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/*
* 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/rtp_rtcp/source/receive_statistics_impl.h"
#include <cmath>
#include <cstdlib>
#include <memory>
#include <utility>
#include <vector>
#include "api/units/time_delta.h"
#include "modules/remote_bitrate_estimator/test/bwe_test_logging.h"
#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
#include "modules/rtp_rtcp/source/rtcp_packet/report_block.h"
#include "modules/rtp_rtcp/source/rtp_packet_received.h"
#include "modules/rtp_rtcp/source/rtp_rtcp_config.h"
#include "rtc_base/logging.h"
#include "rtc_base/time_utils.h"
#include "system_wrappers/include/clock.h"
namespace webrtc {
namespace {
constexpr TimeDelta kStatisticsTimeout = TimeDelta::Seconds(8);
constexpr TimeDelta kStatisticsProcessInterval = TimeDelta::Seconds(1);
TimeDelta UnixEpochDelta(Clock& clock) {
Timestamp now = clock.CurrentTime();
NtpTime ntp_now = clock.ConvertTimestampToNtpTime(now);
return TimeDelta::Millis(ntp_now.ToMs() - now.ms() -
rtc::kNtpJan1970Millisecs);
}
} // namespace
StreamStatistician::~StreamStatistician() {}
StreamStatisticianImpl::StreamStatisticianImpl(uint32_t ssrc,
Clock* clock,
int max_reordering_threshold)
: ssrc_(ssrc),
clock_(clock),
delta_internal_unix_epoch_(UnixEpochDelta(*clock_)),
incoming_bitrate_(/*max_window_size=*/kStatisticsProcessInterval),
max_reordering_threshold_(max_reordering_threshold),
enable_retransmit_detection_(false),
cumulative_loss_is_capped_(false),
jitter_q4_(0),
cumulative_loss_(0),
cumulative_loss_rtcp_offset_(0),
last_received_timestamp_(0),
received_seq_first_(-1),
received_seq_max_(-1),
last_report_cumulative_loss_(0),
last_report_seq_max_(-1),
last_payload_type_frequency_(0) {}
StreamStatisticianImpl::~StreamStatisticianImpl() = default;
bool StreamStatisticianImpl::UpdateOutOfOrder(const RtpPacketReceived& packet,
int64_t sequence_number,
Timestamp now) {
// Check if `packet` is second packet of a stream restart.
if (received_seq_out_of_order_) {
// Count the previous packet as a received; it was postponed below.
--cumulative_loss_;
uint16_t expected_sequence_number = *received_seq_out_of_order_ + 1;
received_seq_out_of_order_ = absl::nullopt;
if (packet.SequenceNumber() == expected_sequence_number) {
// Ignore sequence number gap caused by stream restart for packet loss
// calculation, by setting received_seq_max_ to the sequence number just
// before the out-of-order seqno. This gives a net zero change of
// `cumulative_loss_`, for the two packets interpreted as a stream reset.
//
// Fraction loss for the next report may get a bit off, since we don't
// update last_report_seq_max_ and last_report_cumulative_loss_ in a
// consistent way.
last_report_seq_max_ = sequence_number - 2;
received_seq_max_ = sequence_number - 2;
return false;
}
}
if (std::abs(sequence_number - received_seq_max_) >
max_reordering_threshold_) {
// Sequence number gap looks too large, wait until next packet to check
// for a stream restart.
received_seq_out_of_order_ = packet.SequenceNumber();
// Postpone counting this as a received packet until we know how to update
// `received_seq_max_`, otherwise we temporarily decrement
// `cumulative_loss_`. The
// ReceiveStatisticsTest.StreamRestartDoesntCountAsLoss test expects
// `cumulative_loss_` to be unchanged by the reception of the first packet
// after stream reset.
