Bugfix: FlexFEC causes retransmit bitrate increase.
When FlexFEC is enabled, sometimes media packet will be recovered by FEC before the actual media packet's arrival. In current implementation this will be considered as packet out of order and nack will be sent, thus cause large increase in retransmit bitrate.
This fix:
1. Avoid sending nack for packet out of order caused by "early" recovered media packets.
2. Save recovered media packet in a set, and do not send nack for these packets.
Bug: None
Change-Id: I008ef4e33668bce6d2cb9ff52b4b5c8e3f349965
Reviewed-on: https://webrtc-review.googlesource.com/c/108090
Commit-Queue: Ying Wang <yinwa@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25444}diff --git a/modules/video_coding/nack_module.cc b/modules/video_coding/nack_module.cc
index 7fbcf34..e3eeb84 100644
--- a/modules/video_coding/nack_module.cc
+++ b/modules/video_coding/nack_module.cc
@@ -56,6 +56,12 @@
}
int NackModule::OnReceivedPacket(uint16_t seq_num, bool is_keyframe) {
+ return OnReceivedPacket(seq_num, is_keyframe, false);
+}
+
+int NackModule::OnReceivedPacket(uint16_t seq_num,
+ bool is_keyframe,
+ bool is_recovered) {
rtc::CritScope lock(&crit_);
// TODO(philipel): When the packet includes information whether it is
// retransmitted or not, use that value instead. For
@@ -88,8 +94,6 @@
UpdateReorderingStatistics(seq_num);
return nacks_sent_for_packet;
}
- AddPacketsToNack(newest_seq_num_ + 1, seq_num);
- newest_seq_num_ = seq_num;
// Keep track of new keyframes.
if (is_keyframe)
@@ -100,6 +104,21 @@
if (it != keyframe_list_.begin())
keyframe_list_.erase(keyframe_list_.begin(), it);
+ if (is_recovered) {
+ recovered_list_.insert(seq_num);
+
+ // Remove old ones so we don't accumulate recovered packets.
+ auto it = recovered_list_.lower_bound(seq_num - kMaxPacketAge);
+ if (it != recovered_list_.begin())
+ recovered_list_.erase(recovered_list_.begin(), it);
+
+ // Do not send nack for packets recovered by FEC or RTX.
+ return 0;
+ }
+
+ AddPacketsToNack(newest_seq_num_ + 1, seq_num);
+ newest_seq_num_ = seq_num;
+
// Are there any nacks that are waiting for this seq_num.
std::vector<uint16_t> nack_batch = GetNackBatch(kSeqNumOnly);
if (!nack_batch.empty())
@@ -113,6 +132,8 @@
nack_list_.erase(nack_list_.begin(), nack_list_.lower_bound(seq_num));
keyframe_list_.erase(keyframe_list_.begin(),
keyframe_list_.lower_bound(seq_num));
+ recovered_list_.erase(recovered_list_.begin(),
+ recovered_list_.lower_bound(seq_num));
}
void NackModule::UpdateRtt(int64_t rtt_ms) {
@@ -124,6 +145,7 @@
rtc::CritScope lock(&crit_);
nack_list_.clear();
keyframe_list_.clear();
+ recovered_list_.clear();
}
int64_t NackModule::TimeUntilNextProcess() {
@@ -200,6 +222,9 @@
}
for (uint16_t seq_num = seq_num_start; seq_num != seq_num_end; ++seq_num) {
+ // Do not send nack for packets that are already recovered by FEC or RTX
+ if (recovered_list_.find(seq_num) != recovered_list_.end())
+ continue;
NackInfo nack_info(seq_num, seq_num + WaitNumberOfPackets(0.5));
RTC_DCHECK(nack_list_.find(seq_num) == nack_list_.end());
nack_list_[seq_num] = nack_info;
diff --git a/modules/video_coding/nack_module.h b/modules/video_coding/nack_module.h
