_media_packets, 2);
 
   EXPECT_EQ(0, fec_->GenerateFec(protected_media_packets, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskBursty, &fec_packet_list_));
 
   // Expect 1 FEC packet.
-  EXPECT_EQ(1, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(1u, fec_packet_list_.size());
 
   // 1 protected media packet lost
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   media_loss_mask_[2] = 1;
   NetworkReceivedPackets();
 
   EXPECT_EQ(0, fec_->DecodeFec(&received_packet_list_,
                                &recovered_packet_list_));
 
@@ skipping 22 matching lines @@
   NetworkReceivedPackets();
 
   EXPECT_EQ(0, fec_->DecodeFec(&received_packet_list_,
                                &recovered_packet_list_));
 
   // 2 protected packets lost, one FEC packet, cannot get complete recovery.
   EXPECT_FALSE(IsRecoveryComplete());
 }
 
 TEST_F(RtpFecTest, FecRecoveryNonConsecutivePacketsExtension) {
-  const int kNumImportantPackets = 0;
-  const bool kUseUnequalProtection = false;
-  const int kNumMediaPackets = 21;
+  constexpr int kNumImportantPackets = 0;
+  constexpr bool kUseUnequalProtection = false;
+  constexpr int kNumMediaPackets = 21;
   uint8_t kProtectionFactor = 127;
 
   fec_seq_num_ = ConstructMediaPackets(kNumMediaPackets);
 
   // Create a new temporary packet list for generating FEC packets.
   // This list should have every other packet removed.
   PacketList protected_media_packets;
   DeepCopyEveryNthPacket(media_packet_list_, &protected_media_packets, 2);
 
   // 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, fec_->GenerateFec(protected_media_packets, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskBursty, &fec_packet_list_));
 
   // Expect 5 FEC packet.
-  EXPECT_EQ(5, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(5u, fec_packet_list_.size());
 
   // Last protected media packet lost
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   media_loss_mask_[kNumMediaPackets - 1] = 1;
   NetworkReceivedPackets();
 
   EXPECT_EQ(0, fec_->DecodeFec(&received_packet_list_,
                                &recovered_packet_list_));
 
@@ skipping 26 matching lines @@
   NetworkReceivedPackets();
 
   EXPECT_EQ(0, fec_->DecodeFec(&received_packet_list_,
                                &recovered_packet_list_));
 
   // 5 protected packets lost, one FEC packet, cannot get complete recovery.
   EXPECT_FALSE(IsRecoveryComplete());
 }
 
 TEST_F(RtpFecTest, FecRecoveryNonConsecutivePacketsWrap) {
-  const int kNumImportantPackets = 0;
-  const bool kUseUnequalProtection = false;
-  const int kNumMediaPackets = 21;
+  constexpr int kNumImportantPackets = 0;
+  constexpr bool kUseUnequalProtection = false;
+  constexpr int kNumMediaPackets = 21;
   uint8_t kProtectionFactor = 127;
 
   fec_seq_num_ = ConstructMediaPacketsSeqNum(kNumMediaPackets, 0xFFFF - 5);
 
   // Create a new temporary packet list for generating FEC packets.
   // This list should have every other packet removed.
   PacketList protected_media_packets;
   DeepCopyEveryNthPacket(media_packet_list_, &protected_media_packets, 2);
 
   // 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, fec_->GenerateFec(protected_media_packets, kProtectionFactor,
                                  kNumImportantPackets, kUseUnequalProtection,
                                  webrtc::kFecMaskBursty, &fec_packet_list_));
 
   // Expect 5 FEC packet.
-  EXPECT_EQ(5, static_cast<int>(fec_packet_list_.size()));
+  EXPECT_EQ(5u, fec_packet_list_.size());
 
   // Last protected media packet lost
   memset(media_loss_mask_, 0, sizeof(media_loss_mask_));
   memset(fec_loss_mask_, 0, sizeof(fec_loss_mask_));
   media_loss_mask_[kNumMediaPackets - 1] = 1;
   NetworkReceivedPackets();
 
   EXPECT_EQ(0, fec_->DecodeFec(&received_packet_list_,
                                &recovered_packet_list_));
 
@@ skipping 61 matching lines @@
                media_packet->length) != 0) {
       return false;
     }
     return true;
   };
   return std::equal(media_packet_list_.cbegin(), media_packet_list_.cend(),
                     recovered_packet_list_.cbegin(), cmp);
 }
 
 void RtpFecTest::NetworkReceivedPackets() {
-  const bool kFecPacket = true;
+  constexpr bool kFecPacket = true;
   ReceivedPackets(media_packet_list_, media_loss_mask_, !kFecPacket);
   ReceivedPackets(fec_packet_list_, fec_loss_mask_, kFecPacket);
 }
 
 template <typename T>
 void RtpFecTest::ReceivedPackets(const T& packet_list, int* loss_mask,
                                  bool is_fec) {
   int seq_num = fec_seq_num_;
   int packet_idx = 0;
 
@@ skipping 31 matching lines @@
 
 int RtpFecTest::ConstructMediaPacketsSeqNum(int num_media_packets,
                                             int start_seq_num) {
   RTC_DCHECK_GT(num_media_packets, 0);
   int sequence_number = start_seq_num;
   int time_stamp = random_.Rand<int>();
 
   for (int i = 0; i < num_media_packets; ++i) {
     std::unique_ptr<ForwardErrorCorrection::Packet> media_packet(
         new ForwardErrorCorrection::Packet());
-    const uint32_t kMinPacketSize = kRtpHeaderSize;
+    constexpr uint32_t kMinPacketSize = kRtpHeaderSize;
     const uint32_t kMaxPacketSize = IP_PACKET_SIZE - kRtpHeaderSize -
                                     kTransportOverhead -
                                     ForwardErrorCorrection::PacketOverhead();
     media_packet->length = random_.Rand(kMinPacketSize, kMaxPacketSize);
 
     // Generate random values for the first 2 bytes
     media_packet->data[0] = random_.Rand<uint8_t>();
     media_packet->data[1] = random_.Rand<uint8_t>();
 
     // The first two bits are assumed to be 10 by the FEC encoder.
@@ skipping 38 matching lines @@
                                         PacketList* dst, int N) {
   RTC_DCHECK_GT(N, 0);
   int i = 0;
   for (auto& packet : src) {
     if (i % N == 0) {
       dst->emplace_back(new ForwardErrorCorrection::Packet(*packet));
     }
     ++i;
   }
 }