++cumulative_loss_;
return true;
}
if (sequence_number > received_seq_max_)
return false;
// Old out of order packet, may be retransmit.
if (enable_retransmit_detection_ && IsRetransmitOfOldPacket(packet, now))
receive_counters_.retransmitted.AddPacket(packet);
return true;
}
void StreamStatisticianImpl::UpdateCounters(const RtpPacketReceived& packet) {
RTC_DCHECK_EQ(ssrc_, packet.Ssrc());
Timestamp now = clock_->CurrentTime();
incoming_bitrate_.Update(packet.size(), now);
receive_counters_.transmitted.AddPacket(packet);
--cumulative_loss_;
// Use PeekUnwrap and later update the state to avoid updating the state for
// out of order packets.
int64_t sequence_number = seq_unwrapper_.PeekUnwrap(packet.SequenceNumber());
if (!ReceivedRtpPacket()) {
received_seq_first_ = sequence_number;
last_report_seq_max_ = sequence_number - 1;
received_seq_max_ = sequence_number - 1;
receive_counters_.first_packet_time = now;
} else if (UpdateOutOfOrder(packet, sequence_number, now)) {
return;
}
// In order packet.
cumulative_loss_ += sequence_number - received_seq_max_;
received_seq_max_ = sequence_number;
// Update the internal state of `seq_unwrapper_`.
seq_unwrapper_.Unwrap(packet.SequenceNumber());
// If new time stamp and more than one in-order packet received, calculate
// new jitter statistics.
if (packet.Timestamp() != last_received_timestamp_ &&
(receive_counters_.transmitted.packets -
receive_counters_.retransmitted.packets) > 1) {
UpdateJitter(packet, now);
}
last_received_timestamp_ = packet.Timestamp();
last_receive_time_ = now;
}
void StreamStatisticianImpl::UpdateJitter(const RtpPacketReceived& packet,
Timestamp receive_time) {
RTC_DCHECK(last_receive_time_.has_value());
TimeDelta receive_diff = receive_time - *last_receive_time_;
RTC_DCHECK_GE(receive_diff, TimeDelta::Zero());
uint32_t receive_diff_rtp =
(receive_diff * packet.payload_type_frequency()).seconds<uint32_t>();
int32_t time_diff_samples =
receive_diff_rtp - (packet.Timestamp() - last_received_timestamp_);
ReviseFrequencyAndJitter(packet.payload_type_frequency());
// lib_jingle sometimes deliver crazy jumps in TS for the same stream.
// If this happens, don't update jitter value. Use 5 secs video frequency
// as the threshold.
if (time_diff_samples < 5 * kVideoPayloadTypeFrequency &&
time_diff_samples > -5 * kVideoPayloadTypeFrequency) {
// Note we calculate in Q4 to avoid using float.
int32_t jitter_diff_q4 = (std::abs(time_diff_samples) << 4) - jitter_q4_;
jitter_q4_ += ((jitter_diff_q4 + 8) >> 4);
}
}
void StreamStatisticianImpl::ReviseFrequencyAndJitter(
int payload_type_frequency) {
if (payload_type_frequency == last_payload_type_frequency_) {
return;
}
if (payload_type_frequency != 0) {
if (last_payload_type_frequency_ != 0) {
// Value in "jitter_q4_" variable is a number of samples.
// I.e. jitter = timestamp (s) * frequency (Hz).
// Since the frequency has changed we have to update the number of samples
// accordingly. The new value should rely on a new frequency.
// If we don't do such procedure we end up with the number of samples that
// cannot be converted into TimeDelta correctly
// (i.e. jitter = jitter_q4_ >> 4 / payload_type_frequency).
// In such case, the number of samples has a "mix".
// Doing so we pretend that everything prior and including the current
// packet were computed on packet's frequency.
jitter_q4_ = static_cast<int>(static_cast<uint64_t>(jitter_q4_) *
payload_type_frequency /
last_payload_type_frequency_);
}
// If last_payload_type_frequency_ is not present, the jitter_q4_
// variable has its initial value.
// Keep last_payload_type_frequency_ up to date and non-zero (set).
last_payload_type_frequency_ = payload_type_frequency;
}
}
void StreamStatisticianImpl::SetMaxReorderingThreshold(
int max_reordering_threshold) {
max_reordering_threshold_ = max_reordering_threshold;
}
void StreamStatisticianImpl::EnableRetransmitDetection(bool enable) {
enable_retransmit_detection_ = enable;
}
RtpReceiveStats StreamStatisticianImpl::GetStats() const {
RtpReceiveStats stats;
stats.packets_lost = cumulative_loss_;
// Note: internal jitter value is in Q4 and needs to be scaled by 1/16.
stats.jitter = jitter_q4_ >> 4;
if (last_payload_type_frequency_ > 0) {
// Divide value in fractional seconds by frequency to get jitter in
// fractional seconds.