index 44340e9..1720df9 100644
--- a/modules/video_coding/nack_module.h
+++ b/modules/video_coding/nack_module.h
@@ -32,6 +32,8 @@
KeyFrameRequestSender* keyframe_request_sender);
int OnReceivedPacket(uint16_t seq_num, bool is_keyframe);
+ int OnReceivedPacket(uint16_t seq_num, bool is_keyframe, bool is_recovered);
+
void ClearUpTo(uint16_t seq_num);
void UpdateRtt(int64_t rtt_ms);
void Clear();
@@ -87,6 +89,8 @@
RTC_GUARDED_BY(crit_);
std::set<uint16_t, DescendingSeqNumComp<uint16_t>> keyframe_list_
RTC_GUARDED_BY(crit_);
+ std::set<uint16_t, DescendingSeqNumComp<uint16_t>> recovered_list_
+ RTC_GUARDED_BY(crit_);
video_coding::Histogram reordering_histogram_ RTC_GUARDED_BY(crit_);
bool initialized_ RTC_GUARDED_BY(crit_);
int64_t rtt_ms_ RTC_GUARDED_BY(crit_);
diff --git a/modules/video_coding/nack_module_unittest.cc b/modules/video_coding/nack_module_unittest.cc
index 8a5f46b..208a6f3 100644
--- a/modules/video_coding/nack_module_unittest.cc
+++ b/modules/video_coding/nack_module_unittest.cc
@@ -40,38 +40,38 @@
};
TEST_F(TestNackModule, NackOnePacket) {
- nack_module_.OnReceivedPacket(1, false);
- nack_module_.OnReceivedPacket(3, false);
+ nack_module_.OnReceivedPacket(1, false, false);
+ nack_module_.OnReceivedPacket(3, false, false);
EXPECT_EQ(1u, sent_nacks_.size());
EXPECT_EQ(2, sent_nacks_[0]);
}
TEST_F(TestNackModule, WrappingSeqNum) {
- nack_module_.OnReceivedPacket(0xfffe, false);
- nack_module_.OnReceivedPacket(1, false);
+ nack_module_.OnReceivedPacket(0xfffe, false, false);
+ nack_module_.OnReceivedPacket(1, false, false);
EXPECT_EQ(2u, sent_nacks_.size());
EXPECT_EQ(0xffff, sent_nacks_[0]);
EXPECT_EQ(0, sent_nacks_[1]);
}
TEST_F(TestNackModule, WrappingSeqNumClearToKeyframe) {
- nack_module_.OnReceivedPacket(0xfffe, false);
- nack_module_.OnReceivedPacket(1, false);
+ nack_module_.OnReceivedPacket(0xfffe, false, false);
+ nack_module_.OnReceivedPacket(1, false, false);
EXPECT_EQ(2u, sent_nacks_.size());
EXPECT_EQ(0xffff, sent_nacks_[0]);
EXPECT_EQ(0, sent_nacks_[1]);
sent_nacks_.clear();
- nack_module_.OnReceivedPacket(2, true);
+ nack_module_.OnReceivedPacket(2, true, false);
EXPECT_EQ(0u, sent_nacks_.size());
- nack_module_.OnReceivedPacket(501, true);
+ nack_module_.OnReceivedPacket(501, true, false);
EXPECT_EQ(498u, sent_nacks_.size());
for (int seq_num = 3; seq_num < 501; ++seq_num)
EXPECT_EQ(seq_num, sent_nacks_[seq_num - 3]);
sent_nacks_.clear();
- nack_module_.OnReceivedPacket(1001, false);
+ nack_module_.OnReceivedPacket(1001, false, false);
EXPECT_EQ(499u, sent_nacks_.size());
for (int seq_num = 502; seq_num < 1001; ++seq_num)
EXPECT_EQ(seq_num, sent_nacks_[seq_num - 502]);
@@ -91,7 +91,7 @@
// It will then clear all nacks up to the next keyframe (seq num 2),
// thus removing 0xffff and 0 from the nack list.
sent_nacks_.clear();
- nack_module_.OnReceivedPacket(1004, false);
+ nack_module_.OnReceivedPacket(1004, false, false);
EXPECT_EQ(2u, sent_nacks_.size());
EXPECT_EQ(1002, sent_nacks_[0]);
EXPECT_EQ(1003, sent_nacks_[1]);
@@ -107,7 +107,7 @@
// Adding packet 1007 will cause the nack module to overflow again, thus
// clearing everything up to 501 which is the next keyframe.
- nack_module_.OnReceivedPacket(1007, false);
+ nack_module_.OnReceivedPacket(1007, false, false);
sent_nacks_.clear();
clock_->AdvanceTimeMilliseconds(100);
nack_module_.Process();
@@ -146,8 +146,8 @@
}
TEST_F(TestNackModule, ResendNack) {
- nack_module_.OnReceivedPacket(1, false);
- nack_module_.OnReceivedPacket(3, false);
+ nack_module_.OnReceivedPacket(1, false, false);
+ nack_module_.OnReceivedPacket(3, false, false);
EXPECT_EQ(1u, sent_nacks_.size());
EXPECT_EQ(2, sent_nacks_[0]);
@@ -169,15 +169,15 @@
nack_module_.Process();
EXPECT_EQ(4u, sent_nacks_.size());
- nack_module_.OnReceivedPacket(2, false);
+ nack_module_.OnReceivedPacket(2, false, false);
clock_->AdvanceTimeMilliseconds(50);
nack_module_.Process();
EXPECT_EQ(4u, sent_nacks_.size());
}
TEST_F(TestNackModule, ResendPacketMaxRetries) {
- nack_module_.OnReceivedPacket(1, false);
- nack_module_.OnReceivedPacket(3, false);
+ nack_module_.OnReceivedPacket(1, false, false);
+ nack_module_.OnReceivedPacket(3, false, false);
EXPECT_EQ(1u, sent_nacks_.size());
EXPECT_EQ(2, sent_nacks_[0]);
@@ -193,35 +193,35 @@
}
TEST_F(TestNackModule, TooLargeNackList) {
- nack_module_.OnReceivedPacket(0, false);
- nack_module_.OnReceivedPacket(1001, false);
+ nack_module_.OnReceivedPacket(0, false, false);
+ nack_module_.OnReceivedPacket(1001, false, false);
EXPECT_EQ(1000u, sent_nacks_.size());
EXPECT_EQ(0, keyframes_requested_);
- nack_module_.OnReceivedPacket(1003, false);
+ nack_module_.OnReceivedPacket(1003, false, false);
EXPECT_EQ(1000u, sent_nacks_.size());
EXPECT_EQ(1, keyframes_requested_);
- nack_module_.OnReceivedPacket(1004, false);
+ nack_module_.OnReceivedPacket(1004, false, false);
EXPECT_EQ(1000u, sent_nacks_.size());
EXPECT_EQ(1, keyframes_requested_);
}
TEST_F(TestNackModule, TooLargeNackListWithKeyFrame) {
- nack_module_.OnReceivedPacket(0, false);
- nack_module_.OnReceivedPacket(1, true);
- nack_module_.OnReceivedPacket(1001, false);
+ nack_module_.OnReceivedPacket(0, false, false);
+ nack_module_.OnReceivedPacket(1, true, false);
+ nack_module_.OnReceivedPacket(1001, false, false);
EXPECT_EQ(999u, sent_nacks_.size());
EXPECT_EQ(0, keyframes_requested_);
- nack_module_.OnReceivedPacket(1003, false);
+ nack_module_.OnReceivedPacket(1003, false, false);
EXPECT_EQ(1000u, sent_nacks_.size());
EXPECT_EQ(0, keyframes_requested_);
- nack_module_.OnReceivedPacket(1005, false);
+ nack_module_.OnReceivedPacket(1005, false, false);
EXPECT_EQ(1000u, sent_nacks_.size());
EXPECT_EQ(1, keyframes_requested_);
}
TEST_F(TestNackModule, ClearUpTo) {
- nack_module_.OnReceivedPacket(0, false);