stats.interarrival_jitter =
TimeDelta::Seconds(stats.jitter) / last_payload_type_frequency_;
}
if (last_receive_time_.has_value()) {
stats.last_packet_received =
*last_receive_time_ + delta_internal_unix_epoch_;
}
stats.packet_counter = receive_counters_.transmitted;
return stats;
}
void StreamStatisticianImpl::MaybeAppendReportBlockAndReset(
std::vector<rtcp::ReportBlock>& report_blocks) {
if (!ReceivedRtpPacket()) {
return;
}
Timestamp now = clock_->CurrentTime();
if (now - *last_receive_time_ >= kStatisticsTimeout) {
// Not active.
return;
}
report_blocks.emplace_back();
rtcp::ReportBlock& stats = report_blocks.back();
stats.SetMediaSsrc(ssrc_);
// Calculate fraction lost.
int64_t exp_since_last = received_seq_max_ - last_report_seq_max_;
RTC_DCHECK_GE(exp_since_last, 0);
int32_t lost_since_last = cumulative_loss_ - last_report_cumulative_loss_;
if (exp_since_last > 0 && lost_since_last > 0) {
// Scale 0 to 255, where 255 is 100% loss.
stats.SetFractionLost(255 * lost_since_last / exp_since_last);
}
int packets_lost = cumulative_loss_ + cumulative_loss_rtcp_offset_;
if (packets_lost < 0) {
// Clamp to zero. Work around to accommodate for senders that misbehave with
// negative cumulative loss.
packets_lost = 0;
cumulative_loss_rtcp_offset_ = -cumulative_loss_;
}
if (packets_lost > 0x7fffff) {
// Packets lost is a 24 bit signed field, and thus should be clamped, as
// described in https://datatracker.ietf.org/doc/html/rfc3550#appendix-A.3
if (!cumulative_loss_is_capped_) {
cumulative_loss_is_capped_ = true;
RTC_LOG(LS_WARNING) << "Cumulative loss reached maximum value for ssrc "
<< ssrc_;
}
packets_lost = 0x7fffff;
}
stats.SetCumulativeLost(packets_lost);
stats.SetExtHighestSeqNum(received_seq_max_);
// Note: internal jitter value is in Q4 and needs to be scaled by 1/16.
stats.SetJitter(jitter_q4_ >> 4);
// Only for report blocks in RTCP SR and RR.
last_report_cumulative_loss_ = cumulative_loss_;
last_report_seq_max_ = received_seq_max_;
BWE_TEST_LOGGING_PLOT_WITH_SSRC(1, "cumulative_loss_pkts", now.ms(),
cumulative_loss_, ssrc_);
BWE_TEST_LOGGING_PLOT_WITH_SSRC(1, "received_seq_max_pkts", now.ms(),
(received_seq_max_ - received_seq_first_),
ssrc_);
}
absl::optional<int> StreamStatisticianImpl::GetFractionLostInPercent() const {
if (!ReceivedRtpPacket()) {
return absl::nullopt;
}
int64_t expected_packets = 1 + received_seq_max_ - received_seq_first_;
if (expected_packets <= 0) {
return absl::nullopt;
}
if (cumulative_loss_ <= 0) {
return 0;
}
return 100 * static_cast<int64_t>(cumulative_loss_) / expected_packets;
}
StreamDataCounters StreamStatisticianImpl::GetReceiveStreamDataCounters()
const {
return receive_counters_;
}
uint32_t StreamStatisticianImpl::BitrateReceived() const {
return incoming_bitrate_.Rate(clock_->CurrentTime())
.value_or(DataRate::Zero())
.bps<uint32_t>();
}
bool StreamStatisticianImpl::IsRetransmitOfOldPacket(
const RtpPacketReceived& packet,
Timestamp now) const {
int frequency_hz = packet.payload_type_frequency();
RTC_DCHECK(last_receive_time_.has_value());
RTC_CHECK_GT(frequency_hz, 0);
TimeDelta time_diff = now - *last_receive_time_;
// Diff in time stamp since last received in order.
uint32_t timestamp_diff = packet.Timestamp() - last_received_timestamp_;
TimeDelta rtp_time_stamp_diff =
TimeDelta::Seconds(timestamp_diff) / frequency_hz;
// Jitter standard deviation in samples.
float jitter_std = std::sqrt(static_cast<float>(jitter_q4_ >> 4));
// 2 times the standard deviation => 95% confidence.
// Min max_delay is 1ms.
TimeDelta max_delay = std::max(
TimeDelta::Seconds(2 * jitter_std / frequency_hz), TimeDelta::Millis(1));
return time_diff > rtp_time_stamp_diff + max_delay;
}
std::unique_ptr<ReceiveStatistics> ReceiveStatistics::Create(Clock* clock) {
return std::make_unique<ReceiveStatisticsLocked>(
clock, [](uint32_t ssrc, Clock* clock, int max_reordering_threshold) {
return std::make_unique<StreamStatisticianLocked>(
ssrc, clock, max_reordering_threshold);
});
}
std::unique_ptr<ReceiveStatistics> ReceiveStatistics::CreateThreadCompatible(
Clock* clock) {
return std::make_unique<ReceiveStatisticsImpl>(
clock, [](uint32_t ssrc, Clock* clock, int max_reordering_threshold) {
return std::make_unique<StreamStatisticianImpl>(
ssrc, clock, max_reordering_threshold);
});
}
ReceiveStatisticsImpl::ReceiveStatisticsImpl(
Clock* clock,
std::function<std::unique_ptr<StreamStatisticianImplInterface>(
uint32_t ssrc,
Clock* clock,
int max_reordering_threshold)> stream_statistician_factory)
: clock_(clock),
stream_statistician_factory_(std::move(stream_statistician_factory)),
last_returned_ssrc_idx_(0),
max_reordering_threshold_(kDefaultMaxReorderingThreshold) {}
void ReceiveStatisticsImpl::OnRtpPacket(const RtpPacketReceived& packet) {
// StreamStatisticianImpl instance is created once and only destroyed when
// this whole ReceiveStatisticsImpl is destroyed. StreamStatisticianImpl has
// it's own locking so don't hold receive_statistics_lock_ (potential
// deadlock).
GetOrCreateStatistician(packet.Ssrc())->UpdateCounters(packet);
}
StreamStatistician* ReceiveStatisticsImpl::GetStatistician(
uint32_t ssrc) const {
const auto& it = statisticians_.find(ssrc);
if (it == statisticians_.end())
return nullptr;
return it->second.get();
}
StreamStatisticianImplInterface* ReceiveStatisticsImpl::GetOrCreateStatistician(
uint32_t ssrc) {
std::unique_ptr<StreamStatisticianImplInterface>& impl = statisticians_[ssrc];
if (impl == nullptr) { // new element
impl =
stream_statistician_factory_(ssrc, clock_, max_reordering_threshold_);
all_ssrcs_.push_back(ssrc);
}
return impl.get();
}
void ReceiveStatisticsImpl::SetMaxReorderingThreshold(
int max_reordering_threshold) {
max_reordering_threshold_ = max_reordering_threshold;
for (auto& statistician : statisticians_) {
statistician.second->SetMaxReorderingThreshold(max_reordering_threshold);
}
}
void ReceiveStatisticsImpl::SetMaxReorderingThreshold(
uint32_t ssrc,
int max_reordering_threshold) {
GetOrCreateStatistician(ssrc)->SetMaxReorderingThreshold(
max_reordering_threshold);
}
void ReceiveStatisticsImpl::EnableRetransmitDetection(uint32_t ssrc,
bool enable) {
GetOrCreateStatistician(ssrc)->EnableRetransmitDetection(enable);
}
std::vector<rtcp::ReportBlock> ReceiveStatisticsImpl::RtcpReportBlocks(
size_t max_blocks) {
std::vector<rtcp::ReportBlock> result;
result.reserve(std::min(max_blocks, all_ssrcs_.size()));
size_t ssrc_idx = 0;
for (size_t i = 0; i < all_ssrcs_.size() && result.size() < max_blocks; ++i) {
ssrc_idx = (last_returned_ssrc_idx_ + i + 1) % all_ssrcs_.size();
const uint32_t media_ssrc = all_ssrcs_[ssrc_idx];
auto statistician_it = statisticians_.find(media_ssrc);
RTC_DCHECK(statistician_it != statisticians_.end());
statistician_it->second->MaybeAppendReportBlockAndReset(result);
}
last_returned_ssrc_idx_ = ssrc_idx;
return result;
}
} // namespace webrtc
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