- nack_module_.OnReceivedPacket(100, false);
+ nack_module_.OnReceivedPacket(0, false, false);
+ nack_module_.OnReceivedPacket(100, false, false);
EXPECT_EQ(99u, sent_nacks_.size());
sent_nacks_.clear();
@@ -233,8 +233,8 @@
}
TEST_F(TestNackModule, ClearUpToWrap) {
- nack_module_.OnReceivedPacket(0xfff0, false);
- nack_module_.OnReceivedPacket(0xf, false);
+ nack_module_.OnReceivedPacket(0xfff0, false, false);
+ nack_module_.OnReceivedPacket(0xf, false, false);
EXPECT_EQ(30u, sent_nacks_.size());
sent_nacks_.clear();
@@ -246,20 +246,20 @@
}
TEST_F(TestNackModule, PacketNackCount) {
- EXPECT_EQ(0, nack_module_.OnReceivedPacket(0, false));
- EXPECT_EQ(0, nack_module_.OnReceivedPacket(2, false));
- EXPECT_EQ(1, nack_module_.OnReceivedPacket(1, false));
+ EXPECT_EQ(0, nack_module_.OnReceivedPacket(0, false, false));
+ EXPECT_EQ(0, nack_module_.OnReceivedPacket(2, false, false));
+ EXPECT_EQ(1, nack_module_.OnReceivedPacket(1, false, false));
sent_nacks_.clear();
nack_module_.UpdateRtt(100);
- EXPECT_EQ(0, nack_module_.OnReceivedPacket(5, false));
+ EXPECT_EQ(0, nack_module_.OnReceivedPacket(5, false, false));
clock_->AdvanceTimeMilliseconds(100);
nack_module_.Process();
clock_->AdvanceTimeMilliseconds(100);
nack_module_.Process();
- EXPECT_EQ(3, nack_module_.OnReceivedPacket(3, false));
- EXPECT_EQ(3, nack_module_.OnReceivedPacket(4, false));
- EXPECT_EQ(0, nack_module_.OnReceivedPacket(4, false));
+ EXPECT_EQ(3, nack_module_.OnReceivedPacket(3, false, false));
+ EXPECT_EQ(3, nack_module_.OnReceivedPacket(4, false, false));
+ EXPECT_EQ(0, nack_module_.OnReceivedPacket(4, false, false));
}
TEST_F(TestNackModule, NackListFullAndNoOverlapWithKeyframes) {
@@ -267,14 +267,22 @@
const unsigned int kFirstGap = kMaxNackPackets - 20;
const unsigned int kSecondGap = 200;
uint16_t seq_num = 0;
- nack_module_.OnReceivedPacket(seq_num++, true);
+ nack_module_.OnReceivedPacket(seq_num++, true, false);
seq_num += kFirstGap;
- nack_module_.OnReceivedPacket(seq_num++, true);
+ nack_module_.OnReceivedPacket(seq_num++, true, false);
EXPECT_EQ(kFirstGap, sent_nacks_.size());
sent_nacks_.clear();
seq_num += kSecondGap;
- nack_module_.OnReceivedPacket(seq_num, true);
+ nack_module_.OnReceivedPacket(seq_num, true, false);
EXPECT_EQ(kSecondGap, sent_nacks_.size());
}
+TEST_F(TestNackModule, HandleFecRecoveredPacket) {
+ nack_module_.OnReceivedPacket(1, false, false);
+ nack_module_.OnReceivedPacket(4, false, true);
+ EXPECT_EQ(0u, sent_nacks_.size());
+ nack_module_.OnReceivedPacket(5, false, false);
+ EXPECT_EQ(2u, sent_nacks_.size());
+}
+
} // namespace webrtc